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Sample records for unconfined compressive strength

  1. The Effect of Polymer-Cement Stabilization on the Unconfined Compressive Strength of Liquefiable Soils

    Directory of Open Access Journals (Sweden)

    Ali Ateş

    2013-01-01

    Full Text Available Soil stabilization has been widely used as an alternative to substitute the lack of suitable material on site. The use of nontraditional chemical stabilizers in soil improvement is growing daily. In this study a laboratory experiment was conducted to evaluate the effects of waterborne polymer on unconfined compression strength and to study the effect of cement grout on pre-venting of liquefiable sandy soils. The laboratory tests were performed including grain size of sandy soil, unit weight, ultrasonic pulse velocity, and unconfined compressive strength test. The sand and various amounts of polymer (1%, 2%, 3%, and 4% and cement (10%, 20%, 30%, and 40% were mixed with all of them into dough using mechanical kneader in laboratory conditions. Grouting experiment is performed with a cylindrical mould of  mm. The samples were subjected to unconfined compression tests to determine their strength after 7 and 14 days of curing. The results of the tests indicated that the waterborne polymer significantly improved the unconfined compression strength of sandy soils which have susceptibility of liquefaction.

  2. Influence of variables on the consolidation and unconfined compressive strength of crushed salt: Technical report

    International Nuclear Information System (INIS)

    Eight hydrostatic compression creep tests were performed on crushed salt specimens fabricated from Avery Island dome salt. Following the creep test, each specimen was tested in unconfined compression. The experiments were performed to assess the influence of the following four variables on the consolidation and unconfined strength of crushed salt: grain size distribution, temperature, time, and moisture content. The experiment design comprised a half-fraction factorial matrix at two levels. The levels of each variable investigated were grain size distribution, uniform-graded and well-graded (coefficient of uniformity of 1 and 8); temperature 250C and 1000C; time, 3.5 x 103s and 950 x 103s (approximately 60 minutes and 11 days, respectively); and moisture content, dry and wet (85% relative humidity for 24 hours). The hydrostatic creep stress was 10 MPa. The unconfined compression tests were performed at an axial strain rate of 1 x 10-5s-1. Results show that the variables time and moisture content have the greatest influence on creep consolidation, while grain size distribution and, to a somewhat lesser degree, temperature have the greatest influence on total consolidation. Time and moisture content and the confounded two-factor interactions between either grain size distribution and time or temperature and moisture content have the greatest influence on unconfined strength. 7 refs., 7 figs., 11 tabs

  3. Influence of variables on the consolidation and unconfined compressive strength of crushed salt: Technical report

    Energy Technology Data Exchange (ETDEWEB)

    Pfeifle, T.W.; Senseny, P.E.; Mellegard, K.D.

    1987-01-01

    Eight hydrostatic compression creep tests were performed on crushed salt specimens fabricated from Avery Island dome salt. Following the creep test, each specimen was tested in unconfined compression. The experiments were performed to assess the influence of the following four variables on the consolidation and unconfined strength of crushed salt: grain size distribution, temperature, time, and moisture content. The experiment design comprised a half-fraction factorial matrix at two levels. The levels of each variable investigated were grain size distribution, uniform-graded and well-graded (coefficient of uniformity of 1 and 8); temperature 25/sup 0/C and 100/sup 0/C; time, 3.5 x 10/sup 3/s and 950 x 10/sup 3/s (approximately 60 minutes and 11 days, respectively); and moisture content, dry and wet (85% relative humidity for 24 hours). The hydrostatic creep stress was 10 MPa. The unconfined compression tests were performed at an axial strain rate of 1 x 10/sup -5/s/sup -1/. Results show that the variables time and moisture content have the greatest influence on creep consolidation, while grain size distribution and, to a somewhat lesser degree, temperature have the greatest influence on total consolidation. Time and moisture content and the confounded two-factor interactions between either grain size distribution and time or temperature and moisture content have the greatest influence on unconfined strength. 7 refs., 7 figs., 11 tabs.

  4. The Effect of Polymer-Cement Stabilization on the Unconfined Compressive Strength of Liquefiable Soils

    OpenAIRE

    Ali Ateş

    2013-01-01

    Soil stabilization has been widely used as an alternative to substitute the lack of suitable material on site. The use of nontraditional chemical stabilizers in soil improvement is growing daily. In this study a laboratory experiment was conducted to evaluate the effects of waterborne polymer on unconfined compression strength and to study the effect of cement grout on pre-venting of liquefiable sandy soils. The laboratory tests were performed including grain size of sandy soil, unit weight, ...

  5. Effect Of Coir Fibres On The Compaction And Unconfined Compressive Strength Of Bentonite-Lime-Gypsum Mixture

    Directory of Open Access Journals (Sweden)

    Tilak B. Vidya

    2015-06-01

    Full Text Available This paper presents the effect of coir fibres on the compaction and unconfined compressive strength of a bentonite-lime-gypsum mixture. The coir fiber content varied from 0.5 to 2 %. The results indicated that the dry unit weight and the optimum moisture content of a bentonite – lime mix increased with the addition of gypsum. The unconfined compressive strength of the bentonite increased with the increase in the lime content up to 8 %. Beyond 8 %, the unconfined compressive strength decreased. The dry unit weight of the reference mix decreased, and the optimum moisture content increased with the addition of coir fibre. The unconfined compressive strength of the bentonite + 8 % lime mix increased up to 4 % with the gypsum. Beyond 4 %, the unconfined compressive strength decreased. The unconfined compressive strength of the reference mix increased with the addition of coir fibre up to a fibre content of 1.5 %. The unconfined compressive strength of the reference mix-coir fibre composite was less in comparison to the reference mix. The unconfined compressive strength of the bentonite increased with the addition of lime and gypsum and with the increase in the curing period. The improvement in the post-peak region was better for the reference mix with reinforced coir fibres as compared to the unreinforced reference mix. The improved post-peak behaviour of the bentonite-lime-gypsum-coir fibre mixture could boost the construction of temporary roads on such problematic soils. Further, its use will also provide an environmental motivation for providing a means of consuming large quantities of coir fibres.

  6. Prediction of zeolite-cement-sand unconfined compressive strength using polynomial neural network

    Science.gov (United States)

    MolaAbasi, H.; Shooshpasha, I.

    2016-04-01

    The improvement of local soils with cement and zeolite can provide great benefits, including strengthening slopes in slope stability problems, stabilizing problematic soils and preventing soil liquefaction. Recently, dosage methodologies are being developed for improved soils based on a rational criterion as it exists in concrete technology. There are numerous earlier studies showing the possibility of relating Unconfined Compressive Strength (UCS) and Cemented sand (CS) parameters (voids/cement ratio) as a power function fits. Taking into account the fact that the existing equations are incapable of estimating UCS for zeolite cemented sand mixture (ZCS) well, artificial intelligence methods are used for forecasting them. Polynomial-type neural network is applied to estimate the UCS from more simply determined index properties such as zeolite and cement content, porosity as well as curing time. In order to assess the merits of the proposed approach, a total number of 216 unconfined compressive tests have been done. A comparison is carried out between the experimentally measured UCS with the predictions in order to evaluate the performance of the current method. The results demonstrate that generalized polynomial-type neural network has a great ability for prediction of the UCS. At the end sensitivity analysis of the polynomial model is applied to study the influence of input parameters on model output. The sensitivity analysis reveals that cement and zeolite content have significant influence on predicting UCS.

  7. Development of K-Basin High-Strength Homogeneous Sludge Simulants and Correlations Between Unconfined Compressive Strength and Shear Strength

    Energy Technology Data Exchange (ETDEWEB)

    Onishi, Yasuo; Baer, Ellen BK; Chun, Jaehun; Yokuda, Satoru T.; Schmidt, Andrew J.; Sande, Susan; Buchmiller, William C.

    2011-02-20

    K-Basin sludge will be stored in the Sludge Transport and Storage Containers (STSCs) at an interim storage location on Central Plateau before being treated and packaged for disposal. During the storage period, sludge in the STSCs may consolidate/agglomerate, potentially resulting in high-shear-strength material. The Sludge Treatment Project (STP) plans to use water jets to retrieve K-Basin sludge after the interim storage. STP has identified shear strength to be a key parameter that should be bounded to verify the operability and performance of sludge retrieval systems. Determining the range of sludge shear strength is important to gain high confidence that a water-jet retrieval system can mobilize stored K-Basin sludge from the STSCs. The shear strength measurements will provide a basis for bounding sludge properties for mobilization and erosion. Thus, it is also important to develop potential simulants to investigate these phenomena. Long-term sludge storage tests conducted by Pacific Northwest National Laboratory (PNNL) show that high-uranium-content K-Basin sludge can self-cement and form a strong sludge with a bulk shear strength of up to 65 kPa. Some of this sludge has 'paste' and 'chunks' with shear strengths of approximately 3-5 kPa and 380-770 kPa, respectively. High-uranium-content sludge samples subjected to hydrothermal testing (e.g., 185 C, 10 hours) have been observed to form agglomerates with a shear strength up to 170 kPa. These high values were estimated by measured unconfined compressive strength (UCS) obtained with a pocket penetrometer. Due to its ease of use, it is anticipated that a pocket penetrometer will be used to acquire additional shear strength data from archived K-Basin sludge samples stored at the PNNL Radiochemical Processing Laboratory (RPL) hot cells. It is uncertain whether the pocket penetrometer provides accurate shear strength measurements of the material. To assess the bounding material strength and

  8. Effect of Industrial By-Products on Unconfined Compressive Strength of Solidified Organic Marine Clayey Soils

    Directory of Open Access Journals (Sweden)

    Chan-Gi Park

    2015-08-01

    Full Text Available The use of industrial by-products as admixture to ASTM Type I cement (ordinary Portland cement (OPC was investigated with the objective of improving the solidification of organic marine clayey soils. The industrial by-products considered in this paper were oyster-shell powder (OSP, steelmaking slag dust (SMS and fuel-gas-desulfurized (FGD gypsum. The industrial by-products were added to OPC at a ratio of 5% based on dry weight to produce a mixture used to solidify organic marine clayey soils. The dosage ratios of mixtures to organic marine clayey soils were 5, 10 and 15% on a dry weight basis. Unconfined compressive strength (UCS test after 28 days revealed that the highest strength was obtained with the OPC + SMS 15% mixing ratio. The UCS of specimens treated with this mixture was >500 kPa, compared with 300 kPa for specimens treated with a 15% OPC + OSP mixture and 200 kPa when 15% of OPC was used alone. These results were attributed to the more active hydration and pozzolanic reaction of the OPC + SMS mixture. This hypothesis was verified through X-ray diffraction (XRD and scanning electron microscopy (SEM analyses, and was confirmed by variations in the calcium carbonate (CaCO3 content of the materials during curing.

  9. Unconfined compressive strength test of composite mineral powder soil-cement%复合矿粉水泥土的无侧限抗压强度试验

    Institute of Scientific and Technical Information of China (English)

    马晓宇; 李平

    2014-01-01

    将工业中生产的废渣制作成的复合矿粉掺加至水泥土中,既增强其性能,同时也可达到利废环保的目的。通过室内无侧限抗压强度试验,运用正交试验方法研究了影响复合矿粉水泥土抗压强度的主要因素及其影响规律。通过极差和方差分析可知,水泥掺量对复合矿粉水泥土的无侧限抗压强度的影响最大,其次是龄期,复合矿粉的影响最小。复合矿粉水泥土的早期强度提高主要是由于水泥的水化,而由矿粉和粉煤灰组成的复合矿粉具有微集料效应和火山灰效应,从而可改善水泥土的强度。%To mix the soil-cement with composite mineral powder made from the slag in industrial production can reinforce the property of the soil-cement,and is also environment-friendly to utilize the waste.Based on the indoor unconfined compressive strength test,we investigated the main factors that influence the compressive strength of composite mineral powder soil-cement. Analysis of range and variance shows that cement content is the major factor affecting the unconfined compressive strength,fol-lowed by age and in the last place,composite mineral powder.The improvement of strength of composite mineral powder soil-ce-ment in the early period is mainly due to hydration of cement,while composite mineral powder which is made of mineral powder and fly ash has micro aggregate effect and pozzolanic effect.In general,the strength of soil-cement could be fairly improved.

  10. 废弃轮胎橡胶颗粒混合土无侧限抗压强度试验研究%Test on unconfined compressive strength of lightweight soil mixed with rubber chips of scrap tires

    Institute of Scientific and Technical Information of China (English)

    孔德森; 贾腾; 王晓敏; 张伟伟; 吴燕开

    2016-01-01

    In order to analyze the engineering characteristics of lightweight soil mixed with rubber chips of scrap tires (RST mixed soil), the unconfined compressive strength tests were carried out. Firstly, physical properties of the ingredient materials in RST mixed soil were studied. Then, the mixture ratio scheme and the preparation method of RST mixed soil samples were designed. Furthermore, influence laws of curing age, rubber-soil ratio, cement-soil ratio and water-soil ratio on the unconfined compressive strength of RST mixed soil samples were studied through unconfined compression tests. The results show that the unconfined compressive strength of RST mixed soil increases with the prolonging of curing age during the curing period of 28 d. When the cement-soil ratio is about 10%, the unconfined compressive strength of RST mixed soil is more sensitive to curing age. In addition, the unconfined compressive strength of RST mixed soil decreases with the increase of rubber-soil ratio, while it increases with the increase of cement-soil ratio. The optimal water-soil ratio of RST mixed soil corresponding to the unconfined compressive strength is about 25%.%为了分析废弃轮胎橡胶颗粒混合土(RST 混合土)的工程特性,采用无侧限抗压强度试验对 RST 混合土的无侧限抗压强度进行研究。首先,对组成RST混合土的原材料的物理特性进行分析,然后,进行RST混合土试样的配比方案设计和制备方法研究,进而采用无侧限抗压强度试验,研究养护龄期、胶粒土比、灰土比以及水土比对RST混合土无侧限抗压强度的影响规律。研究结果表明:在28 d的养护龄期内,RST混合土的无侧限抗压强度随养护龄期的延长而增大,且灰土比约为10%的RST混合土试样的无侧限抗压强度对养护龄期尤为敏感;RST混合土的无侧限抗压强度还随胶粒土比的增大而减小,随灰土比的增大而增大;RST混合土无侧限抗压

  11. Unconfined Compressive Strength Comparison between Saline Soils Reinforced with Rice Straw and with Wheat Straw%稻草加筋土和麦秸秆加筋土的无侧限抗压强度比较

    Institute of Scientific and Technical Information of China (English)

    张瑞敏; 王晓燕; 柴寿喜

    2011-01-01

    In order to increase the compressive characteristic of saline soil, saline soils reinforced with rice straw and with wheat straw were used to solve the problem of soil strength decrease due to salt expansion and dissolution. And then the unconfined compressive strengths of the saline soils reinforced with rice straw and with wheat straw were compared by selecting reinforced length, reinforced quality ratio, shapes, anticorrosive processing as influence factors. Test results show that: ①Unconfined compressive strength of the saline soil reinforced with natural rice straw and with antiseptic rice straw is higher than the saline soil reinforced with natural wheat straw and with antiseptic wheat straw; unconfined compressive strength of the two reinforced saline soils are higher than saline soil. ②The appropriate reinforcement condition office straw is as follows: reinforced length of 15 mm, reinforced quality ratio of 0.2%; the condition of wheat straw is as follows: reinforced length of 10 mm or 15 ram, reinforced quality ratio of 0.2% or 0.25%. ③As far as the shapes of rice straw and wheat straw are concerned, half tube shape is better than tubular shape, and the shape of a quarter is better than half. ④ Both rice straw and wheat straw need anti-corrosion treatment before reinforcing to improve the strength and durability of the rein- forced saline soil. Rice straw and wheat straw are suitable for reinforcement materials, rice straw reinforcement is better than that of wheat straw; both of them can be used for handling saline soil.%为解决因溶陷和盐胀引起土的强度降低问题,分别采用稻草和麦秸秆加筋滨海盐渍土,以提高其抗压性能.选择加筋长度、质量加筋率、筋材形状及防腐处理作为影响因素,比较稻草加筋土和麦秸秆加筋土的无侧限抗压强度.试验结果为:①天然稻草加筋土和防腐稻草加筋土的无侧限抗压强度相应地高于天然麦秸秆加筋土

  12. 含盐对长三角粉砂冻土无侧限抗压强度的影响%Effect of Salt to Unconfined Compressive Strength of Frozen Silt Soil from the Yangtze River Delta

    Institute of Scientific and Technical Information of China (English)

    胡向东; 张伟超; 王金泰; 虞兴福

    2016-01-01

    With the experiment means,an analysis was conducted on the strength features of the freezing salt content silt soil from the Yangtze River Delta and a study was conducted on the strength performances of the different salt content remolded soils under the different temperature.With the unconfined compressive strength as the study object,an analysis was conducted on the relationship between the freezing soil strength and the salt content and the relationship between the freezing soil strength and the salt content under the several typi-cal temperatures was obtained individually.The results showed that the freezing strength would be reduced in the index with the salinity increased and the reducing would be small when the soil was in a low temperature and in a high salinity.The test results could provide the theoretical basis to the artificial freezing method ap-plied to the offshore region and coastal region.%通过试验手段,对长三角粉砂含盐冻土的强度特性进行分析,研究了不同盐度的重塑土在不同温度下的强度表现。以无侧限抗压强度为研究对象,对冻土强度和含盐量的关系进行分析,分别得到了几个典型温度下的冻土强度和含盐量的关系。结果表明:强度随盐度的增大而成指数降低,降低幅度在低温和高盐度时较小。试验结果可为近海、沿海地区人工冻结法提供理论基础。

  13. 掺加纳米材料水泥土无侧限抗压强度试验研究∗%Research on Unconfined Compressive Strength of Soil Cement with Nano Structured Materials

    Institute of Scientific and Technical Information of China (English)

    2015-01-01

    把纳米SiO2、纳米Al2 O3和纳米蒙脱土3种纳米材料加入普通水泥土中,制备掺加纳米材料的水泥土。通过室内无侧限抗压强度试验,研究不同纳米材料及其掺量、龄期、水泥掺量、水胶比对添加纳米材料水泥土无侧限抗压强度的影响,为添加纳米材料水泥土的进一步研究及其在实际工程中的应用提供了方向。%Nano⁃SiO2 , nano⁃Al2 O3 and nano⁃montmorillonite are added into plain soil cement as the admixtures. The influence of various factors including the variety and content of nano structured materials, the age, the content of cement, the water⁃to⁃binder ( the sum of cement and nano structured materials) ratio on the unconfined compressive strength of soil cement is studied. The direction of the further study and the practical application of soil cement with nano structured materials is provided.

  14. Experimental study on unconfined compressive strength of clays stabilized with fly ash and slag%粉煤灰炉渣加固土的室内无侧限抗压强度试验研究

    Institute of Scientific and Technical Information of China (English)

    庄心善; 王功勋; 朱瑞赓; 田苾

    2005-01-01

    This paper presents the experimental results on unconfined compressive strength (UCS) of the clays stabilized with industrial wastes such as fly ash and slag. Three kinds of the compound clays are produced with different proportions of fly ash, clay, sand, mud and slag, and then the compound clays are reinforced by cement, lime, and their combination respectively. The experimental results obtained from the laboratory tests show that the compound clays with fly ash can be best reinforced by cement instead of lime or combination of cement and lime. The relationship among UCS, curing time and cement content has been verified by the laboratory test results in this study. For the compound clays with slag, lime is the most suitable stabilizing agent, and the optimal lime content is around 15% in weight for the soil stabilization in Wuhan areas.%给出了用粉煤灰、炉渣等工业废料加固土的室内无侧限抗压强度试验结果,分析了加固土无侧限抗压强度与外加剂掺量、养护龄期之间的影响规律,得出了针对不同工业废料加固土所用外加剂的最佳掺量.

  15. Determination of Friction Coefficient in Unconfined Compression of Brain Tissue

    CERN Document Server

    Rashid, Badar; Gilchrist, Michael; 10.1016/j.jmbbm.2012.05.001

    2013-01-01

    Unconfined compression tests are more convenient to perform on cylindrical samples of brain tissue than tensile tests in order to estimate mechanical properties of the brain tissue because they allow for homogeneous deformations. The reliability of these tests depends significantly on the amount of friction generated at the specimen/platen interface. Thus, there is a crucial need to find an approximate value of the friction coefficient in order to predict a possible overestimation of stresses during unconfined compression tests. In this study, a combined experimental-computational approach was adopted to estimate the dynamic friction coefficient mu of porcine brain matter against metal platens in compressive tests. Cylindrical samples of porcine brain tissue were tested up to 30% strain at variable strain rates, both under bonded and lubricated conditions in the same controlled environment. It was established that mu was equal to 0.09 +/- 0.03, 0.18 +/- 0.04, 0.18 +/- 0.04 and 0.20 +/- 0.02 at strain rates of...

  16. Analysis of Comparison between Unconfined and Confined Condition of Foamed Concrete Under Uni-Axial Compressive Load

    Directory of Open Access Journals (Sweden)

    Mohd Zairul A. Abdul Rahman

    2010-01-01

    Full Text Available Problem statement: Foamed concrete has become most commercial material in construction industry. People in industries were come out with the new mix design of foamed concrete to meet the specification and the requirements needed. Approach: This is because foamed concrete has the possibility as alternative of lightweight concrete for producing intermediate strength capabilities with excellent thermal insulation, freeze-thaw resistance, high-impact resistance and good shock absorption. Results: Currently Standard test to measure the compressive strength of foamed concrete is using standard unconfined compressive test. Several research has been conduct but the compressive strength using standard unconfined compressive test not capture true behavior of foamed concrete because it just achieved only low compressive strength and sample under compression failed due to brittle collapse of the sample. This paper was analyses the comparison between standard compressive test and confined compressive test. The confinement test introduced to prevent sample from brittle collapse. Foamed concrete cylindrical sample has been investigated under the standard compressive test for hard concrete (ASTM-C39. Based on the research, samples are produced under unconfined and confined condition. Analysis has been done and the result show that under standard compressive test, the sample failed due to early crack initiation and failed. Confinement condition was increase the compressive strength but this condition influence the result. Conclusion/Recommendations: Standard test is not suitable to capture the true behavior of foamed concrete, and to prevent the sample from brittle collapse during the test, new testing method was introduced to capture the true behavior of foamed concrete which is using Quasi Static Indentation Test. This test can be used to study about the behaviour of foamed concrete before it can be implemented to its final application.

  17. 胶凝材料性质对干混砂浆抗压强度的影响研究%Influence of the properties of cementing materials on the unconfined compressive strengths of dry-mixed mortar

    Institute of Scientific and Technical Information of China (English)

    郑娟荣; 赵雪飞

    2014-01-01

    为了研究胶凝材料性质对干混砂浆抗压强度的影响规律,共制备了24组样品,其中3组样品的微观形貌和孔结构采用扫描电子显微镜和压汞测孔仪(Autopore IV 9500)等测试手段进行了分析。试验结果表明:无论胶凝材料是100%水泥、50%水泥+50%矿渣粉和50%水泥+50%粉煤灰,7 d和28 d砂浆抗压强度均随胶凝材料总量增加而明显提高,增加水泥掺量对砂浆早期强度有利;与以100%水泥为胶凝材料制备的砂浆相比,当每吨干混砂浆中胶凝材料总量分别为100、150、200、250 kg时,以50%水泥+50%矿渣粉为胶凝材料制备的砂浆的抗压强度分别提高47%、55%、10%和0,而以50%水泥+50%粉煤灰为胶凝材料制备的砂浆的抗压强度分别降低77%、66%、56%和44%。与15%水泥制备的砂浆28 d硬化体相比,7.5%水泥+7.5%矿渣制备的砂浆28 d硬化体中水化产物更多或更分散、基体与骨料结合更密实、总孔隙更低及孔径更细;7.5%水泥+7.5%粉煤灰制备的砂浆28 d硬化体中水化产物更少、基体更松散、总孔隙更高及孔径更大。%24 groups of samples were made so as to investigating the influence of the properties of cementing materials on the uncon-fined compressive strengths (UCS) of dry-mixed mortar.The morphology and pore structure of 3 groups of 24 samples were investigated by scanning electron microscope(SEM) and mercury intrusion porosimeter(Autopore IV 9500)(MIP).The results showed that the 7 d and 28 d UCS of hardened mortars increased with the increase of the total content of cementing materials no matter what cementing materials were 100%cement and 50%cement+50%slag powder and 50%cement+50%fly-ash ,and the increase of cement content was in favour of early strength of hardened mortar.Comparing with the hardened mortar of 100%cement as cementing material ,the 28 d UCS of the hard-ened mortar of 50%cement+50%slag powder as cementing material respectively

  18. Effects of friction on the unconfined compressive response of articular cartilage: a finite element analysis.

    Science.gov (United States)

    Spilker, R L; Suh, J K; Mow, V C

    1990-05-01

    A finite element analysis is used to study a previously unresolved issue of the effects of platen-specimen friction on the response of the unconfined compression test; effects of platen permeability are also determined. The finite element formulation is based on the linear KLM biphasic model for articular cartilage and other hydrated soft tissues. A Galerkin weighted residual method is applied to both the solid phase and the fluid phase, and the continuity equation for the intrinsically incompressible binary mixture is introduced via a penalty method. The solid phase displacements and fluid phase velocities are interpolated for each element in terms of unknown nodal values, producing a system of first order differential equations which are solved using a standard numerical finite difference technique. An axisymmetric element of quadrilateral cross-section is developed and applied to the mechanical test problem of a cylindrical specimen of soft tissue in unconfined compression. These studies show that interfacial friction plays a major role in the unconfined compression response of articular cartilage specimens with small thickness to diameter ratios. PMID:2345443

  19. Influencing factors of compressive strength of solidified inshore saline soil using SH lime-ash

    Institute of Scientific and Technical Information of China (English)

    覃银辉; 刘付华; 周琦

    2008-01-01

    Through unconfined compressive strength test,influencing factors on compressive strength of solidified inshore saline soil with SH lime-ash,ratio of lime-ash(1-K),quantity of lime-ash,age,degree of compression and salt content were studied.The results show that because inshore saline soil has special engineering characteristic,more influencing factors must be considered compared with ordinary soil for the perfect effect of solidifying.

  20. Thermo-mechanical cementation effects in bentonite investigated by unconfined compression tests

    Energy Technology Data Exchange (ETDEWEB)

    Dueck, Ann (Clay Technology AB, Lund (Sweden))

    2010-01-15

    Results from the project LOT showed that specimens exposed to warm conditions had a significantly reduced strain at failure compared to reference material. The objective of the present study was to investigate the impact of parameters such as temperature, density, water content and degree of saturation on the occurrence of brittleness at failure of bentonite specimens. To quantify the influence of the different parameters the unconfined compression test was used on specimens with a height and diameter of 20 mm. In this test the relation between stress and strain is determined from axial compression of a cylindrical specimen. Brittle failure is in this investigation mainly seen on specimens having a density of rho >= 2,060 kg/m3 or on specimens exposed to high temperature T >= 150 deg C in the laboratory. Brittle failure behaviour was also seen on unsaturated specimens with a degree of saturation less than Sr < 90%. Failure at reduced strain was seen in this investigation on specimens exposed to T = 150 deg C, on specimens having a water content of w{sub i} = 0% before saturation, on specimens with a final degree of saturation of S{sub r} <= 97% and also on one specimen subjected to consolidation during preparation. Brittle failure and reduced strain were noticed in the heated field exposed material in the LOT project. Similar behaviour was also observed in the present short term laboratory tests. However, the specimens in the present study showing this behaviour had higher density, lower degree of saturation or were exposed to higher temperatures than the field exposed specimens

  1. Strain distribution in the intervertebral disc under unconfined compression and tension load by the optimized digital image correlation technique.

    Science.gov (United States)

    Liu, Qing; Wang, Tai-Yong; Yang, Xiu-Ping; Li, Kun; Gao, Li-Lan; Zhang, Chun-Qiu; Guo, Yue-Hong

    2014-04-01

    The unconfined compression and tension experiments of the intervertebral disc were conducted by applying an optimized digital image correlation technique, and the internal strain distribution was analysed for the disc. It was found that the axial strain values of different positions increased obviously with the increase in loads, while inner annulus fibrosus and posterior annulus fibrosus experienced higher axial strains than the outer annulus fibrosus and anterior annulus fibrosus. Deep annulus fibrosus exhibited higher compressive and tensile axial strains than superficial annulus fibrosus for the anterior region, while there was an opposite result for the posterior region. It was noted that all samples demonstrated a nonlinear stress-strain profile in the process of deforming, and an elastic region was shown once the sample was deformed beyond its toe region.

  2. Strain distribution in the intervertebral disc under unconfined compression and tension load by the optimized digital image correlation technique.

    Science.gov (United States)

    Liu, Qing; Wang, Tai-Yong; Yang, Xiu-Ping; Li, Kun; Gao, Li-Lan; Zhang, Chun-Qiu; Guo, Yue-Hong

    2014-04-01

    The unconfined compression and tension experiments of the intervertebral disc were conducted by applying an optimized digital image correlation technique, and the internal strain distribution was analysed for the disc. It was found that the axial strain values of different positions increased obviously with the increase in loads, while inner annulus fibrosus and posterior annulus fibrosus experienced higher axial strains than the outer annulus fibrosus and anterior annulus fibrosus. Deep annulus fibrosus exhibited higher compressive and tensile axial strains than superficial annulus fibrosus for the anterior region, while there was an opposite result for the posterior region. It was noted that all samples demonstrated a nonlinear stress-strain profile in the process of deforming, and an elastic region was shown once the sample was deformed beyond its toe region. PMID:24718863

  3. COMPRESSIVE STRENGTH TESTING OF EARTH MORTARS

    Directory of Open Access Journals (Sweden)

    Givanildo Alves Azeredo

    2007-06-01

    Full Text Available This paper discusses the compressive strength of earth mortars. The goal is to use these mortars for masonry construction. Although it is necessary to study the whole masonry behaviour, the scope of this paper refers to the mortar only, without taking into account the blocks. As with other masonry units, compressive strength is a basic measure of quality for masonry mortars. However, there is a great variety of methodology for determining their parameters and properties, such as different samples geometry, the way strains are measured and also the platen restraint effect adopted. The present paper outlines certain experimental devices used to determine compressive strength of earth mortars and tries to show their influence on the properties determined. Proposals for the future development of testing earth mortars are outlined.

  4. COMPRESSIVE STRENGTH CHARACTERISTICS OF TILE WASTE CONCRETE

    OpenAIRE

    Ofonime A. Harry*, Ifiok E. Ekop

    2016-01-01

    Increase in the use of concrete in construction industry in Nigeria has led to the rise in the cost of its constituent material. This has necessitated research into the use of alternative material which is cheaper and can produce a comparable level of strength as the conventionally used ones. This paper present the results of an investigation into the compressive strength characteristics of concrete made with ceramic tile waste as coarse aggregates. The percentage of tile waste was varied in ...

  5. Experimental validation of a flat punch indentation methodology calibrated against unconfined compression tests for determination of soft tissue biomechanics.

    Science.gov (United States)

    Delaine-Smith, R M; Burney, S; Balkwill, F R; Knight, M M

    2016-07-01

    Mechanical characterisation of soft biological tissues using standard compression or tensile testing presents a significant challenge due to specimen geometrical irregularities, difficulties in cutting intact and appropriately sized test samples, and issues with slippage or damage at the grips. Indentation can overcome these problems but requires fitting a model to the resulting load-displacement data in order to calculate moduli. Despite the widespread use of this technique, few studies experimentally validate their chosen model or compensate for boundary effects. In this study, viscoelastic hydrogels of different concentrations and dimensions were used to calibrate an indentation technique performed at large specimen-strain deformation (20%) and analysed with a range of routinely used mathematical models. A rigid, flat-ended cylindrical indenter was applied to each specimen from which 'indentation moduli' and relaxation properties were calculated and compared against values obtained from unconfined compression. Only one indentation model showed good agreement (<10% difference) with all moduli values obtained from compression. A sample thickness to indenter diameter ratio ≥1:1 and sample diameter to indenter diameter ratio ≥4:1 was necessary to achieve the greatest accuracy. However, it is not always possible to use biological samples within these limits, therefore we developed a series of correction factors. The approach was validated using human diseased omentum and bovine articular cartilage resulting in mechanical properties closely matching compression values. We therefore present a widely useable indentation analysis method to allow more accurate calculation of material mechanics which is important in the study of soft tissue development, ageing, health and disease. PMID:26974584

  6. Compressive strength of thick composite panels

    DEFF Research Database (Denmark)

    Branner, Kim; Berring, Peter

    2011-01-01

    The aim of this study is to investigate how much the compressive strength of thick composite panels is reduced due to delaminations and to investigate under which conditions a delamination will grow. Understanding of this is essential in order to move forward the design limits used in the structu......The aim of this study is to investigate how much the compressive strength of thick composite panels is reduced due to delaminations and to investigate under which conditions a delamination will grow. Understanding of this is essential in order to move forward the design limits used...... in the structural design process. Results obtained from finite element modeling analyses are compared with an experimental test campaign performed on flat composite panels with and without delaminations....

  7. Load Bearing and Deformation Characteristics of Granular Spoils under Unconfined Compressive Loading for Coal Mine Backfill

    Directory of Open Access Journals (Sweden)

    Guodong Li

    2016-01-01

    Full Text Available The load bearing capacity and deformation response of granular spoils under uniaxial compression are numerically and experimentally investigated, aiming to shed light on the performance of back filled waste spoils while controlling ground subsidence after coal extraction. In numerical study, the particles are assembled in PFC commercial code in light of the digitized real shape of spoils with image technique, which is proved to be consistent with the physical test. The results from numerical and laboratory experiments showed that the complete compressive process of spoils tended to have spatial and temporal characteristics. The load-strain curves of investigated specimens could be divided into three stages (stage I, rearranging stage; stage II, breaking stage; stage III, consolidating stage and three zones (I, rearranging zone; II, interlocking zone; III, consolidated zone from outside to inside. During stage I, the load increasing rate of smaller spoils is relatively low, but it increases faster than larger ones in stages II and III. In addition, spoils with Talbot’s gradation are greater than single gradations. The magnitude of the density in consolidated zone is maximum, indicating that it is the main part holding the overlying strata weight.

  8. Compressive strength of delaminated aerospace composites.

    Science.gov (United States)

    Butler, Richard; Rhead, Andrew T; Liu, Wenli; Kontis, Nikolaos

    2012-04-28

    An efficient analytical model is described which predicts the value of compressive strain below which buckle-driven propagation of delaminations in aerospace composites will not occur. An extension of this efficient strip model which accounts for propagation transverse to the direction of applied compression is derived. In order to provide validation for the strip model a number of laminates were artificially delaminated producing a range of thin anisotropic sub-laminates made up of 0°, ±45° and 90° plies that displayed varied buckling and delamination propagation phenomena. These laminates were subsequently subject to experimental compression testing and nonlinear finite element analysis (FEA) using cohesive elements. Comparison of strip model results with those from experiments indicates that the model can conservatively predict the strain at which propagation occurs to within 10 per cent of experimental values provided (i) the thin-film assumption made in the modelling methodology holds and (ii) full elastic coupling effects do not play a significant role in the post-buckling of the sub-laminate. With such provision, the model was more accurate and produced fewer non-conservative results than FEA. The accuracy and efficiency of the model make it well suited to application in optimum ply-stacking algorithms to maximize laminate strength.

  9. Size effect on compressive strength of reactive powder concrete

    Institute of Scientific and Technical Information of China (English)

    AN Ming-zhe; ZHANG Li-jun; YI Quan-xin

    2008-01-01

    In this paper the coefficient and law of the size effect of RPC were studied through experiments and theoretical analysis. The size-effect coefficients for the compressive strength of RPC are deduced through experiments. They indicate that RPC without fiber behaves quite the same as normal or high strength concrete. The size effect on compressive strength is more prominent in RPC containing fiber. Bazant's size effect formula of compressive strength applies to RPC. A formula is given to predict the compressive strength of cubic RPC specimens 100 mm on a side where the fiber dosage ranges from 0-2%.

  10. Axial Compressive Strength of Foamcrete with Different Profiles and Dimensions

    Directory of Open Access Journals (Sweden)

    Othuman Mydin M.A.

    2014-01-01

    Full Text Available Lightweight foamcrete is a versatile material; primarily consist of a cement based mortar mixed with at least 20% volume of air. High flow ability, lower self-weight, minimal requirement of aggregate, controlled low strength and good thermal insulation properties are a few characteristics of foamcrete. Its dry densities, typically, is below 1600kg/m3 with compressive strengths maximum of 15MPa. The ASTM standard provision specifies a correction factor for concrete strengths of between 14 and 42MPa to compensate for the reduced strength when the aspect height-to-diameter ratio of specimen is less than 2.0, while the CEB-FIP provision specifically mentions the ratio of 150 x 300mm cylinder strength to 150 mm cube strength. However, both provisions requirements do not specifically clarify the applicability and/or modification of the correction factors for the compressive strength of foamcrete. This proposed laboratory work is intended to study the effect of different dimensions and profiles on the axial compressive strength of concrete. Specimens of various dimensions and profiles are cast with square and circular cross-sections i.e., cubes, prisms and cylinders, and to investigate their behavior in compression strength at 7 and 28 days. Hypothetically, compressive strength will decrease with the increase of concrete specimen dimension and concrete specimen with cube profile would yield comparable compressive strength to cylinder (100 x 100 x 100mm cube to 100dia x 200mm cylinder.

  11. The uniaxial compressive strength of the Arctic summer sea ice

    Institute of Scientific and Technical Information of China (English)

    HAN Hongwei; LI Zhijun; HUANG Wenfeng; LU Peng; LEI Ruibo

    2015-01-01

    The results on the uniaxial compressive strength of Arctic summer sea ice are presented based on the sam-ples collected during the fifth Chinese National Arctic Research Expedition in 2012 (CHINARE-2012). Exper-imental studies were carried out at different testing temperatures (−3, −6 and −9°C), and vertical samples were loaded at stress rates ranging from 0.001 to 1 MPa/s. The temperature, density, and salinity of the ice were measured to calculate the total porosity of the ice. In order to study the effects of the total porosity and the density on the uniaxial compressive strength, the measured strengths for a narrow range of stress rates from 0.01 to 0.03 MPa/s were analyzed. The results show that the uniaxial compressive strength decreases linearly with increasing total porosity, and when the density was lower than 0.86 g/cm3, the uniaxial com-pressive strength increases in a power-law manner with density. The uniaxial compressive behavior of the Arctic summer sea ice is sensitive to the loading rate, and the peak uniaxial compressive strength is reached in the brittle-ductile transition range. The dependence of the strength on the temperature shows that the calculated average strength in the brittle-ductile transition range, which was considered as the peak uniaxial compressive strength, increases steadily in the temperature range from −3 to −9°C.

  12. Compressive Strength of Compacted Clay-Sand Mixes

    Directory of Open Access Journals (Sweden)

    Faseel Suleman Khan

    2014-01-01

    Full Text Available The use of sand to improve the strength of natural clays provides a viable alternative for civil infrastructure construction involving earthwork. The main objective of this note was to investigate the compressive strength of compacted clay-sand mixes. A natural clay of high plasticity was mixed with 20% and 40% sand (SP and their compaction and strength properties were determined. Results indicated that the investigated materials exhibited a brittle behaviour on the dry side of optimum and a ductile behaviour on the wet side of optimum. For each material, the compressive strength increased with an increase in density following a power law function. Conversely, the compressive strength increased with decreasing water content of the material following a similar function. Finally, the compressive strength decreased with an increase in sand content because of increased material heterogeneity and loss of sand grains from the sides during shearing.

  13. Application of size effect to compressive strength of concrete members

    Indian Academy of Sciences (India)

    Jin-Keun Kim; Seong-Tae Yi

    2002-08-01

    It is important to consider the effect of size when estimating the ultimate strength of a concrete member under various loading conditions. Well known as the size effect, the strength of a member tends to decrease when its size increases. Therefore, in view of recent increased interest in the size effect of concrete this research focuses on the size effect of two main classes of compressive strength of concrete: pure axial compressive strength and flexural compressive strength. First, fracture mechanics type size effect on the compressive strength of cylindrical concrete specimens was studied, with the diameter, and the height/diameter ratio considered as the main parameters. Theoretical and statistical analyses were conducted, and a size effect equation was proposed to predict the compressive strength specimens. The proposed equation showed good agreement with the existing test results for concrete cylinders. Second, the size, length, and depth variations of a flexural compressive member have been studied experimentally. A series of -shaped specimens subjected to axial compressive load and bending moment were tested. The shape of specimens and the test procedures used were similar to those by Hognestad and others. The test results are curve-fitted using Levenberg-Marquardt’s least squares method (LSM) to obtain parameters for the modified size effect law (MSEL) by Kim and co workers. The results of the analysis show that the effect of specimen size, length, and depth on ultimate strength is significant. Finally, more general parameters for MSEL are suggested.

  14. Ultimate Strength Analysis of Stiffened Plate Under Longitudinal Compression, Transverse Compression and Lateral Pressure

    Directory of Open Access Journals (Sweden)

    Ta Hong Phong1a,

    2015-10-01

    Full Text Available The ship hull can be considered as a thin – walled box gider constituted by stiffened panels. In order to research the ship ultimate strength, the ultimate strength of stiffened panel must be considered. Stiffened plates are typical structure of ship. Ultimate strength analysis of stiffened plate for the analysis of ships' structures. In present paper, the nonlinear finite element method is employed to predict the ultimate strength of stiffened plate model under longitudinal compression, transverse compression, lateral pressure.

  15. Strength Regularity and Failure Criterion of High-Strength High-Performance Concrete under Multiaxial Compression

    Institute of Scientific and Technical Information of China (English)

    HE Zhen-jun; SONG Yu-pu

    2008-01-01

    Multiaxial compression tests were performed on 100 mm × 100 mm × 100 nun high-strength high-performance concrete (HSHPC) cubes and normal strength concrete (NSC) cubes. The failure modes of specimens were presented, the static compressive strengths in principal directions were measured, the influence of the stress ratios was analyzed. The experimental results show that the ultimate strengths for HSHPC and NSC under multiaxial compression are greater than the uniaxial compressive strengths at all stress ratios, and the multiaxial strength is dependent on the brittleness and stiffness of concrete, the stress state and the stress ratios. In addition, the Kupfer-Gerstle and Ottosen's failure criteria for plain HSHPC and NSC under multiaxial compressive loading were modified.

  16. Effect of magnesia on the compressive strength of pellets

    Institute of Scientific and Technical Information of China (English)

    Feng-man Shen; Qiang-jian Gao; Xin Jiang; Guo Wei; Hai-yan Zheng

    2014-01-01

    The compressive strength of MgO-fluxed pellets was investigated before and after they were reduced. The porosity and pore size of green pellets, product pellets, and reduced pellets were analyzed to clarify how MgO affects the strength of the pellets. Experimental re-sults show that when the MgO-bearing flux content in the pellets increases from 0.0wt%to 2.0wt%, the compressive strength of the pellets at ambient temperature decreases, but the compressive strength of the pellets after reduction increases. Therefore, the compressive strength of the pellets after reduction exhibits no certain positive correlation with that before reduction. The porosity and pore size of all the pellets (with different MgO contents) increase when the pellets are reduced. However, the increase in porosity of the MgO-fluxed pellets is relatively smaller than that of the traditional non-MgO-fluxed pellets, and the pore size range of the MgO-fluxed pellets is relatively narrower. The re-duction swelling index (RSI) is a key factor for governing the compressive strength of the reduced pellets. An approximately reversed linear relation can be concluded that the lower the RSI, the greater the compressive strength of the reduced pellets is.

  17. Compressive strength of brick masonry made with weak mortars

    DEFF Research Database (Denmark)

    Pedersen, Erik Steen; Hansen, Klavs Feilberg

    2013-01-01

    The use of weak mortar has a number of advantages (e.g. prevention of expansion joints, environmental issues). However, according to EC6, the strength of masonry vanishes when the compressive strength of the mortar approaches zero. In reality the presence of even unhardened mortar kept in place...... in the joint will ensure a certain level of load-carrying capacity. This is due to the interaction between compression in the weak mortar and tension in the adjacent bricks. This paper proposes an expression for the compressive strength of masonry made with weak lime mortars (fm... of masonry depends only on the strength of the bricks. A compression failure in masonry made with weak mortars occurs as a tension failure in the bricks, as they seek to prevent the mortar from being pressed out of the joints. The expression is derived by assuming hydrostatic pressure in the mortar joints...

  18. Analysis of Homogel Uniaxial Compression Strength on Bio Grouting Material

    OpenAIRE

    Kyungho Park; Daehyeon Kim

    2016-01-01

    This study analyzed uniaxial compression strength over time by preparing a homogel specimen from a bio grouting material, a cement-like form produced by environment-friendly microbial reactions. Among chemical grouting methods, the most commonly used method is the Labile Waterglass method. In this study, the homogel uniaxial compressive strength of Labile Waterglass (LW) injection material and that of bio grouting material were measured and analyzed. In order to perform the experiment, a tota...

  19. Compressive Strength of Longitudinally Stiffened GRP Panels

    DEFF Research Database (Denmark)

    Böhme, J.; Noury, P.; Riber, Hans Jørgen;

    1996-01-01

    A structural analysis of a cross stiffened orthotropic GRP panel subjected to uniaxial compressive loads is carried out. Analytical solutions to the buckling of such structures are proposed and validated by a finite element analysis. Both analytical and finite element approaches confirm an identi...

  20. Static strength of gold compressed up to 127 GPa

    Institute of Scientific and Technical Information of China (English)

    Jing Qiu-Min; Wu Qiang; Liu Lei; Bi Yan; Zhang Yi; Liu Sheng-Gang; Xu Ji-An

    2012-01-01

    Gold powder is compressed non-hydrostatically up to 127 GPa in a diamond anvil cell (DAC),and its angle dispersive X-ray diffraction patterns are recorded.The compressive strength of gold is investigated in a framework of the lattice strain theory by the line shift analysis.The result shows that the compressive strength of gold increases continuously with the pressure up to 106 GPa and reaches 2.8 GPa at the highest experimental pressure (127 GPa) achieved in our study.This result is in good agreement with our previous experimental result in a relevant pressure range.The compressive strength of gold may be the major source of the error in the equation-of-state measurement in various pressure environments.

  1. TRIAXIAL COMPRESSIVE STRENGTH OF ULTRA HIGH PERFORMANCE CONCRETE

    Directory of Open Access Journals (Sweden)

    Radoslav Sovják

    2013-12-01

    Full Text Available The aim of this work is to describe the strength of Ultra High Performance Concrete (UHPC under triaxial compression. The main goal is to find a trend in the triaxial compressive strength development under various values of confinement pressure. The importance of triaxial tests lies in the spatial loading of the sample, which simulates the real loading of the material in the structure better than conventional uniaxial strength tests. In addition, the authors describe a formulation process for UHPC that has been developed without using heat treatment, pressure or a special mixer. Only ordinary materials available commercially in the Czech Republic were utilized throughout the material design process.

  2. Compressive Strength and Permeability of High-performance Concrete

    Institute of Scientific and Technical Information of China (English)

    Lü Jianfu; GUAN Hui; ZHAO Weixuan; BA Hengjing

    2011-01-01

    The compressive strength, chloride penetration resistance and microstructure of two high-performance concretes were examined under three curing conditions. Curing conditions include standard curing (SC), matched curing (MC, which means sealed concrete specimens curing at temperature controlled box) and matched curing of naked concrete (NMC) according to development law of temperature measured in mass concrete on site. Results indicate that concrete under MC and NMC show higher resistance to chloride penetration than the one under SC. Concrete under MC has slightly lower chloride penetration than those under NMC, but the compressive strength of specimens under NMC was higher than the one under MC at 56 d. In addition, concrete under NMC and MC have higher early strength than under SC, especially at early age. However, the order of curing conditions affecting compressive strength of concrete at 248 day is: SC>NMC>MC.

  3. Compression strength perpendicular to grain of structural timber and glulam

    DEFF Research Database (Denmark)

    Damkilde, Lars; Hoffmeyer, Preben; Pedersen, Torben N.

    1998-01-01

    The characteristic strength values for compression perpendicular to grain as they appear in EN 338 (structural timber) and EN 1194 (glulam) are currently up for discussion. The present paper provides experimental results based on EN 1193 that may assist in the correct assignment of such strength...... values. The dominant failure mode of glulam specimens is shown to be fundamentally different from that of structural timber specimens. Glulam specimens often show tension perpendicular to grain failure before the compression strength value is reached. Such failure mode is not seen for structural timber....... Nonetheless test results show that the levels of characteristic compression strength perpendicular to grain are of the same order for structural timber and glulam. The values are slightly lower than those appearing in EN 1194 and less than half of those appearing in EN 338. The paper presents a numerical...

  4. Calcite-forming bacteria for compressive strength improvement in mortar.

    Science.gov (United States)

    Park, Sung-Jin; Park, Yu-Mi; Chun, Woo-Young; Kim, Wha-Jung; Ghim, Sa-Youl

    2010-04-01

    Microbiological calcium carbonate precipitation (MCP) has been investigated for its ability to improve the compressive strength of concrete mortar. However, very few studies have been conducted on the use of calcite-forming bacteria (CFB) to improve compressive strength. In this study, we discovered new bacterial genera that are capable of improving the compressive strength of concrete mortar. We isolated 4 CFB from 7 environmental concrete structures. Using sequence analysis of the 16S rRNA genes, the CFB could be partially identified as Sporosarcina soli KNUC401, Bacillus massiliensis KNUC402, Arthrobacter crystallopoietes KNUC403, and Lysinibacillus fusiformis KNUC404. Crystal aggregates were apparent in the bacterial colonies grown on an agar medium. Stereomicroscopy, scanning electron microscopy, and x-ray diffraction analyses illustrated both the crystal growth and the crystalline structure of the CaCO3 crystals. We used the isolates to improve the compressive strength of concrete mortar cubes and found that KNUC403 offered the best improvement in compressive strength.

  5. PREPARATION OF BIOACTIVE NANOSTRUCTURE SCAFFOLD WITH IMPROVED COMPRESSIVE STRENGTH

    Directory of Open Access Journals (Sweden)

    R. EMADI

    2011-03-01

    Full Text Available Highly porous scaffolds with open structure are today the best candidates for bone substitution to ensure bone oxygenation and angiogenesis. In this study, we developed a new route to enhance the compressive strength of porous hydroxyapatite scaffold made of natural bone. Briefly, the spongy bone of an adult bovine was extracted, annealed, and coated by a nanostructure bioactive glass layer to be subsequently sintered at different temperatures. The apatite formation ability on the surfaces of the coated scaffolds was investigated by standard procedures. Our results showed that the scaffold and coating microstructure consisted of the grains smaller than 100 nm. These nanostructures improved the compressive strength and bioactivity of highly porous scaffold. The results showed that with increasing the sintering temperature, the compressive strength of scaffolds increased while their in vitro bioactivity decreased.

  6. Prediction of Concrete Compressive Strength by Evolutionary Artificial Neural Networks

    Directory of Open Access Journals (Sweden)

    Mehdi Nikoo

    2015-01-01

    Full Text Available Compressive strength of concrete has been predicted using evolutionary artificial neural networks (EANNs as a combination of artificial neural network (ANN and evolutionary search procedures, such as genetic algorithms (GA. In this paper for purpose of constructing models samples of cylindrical concrete parts with different characteristics have been used with 173 experimental data patterns. Water-cement ratio, maximum sand size, amount of gravel, cement, 3/4 sand, 3/8 sand, and coefficient of soft sand parameters were considered as inputs; and using the ANN models, the compressive strength of concrete is calculated. Moreover, using GA, the number of layers and nodes and weights are optimized in ANN models. In order to evaluate the accuracy of the model, the optimized ANN model is compared with the multiple linear regression (MLR model. The results of simulation verify that the recommended ANN model enjoys more flexibility, capability, and accuracy in predicting the compressive strength of concrete.

  7. Effect Of Salt Water On Compressive Strength Of Concrete

    Directory of Open Access Journals (Sweden)

    Preeti Tiwari

    2014-04-01

    Full Text Available In this research work, the effect of salt water on the compressive strength of concrete was investigated. This paper therefore presents the result and findings of an experimental research on the effect of salt water on compressive strength of concrete. For this concrete cubes were cast using fresh wi and salt water for a design mix of M-30 1:1.8:3.31 by weight of concrete, and 0.45 water- cement ratio. Half of concrete cubes were cast and cured with fresh water and remaining half cubes were cast and cured with salt water. The concrete cubes were cured for 7,14 and 28 days respectively. The result of the average compressive strength of concrete obtained using fresh water ranges from 27.12 - 39.12N/mm2 and using salt water ranges from 28.45 – 41.34N/mm2

  8. Non-Uniform Compressive Strength of Debonded Sandwich Panels

    DEFF Research Database (Denmark)

    Nøkkentved, Alexandros; Lundsgaard-Larsen, Christian; Berggreen, Carl Christian

    2005-01-01

    Face/core debond-damaged sandwich panels exposed to non-uniform compression loads are studied. The panel geometry is rectangular with a centrally located circular debond. The study primarily includes experimental methods, but simple finite element calculations are also applied. The complexity...... debonds show a considerable strength reduction with increasing debond diameter, with failure mechanisms varying between fast debond propagation and wrinkling-introduced face compression failure for large and small debonds, respectively. Residual strength predictions are based on intact panel testing...

  9. Effect Of Salt Water On Compressive Strength Of Concrete

    OpenAIRE

    Preeti Tiwari; Rajiv Chandak

    2014-01-01

    In this research work, the effect of salt water on the compressive strength of concrete was investigated. This paper therefore presents the result and findings of an experimental research on the effect of salt water on compressive strength of concrete. For this concrete cubes were cast using fresh wi and salt water for a design mix of M-30 1:1.8:3.31 by weight of concrete, and 0.45 water- cement ratio. Half of concrete cubes were cast and cured with fresh water and remaining ha...

  10. Goose`s eggshell strength at compressive loading

    Directory of Open Access Journals (Sweden)

    Šárka Nedomová

    2014-02-01

    Full Text Available The paper deals with the study of the goose eggs behaviour under compressive loading between two plates using testing device TIRATEST. The influences of the loading orientation as well as the effect of compressive velocity are studied. 226 eggs from Landes geese were chosen for the experiment. Eggs have been loaded between their poles and in the equator plane. Five different compressive velocities (0.0167, 0.167, 0.334, 1.67 and 5 mm.s-1 were used. The increase in rupture force with loading rate was observed for loading in all direction (along main axes. Dependence of the rupture force on loading rate was quantifies and described. The highest rupture force was obtained when the eggs were loaded along their axes of symmetry (X-axis. Compression in the equator plane (along the Z-axis required the least compressive force to break the eggshells. The eggshell strength was described by the rupture force, specific rupture deformation and by the absorbed energy. The rupture force is highly dependent on compression speeds. The dependence of the rupture force on the compression velocity can be described by a power function. The same is valid for the rate dependence of the energy absorbed by the egg up to the fracture. The rate sensitivity of the Goose's eggshells strength is significantly higher than that reported for the hen's eggs

  11. Changes in Mineralogy, Microstructure, Compressive Strength and Intrinsic Permeability of Two Sedimentary Rocks Subjected to High-Temperature Heating

    Science.gov (United States)

    Liu, Xianfeng; Yuan, Shengyang; Sieffert, Yannick; Fityus, Stephen; Buzzi, Olivier

    2016-08-01

    This study falls in the context of underground coal fires where burning coal can elevate the temperature of a rock mass in excess of 1000°. The objective of the research is to experimentally characterize the change in mechanical behaviour, mineralogy and microstructural texture of two sedimentary rocks when subjected to temperatures up to 1200 °C for 24 h. Specimens of local sandstone and mudstone were comprehensively characterized by X-ray diffraction and thermal-gravimetric analysis. These analyses were complemented by optical microscopy and scanning electron microscopy on polished thin sections. In addition, pore size distributions of these heated rocks were inferred by means of mercury intrusion porosimetry. These results were extended to an estimation of the intrinsic permeability using the Katz-Thompson model. Investigations at micro scale were followed by mechanical testing (both unconfined and confined compression tests) on cylindrical specimens of heated rocks. Results show that the unconfined compressive strength (UCS) of both rock types tends to increase when the temperatures increases up to 900 °C, beyond which the UCS tends to slightly decrease. As for the permeability, a clear increase in intrinsic permeability was observed for both rocks. The macroscopic behaviour was found to be fully consistent with the changes observed at micro scale.

  12. Effect of thickness of bonded composite resin on compressive strength

    NARCIS (Netherlands)

    Hamburger, J.T.; Opdam, N.J.; Bronkhorst, E.M.; Roeters, J.; Huysmans, M.C.

    2014-01-01

    OBJECTIVE: The aim of this study was to investigate the compressive strength of composites with different physical properties bonded as a restoration to dentin in layers of varying thicknesses. METHODS: Four types of direct composite materials: a midway-filled (Tetric EvoCeram); a compact-filled (Cl

  13. Evaluation of Concrete Compressive Strength by incorporating Used Foundry Sand

    Directory of Open Access Journals (Sweden)

    Khuram Rashid

    2016-07-01

    Full Text Available The main objective of this study was to evaluate the compressive strength of concrete by utilizing three types of used foundry sand; with bentonite clay, with sodium silicate & with phenolic resin as partial replacement of fine aggregates. To accomplish the research an experimental program was conducted in which ten concrete mixtures were casted, by keeping all other parameters for concrete proportioning as constant and only change made was in the amount of fine aggregates. Ten, Twenty and Thirty percent replacement level of river sand by used foundry sands was maintained in this study. All fine aggregates were selected after achieving desired physical and chemical tests. Work ability, compressive strength and modulus of elasticity were measured and compared with the conventional concrete termed as control mixture. It was observed that work ability increased with replacement levels. The cubes were crushed at 7, 28 and 63 days of standard moist curing. The compressive strength of all concrete specimens increased with increase in curing age. With exception to foundry sand with phenolic resin, compressive strength of concrete mixtures was decreased with increase in replacement level at all ages. Similar trends were observed in modulus of elasticity of concrete.

  14. Unfired clay bricks – moisture properties and compressive strength

    DEFF Research Database (Denmark)

    Hansen, E.J. de Place; Hansen, Kurt Kielsgaard

    2002-01-01

    Apparatus, methods and test results from an experimental investigation of (1) the properties for moisture performance of the materials, including water vapour sorption and water vapour transmission, (2) humidity buffering of the indoor climate by an absorbent material, and (3) the compressive str...... strength are presented....

  15. Forecast Jointed Rock Mass Compressive Strength Using a Numerical Model

    Directory of Open Access Journals (Sweden)

    Protosenya Anatoliy

    2016-01-01

    Full Text Available The method of forecasting the strength of the jointed rock mass by numerical modeling of finite element method in ABAQUS was described. The paper presents advantages of this method to solve the problem of determining the mechanical characteristics of jointed rock mass and the basic steps of creating a numerical geomechanical model of jointed rock mass and numerical experiment. Numerical simulation was carried out with jointed rock mass in order to obtain the ratio of strain and stress while loading the numerical model, determining parameters of quantitative assessment of the impact of the discontinuities orientation on the value of the compressive strength, compressive strength anisotropy. The results of the numerical experiment are compared with the data of experimental studies investigations. Innovative materials and structures are analyzed in this paper. The results that were obtained by calculation show qualitative agreement with the results of laboratory experiments of jointed rock mass.

  16. Analysis of Homogel Uniaxial Compression Strength on Bio Grouting Material

    Directory of Open Access Journals (Sweden)

    Kyungho Park

    2016-03-01

    Full Text Available This study analyzed uniaxial compression strength over time by preparing a homogel specimen from a bio grouting material, a cement-like form produced by environment-friendly microbial reactions. Among chemical grouting methods, the most commonly used method is the Labile Waterglass method. In this study, the homogel uniaxial compressive strength of Labile Waterglass (LW injection material and that of bio grouting material were measured and analyzed. In order to perform the experiment, a total of 10 types of grouting mixing ratios were prepared by a combination of different materials such as Ordinary Portland Cement, Micro Cement, Bio Grouting Material and Sodium Silicate. They were cured in the air, and their homogel uniaxial compression strengths were measured on days 1, 3, 7 and 28 Based on the test results, it was confirmed that the uniaxial strength of the specimen made with Bio Grouting Material, Ordinary Portland Cement and Micro Cement was increased by more than 30% than that of the specimen only used with Ordinary Portland Cement, as a result of hydrogen-released heat reaction between calcium carbonate, the main ingredient of the bio grouting material, and calcium silicate in the cement. This indicates that the use of 30% bio-grouting material instead of cement in the grouting can be a reasonable mixing ratio to save the use of cement, leading to reduction in CO2 emission.

  17. Optimization of compressive strength of zirconia based dental composites

    Indian Academy of Sciences (India)

    U V Hambire; V K Tripathi

    2014-10-01

    Dental composites are tooth-coloured restorative material used by dentists for various applications. Restoration of a lost tooth structure requires a material having mechanical as well as aesthetic properties similar to that of tooth. This poses challenges to engineers and the dentist alike. Dental composites consist of a matrix and a dispersed phase called filler, which are mainly responsible for its mechanical properties. Most commonly used matrix is bisphenol glycidyl methacrylate (Bis-GMA) and triethylene glycol dimethacrylate (TEGMA). Silica and glass are conventional fillers used in the past. Recently, zirconia is being used due to its improved mechanical properties. A study was conducted to evaluate the contribution of zirconia to the mechanical properties in general and compressive strength in particular. We have attempted to make an experimental dental composite with a conglomerate of nanofillers, namely, zirconia, glass and silica, and optimize this filler volume percentage and obtain an optimum compressive strength for the experimental dental composite.

  18. Estimating compressive strength of concrete by mortar testing

    OpenAIRE

    Camões, Aires; Aguiar, J. L. Barroso de; Jalali, Said

    2005-01-01

    Concrete mix design laboratory tests which time consuming and entails considerable effort. This study presents a method of reducing mix design testing costs by testing mortar instead of concrete specimens. The experimental programme consisted of defining mortar mixes equivalent to concrete mixes, moulding specimens of both mortar and concrete mixes studied and finally evaluating the compressive strength of specimens cured at different curing time. Results obtained indicate that a goo...

  19. Effect of aluminum oxide on the compressive strength of pellets

    Institute of Scientific and Technical Information of China (English)

    Jian-liang Zhang; Zhen-yang Wang; Xiang-dong Xing; Zheng-jian Liu

    2014-01-01

    Analytical-reagent-grade Al2O3 was added to magnetite ore during the process of pelletizing, and the methods of mercury intru-sion, scanning electron microscopy, and image processing were used to investigate the effect of Al2O3 on the compressive strength of the pellets. The results showed that, as the Al2O3 content increased, the compressive strength of the pellets increased slightly and then decreased gradually. When a small amount of Al2O3 was added to the pellets, the Al2O3 combined with fayalite (2FeO·SiO2) and the aluminosilicate (2FeO·2Al2O3·5SiO2) was generated, which releases some iron oxide and reduces the inhibition of fayalite to the solid phase of consolidation. When Al2O3 increased sequentially, high melting point of Al2O3 particles hinder the oxidation of Fe3O4 and the recrystallization of Fe2O3, making the internal porosity of the pellets increase, which leads to the decrease in compressive strength of the pellets.

  20. Toroidal, compression, and vortical dipole strengths in 124Sn

    CERN Document Server

    Kvasil, J; Repko, A; Kleinig, W; Reinhard, P -G; Iudice, N Lo

    2012-01-01

    The toroidal, compression and vortical dipole strength functions in semi-magic $^{124}$Sn (and partly in doubly-magic $^{100,132}$Sn) are analyzed within the random-phase-approximation method with the SkT6, SkI3, SLy6, SV-bas, and SkM* Skyrme forces. The isoscalar (T=0), isovector (T=1), and electromagnetic ('elm') channels are considered. Both convection $j_c$ and magnetization $j_m$ nuclear currents are taken into account. The calculations basically confirm the previous results obtained for $^{208}$Pb with the force SLy6. In particular, it is shown that the vortical and toroidal strengths are dominated by $j_c$ in T=0 channel and by $j_m$ in T=1 and 'elm' channels. The compression strength is always determined by $j_c$. It is also shown that the 'elm' strength (relevant for (e,e') reaction) is very similar to T=1 one. The toroidal mode resides in the region of the pygmy resonance. So, perhaps, this region embraces both irrotational (pygmy) and vortical (toroidal) flows.

  1. Compressive Strength Development and Microstrueture of Cement.asphalt Mortar

    Institute of Scientific and Technical Information of China (English)

    WANG Qiang; YAN Peiyu; KONG Xiangming; YANG Jinbo

    2011-01-01

    The compressive strength developing process and the microstructure of cement-asphalt mortar (CA mortar) were investigated.The fluidity of CA mortar has a great influence on its strength.The optimum value of spread diameter of slump flow test is in the range of 300 to 400 mm.The compressive strength of CA mortar keeps a relatively high growth rate in 56 days and grows slowly afterwards.The residual water of hydration in CA mortar freezes under minus environmental temperature which can lead to a significant reduction of the strength of CA mortar.Increasing A/C retards asphalt emulsion splitting and thus prolongs the setting process of CA mortar.The hydration products of cement form the major structural framework of hardened CA mortar and asphalt is a weak phase in the framework but improves the viscoelastic behavior of CA mortar.Therefore,asphalt emulsion should be used as much as possible on the condition that essential performance criterions of CA mortar are satisfied.

  2. Scaling of compression strength in disordered solids: metallic foams

    Directory of Open Access Journals (Sweden)

    J. Kováčik

    2016-03-01

    Full Text Available The scaling of compression strength with porosity for aluminium foams was investigated. The Al 99.96, AlMg1Si0.6 and AlSi11Mg0.6 foams of various porosity, sample size with and without surface skin were tested in compression. It was observed that the compression strength of aluminium foams scales near the percolation threshold with Tf ≈ 1.9 - 2.0 almost independently on the matrix alloy, sample size and presence of surface skin. The difference of the obtained values of Tf to the theoretical estimate of Tf = 2.64 ± 0.3 by Arbabi and Sahimi and to Ashby estimate of 1.5 was explained using an analogy with the Daoud and Coniglio approach to the scaling of the free energy of sol-gel transition. It leads to the finding that, there are two different universality classes for the critical exponent Tf: when the stretching forces dominate Tf = f = 2.1, respectively when bending forces prevail Tf = .d = 2.64 seems to be valid. Another possibility is the validity of relation Tf ≤ f which varies only according to the universality class of modulus of elasticity in foam.

  3. Size effect on cubic and prismatic compressive strength of cement paste

    Institute of Scientific and Technical Information of China (English)

    苏捷; 叶缙垚; 方志; 赵明华

    2015-01-01

    A series of compression tests were conducted on 150 groups of cement paste specimens with side lengths ranging from 40 mm to 200 mm. The specimens include cube specimens and prism specimens with height to width ratio of 2. The experiment results show that size effect exists in the cubic compressive strength and prismatic compressive strength of the cement paste, and larger specimens resist less in terms of strength than smaller ones. The cubic compressive strength and the prismatic compressive strength of the specimens with side length of 200 mm are respectively about 91% and 89% of the compressive strength of the specimens with the side length of 40 mm. Water to binder ratio has a significant influence on the size effect of the compressive strengths of the cement paste. With a decrease in the water to binder ratio, the size effect is significantly enhanced. When the water to binder ratio is 0.2, the size effects of the cubic compressive strength and the prismatic compressive strength of the cement paste are 1.6 and 1.4 times stronger than those of a water to binder ratio of 0.6. Furthermore, a series of formulas are proposed to calculate the size effect of the cubic compressive strength and the prismatic compressive strength of cement paste, and the results of the size effect predicted by the formulas are in good agreement with the experiment results.

  4. Effect of Banana Fibers on the Compressive and Flexural Strength of Compressed Earth Blocks

    Directory of Open Access Journals (Sweden)

    Marwan Mostafa

    2015-03-01

    Full Text Available Sustainable development of the built environment in developing countries is a major challenge in the 21st century. The use of local materials in construction of buildings is one of the potential ways to support sustainable development in both urban and rural areas. Building with Compressed Earthen Blocks (CEBs is becoming more popular due to their low cost and relative abundance of materials. The proposed Green-Compressed Earth Block (GCEB consists of ordinary CEB ingredients plus Banana fibers, which will be the focus of this study. Banana fibers are widely available worldwide as agricultural waste from Banana cultivation. Banana fibers are environmentally friendly and present important attributes, such as low density, light weight, low cost, high tensile strength, as well as being water and fire resistant. This kind of waste has a greater chance of being utilized for different application in construction and building materials. This focused on the use of banana fiber and its effect on the compressive and flexural strength in CEB. The deflection at the mid-span of the blocks studied was calculated using the Linear Variable Differential Transformer (LVDT. The results of this study will highlight general trends in the strength properties of different soil mixes for CEBs. These efforts are necessary to ensure that GCEB technology becomes more widely accepted in the world of building materials and is considered a reliable option for providing low-cost housing.

  5. Compressive strength and hydrolytic stability of fly ash based geopolymers

    Directory of Open Access Journals (Sweden)

    Nikolić Irena

    2013-01-01

    Full Text Available The process of geopolymerization involves the reaction of solid aluminosilicate materials with highly alkaline silicate solution yielding an aluminosilicate inorganic polymer named geopolymer, which may be successfully applied in civil engineering as a replacement for cement. In this paper we have investigated the influence of synthesis parameters: solid to liquid ratio, NaOH concentration and the ratio of Na2SiO3/NaOH, on the mechanical properties and hydrolytic stability of fly ash based geopolymers in distilled water, sea water and simulated acid rain. The highest value of compressive strength was obtained using 10 mol dm-3 NaOH and at the Na2SiO3/NaOH ratio of 1.5. Moreover, the results have shown that mechanical properties of fly ash based geopolymers are in correlation with their hydrolytic stability. Factors that increase the compressive strength also increase the hydrolytic stability of fly ash based geopolymers. The best hydrolytic stability of fly ash based geopolymers was shown in sea water while the lowest stability was recorded in simulated acid rain. [Projekat Ministarstva nauke Republike Srbije, br. 172054 i Nanotechnology and Functional Materials Center, funded by the European FP7 project No. 245916

  6. Permeability, porosity and compressive strength of self-compacting concrete

    Directory of Open Access Journals (Sweden)

    Valcuende, M.O.

    2005-12-01

    Full Text Available Most deterioration affecting the durability of self-compacting concrete structures is mediated by water penetration in the concrete, a condition related to its porous structure. The present study analyzes these two factors. To this end, two types of concrete were prepared, a self-compacting and a traditional vibrated concrete, with different W/C ratios and different types of cement. The results of low-pressure water testing to evaluate permeability and analyses to determine compressive strength and pore size distribution showed that self-compacting concrete has lower capillary porosity than traditional concrete, which would explain its greater resistance to water penetration. Such concrete likewise reached higher strength values, except where large proportions of lime powder with low sand equivalents were used in its manufacture, when lower strength was recorded. Lastly, the depth of water penetration and compressive strength were found to be linearly correlated. That correlation was seen to depend, in turn, on the type of concrete, since for any given strength level, self-compacting concrete was less permeable than the traditional material.

    En este trabajo experimental se estudia la penetración de agua en hormigones autocompactables, analizando al mismo tiempo su estructura porosa, pues gran parte de los procesos de deterioro que afectan a la durabilidad de las estructuras están condicionados por estos dos aspectos. Para ello se han fabricado dos tipos de hormigones, uno autocompactable y otro tradicional vibrado, con diferentes relaciones A/C y distintos tipos de cemento. Tras determinar la permeabilidad al agua bajo presión, la resistencia a compresión y las distribuciones de tamaño de poro, los resultados obtenidos ponen de manifiesto que los hormigones autocompactables presentan menor porosidad capilar que los tradicionales, lo que les confiere mejores prestaciones frente a la penetración de agua. Asimismo, dichos hormigones

  7. Modeling of Compressive Strength for Self-Consolidating High-Strength Concrete Incorporating Palm Oil Fuel Ash

    Directory of Open Access Journals (Sweden)

    Md. Safiuddin

    2016-05-01

    Full Text Available Modeling is a very useful method for the performance prediction of concrete. Most of the models available in literature are related to the compressive strength because it is a major mechanical property used in concrete design. Many attempts were taken to develop suitable mathematical models for the prediction of compressive strength of different concretes, but not for self-consolidating high-strength concrete (SCHSC containing palm oil fuel ash (POFA. The present study has used artificial neural networks (ANN to predict the compressive strength of SCHSC incorporating POFA. The ANN model has been developed and validated in this research using the mix proportioning and experimental strength data of 20 different SCHSC mixes. Seventy percent (70% of the data were used to carry out the training of the ANN model. The remaining 30% of the data were used for testing the model. The training of the ANN model was stopped when the root mean square error (RMSE and the percentage of good patterns was 0.001 and ≈100%, respectively. The predicted compressive strength values obtained from the trained ANN model were much closer to the experimental values of compressive strength. The coefficient of determination (R2 for the relationship between the predicted and experimental compressive strengths was 0.9486, which shows the higher degree of accuracy of the network pattern. Furthermore, the predicted compressive strength was found very close to the experimental compressive strength during the testing process of the ANN model. The absolute and percentage relative errors in the testing process were significantly low with a mean value of 1.74 MPa and 3.13%, respectively, which indicated that the compressive strength of SCHSC including POFA can be efficiently predicted by the ANN.

  8. Diametral Compressive Strength and Elastic Modulus of Flattened Disc using Diametral Compressive Test

    International Nuclear Information System (INIS)

    The nuclear grade graphite is the candidate materials for the in-core components of the very high temperature gas-cooled tractor (VHTR) due to its very high conductivity, melting temperature, chemical resistance and mechanical stability. Nuclear graphite undergoes dimensional change and mechanical properties change because of irradiation damage. To estimate the irradiation damage, surveillance capsule would be inserted in reactor. Surveillance capsule sizes were limited because it would be located inside of a reactor vessel. Thus, a new test method using small specimen is needed and diametral compressive test is one of them. However, circular anvils are needed according to the specimen size. A flattened disc specimen were proposed to overcome such a problem and applied for determination of mechanical properties for brittle rocks. In this study, the applicability of such specimen was investigated. In addition, minimum specimen size for test was determined and diametral compressive strength of nuclear graphite was measured

  9. Compressive strength after blast of sandwich composite materials.

    Science.gov (United States)

    Arora, H; Kelly, M; Worley, A; Del Linz, P; Fergusson, A; Hooper, P A; Dear, J P

    2014-05-13

    Composite sandwich materials have yet to be widely adopted in the construction of naval vessels despite their excellent strength-to-weight ratio and low radar return. One barrier to their wider use is our limited understanding of their performance when subjected to air blast. This paper focuses on this problem and specifically the strength remaining after damage caused during an explosion. Carbon-fibre-reinforced polymer (CFRP) composite skins on a styrene-acrylonitrile (SAN) polymer closed-cell foam core are the primary composite system evaluated. Glass-fibre-reinforced polymer (GFRP) composite skins were also included for comparison in a comparable sandwich configuration. Full-scale blast experiments were conducted, where 1.6×1.3 m sized panels were subjected to blast of a Hopkinson-Cranz scaled distance of 3.02 m kg(-1/3), 100 kg TNT equivalent at a stand-off distance of 14 m. This explosive blast represents a surface blast threat, where the shockwave propagates in air towards the naval vessel. Hopkinson was the first to investigate the characteristics of this explosive air-blast pulse (Hopkinson 1948 Proc. R. Soc. Lond. A 89, 411-413 (doi:10.1098/rspa.1914.0008)). Further analysis is provided on the performance of the CFRP sandwich panel relative to the GFRP sandwich panel when subjected to blast loading through use of high-speed speckle strain mapping. After the blast events, the residual compressive load-bearing capacity is investigated experimentally, using appropriate loading conditions that an in-service vessel may have to sustain. Residual strength testing is well established for post-impact ballistic assessment, but there has been less research performed on the residual strength of sandwich composites after blast. PMID:24711494

  10. Influence of pore structure on compressive strength of cement mortar.

    Science.gov (United States)

    Zhao, Haitao; Xiao, Qi; Huang, Donghui; Zhang, Shiping

    2014-01-01

    This paper describes an experimental investigation into the pore structure of cement mortar using mercury porosimeter. Ordinary Portland cement, manufactured sand, and natural sand were used. The porosity of the manufactured sand mortar is higher than that of natural sand at the same mix proportion; on the contrary, the probable pore size and threshold radius of manufactured sand mortar are finer. Besides, the probable pore size and threshold radius increased with increasing water to cement ratio and sand to cement ratio. In addition, the existing models of pore size distribution of cement-based materials have been reviewed and compared with test results in this paper. Finally, the extended Bhattacharjee model was built to examine the relationship between compressive strength and pore structure.

  11. Influence of pore structure on compressive strength of cement mortar.

    Science.gov (United States)

    Zhao, Haitao; Xiao, Qi; Huang, Donghui; Zhang, Shiping

    2014-01-01

    This paper describes an experimental investigation into the pore structure of cement mortar using mercury porosimeter. Ordinary Portland cement, manufactured sand, and natural sand were used. The porosity of the manufactured sand mortar is higher than that of natural sand at the same mix proportion; on the contrary, the probable pore size and threshold radius of manufactured sand mortar are finer. Besides, the probable pore size and threshold radius increased with increasing water to cement ratio and sand to cement ratio. In addition, the existing models of pore size distribution of cement-based materials have been reviewed and compared with test results in this paper. Finally, the extended Bhattacharjee model was built to examine the relationship between compressive strength and pore structure. PMID:24757414

  12. Influence of Pore Structure on Compressive Strength of Cement Mortar

    Directory of Open Access Journals (Sweden)

    Haitao Zhao

    2014-01-01

    Full Text Available This paper describes an experimental investigation into the pore structure of cement mortar using mercury porosimeter. Ordinary Portland cement, manufactured sand, and natural sand were used. The porosity of the manufactured sand mortar is higher than that of natural sand at the same mix proportion; on the contrary, the probable pore size and threshold radius of manufactured sand mortar are finer. Besides, the probable pore size and threshold radius increased with increasing water to cement ratio and sand to cement ratio. In addition, the existing models of pore size distribution of cement-based materials have been reviewed and compared with test results in this paper. Finally, the extended Bhattacharjee model was built to examine the relationship between compressive strength and pore structure.

  13. Experimental Study of Confined Low-, Medium- and High-Strength Concrete Subjected to Concentric Compression

    OpenAIRE

    Antonius; Iswandi Imran

    2012-01-01

    An experimental study of 23 low-, medium- and high-strength concrete columns is presented in this paper. Square-confined concrete columns without longitudinal reinforcement were designed, and tested under concentric axial compression. The columns were made of concrete with a compressive strength ranging between 30 MPa and 70 MPa. The test parameters in the study are concrete compressive strengths and confining steel properties, i.e. spacing, volumetric ratios and configurations. The effects o...

  14. Effect of Curing Temperature Histories on the Compressive Strength Development of High-Strength Concrete

    Directory of Open Access Journals (Sweden)

    Keun-Hyeok Yang

    2015-01-01

    Full Text Available This study examined the relative strength-maturity relationship of high-strength concrete (HSC specifically developed for nuclear facility structures while considering the economic efficiency and durability of the concrete. Two types of mixture proportions with water-to-binder ratios of 0.4 and 0.28 were tested under different temperature histories including (1 isothermal curing conditions of 5°C, 20°C, and 40°C and (2 terraced temperature histories of 20°C for an initial age of individual 1, 3, or 7 days and a constant temperature of 5°C for the subsequent ages. On the basis of the test results, the traditional maturity function of an equivalent age was modified to consider the offset maturity and the insignificance of subsequent curing temperature after an age of 3 days on later strength of concrete. To determine the key parameters in the maturity function, the setting behavior, apparent activation energy, and rate constant of the prepared mixtures were also measured. This study reveals that the compressive strength development of HSC cured at the reference temperature for an early age of 3 days is insignificantly affected by the subsequent curing temperature histories. The proposed maturity approach with the modified equivalent age accurately predicts the strength development of HSC.

  15. Numerical analysis of the spacer grids' compression strength

    International Nuclear Information System (INIS)

    Among the components of the fuel assembly, the spacer grids play an important structural role during the energy generation process, mainly for their requirement to have enough structural strength to withstand lateral impact loads, due to fuel assembly shipping/handling and due to forces outcome from postulated accidents (earthquake and LOCA). This requirement ensures a proper geometry for cooling and for guide thimble straightness in the fuel assembly. In this way, the understanding of the macroscopic mechanical behavior of this component becomes essential even to any subsequent geometrical modifications to optimize the flue assemblies' structural behavior. In the present work, three-dimensional finite element models destined to provide consistent predictions of 16X16-type spacer grids lateral strength were proposed. Firstly, buckling tests based on results available in the literature were performed to establish a methodology for spacer grid finite element-based modeling. The, by considering a spacer grid interesting geometry and some possible variations associated to its fabrication, tolerance, the proposed numerical models were submitted to compression conditions to calculate the buckling force. Also, these models were validated for comparison with experimental buckling load results. Comparison of buckling predictions combined to observations of actual and simulated deformed spacer grids geometries permitted to verify the consistency and applicability of the proposed models. Thus, these numerical results show a good agreement between the and the experimental results. (author)

  16. Compressive impact strength of high temperature gas-cooled reactor graphite

    International Nuclear Information System (INIS)

    To investigate the effect of strain rate on fracture behavior for coarse grained nuclear graphite, PGX, a hydraulic servo type impact testing machine has been constructed and compressive impact strength test was performed at various strain up to more than 100(1/s). From the results, the following conclusions were derived. (1) Compressive impact strength of graphite increases with increasing of strain rate in the range of 10-3 to 100(1/s). (2) Compressive impact strength decreases drastically for strain rates more than 100(1/s). (3) Compressive impact strength dose not depend on specimen volume. (author)

  17. Mechanical properties of Concrete with SAP. Part I: Development of compressive strength

    DEFF Research Database (Denmark)

    Hasholt, Marianne Tange; Jespersen, Morten H. Seneka; Jensen, Ole Mejlhede

    2010-01-01

    The development of mechanical properties has been studied in a test program comprising 15 different concrete mixes with 3 different w/c ratios and different additions of superabsorbent polymers (SAP). The degree of hydration is followed for 15 corresponding paste mixes. This paper concerns...... compressive strength. It shows that results agree well with a model based on the following: 1. Concrete compressive strength is proportional to compressive strength of the paste phase 2. Paste strength depends on gel space ratio, as suggested by Powers 3. The influence of air voids created by SAP...... on compressive strength can be accounted for in the same way as when taking the air content into account in Bolomeys formula. The implication of the model is that at low w/c ratios (w/c SAP additions, SAP increases the compressive strength at later ages (from 3 days after casting and onwards...

  18. Effect of size and shape of specimen on compressive strength of glass fiber reinforced concrete (GFRC

    Directory of Open Access Journals (Sweden)

    Krishna Rao M.V.

    2011-01-01

    Full Text Available Concrete is a versatile material with tremendous applications in civil engineering construction. Structural concrete elements are generally made with concrete having a compressive strength of 20 to 35 MPa. Lately, there is an increase in use of high strength concrete (HSC in major construction projects such as high-rise buildings, and bridges involving members of different sizes and shapes. The compressive strength of concrete is used as the most basic and important material property in the design of reinforced concrete structures. It has become a problem to use this value as the control specimen sizes and shapes are different from country to country. In India, the characteristic compressive strength is usually measured based on 150 mm cubes [1]. But, the ACI code of practice specifies the design compressive strength based on the standard 150x300 mm cylinders [2]. The use of 100x200 mm cylinders gained more acceptance as the need to test high strength concrete increases [3]. In this context the size and shape of concrete becomes an important parameter for the compressive strength. In view of the significance of compressive strength of concrete and due to the fact that the structural elements of different sizes and shapes are used, it is proposed to investigate the effect of size and shape of the specimen on the compressive strength of concrete. In this work, specimens of plain as well as Glass Fiber Reinforced Concrete (GFRC specimens are cast in order to carry out a comparative study.

  19. EFFECT OF DAMAGE ON COMPRESSIVE STRENGTH IN FIBER DIRECTION FOR CFRP

    OpenAIRE

    Eyer, G; Montagnier, O; Hochard, C; Charles, J-P; Mazerolle, F

    2015-01-01

    The influence of transverse damage on compressive strength in fiber direction for carbon fiber reinforced epoxy materials is investigated by an experimental approach. Several experimental methods are proposed. The first study focuses on tubular samples. Theses samples are damaged by torsional and cyclic load and next submitted to compressive load. Results show that the transverse damage affects the compressive strength. Yet the stiffness is not modified. A model is then proposed with these re...

  20. Filler effect of fine particle sand on the compressive strength of mortar

    Science.gov (United States)

    Jaturapitakkul, Chai; Tangpagasit, Jatuphon; Songmue, Sawang; Kiattikomol, Kraiwood

    2011-04-01

    The river sand, which is a non-pozzolanic material, was ground into 3 different particle sizes. Portland cement type I was replaced by the ground river sands at 10wt%-40wt% of binder to cast mortar. Compressive strengths of mortar were investigated and the filler effect of different fine particles of sand on the compressive strength of mortar was evaluated. The results show that the compressive strength of mortar contributed from the filler effect of smaller particles is higher than that of the coarser ones. The difference in compressive strength of mortar tends to be greater as the difference in ground river sand fineness increases. The results also suggest that ASTM C618 specification is not practically suitable for specifying pozzolan in concrete since the strength activity index of mortar containing ground river sand (high crystalline phase) with 33.8wt% of particles retained on a 45-μm sieve can pass the strength requirement.

  1. Early Age Compressive Strength of Pastes by Electrical Resistivity Method and Maturity Method

    Institute of Scientific and Technical Information of China (English)

    XIAO Lianzhen; WEI Xiaosheng

    2011-01-01

    The compressive strength development of Portland cement pastes was investigated by the electrical resistivity method and the maturity method.The experiments were carried out on the cement pastes with different water-cement ratios at different curing temperatures.The results show that the application of the maturity method has limitation to obtain the strength.It is found that both of the compressive strength and the electrical resistivity follow hyperbolic trend for all the mixes.The hyperbolic equation of each mix is obtained to estimate the ultimate resistivity value which can probably be reached.The relationship between electrical resistivity and compressive strength of the cement pastes is established based on the test results and interpreted by the empirical Archie equation and a strength-porosity equation.The relationship between the electrical resistivity after temperature correction and the compressive strength was linear and independent of curing temperature and water-cement ratio.

  2. Relation between Modulus of Elasticity and Compressive Strength of Ultrahigh-Strength Mortar with Mixed Silicon Carbide as Fine Aggregate

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Ultrahigh-strength mortar mixed surface-oxidized silicon carbide as a fine aggregate was prepared by means of press-casting followed by curing in an autoclave. The relation between modulus of elasticity up to 111 GPa and compressive strength up to 360 MPa of mortar mixed silicon carbide was discussed and it was revealed that the contributions of the aggregate hardness and of the interfacial strength between the aggregate and the cement paste on the elasticity of mortar were imporant.

  3. Fracture Energy of High-Strength Concrete in Compression

    DEFF Research Database (Denmark)

    Dahl, H.; Brincker, Rune

    1989-01-01

    is essential for understanding the fracture mechanism of concrete in compression. In this paper a series of tests is reported, carried out for the purpose of studying the fracture mechanical properties of concrete in compression. Including the measurement and study of the descending branch, a new...

  4. Effect of Specimen Shape and Size on the Compressive Strength of Foamed Concrete

    Directory of Open Access Journals (Sweden)

    Sudin M.A.S.

    2014-03-01

    Full Text Available Lightweight concrete, in the form of foamed concrete, is a versatile material that primarily consists of a cement based mortar, mixed with at least 20% volume of air. Its dry density is typically below 1600 kg/m3 with a maximum compressive strength of 15MPa. The ASTM standard provision specifies a correction factor for concrete strength of between 14 and 42Mpa, in order to compensate for a reduced strength, when the aspect height-to-diameter ratio of a specimen is less than 2.0. However, the CEB-FIP provision specifically mentions a ratio of 150mm dia. × 300mm cylinder strength to 150 mm cube strength; though, both provision requirements do not specifically clarify the applicability and/or modification of the correction factors for the compressive strength to lightweight concrete (in this case, foamed concrete. The focus of this work is to study the effect of specimen size and shape on the axial compressive strength of concrete. Specimens of various sizes and shapes were cast with square and circular cross-sections i.e., cubes, prisms, and cylinders. Their compression strength behaviours at 7 and 28 days were investigated. The results indicate that, as the CEB-FIP provision specified, even for foamed concrete, 100mm cubes (l/d = 1.0 produce a comparable compressive strength with 100mm dia. × 200mm cylinders (l/d = 2.0.

  5. The Influence of Mineral Admixtures on Bending Strength of Mortar on the Premise of Equal Compressive Strength

    Institute of Scientific and Technical Information of China (English)

    WANG Qiang; YAN Peiyu; FENG Jianwen

    2012-01-01

    The influence of mineral admixtures on bending strength of mortar on the premise of equal compressive strength was investigated.Three mineral admixtures (fly ash,ground granulated blast-furnace slag and steel slag) were used.The adding amount of mineral admixture in this study ranges from 22.5% to 60%,and the water-to-binder ratio ranges from 0.34 to 0.50.With equal compressive strength,different mortars can be arranged in such a descending order with their bending strength:cement-fly ash mortar,cement mortar,cement-GGBS mortar,and cement-steel slag mortar.With the same compressive strength,the higher the steel slag content and water-to-binder ratio,the lower the bending strength of mortars.However,the effect of mineral mixture content and water-to-binder ratio on the bending strength of cement-fly ash mortar and cement-GGBS mortar is far inconspicuous.

  6. FACTORS INFLUENCING THE COMPRESSIVE STRENGTH OF FLY ASH-BASED GEOPOLYMER CONCRETE

    Directory of Open Access Journals (Sweden)

    Djwantoro Hardjito

    2004-01-01

    Full Text Available This paper describes the effects of several factors on the properties of fly ash based geopolymer concrete, especially the compressive strength. The test variables included were the age of concrete, curing time, curing temperature, quantity of superplasticizer, the rest period prior to curing, and the water content of the mix. The test results show that the compressive strength of geopolymer concrete does not vary with age, and curing the concrete specimens at higher temperature and longer curing period will result in higher compressive strength. Furthermore, the commercially available Naphthalene-based superplasticizer improves the workability of fresh geopolymer concrete. The start of curing of geopolymer concrete at elevated temperatures can be delayed at least up to 60 minutes without significant effect on the compressive strength. The test data also show that the water content in the concrete mix plays an important role.

  7. Compressive Strength, Chloride Permeability, and Freeze-Thaw Resistance of MWNT Concretes under Different Chemical Treatments

    Directory of Open Access Journals (Sweden)

    Xingang Wang

    2014-01-01

    Full Text Available This study investigated compressive strength, chloride penetration, and freeze-thaw resistance of multiwalled carbon nanotube (MWNT concrete. More than 100 cylindrical specimens were used to assess test variables during sensitivity observations, including water-cement ratios (0.75, 0.5, and 0.4 and exposure to chemical agents (including gum arabic, propanol, ethanol, sodium polyacrylate, methylcellulose, sodium dodecyl sulfate, and silane. To determine the adequate sonication time for MWNT dispersal in water, the compressive strengths of MWNT concrete cylinders were measured after sonication times ranging from 2 to 24 minutes. The results demonstrated that the addition of MWNT can increase the compressive strength of concrete by up to 108%. However, without chemical treatment, MWNT concretes tend to have poor freeze-thaw resistance. Among the different chemical treatments, MWNT concrete treated with sodium polyacrylate has the best compressive strength, chloride resistance, and freeze-thaw durability.

  8. Compressive strength, chloride permeability, and freeze-thaw resistance of MWNT concretes under different chemical treatments.

    Science.gov (United States)

    Wang, Xingang; Rhee, Inkyu; Wang, Yao; Xi, Yunping

    2014-01-01

    This study investigated compressive strength, chloride penetration, and freeze-thaw resistance of multiwalled carbon nanotube (MWNT) concrete. More than 100 cylindrical specimens were used to assess test variables during sensitivity observations, including water-cement ratios (0.75, 0.5, and 0.4) and exposure to chemical agents (including gum arabic, propanol, ethanol, sodium polyacrylate, methylcellulose, sodium dodecyl sulfate, and silane). To determine the adequate sonication time for MWNT dispersal in water, the compressive strengths of MWNT concrete cylinders were measured after sonication times ranging from 2 to 24 minutes. The results demonstrated that the addition of MWNT can increase the compressive strength of concrete by up to 108%. However, without chemical treatment, MWNT concretes tend to have poor freeze-thaw resistance. Among the different chemical treatments, MWNT concrete treated with sodium polyacrylate has the best compressive strength, chloride resistance, and freeze-thaw durability. PMID:25140336

  9. Estimation of compressive strength of fresh-concrete by using ultrasonic wave propagation velocity

    International Nuclear Information System (INIS)

    The purpose of this work is to give the correlation between ultrasonic wave propagation velocity of fresh concrete and compressive strength of concrete after a age of few days. The ultrasonic wave velocity was measured by using pulse transmission method, and the compressive strength of concrete after 3, 7, and 28 days were measured. For reducing cost, we newly made equipment of measuring the velocity. As results of experiments, regressive equations of which average reliability was about 80%, were proposed.

  10. The Fire Resistance Performance of Recycled Aggregate Concrete Columns with Different Concrete Compressive Strengths

    OpenAIRE

    Hongying Dong; Wanlin Cao; Jianhui Bian; Jianwei Zhang

    2014-01-01

    In order to ascertain the fire resistance performance of recycled aggregate concrete (RAC) components with different concrete compressive strengths, four full-scaled concrete columns were designed and tested under high temperature. Two of the four specimens were constructed by normal concrete with compressive strength ratings of C20 and C30, respectively, while the others were made from recycled coarse aggregate (RCA) concrete of C30 and C40, respectively. Identical constant axial forces were...

  11. Durability and compressive strength of blast furnace slag-based cement grout for special geotechnical applications

    OpenAIRE

    Ortega Álvarez, José Marcos; Pastor Navarro, José Luis; Albaladejo Ruiz, Arturo; Sánchez Martín, Isidro; Climent, Miguel-Ángel

    2014-01-01

    Special foundations, most prominently micropiles and soil anchors, are frequently used in construction today. In Spain, the grout for these special technical applications is generally prepared with portland cement, although the codes and standards in place stipulate only the minimum compressive strength required, with no mention of cement type. Those texts also establish a range of acceptable water:cement ratios. In the present study, durability and compressive strength in cement grout prepar...

  12. Analysis of the Optimum Usage of Slag for the Compressive Strength of Concrete

    OpenAIRE

    Han-Seung Lee; Xiao-Yong Wang; Li-Na Zhang; Kyung-Taek Koh

    2015-01-01

    Ground granulated blast furnace slag is widely used as a mineral admixture to replace partial Portland cement in the concrete industry. As the amount of slag increases, the late-age compressive strength of concrete mixtures increases. However, after an optimum point, any further increase in slag does not improve the late-age compressive strength. This optimum replacement ratio of slag is a crucial factor for its efficient use in the concrete industry. This paper proposes a numerical procedu...

  13. Identification of Bacteria and the Effect on Compressive Strength of Concrete

    OpenAIRE

    Anneza L. H.; Irwan J. M.; Othman N.; Alshalif A. Faisal

    2016-01-01

    This paper presents the species of bacteria used in this study as well as the effect of the bacteria on compressive strength of bioconcrete. Bioconcrete is not only more environmentally friendly but it is easy to procure. The objective of this research is to identify the ureolytic bacteria and sulphate reduction bacteria that have been isolated and further use the bacteria in concrete to determine the effect of bacteria on compressive strength. Identification of bacteria is conducted through ...

  14. Investigation of adding fluoroapatite nanoparticles on compressive strength and corrosion behaviour of dental amalgams

    OpenAIRE

    Fahimeh Mirlohi; Ali Doostmohammadi; Ahmad Monshi

    2012-01-01

    In recent years, there have been many efforts to improve biological and biocompatibility features of amalgam. The aim of this research was investigating the effect of adding fluoroapatite (FA) nanoparticles on compressive strength and corrosion behaviour of dental amalgam. An amalgam alloy powder was mixed with 1, 3 and 5 wt.% of FA nanoparticles to form composite powders. Compressive strength of the corresponding dental amalgam samples was measured on the first and seventh day after preparat...

  15. Determine the Compressive Strength of Calcium Silicate Bricks by Combined Nondestructive Method

    OpenAIRE

    2014-01-01

    The paper deals with the application of combined nondestructive method for assessment of compressive strength of calcium silicate bricks. In this case, it is a combination of the rebound hammer method and ultrasonic pulse method. Calibration relationships for determining compressive strength of calcium silicate bricks obtained from nondestructive parameter testing for the combined method as well as for the L-type Schmidt rebound hammer and ultrasonic pulse method are quoted here. Calibration ...

  16. Prediction of compressive strength of concrete containing fly ash using data mining techniques

    OpenAIRE

    Martins, Francisco F.; Camões, Aires

    2013-01-01

    The concrete compressive strength is the most used mechanical property in the design of concrete structures. Therefore, the use of rational models to its prediction, to simulate the effects of its different constituents and its properties can play an important role in the achievement of the safety-economy required. Models to forecast the concrete compressive strength have already been presented before by some researchers. However, the comparison of different rational models and the applicatio...

  17. Relationship between pore structure and compressive strength of concrete: Experiments and statistical modeling

    Indian Academy of Sciences (India)

    J BU; Z TIAN

    2016-03-01

    Properties of concrete are strongly dependent on its pore structure features, porosity being an important one among them. This study deals with developing an understanding of the pore structure-compressive strength relationship in concrete. Several concrete mixtures with different pore structures are proportioned and subjected to static compressive tests. The pore structure features such as porosity, pore size distribution are extracted using mercury intrusion porosimetry technique. A statistical model is developed to relate thecompressive strength to relevant pore structure features.

  18. Compression strength of a fibre composite main spar in a wind turbine blade

    DEFF Research Database (Denmark)

    Jensen, Find Mølholt

    2003-01-01

    In this report the strength of a wind turbine blade is found and compared with a full-scale test, made in the same project. Especially the postbuckling behaviour of the compression flange is studied. Different compressive failure mechanisms are discussedand the limitations in using the Finite...... Element Method. A suggestion to the further work is made....

  19. Effect of Pelletized Coconut Fibre on the Compressive Strength of Foamed Concrete

    Directory of Open Access Journals (Sweden)

    Mohd Jaini Zainorizuan

    2016-01-01

    Full Text Available Foamed concrete is a controlled low density ranging from 400kg/m3 to 1800kg/m3, and hence suitable for the construction of buildings and infrastructures. The uniqueness of foamed concrete is does not use aggregates in order to retain low density. Foamed concrete contains only cement, sand, water and foam agent. Therefore, the consumption of cement is higher in producing a good quality and strength of foamed concrete. Without the present of aggregates, the compressive strength of foamed concrete can only achieve as high as 15MPa. Therefore, this study aims to introduce the pelletized coconut fibre aggregate to reduce the consumption of cement but able to enhance the compressive strength. In the experimental study, forty-five (45 cube samples of foamed concrete with density 1600kg/m3 were prepared with different volume fractions of pelletized coconut fibre aggregate. All cube samples were tested using the compression test to obtain compressive strength. The results showed that the compressive strength of foamed concrete containing 5%, 10%, 15% and 20% of pelletized coconut fibre aggregate are 9.6MPa, 11.4MPa, 14.6MPa and 13.4MPa respectively. It is in fact higher than the controlled foamed concrete that only achieves 9MPa. It is found that the pelletized coconut fibre aggregate indicates a good potential to enhance the compressive strength of foamed concrete.

  20. Identification of Bacteria and the Effect on Compressive Strength of Concrete

    Directory of Open Access Journals (Sweden)

    Anneza L. H.

    2016-01-01

    Full Text Available This paper presents the species of bacteria used in this study as well as the effect of the bacteria on compressive strength of bioconcrete. Bioconcrete is not only more environmentally friendly but it is easy to procure. The objective of this research is to identify the ureolytic bacteria and sulphate reduction bacteria that have been isolated and further use the bacteria in concrete to determine the effect of bacteria on compressive strength. Identification of bacteria is conducted through Polymerase chain reaction (PCR method and DNA sequencing. The DNA of the bacteria was run through BLAST algorithm to determine the bacterial species.The bacteria were added into the concrete mix as a partial replacement of water. 3% of water is replaced by ureolytic bacteria and 5% of water is replaced by sulphate reduction bacteria. After running BLAST algorithm the bacteria were identified as Enterococcus faecalis (ureolytic bacteria and Bacillus sp (sulphate reduction bacteria. The result of the compressive strength for control is 36.0 Mpa. Partial replacement of 3% water by ureolytic bacteria has strength of 38.2Mpa while partial replacement of 5% of water by sulphate reduction bacteria has strength of 42.5Mpa. The significant increase of compressive strength with the addition of bacteria shows that bacteria play a significant role in the improvement of compressive strength.

  1. Effect of Silica Nanoparticles on Compressive Strength of Leaves-Waste Composite

    Science.gov (United States)

    Masturi, Masturi; Aliah, Hasniah; Aji, Mahardika Prasetya; Sagita, Adi Ardian; Bukit, Minsyahril; Sustini, Euis; Khairurrijal, Khairurrijal; Abdullah, Mikrajuddin

    2011-12-01

    The utilization of solid-waste, especially leaves-waste is one of interesting research of environmental field. One of them is making a composite using polyvinyl acetate (PVAc) polymer as binder (matrix) and silica nanoparticles as reinforcement (filler) to improve the strength of composite-produced. Those raw materials preliminary were mixed by simple mixing with varied compositions and then hot-pressed at 36 MPa and 100 °C for 20 minutes. From compressive strength test, it was found that composite with composition 7:8 of PVAc and leaves-waste had maximum compressive strength, i.e. 57.60 MPa. It was also that the enhancement of strength due to PVAc fraction (w/w) increasing is a percolation behavior, even though its mathematical explanation has not been performed. Into composition of maximum strength above, silica with average size is 74 nm then was added to improve the strength and found that at silica weight fraction of 0.79 (%w/w), the composite had optimum compressive strength, i.e. 70.5 MPa, or increased up to 22.4% of that without silica. The final compressive strength was very comparable to some building goods such as sandstones and bricks. The composite density was also measured and obtained that it was about 0.9 g/cm3 that is very close to some usual woods.

  2. Estimation of hardness and compressive strength of SP 100 aluminum powder epoxy

    Energy Technology Data Exchange (ETDEWEB)

    Han, Jeong Young [Pusan National Univ., Busan (Korea, Republic of); Kim, Myung Hun [Korea Institute of Footwear and Leather Technology, Busan (Korea, Republic of); Kang, Sung Soo [Jeonju Univ., Jeonju (Korea, Republic of)

    2012-09-15

    In this study, we performed experimental tests on five SP 100 aluminum powder epoxy specimens with several after curing conditions in order to estimate their hardness with temperature and compressive strength. In the surface hardness test, it was found that the higher the after curing temperature, the higher was the hardness. In particular, it was found that the hardness of the specimens in cases 3 and 4 was much higher than in the other cases. In addition, in the compression tests carried out to evaluate the compressive strength, it was found that the specimens showed relatively similar stiffness and strength with after curing, and specimens with no after curing showed compression stress strain curves similar to those of thermoplastic resins.

  3. Experimental study on the compressive strength of grouted concrete block masonry based on nondestructive detection methods

    Institute of Scientific and Technical Information of China (English)

    JIANG Hong-bin; LI Long-fei

    2009-01-01

    Existing nondestructive detection methods were adopted to test the compressive strength of grouted concrete block masonry, i.e. the rebound method, pulling-out method and core drilling method were employed to test the strength of block, mortar and grouted concrete, respectively. The suitability of these methods for the testing of strength of grouted concrete block masonry was discussed, and the comprehensive strength of block masonry was appraised by combining existing nondestructive or micro-destructive detection methods. The nondestructive detection test on 25 grouted concrete block masonry specimens was carried out. Experimental results show that these methods mentioned above are applicable for the strength detection of grouted concrete block masonry. Moreover, the formulas of compressive strength, detection methods and proposals are given as well.

  4. Effect of raw material ratios on the compressive strength of magnesium potassium phosphate chemically bonded ceramics.

    Science.gov (United States)

    Wang, Ai-juan; Yuan, Zhi-long; Zhang, Jiao; Liu, Lin-tao; Li, Jun-ming; Liu, Zheng

    2013-12-01

    The compressive strength of magnesium potassium phosphate chemically bonded ceramics is important in biomedical field. In this work, the compressive strength of magnesium potassium phosphate chemically bonded ceramics was investigated with different liquid-to-solid and MgO-to-KH2PO4 ratios. X-ray diffractometer was applied to characterize its phase composition. The microstructure was imaged using a scanning electron microscope. The results showed that the compressive strength of the chemically bonded ceramics increased with the decrease of liquid-to-solid ratio due to the change of the packing density and the crystallinity of hydrated product. However, with the increase of MgO-to-KH2PO4 weight ratio, its compressive strength increased firstly and then decreased. The low compressive strength in lower MgO-to-KH2PO4 ratio might be explained by the existence of the weak phase KH2PO4. However, the low value of compressive strength with the higher MgO-to-KH2PO4 ratio might be caused by lack of the joined phase in the hydrated product. Besides, it has been found that the microstructures were different in these two cases by the scanning electron microscope. Colloidal structure appeared for the samples with lower liquid-to-solid and higher MgO-to-KH2PO4 ratios possibly because of the existence of amorphous hydrated products. The optimization of both liquid-to-solid and MgO-to-KH2PO4 ratios was important to improve the compressive strength of magnesium potassium phosphate chemically bonded ceramics.

  5. The estimation of compressive strength of normal and recycled aggregate concrete

    Directory of Open Access Journals (Sweden)

    Janković Ksenija

    2011-01-01

    Full Text Available Estimation of concrete strength is an important issue in ready-mixed concrete industry, especially, in proportioning new mixtures and for the quality assurance of the concrete produced. In this article, on the basis of the existing experimental data of compressive strength of normal and recycled aggregate concrete and equation for compressive strength calculating given in Technical regulation are compared. The accuracies of prediction by experimental data obtained in laboratory as well as by EN 1992-1-1, ACI 209 and SRPS U.M1.048 are compared on the basis of the coefficient of determination. The determination of the compressive strengths by the equation described here relies on determination of type of cement and age of concrete with the constant curing temperature.

  6. Non-Uniform Compressive Strength of Debonded Sandwich Panels

    DEFF Research Database (Denmark)

    Berggreen, Carl Christian; Simonsen, Bo Cerup

    2005-01-01

    This article describes the development, validation and application of a FEM based numerical model for prediction of residual strength of damaged sandwich panels. The core of the theoretical method is a newly developed procedure for prediction of the propagation of a face-core debond. As demonstra......This article describes the development, validation and application of a FEM based numerical model for prediction of residual strength of damaged sandwich panels. The core of the theoretical method is a newly developed procedure for prediction of the propagation of a face-core debond...

  7. Axial dynamic tensile strength of concrete under static lateral compression

    NARCIS (Netherlands)

    Weerheijm, J.

    2006-01-01

    The rate effect on concrete tensile strength can be modeled by the description of crack extension in a fictitious fracture plane [1,2].The plane represents the initial, internal damage and the geometry of the final fracture plane. In the paper, the same approach is applied to model the failure envel

  8. Strength and stiffness of thermally rectified eucalyptus wood under compression

    OpenAIRE

    Marcio Rogério da Silva; Gilmara de Oliveira Machado; José Otávio Brito; Carlito Calil Junior

    2013-01-01

    The aim of this work was the evaluation of the thermal-rectification process of reforestation wood Corymbia citriodora Hook by measuring of mechanical properties under compression parallel to the grain and also determining of chemical composition. The tested samples were thermally treated in a furnace with nitrogen-atmosphere at heating rate of 0.033 ºC.min-1, at temperatures of 160, 180, 200, 220 and 240 ºC. The chemical components and mechanical properties were affected with the thermal rec...

  9. Influence of Compression and Shear on the Strength of Composite Laminates with Z-Pinned Reinforcement

    Science.gov (United States)

    O'Brien, T. Kevin; Krueger, Ronald

    2005-01-01

    The influence of compression and shear loads on the strength of composite laminates with z-pins is evaluated parametrically using a 2D Finite Element Code (FLASH). Meshes were generated for three unique combinations of z-pin diameter and density. A laminated plate theory analysis was performed on several layups to determine the bi-axial stresses in the zero degree plies. These stresses, in turn, were used to determine the magnitude of the relative load steps prescribed in the FLASH analyses. Results indicated that increasing pin density was more detrimental to in-plane compression strength than increasing pin diameter. FLASH results for lamina with z-pins were consistent with the closed form results, and FLASH results without z-pins, if the initial fiber waviness due to z-pin insertion was added to the fiber waviness in the material to yield a total misalignment. Addition of 10% shear to the compression loading significantly reduced the lamina strength compared to pure compression loading. Addition of 50% shear to the compression indicated shear yielding rather than kink band formation as the likely failure mode. Two different stiffener reinforced skin configurations with z-pins, one quasi-isotropic and one orthotropic, were also analyzed. Six unique loading cases ranging from pure compression to compression plus 50% shear were analyzed assuming material fiber waviness misalignment angles of 0, 1, and 2 degrees. Compression strength decreased with increased shear loading for both configurations, with the quasi-isotropic configuration yielding lower strengths than the orthotropic configuration.

  10. Investigation on Compressive Strength of Special Concrete made with Crushed Waste Glass

    Directory of Open Access Journals (Sweden)

    Mohd Sani Mohd Syahrul Hisyam

    2015-01-01

    Full Text Available Special concrete is the type of concrete that produced by using waste material or using unusual techniques/method of preparation. Special concrete made with waste material is becoming popular in a construction site. This is because the special concrete is selected due to quality, integrity, economic factor and environmental factor. The waste glass is selected as an additional material to provide a good in compressive strength value. The compressive strength is the importance of mechanical properties of concrete and typically the concrete is sustained and stiffed in compression load. The significant issue to utilize the waste glass from the automotive windscreen is to improve the strength of concrete. The waste glass is crushed to become 5 mm size and recognised as crushed waste glass that be used in concrete as additional material. The main objective of the study is to determine the appropriate percentage of crushed waste glass in concrete grade, 30 in order to enhance the compressive strength. There are four mixes of concrete that contained of crushed waste glass with percentage of 2 %, 4 %, 6 % and 8 % and one control mix with 0 % of crushed waste glass. As the result, crushed waste glass with an additional 4 % in concrete is reported having a higher value of compressive strength in early and mature stage. In addition, if the percentage of crushed glass wastes in concrete increases and it leads to a reduction in the workability of concrete.

  11. Compressive strength evaluation of structural lightweight concrete by non-destructive ultrasonic pulse velocity method.

    Science.gov (United States)

    Bogas, J Alexandre; Gomes, M Glória; Gomes, Augusto

    2013-07-01

    In this paper the compressive strength of a wide range of structural lightweight aggregate concrete mixes is evaluated by the non-destructive ultrasonic pulse velocity method. This study involves about 84 different compositions tested between 3 and 180 days for compressive strengths ranging from about 30 to 80 MPa. The influence of several factors on the relation between the ultrasonic pulse velocity and compressive strength is examined. These factors include the cement type and content, amount of water, type of admixture, initial wetting conditions, type and volume of aggregate and the partial replacement of normal weight coarse and fine aggregates by lightweight aggregates. It is found that lightweight and normal weight concretes are affected differently by mix design parameters. In addition, the prediction of the concrete's compressive strength by means of the non-destructive ultrasonic pulse velocity test is studied. Based on the dependence of the ultrasonic pulse velocity on the density and elasticity of concrete, a simplified expression is proposed to estimate the compressive strength, regardless the type of concrete and its composition. More than 200 results for different types of aggregates and concrete compositions were analyzed and high correlation coefficients were obtained. PMID:23351273

  12. The Fire Resistance Performance of Recycled Aggregate Concrete Columns with Different Concrete Compressive Strengths

    Directory of Open Access Journals (Sweden)

    Hongying Dong

    2014-12-01

    Full Text Available In order to ascertain the fire resistance performance of recycled aggregate concrete (RAC components with different concrete compressive strengths, four full-scaled concrete columns were designed and tested under high temperature. Two of the four specimens were constructed by normal concrete with compressive strength ratings of C20 and C30, respectively, while the others were made from recycled coarse aggregate (RCA concrete of C30 and C40, respectively. Identical constant axial forces were applied to specimens while being subjected to simulated building fire conditions in a laboratory furnace. Several parameters from the experimental results were comparatively analyzed, including the temperature change, vertical displacement, lateral deflection, fire endurance, and failure characteristics of specimens. The temperature field of specimens was simulated with ABAQUS Software (ABAQUS Inc., Provindence, RI, USA and the results agreed quite well with those from the experiments. Results show that the rate of heat transfer from the surface to the interior of the column increases with the increase of the concrete’s compressive strength for both RAC columns and normal concrete columns. Under the same initial axial force ratio, for columns with the same cross section, those with lower concrete compressive strengths demonstrate better fire resistance performance. The fire resistance performance of RAC columns is better than that of normal concrete columns, with the same concrete compressive strength.

  13. Compressive Strength of Hydrostatic-Stress-Sensitive Materials at High Strain-Rates

    Institute of Scientific and Technical Information of China (English)

    LI Q M; LU Y B

    2008-01-01

    Many engineering materials demonstrate dynamic enhancement of their compressive strength with the increase of strain-rate.which have been included in material models to improve the reliability of numerical Simulations of the material and structural responses Under impact and biasl tcads,The strain-rate effects on the dynamic Compressive strength of a range of engineering materials which behave in hydrostatic-stress-sensitive manner were investigated.It is concluded that the dynamic enhancement of the compressive strength of a hydrostatic-stress-sensitive material may include inertia-induced lateral confinement effects,which,as a non-strain-rate factor,may greatly enhance the compressive strength of these materials.Some empirical formulae based on the dynamic stress-strain measurements over-predict the strain-rate effects on the compressive strength of these hydrostatic-stress-sensitive materials,and thus may over-estimate the structural resistance to impact and blast lgads.leading fo non-conservative design of protective structures.

  14. Effect of lightweight aggregate intrinsic Strength on lightweight concrete compressive strength and modulus of elasticity

    Directory of Open Access Journals (Sweden)

    Videla, C.

    2002-03-01

    Full Text Available The study of Structural Lightweight Concrete (SLC, which is a material generally composed of cement, water and lightweight aggregate, has been mainly focused on developing particular cases. Then, the main objective of this research was to generalise the knowledge of this type of material. Particularly, the effect of replacing conventional coarse aggregate by lightweight aggregate on mechanical properties of concrete was studied. SLC may be conceived as a two -phase material. The first phase, composed of cement, water and siliceous natural sand, is called the "resistant phase", and contributes to the structural strength. The second phase is the lightweight phase, comprised of coarse lightweight aggregate, and it is meant to decrease the concrete density. In this way it would be possible to describe the mechanical behaviour of concrete, based on lightweight aggregate and the cement mortar parameters. The obtained results allow for the proposition of relationships between mechanical properties of SLC (such as compressive strength and modulus of elasticity and the constituent materials properties and amount. At the same time, an easily measured index representing the structural capability of lightweight aggregate is also proposed, this index allows to estimate the potential mechanical properties of concrete which could be obtained by using a particular aggregate.

    El estudio del Hormigón Ligero Estructural (HLE, material compuesto generalmente por cemento, agua y árido ligero, ha estado enfocado principalmente al desarrollo de casos particulares. Por lo anterior, el objetivo principal de esta investigación fue generalizar el conocimiento sobre este material. En particular, la meta de este trabajo fue estudiar el efecto que tiene el reemplazo de árido convencional por un árido ligero, en las propiedades mecánicas del hormigón. El modelo aplicado conceptualiza al HLE como un material de dos fases, una denominada "soportante", constituida

  15. Structural mechanism and effect of hole compressibility on mechanical strength of MFLB

    Institute of Scientific and Technical Information of China (English)

    Yan MA; Alun

    2008-01-01

    We have studied the structural mechanism of micron flaky wood fiber light density board (MFLB), of which voids are an important structural characteristic. A new parameter called hole compressibility (η) was added to study the characteristics of MFLB further, in order to produce various levels of hole compressibility. A set of hot pressures was applied, and uniform parts at cross-sections of MFLB were selected to study the effects of hole com-pressibility on the modulus of elasticity (MOE) and modulus of rupture (MOR) of MFLB by microscopic analyses. The results showed that MFLB (0.3 g/cm in density) processed at various hot pressures (from 1.6 to 2.2 MPa) all meet the norms of the Japan Light Parti-cleboard Industrial Standard JISA 5908, where η≤ 0 ran-ging from -0.0487 to -0.068. The critical value of hole compressibility at which the strength began to decrease was also obtained. We compared the void distribution, size and shape at different void contents and hole com-pressibility and discussed the effects of hole compressibil-ity on MOE and MOR of MFLB as well. To a certain density of raw material and micro-fiber of a certain thick-ness, the strength of MFLB can be decreased with an increase in hole compressibility. When the hole compres-sibility of MLFB exceeds a certain critical value, loading at a lower level will decrease MOR and MOE of MFLB considerably.

  16. Benefits of Sealed-Curing on Compressive Strength of Fly Ash-Based Geopolymers

    Directory of Open Access Journals (Sweden)

    Sujeong Lee

    2016-07-01

    Full Text Available There is no standardized procedure for producing geopolymers; therefore, many researchers develop their own procedures for mixing and curing to achieve good workability and strength development. The curing scheme adopted is important in achieving maximum performance of resultant geopolymers. In this study, we evaluated the impact of sealed and unsealed curing on mechanical strength of geopolymers. Fly ash-based geopolymers cured in sealed and unsealed moulds clearly revealed that retention of water during curing resulted in superior strength development. The average compressive strength of sealed-cured geopolymers measured after 1 day of curing was a modest 50 MPa, while after 7 day curing the average compressive strength increased to 120~135 MPa. In the unsealed specimens the average compressive strength of geopolymers was lower; ranging from 60 to 90 MPa with a slight increase as the curing period increased. Microcracking caused by dehydration is postulated to cause the strength decrease in the unsealed cured samples. These results show that water is a crucial component for the evolution of high strength three-dimensional cross-linked networks in geopolymers.

  17. Alumina/Polyimide Composite Porous Nanosolid:Dielectric Characteristics and Compressive Strength

    Institute of Scientific and Technical Information of China (English)

    LUAN Chun-hong; GENG Yu-jing; YU Qin-qin; CAO Li-li; LIAN Gang; CUI De-liang

    2012-01-01

    Al2O3 porous nanosolid was prepared via solvothermal hot-press(SHP) method.The dielectric constant of Al2O3 porous nanosolid is as low as 2.34,while its compressive strength is very poor.In order to improve the compressive strength and maitain low dielectric constant,polyimidc was introduced to prepare Al2O3/polyimide composite porous nanosolid.Compared to Al2O3 porous nanosolid,Al2O3/polyimide composite porous nanosolid possesses much higher compressive strength,which reaches its saturation value when the mass loading of polyimide is 7.75%.In addition,the in situ Fourier transformation infrared(FTIR) monitoring result reveals that Al2O3/polyimide composite porous nanosolid is stable up to 400 ℃.

  18. An investigation of the compressive strength of Kevlar 49/epoxy composites

    Science.gov (United States)

    Kulkarni, S. V.; Rosen, B. W.; Rice, J. S.

    1975-01-01

    Tests were performed to evaluate the effect of a wide range of variables including matrix properties, interface properties, fiber prestressing, secondary reinforcement, and others on the ultimate compressive strength of Kevlar 49/epoxy composites. Scanning electron microscopy is used to assess the resulting failure surfaces. In addition, a theoretical study is conducted to determine the influence of fiber anisotropy and lack of perfect bond between fiber and matrix on the shear mode microbuckling. The experimental evaluation of the effect of various constituent and process characteristics on the behavior of these unidirectional composites in compression did not reveal any substantial increase in strength. However, theoretical evaluations indicate that the high degree of fiber anisotropy results in a significant drop in the predicted stress level for internal instability. Scanning electron microscope data analysis suggests that internal fiber failure and smooth surface debonding could be responsible for the measured low compressive strengths.

  19. Characterization of compressive and short beam shear strength of bamboo opened cell foam core sandwich composites

    Science.gov (United States)

    Setyawan, Paryanto Dwi; Sugiman, Saputra, Yudhi

    2016-03-01

    The paper presents the compressive and the short beam shear strength of a sandwich composite with opened cell foam made of bamboo fiber as the core and plywood as the skins. The core thickness was varied from 10 mm to 40 mm keeping the volume fraction of fiber constant. Several test s were carried out including the core density, flatwise compressive and the short beam shear testing in three point bending. The results show that the density of bamboo opened cell foam is comparable with commercial plastic foam, such as polyurethane foam. The compressive strength tends to increase linearly with increasing the core thickness. The short beam shear failure load of the sandwich composite increases with the increase of core thickness, however on the contrary, the short beam shear strength which tends to sharply decrease from the thickness of 10 mm to 30 mm and then becomes flat.

  20. Soft computing methods for estimating the uniaxial compressive strength of intact rock from index tests

    OpenAIRE

    Mishra, A. Deepak; Srigyan, M.; Basu, A.; Rokade, P. J.

    2015-01-01

    Uniaxial compressive strength ( UCS ) is one of the most widely used rock mechanical parameters in rock engineering. Determi- nation of this parameter in the laboratory, however, requires quality rock specimens. The use of various index tests that require little or no specimen preparation and are easier to perform as well as less expensive than the uniaxial compression test has always been attractive in order to predict UCS of rock materials empirically 1 – 16 . Amongst differe...

  1. Improving the Prediction of Cement Compressive Strength by Coupling of Dynamical Models

    OpenAIRE

    Tsamatsoulis, D.

    2016-01-01

    The dynamic approach of two well-known techniques has been used to predict a cement’s 28-day compressive strength: Multiple linear regression (MLR), and artificial neural networks (ANN). The modeling is based on Portland cement data and utilizes daily physical, chemical analyses, and early strength results at days 1 and 7. Two kinds of models have been built, containing the 1-day strength as an independent variable, or both 1- and 7-day strength. The models are dynamic because they are applie...

  2. Effect of In-Situ Curing on Compressive Strength of Reactive Powder Concrete

    Directory of Open Access Journals (Sweden)

    Bali Ika

    2016-01-01

    Full Text Available A development of Reactive Powder Concrete (RPC currently is the use of quartz powder as a stabilizing agent with the content to cement ratio of 30% and steam curing method in an autoclave temperature of 250ºC which produced a high compressive strength of 180 MPa. That RPC can be generated due to one reason for using the technique of steam curing in an autoclave in the laboratory. This study proposes in-situ curing method in order the curing can be applied in the field and with a reasonable compressive strength results of RPC. As the benchmarks in this study are the curing methods in laboratory that are steam curing of 90°C for 8 hours (C1, and water curing for 28 days (C2. For the in-situ curing methods that are covering with tarpaulins and flowed steam of 3 hours per day for 7 days (C3, covering with wet sacks for 28 days (C4, and covering with wet sacks for 28 days for specimen with unwashed sand as fine aggregate (C5. The comparison of compressive strength of the specimens in this study showed compressive strength of RPC with in-situ steam curing (101.64 MPa close to the compressive strength of RPC with steam curing in the laboratory with 8.2% of different. While in-situ wet curing compared with the water curing in laboratory has the different of 3.4%. These results indicated that the proposed in-situ curing methods are reasonable good in term of the compressive strength that can be achieved.

  3. Compressive strength and microstructural analysis of fly ash/palm oil fuel ash based geopolymer mortar

    International Nuclear Information System (INIS)

    Highlights: • Results show POFA is adaptable as replacement in FA based geopolymer mortar. • The increase in POFA/FA ratio delay of the compressive development of geopolymer. • The density of POFA based geoploymer is lower than FA based geopolymer mortar. - Abstract: This paper presents the effects and adaptability of palm oil fuel ash (POFA) as a replacement material in fly ash (FA) based geopolymer mortar from the aspect of microstructural and compressive strength. The geopolymers developed were synthesized with a combination of sodium hydroxide and sodium silicate as activator and POFA and FA as high silica–alumina resources. The development of compressive strength of POFA/FA based geopolymers was investigated using X-ray florescence (XRF), X-ray diffraction (XRD), Fourier transform infrared (FTIR), and field emission scanning electron microscopy (FESEM). It was observed that the particle shapes and surface area of POFA and FA as well as chemical composition affects the density and compressive strength of the mortars. The increment in the percentages of POFA increased the silica/alumina (SiO2/Al2O3) ratio and that resulted in reduction of the early compressive strength of the geopolymer and delayed the geopolymerization process

  4. Reliable evaluation method of quality control for compressive strength of concrete

    Institute of Scientific and Technical Information of China (English)

    CHEN Kuen-suan; SUNG Wen-pei; SHIH Ming-hsiang

    2005-01-01

    Concrete in reinforced concrete structure (RC) is generally under significant compressive stress load. To guarantee required quality and ductility, various tests have to be conducted to measure the concrete's compressive strength based on ACI(American Concrete Institute) code. Investigations of recent devastating collapses of structures around the world showed that some of the collapses directly resulted from the poor quality of the concrete. The lesson learned from these tragedies is that guaranteeing high quality of concrete is one of the most important factors ensuring the safety of the reinforced concrete structure.In order to ensure high quality of concrete, a new method for analyzing and evaluating the concrete production process is called for.In this paper, the indices of fit and stable degree are proposed as basis to evaluate the fitness and stability of concrete's compressive strength. These two indices are combined to define and evaluate the quality index of the compressive strength of concrete. Principles of statistics are used to derive the best estimators of these indices. Based on the outcome of the study, a concrete compressive strength quality control chart is proposed as a tool to help the evaluation process. Finally, a new evaluation procedure to assess the quality control capability of the individual concrete manufacturer is also proposed.

  5. Degree of compression as a potential process control tool of tablet tensile strength.

    Science.gov (United States)

    Nordström, Josefina; Alderborn, Goran

    2011-01-01

    The current view on the development and manufacturing of pharmaceutical preparations points towards improved control tools that can be implemented in pharmaceutical manufacturing as a means to better control end product properties. The objective of this paper was to investigate the relationship between tablet tensile strength and the degree of bed compression in order to evaluate the suitability of assessing the straining of the powder bed during tableting as a process control tool of tablet tensile strength. Microcrystalline cellulose was used as powder raw material and subjected to wet granulation by different procedures to create agglomerates of different physical and compression properties. The produced agglomerates thus showed a large variation in compressibility and compactibility. However, in terms of the relationship between the degree of compression and the tablet tensile strength, all agglomerates gathered reasonably around a single general relationship. The degree of compression hence appears to be a potential valuable process control tool of the tablet tensile strength that may enable the use of an adaptive tableting process with improved product quality consistency. PMID:20649411

  6. Compressive Strength of Concrete Using Recycled Concrete Aggregate as Complete Replacement of Natural Aggregate

    OpenAIRE

    Osei, Daniel Yaw

    2013-01-01

    This paper presents a report of an experimental investigation on the effect of complete replacement of natural aggregate by recycled concrete aggregate in the production of concrete on the compressive strength of concrete. Two sets of concrete mixtures of ratios 1:3:6, 1:2:4, 1:11/2:3, 1:1:2 by mass were cast using natural aggregates and recycled aggregates concrete respectively. The 28-day compressive strengths of 1:3:6, 1:2:4, 1:11/2:3, 1:1:2 concrete using recycled concrete aggregates were...

  7. The ultimate strength of doubler plate reinforced Y-joints under compression loading

    Institute of Scientific and Technical Information of China (English)

    FENQ Qi; TAN Jia-hua

    2005-01-01

    It is common practice in the offshore industry to solve the punching shear problem due to compression by using doubler plate. The finite-element method is a useful tool for studying this problem. The aim of this paper is to study the static strength of doubler plate reinforced Y-joints subjected to compression loading. The finite-element method is adopted in numerical parametric studies. The individual influences of the geometric parameters βand τd (doubler plate to chord wall thickness ratio) and ld/d1(dubler plate length to brace diameter ratio) on the ultimate strength are made clear. The results show the size of plate may have important effects on the strength of reinforced joints. It is found that the ultimate strength of Y-joints reinforced with appropriately proportioned doubler plates can be greatly improved nearly up tothree times to un-reinforced Y-joints.

  8. General and mechanistic optimal relationships for tensile strength of doubly convex tablets under diametrical compression

    OpenAIRE

    Razavi, Sonia M.; Gonzalez, Marcial; Cuitino, Alberto M.

    2014-01-01

    We propose a general framework for determining optimal relationships for tensile strength of doubly convex tablets under diametrical compression. This approach is based on the observation that tensile strength is directly proportional to the breaking force and inversely proportional to a non-linear function of geometric parameters and materials properties. This generalization reduces to the analytical expression commonly used for flat faced tablets, i.e., Hertz solution, and to the empirical ...

  9. Effect of additives on the compressive strength and setting time of a Portland cement

    Directory of Open Access Journals (Sweden)

    Desirée Freitas Mryczka Machado

    2010-06-01

    Full Text Available Improvements in strength and setting time of Portland cements (PC are needed to enhance their performance as endodontic and load bearing materials. This study sought to enhance the compressive strength and setting time of a PC by adding one of the following additives: 20% and 30% poly-methylmethacrylate (PMMA, 20% and 30% irregular and spherical amalgam alloys, and 10% CaCl2. The control consisted of unreinforced PC specimens. Setting time was determined using a Gillmore apparatus according to standardized methods while compressive strength was measured using a universal testing machine after 21 hours or 60 days of water storage. Data were analyzed by ANOVA, Tukey and Games-Howell tests (α = 5%. All additives significantly decreased both initial and final setting times as compared with the PC-control (p < .05. 30% PMMA and 30% irregular alloy had the lowest values of initial setting time. 30% irregular alloy also produced the lowest values of final setting time while 30% spherical alloy yielded the highest (p < .05. No differences were detected between the compressive strength values of 21 hours and 60 days. While 10% CaCl2, 20% and 30% PMMA produced values significantly lower than the PC-control, 30% spherical alloy significantly improved the compressive strength of the reinforced PC (p < .05. In summary, all additives significantly reduced the setting time and 30% spherical amalgam alloy yielded a significant increase in compressive strength for the tested PC, which might represent an improved composition for PCs to expand their use as endodontic and potentially load bearing materials.

  10. Experimental and theoretical research on residual strength of plain concrete under compressive fatigue loading

    Institute of Scientific and Technical Information of China (English)

    MENG Xian-hong; SONG Yu-pu

    2008-01-01

    To investigate the residual strength of concrete under fatigue loading, experiments were conducted to determine the functional relation between residual strength and the number of cycles. 80 100mm×100mm×100ram specimens of plain concrete were tested under uniaxial compressive fatigue loading. Based on probabili-ty distribution of the residual strength of concrete under fatigue loading, the empirical expressions of the residual strength corresponding to the number of cycles were obtained. There is a good correlation between residual strength and residual secant elastic modulus. Thus the relationship between residual secant elastic modulus and the number of cycles is established. A damage variable based on the longitudinal maximum strain is defined, and a good linearity relationship between residual strength and damage is found out.

  11. Compressive strength and heavy metal leaching behaviour of mortars containing spent catalyst.

    Science.gov (United States)

    Rattanasak, U; Jaturapitakkul, C; Sudaprasert, T

    2001-10-01

    This investigation was set and aimed to study the possibility of using spent catalyst as a concrete constituent which the spent catalyst was used as sand. Besides the spent catalyst was used as sand, it was also ground to very small particle size as small as that of cement and used as 20% replacement of cement by weight. Compressive strengths and leaching characteristics of lead, chromium, cadmium, and nickel in mortars containing spent catalyst and ground spent catalyst were tested. The results presented revealed that the compressive strength of mortar containing spent catalyst increased with ages. The results also indicated that the compressive strength of mortar containing spent catalyst at the proportion of 1.25 times of cement by weight was strong enough to make a concrete brick. In case of the ground spent catalyst being used to replace cement, it made the compressive strength lower than that of the standard mortar approximately 20%. The leachate results of lead and chromium from spent catalyst were lower than the allowance, but cadmium and nickel exceeded the limits. After the spent catalyst was fixed with cement, the leaching of the heavy metals did not exceed the industrial effluent standard. Therefore, the heavy metals mentioned earlier were not a problem in using spent catalyst as a concrete constituent.

  12. Preparation and Compressive Strength of Calcium Phosphate Bone Cement Containing N, O-carboxymethyl Chitosan

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    N, O-carboxymethyl chitosan ( CMCTS ), a kind of biodegradable organic substance, was added to calcium phosphate bone cement (CPC) to produce a composite more similar in composition to human bone. The compressive strength of the new material was increased by 10 times compared with conventional CPC.

  13. Prediction of Corrosion Resistance of Concrete Containing Natural Pozzolan from Compressive Strength

    Science.gov (United States)

    al-Swaidani, A. M.; Ismat, R.; Diyab, M. E.; Aliyan, S. D.

    2015-11-01

    A lot of Reinforced Concrete (RC) structures in Syria have suffered from reinforcement corrosion which shortened significantly their service lives. Probably, one of the most effective approaches to make concrete structures more durable and concrete industry on the whole - more sustainable is to substitute pozzolan for a portion of Portland cement (PC). Syria is relatively rich in natural pozzolan. In the study, in order to predict the corrosion resistance from compressive strength, concrete specimens were produced with seven cement types: one plain Portland cement (control) and six natural pozzolan-based cements with replacement levels ranging from 10 to 35%. The development of the compressive strengths of concrete cube specimens with curing time has been investigated. Chloride penetrability has also been evaluated for all concrete mixes after three curing times of 7, 28 and 90 days. The effect on resistance of concrete against damage caused by corrosion of the embedded reinforcing steel has been investigated using an accelerated corrosion test by impressing a constant anodic potential for 7, 28 and 90 days curing. Test results have been statistically analysed and correlation equations relating compressive strength and corrosion performance have been developed. Significant correlations have been noted between the compressive strength and both rapid chloride penetrability and corrosion initiation times. So, this prediction could be reliable in concrete mix design when using natural pozzolan as cement replacement.

  14. The Effect of Blood Contamination on the Compressive Strength of Calcium-Enriched Mixture

    Directory of Open Access Journals (Sweden)

    Alireza Adl

    2015-03-01

    Full Text Available Statement of the Problem: In clinical situations, Calcium-Enriched Mixture (CEM comes into direct contact or even mixes with blood during or after placement. Purpose: The aim of this study was to evaluate the effect of blood contamination on the compressive strength of CEM. Materials and Method: Three experimental groups were included in this study. In the first group, CEM was mixed with distilled water and was exposed to normal saline (control group. In the second group, CEM cement was mixed with distilled water and then was exposed to blood. In the third group, CEM was mixed with and exposed to blood. Nine custom-made two-part split Plexiglas molds with five holes were used to form CEM samples for compressive strength testing (15 samples in each group. After 7 days of incubation, compressive bond strength testing was performed using a universal testing machine. Data were statistically analyzed using the Mann–Whitney U test with a significance level of p 0.05. Conclusion: It can be concluded that exposure to blood does not adversely affect the compressive strength of CEM, but incorporation of blood makes the cement very brittle.

  15. Effects of CuO nanoparticles on compressive strength of self-compacting concrete

    Indian Academy of Sciences (India)

    Ali Nazari; Shadi Riahi

    2011-06-01

    In the present study, the compressive strength, thermal properties and microstructure of self-compacting concrete with different amounts of CuO nanoparticles have been investigated. CuO nanoparticles with an average particle size of 15 nm were added to self-compacting concrete and various properties of the specimens were measured. The results indicate that CuO nanoparticles are able to improve the compressive strength of self-compacting concrete and reverse the negative effects of superplasticizer on compressive strength of the specimens. CuO nanoparticles as a partial replacement of cement up to 4 wt.% could accelerate C–S–H gel formation as a result of the increased crystalline Ca(OH)2 amount at the early ages of hydration. Increasing CuO nanoparticle content to more than 4 wt.%, causes reduced compressive strength because of unsuitable dispersion of nanoparticles in the concrete matrix. Accelerated peak appearance in conduction calorimetry tests, more weight loss in thermogravimetric analysis and more rapid appearance of peaks related to hydrated products in X-ray diffraction results, all indicate that CuO nanoparticles up to 4 wt.% could improve the mechanical and physical properties of the specimens. Finally, CuO nanoparticles improved the pore structure of concrete and caused shifting of the distributed pores from harmless to low harm.

  16. Compression strength of sandwich panels with sub-interface damage in the foam core

    NARCIS (Netherlands)

    Koissin, Vitaly; Shipsha, Andrey; Skvortsov, Vitaly

    2009-01-01

    This paper addresses the effect of a local quasi-static indentation or a low-velocity impact on the residual strength of foam core sandwich panels subjected to edgewise compression. The damage is characterized by a local zone of crushed core accompanied by a residual dent in the face sheet. Experime

  17. Comparison of Compression Strength of Red Oak and Pedunculate Oak Wood from Mine Dumps

    OpenAIRE

    Brich, Jiří

    2013-01-01

    The aim of this work was to determine the strength of wood in compression on samples of oak and red oak coming from the reclaimed landscape, the Most brown coal basins. There was also examined the dependence of the strength of density, which eventually significantly affected. These results were achieved by laboratory tests and calculations according to. The average value of red oak strength is 55,29 MPa and tensile oak 56,18 MPa. These values correspond to those in the literature. ...

  18. Compressive strength of dental composites photo-activated with different light tips

    Science.gov (United States)

    Galvão, M. R.; Caldas, S. G. F. R.; Calabrez-Filho, S.; Campos, E. A.; Bagnato, V. S.; Rastelli, A. N. S.; Andrade, M. F.

    2013-04-01

    The aim of this study was to evaluate the compressive strength of microhybrid (Filtek™ Z250) and nanofilled (Filtek™ Supreme XT) composite resins photo-activated with two different light guide tips, fiber optic and polymer, coupled with one LED. The power density was 653 mW cm-2 when using the fiber optic light tip and 596 mW cm-2 with the polymer. After storage in distilled water at 37 ± 2 °C for seven days, the samples were subjected to mechanical testing of compressive strength in an EMIC universal mechanical testing machine with a load cell of 5 kN and speed of 0.5 mm min-1. The statistical analysis was performed using ANOVA with a confidence interval of 95% and Tamhane’s test. The results showed that the mean values of compressive strength were not influenced by the different light tips (p > 0.05). However, a statistical difference was observed (p composite resin photo-activated with the fiber optic light tip and the nanofilled composite resin. Based on these results, it can be concluded that microhybrid composite resin photo-activated with the fiber optic light tip showed better results than nanofilled, regardless of the tip used, and the type of the light tip did not influence the compressive strength of either composite. Thus, the presented results suggest that both the fiber optic and polymer light guide tips provide adequate compressive strength to be used to make restorations. However, the fiber optic light tip associated with microhybrid composite resin may be an interesting option for restorations mainly in posterior teeth.

  19. Effect of pH and Lidocaine on the Compressive Strength of Calcium Enriched Mixture Cement

    Directory of Open Access Journals (Sweden)

    Sobhnamayan F

    2015-12-01

    Full Text Available Statement of Problem: The pH of the human abscess has been measured as low as 5.0. This low pH could potentially inhibit setting reactions, affect adhesion, or increase the solubility of root end filling materials hence affect the compressive strength. Moreover, root end filling materials might expose or even mix with lidocaine HCL during periapical surgery. Objectives: The aim of this in vitro study was to evaluate the effect of acidic pH and lidocaine on the compressive strength of calcium-enriched mixture (CEM. Materials and Methods: CEM was mixed according to the manufacturer’s instructions or with lidocaine (L, and condensed into 6 × 4 mm split moulds. The samples were exposed to phosphate buffered saline (PBS at pH 5 or 7.4 for 7 or 28 days. Cylindrical blocks of CEM (total number = 120 and 15 for each group were subjected to compressive strength test using a universal testing machine. Data were analysed using three-factor analysis of variance (ANOVA. Results: Regardless of pH and time, significant differences were not found between lidocaine groups and the groups that were mixed according to the manufacturer’s instruction (p = 0.083. For both mixing agents, regardless of time, there were no significant differences between the two pH levels (p = 0.157. Regardless of the material and pH, there was a significant increase in the compressive strength from days 7 to 28 (p < 0.001. Conclusions: Mixtures with lidocaine and exposure to an acidic environment had no adverse effects on the compressive strength of CEM Cement.

  20. Compressive strength of dental composites photo-activated with different light tips

    International Nuclear Information System (INIS)

    The aim of this study was to evaluate the compressive strength of microhybrid (Filtek™ Z250) and nanofilled (Filtek™ Supreme XT) composite resins photo-activated with two different light guide tips, fiber optic and polymer, coupled with one LED. The power density was 653 mW cm−2 when using the fiber optic light tip and 596 mW cm−2 with the polymer. After storage in distilled water at 37 ± 2 °C for seven days, the samples were subjected to mechanical testing of compressive strength in an EMIC universal mechanical testing machine with a load cell of 5 kN and speed of 0.5 mm min−1. The statistical analysis was performed using ANOVA with a confidence interval of 95% and Tamhane’s test. The results showed that the mean values of compressive strength were not influenced by the different light tips (p > 0.05). However, a statistical difference was observed (p < 0.001) between the microhybrid composite resin photo-activated with the fiber optic light tip and the nanofilled composite resin. Based on these results, it can be concluded that microhybrid composite resin photo-activated with the fiber optic light tip showed better results than nanofilled, regardless of the tip used, and the type of the light tip did not influence the compressive strength of either composite. Thus, the presented results suggest that both the fiber optic and polymer light guide tips provide adequate compressive strength to be used to make restorations. However, the fiber optic light tip associated with microhybrid composite resin may be an interesting option for restorations mainly in posterior teeth. (paper)

  1. Optimum Compressive Strength of Hardened Sandcrete Building Blocks with Steel Chips

    Directory of Open Access Journals (Sweden)

    Alohan Omoregie

    2013-02-01

    Full Text Available The recycling of steel chips into an environmentally friendly, responsive, and profitable commodity in the manufacturing and construction industries is a huge and difficult challenge. Several strategies designed for the management and processing of this waste in developed countries have been largely unsuccessful in developing countries mainly due to its capital-intensive nature. To this end, this investigation attempts to provide an alternative solution to the recycling of this material by maximizing its utility value in the building construction industry. This is to establish their influence on the compressive strength of sandcrete hollow blocks and solid cubes with the aim of specifying the range percent of steel chips for the sandcrete optimum compressive strength value. This is particularly important for developing countries in sub-Saharan Africa, and even Latin America where most sandcrete blocks exhibit compressive strengths far below standard requirements. Percentages of steel chips relative to the weight of cement were varied and blended with the sand in an attempt to improve the sand grading parameters. The steel chips variations were one, two, three, four, five, ten and fifteen percent respectively. It was confirmed that the grading parameters were improved and there were significant increases in the compressive strength of the blocks and cube samples. The greatest improvement was noticed at four percent steel chips and sand combination. Using the plotted profile, the margin of steel chips additions for the optimum compressive strength was also established. It is recommended that steel chip sandcrete blocks are suitable for both internal load bearing, and non-load bearing walls, in areas where they are not subjected to moisture ingress. However, for external walls, and in areas where they are liable to moisture attack after laying, the surfaces should be well rendered. Below ground level, the surfaces should be coated with a water

  2. Compressive Strength and Static Modulus of Elasticity of Periwinkle Shell Ash Blended Cement Concrete

    Directory of Open Access Journals (Sweden)

    Akaninyene Afangide Umoh

    2012-12-01

    Full Text Available The study examined the effect of periwinkle shell ash as supplementary cementitious material on the compressive strength and static modulus of elasticity of concrete with a view to comparing it’s established relation with an existing model. The shells were calcined at a temperature of 800oC. Specimens were prepared from a mix of designed strength 25N/mm2. The replacement of cement with periwinkle shell ash (PSA was at five levels of 0, 10, 20, 30 and 40% by volume. A total of 90 cubical and cylindrical specimens each were cast and tested at 7, 14, 28, 90, 120 and 180 days. The results revealed that the PSA met the minimum chemical and physical requirements for class C Pozzolans. The compressive strength of the PSA blended cement concrete increased with increase in curing age up to 180 days but decreased as the PSA content increased. The design strength was attained with 10%PSA content at the standard age of 28 days. The static modulus of elasticity of PSA blended cement concrete was observed to increase with increased in curing age and decreases with PSA content. In all the curing ages 0%PSA content recorded higher value than the blended cement concrete. The statistical analysis indicated that the percentage PSA replacement and the curing age have significant effect on the properties of the concrete at 95% confidence level. The relation between compressive strength and static modulus of elasticity fitted into existing model for normal-weight concrete.

  3. Retention Strength after Compressive Cyclic Loading of Five Luting Agents Used in Implant-Supported Prostheses

    Directory of Open Access Journals (Sweden)

    Angel Alvarez-Arenal

    2016-01-01

    Full Text Available The purpose of this study was to evaluate and compare the retention strength of five cement types commonly used in implant-retained fixed partial dentures, before and after compressive cyclic loading. In five solid abutments screwed to 5 implant analogs, 50 metal Cr-Ni alloy copings were cemented with five luting agents: resin-modified glass ionomer (RmGI, resin composite (RC, glass ionomer (GI, resin urethane-based (RUB, and compomer cement (CC. Two tensile tests were conducted with a universal testing machine, one after the first luting of the copings and the other after 100,000 cycles of 100 N loading at 0.72 Hz. The one way ANOVA test was applied for the statistical analysis using the post hoc Tukey test when required. Before and after applying the compressive load, RmGI and RC cement types showed the greatest retention strength. After compressive loading, RUB cement showed the highest percentage loss of retention (64.45%. GI cement recorded the lowest retention strength (50.35 N and the resin composite cement recorded the highest (352.02 N. The type of cement influences the retention loss. The clinician should give preference to lower retention strength cement (RUB, CC, and GI if he envisages any complications and a high retention strength one (RmGI, RC for a specific clinical situation.

  4. Effect of quartz sand on compressive strength of the solid waste composite

    Science.gov (United States)

    Masturi, Marwoto, Putut; Sunarno, Rustad, Supriadi

    2016-02-01

    A solid waste composite was successfully made. Preliminary, the composite was synthesized using polyurethane (PU) as binder mixed with the solid waste using simple mixing method and then hot-pressed at at pressure of 4 metric-tons and temperature of 80°C for 20 minutes. To enhance its strength, quartz sand partilces with varied content then were added into the PU-solid waste mixture. From the compressive strength test, it was obtained that PU/solid waste composite with PU fraction (w/w) of 0.43 has optimum compressive strength of 38.91 MPa. Having been added quartz sand having average particles size of 0.94 μm, its compressive strength attains maximum at 40.47 MPa for quartz sand fraction (w/w) of 4.27 × 10-3. The strength is comparable to that of clay brick, slate stone, sandstone, limestone, alder wood, aspen wood, black cherry and pine woods. Therefore, this composite is very adequate to compete the building materials such as the bricks, stones and woods.

  5. THE COMPRESSIVE AND FLEXURAL STRENGTHS OF SELF-COMPACTING CONCRETE USING RAW RICE HUSK ASH

    Directory of Open Access Journals (Sweden)

    MD NOR ATAN

    2011-12-01

    Full Text Available This study investigates the compressive and flexural strengths of self-compacting concrete incorporating raw rice husk ash, individually and in combination with other types of mineral additives, as partial cement replacement. The additives paired with raw rice husk ash were fine limestone powder, pulverized fuel ash and silica fumes. The mix design was based on the rational method where solid constituents were fixed while water and superplasticizer contents were adjusted to produce optimum viscosity and flowability. All mixes were designed to achieve SF1 class slump-flow with conformity criteria ≥ 520 mm and ≤ 700 mm. Test results show that 15% replacement of cement using raw rice husk ash produced grade 40 concrete. It was also revealed that 30% and 45% cement replacements using raw rice husk ash combined with limestone powder and raw rice husk ash combined with limestone powder and silica fume respectively, produced comparable compressive strength to normal concrete and improved flexural strengths.

  6. A low cost method of testing compression-after-impact strength of composite laminates

    Science.gov (United States)

    Nettles, Alan T.

    1991-01-01

    A method was devised to test the compression strength of composite laminate specimens that are much thinner and wider than other tests require. The specimen can be up to 7.62 cm (3 in) wide and as thin as 1.02 mm (.04 in). The best features of the Illinois Institute of Technology Research Institute (IITRI) fixture are combined with an antibuckling jig developed and used at the University of Dayton Research Institute to obtain a method of compression testing thin, wide test coupons on any 20 kip (or larger) loading frame. Up to 83 pct. less composite material is needed for the test coupons compared to the most commonly used compression-after-impact (CAI) tests, which calls for 48 ply thick (approx. 6.12 mm) test coupons. Another advantage of the new method is that composite coupons of the exact lay-up and thickness of production parts can be tested for CAI strength, thus yielding more meaningful results. This new method was used to compression test 8 and 16 ply laminates of T300/934 carbon/epoxy. These results were compared to those obtained using ASTM standard D 3410-87 (Celanese compression test). CAI testing was performed on IM6/3501-6, IM7/SP500 and IM7/F3900. The new test method and associated fixture work well and is a valuable asset to MSFC's damage tolerance program.

  7. Compressive strength and microstructure of carbon nanotubes-fly ash cement composites

    International Nuclear Information System (INIS)

    In this work, carbon nanotubes of 0.5 and 1% by weight were added for the first time in a fly ash cement system to produce carbon nanotubes-fly ash composites in the form of pastes and mortars. Compressive strengths of the composites were then investigated. It was found that the use of carbon nanotubes resulted in higher strength of fly ash mortars. The highest strength obtained for 20% fly ash cement mortars was found at 1% carbon nanotubes where the compressive strength at 28 days was 51.8 MPa. This benefit can clearly be seen in fly ash cement with fly ash of 20% where the importance of the addition of carbon nanotubes means that the relative strength to that of Portland cement became almost 100% at 28 days. In addition, scanning electron micrographs also showed that good interaction between carbon nanotubes and the fly ash cement matrix is seen with carbon nanotubes acting as a filler resulting in a denser microstructure and higher strength when compared to the reference fly ash mix without CNTs.

  8. Correlation between aggregate quality and compressive strength of andesite from Hungary

    Science.gov (United States)

    Czinder, Balázs; Török, Ákos

    2015-04-01

    Andesite is one of the most common lithology that is used as aggregate. Testing of aggregate quality traditionally includes Los Angeles, micro-Deval tests and the quality of the stone is assessed according to these values. In the present paper both aggregate properties and strength properties of andesites are compared in order to find correlation between aggregate strength, durability and compressive and tensile strength as well as frost resistance. Tests were made from andesite types obtained from two operating quarries of Nógrádkövesd and Gyöngyössolymos. Uniaxial compressive strength (UCS) values were compared with aggregate test results obtained from the same block. Air dry, water saturated and freeze-thaw subjected specimens were tested. According to lithological description and fabric analyses samples were grouped into 4 main lithotypes: one from Nógrádkövesd and three from Gyöngyössolymos. Fine porphyric andesite from Gyöngyössolymos provided the best micro-Deval values. In terms of uniaxial compressive strength the same trend was found, fine porphyric andesite from Gyöngyössolymos had the highest UCS under laboratory conditions, while coarser porphyritic andesite from the same quarry had lower strength. Water saturation decreased UCS as it was expected. Tensile strength values show a gradual deceases from air dry to water saturated and finally subjected to freeze-thaw cycles. Mean micro-Deval value of fine porphyric Gyöngyössolymos andesite was about 7, while that of the coarser porphyritic andesite was app. 16. These values are still higher than the mean micro-Deval test result of Nógrádkövesd andesite; which was 20. A good correlation was found in between Los Angeles and micro-Deval values, but there was no indication that micro-Deval values correlate well with UCS.

  9. The influence of nickel slag aggregate concentration to compressive and flexural strength on fly ash-based geopolymer composite

    Science.gov (United States)

    Sujiono, E. H.; Setiawan, A.; Husain, H.; Irhamsyah, A.; Samnur, S.; Subaer, S.

    2016-04-01

    Fly ash-based geopolymer with nickel slag aggregate has been successfully produced. Fly ash and nickel slag were obtained from Bosowa Jeneponto Power Plant and PT. Vale Indonesia, respectively. This research aims to investigate the influence of nickel slag concentration to compressive strength, flexural strength, and microstructure of geopolymer composite. The increment of nickel slag aggregate on fly ash was relative to the weight of samples. Geopolymer composite were synthesized by using alkali activated method, cured at temperature of 70 °C for 1 hour. The resulting composites were left at room temperature for 14 days, before compressive and flexural strength were performed. The results showed that the addition of nickel slag aggregate was found to increase the compressive strength of the material. The optimum compressive strength was 14.81 MPa with the addition of 10% aggregate. The optimum flexural strength was 2.63 MPa with the addition of 15% aggregate.

  10. Electrical resistivity measurement to predict uniaxial compressive and tensile strength of igneous rocks

    Indian Academy of Sciences (India)

    Sair Kahraman; Tekin Yeken

    2010-12-01

    Electrical resistivity values of 12 different igneous rocks were measured on core samples using a resistivity meter in the laboratory. The resistivity tests were conducted on the samples fully saturated with brine (NaCl solution) and the uniaxial compressive strength (UCS), Brazilian tensile strength, density and porosity values of the samples were determined in the laboratory. The test results were evaluated using simple and multiple regression analysis. It was seen that the UCS and tensile strength values were linearly correlated with the electrical resistivity. The correlation coefficients are generally higher for the multiple regression models than that of the simple regression models. It was concluded that the UCS and tensile strength of igneous rocks can be estimated from electrical resistivity. However, the derived relations are purely empirical and they should be checked for other igneous rocks. The effect of rock types such as sedimentary and metamorphic rocks on the derived equations also needs to be investigated.

  11. Development of optimization models for the set behavior and compressive strength of sodium activated geopolymer pastes

    Science.gov (United States)

    Fillenwarth, Brian Albert

    As large countries such as China begin to industrialize and concerns about global warming continue to grow, there is an increasing need for more environmentally friendly building materials. One promising material known as a geopolymer can be used as a portland cement replacement and in this capacity emits around 67% less carbon dioxide. In addition to potentially reducing carbon emissions, geopolymers can be synthesized with many industrial waste products such as fly ash. Although the benefits of geopolymers are substantial, there are a few difficulties with designing geopolymer mixes which have hindered widespread commercialization of the material. One such difficulty is the high variability of the materials used for their synthesis. In addition to this, interrelationships between mix design variables and how these interrelationships impact the set behavior and compressive strength are not well understood. A third complicating factor with designing geopolymer mixes is that the role of calcium in these systems is not well understood. In order to overcome these barriers, this study developed predictive optimization models through the use of genetic programming with experimentally collected set times and compressive strengths of several geopolymer paste mixes. The developed set behavior models were shown to predict the correct set behavior from the mix design over 85% of the time. The strength optimization model was shown to be capable of predicting compressive strengths of geopolymer pastes from their mix design to within about 1 ksi of their actual strength. In addition to this the optimization models give valuable insight into the key factors influencing strength development as well as the key factors responsible for flash set and long set behaviors in geopolymer pastes. A method for designing geopolymer paste mixes was developed from the generated optimization models. This design method provides an invaluable tool for use in future geopolymer research as well as

  12. ON RESIDUAL COMPRESSIVE STRENGTH PREDICTION OF COMPOSITE SANDWICH PANELS AFTER LOW-VELOCITY IMPACT DAMAGE

    Institute of Scientific and Technical Information of China (English)

    Xie Zonghong; Anthony J. Vizzini; Tang Qingru

    2006-01-01

    This paper introduces a nonlinear finite element analysis on damage propagation behavior of composite sandwich panels under in-plane uniaxial quasi-static compression after a low velocity impact. The major damage modes due to the impact, including the residual indentation on the impacted facesheet, the initially crushed core under the impacted area, and the delamination are incorporated into the model. A consequential core crushing mechanism is incorporated intothe analysis by using an element deactivation technique. Damage propagation behavior, which corresponds to those observed in sandwich compression after impact (SCAI) tests, has been successfully captured in the numerical simulation. The critical far field stress corresponding to the onset of damage propagation at specified critical locations near the damage zone are captured successfully. They show a good correlation with experimental data. These values can be used to effectively predict the residual compressive strength of low-velocity impact damaged composite sandwich panels.

  13. Predicting Concrete Compressive Strength and Modulus of Rupture Using Different NDT Techniques

    Directory of Open Access Journals (Sweden)

    Wilfrido Martínez-Molina

    2014-01-01

    Full Text Available Quality tests applied to hydraulic concrete such as compressive, tension, and bending strength are used to guarantee proper characteristics of materials. All these assessments are performed by destructive tests (DTs. The trend is to carry out quality analysis using nondestructive tests (NDTs as has been widely used for decades. This paper proposes a framework for predicting concrete compressive strength and modulus of rupture by combining data from four NDTs: electrical resistivity, ultrasonic pulse velocity, resonant frequency, and hammer test rebound with DTs data. The model, determined from the multiple linear regression technique, produces accurate indicators predictions and categorizes the importance of each NDT estimate. However, the model is identified from all the possible linear combinations of the available NDT, and it was selected using a cross-validation technique. Furthermore, the generality of the model was assessed by comparing results from additional specimens fabricated afterwards.

  14. Use of triangular membership function for prediction of compressive strength of concrete containing nanosilica

    Directory of Open Access Journals (Sweden)

    Sakshi Gupta

    2015-12-01

    Full Text Available In this paper, application of fuzzy logic technique using triangular membership function for developing models for predicting compressive strength of concrete with partial replacement of cement with nanosilica has been carried out. For this, the data have been taken from various literatures and help in optimizing the constituents available and reducing cost and efforts in studying design to develop mixes by predefining suitable range for experimenting. The use of nanostructured materials in concrete can add many benefits that are directly related to the durability of various cementitious materials, besides the fact that it is possible to reduce the quantities of cement in the composite. Successful prediction by the model indicates that fuzzy logic could be a useful modelling tool for engineers and research scientists in the area of cement and concrete. Compressive strength values of concrete can be predicted in fuzzy logic models without attempting any experiments in a quite short period of time with tiny error rates.

  15. Analysis of the Flexure Behavior and Compressive Strength of Fly Ash Core Sandwiched Composite Material

    Directory of Open Access Journals (Sweden)

    Vijaykumar H.K

    2014-07-01

    Full Text Available In this paper, commercially available Fly Ash and Epoxy is used for the core material, woven glass fabric as reinforcing skin material, epoxy as matrix/adhesive materials used in this study for the construction of sandwich composite. Analysis is carried out on different proportions of epoxy and fly ash sandwiched composite material for determining the flexural strength and compressive strength, three different proportions of epoxy and fly ash used for the study. Those are 65%-35% (65% by weight fly ash and 35% by weight epoxy resin composite material, 60%-40% and 55%-45% composite material. 60%-40% composite material specimen shows better results in the entire test carried out i.e. Flexure and Compression. The complete experimental results are discussed and presented in this paper.

  16. Tensile strength and internal stress determination in salt compacts by diametrical and axial compression tests

    International Nuclear Information System (INIS)

    Due to the brittle character of the material an indirect method (diametrical and axial compression testing) was adopted for tensile strength determination. Two lots of compacts were prepared from salt powder, by pressing it in steel dyes by means of a hydraulic press. For uniaxial tests, cylindrical compacts were used. Biaxial tests were done on disk-shaped compacts, each disk having a diametrical V-shaped cut on one of its plane areas. The punches used for compression tests, were designed to obtain a ratio of 1.2 between their curvature radius and sample radius. At the same time with the tensile strength, the stress intensity factor (KIC and KIIC values) has been obtained. The results obtained are in good agreement with the mechanical properties of the salt, previously reported. (Authors)

  17. Increasing the compressive strength of portland cement concrete using flat glass powder

    Energy Technology Data Exchange (ETDEWEB)

    Miranda Junior, Edson Jansen Pedrosa de; Bezerra, Helton de Jesus Costa Leite; Politi, Flavio Salgado; Paiva, Antonio Ernandes Macedo, E-mail: edson.jansen@ifma.edu.br [Instituto Federal de Educacao, Ciencia e Tecnologia do Maranha (IFMA), Sao Luis, MA (Brazil). Dept. de Mecanica e Materiais

    2014-08-15

    This paper analyzes the compressive strength of Portland cement concrete in response to the incorporation of 5%, 10% and 20% of flat glass powder in place of sand, at w/c (water/cement) ratios of 0.50, 0.55 and 0.58. A statistical analysis of variance (ANOVA) was performed after 7, 14 and 28 days of curing. The compressive strength test results indicate that the concrete containing a w/c ratio of 0.50 can be used for structural applications, regardless of the waste glass content, as can that with a w/c ratio of 0.55 containing 20% of waste glass. We suggest that the use of flat glass powder in place of sand in the above mentioned percentages is feasible for the production of an environmentally appropriate and structurally applicable concrete. However, the concrete's fluidity and void content must be taken into account. (author)

  18. Strength of Tubular Joints Made by Electromagnetic Compression at Quasistatic and Cyclic Loading

    OpenAIRE

    Barreiro, P.; Beerwald, C.; Homberg, W.; Kleiner, M.; Löhe, D.; Marré, M.; Schulze, V.

    2006-01-01

    Electromagnetic compression of tubular profiles with high electrical conductivity is an innovative joining process for lightweight structures. The components are joined using pulsed magnetic fields which apply radial pressures of up to 200 MPa to tubular workpieces, causing a symmetric reduction of the diameter with typical strain rates of up to 10^4 sec^(-1). This process avoids any surface damage of the workpiece because there is no contact between component and forming tool. The strength o...

  19. EXPERIMENTAL STUDY ON EFFECT OF VARIOUS FACTORS ON COMPRESSIVE STRENGTH OF CONCRETE

    Directory of Open Access Journals (Sweden)

    Hanifi BİNİCİ

    2000-03-01

    Full Text Available In this study, the factors affecting at the compressive strength of the concrete were determined. According the result of the test, the quality of concrete, which was used, is very low. Cement, analysis of aggregates for concrete, compacting, mixing placing and curing of concrete, and the techniques of the production of concrete have effected by different ratio of the quality of concrete.

  20. Compressive Strength, Chloride Permeability, and Freeze-Thaw Resistance of MWNT Concretes under Different Chemical Treatments

    OpenAIRE

    Xingang Wang; Inkyu Rhee; Yao Wang; Yunping Xi

    2014-01-01

    This study investigated compressive strength, chloride penetration, and freeze-thaw resistance of multiwalled carbon nanotube (MWNT) concrete. More than 100 cylindrical specimens were used to assess test variables during sensitivity observations, including water-cement ratios (0.75, 0.5, and 0.4) and exposure to chemical agents (including gum arabic, propanol, ethanol, sodium polyacrylate, methylcellulose, sodium dodecyl sulfate, and silane). To determine the adequate sonication time for MWNT...

  1. PENGARUH KETEBALAN SEMEN BASE POLIKARBOKSILAT TERHADAP COMPRESSIVE STRENGTH AMALGAM HIGH COPPER

    OpenAIRE

    Angreani W, Olivia

    2007-01-01

    Amalgam merupakan salah satu bahan restorasi gigi yang populer dan sering digunakan sampai saat ini. Selain kuat menahan daya kunyah, penggunaannya sederhana dan harganya terjangkau. Compressive strength amalgam high copper adalah daya tahan bahan restorasi amalgam high copper terhadap kekuatan tekan sampai bahan tersebut pecah. Semen polikarboksilat dikembangkan pada tahun 1960 oleh Dennis Smith dalam sebuah usaha untuk menghindari kemungkinan kerusakan pulpa yang dihubungkan dengan pH rend...

  2. Uniaxial compressive strength prediction of jet grouting columns using support vector machines

    OpenAIRE

    Tinoco, Joaquim Agostinho Barbosa; Correia, A. Gomes; Cortez, Paulo

    2011-01-01

    Uniaxial compressive strength (UCS) is the mechanical properties currently used in geotechnical works design, namely in jet grouting (JG) treatments. However, when working with this soil improvement technology, due to its inherent geological complexity and high number of variables involved, such design is a hard, perhaps very hard task. To help in such task, a support vector machine (SVM), which is a data mining algorithm particularly adequate to explore high number of complex data, was train...

  3. EFFECT OF NATURAL ZEOLITE ON THE COMPRESSIVE STRENGTH AND FREEZE-THAW RESISTANCE OF PORTLAND CEMENT

    OpenAIRE

    Bayartsetseg, E.; Lkhagvajargal, G.; Batgerel, D.; Sarangerel, D.; Ochirkhuyag, B

    2011-01-01

    Effects of zeolites in various natural deposits as replacement cementing material on mechanical performance of Portland cement were studied. The blended cement pastes with zeolites were cured at room temperature in air for various durations (1, 7 and 28 days). Mechanical performance of the blended cement samples such as setting time, volume of water, compressive strength, normal consistency and freeze-thaw resistance of the mortar are determined. The optimal substitution ratio was 20 wt. % of...

  4. The pore characteristics of geopolymer foam concrete and their impact on the compressive strength and modulus

    Science.gov (United States)

    Zhang, Zuhua; Wang, Hao

    2016-08-01

    The pore characteristics of GFCs manufactured in the laboratory with 0-16% foam additions were examined using image analysis (IA) and vacuum water saturation techniques. The pore size distribution, pore shape and porosity were obtained. The IA method provides a suitable approach to obtain the information of large pores, which are more important in affecting the compressive strength of GFC. By examining the applicability of the existing models of predicting compressive strength of foam concrete, a modified Ryshkevitch’s model is proposed for GFC, in which only the porosity that is contributed by the pores over a critical diameter (>100 μm) is considered. This “critical void model” is shown to have very satisfying prediction capability in the studied range of porosity. A compression-modulus model for Portland cement concrete is recommended for predicting the compression modulus elasticity of GFC. This study confirms that GFC have similar pore structures and mechanical behavior as those Portland cement foam concrete and can be used alternatively in the industry for the construction and insulation purposes.

  5. Determination of dynamic shear strength of 2024 aluminum alloy under shock compression

    Science.gov (United States)

    Zhang, H. S.; Yan, M.; Wang, H. Y.; Shen, L. T.; Dai, L. H.

    2016-04-01

    A series of plate impact shock-reshock and shock-release experiments were conducted by using an one-stage light gas gun to determine the critical shear strength of the 2024 aluminum alloy under shock compression levels ranging from 0.66 to 3.05 GPa in the present study. In the experiments, a dual flyer plate assembly, i.e., the 2024 aluminum alloy flyer backed either by a brass plate or a PMMA plate, was utilized to produce reshock or release wave. The stress profiles of uniaxial plane strain wave propagation in the 2024 aluminum alloy sample under different pre-compressed states were measured by the embedded stress gauges. The stress-strain data at corresponding states were then calculated by a Lagrangian analysis method named as path line method. The critical shear strengths at different stress levels were finally obtained by self-consistent method. The results show that, at the low shock compression level (0.66 to 3.05 GPa), the critical shear strength of the 2024 aluminum alloy cannot be ignored and increases with the increasing longitudinal stress, which may be attributed to rate-dependence and/or pressure dependent yield behavior of the 2024 aluminum alloy.

  6. Superplasticized Portland cement: Production and compressive strength of mortars and concrete

    Energy Technology Data Exchange (ETDEWEB)

    Bouzoubaa, N.; Zhang, M.H.; Malhotra, V.M. [Natural Resources Canada, Ottawa, Ontario (Canada)

    1998-12-01

    This paper deals with the effect of intergrinding different percentages of a naphthalene-based superplasticizer with Portland cement clinker and gypsum on the fineness of the product, and on the water requirement and the compressive strength of the mortars made with the superplasticized cement. The properties of the fresh and hardened concrete made with the superplasticized cements were also investigated. The results showed that the intergrinding of a given amount of a naphthalene-based superplasticizer with Portland clinker and gypsum reduced the grinding time required for obtaining the same Blaine fineness as that of the control Portland cement without the superplasticizer. The water requirement of the mortars made with the superplasticized cements was similar to that of the mortars made with the control Portland cements when the same amount of the superplasticizer was added at the mortar mixer; for a given grinding time and a Blaine fineness of {approximately}4500 cm{sup 2}/g, the mortars made with the superplasticized cement had higher compressive strength than those made with the control Portland cement. For a given grinding time or Blaine fineness of cement {ge}5000 cm{sup 2}/g, the slump loss, air content stability, bleeding, autogenous temperature rise, setting times, and compressive strength of the concrete made with the superplasticized cements were generally comparable to those of the concrete made with the control Portland cements when the superplasticizer was added at the concrete mixer.

  7. Determination of dynamic shear strength of 2024 aluminum alloy under shock compression

    Directory of Open Access Journals (Sweden)

    H. S. Zhang

    2016-04-01

    Full Text Available A series of plate impact shock-reshock and shock-release experiments were conducted by using an one-stage light gas gun to determine the critical shear strength of the 2024 aluminum alloy under shock compression levels ranging from 0.66 to 3.05 GPa in the present study. In the experiments, a dual flyer plate assembly, i.e., the 2024 aluminum alloy flyer backed either by a brass plate or a PMMA plate, was utilized to produce reshock or release wave. The stress profiles of uniaxial plane strain wave propagation in the 2024 aluminum alloy sample under different pre-compressed states were measured by the embedded stress gauges. The stress-strain data at corresponding states were then calculated by a Lagrangian analysis method named as path line method. The critical shear strengths at different stress levels were finally obtained by self-consistent method. The results show that, at the low shock compression level (0.66 to 3.05 GPa, the critical shear strength of the 2024 aluminum alloy cannot be ignored and increases with the increasing longitudinal stress, which may be attributed to rate-dependence and/or pressure dependent yield behavior of the 2024 aluminum alloy.

  8. Investigation of compressive strength of concrete with slag and silica fu

    International Nuclear Information System (INIS)

    Without doubt, concrete has special place in construction of different types of structures, and used as one of the most important materials in construction industry. Today, with development and modernization of human knowledge in construction industry, it is possible to reach high performance concrete. Mechanical properties and durability of high performance concrete is quite better than that of conventional concrete. In present, the use of supplementary cementitious materials, mainly silica fume, fly ash and blast furnace slag has become increasingly common for reasons of economy and technical benefits imparted by these materials. The aim of present research is investigation and comparison compressive strength of concrete specimens due to variation of water to cementitious materials ratio (W/C M), silica fume and slag percent and their proportions as cement replacement. Furthermore, it is intended to determine best combination of these materials with cement in concrete (optimum percent) to reach to maximum compressive strength. In the current study, specimens were made in 0.5,0.4 and 0.3 W/C M ratio contained 0,20,35 and 50 percent of slag as cement replacement, where in each slag replacement percent, 0, 5, 10 and 15 percent of of silica fume were used as cement replacement. Results of the current study show that the combination effect of slag and silica fume replacement in concrete leads to the maximum compressive strength in concrete; also there are some optimum percents for replacement of slag and silica fume to cement to get the best results

  9. Experimental Study on the Compressive Strength of Big Mobility Concrete with Nondestructive Testing Method

    Directory of Open Access Journals (Sweden)

    Huai-Shuai Shang

    2012-01-01

    Full Text Available An experimental study of C20, C25, C30, C40, and C50 big mobility concrete cubes that came from laboratory and construction site was completed. Nondestructive testing (NDT was carried out using impact rebound hammer (IRH techniques to establish a correlation between the compressive strengths and the rebound number. The local curve for measuring strength of the regression method is set up and its superiority is proved. The rebound method presented is simple, quick, and reliable and covers wide ranges of concrete strengths. The rebound method can be easily applied to concrete specimens as well as existing concrete structures. The final results were compared with previous ones from the literature and also with actual results obtained from samples extracted from existing structures.

  10. Standard test method for compressive (crushing) strength of fired whiteware materials

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    1988-01-01

    1.1 This test method covers two test procedures (A and B) for the determination of the compressive strength of fired whiteware materials. 1.2 Procedure A is generally applicable to whiteware products of low- to moderately high-strength levels (up to 150 000 psi or 1030 MPa). 1.3 Procedure B is specifically devised for testing of high-strength ceramics (over 100 000 psi or 690 MPa). 1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

  11. The Value Compressive Strength and Split Tensile Strength on Concrete Mixture With Expanded Polystyrene Coated by Surfactant Span 80 as a Partial Substitution of Fine Aggregate

    Directory of Open Access Journals (Sweden)

    Hidayat Irpan

    2014-03-01

    Full Text Available The value of the density normal concrete which ranges between 2200–2400 kg/m3. Therefore the use of Expanded Polystyrene (EPS as a subitute to fine aggregate can reduce the density of concrete. The purpose this research is to reduce the density of normal concrete but increase compressive strength of EPS concrete, with use surfactant as coating for the EPS. Variables of substitution percentage of EPS and EPS coated by surfactant are 5%,10%,15%,20%,25%. Method of concrete mix design based on SNI 03-2834-2000 “Tata Cara Pembuatan Rencana Campuran Beton Normal (Provisions for Proportioning Normal Concrete Mixture”. The result of testing, every increase percentage of EPS substitution will decrease the compressive strength around 1,74 MPa and decrease density 34,03 kg/m3. Using Surfactant as coating of EPS , compressive strength increase from the EPS’s compressive strength. Average of increasing compressive strength 0,19 MPa and increase the density 20,03 kg/m3,average decrease of the tensile split strength EPS coated surfaktan is 0,84 MPa.

  12. The Value Compressive Strength and Split Tensile Strength on Concrete Mixture With Expanded Polystyrene Coated by Surfactant Span 80 as a Partial Substitution of Fine Aggregate

    Science.gov (United States)

    Hidayat, Irpan; Siauwantara, Alice

    2014-03-01

    The value of the density normal concrete which ranges between 2200-2400 kg/m3. Therefore the use of Expanded Polystyrene (EPS) as a subitute to fine aggregate can reduce the density of concrete. The purpose this research is to reduce the density of normal concrete but increase compressive strength of EPS concrete, with use surfactant as coating for the EPS. Variables of substitution percentage of EPS and EPS coated by surfactant are 5%,10%,15%,20%,25%. Method of concrete mix design based on SNI 03-2834-2000 "Tata Cara Pembuatan Rencana Campuran Beton Normal (Provisions for Proportioning Normal Concrete Mixture)". The result of testing, every increase percentage of EPS substitution will decrease the compressive strength around 1,74 MPa and decrease density 34,03 kg/m3. Using Surfactant as coating of EPS , compressive strength increase from the EPS's compressive strength. Average of increasing compressive strength 0,19 MPa and increase the density 20,03 kg/m3,average decrease of the tensile split strength EPS coated surfaktan is 0,84 MPa.

  13. The influence of dicarboxylic acids: Oxalic acid and tartaric acid on the compressive strength of glass ionomer cements

    Science.gov (United States)

    Permana, Ahmadi Jaya; Setyawati, Harsasi; Hamami, Murwani, Irmina Kris

    2016-03-01

    Glass ionomer cement (GIC) has limitation on the mechanical properties especially compressive strength. The change of compressive strength of GIC by adding oxalic acid and tartaric acid has been investigated. Oxalic acid and tartaric acid was added to the liquid components at concentrations of 0 - 15% (w/w). Powder component of GIC was made from optimum experimental powder glass SiO2-Al2O3-CaF2. GIC was characterized by compressive strength test, SEM-EDX and FTIR. The addition of tartaric acid to GIC has greater improvement than addition of oxalic acid. The addition of tartaric acid at 10 % (w/w) to GIC has greatest value of compressive strength.

  14. Compressive Strength of Steel Frames after Welding with Micro-Jet Cooling

    Directory of Open Access Journals (Sweden)

    Hadryś D.

    2016-03-01

    Full Text Available Low carbon steel weld structures generally exhibit a very linear stress-strain relationship. In the study of strength of materials, the compressive strength is the capacity of a material or structure to withstand loads tending to reduce size of structure. It is mainly measured by plotting applied force against deformation in a testing machine. Compressive strength is a main key value for design of welded structures.The main goal of that paper was analysing of plastic properties of frame welds which were made with various parameters of micro-jet cooling. New technology of micro-jet welding could be regarded as a new way to improve plastic properties of welds. It allows to obtain welds with better mechanical properties in comparison to ordinary welding method. Furthermore it is possible to steering of weld structure and properties of the weld. There were given main information about influence of various micro-jet gases on metallographic and properties of structure steel welds.

  15. Influence of curing regimes on compressive strength of ultra high performance concrete

    Indian Academy of Sciences (India)

    Prabhat Ranjan Prem; B H Bharatkumar; Nagesh R Iyer

    2013-12-01

    The present paper is aimed to identify an efficient curing regime for ultra high performance concrete (UHPC), to achieve a target compressive strength more than 150 MPa, using indigenous materials. The thermal regime plays a vital role due to the limited fineness of ingredients and low water/binder ratio. By activation of the reaction kinetics, the effectiveness of the binder is enhanced which leads to improvements in mechanical as well as durability properties. The curing cycle employed are ambient air curing, water curing and hot air curing. The specimens were exposed to thermal regime at (90°C/150°C/200°C) for duration of 24, 48 or 72 hours at the age of 3rd and 7th day followed with air curing or water curing till 28 days. The results showed a marked difference in compressive strength ranging from 217 to 142 MPa with change in curing regimes. The samples when thermally cured at the age of 3rd and 7th day produced an average ultimate strength of 217–152 MPa and 196–150 MPa, respectively.

  16. A study on the effect of nano silica on compressive strength of high volume fly ash mortars and concretes

    International Nuclear Information System (INIS)

    Highlights: • The addition of NS compensates low early age compressive strength of HVFA system. • NS also contributes to later age compressive strength gain of HVFA system. • The XRD results confirm the reduction of CH in HVFA paste due to addition of NS. - Abstract: This paper presents the effect of nano silica (NS) on the compressive strength of mortars and concretes containing different high volume fly ash (HVFA) contents ranging from 40% to 70% (by weight) as partial replacement of cement. The compressive strength of mortars is measured at 7 and 28 days and that for concretes is measured at 3, 7, 28, 56 and 90 days. The effects of NS in microstructure development and pozzolanic reaction of pastes containing above HVFA contents are also studied through backscattered electron (BSE) image and X-ray diffraction (XRD) analysis. Results show that among different NS contents ranging from 1% to 6%, cement mortar containing 2% NS exhibited highest 7 and 28 days compressive strength. This NS content (2%) is then added to the HVFA mortars and concretes and the results show that the addition of 2% NS improved the early age (7 days) compressive strength of mortars containing 40% and 50% fly ash by 5% and 7%, respectively. However, this improvement is not observed at high fly ash contents beyond 50%. On the other hand, all HVFA mortars exhibited improvement in 28 days compressive strength due to addition of 2% NS and the most significant improvement is noticed in mortars containing more than 50% fly ash. In HVFA concretes, the improvement of early age (3 days) compressive strength is also noticed due to addition of 2% NS. The BSE and XRD analysis results also support the above findings

  17. Investigation of out of plane compressive strength of 3D printed sandwich composites

    Science.gov (United States)

    Dikshit, V.; Yap, Y. L.; Goh, G. D.; Yang, H.; Lim, J. C.; Qi, X.; Yeong, W. Y.; Wei, J.

    2016-07-01

    In this study, the 3D printing technique was utilized to manufacture the sandwich composites. Composite filament fabrication based 3D printer was used to print the face-sheet, and inkjet 3D printer was used to print the sandwich core structure. This work aims to study the compressive failure of the sandwich structure manufactured by using these two manufacturing techniques. Two different types of core structures were investigated with the same type of face-sheet configuration. The core structures were printed using photopolymer, while the face-sheet was made using nylon/glass. The out-of-plane compressive strength of the 3D printed sandwich composite structure has been examined in accordance with ASTM standards C365/C365-M and presented in this paper.

  18. Durability and compressive strength of blast furnace slag-based cement grout for special geotechnical applications

    Directory of Open Access Journals (Sweden)

    Ortega, J. M.

    2014-03-01

    Full Text Available Special foundations, most prominently micropiles and soil anchors, are frequently used in construction today. In Spain, the grout for these special technical applications is generally prepared with portland cement, although the codes and standards in place stipulate only the minimum compressive strength required, with no mention of cement type. Those texts also establish a range of acceptable water:cement ratios. In the present study, durability and compressive strength in cement grout prepared with blast furnace slag cement at different w/c ratios are characterised and compared to the findings for a reference portland cement grout. The results show that slag grout exhibits greater durability than the portland cement material and complies with the compressive strength requirements laid down in the respective codes.Actualmente es muy frecuente el empleo de cimentaciones especiales, entre las que destacan los micropilotes y los anclajes. En España, las lechadas de cemento para estos trabajos geotécnicos especiales se preparan habitualmente con cemento Portland, aunque las diferentes normativas al respecto no restringen el tipo de cemento a emplear, siempre que se alcance una determinada resistencia a compresión. Respecto a la dosificación de las lechadas, la normativa permite emplear diferentes relaciones agua/cemento dentro de un determinado rango. En vista de ello, en este trabajo se han caracterizado las propiedades de durabilidad y resistencia a compresión de lechadas de cemento preparadas con un cemento con escoria de alto horno y con diferentes relaciones a/c, tomando como referencia de comportamiento lechadas de cemento Portland. El uso de un cemento con escoria conlleva una mejora en la durabilidad de las lechadas, cumpliendo los requisitos de resistencia a compresión establecidos por la normativa.

  19. Comparative Evaluation of the Compressive Strength of a Direct Composite Resin and Two Laboratorial Resins

    Directory of Open Access Journals (Sweden)

    Alexandre Costa Reis BRITO

    2007-05-01

    Full Text Available Purpose: To compare the compressive strength of two commercially available laboratorial resins - Solidex® (Shofu and Cristobal® (Dentsply - to that of a direct composite resin (Concept®; Vigodent, as a control group.Method: Five specimens of each tested material were fabricated using stainless steel matrices with the following dimensions: 8 mm of internal diameter on the base, 9 mm of internal diameter on the top and 4 mm of height. The specimens were stored in distilled water for 72 hours and submitted to an axial load by the action of a 2-mm-diameter round-end tip adapted to a universal testing machine (EMIC 500. A 200 kgf load cell was used running at a crosshead speed of 0.5 mm/min. The load and the point of failure were recorded. Results: Means, in kgf, were: Concept® (Ct = 124.26; Cristobal® (C =184.63; Solidex® (S =173.58. Data (means and standard deviations were analyzed statistically by ANOVA and Tukey’s for comparisons among the groups using the SPSS software (version 10.0. Significance level was set at á=0.05 (95%. Concept® presented significantly lower (p<0.05 compressive strength than the other two materials, Cristobal® and Solidex®, which, in turn, did not differ significantly to each other.Conclusion: Cristobal® and Solidex® laboratorial resins did not show significant difference to each other and both presented compressive strength significantly higher than that of Concept® direct resin.

  20. Compressive strength at high temperatures of a concrete made with recycled tire textile and steel fibers

    OpenAIRE

    Santos Cristina Calmeiro; Rodrigues João Paulo C.

    2013-01-01

    This paper presents the results of a research work on the evaluation of the compressive strength at high temperatures of a concrete made with recycled tire steel and textile fibers. It was considered five different concrete compositions, with a water/cement ratio (W/C = 0.43), differ only in the type and amount of fibers. The compositions with smaller amounts of textile fibers were those that gave better results. The compositions with steel fibers showed a less explosive rupture showing the e...

  1. Steelmaking slag as aggregate for mortars: effects of particle dimension on compression strength.

    Science.gov (United States)

    Faraone, Nicola; Tonello, Gabriele; Furlani, Erika; Maschio, Stefano

    2009-11-01

    The present paper reports on the results of some experiments obtained from the production, hydration and subsequent measurement of the mechanical properties of several mortars prepared using a commercial CII/B-LL Portland cement, steelmaking slag, superplasticizer and water. Relevant parameters for the mortar preparation are the weight ratios of cement/water, the weight ratio superplasticizer/cement and between fine and granulated coarse particles. It has been demonstrated that optimisation of such parameters leads to the production of materials with mechanical properties suitable for civil engineering applications. Moreover, materials with improved compressive strength can be prepared by the use of slag containing extensive amounts of large particles.

  2. ALKALI-ACTIVATION KINETICS OF PHOSPHORUS SLAG CEMENT USING COMPRESSIVE STRENGTH DATA

    OpenAIRE

    Hojjatollah Maghsoodloorad; Ali Allahverdi

    2015-01-01

    In this research, through compressive strength data, the order and kinetics of alkali-activation of phosphorus slag activated with two compound activators of NaOH + Na2CO3 and Na2CO3 + Ca(OH)2, has been evaluated. The kinetics and order of alkali activation is a key factor to forecasting the mechanical behavior of alkali activated cement at different curing time and temperatures without carrying out experimental tests. The apparent activation energy was obtained as 35.6 kJ.mol-1 and 60.7 kJ.m...

  3. Compressive strength at high temperatures of a concrete made with recycled tire textile and steel fibers

    Directory of Open Access Journals (Sweden)

    Santos Cristina Calmeiro

    2013-09-01

    Full Text Available This paper presents the results of a research work on the evaluation of the compressive strength at high temperatures of a concrete made with recycled tire steel and textile fibers. It was considered five different concrete compositions, with a water/cement ratio (W/C = 0.43, differ only in the type and amount of fibers. The compositions with smaller amounts of textile fibers were those that gave better results. The compositions with steel fibers showed a less explosive rupture showing the effectiveness of this type of fibers in the spalling and cracking control.

  4. Comparison of Elastic Modulus and Compressive Strength of Ariadent and Harvard Polycarboxylate Cement and Vitremer Resin Modified Glass Ionomer

    Directory of Open Access Journals (Sweden)

    Ahmadian Khoshemehr Leila

    2009-09-01

    Full Text Available Background: Luting agents are used to attach indirect restoration into or on the tooth. Poor mechanical properties of cement may be a cause of fracture of this layer and lead to caries and restoration removal. The purpose of this study was to compare the elastic modulus and compressive strength of Ariadent (A Poly and Harvard polycarboxylate (H Poly cements and Vitremer resin modified glass ionomer (RGl.Materials & Methods: In this experimental study 15 specimens were prepared form each experimental cement in Laboratory of Tehran Oil Refining Company. The cylindrical specimens were compressed in Instron machine after 24 hours. Elastic modulus and compressive strength were calculated from stress/strain curve of each specimen. One way ANOVA and Tukey tests were used for statistical analysis and P values<0.05 were considered to be statistically significant.Results: The mean elastic modulus and mean compressive strength were 2.2 GPa and 87.8MPa in H poly, 2.4 GPa and 56.5 MPa in A Poly, and 0.8GPa and 105.6 MPa in RGI, respectively. Statistical analysis showed that compressive strength and elastic modulus of both polycarboxylate cements were significantly different from hybrid ionomer (P<0.05, but the difference between elastic modulus of two types of polycarboxilate cements was not statistically significant. Compressive strength of two polycarboxilate cements were significantly different (P<0.05. Conclusion: An ideal lutting agent must have the best mechanical properties. Between the tested luttins RGl cement had the lowest elastic modulus and the highest compressive strength, but the A poly cement had the highest elastic modulus and the lowest compressive strength. Therefore none of them was the best.

  5. Ultimate uniaxial compressive strength of stiffened panel with opening under lateral pressure

    Directory of Open Access Journals (Sweden)

    Yu Chang-Li

    2015-06-01

    Full Text Available This paper concentrated on the ultimate uniaxial compressive strength of stiffened panel with opening under lateral load and also studied the design-oriented formulae. For this purpose, three series of well executed experiments on longitudinal stiffened panel with rectangular opening subjected to the combined load have been selected as test models. The finite element analysis package, ABAQUS, is used for simulation with considering the large elasticplastic deflection behavior of stiffened panels. The feasibility of the numerical procedure is verified by a good agreement of experimental results and numerical results. More cases studies are executed employing nonlinear finite element method to analyze the influence of design variables on the ultimate strength of stiffened panel with opening under combined pressure. Based on data, two design formulae corresponding to different opening types are fitted, and accuracy of them is illustrated to demonstrate that they could be applied to basic design of practical engineering structure.

  6. Higher compressive strengths and the Bauschinger effect in conformally passivated copper nanopillars

    International Nuclear Information System (INIS)

    Our current understanding of size-dependent strength in nano- and microscale crystals is centered around the idea that the overall strength is determined by the stress required to propagate dislocation sources. The nature and type of these dislocation sources is the subject of extensive debate, however, one commonality amongst these theories is that the ability of the free surface to absorb dislocations is a necessary condition for transition to a source controlled regime. In this work we demonstrate that atomic layer deposition (ALD) of conformal 5–25 nm thick TiO2/Al2O3 coatings onto electroplated single crystalline copper pillars with diameters ranging from 75 nm to 1 μm generally inhibits the ability of a dislocation to vanish at the free surface. Uniaxial compression tests reveal increased strength and hardening relative to uncoated pillars at equivalent diameters, as well as a notable recovery of plastic strain during unloading, i.e. the Bauschinger effect. Unlike previous reports, these coated pillars retained the stochastic signature in their stress–strain curves. We explain these observations within the framework of a size-dependent strength theory based on a single arm source model, dislocation theory, and microstructural analysis by transmission electron microscopy.

  7. Compressive strength and microstructural characteristics of class C fly ash geopolymer

    Energy Technology Data Exchange (ETDEWEB)

    Xiaolu Guo; Huisheng Shi; Warren A. Dick [Key Laboratory of Advanced Civil Engineering Materials (Tongji University), Shanghai (China)

    2010-02-15

    Geopolymers prepared from a class C fly ash (CFA) and a mixed alkali activator of sodium hydroxide and sodium silicate solution were investigated. A high compressive strength was obtained when the modulus of the activator viz., molar ratio of SiO{sub 2}/Na{sub 2}O was 1.5, and the proper content of this activator as evaluated by the mass proportion of Na{sub 2}O to CFA was 10%. The compressive strength of these samples was 63.4 MPa when they were cured at 75{sup o}C for 8 h followed by curing at 23{sup o}C for 28 d. In FTIR spectroscopy, the main peaks at 1036 and 1400 cm{sup -1} have been attributed to asymmetric stretching of Al-O/Si-O bonds, while those at 747 cm{sup -1} are due to the Si-O-Si/Si-O-Al bending band. The main geopolymeric gel and calcium silicate hydrate (C-S-H) gel co-exist and bond some remaining unreacted CFA spheres as observed in XRD and SEM-EXDA. The presence of gismondine (zeolite) was also observed in the XRD pattern.

  8. Application of alkaliphilic biofilm-forming bacteria to improve compressive strength of cement-sand mortar.

    Science.gov (United States)

    Park, Sung-Jin; Chun, Woo-Young; Kim, Wha-Jung; Ghim, Sa-Youl

    2012-03-01

    The application of microorganisms in the field of construction material is rapidly increasing worldwide; however, almost all studies that were investigated were bacterial sources with mineral-producing activity and not with organic substances. The difference in the efficiency of using bacteria as an organic agent is that it could improve the durability of cement material. This study aimed to assess the use of biofilm-forming microorganisms as binding agents to increase the compressive strength of cement-sand material. We isolated 13 alkaliphilic biofilmforming bacteria (ABB) from a cement tetrapod block in the West Sea, Korea. Using 16S RNA sequence analysis, the ABB were partially identified as Bacillus algicola KNUC501 and Exiguobacterium marinum KNUC513. KNUC513 was selected for further study following analysis of pH and biofilm formation. Cement-sand mortar cubes containing KNUC513 exhibited greater compressive strength than mineral-forming bacteria (Sporosarcina pasteurii and Arthrobacter crystallopoietes KNUC403). To determine the biofilm effect, Dnase I was used to suppress the biofilm formation of KNUC513. Field emission scanning electron microscopy image revealed the direct involvement of organic-inorganic substance in cement-sand mortar.

  9. Effects of Elevated Temperatures on the Compressive Strength Capacity of Concrete Cylinders Confined with FRP Sheets: An Experimental Investigation

    Directory of Open Access Journals (Sweden)

    Sherif El-Gamal

    2015-01-01

    Full Text Available Due to their high strength, corrosion resistance, and durability, fiber reinforced polymers (FRP are very attractive for civil engineering applications. One of these applications is the strengthening of concrete columns with FRP sheets. The performance of this strengthening technique at elevated temperature is still questionable and needs more investigations. This research investigates the effects of exposure to high temperatures on the compressive strength of concrete cylinders wrapped with glass and carbon FRP sheets. Test specimens consisted of 30 unwrapped and 60 wrapped concrete cylinders. All specimens were exposed to temperatures of 100, 200, and 300°C for periods of 1, 2, and 3 hours. The compressive strengths of the unwrapped concrete cylinders were compared with their counterparts of the wrapped cylinders. For the unwrapped cylinders, test results showed that the elevated temperatures considered in this study had almost no effect on their compressive strength; however, the wrapped specimens were significantly affected, especially those wrapped with GFRP sheets. The compressive strength of the wrapped specimens decreased as the exposure period and the temperature level increased. After three hours of exposure to 300°C, a maximum compressive strength loss of about 25.3% and 37.9%, respectively, was recorded in the wrapped CFRP and GFRP specimens.

  10. Dynamics of unconfined spherical flames

    CERN Document Server

    Leblanc, Louis; Dennis, Kadeem; Zhe,; Liang,; Radulescu, Matei I

    2012-01-01

    Using the soap bubble technique, we visualize the dynamics of unconfined hydrogen-air flames using high speed schlieren video. We show that for sufficiently weak mixtures, i.e., low flame speeds, buoyancy effects become important. Flame balls of a critical dimension begin to rise. The experiments are found in very good agreement with the scaling laws proposed by Zingale and Dursi. We report the results in a fluid dynamics video.

  11. The Densification and Diametral Compression Strength of IsiOgwuta Clay

    Directory of Open Access Journals (Sweden)

    J. E. O. Ovri

    2016-07-01

    Full Text Available The diametral compression strength of clay was investigated. The clay sample was analyzed to ascertain its chemical composition and mineralogical constituent. The diametral clay discs were produced using a uniaxial cold pressing hydraulic press and sintered at a predetermined temperature and time (1200℃ and 15 minutes. Two diameters (D of discs of 23mm and 29mm were used with varying thicknesses (3mm-10mm. The effect of disc thickness with intent to qualitatively define the plane stress and the plane strain fracture conditions of the clay was undertaken. The plane stress condition was obtained by discs with thickness ≤ 1 ⁄ 4 D for 23mm and 29mm whilst the plane strain condition was obtained by testing discs of thickness > 1 ⁄ 4 D. The diametral compression strength of discs of thicknesses 3 −10mm gave a range of 14.6− 5.5MPa for samples of 23mm diameter whilst a range of 5.8 − 2.2MPa was obtained for samples of 29mm diameter. Greater numbers of 29mm diameter samples failed in the normal tensile fracture mode whilst more samples of 23mm diameter failed in the triple-cleft fracture mode. 23mm diameter discs gave higher values of Weibull moduli in comparison with the values obtained for discs of 29mm diameter indicating the flaws sampled in the 23mm diameter were of the same severity. Pores were observed to be singularly effective as initiation sites for failure as shown by the negative slope of the effect of porosity on the strength of clay.

  12. Compressive Strength Evaluation in Brazed ZrO2/Ti6Al4V Joints Using Finite Element Analysis

    Science.gov (United States)

    Sharma, Ashutosh; Kee, Se Ho; Jung, Flora; Heo, Yongku; Jung, Jae Pil

    2016-05-01

    This study aims to synthesize and evaluate the compressive strength of the ZrO2/Ti-6Al-4V joint brazed using an active metal filler Ag-Cu-Sn-Ti, and its application to dental implants assuring its reliability to resist the compressive failure in the actual oral environment. The brazing was performed at a temperature of 750 °C for 30 min in a vacuum furnace under 5 × 10-6 Torr atmosphere. The microstructure of the brazed joint showed the presence of an Ag-rich matrix and a Cu-rich phase, and Cu-Ti intermetallic compounds were observed along the Ti-6Al-4V bonded interface. The compressive strength of the brazed ZrO2/Ti-6Al-4V joint was measured by EN ISO 14801 standard test method. The measured compressive strength of the joint was ~1477 MPa—a value almost five times that of existing dental cements. Finite element analysis also confirmed the high von Mises stress values. The compressive strains in the samples were found concentrated near the Ti-6Al-4V position, matching with the position of the real fractured sample. These results suggest extremely significant compressive strength in ZrO2/Ti-6Al-4V joints using the Ag-Cu-Sn-Ti filler. It is believed that a highly reliable dental implant can be processed and designed using the results of this study.

  13. Ultimate tensile strength testing campaign on ITER pre-compression ring mock-ups

    Energy Technology Data Exchange (ETDEWEB)

    Rossi, Paolo, E-mail: paolo.rossi@enea.it [Associazione EURATOM-ENEA sulla Fusione, C.R. Frascati, C.P. 65, 00044 Frascati (Rome) (Italy); Capobianchi, Mario; Crescenzi, Fabio; Massimi, Alberto; Mugnaini, Giampiero; Nardi, Claudio; Pizzuto, Aldo [Associazione EURATOM-ENEA sulla Fusione, C.R. Frascati, C.P. 65, 00044 Frascati (Rome) (Italy); Bettinali, Livio [Consorzio CREATE, Via Claudio 21, 80125 Napoli (Italy); Knaster, Juan [ITER, Route de Vinon-sur-Verdon CS 90 046, 13067, St. Paul-lez-Durance Cedex (France); Rajainmaki, Hannu [FUSION FOR ENERGY, Josep Pla no 2, Torres Diagonal Litoral Edificio B3, 08019 Barcelona (Spain); Evans, David [Advanced Cryogenic Materials, Abingdon, Oxon (United Kingdom)

    2011-10-15

    ENEA has developed and characterized a high strength glass fibre-epoxy composite as reference material for the manufacture of the two sets of 3 pre-compression rings located at top and bottom of the inner straight leg region of the ITER Toroidal Field (TF) coils. These rings will provide a radial force of about 70 MN/coil at cryogenic temperature pulling the TF coils into contact and reducing toroidal tension in the four outer intercoil structures. The paper describes the ultimate tensile strength (UTS) testing campaign carried out at ENEA Frascati laboratories on six different rings manufactured winding S2 glass fibers on a diameter of 1 m (1/5 of the full scale) by both vacuum pressure epoxy impregnation and filament wet winding techniques. The volumetric glass content was around 70%. The rings were expanded with radial steps of 0.1 mm into a dedicated hydraulic testing machine consisting of 18 radial actuators working in position control with a total capability of 1000 tons. All the mock-ups showed very high tensile strength (1550 MPa is the average of the mean hoop stresses at failure) and a practically constant tensile modulus. The test results are reported and discussed.

  14. Strength Studies of Dadri Fly Ash Modified with Lime Sludge – A Composite Material

    Directory of Open Access Journals (Sweden)

    Vaishali Sahu

    2014-07-01

    Full Text Available The aim of the present work is to prepare a new type of fly ash–lime sludge composite totally composed with industrial by-products which can be utilized as road construction material. The lime sludge content was varied from 10% to 50% (at an interval of 10% and the various composites were tested for unconfined compressive strength after 7 and 28 days curing period. The mix formula of this composite was optimized based on maximum strength and equal utilization of both the by-products. The composite with optimal mix formula (fly ash/lime sludge =1:1 results in highest strength. This paper outlines the characteristics of fly ash and lime sludge, method of preparation of compaction specimen and unconfined compression test specimen, testing procedure and salient results thereof. The strength formation mechanism of this composite is discussed. This composite can be further engineered as road construction material with competitive properties.

  15. Electrical impedance spectroscopy measurements to estimate the uniaxial compressive strength of a fault breccia

    Indian Academy of Sciences (India)

    Sair Kahraman; Michael Alber

    2014-10-01

    Fault breccias are usually not suitable for preparing smooth specimens or else the preparation of such specimens is tedious, time consuming and expensive. To develop a predictive model for the uniaxial compressive strength (UCS) of a fault breccia from electrical resistivity values obtained from the electrical impedance spectroscopy measurements, twenty-four samples of a fault breccia were tested in the laboratory. The UCS values were correlated with corresponding resistivity values and a strong correlation between them could not be found. However, a strong correlation was found for the samples having volumetric block proportion (VBP) of 25–75%. In addition, it was seen that VBP strongly correlated with resistivity. It was concluded that the UCS of the tested breccia can be estimated from resistivity for the samples having VBP of 25–75%.

  16. Comparison of the compressive strength of impregnated and nonimpregnated eucalyptus subjected to two different pressures and impregnation times

    Directory of Open Access Journals (Sweden)

    Waldemir Rodrigues

    2004-06-01

    Full Text Available The durability of wood is affected by several factors. For this reason, much research has been done on a variety of chemical compounds for impregnating wood, aimed at preserving it while simultaneously improving its properties. Recent studies of the properties of impregnated wood have demonstrated the possibility of substantially improving its mechanical characteristics. Thus, the purpose of this work was to compare the strength to parallel compression of wooden fibers (Eucalyptus grandis, both nonimpregnated and impregnated with a monocomponent resin, from the standpoint of pressure and impregnation time, aiming at its structural utilization. The results demonstrate that the compressive strength of impregnated test specimens is greater than that of nonimpregnated ones, indicating that monocomponent polyurethane resin can be considered suitable for impregnating wood, since it increases the compressive strength of eucalyptus.

  17. Statistical analysis of the effective factors on the 28 days compressive strength and setting time of the concrete

    Directory of Open Access Journals (Sweden)

    Bahador Abolpour

    2015-09-01

    Full Text Available In this study, the effects of various factors (weight fraction of the SiO2, Al2O3, Fe2O3, Na2O, K2O, CaO, MgO, Cl, SO3, and the Blaine of the cement particles on the concrete compressive strength and also initial setting time have been investigated. Compressive strength and setting time tests have been carried out based on DIN standards in this study. Interactions of these factors have been obtained by the use of analysis of variance and regression equations of these factors have been obtained to predict the concrete compressive strength and initial setting time. Also, simple and applicable formulas with less than 6% absolute mean error have been developed using the genetic algorithm to predict these parameters. Finally, the effect of each factor has been investigated when other factors are in their low or high level.

  18. Enhanced densification, strength and molecular mechanisms in shock compressed porous silicon

    Science.gov (United States)

    Lane, J. Matthew D.; Vogler, Tracy J.

    2015-06-01

    In most porous materials, void collapse during shock compression couples mechanical energy to thermal energy. Increased temperature drives up pressures and lowers densities in the final Hugoniot states as compared to full-density samples. Some materials, however, exhibit an anomalous enhanced densification in their Hugoniot states when porosity is introduced. We have recently shown that silicon is such a material, and demonstrated a molecular mechanism for the effect using molecular simulation. We will review results from large-scale non-equilibrium molecular dynamics (NEMD) and Hugoniotstat simulations of shock compressed porous silicon, highlighting the mechanism by which porosity produces local shear which nucleate partial phase transition and localized melting at shock pressures below typical thresholds in these materials. Further, we will characterize the stress states and strength of the material as a function of porosity from 5 to 50 percent and with various porosity microstructures. Sandia National Laboratories is a multi program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  19. The Effect of Different Parameters on the Development of Compressive Strength of Oil Palm Shell Geopolymer Concrete

    Directory of Open Access Journals (Sweden)

    Ramin Hosseini Kupaei

    2014-01-01

    Full Text Available This paper presents the experimental results of an on-going research project on geopolymer lightweight concrete using two locally available waste materials—low calcium fly ash (FA and oil palm shell (OPS—as the binder and lightweight coarse aggregate, respectively. OPS was pretreated with three different alkaline solutions of sodium hydroxide (NaOH, potassium hydroxide, and sodium silicate as well as polyvinyl alcohol (PVA for 30 days; afterwards, oil palm shell geopolymer lightweight concrete (OPSGPC was cast by using both pretreated and untreated OPSs. The effect of these solutions on the water absorption of OPS, and the development of compressive strength in different curing conditions of OPSGPC produced by pretreated OPS were investigated; subsequently the influence of NaOH concentration, alkaline solution to FA ratio (A/FA, and different curing regimes on the compressive strength and density of OPSGPC produced by untreated OPS was inspected. The 24-hour water absorption value for OPS pretreated with 20% and 50% PVA solution was about 4% compared to 23% for untreated OPS. OPSGPC produced from OPS treated with 50% PVA solution produced the highest compressive strength of about 30 MPa in ambient cured condition. The pretreatment with alkaline solution did not have a significant positive effect on the water absorption of OPS aggregate and the compressive strength of OPSGPC. The result revealed that a maximum compressive strength of 32 MPa could be obtained at a temperature of 65°C and curing period of 4 days. This investigation also found that an A/FA ratio of 0.45 has the optimum amount of alkaline liquid and it resulted in the highest level of compressive strength.

  20. The effect of different parameters on the development of compressive strength of oil palm shell geopolymer concrete.

    Science.gov (United States)

    Kupaei, Ramin Hosseini; Alengaram, U Johnson; Jumaat, Mohd Zamin

    2014-01-01

    This paper presents the experimental results of an on-going research project on geopolymer lightweight concrete using two locally available waste materials--low calcium fly ash (FA) and oil palm shell (OPS)--as the binder and lightweight coarse aggregate, respectively. OPS was pretreated with three different alkaline solutions of sodium hydroxide (NaOH), potassium hydroxide, and sodium silicate as well as polyvinyl alcohol (PVA) for 30 days; afterwards, oil palm shell geopolymer lightweight concrete (OPSGPC) was cast by using both pretreated and untreated OPSs. The effect of these solutions on the water absorption of OPS, and the development of compressive strength in different curing conditions of OPSGPC produced by pretreated OPS were investigated; subsequently the influence of NaOH concentration, alkaline solution to FA ratio (A/FA), and different curing regimes on the compressive strength and density of OPSGPC produced by untreated OPS was inspected. The 24-hour water absorption value for OPS pretreated with 20% and 50% PVA solution was about 4% compared to 23% for untreated OPS. OPSGPC produced from OPS treated with 50% PVA solution produced the highest compressive strength of about 30 MPa in ambient cured condition. The pretreatment with alkaline solution did not have a significant positive effect on the water absorption of OPS aggregate and the compressive strength of OPSGPC. The result revealed that a maximum compressive strength of 32 MPa could be obtained at a temperature of 65°C and curing period of 4 days. This investigation also found that an A/FA ratio of 0.45 has the optimum amount of alkaline liquid and it resulted in the highest level of compressive strength.

  1. Effects of Nanosilica on Compressive Strength and Durability Properties of Concrete with Different Water to Binder Ratios

    OpenAIRE

    Forood Torabian Isfahani; Elena Redaelli; Federica Lollini; Weiwen Li; Luca Bertolini

    2016-01-01

    The effects of the addition of different nanosilica dosages (0.5%, 1%, and 1.5% with respect to cement) on compressive strength and durability properties of concrete with water/binder ratios 0.65, 0.55, and 0.5 were investigated. Water sorptivity, apparent chloride diffusion coefficient, electrical resistivity, and carbonation coefficient of concrete were measured. The results showed that compressive strength significantly improved in case of water/binder = 0.65, while for water/binder = 0.5 ...

  2. Experiments on the enhancement of compressible mixing via streamwise vorticity. II - Vortex strength assessment and seed particle dynamics

    Science.gov (United States)

    Naughton, J. W.; Cattafesta, L. N.; Settles, G. S.

    1993-01-01

    The effect of streamwise vorticity on compressible axisymmetric mixing layers is examined using vortex strength assessment and seed particle dynamics analysis. Experimental results indicate that the particles faithfully represent the dynamics of the turbulent swirling flow. A comparison of the previously determined mixing layer growth rates with the present vortex strength data reveals that the increase of turbulent mixing up to 60 percent scales with the degree of swirl. The mixing enhancement appears to be independent of the compressibility level of the mixing layer.

  3. Compressive strength and frost heave resistance of different types of semi-rigid base materials after freeze-thaw cycles

    Institute of Scientific and Technical Information of China (English)

    ZhenYa Liu; JingYu Liu; QingZhi Wang; JianKun Liu

    2015-01-01

    Freeze-thaw damage is the most common disease of semi-rigid bases in cold regions, which may greatly affect the dura-bility of roadways. In this study, the compressive strength and frost resistance of four different types of semi-rigid bases (lime-fly ash-stabilized sand, cement-stabilized sand, lime-fly ash-stabilized gravel, and cement-stabilized gravel) are assessed by varying the materials content. Based on freeze-thaw and compressive strength tests, this paper presents the performance of the different materials, each having different physical properties, and the optimal amounts of materials contents are proposed.

  4. Statistical analysis of the effective factors on the 28 days compressive strength and setting time of the concrete

    OpenAIRE

    Bahador Abolpour; Mohammad Mehdi Afsahi; Saeed Gharib Hosseini

    2015-01-01

    In this study, the effects of various factors (weight fraction of the SiO2, Al2O3, Fe2O3, Na2O, K2O, CaO, MgO, Cl, SO3, and the Blaine of the cement particles) on the concrete compressive strength and also initial setting time have been investigated. Compressive strength and setting time tests have been carried out based on DIN standards in this study. Interactions of these factors have been obtained by the use of analysis of variance and regression equations of these factors have been obtain...

  5. Statistical analysis of the effective factors on the 28 days compressive strength and setting time of the concrete

    OpenAIRE

    Abolpour, Bahador; Mehdi Afsahi, Mohammad; Hosseini, Saeed Gharib

    2014-01-01

    In this study, the effects of various factors (weight fraction of the SiO2, Al2O3, Fe2O3, Na2O, K2O, CaO, MgO, Cl, SO3, and the Blaine of the cement particles) on the concrete compressive strength and also initial setting time have been investigated. Compressive strength and setting time tests have been carried out based on DIN standards in this study. Interactions of these factors have been obtained by the use of analysis of variance and regression equations of these factors have been obtain...

  6. Compressive Strength and Water Permeability Performance of Micronised Biomass Silica Concrete

    Directory of Open Access Journals (Sweden)

    S.H. Adnan

    2009-12-01

    Full Text Available Concrete is a common material that is widely used in construction industry. Cement is the main material component for producing concrete but its production has lead into CO2 emission. This work presents a study on Micronised Biomass Silica (MBS that can be used as pozzolan material which can enhance the quality of concrete. The material can be produced from a by-product of biomass agricultural waste but for this study rice husk has been used. From the chemical analysis, MBS has a chemical composition that is fulfill the standard requirement for becoming pozzolan material. The result of MBS concrete shows that the MBS material can enhance the performance of concrete by increasing the compressive strength development and reducing the water permeability. The drawback of MBS is the workability of fresh concrete but can be rectify by using superplasticizer. By replacing up to 12% of cement, MBS material gives the highest performance in term of strength and permeability of the concrete.

  7. Formulation of Reduction Rate for Ultimate Compressive Strength of Stiffened Panel Induced by Opening

    Institute of Scientific and Technical Information of China (English)

    于昌利; LEE Joo-sung

    2014-01-01

    The-main-objective-of-this-study-is-to-numerically-investigate-the-characteristics-of-ultimate-compressive-strength-of-stiffened-panels-with-opening-and-also-to-fit-the-design-oriented-formulae.-For-this-purpose,-three-series-of-well-executed-experimental-data-on-longitudinally-stiffened-steel-plates-with-and-without-opening-subjected-to-the-uniform-axial-in-pane-load-which-is-carried-out-to-study-the-buckling-and-post-buckling-up-to-the-final-failure-are-chosen.-Also,-a-nonlinear-finite-element-method-capable-of-efficiently-analyzing-the-large-elasto-plastic-deflection-behavior-of-stiffened-panels-is-developed-and-used-for-simulation.-The-feasibility-of-the-present-simulation-process-is-confirmed-by-a-good-agreement-with-the-experimental-results.-More-case-studies-are-developed-employing-the-simulation-process-to-analyze-the-influence-of-various-design-variables-on-the-reduction-rate-of-ultimate-strength-of-stiffened-panel-induced-by-opening.-Based-on-the-computed-results,-two-design-formulae-are-fitted-and-the-accuracy-of-design-formulae-is-studied.-Furthermore,-the-viability-of-the-design-formulae-for-practical-engineering-is-proved.

  8. THE INFLUENCE OF SATURATION ON THE UNIAXIAL COMPRESSIVE STRENGTH OF LIMESTONE IN EXPLORATION AREA CRNOGLAV NEAR NEUM

    OpenAIRE

    Zlatko Briševac; Trpimir Kujundžić; Borna Jutriša

    2014-01-01

    Exploration area Crnoglav, near Neum, Bosnia and Herzegovina, is composed of limestone sedimentary rock. Research of influence of saturation with water was made on intact material from this area on physical and mechanical properties of the rock: uniaxial compressive strength, module of deformation, point load strength index and Schmidt rebound hardness. Tests were conducted on recommendation of International Society for Rock Mechanics (ISRM Suggested methods) and Croatian Standards. Results s...

  9. A comparative study for the concrete compressive strength estimation using neural network and neuro-fuzzy modelling approaches

    Science.gov (United States)

    Bilgehan, Mahmut

    2011-03-01

    In this paper, adaptive neuro-fuzzy inference system (ANFIS) and artificial neural network (ANN) model have been successfully used for the evaluation of relationships between concrete compressive strength and ultrasonic pulse velocity (UPV) values using the experimental data obtained from many cores taken from different reinforced concrete structures having different ages and unknown ratios of concrete mixtures. A comparative study is made using the neural nets and neuro-fuzzy (NF) techniques. Statistic measures were used to evaluate the performance of the models. Comparing of the results, it is found that the proposed ANFIS architecture with Gaussian membership function is found to perform better than the multilayer feed-forward ANN learning by backpropagation algorithm. The final results show that especially the ANFIS modelling may constitute an efficient tool for prediction of the concrete compressive strength. Architectures of the ANFIS and neural network established in the current study perform sufficiently in the estimation of concrete compressive strength, and particularly ANFIS model estimates closely follow the desired values. Both ANFIS and ANN techniques can be used in conditions where too many structures are to be examined in a restricted time. The presented approaches enable to practically find concrete strengths in the existing reinforced concrete structures, whose records of concrete mixture ratios are not available or present. Thus, researchers can easily evaluate the compressive strength of concrete specimens using UPV and density values. These methods also contribute to a remarkable reduction in the computational time without any significant loss of accuracy. A comparison of the results clearly shows that particularly the NF approach can be used effectively to predict the compressive strength of concrete using UPV and density values. In addition, these model architectures can be used as a nondestructive procedure for health monitoring of

  10. Improving the standard of the standard for glass ionomers: an alternative to the compressive fracture strength test for consideration?

    LENUS (Irish Health Repository)

    Dowling, Adam H

    2012-03-01

    Three strength tests (compressive, three point flexure and biaxial) were performed on three glass ionomer (GI) restoratives to assess the most appropriate methodology in terms of validity and reliability. The influence of mixing induced variability on the data sets generated were eliminated by using encapsulated GIs.

  11. EFFECT OF SODIUM HYDROXIDE CONCENTRATION ON FRESH PROPERTIES AND COMPRESSIVE STRENGTH OF SELF-COMPACTING GEOPOLYMER CONCRETE

    Directory of Open Access Journals (Sweden)

    FAREED AHMED MEMON

    2013-02-01

    Full Text Available This paper reports the results of the laboratory tests conducted to investigate the effect of sodium hydroxide concentration on the fresh properties and compressive strength of self-compacting geopolymer concrete (SCGC. The experiments were conducted by varying the concentration of sodium hydroxide from 8 M to 14 M. Test methods such as Slump flow, V-Funnel, L-box and J-Ring were used to assess the workability characteristics of SCGC. The test specimens were cured at 70°C for a period of 48 hours and then kept in room temperature until the day of testing. Compressive strength test was carried out at the ages of 1, 3, 7 and 28 days. Test results indicate that concentration variation of sodium hydroxide had least effect on the fresh properties of SCGC. With the increase in sodium hydroxide concentration, the workability of fresh concrete was slightly reduced; however, the corresponding compressive strength was increased. Concrete samples with sodium hydroxide concentration of 12 M produced maximum compressive strength.

  12. Effects of coarse aggregate on compressive strength of dam concrete. Damu concrete no asshuku kyodo ni oyobosu sokotsuzai no eikyo

    Energy Technology Data Exchange (ETDEWEB)

    Umehara, H.; Ueda, M. (Nagoya Inst. of Technology, Nagoya (Japan). Faculty of Engineering); Zhang, J. (Yahagi Construction Ltd., Nagoya (Japan)); Yoshida, H. (Nagoya Inst. of Technology, Nagoya (Japan))

    1992-08-20

    Compressive strength of coarse aggregate as well as the bond between coarse aggregate and cement paste effect the compressive strength of concrete greatly. Furthermore the said bond is affected by the bleeding. Consequently, to grasp the level of the voids, under the bottom of the coarse aggregate, caused by the bleeding is the most important in estimating the compressive strength of concrete. However, the researches by now are almost performed on the specimens with Gmax (maximum size of coarse aggregate) being less than 40 mm, and there is nearly none being carried out on a specimen such as dam concrete comprising Gmax as around 150 mm. Now, in the present study, the mechanism of the deterioration of compressive strength in dam concrete due to the voids under the bottom of coarse aggregate is clarified based on the experiment carried out on the alterations of the size, shape, number. location and surface states of the model coarse aggregate in the prepared model concrete made by mortar with Gmax as more than 80 mm. 16 refs., 9 figs., 5 tabs.

  13. Microstructure, characterizations, functionality and compressive strength of cement-based materials using zinc oxide nanoparticles as an additive

    Energy Technology Data Exchange (ETDEWEB)

    Nochaiya, Thanongsak [Department of Physics, Faculty of Science, Naresuan University, Phitsanulok 65000 (Thailand); Sekine, Yoshika [Department of Chemistry, School of Science, Tokai University, 4-1-1 Kitakaname, Hiratsuka, Kanagawa 259-1292 (Japan); Choopun, Supab [Applied Physics Research Laboratory, Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Chaipanich, Arnon, E-mail: arnon.chaipanich@cmu.ac.th [Advanced Cement-Based Materials Research Unit, Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand)

    2015-05-05

    Highlights: • Nano zinc oxide was used as an additive material. • Microstructure and phase characterization of pastes were characterized using SEM and XRD. • TGA and FTIR were also used to determine the hydration reaction. • Compressive strength of ZnO mixes was found to increase at 28 days. - Abstract: Zinc oxide nanoparticles as a nanophotocatalyst has great potential for self-cleaning applications in concrete structures, its effects on the cement hydration, setting time and compressive strength are also important when using it in practice. This paper reports the effects of zinc oxide nanoparticles, as an additive material, on properties of cement-based materials. Setting time, compressive strength and porosity of mortars were investigated. Microstructure and morphology of pastes were characterized using scanning electron microscope and X-ray diffraction (XRD), respectively. Moreover, thermal gravimetric analysis (TGA) and Fourier-transform infrared spectrometer (FTIR) were also used to determine the hydration reaction. The results show that Portland cement paste with additional ZnO was found to slightly increase the water requirement while the setting time presented prolongation period than the control mix. However, compressive strength of ZnO mixes was found to be higher than that of PC mix up to 15% (at 28 days) via filler effect. Microstructure, XRD and TGA results of ZnO pastes show less hydration products before 28 days but similar at 28 days. In addition, FTIR results confirmed the retardation when ZnO was partially added in Portland cement pastes.

  14. Reaction Degree of Silica Fume and Its Effect on Compressive Strength of Cement-silica Fume Blends

    Institute of Scientific and Technical Information of China (English)

    WANG Xiaojun; PAN Zhigang; ZHU Chengfei; ZHU Hongfei

    2014-01-01

    The compressive strength of the cement-silica fume blends with 5mass%, 10mass%, 20mass%and 30mass%of silica fume and water to binder ratio of 0.28, 0.32 and 0.36 from three days to ninety days were investigated. The reaction degree of silica fume was calculated from the Q4 silica tetrahedron, which was used as a probe obtained from 29Si solid state nuclear magnetic resonance analysis. The flat of compressive strength after 28 days disappeared for blended cement with inereasing reaction degree of silica fume. The compressive strength of the blended cement pastes approached that of P.I. cement pastes after 56 days and exceeded that after 90 days. The addition of silica fume and the w/b ratio of blends are both critical to the reaction degree of silica fume. The appropriate addition of silica fume, high silica fume reaction degree and low w/b ratio are beneficial to the compressive strength of the cement-silica fume blends.

  15. Investigation of test methods for measuring compressive strength and modulus of two-dimensional carbon-carbon composites

    Science.gov (United States)

    Ohlhorst, Craig W.; Sawyer, James Wayne; Yamaki, Y. Robert

    1989-01-01

    An experimental evaluation has been conducted to ascertain the the usefulness of two techniques for measuring in-plane compressive failure strength and modulus in coated and uncoated carbon-carbon composites. The techniques involved testing specimens with potted ends as well as testing them in a novel clamping fixture; specimen shape, length, gage width, and thickness were the test parameters investigated for both coated and uncoated 0/90 deg and +/-45 deg laminates. It is found that specimen shape does not have a significant effect on the measured compressive properties. The potting of specimen ends results in slightly higher measured compressive strengths than those obtained with the new clamping fixture. Comparable modulus values are obtained by both techniques.

  16. Development of a method for evaluating tensile and compressive strengths of discontinuous rock mass considering scale effect

    International Nuclear Information System (INIS)

    The purpose of this research is to develop a method for evaluating tensile and compressive strengths considering scale effect which is an old problem in rock mechanics. The method is based on the results of investigation on geometrical information of discontinuity distribution in rock mass. We created a three-dimensional structural model of rock mass with reference to previous studies. Discontinuities in the 3D model were arranged in the supposed cube which is equal to the size of FEM mesh in stability analysis. We clipped arbitrarily-sized two-dimensional cross-section model from the 3D model and calculated tensile and compressive strengths of the 2D model by the stress analysis method we proposed. The relationship between the strength and the size, or the scale effect can be obtained from the method previously describe. The results of the simulations of the proposed method agree with the past test results that the strength and the rate of change of strength decreases with decreasing scale, and show that the scale effect varies according to conditions of geometrical information of discontinuity, confining stress and compression or tension. (author)

  17. Age- and sex-related regional compressive strength characteristics of human lumbar vertebrae in osteoporosis

    Directory of Open Access Journals (Sweden)

    Márta Kurutz

    2008-12-01

    Full Text Available Márta Kurutz1, Judit Donáth3, Miklós Gálos2, Péter Varga1, Béla Fornet41Department of Structural Mechanics; 2Department of Construction Materials, Budapest University of Technology and Economics, Budapest, Hungary; 3Department of Reumatology, National Institute for Reumatology, Budapest, Hungary; 4Department of Radiology, County Hospital András Jósa, Nyiregyháza, HungaryObjective: To obtain the compressive load bearing and energy absorption capacity of lumbar vertebrae of osteoporotic elderly for the everyday medical praxis in terms of the simple diagnostic data, like computed tomography (CT, densitometry, age, and sex.Methods: Compressive test of 54 osteoporotic cadaver vertebrae L1 and L2, 16 males and 38 females (age range 43–93, mean age 71.6 ± 13.3 years, mean bone mineral density (BMD 0.377 ± 0.089 g/cm2, mean T-score −5.57 ± 0.79, Z-score −4.05 ± 0.77 was investigated. Based on the load-displacement diagrams and the measured geometrical parameters of vertebral bodies, proportional, ultimate and yield stresses and strains, Young’s modulus, ductility and energy absorption capacity were determined. Three vertebral regions were distinguished: superior, central and inferior regions, but certain parameters were calculated for the upper/lower intermediate layers, as well. Cross-sectional areas, and certain bone tissue parameters were determined by image analysis of CT pictures of vertebrae. Sex- and age-related decline functions and trends of strength characteristics were determined.Results: Size-corrected failure load was 15%–25% smaller in women, proportional and ultimate stresses were about 30%–35% smaller for women in any region, and 20%–25% higher in central regions for both sexes. Young’s moduli were about 30% smaller in women in any region, and 20%–25% smaller in the central region for both sexes. Small strains were higher in males, large strains were higher in females, namely, proportional strains were

  18. A Comparative Study on Compressive and Flexural Strength of Concrete Containing Different Admixtures as Partial Replacement of Cement

    Directory of Open Access Journals (Sweden)

    Apoorv Singh

    2014-09-01

    Full Text Available Concrete is the most widely used material in the world today. This paper is about the comparative study of the flexural strength and compressive strength of concrete when different admixtures are used as partial replacement of cement in the concrete mix. The mineral admixtures that are used here are Silica Fume, Rice Husk Ash and Iron slag as partial replacement of cement. All these materials are industrial waste products and are abundantly available nowadays. These materials have high silica content and pozzolanic properties and can be effectively used as a replacement of cement during the formation of High Performance Concrete. Compressive and Flexural strength are the two most important characteristic of concrete and are calculated for the hardened concrete to analyze the load bearing capacity for design purposes. Thus for the effective judgment of type of mineral admixtures to be used a comparative study is very useful.

  19. Comparative experimental study of dynamic compressive strength of mortar with glass and basalt fibres

    Directory of Open Access Journals (Sweden)

    Kruszka Leopold

    2015-01-01

    Full Text Available Specimen reinforced with glass and basalt fibers were prepared using Standard Portland cement (CEM I, 52.5 R as prescribed by EN 197-1 and standard sand, in accordance with EN 196-1. From this cementitious mixture, a reference cement mortar without fibers was first prepared. Compressive strength, modulus of elasticity, and mod of fracture were determined for all specimens. Static and dynamic properties were investigated using Instron testing machine and split Hopkinson pressure bar, respectively. Content of the glass fibers in the mortar does not influence the fracture stress at static loading conditions in a clearly observed way. Moreover at dynamic range 5% content of the fiber results in a significant drop of fracture stress. Analysis of the basalt fibers influence on the fracture stress shows that optimal content of this reinforcement is equal to 3% for both static and dynamic loading conditions. Further increase of the fiber share gives the opposite effect, i.e. drop of the fracture stress.

  20. Effect of Incorporating Nanoporous Metal Phosphate Materials on the Compressive Strength of Portland Cement

    Directory of Open Access Journals (Sweden)

    Glen E. Fryxell

    2008-03-01

    Full Text Available Nanoporous metal phosphate (NP-MPO materials are being developed for removal of contaminant oxyanions (As(OHO32−, CrO42−, and TcO4−, and cations (mercury, cadmium, and lead from water and waste streams. Following sequestration, incorporation of metal laden NP-MPOs as a portion of cement formulation would provide an efficient and low-cost way to immobilize metal laden NP-MPOs in an easily handled waste form suitable for permanent disposal. There are no known investigations regarding the incorporation of NP-MPOs in concrete and the effects imparted on the physical and mechanical properties of concrete. Results of this investigation demonstrated that incorporating of NP-MPO materials requires additional water in the concrete formulation which decreases the compressive strength. Thus, incorporation of NP-MPOs in concrete may not serve as an efficient means for long-term disposal.

  1. Strength properties of soft clay treated with mixture of nano-SiO2 and recycled polyester fiber

    OpenAIRE

    Foad Changizi; Abdolhosein Haddad

    2015-01-01

    This paper investigates the effect of recycled polyester fiber, produced from polyethylene (PET) bottles, in combination with nano-SiO2 as a new stabilizer to improve the mechanical properties of soils. We intend to study the effect of adding nano-SiO2 and recycled polyester fiber on soil engineering properties, especially the shear strength and unconfined compressive strength (UCS), using clayey soil with low liquid limit. Three different combinations of fiber-soil ratios ranging between 0.1...

  2. Relationship Between Compression Strength and Its Microstructure of 5 Axial-Braided Composite

    Institute of Scientific and Technical Information of China (English)

    Yang; Chaokun; Zhu; Jianxun; Jiang; Yun

    2007-01-01

    Compression performance of 5-axial braided composites is observed through compression tests.A mixed model of micro-buckling shear with braided tows web is set up to predict compression stress of braided composite through analyzing three broken modes.Using this mixed model,data from tests indicated that the main parameters effecting the compression properties of braided composite are fiber volume fraction,directional angle,axial-tow volume fraction and diameter of tow.Contributing rate of tows is proposed to describe the compression properties of fibre composites.Optimization geometrical structure of braids can optimize composite properties.

  3. Relationship between Leucite Content and Compressive Strength of K2O-Al2O3-SiO2 System Dental Glass Ceramics

    Institute of Scientific and Technical Information of China (English)

    ZHANG Biao; QIAN Fatang; DUAN Xinglong; WU Bolin

    2009-01-01

    Relationship between leucite content and compressive strength of K2O-Al2O3-SiO2 sys-tem dental glass ceramics were investigated. 10 groups of feedstock powder with different composi-tions were treated according to the same thermal treatment system of leucite micro-crystallization reported in some primary studies. The products of each group were analyzed by X-ray diffractometer,polaring microscope and scanning electronic microscope (SEM), and then the compressive strength was tested by a material testing machine. A direct proportion was found between leucite content and the compressive strength when leucite content was less than 50 vol%, and compressive strength de-creased with the increasing of leucite micro-crystals when leucite content was more than 50vol%, The leucite content has a notable influence on the compressive strength of K2O-Al2O3-SiO2 system dental glass ceramics.

  4. Characteristic compression strength of a brickwork masonry starting from the strength of its components. Experimental verification of analitycal equations of european codes

    Directory of Open Access Journals (Sweden)

    Rolando, A.

    2006-09-01

    Full Text Available In this paper the compression strength of a clay brickwork masonry bound with cement mortar is analyzed. The target is to obtain the characteristic compression strength of unreinforced brickwork masonry. This research try to test the validity of the analytical equations in European codes, comparing the experimental strength with the analytically obtained from the strength of its components (clay brick and cement mortar.En este artículo se analiza la resistencia a compresión de una fábrica de ladrillo cerámico, asentado con mortero de cemento.El objetivo es obtener la resistencia característica a compresión de la fábrica sin armar.La investigación comprueba la fiabilidad de las expresiones analíticas existentes en la normativa europea, comparando la resistencia obtenida experimentalmente con la obtenida analíticamente, a partir de la resistencia de sus componentes (ladrillo cerámico y mortero de cemento.

  5. Effect of Superplasticizer and Extra Water on Workability and Compressive Strength of Self-Compacting Geopolymer Concrete

    Directory of Open Access Journals (Sweden)

    Fareed Ahmed Memon

    2012-03-01

    Full Text Available This study documents the results of an experimental work carried out to investigate the effect of superplasticizer and amount of extra water on strength and workability properties of Fly ash-based Selfcompacting geopolymer concrete. The experiments were conducted by varying the amount of extra water and dosage of superplasticizer. A total of nine mixtures with superplasticizer content varying from 3 to 7% and extra water ranging from 10 to 20% of the mass of fly ash were prepared and tested. The essential workability properties of the freshly prepared concrete such as filling ability, passing ability and segregation resistance were evaluated by using Slump flow, T50 slump flow, V-funnel, L-box and J-ring test methods. The compressive strength tests were carried out at 1, 3, 7 and 28 days. Test results indicated that extra water and superplasticizer are key parameters and play an important role in the development of self-compacting geopolymer concrete. Workability of self-compacting geopolymer concrete was dependent on the amount of extra water and dosage of superplasticizer. With the increase in amount of extra water and superplasticizer, the workability was improved. However, the addition of water beyond 15% resulted in bleeding as well as segregation and decreased the compressive strength of the concrete. The compressive strength of self-compacting geopolymer concrete was significantly decreased as the amount of extra water exceeded 12% by mass of Fly ash.

  6. Influence of Molarity and Chemical Composition on the Development of Compressive Strength in POFA Based Geopolymer Mortar

    Directory of Open Access Journals (Sweden)

    S. M. Alamgir Kabir

    2015-01-01

    Full Text Available The investigation concerns the use of the optimum mix proportion of two locally available pozzolanic waste materials, namely, ground granulated blast furnace slag (GGBS and palm oil fuel ash (POFA, together with metakaolin (MK as binders. In addition, another local waste material, manufactured sand (M-sand, was used as a replacement for conventional sand in the development of green geopolymer mortar. Twenty-four mortar mixtures were designed with varying binder contents and alkaline activators. The oven dry curing was also kept consistent for all the mix proportions at a temperature of 65°C for 24 hours. The highest 28-day compressive strength of about 48 MPa was obtained for the mortar containing 20% of MK, 35% of GGBS, and 45% of POFA. The increment of MK beyond 20% leads to reduction of the compressive strength. The GGBS replacement beyond 35% also reduced the compressive strength. The entire specimen achieved average 80% of the 28-day strength at the age of 3 days. The density decreased with the increase of POFA percentage. The finding of this research by using the combination of MK, GGBS, and POFA as binders to wholly replace conventional ordinary Portland cement would lead to alternate eco-friendly geopolymer matrix.

  7. Modeling compressive strength of recycled aggregate concrete by Artificial Neural Network, Model Tree and Non-linear Regression

    Directory of Open Access Journals (Sweden)

    Neela Deshpande

    2014-12-01

    Full Text Available In the recent past Artificial Neural Networks (ANN have emerged out as a promising technique for predicting compressive strength of concrete. In the present study back propagation was used to predict the 28 day compressive strength of recycled aggregate concrete (RAC along with two other data driven techniques namely Model Tree (MT and Non-linear Regression (NLR. Recycled aggregate is the current need of the hour owing to its environmental friendly aspect of re-use of the construction waste. The study observed that, prediction of 28 day compressive strength of RAC was done better by ANN than NLR and MT. The input parameters were cubic meter proportions of Cement, Natural fine aggregate, Natural coarse Aggregates, recycled aggregates, Admixture and Water (also called as raw data. The study also concluded that ANN performs better when non-dimensional parameters like Sand–Aggregate ratio, Water–total materials ratio, Aggregate–Cement ratio, Water–Cement ratio and Replacement ratio of natural aggregates by recycled aggregates, were used as additional input parameters. Study of each network developed using raw data and each non dimensional parameter facilitated in studying the impact of each parameter on the performance of the models developed using ANN, MT and NLR as well as performance of the ANN models developed with limited number of inputs. The results indicate that ANN learn from the examples and grasp the fundamental domain rules governing strength of concrete.

  8. Compressive Strength and Water Absorption of Pervious Concrete that Using the Fragments of Ceramics and Roof Tiles

    Science.gov (United States)

    Prahara, E.; Meilani

    2014-03-01

    Pervious concrete was introduced in America in 2003, popularized by Dan Brown and used as a rigid pavement in the open parking lot. Rigid pavement using pervious concrete can absorb water in the surface to go straight through the concrete to the ground below.This water flow is one of the benefit of using the pervious concrete. Using of wastes such as broken roof and ceramics tiles are not commonly used in Indonesia. Utilization these kind of wastes is predicted lower the compressive strength of pervious concrete as they are used as a substitute for coarse aggregate.In this research, pervious concrete is made using a mixture of the fragment of ceramics and roof tiles.This research using broken ceramics and roof tiles with a grain size that loose from 38 mm sieve, retained on 19 mm sieve and the coarse aggregate from crushed stone that loose 12.5 mm sieve, retained on 9.5 mm sieve. The water cement ratio is 0.3 and to assist the mixing process, the addition of addictive in pervious concrete is used.The size of coarse aggregate used in the mixture affects the strength of pervious concrete. The larger the size of aggregate, the obtained compressive strength becomes smaller. It also affects the density of pervious concrete. The using of mixture of ceramics and roof tiles only reduce 2 MPa of pervious concrete compressive strength so this mixture can be used as a substitute for coarse aggregate with a maximum portion of 30 %. The high porosity of the specimens causes the reduction of pervious concrete density that affect the compressive strength. This high level of porosity can be seen from the high level of water absorption that exceed the required limit of water infiltration.

  9. Compressive Strength and Water Absorption of Pervious Concrete that Using the Fragments of Ceramics and Roof Tiles

    Directory of Open Access Journals (Sweden)

    Prahara E.

    2014-03-01

    Full Text Available Pervious concrete was introduced in America in 2003, popularized by Dan Brown and used as a rigid pavement in the open parking lot. Rigid pavement using pervious concrete can absorb water in the surface to go straight through the concrete to the ground below.This water flow is one of the benefit of using the pervious concrete. Using of wastes such as broken roof and ceramics tiles are not commonly used in Indonesia. Utilization these kind of wastes is predicted lower the compressive strength of pervious concrete as they are used as a substitute for coarse aggregate.In this research, pervious concrete is made using a mixture of the fragment of ceramics and roof tiles.This research using broken ceramics and roof tiles with a grain size that loose from 38 mm sieve, retained on 19 mm sieve and the coarse aggregate from crushed stone that loose 12.5 mm sieve, retained on 9.5 mm sieve. The water cement ratio is 0.3 and to assist the mixing process, the addition of addictive in pervious concrete is used.The size of coarse aggregate used in the mixture affects the strength of pervious concrete. The larger the size of aggregate, the obtained compressive strength becomes smaller. It also affects the density of pervious concrete. The using of mixture of ceramics and roof tiles only reduce 2 MPa of pervious concrete compressive strength so this mixture can be used as a substitute for coarse aggregate with a maximum portion of 30 %. The high porosity of the specimens causes the reduction of pervious concrete density that affect the compressive strength. This high level of porosity can be seen from the high level of water absorption that exceed the required limit of water infiltration.

  10. Injectable porous nano-hydroxyapatite/chitosan/tripolyphosphate scaffolds with improved compressive strength for bone regeneration.

    Science.gov (United States)

    Uswatta, Suren P; Okeke, Israel U; Jayasuriya, Ambalangodage C

    2016-12-01

    In this study we have fabricated porous injectable spherical scaffolds using chitosan biopolymer, sodium tripolyphosphate (TPP) and nano-hydroxyapatite (nHA). TPP was primarily used as an ionic crosslinker to crosslink nHA/chitosan droplets. We hypothesized that incorporating nHA into chitosan could support osteoconduction by emulating the mineralized cortical bone structure, and improve the Ultimate Compressive Strength (UCS) of the scaffolds. We prepared chitosan solutions with 0.5%, 1% and 2% (w/v) nHA concentration and used simple coacervation and lyophilization techniques to obtain spherical scaffolds. Lyophilized spherical scaffolds had a mean diameter of 1.33mm (n=25). Further, portion from each group lyophilized scaffolds were soaked and dried to obtain Lyophilized Soaked and Dried (LSD) scaffolds. LSD scaffolds had a mean diameter of 0.93mm (n=25) which is promising property for the injectability. Scanning Electron Microscopy images showed porous surface morphology and interconnected pore structures inside the scaffolds. Lyophilized and LSD scaffolds had surface pores chitosan LSD scaffolds exhibited UCS of 8.59MPa compared to UCS of 2% nHA/chitosan lyophilized scaffolds at 3.93MPa. Standardize UCS values were 79.98MPa and 357MPa for 2% nHA/chitosan lyophilized and LSD particles respectively. One-way ANOVA results showed a significant increase (pchitosan lyophilized scaffolds compared to 0% and 0.5% nHA/chitosan lyophilized scaffolds. Moreover, 2% nHA LSD scaffolds had significantly increased (pchitosan scaffolds showed higher osteoblast attachment than 0% nHA/chitosan scaffolds. PMID:27612741

  11. Study of the strength of molybdenum under high pressure using electromagnetically applied compression-shear ramp loading

    Science.gov (United States)

    Ding, Jow; Alexander, C. Scott; Asay, James

    2015-06-01

    MAPS (Magnetically Applied Pressure Shear) is a new technique that has the potential to study material strength under mega-bar pressures. By applying a mixed-mode pressure-shear loading and measuring the resultant material responses, the technique provides explicit and direct information on material strength under high pressure. In order to apply sufficient shear traction to the test sample, the driver must have substantial strength. Molybdenum was selected for this reason along with its good electrical conductivity. In this work, the mechanical behavior of molybdenum under MAPS loading was studied. To understand the experimental data, a viscoplasticity model with tension-compression asymmetry was also developed. Through a combination of experimental characterization, model development, and numerical simulation, many unique insights were gained on the inelastic behavior of molybdenum such as the effects of strength on the interplay between longitudinal and shear stresses, potential interaction between the magnetic field and molybdenum strength, and the possible tension-compression asymmetry of the inelastic material response. Sandia National Labs is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corp., for the U.S. Dept. of Energy's National Nuclear Security Administration under Contract DE-AC04-94AL85000.

  12. Effect of Coal Gangue with Different Kaolin Contents on Compressive Strength and Pore Size of Blended Cement Paste

    Institute of Scientific and Technical Information of China (English)

    CHEN Yimin; ZHOU Shuangxi; ZHANG Wensheng

    2008-01-01

    The effects of activated coal gangue on compressive strength,porosity and pore size distribution of hardened cement pastes were investigated.Activated coal gangue with two different kaolin contents,one higher and one lower,were used to partially replace Portland cement at 0%,10%,and 30% by weight.The water to binder ratio(w/b)of 0.5 was used for all the blended cement paste mixes.Experimental results indicate that the blended cement of activated coal gangue mortar with higher kaolin mineral content has a higher compressive strength than that with lower kaolin mineral content.The porosity and pore size of blended cement mortar were significantly affected by the replacement of activated coal gangue.

  13. Analysis of moisture state of recycled coarse aggregate and its influence on compression strength of the concrete

    OpenAIRE

    Pelufo Carbonell, María José; Domingo Cabo, Alberto; Ulloa Mayorga, Vivián Andrea; VERGARA ACUÑA, NEEDY NAYIV

    2009-01-01

    p. 2932-2940 This article analyzes the impact of the moisture level of recycled coarse aggregate additions to concrete on its compression strength, with the goal of finding a logical development process that can be reproduced at an industrial level and provide acceptable results for concrete production. This study takes into account the reality in the process of the production of concrete; while many authors suggest the use of recycled coarse aggregates in a saturated state to ensure the d...

  14. Improvement of linerboard compressive strength by hot-pressing and addition of recovered lignin from spent pulping liquor

    OpenAIRE

    Saidan Motasem N.

    2015-01-01

    This paper evaluates the effect of addition of precipitated lignin, from spent pulping black liquor, to a wet single-ply linerboard handsheet followed by hot-pressing at different temperatures, on the improvement of its compressive strength. Linerboard handsheets for testing the effect of lignin addition were prepared so that the lignin-modified sheets would have the same basis weights as the control handsheets. Both the commercial and the black liquor lign...

  15. Compressive Strength and Hydration Process of Self Compacting Concrete (SCC) mixed with Sea Water, Marine Sand and Portland Composite Cement

    OpenAIRE

    Tjaronge, Wihardi; Irmawaty, Rita

    2014-01-01

    In order to eliminate the main problems of shortage of clean water and fine aggregate in the low land areas and the distant islands, this research utilized sea water and marine sand and Portland composite cement to produce high performance of Self Compacting Concrete (SCC). Portland composite cement containing of fly ash. The evaluation result on the mix design, workability (slumpflow, segregation), mechanical properties (compressive strength-static modulus) and hydration process of SCC were ...

  16. An experimental study of the strength of composite-reinforced beams and bars in transverse bending and axial compression

    Energy Technology Data Exchange (ETDEWEB)

    Dzhankhotov, S.O.; Panfilov, B.V.; Spichkova, L.E.

    1989-01-01

    Experimental data are presented on the strength and fracture characteristics of composite-reinforced beams and short and long bars of aluminum alloys in transverse bending and axial compression. The reinforcement materials include carbon and boron composites with a polymer matrix as well as boron/aluminum. The results demonstrate the effectiveness of using structures reinforced by unidirectional composites. In aerospace applications, the use of composite reinforcements can significantly reduce the weight of structures. 6 refs.

  17. Effects of carbonation on the leachability and compressive strength of cement-solidified and geopolymer-solidified synthetic metal wastes.

    Science.gov (United States)

    Pandey, Bhishan; Kinrade, Stephen D; Catalan, Lionel J J

    2012-06-30

    The effects of accelerated carbonation on the compressive strength and leachability of fly ash-based geopolymer and ordinary portland cement (OPC) doped with Cd(II), Cr(III), Cr(VI), Cu(II), Pb(II) or Zn(II) salts were investigated. Cement was effective at immobilizing Cd, Cr(III), Cu, Pb and Zn under both the Synthetic Precipitation Leaching Procedure (SPLP) and the Toxicity Characteristic Leaching Procedure (TCLP), but ineffective for retaining Cr(VI). Carbonated cement maintained its ability to immobilize Cd, Cr(III), Pb and Zn, but, under acidic TCLP conditions, was much worse at retaining Cu. Geopolymer was effective at immobilizing Cr(III) and Cu, and, to a lesser degree, Cd, Pb and Zn in SPLP leaching tests. Only Cr(III) was immobilized under comparatively acidic TCLP testing conditions. Carbonation did not change the metal retention capacity of the geopolymer matrix. Metal doping caused compressive strengths of both geopolymer and cement to decrease. Carbonation increased the compressive strength of cement, but decreased that of the geopolymer. Geochemical equilibrium modeling provided insight on the mechanisms of metal immobilization.

  18. Study of Compressive Strength of Concrete with Coal Power Plant Fly Ash as Partial Replacement of Cement and Fine Aggregate

    Directory of Open Access Journals (Sweden)

    FAREED AHMED MEMON

    2010-10-01

    Full Text Available This research study comprises of concrete cubes made with Ordinary Portland Cement and with different configurations of fly ash by replacing cement and fine aggregate. To achieve the aim of this study, total 81 concrete cubes were cast. Among 81 cubes, 9 cubes were made with normal concrete, 36 cubes were made by replacing 25%, 50%, 75% and 100% of fine aggregate with fly ash and 36 cubes were made by replacing 10%, 25%, 50%, and 75% of cement with fly ash. The cubes were 6\\" x 6\\" in cross-section, and the mix design was aimed for 5000 psi. After proper curing of all 81 cubes, they were tested at 3, 7 and 28 days curing age. The cubes were tested in Forney Universal Testing Machine. By analyzing the test results of all the concrete cubes, the following main findings have been drawn. The compressive strength of concrete cubes made by replacing 100 % fine aggregate by fly ash was higher than the concrete cubes made with Ordinary Portland Cement at all 3, 7 and 28 days curing ages. On the other hand, the compressive strength of concrete cubes made by replacing 10 % and 25 % cement by fly ash was slightly lower than the concrete cubes made with Ordinary Portland Cement at all curing ages, whereas, the compressive strength of concrete cubes made by replacing 50 % and 75 % of cement by fly ash were quite lower than the concrete cubes made with Ordinary Portland Cement at all curing ages.

  19. Effect of Elevated Temperature and Aggressive Chemical Environment on Compressive Strength of M-30 Grade of Concrete Composite.

    Directory of Open Access Journals (Sweden)

    Chandan Kumar

    2014-05-01

    Full Text Available The present paper reports result of an experimental program conducted to study the behavior of M-30 grade of concrete at elevated temperature on the basis of physical appearance, weight loss and residual compressive strength test. The concrete cubes(M-30 of 150×150×150 mm were cast with a ratio of 1:1.26:2.8 by weight. Three cubeswere tested for compressive strength at the age of 7 days and 28 days by universal testing machine. Then the specimen were subjected to the elevated temperature 200o c, 400o c, 600o c, 800o c and 1000o c in an electric air heated muffle and after cooling were tested for the compressive strength. Six cubes were immersed in each solution of sodium sulphate, sulfuric acid, and sodium chloride for 30 days and 60 days. The testreveal the properties of M-30 concrete and its applicability at elevated temperature and against aggressive environment such as acid attack, sulphate attack and chloride attack. Keywords:

  20. Experimental and statistical study of the influence of broken up particles and air content on the compressive strength of concretes

    International Nuclear Information System (INIS)

    Companies in Algeria have restricted budgets devoted to the formulation of concrete. Therefore, very few research studies are interested by the concrete composition in accordance to its purpose. Hence, this work is a part of an approved research program assigned to clarify the impact of certain parameters on the quality of concrete. This experimental program consists of more than 700 cylindrical specimens of 16x32 cm that were made using local materials. Excluding the durability indicators towards the concrete, the compressive strength is the most significant property to be considered (Mounanga et al., 2006). The obtained results concern consistency and content air propertiesof the concrete at fresh state and compressive strength of hardened concrete at 28 days. Thus, the influence of the air content percentage on the concrete consistency is studied. Moreover, the influence of these two parameters on the compressive strength of the hardened concrete is also presented. The experimental results obtained constitute a data bank, which allows comparing through a statistical analysis, the model established by Feret (Baron and Ollivier, 1996) and the results of the tests. (author)

  1. Investigation of Noise Level and Penetration Rate of Pneumatic Drill vis-à-vis Rock Compressive Strength and Abrasivity

    Science.gov (United States)

    Kivade, S. B.; Murthy, Ch. S. N.; Vardhan, H.

    2014-10-01

    In this paper, detailed studies were carried out to determine the influence of rock properties on the sound level produced during pneumatic drilling. Further, investigation was also carried out on the effect of thrust, air pressure and compressive strength on penetration rate and the sound level produced. For this purpose, a fabricated pneumatic drill set up available in the institute was used. Rock properties, like compressive strength and abrasivity, of various samples collected from the field were determined in the laboratory. Drilling experiments were carried out on ten different rock samples for varying thrust and air pressure values and the corresponding A-weighted equivalent continuous sound levels were measured. It was observed that, very low thrust results in low penetration rate. Even very high thrust does not produce high penetration rate at higher operating air pressures. With increase in thrust beyond the optimum level, the penetration rate starts decreasing and causes the drill bit to `stall'. Results of the study show that penetration rate and sound level increases with increase in the thrust level. After reaching the maximum, they start decreasing despite the increase of thrust. The main purpose of the study is to develop a general prediction model and to investigate the relationships between sound level produced during drilling and physical properties such as uniaxial compressive strength and abrasivity of sedimentary rocks. The results were evaluated using the multiple regression analysis taking into account the interaction effects of predictor variables.

  2. An in vitro study to compare the transverse strength of thermopressed and conventional compression-molded polymethylmethacrylate polymers

    Directory of Open Access Journals (Sweden)

    Anjana Raut

    2013-01-01

    Full Text Available Statement of Problem: Acrylic resins have been in the center stage of Prosthodontics for more than half a century. The flexural fatigue failure of denture base materials is the primary mode of clinical failure. Hence there is a need for superior physical and mechanical properties. Purpose: This in vitro study compared the transverse strength of specimens of thermopressed injection-molded and conventional compression-molded polymethylmethacrylate polymers and examined the morphology and microstructure of fractured acrylic specimens. Materials and Methods: The following denture base resins were examined: Brecrystal (Thermopressed injection-molded, modified polymethylmethacrylate and Pyrax (compression molded, control group. Specimens of each material were tested according to the American Society for Testing and Materials standard D790-03 for flexural strength testing of reinforced plastics and subsequently examined under SEM. The data was analyzed with Student unpaired t test. Results: Flexural strength of Brecrystal (82.08 ± 1.27 MPa was significantly higher than Pyrax (72.76 ± 0.97 MPa. The tested denture base materials fulfilled the requirements regarding flexural strength (>65 MPa. The scanning electron microscopy image of Brecrystal revealed a ductile fracture with crazing. The fracture pattern of control group specimens exhibited poorly defined crystallographic planes with a high degree of disorganization. Conclusion: Flexural strength of Brecrystal was significantly higher than the control group. Brecrystal showed a higher mean transverse strength value of 82.08 ± 1.27 MPa and a more homogenous pattern at microscopic level. Based on flexural strength properties and handling characteristics, Brecrystal may prove to be an useful alternative to conventional denture base resins.

  3. Static compressive strength prediction of open-hole structure based on non-linear shear behavior and micro-mechanics

    Science.gov (United States)

    Li, Wangnan; Cai, Hongneng; Li, Chao

    2014-11-01

    This paper deals with the characterization of the strength of the constituents of carbon fiber reinforced plastic laminate (CFRP), and a prediction of the static compressive strength of open-hole structure of polymer composites. The approach combined with non-linear analysis in macro-level and a linear elastic micromechanical failure analysis in microlevel (non-linear MMF) is proposed to improve the prediction accuracy. A face-centered cubic micromechanics model is constructed to analyze the stresses in fiber and matrix in microlevel. Non-interactive failure criteria are proposed to characterize the strength of fiber and matrix. The non-linear shear behavior of the laminate is studied experimentally, and a novel approach of cubic spline interpolation is used to capture significant non-linear shear behavior of laminate. The user-defined material subroutine UMAT for the non-linear share behavior is developed and combined in the mechanics analysis in the macro-level using the Abaqus Python codes. The failure mechanism and static strength of open-hole compressive (OHC) structure of polymer composites is studied based on non-linear MMF. The UTS50/E51 CFRP is used to demonstrate the application of theory of non-linear MMF.

  4. Effect of shear strength on Hugoniot-compression curve and the equation of state of tungsten (W)

    International Nuclear Information System (INIS)

    The Hugoniot data for highly dense polycrystalline tungsten were obtained for pressures above 200 GPa, and the equation of state (EOS) was determined taking into account shear strength effects. For this study, we have made some improvements in measurement system and analyses of the shock wave data. Symmetric-impact Hugoniot measurements were performed using the high-time resolution streak camera system equipped on a one-stage powder gun and two-stage light gas gun, where the effects of tilting and bowing of flyer plate on the Hugoniot data were carefully considered. The shock velocity–particle velocity (US–UP) Hugoniot relation in the plastic regime was determined to be US = 4.137 + 1.242UP km/s (UP < 2 km/s). Ultrasonic and Velocity Interferometer System for Any Reflector measurements were also performed in this study. The zero-intercept value of the US–UP Hugoniot relation was found to be slightly larger than the ultrasonic bulk sound velocity (4.023 km/s). The hypothetical hydrostatic isothermal Us–Up Hugoniot curve, which corresponds to the hydrostatic isothermal compression curve derived from the Hugoniot data using the strength data, converged to the bulk sound velocity, clearly showing shear strength dependence in the Hugoniot data. The EOS for tungsten is derived from the hydrostatic isothermal compression curve using the strength data

  5. Effects of Nanosilica on Compressive Strength and Durability Properties of Concrete with Different Water to Binder Ratios

    Directory of Open Access Journals (Sweden)

    Forood Torabian Isfahani

    2016-01-01

    Full Text Available The effects of the addition of different nanosilica dosages (0.5%, 1%, and 1.5% with respect to cement on compressive strength and durability properties of concrete with water/binder ratios 0.65, 0.55, and 0.5 were investigated. Water sorptivity, apparent chloride diffusion coefficient, electrical resistivity, and carbonation coefficient of concrete were measured. The results showed that compressive strength significantly improved in case of water/binder = 0.65, while for water/binder = 0.5 no change was found. Increasing nanosilica content, the water sorptivity decreased only for water/binder = 0.55. The addition of 0.5% nanosilica decreased the apparent chloride diffusion coefficient for water/binder = 0.65 and 0.55; however, higher nanosilica dosages did not decrease it with respect to reference value. The resistivity was elevated by 0.5% nanosilica for all water/binder ratios and by 1.5% nanosilica only for water/binder = 0.5. The carbonation coefficient was not notably affected by increasing nanosilica dosages and even adverse effect was observed for water/binder = 0.65. Further information of microstructure was also provided through characterization techniques such as X-ray diffraction, thermal gravimetric analysis, mercury intrusion porosimetry, and scanning electron microscopy. The effectiveness of a certain nanosilica dosage addition into lower strength mixes was more noticeable, while, for the higher strength mix, the effectiveness was less.

  6. Effect of shear strength on Hugoniot-compression curve and the equation of state of tungsten (W)

    Science.gov (United States)

    Mashimo, Tsutomu; Liu, Xun; Kodama, Masao; Zaretsky, Eugene; Katayama, Masahide; Nagayama, Kunihiko

    2016-01-01

    The Hugoniot data for highly dense polycrystalline tungsten were obtained for pressures above 200 GPa, and the equation of state (EOS) was determined taking into account shear strength effects. For this study, we have made some improvements in measurement system and analyses of the shock wave data. Symmetric-impact Hugoniot measurements were performed using the high-time resolution streak camera system equipped on a one-stage powder gun and two-stage light gas gun, where the effects of tilting and bowing of flyer plate on the Hugoniot data were carefully considered. The shock velocity-particle velocity (US-UP) Hugoniot relation in the plastic regime was determined to be US = 4.137 + 1.242UP km/s (UP isothermal compression curve derived from the Hugoniot data using the strength data, converged to the bulk sound velocity, clearly showing shear strength dependence in the Hugoniot data. The EOS for tungsten is derived from the hydrostatic isothermal compression curve using the strength data.

  7. Compression Strength Testing for Automotive Brake Pads Used in Earthquake Energy Dampers

    Directory of Open Access Journals (Sweden)

    Dragoş Voiculescu

    2010-01-01

    Full Text Available In order to calibrate a friction damper which uses automotive brake pads it is necessary to determine the compression behaviour of the friction material. This paper summarizes the experimental results obtained for a set of automotive brake pads made in Romania. These results are useful in order to determine the slip load level in a seismic energy dissipation mechanism which uses this type of friction pads. The paper presents the experimental set up and the compression behaviour curves obtained for a set of four commercial brake pads. The testing was performed by the author as a part of his research work, using a hydraulic compression press.

  8. Effect of Perma-Zyme on Compressive Strength of Compacted Tabia%派酶掺入三合土对土体抗压强度影响的探讨

    Institute of Scientific and Technical Information of China (English)

    彭红涛; 张琪; 李乃胜; 王德发

    2012-01-01

    利用一种生物酶类土壤固化剂——派酶,以适当比例掺入两种配合比的压实三合土中,测得其28 d无侧限抗压强度均比未掺派酶时有所提高.在石灰掺量较高的情况下,掺派酶后三合土土体的28 d无侧限抗压强度仍比未掺派酶时有较大幅度的提高,说明在具有抑制和杀灭细菌的较高碱度环境下,派酶对土体结构的增强作用不是因为其单纯地促进土壤中存在的各种菌类活动所引起的.掺派酶三合土的X射线衍射分析图谱横坐标28°附近位置出现明显超过未掺派酶三合土的强峰,不能排除派酶的掺入会促进土体固化过程中某种晶型变化产生的可能性.SEM显微结构形貌图片显示掺派酶三合土试件的微结构比未掺派酶试件更紧凑、密实.基于分形几何理论研究发现,派酶的掺入促进了三合土土体中细小孔隙增多,大孔隙减少,有利于土体中颗粒间相互作用力的增强.%Two types of compacted tabia were mixed with Perma-zyme in proper proportion. The 28 d un-confined compressive strengths of them were higher than those without Perma-zyme. The 28 d unconfined compressive strength of compacted tabia with Perma-zyme added and higher use level of lime was higher than the others. Strong base environment with high pH value can strain and even kill bacteria. It is indicated that promotion of the soil bacteria to be more activated is not the only factor for Perma-zyme as an enzymatic stabilizer to improve the compressive strength of compacted tabia. The XRD pattern of compacted tabia treated with Perma-zyme shows that there is a stronger diffraction peak than that without Perma-zyme added occurring at near 28℃of abscissa. The possibility of some crystal form changes caused by Perma-zyme in tabia could not be excluded. Scanning electron microscopy revealed that the microstructure of the tabia treated with Perma-zyme became more dense. It is found based on fractal analysis that

  9. Introducing Mg-4Zn-3Gd-1Ca/ZnO nanocomposite with compressive strengths matching/exceeding that of mild steel

    Science.gov (United States)

    Chen, Y.; Tekumalla, S.; Guo, Y. B.; Gupta, M.

    2016-08-01

    This work introduces Mg-4Zn-3Gd-1Ca/2ZnO (wt.%) nanocomposite fabricated using the technique of disintegrated melt deposition and extrusion. Addition of ZnO nanoparticles enhanced the compressive strengths of alloy by ~100 MPa. Nanocomposite samples display high strength and good ductility: 0.2% compressive yield stress of 355 MPa, ultimate compressive stress of 703 MPa, and compressive failure strain of 10.6%. The significant enhancement of compressive yield stress is mainly attributed to the grain refinement by adding nanoparticles. The strength levels exceed that of commercial magnesium alloys (i.e. WE43, WE54, ZK60, and ME21) and mild steels (i.e. S275 and S355), making Mg-4Zn-3Gd-1Ca/2ZnO a very promising material for multiple engineering and biomedical applications.

  10. Statistical Study on Cement-Soil Mixture Strength

    Institute of Scientific and Technical Information of China (English)

    YU Zhiqiang; CAO Yonghua; YAN Shuwang

    2005-01-01

    This paper presents an investigation on strength of cement deep mixing (CDM) mixture. Four typical works of offshore or land-based projects are introduced. With samples from these projects and laboratory tests, statistical analysis is made on the increment law of the strength of cement-soil mixture with different amount of cement, and strengths under different working conditions are compared. It is found that the amount of cement in the cement-soil mixture is closely related to the unconfined compressive strength of the mixture. At the age of 90 d,the unconfined compressive strength of the cement-soil mixture increased by 0.054 Mpa-0.124 Mpa with each cement increasing 10 kg/m3 in the cement-soil mixture, averagely increased by 0.085 Mpa, while that at the age of 120 d increased by 11% in comparison.The quality of the cement-soil mixture should be comprehensively evaluated in accordance with the trimmed average of strength, coefficient of variation and rock quality designation (RQD) indicators of sampling ratio.

  11. Prediction of Compressive Strength of Self compacting Concrete with Flyash and Rice Husk Ash using Adaptive Neuro-fuzzy Inference System

    Directory of Open Access Journals (Sweden)

    S. S, Pathak

    2012-10-01

    Full Text Available Self-compacting concrete is an innovative concrete that does not require vibration for placing and compaction. It is able to flow under its own weight, completely filling formwork and achieving full compaction even in congested reinforcement without segregation and bleeding. In the present study self compacting concrete mixes were developed using blend of fly ash and rice husk ash. Fresh properties of theses mixes were tested by using standards recommended by EFNARC (European Federation for Specialist Construction Chemicals and Concrete system. Compressive strength at 28 days was obtained for these mixes. This paper presents development of Adaptive Neuro-fuzzy Inference System (ANFIS model for predicting compressive strength of self compacting concrete using fly ash and rice husk ash. The input parameters used for model are cement, fly ash, rice husk ash and water content. Output parameter is compressive strength at 28 days. The results show that the implemented model is good at predicting compressive strength.

  12. The influence of poly(acrylic) acid number average molecular weight and concentration in solution on the compressive fracture strength and modulus of a glass-ionomer restorative.

    LENUS (Irish Health Repository)

    Dowling, Adam H

    2011-06-01

    The aim was to investigate the influence of number average molecular weight and concentration of the poly(acrylic) acid (PAA) liquid constituent of a GI restorative on the compressive fracture strength (σ) and modulus (E).

  13. A prediction model for uniaxial compressive strength of deteriorated pyroclastic rocks due to freeze-thaw cycle

    Science.gov (United States)

    İnce, İsmail; Fener, Mustafa

    2016-08-01

    Either directly or indirectly, building stone is exposed to diverse atmospheric interactions depending on the seasonal conditions. Due to those interactions, objects of historic and cultural heritage, as well as modern buildings, partially or completely deteriorate. Among processes involved in rock deterioration, the freeze-thaw (F-T) cycle is one of the most important. Even though pyroclastic rocks have been used as building stone worldwide due to their easy workability, they are the building stone most affected by the F-T cycle. A historical region in Central Anatolia, Turkey, Cappadoia encompasses exceptional natural wonders characterized by fairy chimneys and unique historical and cultural heritage. Human-created caves, places of worship and houses have been dug into the pyroclastic rocks, which have in turn been used in architectural construction as building stone. Using 10 pyroclastic rock samples collected from Cappadocia, we determined the rock's index-mechanical properties to develop a statistical model for estimating percentage loss of uniaxial compressive strength a critical parameter of F-T cycle's important value. We used dry density (ρd), ultrasonic velocity (Vp), point load strengths (IS(50)), and slake-durability test indexes (Id4) values of unweathered rocks in our model, which is highly reliable (R2 = 0.84) for predetermination of percentage loss of uniaxial compressive strengths of pyroclastic rocks without requiring any F-T tests.

  14. Further investigation on the dynamic compressive strength enhancement of concrete-like materials based on split Hopkinson pressure bar tests Part II Numerical Simulations

    OpenAIRE

    Li, Q.M.; Lu, Y.B.; Meng, H.

    2009-01-01

    Abstract Split Hopkinson pressure bars (SHPB) have been used widely to measure the dynamic compressive strength of concrete-like materials at high strain-rate between 101 and 103 s?1. It has been shown in companion paper (Zhang et al. 2009) that the axial strain acceleration is normally unavoidable in an SHPB test on brittle materials. Axial strain acceleration introduces radial confinement in the SHPB specimens and consequently enhances the compressive strength of concrete-like sp...

  15. Evaluation of Compressive Strength and Stiffness of Grouted Soils by Using Elastic Waves

    Directory of Open Access Journals (Sweden)

    In-Mo Lee

    2014-01-01

    Full Text Available Cement grouted soils, which consist of particulate soil media and cementation agents, have been widely used for the improvement of the strength and stiffness of weak ground and for the prevention of the leakage of ground water. The strength, elastic modulus, and Poisson’s ratio of grouted soils have been determined by classical destructive methods. However, the performance of grouted soils depends on several parameters such as the distribution of particle size of the particulate soil media, grouting pressure, curing time, curing method, and ground water flow. In this study, elastic wave velocities are used to estimate the strength and elastic modulus, which are generally obtained by classical strength tests. Nondestructive tests by using elastic waves at small strain are conducted before and during classical strength tests at large strain. The test results are compared to identify correlations between the elastic wave velocity measured at small strain and strength and stiffness measured at large strain. The test results show that the strength and stiffness have exponential relationship with elastic wave velocities. This study demonstrates that nondestructive methods by using elastic waves may significantly improve the strength and stiffness evaluation processes of grouted soils.

  16. Evaluation of compressive strength and stiffness of grouted soils by using elastic waves.

    Science.gov (United States)

    Lee, In-Mo; Kim, Jong-Sun; Yoon, Hyung-Koo; Lee, Jong-Sub

    2014-01-01

    Cement grouted soils, which consist of particulate soil media and cementation agents, have been widely used for the improvement of the strength and stiffness of weak ground and for the prevention of the leakage of ground water. The strength, elastic modulus, and Poisson's ratio of grouted soils have been determined by classical destructive methods. However, the performance of grouted soils depends on several parameters such as the distribution of particle size of the particulate soil media, grouting pressure, curing time, curing method, and ground water flow. In this study, elastic wave velocities are used to estimate the strength and elastic modulus, which are generally obtained by classical strength tests. Nondestructive tests by using elastic waves at small strain are conducted before and during classical strength tests at large strain. The test results are compared to identify correlations between the elastic wave velocity measured at small strain and strength and stiffness measured at large strain. The test results show that the strength and stiffness have exponential relationship with elastic wave velocities. This study demonstrates that nondestructive methods by using elastic waves may significantly improve the strength and stiffness evaluation processes of grouted soils. PMID:25025082

  17. Strength criterion for rocks under compressive-tensile stresses and its application

    Directory of Open Access Journals (Sweden)

    Mingqing You

    2015-08-01

    Full Text Available Estimating in-situ stress with hydraulic borehole fracturing involves tensile strength of rock. Several strength criteria with three parameters result in tensile strengths with great differences, although they may describe the relation between strength of rock and confining pressure with low misfits. The exponential criterion provides acceptable magnitudes of tensile strengths for granites and over-estimates that for other rocks, but the criterion with tension cut-off is applicable to all rocks. The breakdown pressure will be lower than the shut-in pressure during hydraulic borehole fracturing, when the maximum horizontal principal stress is 2 times larger than the minor one; and it is not the peak value in the first cycle, but the point where the slope of pressure-time curve begins to decline.

  18. Theory of DDT in unconfined flames

    CERN Document Server

    Khokhlov, A M; Wheeler, J C; Wheeler, J Craig

    1996-01-01

    This paper outlines a theoretical approach for predicting the onset of detonation in unconfined turbulent flames which is relevant both to problems of terrestrial combustion and to thermonuclear burning in Type Ia supernovae. Two basic assumuptions are made: 1) the gradient mechanism is the inherent mechanism that leads to DDT in unconfined conditions, and 2) the sole mechanism for preparing the gradient in induction time is by turbulent mixing and local flame quenching. The criterion for DDT is derived in terms of the one-dimensional detonation wave thickness, the laminar flame speed, and the laminar flame thickness in the reactive gas. This approach gives a lower-bound criterion for DDT for conditions where shock preheating, wall effects, and interactions with obstacles are absent. Regions in parameter space where unconfined DDT can and cannot occur are determined. A subsequent paper will address these issues specifically in the astrophysical context.

  19. Compressive Strength and Water Absorption of Pervious Concrete that Using the Fragments of Ceramics and Roof Tiles

    OpenAIRE

    Prahara E.; Meilani

    2014-01-01

    Pervious concrete was introduced in America in 2003, popularized by Dan Brown and used as a rigid pavement in the open parking lot. Rigid pavement using pervious concrete can absorb water in the surface to go straight through the concrete to the ground below.This water flow is one of the benefit of using the pervious concrete. Using of wastes such as broken roof and ceramics tiles are not commonly used in Indonesia. Utilization these kind of wastes is predicted lower the compressive strength ...

  20. THE INFLUENCE OF SATURATION ON THE UNIAXIAL COMPRESSIVE STRENGTH OF LIMESTONE IN EXPLORATION AREA CRNOGLAV NEAR NEUM

    Directory of Open Access Journals (Sweden)

    Zlatko Briševac

    2014-12-01

    Full Text Available Exploration area Crnoglav, near Neum, Bosnia and Herzegovina, is composed of limestone sedimentary rock. Research of influence of saturation with water was made on intact material from this area on physical and mechanical properties of the rock: uniaxial compressive strength, module of deformation, point load strength index and Schmidt rebound hardness. Tests were conducted on recommendation of International Society for Rock Mechanics (ISRM Suggested methods and Croatian Standards. Results showed different influence of saturation on values of respective test. Ratios that help with calculations of physical and mechanical properties of rock in their saturated state based on their known values in dry state are presented in this paper (the paper is published in Croatian.

  1. Measurement of In-Plane Shear Strength of Carbon/Carbon Composites by Compression of Double-Notched Specimens

    Science.gov (United States)

    Yan, K. F.; Zhang, C. Y.; Qiao, S. R.; Song, C. Z.; Han, D.; Li, M.

    2012-01-01

    The compression of a double-notched specimen was used to determine the in-plane shear strength (IPSS) of a carbon/carbon composite in the paper. The effects of the notch distance ( L), thickness ( T), and notch width ( W) and supporting jig on the IPSS of the double-notched specimens were investigated numerically and experimentally. The fracture surfaces were examined by a scanning electron microscope. It was found that the IPSS varied with L. Thin specimen yielded low strength. W has little effect on IPSS. The main failure modes include the matrix shear cracking, delamination, fracture and pullout of fibers or fiber bundles. Meanwhile, a supporting jig can provide lateral support and prevent buckling, therefore lead to the failure in a shear mode.

  2. Compressive Strength Prediction of Square Concrete Columns Retrofitted with External Steel Collars

    Directory of Open Access Journals (Sweden)

    Pudjisuryadi, P.

    2013-01-01

    Full Text Available Transverse confining stress in concrete members, commonly provided by transverse reinforcement, has been recognized to enhance strength and ductility. Nowadays, the confining method has been further developed to external confinement approach. This type of confinement can be used for retrofitting existing concrete columns. Many external confining techniques have been proven to be successful in retrofitting circular columns. However, for square or rectangular columns, providing effective confining stress by external retrofitting method is not a simple task due to high stress concentration at column’s corners. This paper proposes an analytical model to predict the peak strength of square concrete columns confined by external steel collars. Comparison with the experimental results showed that the model can predict the peak strength reasonably well. However, it should be noted that relatively larger amount of steel is needed to achieve comparable column strength enhancement when it is compared with those of conve tional internally-confined columns.

  3. STRUCTURAL ASPECTS OF PLASTICITY LOWERING OF HIGH-STRENGTH WIRE AT BIG CUMULATIVE COMPRESSIONS

    Directory of Open Access Journals (Sweden)

    V. P. Fetisov

    2012-01-01

    Full Text Available It is shown that decrease of plasticity of high-strength wire at big total cobbings is connected with reduction of mobility of dislocations in the substructure formed at loss of perlite lamellar structure.

  4. Effect of shear strength on Hugoniot-compression curve and the equation of state of tungsten (W)

    Energy Technology Data Exchange (ETDEWEB)

    Mashimo, Tsutomu, E-mail: mashimo@gpo.kumamoto-u.ac.jp; Liu, Xun [Institute of Pulsed Power Science, Kumamoto University, Kumamoto 860-8555 (Japan); Kodama, Masao [Sojo University, Kumamoto 860-0082 (Japan); Zaretsky, Eugene [Ben-Gurion University of the Negev, P.O. Box 653, Beer Sheva 84105 (Israel); Katayama, Masahide [Itochu Techno-Solutions Corporation, Tokyo 100-6080 (Japan); Nagayama, Kunihiko [Kyushu University, Fukuoka 812-8581 (Japan)

    2016-01-21

    The Hugoniot data for highly dense polycrystalline tungsten were obtained for pressures above 200 GPa, and the equation of state (EOS) was determined taking into account shear strength effects. For this study, we have made some improvements in measurement system and analyses of the shock wave data. Symmetric-impact Hugoniot measurements were performed using the high-time resolution streak camera system equipped on a one-stage powder gun and two-stage light gas gun, where the effects of tilting and bowing of flyer plate on the Hugoniot data were carefully considered. The shock velocity–particle velocity (U{sub S}–U{sub P}) Hugoniot relation in the plastic regime was determined to be U{sub S} = 4.137 + 1.242U{sub P} km/s (U{sub P} < 2 km/s). Ultrasonic and Velocity Interferometer System for Any Reflector measurements were also performed in this study. The zero-intercept value of the U{sub S}–U{sub P} Hugoniot relation was found to be slightly larger than the ultrasonic bulk sound velocity (4.023 km/s). The hypothetical hydrostatic isothermal U{sub s}–U{sub p} Hugoniot curve, which corresponds to the hydrostatic isothermal compression curve derived from the Hugoniot data using the strength data, converged to the bulk sound velocity, clearly showing shear strength dependence in the Hugoniot data. The EOS for tungsten is derived from the hydrostatic isothermal compression curve using the strength data.

  5. Toroidal, compression, and vortical dipole strengths in $^{144-154}$Sm: Skyrme-RPA exploration of deformation effect

    CERN Document Server

    Kvasil, J; Kleinig, W; Bozik, D; Reinhard, P -G; Iudice, N Lo

    2013-01-01

    A comparative analysis of toroidal, compressional and vortical dipole strengths in the spherical $^{144}$Sm and the deformed $^{154}$Sm is performed within the random-phase-approximation using a set of different Skyrme forces. Isoscalar (T=0), isovector (T=1), and electromagnetic excitation channels are considered. The role of the nuclear convection $j_{\\text{con}}$ and magnetization $j_{\\text{mag}}$ currents is inspected. It is shown that the deformation leads to an appreciable redistribution of the strengths and causes a spectacular deformation splitting (exceeding 5 MeV) of the isoscalar compressional mode. In $^{154}$Sm, the $\\mu$=0 and $\\mu$=1 branches of the mode form well separated resonances. When stepping from $^{144}$Sm to $^{154}$Sm, we observe an increase of the toroidal, compression and vortical contributions in the low-energy region (often called pygmy resonance). The strength in this region seems to be an overlap of various excitation modes. The energy centroids of the strengths depend signific...

  6. Multicriteria decision-making analysis based methodology for predicting carbonate rocks' uniaxial compressive strength

    Directory of Open Access Journals (Sweden)

    Ersoy Hakan

    2012-10-01

    Full Text Available

    ABSTRACT

    Uniaxial compressive strength (UCS deals with materials' to ability to withstand axially-directed pushing forces and especially considered to be rock materials' most important mechanical properties. However, the UCS test is an expensive, very time-consuming test to perform in the laboratory and requires high-quality core samples having regular geometry. Empirical equations were thus proposed for predicting UCS as a function of rocks' index properties. Analytical hierarchy process and multiple regression analysis based methodology were used (as opposed to traditional linear regression methods on data-sets obtained from carbonate rocks in NE Turkey. Limestone samples ranging from Devonian to late Cretaceous ages were chosen; travertine-onyx samples were selected from morphological environments considering their surface environmental conditions Test results from experiments carried out on about 250 carbonate rock samples were used in deriving the model. While the hierarchy model focused on determining the most important index properties affecting on UCS, regression analysis established meaningful relationships between UCS and index properties; 0. 85 and 0. 83 positive coefficient correlations between the variables were determined by regression analysis. The methodology provided an appropriate alternative to quantitative estimation of UCS and avoided the need for tedious and time consuming laboratory testing


    RESUMEN

    La resistencia a la compresión uniaxial (RCU trata con la capacidad de los materiales para soportar fuerzas empujantes dirigidas axialmente y, especialmente, es considerada ser uno de las más importantes propiedades mecánicas de

  7. The effect of tow gaps on compression after impact strength of robotically laminated structures

    OpenAIRE

    Rhead, A. T.; Dodwell, T. J.; Butler, R.

    2013-01-01

    When (robotic) Automated Fibre Placement (AFP) is used to manufacture aerospace components with complex three dimensional geometries, gaps between fibre tows can occur. This paper is the first to explore the interaction under compressive load of these tow gaps with impact damage. Two coupons with different distributions of tow-gaps were impacted. Results indicated that the area of delamination is smaller for an impact directly over a tow gap where the tow gap is situated close to the non-impa...

  8. The fracture strength of TRISO-coated particles determined by compression testing between soft aluminium anvils

    International Nuclear Information System (INIS)

    Compression testing of tri-isotropic (TRISO) carbon/silicon carbide-coated fuel particles between anvil materials with a wide range of hardnesses was investigated. During compression testing, the particle produces a hardness impression before it fractures. For subsequent measurements, the same position can therefore not be used. A special testing machine was designed to use the same set of anvils for testing more than one specimen. By each time positioning a particle at a slightly different position between the anvils, a large number of measurements could be made. The load required for fracture is almost independent of anvil hardness for very hard or very soft anvils. Finite element stress analysis showed that when the anvil hardness is very high, fracture occurs because of high local contact bending stresses at the point of contact. In the case of very soft anvils, a tensile stress develops along a latitudinal direction along the perimeter of the particle over a large volume in between the contact zones with the anvils. The particle then fractures by the development of cracks at right angles to the direction of the tensile stress. From the fracture load, the ability of the particle to withstand internal pressure can be assessed. The advantages of using compression testing of full particles between soft anvils without prior preparation to complement previous test methods are highlighted.

  9. Evaluation of compressive strength in cement mortars, according to the dosage established by the colombian seismic resistance code. Case study

    Directory of Open Access Journals (Sweden)

    Sergio Giovanny Valbuena Porras

    2016-06-01

    Full Text Available Context: In a masonry wall the mortar it is between 10 and 20% of the total volume of the system, despite its effect on the behavior of it is significantly higher than this percentage indicates.Objective: The purpose of this research was to evaluate the resistance to compression of two types of mortar paste (A and B, prepared with natural sand from the town of Usme in Bogotá, in accordance with the proportions set by the Standard Colombian earthquake Resistant regulation (NSR-10.Method: Two types of mortar paste were prepared, according to the proportions of cement and sand established in NSR-10 section D.3.4-1 of (Table 1; these proportions were calculated using a 0.0028 m3 container for measuring unit weight. For type A mortar rock sand was used and river sand for type B mortar.Results: The resistance to compression for mortars type A at the end of the study was on average 84% of the expected resistance, whereas for type B mortars it averaged 64% above the expected resistance.Conclusion: Mortar mixes made with crushed or rock (type A arena do not reach the compressive strength required demanded by regulatory standards, despite complying with the dosage established in NSR 10 and with NTC quality criteria; while the natural sand origin or natural river sand meet these standards.

  10. Evaluation of compressive strength and water absorption of soil-cement bricks manufactured with addition of pet (polyethylene terephthalate wastes

    Directory of Open Access Journals (Sweden)

    João Alexandre Paschoalin Filho

    2016-04-01

    Full Text Available This paper presents the evaluation of compressive strength of soil-cement bricks obtained by the inclusion in their mixture of PET flakes through mineral water bottles grinding. The Polyethylene Terephthalate (PET has been characterized by its difficulty of disaggregation in nature, requiring a long period for this. On the other hand, with the increase in civil construction activities the demand for raw material also increases, causing considerable environmental impacts. In this context, the objective of this research is to propose a simple methodology, preventing its dumping and accumulation in irregular areas, and reducing the demand of raw materials by the civil construction industry. The results showed that compressive strengths obtained were lower than recommended by NBR 8491 (Associação Brasileira de Normas Técnicas [ABNT], 2012b at seven days of curing time. However, they may be used as an alternative solution in masonry works in order to not submit themselves to great loads or structural functions. The studied bricks also presented water absorption near to recommended values by NBR 8491 (ABNT, 2012b. Manufacturing costs were also determined for this brick, comparing it with the costs of other brick types. Each brick withdrew from circulation approximately 300 g of PET waste. Thus, for an area of 1 m2 the studied bricks can promote the withdrawal of approximately 180 beverage bottles of 2 L capacity.

  11. Determination of Relationship between Dielectric Properties, Compressive Strength, and Age of Concrete with Rice Husk Ash Using Planar Coaxial Probe

    Directory of Open Access Journals (Sweden)

    Piladaeng Nawarat

    2016-02-01

    Full Text Available This paper deals with an investigation of the dielectric properties of concretes that includes rice husk ash using a planar coaxial probe. The planar coaxial probe has a planar structure with a microstrip and coaxial features. The measurement was performed over the frequency range of 0.5-3.5 GHz, and concrete specimens with different percentages of rice husk ash were tested. The results indicated that the dielectric constant of the concretes was inversely proportional to the frequency, while the conductivity was proportional to the frequency. The dielectric constant decreased with the increasing age of the concrete at the frequency of 1 GHz. The conductivity of the concrete decreased with the increasing age of the concrete at the frequency of 3.2 GHz. In addition, the dielectric constant and the conductivity decreased when the compressive strength increased. It was also shown that the obtained dielectric properties of the concrete could be used to investigate the relationship between the compressive strength and age of the concrete. Moreover, there is an opportunity to apply the proposed probe to determine the dielectric properties of other materials.

  12. Compressive Strength, Pore Size Distribution and Chloride-ion Penetration of Recycled Aggregate Concrete Incorporating Class-F Fly Ash

    Institute of Scientific and Technical Information of China (English)

    KOU Shicong; C S Poon

    2006-01-01

    The effects of fly ash on the compressive strength, pore size distribution ard chloride-ion penetration of recycled aggregate concrete were investigated. Two series of concrete mixtures were prepared. The concrete mixtures in series I had a water-to-binder ratio and a cement content of 0.55 and 410 kg/m3 , respectively. The concrete mixtures in series Ⅱ had a water-to-binder ratio and a cement content of 0.45 and 400 kg/m3 respectively. Recycled aggregate was used as 20% , 50% , and 100% replacements of natural coarse aggregate in the concrete mixtures in both series. In addition, fly ash was used as 0% , 25% and 35% by weight replacements of cement. The results show that the compressive strengths of the concrete decreased as the recycled aggregate and the fly ash contents increased. The total porosity and average porosity diameter of the concrete increased as the recycled aggregate content increased. Furthermore, an increase in the recycled aggregate content decreased the resistance to chloride ion penetration. Nevertheless, the replacement of cement by 25% fly ash improved the resistance to chloride ion penetration and pore diameters and reduced the total porosity of the recycled aggregate concrete.

  13. Strength Anisotropy of Berea Sandstone: Results of X-Ray Computed Tomography, Compression Tests, and Discrete Modeling

    Science.gov (United States)

    Kim, Kwang Yeom; Zhuang, Li; Yang, Hwayoung; Kim, Hanna; Min, Ki-Bok

    2016-04-01

    Berea sandstone in northern Ohio is a transversely isotropic rock. X-ray CT investigations showed that its internal structure is composed of cross-bedded loose layers and relatively thin tightly packed layers called bedding. Uniaxial compression tests were performed on different Berea sandstone specimens. The uniaxial compressive strength (UCS) decreases with increasing porosity, and also decreases with increasing inclination of the bedding plane relative to horizontal line. Two-dimensional discrete modeling was applied to investigate the micromechanical behavior of Berea sandstone. Different microparameters were assigned to loose and tight layers. The UCS simulation results agree well with the experimental results. At the peak stress, cracks almost always develop in loose layers regardless of the bedding plane orientation. In addition, both normal and shear cracks occur earlier for specimens with a higher inclination angle. No correlations were found between the inclination angle of failure planes and the orientation of bedding planes. The bedding planes of Berea sandstone are not weak planes. The strength anisotropy of Berea sandstone is not significant compared with other rocks such as shale, gneiss, and schist.

  14. A summary of the strength and modulus of ice samples from multi-year pressure ridges

    Energy Technology Data Exchange (ETDEWEB)

    Cox, G.F.N.; Mellor, M.; Richter, J.A.; Weeks, W.F.

    1985-03-01

    Over two hundred unconfined compression tests were performed on vertical ice samples obtained from 10 multi-yr pressure ridges in the Beaufort Sea. The tests were performed on a closed-loop electrohydraulic testing machine at two strain rates (10/sup -5/ and 10/sup -3/ s/sup -1/) and two temperatures (-20/sup 0/ and -5/sup 0/C). This paper summarizes the sample preparation and testing techniques used in the investigation and presents data on the compressive strength and initial tangent modulus of the ice.

  15. EFFECT OF STONE DUST ON COMPRESSIVE STRENGTH OF CONCRETE AN EXPERIMENTAL INVESTIGATION

    OpenAIRE

    Syed Yaqub Abbas; Vikas Srivastava

    2015-01-01

    Concrete is the most used construction material having basic ingredients as binding material, fine aggregate, coarse aggregate and water in predetermined proportion all the ingredients are homogeneously mixed to obtain resulting mixed of desired strength. In the present investigation, stone dust, a waste material obtain from crusher plant is used as partial replacement of fine aggregate. M25 grade of concrete was considered for this investigation with a final mix proportion of 1:1...

  16. Effect of SrCO3 addition on the dynamic compressive strength of ZTA

    Institute of Scientific and Technical Information of China (English)

    Ali Arab; Roslan Ahmad; Zainal Arifin Ahmad

    2016-01-01

    Ceramic parts usually experience dynamic load in armor applications. Therefore, studying the dynamic behaviors of ceramics is important. Limited data are available on the dynamic behaviors of ceramics;thus, it is helpful to predict the dynamic strength of ceramics on the basis of their mechanical properties. In this paper, the addition of SrCO3 into zirconia-toughened alumina (ZTA) was demonstrated to improve the fracture toughness of ZTA due to the formation of the SrAl12O19 (SA6) phase. The porosity of ZTA was found to be increased by the addition of SrCO3. These newly formed pores served as the nucleation sites of cracks under dynamic load;these cracks eventually coalesced to form damaged zones in the samples. Although the KIC values of the samples were improved, the dynamic strength was not en-hanced because of the increase in porosity;in fact, the dynamic strength of ZTA ceramics decreased with the addition of SrCO3.

  17. Spall strength and ejecta production of gold under explosively driven shock wave compression

    Energy Technology Data Exchange (ETDEWEB)

    La Lone, B. M. [National Security Technologies, LLC. (NSTec), Mercury, NV (United States); Stevens, G. D. [National Security Technologies, LLC. (NSTec), Mercury, NV (United States); Turley, W. D. [National Security Technologies, LLC. (NSTec), Mercury, NV (United States); Veeser, L. R. [National Security Technologies, LLC. (NSTec), Mercury, NV (United States); Holtkamp, D. B. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2013-12-16

    Explosively driven shock wave experiments were conducted to characterize the spall strength and ejecta production of high-purity cast gold samples. The samples were from 0.75 to 1.84 mm thick and 30 mm in diameter. Peak stresses up to 44 GPa in gold were generated using PBX-9501 high explosive. Sample free surface and ejecta velocities were recorded using photonic Doppler velocimetry techniques. Lithium niobate pins were used to quantify the time dependence of the ejecta density and the total ejected mass. An optical framing camera for time-resolved imaging and a single-image x-ray radiograph were used for additional characterization. Free surface velocities exhibited a range of spall strengths from 1.7 to 2.4 GPa (mean: 2.0 ±0.3 GPa). The pullback signals were faint, minimal ringing was observed in the velocity records, and the spall layer continued to decelerate after first pull back. These results suggest finite tensile strength was present for some time after the initial void formation. Ejecta were observed for every sample with a roughened free surface, and the ejecta density increased with increased surface roughness, which was different in every experiment. The total ejected mass is consistent with the missing mass model.

  18. A preliminary examination of the effect of structure on the (compressive strength) of ice samples from (multi-year pressure ridges)

    Energy Technology Data Exchange (ETDEWEB)

    Richter, J.A.; Cox, G.F.N.

    1985-03-01

    A series of 222 uniaxial constant-strain-rate compression tests was performed on vertical multi-year pressure ridge sea ice samples. A preliminary analysis of the effect of structure on the compressive strength of the ice was performed on 78 of these tests. Test parameters included a temperature of -5 C (23 F) and strain rates of 10 V and 10 T s . Columnar ice loaded parallel to the elongated crystal axes and perpendicular to the crystal c-axis was consistently the strongest type of ice. The strength of the columnar samples decreased significantly as the orientation of the elongated crystals approached the plane of maximum shear. Samples containing granular ice or a mixture of granular and columnar ice resulted in intermediate and low strength values. No clear relationship could be established between structure and strength for these ice types. However, in general, their strength decreased with an increase in porosity.

  19. Strength and Mechanical Response of NaCl Using In-Situ Transmission Electron Microscopy Compression and Nanoindentation.

    Science.gov (United States)

    Lin, Kai-Peng; Fang, Te-Hua; Kang, Sho-Hui

    2016-03-01

    Strength and mechanical properties of single crystal sodium chloride (NaCl) are characterized. Critical deformation variations of NaCl pillared structures and films are estimated using in-situ transmission electron microscope (TEM) compression tests and nanoindentation experiments. Young's modulus and contact stiffness of NaCl pillars with diameters of 300 to 500 nm were 10.4-23.9 GPa, and 159-230 N/m, respectively. The nanohardness and Vickers hardness of the NaCl (001) film were 282-596 and 196-260 MPa, respectively. The results could provide useful information for understanding the mechanical properties, contact and local deformation of NaCl pillars and films. PMID:27455676

  20. A Discrete Element Model for Predicting Shear Strength and Degradation of Rock Joint by Using Compressive and Tensile Test Data

    Science.gov (United States)

    Kazerani, T.; Yang, Z. Y.; Zhao, J.

    2012-09-01

    A discrete element model is proposed to examine rock strength and failure. The model is implemented by UDEC, which is developed for this purpose. The material is represented as a collection of irregular-sized deformable particles interacting at their cohesive boundaries. The interface between two adjacent particles is viewed as a flexible contact whose constitutive law controls the material fracture and fragmentation properties. To reproduce rock anisotropy, an orthotropic cohesive law is developed for the contacts, which allows their shear and tensile behaviors to be different from each other. Using a combination of original closed-form expressions and statistical calibrations, a unique set of the contact microparameters are found based on the uniaxial/triaxial compression and Brazilian tension test data of a plaster. Applying the obtained microparameters, joint specimens, made of the same plaster, are simulated, where the comparison of the obtained results to laboratory data shows a reasonable agreement.

  1. Contributions to the study of porosity in fly ash-based geopolymers. Relationship between degree of reaction, porosity and compressive strength

    Directory of Open Access Journals (Sweden)

    Y. Luna-Galiano

    2016-09-01

    Full Text Available The main contribution of this paper relates to the development of a systematic study involving a set of parameters which could potentially have an impact on geopolymer properties: curing temperature, type of activating solution, alkali metal in solution, incorporation of slag (Ca source and type of slag used. The microstructures, degrees of reaction, porosities and compressive strengths of geopolymers have been evaluated. Geopolymers prepared with soluble silicate presented a more compacted and closed structure, a larger amount of gel, lower porosity and greater compressive strength than those prepared with hydroxides. On the other hand, Na-geopolymers were more porous but more resistant than K-geopolymers. Although there is an inverse relation between degree of reaction and porosity, between compressive strength and porosity it is not always inversely proportional and could, in some cases, be masked by changes produced in other influencing parameters.

  2. The strength of ruby from X-ray diffraction under non-hydrostatic compression to 68 GPa

    Science.gov (United States)

    Dong, Haini; Dorfman, Susannah M.; Wang, Jianghua; He, Duanwei; Duffy, Thomas S.

    2014-07-01

    Polycrystalline ruby (α-Al2O3:Cr3+), a widely used pressure calibrant in high-pressure experiments, was compressed to 68.1 GPa at room temperature under non-hydrostatic conditions in a diamond anvil cell. Angle-dispersive X-ray diffraction experiments in a radial geometry were conducted at beamline X17C of the National Synchrotron Light Source. The stress state of ruby at high pressure and room temperature was analyzed based on the measured lattice strain. The differential stress of ruby increases with pressure from ~3.4 % of the shear modulus at 18.5 GPa to ~6.5 % at 68.1 GPa. The polycrystalline ruby sample can support a maximum differential stress of ~16 GPa at 68.1 GPa under non-hydrostatic compression. The results of this study provide a better understanding of the mechanical properties of this important material for high-pressure science. From a synthesis of existing data for strong ceramic materials, we find that the high-pressure yield strength correlates well with the ambient pressure Vickers hardness.

  3. Strength and stability analysis of a single-walled black phosphorus tube under axial compression

    Science.gov (United States)

    Cai, Kun; Wan, Jing; Wei, Ning; Qin, Qing H.

    2016-07-01

    Few-layered black phosphorus materials currently attract much attention due to their special electronic properties. As a consequence, a single-layer black phosphorus (SLBP) nanotube has been theoretically built. The corresponding electronic properties of such a black phosphorus nanotube (BPNT) were also evaluated numerically. However, unlike graphene formed with 2sp2 covalent carbon atoms, SLBP is formed with 3sp3 bonded atoms. It means that the structure from SLBP will possess lower Young’s modulus and mechanical strength than those of carbon nanotubes. In this study, molecular dynamics simulation is performed to investigate the strength and stability of BPNTs affected by the factors of diameter, length, loading speed and temperature. Results are fundamental for investigating the other physical properties of a BPNT acting as a component in a nanodevice. For example, buckling of the BPNT happens earlier than fracture, before which the nanostructure has very small axial strain. For the same BPNT, a higher load speed results in lower critical axial strain and a nanotube with lower axial strain can still be stable at a higher temperature.

  4. Modeling of Compressive Strength Parallel to Grain of Heat Treated Scotch Pine (Pinus sylvestris L. Wood by Using Artificial Neural Network

    Directory of Open Access Journals (Sweden)

    Fatih Yapıcı

    2016-01-01

    Full Text Available In this study, the compressive strength of heat treated Scotch Pine was modeled using artificial neural network. The compressive strength (CS value parallel to grain was determined after exposing the wood to heat treatment at temperature of 130, 145, 160, 175, 190 and 205ºC for 3, 6, 9, 12 hours. The experimental data was evaluated by using multiple variance analysis. Secondly, the effect of heat treatment on the CS of samples was modeled by using artificial neural network (ANN.

  5. Study of Condition of Molding on Compressive Strength of Cement%影响水泥抗压强度的成型条件研究

    Institute of Scientific and Technical Information of China (English)

    张新爱; 关润伶

    2014-01-01

    水泥抗压强度的测定过程有成型、养护、破型三个主要环节。各环节的试验条件不同,将直接影响抗压强度的测定结果。研究了水泥试件成型过程中流动度、试件尺寸、表面状态等试验条件对试件抗压强度测定结果的影响。结果表明:在一定范围内水灰比与抗压强度呈正相关关系,即水灰比越大,其流动度越好,抗压强度越高,当超过这个范围后,随着水灰比的增大,抗压强度逐渐减小;随着试件尺寸逐渐变大,抗压强度依次降低;试模涂油量多少不同,导致试件表面状态存在差异,涂油量过多或过少都会使抗压强度的测定结果偏低。%Three main aspects of molding, conservation and breaking - type were involved in the testing about compressive strength of cement sample. Different experimental conditions directly influenced the results of compressive strength test. Effects of experimental conditions such as, fluidity, dimension and surface on cement sample compressive-strength in molding process were investigated. The results showed that water cement ratio had a significant linear correlation with compressive strength within a certain range. The bigger the water cement ratio, the better the fluidity and the higher compressive strength. Beyond the range of water cement ratio, compressive strength gradually decreased with the increase of water cement ratio, and remarkably decreased with increasing the sample block size. In addition, the fluctuation of compressive strength can also be caused by the difference of specimen surface with oil coated to varying degrees, which more or less oil would reduce cement compressive strength.

  6. Phase transition and strength of vanadium under shock compression up to 88 GPa

    International Nuclear Information System (INIS)

    A series of reverse-impact experiments were performed on vanadium at shock pressure ranging from 32 GPa to 88 GPa. Particle velocity profiles measured at sample/LiF window interface were used to estimate the sound velocities, shear modulus, and yield stress in shocked vanadium. A phase transition at ∼60.5 GPa that may be the body-centered cubic (BCC) to rhombohedral structure was identified by the discontinuity of the sound velocity against shock pressure. This transition pressure is consistent with the results from diamond anvil cell (DAC) experiments and first-principle calculations. However, present results show that the rhombohedral phase has higher strength and shear modulus than the BCC phase, which is contrast to the findings from DAC experiments and theoretical work

  7. The influence of clay additives in Portland cement on the compressive strength of the cement stone

    Directory of Open Access Journals (Sweden)

    A.R. Gaifullin

    2015-11-01

    Full Text Available The introduction of mineral additives to binders, especially to Portland cement, is one of the promising trends for solving the resource and energy saving problems, as well as problems of environmental protection during production and application. Expanding the supplementary cementitious materials resource base can be achieved through the use of natural pozzolans and thermally activated polymineral clays(commonly known as glinites in Russia. One type of glinite is metakaolin, which is obtained by calcination of kaolin clays. Metakaolin is widely and effectively used as a pozzolanic additive due to its beneficial effect on the physical and mechanical properties of Portland cement-based materials. The obstacle to its wide production and use are the limited deposits of pure kaolin clays in many countries, including the Russian Federation. In this respect, the studies of pozzolanic activity of the most common mineral clays and their use in some countries have significantly advanced. Similar studies were widely performed in the 1940s in USSR. It seems reasonable to renew this trend to provide a scientific base for the production of local pozzolans made of clays commonly used in different regions. Comparative studies of the effect of 5 clays differing in mineral and chemical composition, calcination temperature and specific surface area, and high-quality metakaolin, on the strength of hardened Portland cement paste have been performed. It has been established that introducing 5…10 % of composite clays calcined at 400…8000 C° and milled to a specific surface area of 290…800 m2/kg into Portland cement enhanced the strength of the hardened cement paste considerably better than the introduction of metakaolin with a specific surface area of 1200 m2/kg. The findings of the study suggest that many kinds of commonly used polymineral clays have a specific calcination temperature and dispersity, which results in a higher pozzolanic activity compared with

  8. Method of increasing the phase stability and the compressive yield strength of uranium-1 to 3 wt. % zirconium alloy

    Science.gov (United States)

    Anderson, Robert C.

    1986-01-01

    A uranium-1 to 3 wt. % zirconium alloy characterized by high strength, high ductility and stable microstructure is fabricated by an improved thermal mechanical process. A homogenous ingot of the alloy which has been reduced in thickness of at least 50% in the two-step forging operation, rolled into a plate with a 75% reduction and then heated in vacuum at a temperature of about 750.degree. to 850.degree. C. and then quenched in water is subjected to further thermal-mechanical operation steps to increase the compressive yield strength approximately 30%, stabilize the microstructure, and decrease the variations in mechanical properties throughout the plate is provided. These thermal-mechanical steps are achieved by cold rolling the quenched plate to reduce the thickness thereof about 8 to 12%, aging the cold rolled plate at a first temperature of about 325.degree. to 375.degree. C. for five to six hours and then aging the plate at a higher temperature ranging from 480.degree. to 500.degree. C. for five to six hours prior to cooling the billet to ambient conditions and sizing the billet or plate into articles provides the desired increase in mechanical properties and phase stability throughout the plate.

  9. The effect of fly ash and limestone fillers on the viscosity and compressive strength of self-compacting repair mortars

    Energy Technology Data Exchange (ETDEWEB)

    Burak Felekoglu; Kamile Tosun; Bulent Baradan; Akin Altun; Bahadir Uyulgan [Dokuz Eylul University (Turkey). Faculty of Engineering

    2006-09-15

    Today, self-compacting mortars are preferred for repair purposes due to the application easiness and mechanical advantages. However, for self-compatibility, the paste phase must meet some certain criteria at fresh state. The cement as well as the ingredients of the paste, powders with cementitious, pozzolanic or inert nature and plasticizing chemical admixtures should be carefully chosen in order to obtain a suitable paste composition to enrich the granular skeleton of the mix. The physical properties of powders (shape, surface morphology, fineness, particle size distribution, particle packing) and physico-chemical (time-dependent hydration reactions, zeta potentials) interactions between cement powder and plasticizer should be taken into consideration. All these parameters affect the performance of fresh paste in different manners. There is no universally accepted agreement on the effect of these factors due to the complexity of combined action; thus, it is hard to make a generalization. This study deals with the selection of amount and type of powders from the viewpoint of fresh state rheology and mechanical performance. The influence of powder materials on self-compatibility, viscosity and strength were compared with a properly designed set of test methods (the mini-slump, V-funnel tests, viscosity measurements and compressive strength tests). It may be advised that, for each cement-powder-plasticizer mixture, a series of test methods can be used to determine the optimum content and type of materials for a specified workability.

  10. Influence of cactus mucilage and marine brown algae extract on the compressive strength and durability of concrete

    Directory of Open Access Journals (Sweden)

    Hernández, E. F.

    2016-03-01

    Full Text Available This paper presents the mechanical performance and durability of concrete with water/cement (w/c ratios of 0.30 and 0.60 containing cactus mucilage and brown marine seaweed extract solutions (at 0.5° Brix concentrations. Cylindrical specimens (100 mm x 200 mm were cast and moist-cured for 0 and 28 days. Compressive strength, rapid chloride permeability, and chloride diffusion tests were conducted to evaluate all of the concrete mixes at the ages of 60 and 120 days. In addition, accelerated carbonation tests were carried out on specimens at the age of 180 days by exposure to 23 °C, 60% RH and at 4.4% CO2 for 120 days. The compressive strength results showed that only one concrete mix with admixtures increased in strength compared to the control. Regarding the rapid chloride permeability, chloride diffusion and carbonation, the results indicated that the durability of concretes containing organic additions was enhanced compared to the control.Este trabajo presenta el comportamiento mecánico y de durabilidad de concretos con relaciones agua/cemento de 0.30 y 0.60, conteniendo soluciones de mucílago de nopal y extracto de algas marinas cafés (0.5 °Brix de concentración. Especímenes cilíndricos (100 mm x 200 mm fueron elaborados y curados en húmedo por 0 y 28 días. Se evaluó la resistencia a la compresión, permeabilidad rápida y difusión de cloruros a los 60 y 120 días de edad. Adicionalmente, se realizaron pruebas de carbonatación acelerada en especímenes con 180 días de edad, expuestos a 23 °C, 60% HR y 4.4% de CO2 por 120 días. Los resultados de resistencia a la compresión muestran que únicamente una mezcla de concreto con adición orgánica incrementó su resistencia con respecto al control. Con respecto a la permeabilidad rápida a cloruros, difusión de cloruros y carbonatación, los resultados indican que la durabilidad de los concretos que contenían adiciones orgánicas fue mejorada con respecto al control.

  11. Neural network modeling to evaluate the dynamic flow stress of high strength armor steels under high strain rate compression

    Directory of Open Access Journals (Sweden)

    Ravindranadh Bobbili

    2014-12-01

    Full Text Available An artificial neural network (ANN constitutive model is developed for high strength armor steel tempered at 500 °C, 600 °C and 650 °C based on high strain rate data generated from split Hopkinson pressure bar (SHPB experiments. A new neural network configuration consisting of both training and validation is effectively employed to predict flow stress. Tempering temperature, strain rate and strain are considered as inputs, whereas flow stress is taken as output of the neural network. A comparative study on Johnson–Cook (J–C model and neural network model is performed. It was observed that the developed neural network model could predict flow stress under various strain rates and tempering temperatures. The experimental stress–strain data obtained from high strain rate compression tests using SHPB, over a range of tempering temperatures (500–650 °C, strains (0.05–0.2 and strain rates (1000–5500/s are employed to formulate J–C model to predict the high strain rate deformation behavior of high strength armor steels. The J-C model and the back-propagation ANN model were developed to predict the high strain rate deformation behavior of high strength armor steel and their predictability is evaluated in terms of correlation coefficient (R and average absolute relative error (AARE. R and AARE for the J–C model are found to be 0.7461 and 27.624%, respectively, while R and AARE for the ANN model are 0.9995 and 2.58%, respectively. It was observed that the predictions by ANN model are in consistence with the experimental data for all tempering temperatures.

  12. Neural network modeling to evaluate the dynamic flow stress of high strength armor steels under high strain rate compression

    Institute of Scientific and Technical Information of China (English)

    Ravindranadh BOBBILI; V. MADHU; A.K. GOGIA

    2014-01-01

    An artificial neural network (ANN) constitutive model is developed for high strength armor steel tempered at 500 ?C, 600 ?C and 650 ?C based on high strain rate data generated from split Hopkinson pressure bar (SHPB) experiments. A new neural network configuration consisting of both training and validation is effectively employed to predict flow stress. Tempering temperature, strain rate and strain are considered as inputs, whereas flow stress is taken as output of the neural network. A comparative study on JohnsoneCook (JeC) model and neural network model is performed. It was observed that the developed neural network model could predict flow stress under various strain rates and tempering temperatures. The experimental stressestrain data obtained from high strain rate compression tests using SHPB, over a range of tempering temperatures (500e650 ?C), strains (0.05e0.2) and strain rates (1000e5500/s) are employed to formulate JeC model to predict the high strain rate deformation behavior of high strength armor steels. The J-C model and the back-propagation ANN model were developed to predict the high strain rate deformation behavior of high strength armor steel and their predictability is evaluated in terms of correlation coefficient (R) and average absolute relative error (AARE). R and AARE for the JeC model are found to be 0.7461 and 27.624%, respectively, while R and AARE for the ANN model are 0.9995 and 2.58%, respectively. It was observed that the predictions by ANN model are in consistence with the experimental data for all tempering temperatures.

  13. Hierarchical Order of Influence of Mix Variables Affecting Compressive Strength of Sustainable Concrete Containing Fly Ash, Copper Slag, Silica Fume, and Fibres

    Directory of Open Access Journals (Sweden)

    Sakthieswaran Natarajan

    2014-01-01

    Full Text Available Experiments have been conducted to study the effect of addition of fly ash, copper slag, and steel and polypropylene fibres on compressive strength of concrete and to determine the hierarchical order of influence of the mix variables in affecting the strength using cluster analysis experimentally. While fly ash and copper slag are used for partial replacement of cement and fine aggregate, respectively, defined quantities of steel and polypropylene fibres were added to the mixes. It is found from the experimental study that, in general, irrespective of the presence or absence of fibres, (i for a given copper slag-fine aggregate ratio, increase in fly ash-cement ratio the concrete strength decreases and with the increase in copper slag-sand ratio also the rate of strength decrease and (ii for a given fly ash-cement ratio, increase in copper slag-fine aggregate ratio increases the strength of the concrete. From the cluster analysis, it is found that the quantities of coarse and fine aggregate present have high influence in affecting the strength. It is also observed that the quantities of fly ash and copper slag used as substitutes have equal “influence” in affecting the strength. Marginal effect of addition of fibres in the compression strength of concrete is also revealed by the cluster analysis.

  14. An Assessment of the Compressive Strength of Glass Reinforced Plastic Waste Filled Concrete for Potential Applications in Construction

    Directory of Open Access Journals (Sweden)

    Asokan Pappu

    2010-03-01

    Full Text Available

    Efforts were made to recycle Glass reinforced plastic (GRP waste powder in concrete products and assess its compressive strength to comply with British Standards for use in construction applications. More than 90 GRP waste-filled concrete specimens were

  15. Strength and deformability of compressed concrete elements with various types of non-metallic fiber and rods reinforcement under static loading

    Science.gov (United States)

    Nevskii, A. V.; Baldin, I. V.; Kudyakov, K. L.

    2015-01-01

    Adoption of modern building materials based on non-metallic fibers and their application in concrete structures represent one of the important issues in construction industry. This paper presents results of investigation of several types of raw materials selected: basalt fiber, carbon fiber and composite fiber rods based on glass and carbon. Preliminary testing has shown the possibility of raw materials to be effectively used in compressed concrete elements. Experimental program to define strength and deformability of compressed concrete elements with non-metallic fiber reinforcement and rod composite reinforcement included design, manufacture and testing of several types of concrete samples with different types of fiber and longitudinal rod reinforcement. The samples were tested under compressive static load. The results demonstrated that fiber reinforcement of concrete allows increasing carrying capacity of compressed concrete elements and reducing their deformability. Using composite longitudinal reinforcement instead of steel longitudinal reinforcement in compressed concrete elements insignificantly influences bearing capacity. Combined use of composite rod reinforcement and fiber reinforcement in compressed concrete elements enables to achieve maximum strength and minimum deformability.

  16. Compressive strength of two newly developed glass-ionomer materials for use with the Atraumatic Restorative Treatment (ART) approach in class II cavities.

    NARCIS (Netherlands)

    Koenraads, H.; Kroon, G. Van der; Frencken, J.E.F.M.

    2009-01-01

    OBJECTIVES: The null-hypotheses tested were that no difference in compressive strength of ART class II cavities exists between those restored with (1) glass-carbomer and a commonly used glass-ionomer; (2) KMEM and the commonly used glass-ionomer and; (3) glass-carbomer and KMEM. METHODS: 100 molar t

  17. 泡沫混凝土的抗压强度对比试验研究%Foam concrete compressive strength of the contrast test research

    Institute of Scientific and Technical Information of China (English)

    宫家良; 姚文杰

    2016-01-01

    介绍了泡沫混凝土的特点,通过试验,分析了粉煤灰和聚丙乙烯掺量对泡沫混凝土抗压强度的影响,指出使用粉煤灰代替部分水泥可以有效降低泡沫混凝土的自重,在泡沫混凝土中掺入纤维可增加其抗压强度,且聚丙乙烯的掺量为0.9 kg/ m3时抗压强度最大,达到了减少水泥用量,增加抗压强度的目标。%This paper introduced the characteristics of foam concrete,through the experimental analyzed the influence of fly ash and poly acrylic dosage to foam concrete compression strength,pointed out that using fly ash to replace partial cement could effectively reduce the weight of foam concrete,mixed fiber in foam concrete could increase the compression strength,and the content poly acrylic was 0. 9 kg/ m3 had the maximum compression strength,to reduce the dosage of cement,aim to increase the compression strength.

  18. Unconfined Aquifer Flow Theory - from Dupuit to present

    OpenAIRE

    Mishra, Phoolendra K.; Kuhlman, Kristopher L.

    2013-01-01

    Analytic and semi-analytic solution are often used by researchers and practicioners to estimate aquifer parameters from unconfined aquifer pumping tests. The non-linearities associated with unconfined (i.e., water table) aquifer tests makes their analysis more complex than confined tests. Although analytical solutions for unconfined flow began in the mid-1800s with Dupuit, Thiem was possibly the first to use them to estimate aquifer parameters from pumping tests in the early 1900s. In the 195...

  19. Arrows of time in unconfined systems

    CERN Document Server

    Barbour, Julian

    2016-01-01

    Entropy and the second law of thermodynamcs were discovered through study of the behaviour of gases in confined spaces. The related techniques developed in the kinetic theory of gases have failed to resolve the apparent conflict between the time-reversal symmetry of all known laws of nature and the existence of arrows of time that at all times and everywhere in the universe all point in the same direction. I will argue that the failure may due to unconscious application to the universe of the conceptual framework developed for confined systems. If, as seems plausible, the universe is an unconfined system, new concepts are needed.

  20. FAILURE MODE AND CONSTITUTIVE MODEL OF PLAIN HIGH-STRENGTH HIGH-PERFORMANCE CONCRETE UNDER BIAXIAL COMPRESSION AFTER EXPOSURE TO HIGH TEMPERATURES

    Institute of Scientific and Technical Information of China (English)

    Zhenjun He; Yupu Song

    2008-01-01

    An orthotropic constitutive relationship with temperature parameters for plain highstrength high-performance concrete (HSHPC) under biaxial compression is developed. It is based on the experiments performed for characterizing the strength and deformation behavior at two strength levels of HSHPC at 7 different stress ratios including α = σ2 : σ3 = 0.00 : -1, -0.20 : -1, -0.30 : -1, -0.40 : -1, -0.50 : -1, -0.75 : -1, -1.00 : -1, after the exposure to normal and high temperatures of 20, 200, 300, 400, 500 and 600℃, and using a large static-dynamic true triaxial machine. The biaxial tests were performed on 100 mm × 100 mm × 100 mm cubic specimens, and friction-reducing pads were used consisting of three layers of plastic membrane with glycerine in-between for the compressive loading plane. Based on the experimental results, failure modes of HSHPC specimens were described. The principal static compressive strengths, strains at the peak stress and stress-strain curves were measured; and the influence of the temperature and stress ratios on them was also analyzed. The experimental results showed that the uniaxial compressive strength of plain HSHPC after exposure to high temperatures does not decrease dramatically with the increase of temperature. The ratio of the biaxial to its uniaxial compressive strength depends on the stress ratios and brittleness-stiffness of HSHPC after exposure to different temperature levels. Comparison of the stress-strain results obtained from the theoretical model and the experimental data indicates good agreement.

  1. The Effect of Variation of Molarity of Alkali Activator and Fine Aggregate Content on the Compressive Strength of the Fly Ash: Palm Oil Fuel Ash Based Geopolymer Mortar

    Directory of Open Access Journals (Sweden)

    Iftekhair Ibnul Bashar

    2014-01-01

    Full Text Available The effect of molarity of alkali activator, manufactured sand (M-sand, and quarry dust (QD on the compressive strength of palm oil fuel ash (POFA and fly ash (FA based geopolymer mortar was investigated and reported. The variable investigated includes the quantities of replacement levels of M-sand, QD, and conventional mining sand (N-sand in two concentrated alkaline solutions; the contents of alkaline solution, water, POFA/FA ratio, and curing condition remained constant. The results show that an average of 76% of the 28-day compressive strength was found at the age of 3 days. The rate of strength development from 3 to 7 days was found between 12 and 16% and it was found much less beyond this period. The addition of 100% M-sand and QD shows insignificant strength reduction compared to mixtures with 100% N-sand. The particle angularity and texture of fine aggregates played a significant role in the strength development due to the filling and packing ability. The rough texture and surface of QD enables stronger bond between the paste and the fine aggregate. The concentration of alkaline solution increased the reaction rate and thus enhanced the development of early age strength. The use of M-sand and QD in the development of geopolymer concrete is recommended as the strength variation between these waste materials and conventional sand is not high.

  2. Compressive strength and interfacial transition zone of sugar cane bagasse ash concrete: A comparison to the established pozzolans

    Science.gov (United States)

    Hussein, Asma Abd Elhameed; Shafiq, Nasir; Nuruddin, Muhd Fadhil

    2015-05-01

    Agricultural and industrial by-products are commonly used in concrete production as cement replacement materials (CRMs) or as admixtures to enhance both fresh and hardened properties of concrete as well as to save the environment from the negative effects caused by their disposal. Sugar Cane Bagasse Ash (SCBA) is one of the promising CRMs, it is used as a partial replacement of cement for producing concrete; properties of such concrete depend on the chemical composition, fineness, and burning temperature of SCBA. Approximately 1500 Million tons of sugarcane are annually produced over all the world which leave about 40-45% bagasse after juice crushing for sugar industry giving an average annual production of about 600 Million tons of bagasse as a waste material. This paper presents some findings on the effect of SCBA on workability, compressive strength and microstructure of interfacial zone of concrete and its performance is compared to some of the established CRMs namely Densified Silica Fume, Fly Ash and Microwave Incinerated Rice Husk Ash.

  3. RESIDUAL COMPRESSIVE STRENGTH OF FLY ASH BASED GLASS FIBRE REINFORCED HIGH PERFORMANCE CONCRETE SUBJECTED TO ACID ATTACK

    Directory of Open Access Journals (Sweden)

    Dr.H.Sudarsana Rao

    2012-01-01

    Full Text Available In recent years, improvements in concrete properties have been achieved by the invention of High- Performance-Concrete (HPC. Improvements involving a combination of improved compaction, improved paste characteristics and aggregate-matrix bond, and reduced porosity are achieved through HPC. The ductility of HPC can be improved by altering its composition through the addition of glass fibers in the design mix. High- Performance-Concrete made with glass fibers inside is regarded as Glass Fiber Reinforced High Performance Concrete (GFRHPC. This paper presents the details of an experimental investigation planned to utilize fly ash in the production of Glass fibre reinforced High-Performance-Concrete (GFRHPC. The investigation examines the progressive deterioration of concrete mixtures containing various combinations of fly ash based GFRHPCmixes exposed to sulphate and chloride solutions. Acid attack tests have been conducted to measure the durability of GFRHPC. Cubes of 150X150X150 mm have been cast, cured and then kept immersed in 5%concentrated solutions of HCl, H2SO4 and MgSO4 for 30, 60 and 90 days and then tested to record the residual compressive strengths of GFRHPC produced with the fly ash mineral admixtures. The results have been analyzed and useful conclusions have been drawn.

  4. Experimental Study on Compressive Strength of Pervious Concrete%透水混凝土抗压强度试验研究

    Institute of Scientific and Technical Information of China (English)

    唐硕; 丁权福; 洪涛; 徐晓燕; 喻孟雄; 苏登宇

    2015-01-01

    为优化满足特定孔隙率条件下的透水混凝土抗压强度,试验研究了材料制备过程中水灰比和胶骨比变化对抗压强度的影响,分析了常用矿物掺合料在掺量变化情况下的浆体强度。结果表明,满足21%的孔隙率时,提高抗压强度的最佳水灰比为0.3,胶骨比为1:5;提高浆体强度的掺合料最佳单一掺量分别为:粉煤灰20%、矿渣微粉24%、硅灰6%,硅灰为佳,同量级变化下其28天抗压强度增长19.3%。%In order to optimize and meet the pervious concrete compressive strength under specific porosity conditions, this test studies the influence of the changes of water-cement ratio and plastic bone ratio on the compressive strength in materials preparation process, and analyzes the slurry strength of common mineral admixtures under the changes of proportion. The results show that, when the satisfied porosity is 21%, the best water-cement ratio of the compressive strength is 0.3, plastic bone ratio is 1: 5; the best single proportion of admixtures to improve the slurry strength is:20%of the fly ash, 24%of the slag powder, 6%of silica fume, silica fume is better, and under the same magnitude change, its 28 days compressive strength is increased by 19.3%.

  5. Study of recycled concrete aggregate quality and its relationship with recycled concrete compressive strength using database analysis

    Directory of Open Access Journals (Sweden)

    González-Taboada, I.

    2016-09-01

    Full Text Available This work studies the physical and mechanical properties of recycled concrete aggregate (recycled aggregate from concrete waste and their influence in structural recycled concrete compressive strength. For said purpose, a database has been developed with the experimental results of 152 works selected from over 250 international references. The processed database results indicate that the most sensitive properties of recycled aggregate quality are density and absorption. Moreover, the study analyses how the recycled aggregate (both percentage and quality and the mixing procedure (pre-soaking or adding extra water influence the recycled concrete strength of different categories (high or low water to cement ratios. When recycled aggregate absorption is low (under 5%, pre-soaking or adding extra water to avoid loss in workability will negatively affect concrete strength (due to the bleeding effect, whereas with high water absorption this does not occur and both of the aforementioned correcting methods can be accurately employed.El estudio analiza las propiedades físico-mecánicas de los áridos reciclados de hormigón (procedentes de residuos de hormigón y su influencia en la resistencia a compresión del hormigón reciclado estructural. Para ello se ha desarrollado una base de datos con resultados de 152 trabajos seleccionados a partir de más de 250 referencias internacionales. Los resultados del tratamiento de la base indican que densidad y absorción son las propiedades más sensibles a la calidad del árido reciclado. Además, este estudio analiza cómo el árido reciclado (porcentaje y calidad y el procedimiento de mezcla (presaturación o adición de agua extra influyen en la resistencia del hormigón reciclado de diferentes categorías (alta o baja relación agua-cemento. Cuando la absorción es baja (inferior al 5% presaturar o añadir agua para evitar pérdidas de trabajabilidad afectan negativamente a la resistencia (debido al bleeding

  6. Experimental Study on Unconfined Vapor Cloud Explosion

    Institute of Scientific and Technical Information of China (English)

    毕明树; ABULITI; Abudula

    2003-01-01

    An experimental system was setup to study the pressure field of unconfined vapor cloud explosions.The semi-spherical vapor clouds were formed by slotted 0.02mm polyethylene film.In the Center of the cloud was an ignition electrode that met ISO6164"Explosion protection System" and NFPA68 "Guide for Venting of Deflagrations". A data-acquisition system,with dymame responding time less than 0.001s with 0.5% accuracy,recorded the pressure-time diagram of acetylene-air mixture explosion with stoichiometrical ratio.The initial cloud diameters varied from 60cm to 300cm.Based on the analysis of experimental data,the quantitative relationship is obtained for the cloud explosion pressure,the cloud radius and the distance from ignition point .Present results provide a useful way to evaluate the building damage caused by unconfined vapor cloud explosions and to determine the indispensable explosion grade in the application of multi-energy model.

  7. 饱和冻结粉土在常应变速率下的单轴抗压强度%Uniaxial Compressive Strength of the Saturated Frozen Silt at Constant Strain Rates

    Institute of Scientific and Technical Information of China (English)

    李海鹏; 朱元林; 潘卫东

    2002-01-01

    Uniaxial compressive strength tests were conducted on the saturated frozen Lanzhou silt (loess) at various constant strain rates and at various constant temperatures. It is concluded from the test results that: the compressive strength (σ f) is very sensitive to temperature (θ) and increases with the temperature decreasing as a power law. Compressive strength is sensitive to strain rate () and increases with strain rates increasing within a certain range of strain rates as a power law. Compressive strength decreases when time to failure (tf) increases, also following a power law. Finally, Compressive strength of frozen silt with higher dry density (γd) is higher than that of frozen silt with lower dry density. The difference between them is mainly influenced by strain rate.

  8. Poly-L-lactide/sodium alginate/chitosan microsphere hybrid scaffolds made with braiding manufacture and adhesion technique: Solution to the incongruence between porosity and compressive strength.

    Science.gov (United States)

    Lin, Jia-Horng; Chen, Chih-Kuang; Wen, Shih-Peng; Lou, Ching-Wen

    2015-01-01

    Bone scaffolds require a three-dimensional structure, high porosity, interconnected pores, adequate mechanical strengths, and non-toxicity. A high porosity is incongruent with mechanical strengths. Therefore, this study combines a braiding method and microsphere solution to create bone scaffolds with a high porosity and sufficient mechanical strengths. First, poly-L-lactide (PLLA) plied yarns are braided into 5-, 10-, 15-, 20-, and 25-layer hollow braids, and then thermally treated at 165 °C for various durations. Next, sodium alginate (SA) microspheres, cross-linked with CaCl2 solution with various concentrations, are combined with PLLA porous braided bone scaffolds to form PLLA/SA/CS microsphere hybrid scaffolds, which are then observed for surface observation, and tested for porosity, water contact angle, compressive strength, MTT assay, bioactivity, alkaline phosphatase (ALP) assay, cell attachment, and statistical analyses. The test results show that the layer amount of the bone scaffold is proportional to the compressive strength. With the same number of layers, the compressive strength is inversely proportional to the concentration of the CaCl2 solution. The results of surface observation, porosity, and water contact angle tests show that PLLA/SA/CS microsphere hybrid scaffolds possess a high porosity and good hydrophilicity; as a result, the braiding manufacture and the bonding technique effectively solve the confliction between porosity and mechanical strength. The concentration of CaCl2 does not pertain to cell activity and ALP results, exemplified by good cell attachment on bone scaffolds for each specification. PMID:25953547

  9. Effects of coating thickness and interfacial roughness on cracking and delamination strength of WC-Co coating measured by ring compression test

    Science.gov (United States)

    Kato, Masahiko; Nazul, Mahmoud; Itti, Takeshi; Akebono, Hiroyuki; Sugeta, Atsushi; Mitani, Eiji

    2014-08-01

    The effects of coating thickness and interfacial roughness on the interfacial fracture toughness of tungsten carbide-cobalt (WC-Co) coatings were evaluated using a ring compression test. WC-Co powder was sprayed on steel (JIS:SS400) rings by a high-velocity air- fuel method in coatings with various thicknesses and values of interfacial roughness. The ring compression test was carried out, and the cracking and delamination behavior of the coatings was observed using charge-coupled-device cameras. The results showed that cracking perpendicular to the loading direction occurred in the coatings during the ring compression test, and the cracking strength obtained from the ring compression test decreased slightly with increasing coating thickness, but was independent of the interfacial roughness. Upon further increase of the compression load, the coatings delaminated from the substrate. The interfacial fracture toughness calculated from the delamination of the coatings during the ring compression test decreased with increasing coating thickness and increased with increasing interfacial roughness.

  10. Unconfined Aquifer Flow Theory - from Dupuit to present

    CERN Document Server

    Mishra, Phoolendra K

    2013-01-01

    Analytic and semi-analytic solution are often used by researchers and practicioners to estimate aquifer parameters from unconfined aquifer pumping tests. The non-linearities associated with unconfined (i.e., water table) aquifer tests makes their analysis more complex than confined tests. Although analytical solutions for unconfined flow began in the mid-1800s with Dupuit, Thiem was possibly the first to use them to estimate aquifer parameters from pumping tests in the early 1900s. In the 1950s, Boulton developed the first transient well test solution specialized to unconfined flow. By the 1970s Neuman had developed solutions considering both primary transient storage mechanisms (confined storage and delayed yield) without non-physical fitting parameters. In the last decade, research into developing unconfined aquifer test solutions has mostly focused on explicitly coupling the aquifer with the linearized vadose zone. Despite the many advanced solution methods available, there still exists a need for realism ...

  11. Nitrate reduction in an unconfined sandy aquifer

    DEFF Research Database (Denmark)

    Postma, Diederik Jan; Boesen, Carsten; Kristiansen, Henning;

    1991-01-01

    in the reduced zone of the aquifer are organic matter, present as reworked brown coal fragments from the underlying Miocene, and small amounts of pyrite at an average concentration of 3.6 mmol/kg. Electron balances across the redoxcline, based on concentrations of O2, NO3-, SO4(2-) and total inorganic carbon......Nitrate distribution and reduction processes were investigated in an unconfined sandy aquifer of Quaternary age. Groundwater chemistry was studied in a series of eight multilevel samplers along a flow line, deriving water from both arable and forested land. Results show that plumes of nitrate......-contaminated groundwater emanate from the agricultural areas and spread through the aquifer. The aquifer can be subdivided into an upper 10- to 15-m thick oxic zone that contains O2 and NO3-, and a lower anoxic zone characterized by Fe2+-rich waters. The redox boundary is very sharp, which suggests that reduction...

  12. Fly and bottom ashes from biomass combustion as cement replacing components in mortars production: rheological behaviour of the pastes and materials compression strength.

    Science.gov (United States)

    Maschio, Stefano; Tonello, Gabriele; Piani, Luciano; Furlani, Erika

    2011-10-01

    In the present research mortar pastes obtained by replacing a commercial cement with the equivalent mass of 5, 10, 20 and 30 wt.% of fly ash or bottom ash from fir chips combustion, were prepared and rheologically characterized. It was observed that the presence of ash modifies their rheological behaviour with respect to the reference blend due to the presence, in the ashes, of KCl and K2SO4 which cause precipitation of gypsum and portlandite during the first hydration stages of the pastes. Hydrated materials containing 5 wt.% of ash display compression strength and absorption at 28 d of same magnitude as the reference composition; conversely, progressive increase of ash cause a continuous decline of materials performances. Conversely, samples tested after 180 d display a marked decline of compression strength, as a consequence of potassium elution and consequent alkali-silica reaction against materials under curing.

  13. Laboratory Investigation on Compressive Strength and Micro-structural Features of Foamed Concrete with Addition of Wood Ash and Silica Fume as a Cement Replacement

    Directory of Open Access Journals (Sweden)

    Othuman Mydin M.A.

    2014-01-01

    Full Text Available Wood Ash (WA and Silica Fume (SF exhibit good cementation properties and have great potential as supplementary binder materials for the concrete production industry. This study will focus on enhancing the micro-structural formation and compressive strength of foamed concrete with the addition of WA and SF. A total of 3 mixes were prepared with the addition of WA and SF at various cement replacement levels by total binder weight. For this particular study, the combination of WA (5%, 10%, and 15% by binder weight and SF (5%, 10%, and 15% by binder weight were utilized as supplementary binder materials to produce foamed concrete mixes. As was made evident from micrographs obtained in the study, the improvement observed in the compressive strength of the foamed concrete was due to a significant densification in the microstructure of the cement paste matrix in the presence of WA and SF hybrid supplementary binders. Experimental results indicated that the combination of 15% SF and 5% WA by binder weight had a more substantial influence on the compressive strength of foamed concrete compared to the control mix. Furthermore, the addition of WA and SF significantly prolonged the setting times of the blended cement paste of the foamed concrete.

  14. STUDY ON COMPRESSIVE STRENGTH OF RECYCLED AGGREGATE CONCRETE%再生混凝土抗压强度试验研究

    Institute of Scientific and Technical Information of China (English)

    孙晓雪; 赵吉坤; 张永兴; 杜林勇

    2011-01-01

    通过对实验室及室外等3种不同的废弃混凝土再生后进行抗压强度试验,研究了取代率分别为0,40%,70%,100%的再生粗骨料混凝土及再生细骨料混凝土抗压强度.研究结果表明,再生混凝土的取代率对再生混凝土的抗压强度影响很大.室内与室外骨料再生混凝土的抗压强度变化规律不同.针对实验提出了再生混凝土抗压强度与取代率关系的公式.%We studied compressive strength of recycled aggregate concrete with 0, 40% , 70% and 100% replacement rates. The results indicated that the recycled aggregate concrete replacement rate has a remarkable influence on the compressive strength of recycled aggregate concrete. According to the ex-periment, formula of the relationship between recycled aggregate replacement rate and compressive strength of recycled aggregate concrete is present.

  15. Analysis of Environmental Impact for Concrete Using LCA by Varying the Recycling Components, the Compressive Strength and the Admixture Material Mixing

    Directory of Open Access Journals (Sweden)

    Taehyoung Kim

    2016-04-01

    Full Text Available Concrete is a type of construction material in which cement, aggregate, and admixture materials are mixed. When cement is produced, large amounts of substances that impact the environment are emitted during limestone extraction and clinker manufacturing. Additionally, the extraction of natural aggregate causes soil erosion and ecosystem destruction. Furthermore, in the process of transporting raw materials such as cement and aggregate to a concrete production company, and producing concrete in a batch plant, substances with an environmental impact are emitted into the air and water system due to energy use. Considering the fact that the process of producing concrete causes various environmental impacts, an assessment of various environmental impact categories is needed. This study used a life cycle assessment (LCA to evaluate the environmental impacts of concrete in terms of its global warming potential, acidification potential, eutrophication potential, ozone depletion potential, photochemical ozone creation potential, and abiotic depletion potential (GWP, AP, EP, ODP, POCP, ADP. The tendency was that the higher the strength of concrete, the higher the GWP, POCP, and ADP indices became, whereas the AP and EP indices became slightly lower. As the admixture mixing ratio of concrete increased, the GWP, AP, ODP, ADP, and POCP decreased, but EP index showed a tendency to increase slightly. Moreover, as the recycled aggregate mixing ratio of concrete increased, the AP, EP, ODP, and ADP decreased, while GWP and POCP increased. The GWP and POCP per unit compressed strength (1 MPa of high strength concrete were found to be about 13% lower than that for its normal strength concrete counterpart. Furthermore, in the case of AP, EP, ODP, and ADP per unit compressed strength (1 MPa, high-strength concrete was found to be about 10%~25% lower than its normal strength counterpart. Among all the environmental impact categories, ordinary cement was found to have

  16. Confinement effects on the steel-concrete bond strength and pull-out failure

    International Nuclear Information System (INIS)

    In this contribution, an experimental campaign based on unconfined and actively confined pull-out tests is presented to investigate the bond stress-slip behavior. This campaign aims at underlining passive (concrete cover) and active (external pressure) confinement effects on the maximal bond stress. Experimental results are associated to a numerical approach in order to predict the evolution of the bond strength. Equations are finally proposed that distinguish splitting failure (function of the concrete tensile properties) and pull-out failure (function of the compressive concrete properties). (authors)

  17. Linear dimensional change, compressive strength and detail reproduction in type IV dental stone dried at room temperature and in a microwave oven

    Directory of Open Access Journals (Sweden)

    Marcos Aurélio Bomfim da Silva

    2012-10-01

    Full Text Available The type IV dental stone is widely used for the fabrication of dyes and master casts for fixed and removable partial prostheses. It is typically normal to wait at least 24 hours for the casts to dry prior to beginning the laboratory procedures. The waiting time has been shown to be greatly reduced by using microwave drying. OBJECTIVE: This study evaluated the influence of drying techniques at room temperature and microwave oven on the linear dimensional change, compressive strength and detail reproduction in type IV dental stones. MATERIAL AND METHODS: Three type IV dental stone brands were selected; elite Rock, Shera Premium and Durone IV. Two different drying protocols were tested in 4 groups (n=10; G1 - room temperature (25±4ºC dried for 2 hours; G2 - room temperature dried for 24 hours; G3 - room temperature dried for 7 days and G4 - microwave oven dried at 800 W for 5 minutes and after 2 hours at room temperature. After drying, the samples were assayed for dimensional charges. The sample surface was submitted to the ImageTool 3.0 software for compressive strength in a universal testing machine with a cell load of 50 KN at a crosshead speed of 0.5 mm/minutes and the detail reproduction was analyzed with a stereomicroscope at 25x magnification. The statistical analysis of the linear dimensional change and compressive strength data were conducted by the ANOVA test followed by the Tukey test (p<0.05. Detailed reproduction values were reported in percentages. RESULTS: For the compressive strength test, Elite Rock and Durone IV did not present significant differences between G2 and G4, while Shera Premium did not present differences between G3 and G4. The best reproduction levels were observed for G3. CONCLUSIONS: Dental stone microwave oven drying showed a linear dimensional change similar to after room temperature drying for 24 hours and 7 days. The compressive strength of the stone dried in the microwave oven was similar to those dried at

  18. Smart cement modified with iron oxide nanoparticles to enhance the piezoresistive behavior and compressive strength for oil well applications

    Science.gov (United States)

    Vipulanandan, C.; Mohammed, A.

    2015-12-01

    In this study, smart cement with a 0.38 water-to-cement ratio was modified with iron oxide nanoparticles (NanoFe2O3) to have better sensing properties, so that the behavior can be monitored at various stages of construction and during the service life of wells. A series of experiments evaluated the piezoresistive smart cement behavior with and without NanoFe2O3 in order to identify the most reliable sensing properties that can also be relatively easily monitored. Tests were performed on the smart cement from the time of mixing to a hardened state behavior. When oil well cement (Class H) was modified with 0.1% of conductive filler, the piezoresistive behavior of the hardened smart cement was substantially improved without affecting the setting properties of the cement. During the initial setting the electrical resistivity changed with time based on the amount of NanoFe2O3 used to modify the smart oil well cement. A new quantification concept has been developed to characterize the smart cement curing based on electrical resistivity changes in the first 24 h of curing. Addition of 1% NanoFe2O3 increased the compressive strength of the smart cement by 26% and 40% after 1 day and 28 days of curing respectively. The modulus of elasticity of the smart cement increased with the addition of 1% NanoFe2O3 by 29% and 28% after 1 day and 28 days of curing respectively. A nonlinear curing model was used to predict the changes in electrical resistivity with curing time. The piezoresistivity of smart cement with NanoFe2O3 was over 750 times higher than the unmodified cement depending on the curing time and nanoparticle content. Also the nonlinear stress-strain and stress-change in resistivity relationships predicated the experimental results very well. Effects of curing time and NanoFe2O3 content on the model parameters have been quantified using a nonlinear model.

  19. Experiment Study on Early Compressive Strength of Fly Ash Mortar%粉煤灰砂浆早期抗压强度试验研究

    Institute of Scientific and Technical Information of China (English)

    徐云

    2013-01-01

    In this paper, according to different mixing proportion, it develops M5 fly ash mortar of the six groups, the three groups of 13.6% fly ash content and the another groups of 11.5% fly ash content. Natural curing after 3 days, it Studies the influence factors of early compressive strength of fly ash mortar through the compressive strength test. Research shows that:air-entraining agent (micro foam agent) incorporation will lower early strength of fly ash mortar. The mixed water reducing agent can improve the early strength of fly ash mortar. When the dosage of water reducing agent arrives a certain level, the smaller the water/cement ratio is, the higher the early compressive strength of fly ash cement is. Specimens are selected from 6 group 28 days compressive strength of fly ash mortar which can reach more than M5,the mixing ratio is:cement:fly ash:light sand:water:micro foam agent:water reducing agent=1:0.7:4.4:2.0:0.00326:0.096.%根据不同配合比研制的粉煤灰掺量13.6%的3组,粉煤灰掺量11.5%的3组,共6组M5粉煤灰砂浆.经过3天自然养护,对其进行了抗压强度试验,研究粉煤灰砂浆早期抗压强度的影响因素.试验研究表明:引气剂(微沫剂)掺入会降低粉煤灰砂浆的早期强度.减水剂的掺入可以提高粉煤灰砂浆的早期强度.减水剂掺量一定时,水胶比越小,粉煤灰水泥的早期抗压强度越高.从6组试件中选出28天抗压强度可达M5以上的粉煤灰砂浆,其配合比为:水泥:粉煤灰:轻砂:水:微沫剂:减水剂=1:0.7:4.4:2.0:0.00326:0.096.

  20. Nematode Locomotion in Unconfined and Confined Fluids

    CERN Document Server

    Bilbao, Alejandro; Vanapalli, Siva; Blawzdziewicz, Jerzy

    2013-01-01

    The millimeter-long soil-dwelling nematode {\\it C. elegans} propels itself by producing undulations that propagate along its body and turns by assuming highly curved shapes. According to our recent study [PLoS ONE \\textbf{7}, e40121 (2012)] all these postures can be accurately described by a piecewise-harmonic-curvature (PHC) model. We combine this curvature-based description with highly accurate hydrodynamic bead models to evaluate the normalized velocity and turning angles for a worm swimming in an unconfined fluid and in a parallel-wall cell. We find that the worm moves twice as fast and navigates more effectively under a strong confinement, due to the large transverse-to-longitudinal resistance-coefficient ratio resulting from the wall-mediated far-field hydrodynamic coupling between body segments. We also note that the optimal swimming gait is similar to the gait observed for nematodes swimming in high-viscosity fluids. Our bead models allow us to determine the effects of confinement and finite thickness...

  1. Nematode locomotion in unconfined and confined fluids

    Science.gov (United States)

    Bilbao, Alejandro; Wajnryb, Eligiusz; Vanapalli, Siva A.; Blawzdziewicz, Jerzy

    2013-08-01

    The millimeter-long soil-dwelling nematode Caenorhabditis elegans propels itself by producing undulations that propagate along its body and turns by assuming highly curved shapes. According to our recent study [V. Padmanabhan et al., PLoS ONE 7, e40121 (2012), 10.1371/journal.pone.0040121] all these postures can be accurately described by a piecewise-harmonic-curvature model. We combine this curvature-based description with highly accurate hydrodynamic bead models to evaluate the normalized velocity and turning angles for a worm swimming in an unconfined fluid and in a parallel-wall cell. We find that the worm moves twice as fast and navigates more effectively under a strong confinement, due to the large transverse-to-longitudinal resistance-coefficient ratio resulting from the wall-mediated far-field hydrodynamic coupling between body segments. We also note that the optimal swimming gait is similar to the gait observed for nematodes swimming in high-viscosity fluids. Our bead models allow us to determine the effects of confinement and finite thickness of the body of the nematode on its locomotion. These effects are not accounted for by the classical resistive-force and slender-body theories.

  2. Evaluation of W/P Ratio, Setting Time and Compressive Strength of Dental Stone Type III and IV Marketed in Jakarta

    Directory of Open Access Journals (Sweden)

    Yosi Kusuma Eriwati

    2015-10-01

    Full Text Available Dental gypsum products in Indonesia are mainly imported from countries with non-tropical weather. Mostly, these gypsum products marketed in Jakarta are without adequate packaging, data or manipulative and maintenance instructions, which can cause misuse & abuse in the materials manipulation and handling. The purpose of this study was to evaluate the W/P ratio, setting time and compressive strength of dental stone type III and IV in relation with room temperature condition and relative humidity in Jakarta, Indonesia. One hundred and eighty dental stone Type III (unlabelled Blue Hard Stone; Giludur, Germany: Moldaroc, Germany and Type IV (New Fujirock, Japan; Glastone, USA; unlabelled Quickstone specimens were made as recommended by ISO 6873-1983 for setting time (with Vicat needle and compressive strength determination (Shimadzu mechanical testing machine with W/P ratio variables of 0.28; 0.29; 0.30 for Type III and 0.20; 0.21; 0.22 for type IV. The tests were conducted in 2 rooms with different temperature and humidity and with and without air-conditioned. Statistical analysis using T-test. The results shows that the increasing of W/P ratio will decrease the dental stone type III and IV setting time. Jakarta condition of high room temperature and relative humidity significantly shorten the setting time of Moldaroc and New Fujirock. The rest of the stones were reduced statistically insignificant. It can be concluded that the temperature and humidity in Jakarta can influence the setting time and compressive strength of dental stone type III and IV. However, since the setting time and strength values are still within the ISO standard, these stones can be accepted and used in Indonesia.

  3. Specimen size effects on the compressive strength and Weibull modulus of nuclear graphite of different coke particle size: IG-110 and NBG-18

    Energy Technology Data Exchange (ETDEWEB)

    Chi, Se-Hwan, E-mail: shchi@kaeri.re.kr [Nuclear Hydrogen Development and Demonstration Project, Korea Atomic Energy Research Institute, 1045 Daedeok Daero, Yuseong, Daejeon 305-353 (Korea, Republic of)

    2013-05-15

    The effects of specimen size on the compressive strength and Weibull modulus were investigated for nuclear graphite of different coke particle sizes: IG-110 and NBG-18 (average coke particle size for IG-110: 25 μm, NBG-18: 300 μm). Two types of cylindrical specimens, i.e., where the diameter to length ratio was 1:2 (ASTM C 695-91 type specimen, 1:2 specimen) or 1:1 (1:1 specimen), were prepared for six diameters (3, 4, 5, 10, 15, and 20 mm) and tested at room temperature (compressive strain rate: 2.08 × 10{sup −4} s{sup −1}). Anisotropy was considered during specimen preparation for NBG-18. The results showed that the effects of specimen size appeared negligible for the compressive strength, but grade-dependent for the Weibull modulus. In view of specimen miniaturization, deviations from the ASTM C 695-91 specimen size requirements require an investigation into the effects of size for the grade of graphite of interest, and the specimen size effects should be considered for Weibull modulus determination.

  4. Strength and Stiffness Development in Soft Soils: A FESEM aided Soil Microstructure Viewpoint

    Science.gov (United States)

    Wijeyesekera, D. C.; Ho, M. H.; Bai, X.; Bakar, I.

    2016-07-01

    This paper opens with an overview of the debatable definition of soft soil that goes beyond a (CH) organic / inorganic clay and OH peat to include weakly cemented periglacial deposits of loess and alike. It then outlines the findings obtained from stiffness test on cement-stabilised soft clay. The findings are complemented with a microstructure viewpoint obtained using field emission scanning electron microscope (FESEM). Research also comprised of making cylindrical stabilised clay samples, prepared in the laboratory with various rubber chips contents and cement, and then aged for 28 days. The samples were then subjected to unconfined compressive strength (UCS) test and observations were also made of its microstructure using the FESEM. The impact of the soil microstructure on the stiffness result was studied both with the stabilized soil and also of some of the natural undisturbed loess soils. Sustainability aspect and the potential of the use of rubber chips and sand as additives to cement stabilisation are also discussed. The overall test results indicated that rubber chips and sand contributed to the improvement in unconfined compressive strength (qu). The derogatory influence of moisture on the stiffness of the stabilised clay was studied simultaneously. SEM micrographs are presented that show bonding of cement, rubber chips/ sand and soft clay, granular units and aggregated / agglomerated units in loess. The paper concludes with observations on the dependence of soil microstructure on the soil strength and deformability and even collapsibility of the loess. Current practices adopted as engineering solutions to these challenging soils are outlined.

  5. 圆柱体钢筋混凝土柱的轴压强度%Strength of circular concrete columns under concentric compression

    Institute of Scientific and Technical Information of China (English)

    赵玲; 李爱群

    2003-01-01

    An experimental study, in which six columns were loaded concentrically to investigate the behavior of reinforced normal strength and high strength circular colu mns under concentric compression, is described. The concrete strengths of the c olumns were 30 Mpa and 60 Mpa. The primary variables considered were the concrete strength and the amount of transverse reinforcement. Test results indi cate that smaller hoop spacing provides higher column capacity and greater stre ngth enhancement in a confined concrete core of columns. For the same lateral co nfinement, high strength concrete columns develop lower strength enhancement than normal strength concrete columns. Both the strength enhancement ratio (f ′cc/f ′co) and the column capacity ratio (Ptest/Po) were observed to show linear increase variations with ρsfyt/f ′c in circular columns.%通过对6根圆柱体钢筋混凝土柱的轴压试验,研究普通及高强混凝土柱的轴向受压性能.柱的混凝土强度为30 MPa和60 MPa.所考虑的主要因素为混凝土强度和箍筋用量.试验结果表明 ,箍筋间距越小,则柱承载能力越高,混凝土核心约束强度提高幅度越大.在相同的侧向约束下 ,高强混凝土柱的核心强度提高幅度低于普通混凝土柱.混凝土核心约束强度与非约束强度比率(fcc ′ /fco ′)及柱承载能力试验值与理论值之比(Ptest/Po)均与约束率ρs/fyt/ f ′c成正比.

  6. Surface Modification of Fly Ashes with Carbide Slag and Its Effect on Compressive Strength and Autogenous Shrinkage of Blended Cement Pastes

    Institute of Scientific and Technical Information of China (English)

    HAO Chengwei; DENG Min; MO Liwu; LIU Kaiwei

    2012-01-01

    Surfaces of grade Ⅲ fly ashes were modified through mixing with carbide slag and calcining at 850 ℃ for 1 h.Mineralogical compositions and surface morphology of fly ashes before and after modification were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM),respectively.Effect of surface-modified fly ashes on compressive strength and autogenous shrinkage of blended cement pastes was investigated.Microstructures of cement pastes were examined by backscattered electron (BSE) imaging and mercury intrusion porosimetry (MIP).The experimental results showed that β-C2S was formed on the surfaces of fly ashes after modification.Hydration of β-C2S on the surface-modified fly ashes densified interface zone and enhanced bond strength between particles of fly ashes and hydrated clinkers.In addition,surface modification of fly ashes tended to decrease total porosity and 10-50 nm pores of cement pastes.Surface modification of fly ashes increased compressive strength and reduced autogenous shrinkage of cement pastes.

  7. Size effect of compressive strength of cemented backfill%胶结充填体力学强度尺寸效应

    Institute of Scientific and Technical Information of China (English)

    彭志华

    2009-01-01

    本文通过尾砂胶结充填体配比试验,研究了尾砂胶结充填体强度与试样尺寸和几何形状之间的关系.试验研究结果表明:在相同条件下,胶结充填体强度在试验范围内,随试样尺寸的增加而减小,其呈非线性变化;不同尺寸与几何形状的胶结充填体试样强度之间的换算比例关系为:152mm充填体试样强度大致为72mm和85mm试样强度的3/4,为70.7mm立方体试样强度的3/5.%This paper researches relation of compressive strength of cemented tailings fill and size、geometries of cemented backfill. The test results show under same condition compressive strength of cemented tailings fill will minish with size increasing, it show itself non-linear variety. 150mm diameter cylinder specimen fill strength averaged approximately three-quarter of 72mm and 85mm diameter cylinders specimen, about three fifths of 70.7mm cubes specimen.

  8. A comparative evaluation of compressive strength of Portland cement with zinc oxide eugenol and Polymer-reinforced cement: An in vitro analysis

    OpenAIRE

    S.Prakasam; Prakasam Bharadwaj; S C Loganathan; B Krishna Prasanth

    2014-01-01

    Objective: The purpose of this study is to evaluate the ultimate compressive strength of 50% and 25% Portland cement mixed with Polymer-reinforced zinc oxide eugenol and zinc oxide eugenol cement after 1 hour, 24 hours, and 7 days. Materials and Methods: One hundred and eighty samples were selected. The samples were made cylindrical of size 6 × 8 mm and were divided into six groups as follows with each group consisting of 10 samples. Group 1: Polymer-reinforced zinc oxide eugenol with...

  9. Conditions pertaining to the influence of electrode surface roughness upon the insulation strength of compressed SF6 systems

    DEFF Research Database (Denmark)

    McAllister, Iain Wilson; Crichton, George C

    1997-01-01

    On the basis of a series of experimental investigations reported in the literature, electrode microscopic surface roughness was dismissed as a factor influencing breakdown levels in compressed SF6, irrespective of field non-uniformity. This conclusion appears to be tenable if one restricts observ...

  10. New phosphate-based binder for stabilization of soils contaminated with heavy metals: leaching, strength and microstructure characterization.

    Science.gov (United States)

    Du, Yan-Jun; Wei, Ming-Li; Reddy, Krishna R; Jin, Fei; Wu, Hao-Liang; Liu, Zhi-Bin

    2014-12-15

    Cement stabilization is used extensively to remediate soils contaminated with heavy metals. However, previous studies suggest that the elevated zinc (Zn) and lead (Pb) concentrations in the contaminated soils would substantially retard the cement hydration, leading to the deterioration of the performance of cement stabilized soils. This study presents a new binder, KMP, composed of oxalic acid-activated phosphate rock, monopotassium phosphate and reactive magnesia. The effectiveness of stabilization using this binder is investigated on soils spiked with Zn and Pb, individually and together. Several series of tests are conducted including toxicity characteristic leaching (TCLP), ecotoxicity in terms of luminescent bacteria test and unconfined compressive strength. The leachability of a field Zn- and Pb- contaminated soil stabilized with KMP is also evaluated by TCLP leaching test. The results show that the leached Zn concentrations are lower than the China MEP regulatory limit except when Zn and Pb coexist and for the curing time of 7 days. On the other hand, the leached Pb concentrations for stabilized soils with Pb alone or mixed Zn and Pb contamination are much lower than the China MEP or USEPA regulatory limit, irrespective of the curing time. The luminescent bacteria test results show that the toxicity of the stabilized soils has been reduced considerably and is classified as slightly toxic class. The unconfined compressive strength of the soils decrease with the increase in the Zn concentration. The stabilized soils with mixed Zn and Pb contaminants exhibit notably higher leached Zn concentration, while there is lower unconfined compressive strength relative to the soils when contaminated with Zn alone. The X-ray diffraction and scanning electron microscope analyses reveal the presence of bobierrite (Mg3(PO4)2·8H2O) and K-struvite (MgKPO4·6H2O) as the main products formed in the KMP stabilized uncontaminated soils; the formation of hopeite (Zn3(PO4)2·4H2O

  11. An experimental method of measuring the confined compression strength of high-performance concretes to analyse their ballistic behaviour

    Science.gov (United States)

    Forquin, P.; Árias, A.; Zaera, R.

    2006-08-01

    The test known as “quasi-oedometric compression” consists of the compression of a cylindrical specimen confined in a thick vessel. In this work, an original methodology is proposed to deduce the radial stress and strain within the specimen using hoop strains measured on the external surface of the vessel, taking into account its elasto-plastic deformation. On one hand the spherical and deviatoric behaviours of two concretes are deduced. On the other hand, their ballistic behaviour is analysed using impact tests. These experiments are simulated numerically by the plasticity model of Krieg, Swenson and Taylor, and the features of the model are identified by the previous confined compression tests. The capacity of the model to describe the ballistic behaviour of such materials is shown in a comparison of the numerical simulations with the ballistic tests.

  12. Application of Geostatistical Modelling to Study the Exploration Adequacy of Uniaxial Compressive Strength of Intact Rock alongthe Behesht-Abad Tunnel Route

    Directory of Open Access Journals (Sweden)

    Mohammad Doustmohammadi

    2014-12-01

    Full Text Available Uniaxial compressive strength (UCS is one of the most significant factors on the stability of underground excavation projects. Most of the time, this factor can be obtained by exploratory boreholes evaluation. Due to the large distance between exploratory boreholes in the majority of geotechnical projects, the application of geostatistical methods has increased as an estimator of rock mass properties. The present paper ties the estimation of UCS values of intact rock to the distance between boreholes of the Behesht-Abad tunnel in central Iran, using SGEMS geostatistical program. Variography showed that UCS estimation of intact rock using geostatistical methods is reasonable. The model establishment and validation was done after assessment that the model was trustworthy. Cross validation proved the high accuracy (98% and reliability of the model to estimate uniaxial compressive strength. The UCS values were then estimated along the tunnel axis. Moreover, using geostatistical estimation led to better identification of the pros and cons of geotechnical explorations in each location of tunnel route.

  13. Influence of the waste glass in the axial compressive strength of Portland cement concrete; Influencia dos residuos vitreos na resistencia a compressao axial do concreto de cimento Portland

    Energy Technology Data Exchange (ETDEWEB)

    Miranda Junior, E.J.P.; Paiva, A.E.M., E-mail: edson.jansen@hotmail.com [Instituto Federal de Educacao, Ciencia e Tecnologia do Maranhao (PPGEM/IFMA), Sao Luis, MA (Brazil). Programa de Pos-Graduacao em Engenharia de Materiais

    2012-07-01

    In this work, was studied the influence of the incorporation of waste glass, coming from the stage of thinning and polishing of a company of thermal glass treatments, in the axial compressive strength of Portland cement concrete. The coarse and ground aggregates used was crushed stone and sand, respectively. For production of the concrete, percentages of glass residues of 5%, 10% and 20% had been used in substitution to the sand, and relations water/cement (a/c) 0,50, 0,55 and 0,58. The cure of the test bodies was carried through in 7, 14 and 28 days. The statistics analysis of the results was carried out through of the analysis of variance for each one of the cure times. From the results of the compressive strength of the concrete, it could be observed that the concrete has structural application for the relation a/c 0,5, independently of waste glass percentage used, and for the relation a/c 0,55 with 20% of waste glass. (author)

  14. A comparative evaluation of compressive strength of Portland cement with zinc oxide eugenol and Polymer-reinforced cement: An in vitro analysis

    Directory of Open Access Journals (Sweden)

    S Prakasam

    2014-01-01

    These samples were further subdivided based on time interval and were tested at 1 hour, 24 hours and at 7 th day. After each period of time all the specimens were tested by vertical CVR loaded frame with capacity of 5 tones/0473-10kan National Physical laboratory, New Delhi and the results were statistically analyzed using ANOVA and Scheffe test. Results: Polymer-reinforced cement with 50% Portland cement, Zinc oxide with 50% Portland cement, Polymer-reinforced cement with 25% Portland cement and Zinc oxide with 25% Portland cement exhibited higher compressive strength when compared to Zinc oxide with 0% Portland cement and Polymer-reinforced cement with 0% Portland cement, at different periods of time. The difference between these two groups were statistically significant (P < 0.05 and it is suggested that mixture of 50% and 25% Portland cement in Zinc oxide eugenol and Polymer-modified zinc oxide cement can be used as core build up material and permanent filling material. Conclusion: It is concluded that 50% and 25% Portland cement in zinc oxide eugenol and polymer-modified zinc oxide eugenol results in higher compressive strength and hence can be used as permanent filling material and core built-up material.

  15. Analysis of Factors Affecting the Compressive Strength of Cemented Backfill%胶结充填体抗压强度的影响因素分析

    Institute of Scientific and Technical Information of China (English)

    杨安国; 周宗红; 张秋华

    2014-01-01

    This paper introduces some factors influencing the compressive strength of cemented filling body, in order to demonstrate that the compressive strength of cemented filling body is affected by cementitious materials, inert material, slurry concentration, material ratio and curing conditions. In addition, this paper also points out some problems in mine cemented filling process and the improvement direction.%本文通过介绍影响胶结充填体抗压强度的若干因素,目的是为了说明胶结充填体抗压强度受到胶凝材料、惰性材料、料浆浓度以及物料配比和养护条件等因素的影响。此外,本文还指出了目前矿山胶结在充填过程中存在的一些问题以及改进的方向。

  16. Effect of Polyvinyl Alcohol (PVA Blending and Gamma Irradiation on Compressive Strength of FHAp/FGel Composite as Candidate of Scaffold

    Directory of Open Access Journals (Sweden)

    Alva Edy Tontowi

    2016-02-01

    Full Text Available Composite as candidate of scaffold have been synthesized from fish hydroxyapatite (FHAp and fish gelatin (FGel of Barramundi (Lates calcarifer Bloch scale that aqua-cultured in Jakarta Bay, Indonesia. The effect of polyvinyl alcohol (PVA blending was investigated for improvement of compressive strength of composites. Composites were synthesized by wet method at FGel/PVA percent mass ratio of 10/0, 7.5/2.5, 5.0/5.0, and 7.5/2.5 (w/w, respectively. Sodium citrate was used as dispersant to forming a paste-like suspension condition. Porous composites were obtained after freeze-drying of suspensions. Compressive strength and Young’s modulus of scaffold were increased as increasing PVA content. FTIR spectra confirmed the molecular interaction among components of composite. SEM micrograph showed fibrous and ribbon structure over surface of FHAp/FGel composite that blended with PVA. Gamma irradiation lead to formation of micro- and mesopores in the wall surface of composite.

  17. Strength Restoration of Cracked Sandstone and Coal under a Uniaxial Compression Test and Correlated Damage Source Location Based on Acoustic Emissions

    Science.gov (United States)

    Feng, Xiaowei; Zhang, Nong; Zheng, Xigui; Pan, Dongjiang

    2015-01-01

    Underground rock masses have shown a general trend of natural balance over billions of years of ground movement. Nonetheless, man-made underground constructions disturb this balance and cause rock stability failure. Fractured rock masses are frequently encountered in underground constructions, and this study aims to restore the strength of rock masses that have experienced considerable fracturing under uniaxial compression. Coal and sandstone from a deep-buried coal mine were chosen as experimental subjects; they were crushed by uniaxial compression and then carefully restored by a chemical adhesive called MEYCO 364 with an innovative self-made device. Finally, the restored specimens were crushed once again by uniaxial compression. Axial stress, axial strain, circumferential strain, and volumetric strain data for the entire process were fully captured and are discussed here. An acoustic emission (AE) testing system was adopted to cooperate with the uniaxial compression system to provide better definitions for crack closure thresholds, crack initiation thresholds, crack damage thresholds, and three-dimensional damage source locations in intact and restored specimens. Several remarkable findings were obtained. The restoration effects of coal are considerably better than those of sandstone because the strength recovery coefficient of the former is 1.20, whereas that of the latter is 0.33, which indicates that MEYCO 364 is particularly valid for fractured rocks whose initial intact peak stress is less than that of MEYCO 364. Secondary cracked traces of restored sandstone almost follow the cracked traces of the initial intact sandstone, and the final failure is mainly caused by decoupling between the adhesive and the rock mass. However, cracked traces of restored coal only partially follow the traces of intact coal, with the final failure of the restored coal being caused by both bonding interface decoupling and self-breakage in coal. Three-dimensional damage source

  18. Strength Restoration of Cracked Sandstone and Coal under a Uniaxial Compression Test and Correlated Damage Source Location Based on Acoustic Emissions.

    Directory of Open Access Journals (Sweden)

    Xiaowei Feng

    Full Text Available Underground rock masses have shown a general trend of natural balance over billions of years of ground movement. Nonetheless, man-made underground constructions disturb this balance and cause rock stability failure. Fractured rock masses are frequently encountered in underground constructions, and this study aims to restore the strength of rock masses that have experienced considerable fracturing under uniaxial compression. Coal and sandstone from a deep-buried coal mine were chosen as experimental subjects; they were crushed by uniaxial compression and then carefully restored by a chemical adhesive called MEYCO 364 with an innovative self-made device. Finally, the restored specimens were crushed once again by uniaxial compression. Axial stress, axial strain, circumferential strain, and volumetric strain data for the entire process were fully captured and are discussed here. An acoustic emission (AE testing system was adopted to cooperate with the uniaxial compression system to provide better definitions for crack closure thresholds, crack initiation thresholds, crack damage thresholds, and three-dimensional damage source locations in intact and restored specimens. Several remarkable findings were obtained. The restoration effects of coal are considerably better than those of sandstone because the strength recovery coefficient of the former is 1.20, whereas that of the latter is 0.33, which indicates that MEYCO 364 is particularly valid for fractured rocks whose initial intact peak stress is less than that of MEYCO 364. Secondary cracked traces of restored sandstone almost follow the cracked traces of the initial intact sandstone, and the final failure is mainly caused by decoupling between the adhesive and the rock mass. However, cracked traces of restored coal only partially follow the traces of intact coal, with the final failure of the restored coal being caused by both bonding interface decoupling and self-breakage in coal. Three

  19. Strength Restoration of Cracked Sandstone and Coal under a Uniaxial Compression Test and Correlated Damage Source Location Based on Acoustic Emissions.

    Science.gov (United States)

    Feng, Xiaowei; Zhang, Nong; Zheng, Xigui; Pan, Dongjiang

    2015-01-01

    Underground rock masses have shown a general trend of natural balance over billions of years of ground movement. Nonetheless, man-made underground constructions disturb this balance and cause rock stability failure. Fractured rock masses are frequently encountered in underground constructions, and this study aims to restore the strength of rock masses that have experienced considerable fracturing under uniaxial compression. Coal and sandstone from a deep-buried coal mine were chosen as experimental subjects; they were crushed by uniaxial compression and then carefully restored by a chemical adhesive called MEYCO 364 with an innovative self-made device. Finally, the restored specimens were crushed once again by uniaxial compression. Axial stress, axial strain, circumferential strain, and volumetric strain data for the entire process were fully captured and are discussed here. An acoustic emission (AE) testing system was adopted to cooperate with the uniaxial compression system to provide better definitions for crack closure thresholds, crack initiation thresholds, crack damage thresholds, and three-dimensional damage source locations in intact and restored specimens. Several remarkable findings were obtained. The restoration effects of coal are considerably better than those of sandstone because the strength recovery coefficient of the former is 1.20, whereas that of the latter is 0.33, which indicates that MEYCO 364 is particularly valid for fractured rocks whose initial intact peak stress is less than that of MEYCO 364. Secondary cracked traces of restored sandstone almost follow the cracked traces of the initial intact sandstone, and the final failure is mainly caused by decoupling between the adhesive and the rock mass. However, cracked traces of restored coal only partially follow the traces of intact coal, with the final failure of the restored coal being caused by both bonding interface decoupling and self-breakage in coal. Three-dimensional damage source

  20. The use of coal fly ash in concrete for marine artificial reefs in the southeastern Mediterranean: compressive strength, sessile biota, and chemical composition

    Energy Technology Data Exchange (ETDEWEB)

    Kress, N.; Tom, M.; Spanier, E. [National Institute of Oceanography, Haifa (Israel)

    2002-07-01

    To examine the possible use of coal fly ash (CFA) in concrete for artificial reefs, blocks containing 0%, 40%, 60% and 80% CFA as a substitute for sand were deployed in the Mediterranean at 18.5-m depth off the coast of Israel during a period of 33 months. Changes in compressive strength, composition, and coverage of sessile biota species, as well as in trace element concentration of the block surface and in sessile biota from four taxonomic groups, were determined as a function of time at sea and block type. Compressive strength clearly increased with time in all types to values well above the minimal strength considered necessary for stability of the blocks at sea. Moreover, the 40% and 60% CFA blocks were 1.5 times stronger than the 0% and 80% ones. Main sessile taxa recorded were filamentous green algae, bryozoa, barnacles, serpulid polychaeta, hydrozoa, and bivalves. Number of species settled and biotic coverage varied among block side and seasonally, but did not differ significantly between block types. The initial heavy metal composition (Hg, Cd, Pb, Cu, Zn, Cr, Mn, Fe, Al) of the block material was directly proportional to the CFA percentage. At the end of the study, Pb had decreased in all types, Cd in the 60% CFA block, and Fe and Al in the 40% and 60% blocks, while Mn had increased in the blocks with 0% and 80% CFA. After 21 months at sea, the only detectable change was a decrease in Pb concentration in all types, indicating that changes may be due to long-term processes. Trace metal levels (Hg, Cd, Zn, Mn, Cu, Fe, and Al) were measured in the sessile biota (hydrozoa, polychaeta, and bivalvia). In most cases, no dependence was found between metal levels and time at sea or CFA content of the blocks. In the hydroid, metal concentration even decreased over time.

  1. Experimental observation and theoretical modeling of the effect of magnetic field on the strength of molybdenum under ramp wave compression

    Science.gov (United States)

    Ding, Jow; Alexander, C.; Asay, James

    2013-06-01

    A new experimental technique has been developed at Sandia National Labs to study the dynamic material strength at high pressures using ``magnetically applied pressure shear (MAPS)'' ramp waves. In order to apply sufficient shear traction to the test sample, the driver must have substantial strength. Molybdenum was selected for this reason along with its good electrical conductivity. It was observed that an imposed magnetic field of around 10 Tesla induced some annealing on molybdenum. Furthermore, when subjected directly to magnetohydrodynamic loading as encountered for the driver material, molybdenum exhibited an apparently stiff response and did not show a discernible elastic plastic transition. To better understand the experiments and establish a predictive capability for molybdenum, a tentative strength model that incorporates the possible magnetic effects including magnetic diffusion, Joule heating, and the coupling between the magnetic field and material strength has been developed. Experimental observations and the model will be discussed. Sandia National Labs is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corp., for the U.S. Dept. of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  2. Deflagration-to-Detonation Transition in Unconfined Media

    Science.gov (United States)

    Poludnenko, Alexei; Gardiner, Thomas; Oran, Elaine

    2011-11-01

    Deflagration-to-detonation transition (DDT) can occur in environments ranging from experimental and industrial systems on Earth to astrophysical thermonuclear supernovae explosions. In recent years, substantial progress has been made in elucidating the nature of this process in confined systems with walls, obstacles, etc. It remains unclear, however, whether a subsonic turbulent flame in an unconfined environment can undergo a DDT. We present simulations of premixed flames in stoichiometric H2-air and CH4-air mixtures interacting with high-intensity turbulence. These calculations demonstrate the DDT in unconfined systems unassisted by shocks or obstacles. We discuss the mechanism of this process and its implications.

  3. Three-dimensional groundwater velocity field in an unconfined aquifer under irrigation

    International Nuclear Information System (INIS)

    A method for three-dimensional flow velocity calculation has been developed to evaluate unconfined aquifer sensitivity to areal agricultural contamination of groundwater. The methodology of Polubarinova-Kochina is applied to an unconfined homogeneous compressible or incompressible anisotropic aquifer. It is based on a three-dimensional groundwater flow model with a boundary condition on the moving surface. Analytical solutions are obtained for a hydraulic head under the influence of areal sources of circular and rectangular shape using integral transforms. Two-dimensional Hantush formulas result from the vertical averaging of the three-dimensional solutions, and the asymptotic behavior of solutions is analyzed. Analytical expressions for flow velocity components are obtained from the gradient of the hydraulic head field. Areal and temporal variability of specific yield in groundwater recharge areas is also taken into account. As a consequence of linearization of the boundary condition, the operation of any irrigation system with respect to groundwater is represented by superposition of the operating wells and circular and rectangular source influences. Combining the obtained solutions with Dagan or Neuman well functions, one can develop computer codes for the analytical computation of the three-dimensional groundwater hydraulic head and velocity component distributions. Methods for practical implementation are discussed. (Author) (20 refs., 4 figs.)

  4. Compressive strength and resistance to chloride ion penetration and carbonation of recycled aggregate concrete with varying amount of fly ash and fine recycled aggregate.

    Science.gov (United States)

    Sim, Jongsung; Park, Cheolwoo

    2011-11-01

    Construction and demolition waste has been dramatically increased in the last decade, and social and environmental concerns on the recycling have consequently been increased. Recent technology has greatly improved the recycling process for waste concrete. This study investigates the fundamental characteristics of concrete using recycled concrete aggregate (RCA) for its application to structural concrete members. The specimens used 100% coarse RCA, various replacement levels of natural aggregate with fine RCA, and several levels of fly ash addition. Compressive strength of mortar and concrete which used RCA gradually decreased as the amount of the recycled materials increased. Regardless of curing conditions and fly ash addition, the 28 days strength of the recycled aggregate concrete was greater than the design strength, 40 MPa, with a complete replacement of coarse aggregate and a replacement level of natural fine aggregate by fine RCA up to 60%. The recycled aggregate concrete achieved sufficient resistance to the chloride ion penetration. The measured carbonation depth did not indicate a clear relationship to the fine RCA replacement ratio but the recycled aggregate concrete could also attain adequate carbonation resistance. Based on the results from the experimental investigations, it is believed that the recycled aggregate concrete can be successfully applied to structural concrete members. PMID:21784626

  5. Influence of fly ash and desert Sand content on the compressive strength of high strength concrete%掺粉煤灰、沙漠砂高强混凝土抗压强度研究

    Institute of Scientific and Technical Information of China (English)

    陈云龙; 马菊荣; 刘海峰; 宋建夏

    2014-01-01

    The orthogonal experiment was designed to analyze the influence of water-binder ratio,fly ash content,sand ratio and desert sand replacement ratio on the compressive strength of high strength concrete at the different age.The optimum mix ratio of desert sand high-strength concrete was also given out.Experimental result showed that it is practical to use the desert sand from Mu Us desert sand to mix high strength concrete,the optimum mix ratio of which was that water-binder ratio,fly ash dosage,sand ratio and desert sand replace-ment ratio were 0.24,10%,30% and 30%,respectively.%通过正交试验,分析了水胶比、粉煤灰掺量、砂率、沙漠砂取代率对不同龄期高强混凝土抗压强度影响,并给出了配制高强混凝土的最优配合比。研究结果表明:用沙漠砂替代中砂配制高强混凝土是可行的;综合考虑各阶段的抗压强度,高强混凝土的最优配合比为水胶比0.24、粉煤灰掺量10%、砂率30%、沙漠砂取代率30%。

  6. Effect of solution heat treatment on the internal architecture and compressive strength of an AlMg4.7Si8 alloy

    International Nuclear Information System (INIS)

    The evolution of the microstructure of an AlMg4.7Si8 alloy is investigated by scanning electron microscopy and ex situ synchrotron tomography in as-cast condition and subsequent solution treatments for 1 h and 25 h at 540 °C, respectively. The eutectic Mg2Si phase, which presents a highly interconnected structure in the as-cast condition, undergoes significant morphological changes during the solution heat treatment. Statistical analyses of the particle distribution, the sphericity, the mean curvatures and Gaussian curvatures describe the disintegration of the interconnected seaweed-like structure followed by the rounding of the disintegrated fractions of the eutectic branches quantitatively. The ternary eutectic Si resulting from the Si-surplus to the stoichiometric Mg2Si ratio of the alloy undergoes similar changes. The morphological evolution during solution heat treatment is correlated with results of elevated temperature compression tests at 300 °C. The elevated temperature compressive strength is more sensitive to the degree of interconnectivity of the three dimensional Mg2Si network than to the shape of the individual particles

  7. The compression strength investigations of AW-AlCu4Mg2Mn alloy based composites reinforced with SiC particles

    Directory of Open Access Journals (Sweden)

    A. Kurzawa

    2011-04-01

    Full Text Available In this paper strength tests of composite materials based on AW-AlCu4Mg2Mn obtained in uniaxial compression test was studied.Materials used for examination were made from AW-AlCu4Mg2Mn alloy and porous preforms of SiC particles (grain size 6÷10μm bypressure infiltration (squeeze casting. The stress-strain curves of the materials with 10% vol., 20% vol., 30% vol. particles of SiC, as well unreinforcement alloy and microstructure of scrap surface samples in a plane parallel to the compressive force were analyzed. The investigated metal matrix composites are characterized by marked reduced the plastic strain values with increasing particle strengthening while the unreinforcement materials throughout the range of deformation show considerable plasticity. In the case of the material containing 10% vol of SiC the plastic strain is a slight strengthening of the material. With increasing of the particle content the plasticity decreases. Materials with 20%vol and 30%vol of SiC particles were brittle cracked at much higher values of stress σ.

  8. Raman spectroscopic determination of the length, strength, compressibility, Debye temperature, elasticity, and force constant of the C-C bond in graphene.

    Science.gov (United States)

    Yang, X X; Li, J W; Zhou, Z F; Wang, Y; Yang, L W; Zheng, W T; Sun, Chang Q

    2012-01-21

    From the perspective of bond relaxation and bond vibration, we have formulated the Raman phonon relaxation of graphene, under the stimuli of the number-of-layers, the uni-axial strain, the pressure, and the temperature, in terms of the response of the length and strength of the representative bond of the entire specimen to the applied stimuli. Theoretical unification of the measurements clarifies that: (i) the opposite trends of the Raman shifts, which are due to the number-of-layers reduction, of the G-peak shift and arises from the vibration of a pair of atoms, while the D- and the 2D-peak shifts involve the z-neighbor of a specific atom; (ii) the tensile strain-induced phonon softening and phonon-band splitting arise from the asymmetric response of the C(3v) bond geometry to the C(2v) uni-axial bond elongation; (iii) the thermal softening of the phonons originates from bond expansion and weakening; and (iv) the pressure stiffening of the phonons results from bond compression and work hardening. Reproduction of the measurements has led to quantitative information about the referential frequencies from which the Raman frequencies shift as well as the length, energy, force constant, Debye temperature, compressibility and elastic modulus of the C-C bond in graphene, which is of instrumental importance in the understanding of the unusual behavior of graphene.

  9. Hydraulic Tomography to Characterization of Heterogeneity of Unconfined Aquifers

    Science.gov (United States)

    Zhu, J.; Yeh, T. J.

    2008-12-01

    Analytical models are the most widely used methods for analyzing pumping tests in unconfined aquifers. However, one major group analytical models assume instantaneous and complete drainage at the water table and therefore are inadequate to account for gradual drainage of water from the vadose zone due to pumping; the other major group analytical models use an exponential function of drawdown at the water table to account for gradual drainage and are subsequently limited to represent the highly non-linear flow in the vadose zone. Moreover, both models assume aquifer homogeneity while the natural aquifers are inherently heterogeneous. Recently emerged Hydraulic tomography (HT) is a cost-effective method for mapping spatial distribution of aquifer hydraulic properties. HT takes advantage of the power of numerical models and fuses information from multiple cross-hole tests conducted at different locations to image aquifers in great details. In this study, we apply HT concept to unconfined aquifers. To accurately simulate the flow behavior due to a HT survey in an unconfined aquifer, a fully three dimensional variably saturated flow model based on mixed form of Richards equation is used. Pressure responses in both saturated and unsaturated zones are used to estimate spatial variations of hydraulic conductivity, specific storage, and soil water constitutive model parameters through a sequential successive linear estimator. A systematic approach that uses wavelet analysis, least-square method, and fuzzy similarity compassion is applied for data denoising, statistic inputs, convergence, and performance assessment. A cross-correlation is also performed to investigate the relation between pressure change and different parameters. The HT method for unconfined aquifers is tested in a synthetic aquifer. The tests show that the proposed HT method effectively maps heterogeneity of the unconfined aquifer and predicts the vadose zone responses due to a pumping test more accurately

  10. Scaling laws of nanoporous gold under uniaxial compression: Effects of structural disorder on the solid fraction, elastic Poisson's ratio, Young's modulus and yield strength

    Science.gov (United States)

    Roschning, B.; Huber, N.

    2016-07-01

    In this work the relationship between the structural disorder and the macroscopic mechanical behavior of nanoporous gold under uniaxial compression was investigated, using the finite element method. A recently proposed model based on a microstructure consisting of four-coordinated spherical nodes interconnected by cylindrical struts, whose node positions are randomly displaced from the lattice points of a diamond cubic lattice, was extended. This was done by including the increased density as result of the introduced structural disorder. Scaling equations for the elastic Poisson's ratio, the Young's modulus and the yield strength were determined as functions of the structural disorder and the solid fraction. The extended model was applied to identify the elastic-plastic behavior of the solid phase of nanoporous gold. It was found, that the elastic Poisson's ratio provides a robust basis for the calibration of the structural disorder. Based on this approach, a systematic study of the size effect on the yield strength was performed and the results were compared to experimental data provided in literature. An excellent agreement with recently published results for polymer infiltrated samples of nanoporous gold with varying ligament size was found.

  11. Strength Development of Lime Treated Artificial Organic Soil

    Science.gov (United States)

    Yeo, S. W.; Ling, F. N. L.; Sulaeman, A.; Low, V. S.; Toh, K. L.

    2016-07-01

    In over many years, considerable research has been carried out on organic soils which consists of various components of organic matter but the effect of particular organic matter is less reported. Thus, some of contributing factors for each organic matter are not fully understood yet. Hence, the aim of this study is to determine the effect of organic acid concentration on the strength of artificial organic soil. There are four types of artificial organic soil created by mixing kaolin (inorganic matter) and organic acid (a kind of humified organic matter) in different concentrations. Unconfined Compressive Strength test (UCT) was carried out for all soil samples after being cured for 7 and 28 days under room temperature and 50°C. Soil samples shows highest strength when cured for 28 days under 50°C compared to those cured under room temperature. However, when the organic acid concentration decrease, the strength increased for soil 2 after 7 and 28 days cured under room temperature and 50°C. Apart from this, soil 3 and soil 4 that were cured under room temperature shows decrease in strength when the organic acid concentration decreasing but different result shown for both samples when cured under 50°C.

  12. TNT Equivalency of Unconfined Aerosols of Propylene Oxide

    Directory of Open Access Journals (Sweden)

    A. Apparao

    2014-09-01

    Full Text Available The unconfined aerosols of propylene oxide (PO are formed by dispersing the fuel in air. These aerosols undergo detonation by suitable initiation and produce high impulse blast. Tri-nitro Toluene (TNT equivalence is an important parameter used to represent the power of explosive materials and compare their relative damage effects wrt TNT. The parameters commonly used for estimation of TNT equivalency are total energy of explosive source and properties of resulting blast wave, viz., blast peak overpressure and positive impulse. In the present study, the unconfined aerosols of 4.2 kg PO were formed by breaking open the cylindrical canister with the help of axially positioned central burster charge and then detonated using a secondary explosive charge after a preset time delay. The resulting blast profiles were recorded and the blast parameters were analysed. Being a non-ideal explosive source, the TNT equivalency depends on fraction of total energy utilised for blast formation, the rate of energy release, cloud dimensions, and concentration of fuel. Hence, various approaches based on energy release, experimental blast profiles, triangulated blast parameters, and ground reflected blast parameters were considered to determine the TNT equivalency of unconfined PO aerosols. It was observed that the TNT equivalency is not a single value but vary with distance. The paper provides various options for weapon designer to choose a suitable approach for considering TNT equivalency. The scaling laws established from the experimental data of unconfined aerosols of PO for blast peak over pressure and scaled impulse help in predicting the performance for different values of fuel weight and distance.Defence Science Journal, Vol. 64, No. 5, September 2014, pp.431-437, DOI:http://dx.doi.org/10.14429/dsj.64.6851

  13. 水泥搅拌砂土强度特性及影响因素研究%Study on Strength Characteristics and Influence Factors of Sand Mixing Cement

    Institute of Scientific and Technical Information of China (English)

    马殷军

    2014-01-01

    The saturated loess foundation with sand lens is mostly distributed along the railway project of Lanzhou to Zhongchuan Airport,so the cement mixed pile foundation is applied.The strength properties of cement mixing sand are studied by experiment in different lime-fly ash in-corporation ratios,curing time and stirring uniformity,and the variation of unconfined compres-sive strength of the cement mixing sand is analyzed.The results show that the unconfined com-pressive strength of cement mixing sand increases with the increase of lime-fly ash incorporation, whose increasing from 7% to 20% makes the unconfined compressive strength of cement mixing sand increase by 160.1%,and it increases with the growth of curing period;it grows rapidly dur-ing 7 d to 28 d,and still grows much after 28 d;the compressive strength of age 90 d has good cor-relation with that of 28 d,so the strength of 28 d can be predicted from that of 90 d,thus to short-en the test cycle;furthermore,the unconfined compressive strength of cement mixed soil increases obviously with the increase of stirring uniformity,and the unconfined compressive strength of uni-form specimen increases by 238%~263% than that of uneven specimen.%兰州至中川机场铁路工程沿线大多地段为饱和黄土地基,设计采取水泥土搅拌桩复合地基加固;该线部分地段饱和黄土地基中含有呈透镜状分布的砂土.对水泥搅拌砂土在不同的水泥和粉煤灰(以下简称“二灰”)掺合比、养护龄期、搅拌均匀程度下进行强度特性试验研究,分析了水泥搅拌砂土无侧限抗压强度的变化规律.试验表明:水泥搅拌砂土无侧限抗压强度随二灰掺量的增加而增加,二灰掺入量从7%增加到20%水泥搅拌砂土的无侧限抗压强度增长了160.1%;随养护龄期的增加而增大,7~28 d 增长较快,28 d 以后仍有较大程度的增长,龄期90 d 抗压强度与28 d 强度有

  14. Effect of Heat Treatment Upon the Compression Strength of Black Pine and Spruce – A Comparison Between Wood Originating From Mature Trees Vs. Thinnings

    Directory of Open Access Journals (Sweden)

    Cristina OLARESCU

    2013-06-01

    Full Text Available The paper presents the results of anexperimental study performed with black pine (Pinusnigra L. and spruce (Picea abies L. wood, originatingfrom mature trees and thinnings cut from the sameparcel from the Stroesti-Arges region in Romania.After air drying and conditioning, the defect-freetest boards were cut into standard 20x20x60mmsamples for the compression test. The compressionstrength was measured and the rupture mode incompression was analyzed.Therefore, the sampleswere first dried to oven-dry state, then heat-treated athigh temperatures (180 and 200ºC for 1, 2, 3 and 4hours. Sets of 10 samples from each wood species,wood assortment and treating regime were tested.The obtained results were comparativelyanalyzed for the two species (pine vs. spruce and forthe two wood assortments (mature wood vs, thinwood. Then they were also expressed relatively tothe mass loss, considered to be the main indiactor ofthe degradation suffered by wood during the heattreatment.A graph was drawn for each species andassortment in order to establish the optimum treatingregime, considering the correlated influence of theheat treatment conditions upon all three analyzedproperties (mass loss, dimensional stability andcompression strength.The results of the present research are to bevalorized at the manufacturing of solid wood panelsmade from heat-treated lamellas.

  15. Strength properties of soft clay treated with mixture of nano-SiO2 and recycled polyester fiber

    Directory of Open Access Journals (Sweden)

    Foad Changizi

    2015-08-01

    Full Text Available This paper investigates the effect of recycled polyester fiber, produced from polyethylene (PET bottles, in combination with nano-SiO2 as a new stabilizer to improve the mechanical properties of soils. We intend to study the effect of adding nano-SiO2 and recycled polyester fiber on soil engineering properties, especially the shear strength and unconfined compressive strength (UCS, using clayey soil with low liquid limit. Three different combinations of fiber-soil ratios ranging between 0.1% and 0.5% as well as three different combinations of nano-soil ratios ranging between 0.5% and 1% are used. The shear strength and UCS of treated specimens are obtained from direct shear test and unconfined compression test, respectively. Results of this study show that the addition of recycled polyester fiber and nano-SiO2 increases the strength of soil specimens. Both the shear strength and UCS are improved by increasing the contents of recycled polyester fiber and nano-SiO2 in the soil mixture. The increase in the nano-SiO2 content leads to a reduction in failure strain, but the increase in the content of recycled polyester fiber leads to an increase in failure strain. The increase in the contents of recycled polyester fiber and nano-SiO2 leads to an increase in elastic modulus of soils. Based on the test results, the addition of recycled polyester fiber improves the mechanical properties of soils stabilized with nano-SiO2 as well as the recycled polyester fiber has a positive effect on soil behaviors.

  16. Strength properties of soft clay treated with mixture of nano-SiO2 and recycled polyester fiber

    Institute of Scientific and Technical Information of China (English)

    Foad Changizi; Abdolhosein Haddad

    2015-01-01

    This paper investigates the effect of recycled polyester fiber, produced from polyethylene (PET) bottles, in combination with nano-SiO2 as a new stabilizer to improve the mechanical properties of soils. We intend to study the effect of adding nano-SiO2 and recycled polyester fiber on soil engineering properties, especially the shear strength and unconfined compressive strength (UCS), using clayey soil with low liquid limit. Three different combinations of fiber-soil ratios ranging between 0.1% and 0.5% as well as three different combinations of nano-soil ratios ranging between 0.5% and 1% are used. The shear strength and UCS of treated specimens are obtained from direct shear test and unconfined compression test, respectively. Results of this study show that the addition of recycled polyester fiber and nano-SiO2 increases the strength of soil specimens. Both the shear strength and UCS are improved by increasing the contents of recycled polyester fiber and nano-SiO2 in the soil mixture. The increase in the nano-SiO2 content leads to a reduction in failure strain, but the increase in the content of recycled polyester fiber leads to an increase in failure strain. The increase in the contents of recycled polyester fiber and nano-SiO2 leads to an increase in elastic modulus of soils. Based on the test results, the addition of recycled polyester fiber improves the mechanical properties of soils stabilized with nano-SiO2 as well as the recycled polyester fiber has a positive effect on soil behaviors.

  17. Computational Model of Fly Ash Concrete Compressive Strength Based on the Equivalent Age%基于等效龄期的粉煤灰混凝土抗压强度计算模型

    Institute of Scientific and Technical Information of China (English)

    王甲春; 阎培渝

    2014-01-01

    设计温度跟踪养护系统来模拟实际结构中混凝土所经历的温度历程,通过测试在标准养护条件20℃、恒温50℃和变温养护条件下不同强度等级的粉煤灰混凝土早龄期抗压强度的值,分析温度历程对粉煤灰混凝土早龄期抗压强度的影响。根据混凝土早龄期抗压强度的两个主要影响因素:温度和龄期,引入等效龄期理论建立了粉煤灰混凝土早龄期抗压强度的计算模型,并分析了模型参数。实际结构中的粉煤灰混凝土抗压强度可以通过测定温度场,利用计算模型进行相应龄期的抗压强度计算。研究结果表明,粉煤灰混凝土抗压强度计算模型能够较准确计算结构中粉煤灰混凝土的抗压强度,从而有效指导粉煤灰混凝土的工程应用。%Temperature tracking system is designed to simulate the actual curing concrete structure tem-perature history experienced .By the test standard curing conditions at 20℃, 50℃constant temperature and variable temperature curing conditions , early age compressive strength of different strength levels fly ash concrete is measured .According to the compressive strength of concrete at early age of the two main factors:temperature and age , the calculation model of compressive strength of fly ash concrete is estab-lished and analyze the model parameters with introduction of equivalent age theory .The compressive strength of fly ash concrete structures is predicted by measuring temperature field with computational mod -els.The results show that the compressive strength of fly ash concrete calculation model can accurately calculate the compressive strength of fly ash concrete structures , which can effectively guide the engineer-ing application of fly ash concrete .

  18. Electrostatic and Non-Electrostatic Contributions of Proteoglycans to the Compressive Equilibrium Modulus of Bovine Articular Cartilage

    OpenAIRE

    Guterl, Clare Canal; Hung, Clark T.; Ateshian, Gerard A.

    2010-01-01

    This study presents direct experimental evidence for assessing the electrostatic and nonelectrostatic contributions of proteoglycans to the compressive equilibrium modulus of bovine articular cartilage. Immature and mature bovine cartilage samples were tested in unconfined compression and their depth-dependent equilibrium compressive modulus was determined using strain measurements with digital image correlation analysis. The electrostatic contribution was assessed by testing samples in isoto...

  19. Double mixing fly ash and lime powder's influence on the compressive strength of concrete%粉煤灰石灰粉对再生细骨料混凝土抗压强度的影响

    Institute of Scientific and Technical Information of China (English)

    贾广测; 吴相豪; 朱涛

    2015-01-01

    Add lime to regeneration of fly ash concrete, can stimulate the activity of fly ash, promote the secondary hydration of fly ash. This topic proposed through experiment explore single mixing fly ash, double mixing fly ash and lime powder on the compressive strength of recycled fine aggregate concrete are studied, for the recycled fine aggregate concrete to provide theoretical basis for the popularization and application. Research process, the test is divided into two kinds of conditions: the first condition for single mixing fly ash; The second condition for double mixing fly ash and lime. Experiments show that: when only mixing fly ash, with the increasing dosage of fly ash, the compressive strength is first increases then decreases, and the content was 20%, the compressive strength is the largest. Double mixing fly ash and lime powder, the early compressive strength increases rapidly and the compressive strength increases with the increase of the dosage of lime powder is first reduced, after lime powder content was 4%, the compressive strength of recycled fine aggregate concrete is the largest.?%将石灰粉加入再生粉煤灰混凝土中,可激发粉煤灰的活性,促进粉煤灰的"二次水化".本课题拟通过试验探索单掺粉煤灰、双掺粉煤灰和石灰粉对再生细骨料混凝土抗压强度的影响规律,为再生细骨料混凝土的推广应用提供理论依据.研究过程中,试验分两种工况:第一种工况为单掺粉煤灰;第二种工况为双掺粉煤灰和石灰粉.实验表明:单掺粉煤灰时,随着粉煤灰掺量增加,抗压强度是先增大后减小,且掺量为20%时,抗压强度最大.双掺粉煤灰和石灰粉时,早期抗压强度增大较快,抗压强度随石灰粉掺量的增加是先增加后减小,石灰粉掺量为4%时,再生细骨料混凝土的抗压强度最大.

  20. In vitro study on compression strength of five kinds of provisional restorative materials.%暂时冠桥材料抗压强度的体外实验研究

    Institute of Scientific and Technical Information of China (English)

    邹康元; 张佩芬; 符镇南; 陈月明; 陈觉清

    2013-01-01

    目的:对比分析5种暂时冠桥材料的抗压强度.方法:参照标准制作直径4 mm,高6 mm的圆柱形试件50个,甲基丙烯酸酯即自凝树脂(A组)、Integrity(B组)、Luxatemp(C组)、Temphase(D组)、Protem 3 Garant(E组)5种暂时冠桥材料试件各10个,采用万能材料试验机测定其抗压强度,并进行统计分析.结果:A组抗压强度(210.28±20.07)MPa,显著低于其余4组(P <0.05),E组抗压强度最高(304.55±24.50)MPa,B、C、D组间无统计学差异(P >0.05),B、D、E组间也无显著性差异(P >0.05),C组和E组间抗压强度差异有统计学意义(P <0.05).结论:5种暂时冠桥材料抗压强度间存在较大差异,Bis-acryl类材料较甲基丙烯酸酯类材料抗压强度高.%Objective: To investigate the compression strength of five kinds of provisional restorative materials. Method: Fifty cylinder specimens were fabricated with 4mm in diameter and 6mm in height. Ten specimens were made of self-curing resin (group A) , Integrity (group B) , Luxatemp (group C) ,Temphase (group D) and Protemp 3 Garant (group E) respectively. Then the compression strength of all the specimens were tested by the universal testing machine. Result: The compression strength of group A was the lowest among the groups (P 0.05) , and it was also not significant difference among group B, D and E (P >0.05). While the significant difference in compression strength was found between group C and group E (P <0.05). Conclusion: The compression strength performance of five kinds of provisional restorative materials are significant difference. The Bis- acryl resins have higher compression strength than those of themethacrylate- based resins.

  1. Assessing the Performance of Statistical-structural and Geostatistical Methods in Estimating the 3D Distribution of the Uniaxial Compressive Strength Parameter in the Sarcheshmeh Porphyry Copper Deposit

    Directory of Open Access Journals (Sweden)

    Mahboubeh Pishbin

    2014-06-01

    Full Text Available The uniaxial compressive strength (UCS of intact rocks is an important geotechnical parameter required for designing geotechnical and mining engineering projects. Obtaining accurate estimates of the rock mass UCS parameter throughout a 3D geological model of the deposit is vital for determining optimum rock slope stability, designing new exploratory and blast boreholes, mine planning, optimizing the production schedule and even designing the crusher’s feed size. The main objective of this paper is to select the preferred estimator of the UCS parameter based on accuracy performance using all the available geological-geotechnical data at the Sarcheshmeh copper deposit, located 160 km southwest of Kerman City, in south-eastern Iran. In this paper, an attempt is made to estimate the spatial distribution of the UCS parameter using commonly-used statistical-structural and geostatistical methods. In order to achieve the aim of the current study, the UCS parameter was measured along with other qualitative geological properties, including the rock type, weathering, alteration type and intensity of core samples taken from 647 boreholes. The 3D distribution of the UCS parameter is obtained using different algorithms including statistical-structural (the nearest-neighbour technique, linear (ordinary Kriging and nonlinear (indicator Kriging geostatistical methods. After estimating the UCS parameter at block centres using the above-mentioned methods, the performance of each method is compared and validated through 21 set aside borehole data. The assessment of selecting best estimator of UCS parameter is based on scatter plots of the observed versus estimated data plus the root mean square error (RMSE statistics of the differences between observed and estimated values for 21 set aside borehole data. Finally, due to the special characteristics of the UCS spatial variability, it is concluded that the nearest-neighbour method is the most appropriate method for

  2. Concrete-Filled-Large Deformable FRP Tubular Columns under Axial Compressive Loading

    Directory of Open Access Journals (Sweden)

    Omar I. Abdelkarim

    2015-10-01

    Full Text Available The behavior of concrete-filled fiber tubes (CFFT polymers under axial compressive loading was investigated. Unlike the traditional fiber reinforced polymers (FRP such as carbon, glass, aramid, etc., the FRP tubes in this study were designed using large rupture strains FRP which are made of recycled materials such as plastic bottles; hence, large rupture strain (LRS FRP composites are environmentally friendly and can be used in the context of green construction. This study performed finite element (FE analysis using LS-DYNA software to conduct an extensive parametric study on CFFT. The effects of the FRP confinement ratio, the unconfined concrete compressive strength ( , column size, and column aspect ratio on the behavior of the CFFT under axial compressive loading were investigated during this study. A comparison between the behavior of the CFFTs with LRS-FRP and those with traditional FRP (carbon and glass with a high range of confinement ratios was conducted as well. A new hybrid FRP system combined with traditional and LRS-FRP is proposed. Generally, the CFFTs with LRS-FRP showed remarkable behavior under axial loading in strength and ultimate strain. Equations to estimate the concrete dilation parameter and dilation angle of the CFFTs with LRS-FRP tubes and hybrid FRP tubes are suggested.

  3. 复合树脂的不同固化方法对抗压强度影响%Effect of composite resins with different curing methods on compressive strength

    Institute of Scientific and Technical Information of China (English)

    徐晓; 崔智骁

    2001-01-01

    目的 探讨不同固化方法处理后对复合树脂抗压强度的影响。方法 采用光固化、光固化+光固化、光固化+热固化,3种不同固化方法处理3M和贺利氏复合树脂,在万能验试机上测试抗压强度。结果 2次处理的复合树脂抗压强度均比1次处理的复合树脂有较大提高,范围在51.8%~91.6%之间。不同的2次固化方法相比,统计学无显著差异。结论 复合树脂经2次固化方法处理,其抗压强度高于1次光固化方法的处理。%Objective To investigate the effect of composite resins dealedwith different curing methods on compressive strength. Methods The compressive strength change were determined by dealing with 3M composite resins and Herues composite resins by light cured, light cured + light cured and light cured + heat cured. Results The compressive strength with secondary cure was significantly higher than that of control groups (light cured only),a range from 51.8%~91.6% (P<0.05) , but there were no statistical difference between two secondary cure groups. Conclusion The compressive strength of secondary cured composite resins is higher than that of light cured only.

  4. 黄麻纤维增强混凝土的抗压和抗折性能研究%Compressive and flexural strength of jute fiber reinforced concrete

    Institute of Scientific and Technical Information of China (English)

    刘备; 季涛; 张丽哲

    2013-01-01

      在混凝土中添加黄麻纤维,以增强混凝土的抗压和抗折性能。通过测定纤维增强混凝土的抗压和抗折强度,并与素混凝土进行对比,进而研究黄麻纤维的长度和掺量对混凝土的增强作用。结果表明:黄麻纤维长度为30 mm,掺量为0.5~0.6 kg/m 3时,对混凝土的抗压及抗折强度增强作用最为显著。%Jute fibers were added into concrete to improve its compressive and flexural strength.In comparison with the pure concrete, the enhancement of jute fiber’s length and mixing amount in concrete was stud-ied by testing the compressive and flexural strength of fiber reinforced concrete.Test results showed that the compressive and flexural strength of the fiber reinforced concrete were significantly enhanced with 30 mm length jute fiber at the mixing amount of 0.5~0.6 kg/m 3 .

  5. 水饱和条件下的水泥土抗压试验意义%The Signiifcance of Cement Soil Compression Test under the Water Saturated Condition

    Institute of Scientific and Technical Information of China (English)

    胡桂宝; 周建民; 高乔明

    2015-01-01

    The test of pile body quality of cement soil mixing pile usually use the core and retention samples for unconfined compressive strength test. Unconfined compressive strength test of cement soil has been described in many codes,but not specific for the regulations of moisture content when testing pressure test. Moisture content is one of the most important factors affecting the compress strength of cement soil. In engineering practice,cement soil mixing piles were often under the ground water level which was usually destroyed in the saturated state. Therefore,it's very significant to study the water saturation state as a necessary condition for the compressive test of cement soil.%水泥土搅拌桩的桩身质量检测,通常采用取芯和留样进行无侧限抗压强度试验.水泥土无侧限抗压强度试验在很多规范中均有阐述,但对于试件试压时的含水率规定得并不够具体.含水率是影响水泥土抗压强度重要的因素之一,工程实践中,水泥土搅拌桩往往处于地下水位以下,其破坏时通常处于饱和状态,因此研究水饱和状态作为水泥土抗压试验的必要条件是很有意义的.

  6. C40特细砂混凝土和易性和抗压强度研究%Study on the workability and compressive strength of C40 superfine sand concrete

    Institute of Scientific and Technical Information of China (English)

    何锦云; 王陆陆

    2012-01-01

    The C40 super fine sand concrete is produced by using Handan local material and the influence of water - binder ratio, fly ash replacement rate, and sand ratio on the 28 d compressive strength and workability are studied in orthogonal experiment design. The results show that fly ash replacement is the most primary factor effecting on 28 d compressive strength and sand ratio is the most primary factor effecting on workability. Appropriate fly ash replacement can improve the 28 d compressive strength. With the increase of sand ratio, slumps decrease sharply and strength decreases slightly. It calls for using the 0.45 as water - binder ratio, 10% as fly ash replacement and 30% as sand ratio to make reasonable design of mix proportions, we can obtain the super fine concrete strength that its 28 d compressive strength reaches to 59. IMPa ,for 60mm of slump.%利用邯郸当地的原材料制备C40特细砂混凝土,采用正交设计方法,试验研究了水胶比、粉煤灰取代率、砂率对特细砂混凝土28 d抗压强度及和易性的影响.结果表明,粉煤灰取代率是影响混凝土28 d抗压强度的最主要因素,砂率是影响混凝土和易性的最主要因素;适当的粉煤灰取代率能提高混凝土28 d抗压强度;随着砂率的增加,塌落度大幅下降而强度略有降低;水胶比为0.45,粉煤灰取代率为10%,砂率为30%,通过添加1.2%的高效减水剂可配制出28d强度达59.1MPa、塌落度为60mm的混凝土.

  7. Unconfined deflagrative explosions without turbulence: experiments and model

    International Nuclear Information System (INIS)

    This paper reviews laboratory, balloon and open field experiments which have been performed to study the deflagration regime in free air. In a first part, are considered different models available to estimate deflagrative unconfined explosions effects, without turbulence. Then, a description is given of the known performed tests, which indicate the effective scale of various experiments, their operating conditions and the type of measurements carried out. Results are presented and discussed. The influence on the explosion force of different parameters (fuel concentration gradients, flammable mixture shape and size, ignition energy) is estimated. The overall conclusion of this survey is that flammable mixtures drifting over open field and ignited, will burn with low flame speed and consequently will generate very weak pressure effects

  8. Physical model simulations of seawater intrusion in unconfined aquifer

    Directory of Open Access Journals (Sweden)

    Tanapol Sriapai

    2012-12-01

    Full Text Available The objective of this study is to simulate the seawater intrusion into unconfined aquifer near shoreline and to assessthe effectiveness of its controlling methods by using scaled-down physical models. The intrusion controlled methods studiedhere include fresh water injection, saltwater extraction, and subsurface barrier. The results indicate that under natural dynamicequilibrium between the recharge of fresh water and the intrusion well agree with the Ghyben-Herzberg mathematical solution.Fresh water pumping from the aquifer notably move the fresh-salt water interface toward the pumping well, depending on thepumping rates and the head differences (h between the aquifer recharge and the salt water level. The fresh water injectionmethod is more favorable than the salt water extraction and subsurface barrier method. The fresh water injection rate of about10% of the usage rate can effectively push the interface toward the shoreline, and keeping the pumping well free of salinity.

  9. Study on the workability and compressive strength of C30 recycled coarse aggregate concrete%C30再生粗骨料混凝土和易性和抗压强度研究

    Institute of Scientific and Technical Information of China (English)

    何锦云; 毛明明

    2011-01-01

    The C30 recycled coarse aggregate concrete is produced by use of the concrete blocks from the dismantled masonry structure buildings and the influence of recycled coarse aggregate replacement percentages, water cement ratio, and sand ratio on the 28 d compressive strength and workability are studied in orthogonal experiment design. The results show that the recycled coarse aggregate replacement percentages is the most primary factor effecting on 28 d compressive strength and workability; and with the recycled coarse aggregate replacement percentages increased, strength and workability decreased; It calls for using the percentages of 60% as recycled coarse aggregate, 0. 5 as water cement ratio and 36% as sand ratio to make reasonable design of mix proportions, we can obtain the recycled coarse aggregate concrete that its 28d compressive strength reach to 46. 3 Mpa.%以砖混结构建筑拆卸下来的混凝土块为原材料制备C30再生粗骨料混凝土,利用正交设计方法,研究了再生粗骨料取代率、水灰比、砂率对再生混凝土28 d抗压强度及和易性的影响.结果表明再生粗骨料取代率是影响混凝土28 d抗压强度及和易性的最主要因素;随着再生粗骨料取代率的增加,强度与和易性均下降;使再生粗骨料取代率为60%,水灰比为0.5,砂率为36%,通过合理的配合比可以配制出28 d强度达到46.3 MPa的混凝土.

  10. Constructing a geomechanical model of the Woodford Shale, Cherokee Platform, Oklahoma, USA effects of confining stress and rock strength on fluid flow

    Science.gov (United States)

    Hair, Tyler J.

    A micro-indentation tool is used to estimate the strength of the Woodford Shale from whole core samples through the geometrical attributes (diameter and depth) of a 'dimple' produced by the tool on the rock's surface. The measured dimples are correlated graphically with the unconfined compressive strength and internal friction angle of the Woodford and integrated with contemporary stress data from earthquake focal mechanisms and mapped active faults. Right-lateral strike-slip motion on a deep, unnamed potential splay of the Wilzetta fault (Cherokee Platform, Lincoln County, Oklahoma) is representative of the contemporary stress state of the region. Vertical or near-vertical factures striking ˜ 030° from SHaz (˜ 077°) are the mechanical discontinuities most likely to be reactivated and allow fluids to flow along their surfaces. This reactivation will occur if the magnitude of pressure sources such as pore pressure or fluid pressure exceeds the reactivation pressure for that fracture surface.

  11. Experimental study of high volume fly ash pumping concrete compressive strength early%大掺量粉煤灰泵送混凝土早期抗压强度的试验研究

    Institute of Scientific and Technical Information of China (English)

    刘思海; 侍克斌; 吴福飞

    2014-01-01

    通过理论分析和试验,研究了大掺量粉煤灰对混凝土早期抗压强度及成本的影响。试验所选用的胶凝材料总量为375 kg,以0~55%的粉煤灰替代水泥,减水剂的掺量固定为1.0%,引气剂的掺量固定为1.2‱。通过坍落度及不同龄期抗压强度等对比分析粉煤灰掺量对混凝土和易性及早期强度的影响。结果表明,混凝土早期抗压强度及成本随着粉煤灰掺量的增大而逐渐减小,运用粉煤灰等质量代替水泥(P·O 42.5级水泥)可配制出28 d抗压强度为20 MPa以上,成本大大降低的大掺量粉煤灰混凝土。研究的结论为新疆地区粉煤灰的应用提供了有效途径,有助于制备高性能混凝土。%Through theoretical analysis and test,studied the effect of high volume fly ash on concrete compressive strength and cost. To-tal cementitious materials test for the selected 375 kg,with 0~55%fly ash instead of cement,the amount of superplasticizer was fixed at 1%,dosage of air entraining agent was fixed at 1.2‱.Through the slump and compressive strength of comparative analysis of the influence of fly ash on concrete workability and early strength. The results showed that ,the concrete compressive strength and cost decreased gradu-ally with the increase in the amount of fly ash,fly ash and other quality instead of using cement (42.5 ordinary portland cement)can be made by 28 d compressive strength was more than 20 MPa,a large amount of fly ash can reduce the cost of concrete. Provided an effective way for research conclusion was the application of fly ash in Xinjiang ,contributed to the preparation of high performance concrete.

  12. 再生粗骨料混凝土棱柱体抗压强度试验研究%Experimental Investigation of the Prism Compressive Strength of RAC

    Institute of Scientific and Technical Information of China (English)

    施养杭; 吴泽进; 彭冲; 王大富

    2011-01-01

    Because of the diversity of sources of recycled coarse aggregate, the prism compressive strength of RAC ( recycled aggregate concrete) will also vary. To study the differences of the prism compressive strength of RAC whose coarse aggregate is derived from different origins, four sources of recycled concrete, such as old house dismantlement, high-strength pile, municipal engineering and scientific research, are chosen in the study. The four kinds of waste concrete are broken into four kinds of RCA. Then, four kinds of replacement ratios are selected separately, and two mineral admixtures, such as fly ash and silicon epitaxial material, are added. By using the method of orthogonal test, four kinds of RAC whose coarse aggregate is derived from different origins are compounded. After 28-Day curing, the prism compressive strength is measured, compared and analyzed. Results show that recycled coarse aggregate replacement ratios and mineral admixtures are two important factors, while recycled coarse aggregate origin has lowest effect on the prism compressive strength of RAC.%因再生粗骨料来源的多途径,RAC(再生混凝土)棱柱体抗压强度将不同.为探索不同粗骨料来源RAC棱柱体抗压强度之间的差异性,选取最具典型代表性的旧房拆迁、高强桩基、市政工程、科学研究等四种不同粗骨料来源的废混凝土,经破碎加工成四种再生粗骨料,分别选取25%、50%、75%和100%四种取代率,同时掺入粉煤灰、硅微粉两种矿物掺合料,采用正交试验法,配置成四种不同粗骨料来源的RAC,测其棱柱体抗压强度,经比较与分析,得到再生粗骨料取代率和矿物掺合料是影响RAC棱柱体抗压强度的两个重要因素,再生粗骨料来源对RAC轴心抗压强度的影响不显著.

  13. 水泥粉煤灰搅拌饱和黄土强度影响因素试验研究%Experimental Research on the Factors Affecting the Strength of Saturated Loess Mixed with Cement and Fly Ash

    Institute of Scientific and Technical Information of China (English)

    安芃芃; 刘文晓; 杨有海

    2014-01-01

    Most of sections along Lanzhou to Zhongchuan Airport Railway Engineering fall into the saturated foundation with low bearing capacity, high compressibility and are reinforced by composite cement-soil mixed pile foundations. The strength performances of cement-fly-ash mixed saturated loess are tested and studied. Under such conditions with different cement and fly ash ( hereinafter referred to as the"two ash") admixture ratio, different cement strength grade, different age, the variation of unconfined compressive strength of cement soil is analyzed. The test results show that the unconfined compressive strength increases with the increasing of two ash admixture, age, the unconfined compressive strength of two ash admixture for cement soil 20% is 1. 42 times of two ash admixture 15%, and is 1. 9 times of the two ash admixture 12%;when the total admixture of two ash is unchanged, with fly ash in total of two ash ratio of 1/5 ,1/4 , 1/3 , cement soil strength decreases slightly; the unconfined compressive strength of cement soil increases obviously with the increasing of strength grade of cement, and the strength of cement soil increases dramatically with the increasing of the amount of cement and fly ash.%兰州至中川机场铁路工程沿线大多地段属于饱和黄土地基,承载力低,压缩性大,采取水泥土搅拌桩复合地基进行加固。对水泥粉煤灰搅拌饱和黄土强度特性进行试验研究。在不同的水泥和粉煤灰(以下简称“二灰”)掺和比、不同的龄期、不同的水泥强度等级下,分析水泥土无侧限抗压强度的变化规律。试验结果表明:水泥土无侧限抗压强度随二灰掺量、龄期的增加而增大,二灰掺量为20%的水泥土无侧限抗压强度是二灰掺量为15%的1.42倍,是二灰掺量12%的1.9倍;当二灰总掺入量不变,粉煤灰掺入量占二灰比例为1/5、1/4、1/3时,水泥土强度略有降低;水泥土无侧限抗压强度随水泥强度

  14. 复合处理法提高再生混凝土抗压强度的研究%THE STUDY ON IMPROVING COMPRESSIVE STRENGTH OF RECYCLED CONCRETE BY DUPLEX TREATMENT

    Institute of Scientific and Technical Information of China (English)

    方瑾; 郑双七

    2011-01-01

    The low compressive strength of recycled concrete led by itself defects of the recycled aggregate and working process, its application in engineering is limited. Comparing the difference between the compressive strength of recycled concrete and natural concrete, chemical treatment and active mixtures were used for recycled concrete to improve its surface modification, and the measures to improve strength of recycled concrete were also proposed.%再生骨料本身缺陷及加工过程复杂导致再生混凝土强度不高,工程推广受到限制。通过比较天然混凝土与再生混凝土抗压强度的区别,利用化学处理以及加入活性掺合料对再生混凝土进行表面改性,并提出提高再生混凝土强度的途径。

  15. The influence of post-local buckling mechanics on the stress variations, axial stiffness and ultimate failure strength of uniformly compressed thin-walled i-section struts

    International Nuclear Information System (INIS)

    It is well known that thin-walled compression members are subject to the effects of local buckling and that due to these local effects the compressive carrying capability of short strut members can be significantly reduced. Finite element simulation is employed in this paper to examine the post-buckled response of thin-walled sections giving due consideration to the influence of geometric imperfections and to elasto-plastic material behaviour. The findings from this work highlight the complete loading history of the compression struts from the onset of elastic local buckling through the nonlinear elastic and elasto-plastic post-buckling phases of behaviour to final collapse and unloading. A detailed account of the growth and redistribution of stresses as well as the influence of yielding and yield propagation throughout loading is given in the paper. The results from the finite element simulations are shown to compare well with independent simulations using the finite strip method of analysis.

  16. 改性贵州玄武岩残积土的抗压强度试验研究%Experimental Research on Compressive Strength of Modified Residual Soil of Basalt in Guizhou

    Institute of Scientific and Technical Information of China (English)

    张瑞敏; 柴寿喜; 魏厚振; 徐良

    2012-01-01

    In order to make residual soil of basalt in guizhou underlying for subgrade reasonably, according to the different content of lime, fly ash and cement on the mixed with a single, double, orthogonal. Measuring the compressive strength on considering not water and water to get a best proportion . Test results show that: (1) The compressive strength of modified residual soil of basalt increase gradually with the increase of the content of modified materials with a single experiment. The modification treatment of lime soil reach a maximum 8% when is watered. Fly ash reach a maximum 15% when is not watered, at the same time, the watering sample are all crumbling. (2) The compressive strength increase all with the increase of the content with the double experiment, and the compressive strength of lime: fly ash = 1 : 1 is higher than lime = fly ash = 1 : 2. (3) The best proportion is for 8% lime, 8% fly ash, 2% cement with the orthogonal experiment, and the lime is the biggest influence factors to the compressive strength of residual soil. Because the compression strength all has different increases with lime, fly ash, cement three kinds of materials processing basalt residual soil, so it is reference for subgrade with three kinds of materials mixed processing basalt residual soil.%为了使贵州玄武岩残积土合理用于路基,通过采用石灰、粉煤灰、水泥三种改性材料按不同含量对其进行单掺、双掺、正交试验研究,同时考虑未浸水与浸水两种状态,测其抗压强度,得出最佳配比.实验结果表明:①单掺试验,改性残积土的抗压强度随着改性材料含量的增加而逐渐增大.石灰处理的改性土浸水时在8%达到最大值,粉煤灰处理的在未浸水时在15%达到最大值,同时浸水的试样全部崩解.②双掺试验,抗压强度均是随着含量的增加而增大,且石灰:粉煤灰=1∶1的抗压强度比石灰:粉煤灰=1∶2的高.③正交掺试验,得出

  17. Workability Improvement Measures of Lightweight Aggregate Concrete and Its Influence on Compressive Strength%轻集料混凝土工作性能改善措施及其对强度影响

    Institute of Scientific and Technical Information of China (English)

    李晓斌

    2012-01-01

      采用陶粒预湿和掺增黏剂两种方法改善轻集料混凝土的工作性能,并研究其对混凝土抗压强度的影响.结果表明:陶粒预湿能够改善轻集料混凝土的工作性能,但会使混凝土强度有所降低;适量增黏剂HEMC 的掺入能够改善混凝土拌合物的工作性能,但掺量过多会使混凝土拌合物流动性下降和抗压强度明显降低.两种方法皆可用来改善轻集料混凝土拌合物的工作性能.采取陶粒预湿方法时,预湿时间宜为0.5 h,使用增黏剂 HEMC 时,其掺量宜控制在0.1%以内.%  Two methods of Pre-wetting ceramsite and spiking thickener were used to improve the workability of lightweight concrete, and its influence on compressive strength was also studied. The results indicate that Pre-wetting ceramsite can improve workability but reduce compressive strength of lightweight concrete. An appropriate amount of Hydroxyethyl Methylcellulose(HEMC) can improve the workability of lightweight concrete but the flowability and compressive strength will reduce when the amount of HEMC is too much. The two methods can both be used to improve the workability of lightweight concrete and the time of pre-wetting ceramsite should be 30 minutes and the amount of HEMC should be controlled less than 0.1%.

  18. The bearing capacity research for slender reinforced high strength concrete columns under eccentric compression loading%钢筋高强混凝土偏压中长柱承载力研究

    Institute of Scientific and Technical Information of China (English)

    杨荣华; 焦俊婷

    2015-01-01

    The bearing capacity was researched for slender reinforced high strength concrete ( RHC ) columns under eccentric compression loading .Based on the element model of beam -column when considering material nonlinearity and geometric nonlinearity , the computer program was given about nonlinearity analysis for RHC structures .Then main affecting factors were researched , such as slen-derness ratio , relative eccentricity , concrete strength , and longitudinal reinforcement ratio .The influ-encing order of these factors was relative eccentricity , slenderness ratio , longitudinal reinforcement ra-tio , and concrete strength , on the bearing capacity for slender RHC columns under eccentric compres-sion loading.As last, the design formula of the bearing capacity was given for slender RHC columns under eccentric compression loading by using the regression statistics method , this would offer design reference .%基于考虑材料非线性和几何非线性耦合梁柱单元模型,采用编制的钢筋高强混凝土结构非线性数值分析程序,分析钢筋高强混凝土偏压中长柱极限承载力主要影响因素有长细比、相对偏心距、混凝土强度、纵筋配筋率等。研究钢筋高强混凝土偏压中长柱极限承载力对各主要影响因素的敏感性,依次为相对偏心距、长细比、纵筋配筋率和混凝土强度。通过回归给出钢筋高强混凝土偏压中长柱极限承载力的计算公式,为实际工程应用提供计算参考。

  19. Modeling cross-hole slug tests in an unconfined aquifer

    Science.gov (United States)

    Malama, Bwalya; Kuhlman, Kristopher L.; Brauchler, Ralf; Bayer, Peter

    2016-09-01

    A modified version of a published slug test model for unconfined aquifers is applied to cross-hole slug test data collected in field tests conducted at the Widen site in Switzerland. The model accounts for water-table effects using the linearized kinematic condition. The model also accounts for inertial effects in source and observation wells. The primary objective of this work is to demonstrate applicability of this semi-analytical model to multi-well and multi-level pneumatic slug tests. The pneumatic perturbation was applied at discrete intervals in a source well and monitored at discrete vertical intervals in observation wells. The source and observation well pairs were separated by distances of up to 4 m. The analysis yielded vertical profiles of hydraulic conductivity, specific storage, and specific yield at observation well locations. The hydraulic parameter estimates are compared to results from prior pumping and single-well slug tests conducted at the site, as well as to estimates from particle size analyses of sediment collected from boreholes during well installation. The results are in general agreement with results from prior tests and are indicative of a sand and gravel aquifer. Sensitivity analysis show that model identification of specific yield is strongest at late-time. However, the usefulness of late-time data is limited due to the low signal-to-noise ratios.

  20. Modeling cross-hole slug tests in an unconfined aquifer

    CERN Document Server

    Malama, Bwalya; Brauchler, Ralf; Bayer, Peter

    2016-01-01

    A modified version of a published slug test model for unconfined aquifers is applied to cross-hole slug test data collected in field tests conducted at the Widen site in Switzerland. The model accounts for water-table effects using the linearised kinematic condition. The model also accounts for inertial effects in source and observation wells. The primary objective of this work is to demonstrate applicability of this semi-analytical model to multi-well and multi-level pneumatic slug tests. The pneumatic perturbation was applied at discrete intervals in a source well and monitored at discrete vertical intervals in observation wells. The source and observation well pairs were separated by distances of up to 4 m. The analysis yielded vertical profiles of hydraulic conductivity, specific storage, and specific yield at observation well locations. The hydraulic parameter estimates are compared to results from prior pumping and single-well slug tests conducted at the site, as well as to estimates from particle size ...

  1. Improvement of magnetic hysteresis loss, corrosion resistance and compressive strength through spark plasma sintering magnetocaloric LaFe11.65Si1.35/Cu core-shell powders

    Science.gov (United States)

    You, Caiyin; Wang, Shaopeng; Zhang, Jing; Yang, Nannan; Tian, Na

    2016-05-01

    LaFe11.65Si1.35/Cu core-shell powders were achieved by self-designed magnetron sputtering system, which presents a better solidification during spark plasma sintering in comparison to the naked LaFe11.65Si1.35 powders. Much higher compressive strength, lower corrosion current density and magnetic hysteresis losses are achieved for the sintered sample of LaFe11.65Si1.35/Cu core-shell powders without significant decrease of the magnetic entropy change. The compressive strength, corrosion current density and maximum magnetic hysteresis losses are 105.6 MPa/16.8 MPa, 1.08 × 10-3A/cm2/3.03 × 10-3 A/cm2 and 1.33 J/kg/2.71 J/kg, respectively for the sintered samples of core-shell structured/naked powders. The technique of fabricating the core-shell structured powders demonstrated here is also applicable for other types of functional powders.

  2. 再生火山岩骨料混凝土抗压强度及干缩性能试验%Experimental study on compressive strength and dry-shrinkage property of recycled volcanic rock coarse aggregate concrete

    Institute of Scientific and Technical Information of China (English)

    2015-01-01

    A recycled volcanic rock coarse aggregate concrete is developed,which the aggregate replacement rate is 100%. The compressive strength and dry-shrinkage performance of recycled volcanic rock aggregate concrete are studied. The results show that the compressive strength of recycled concrete after curing 28 days than that of normal concrete is reduced by about 13%,and the dry-shrinkage strain is about 1. 25 times of the reference concrete.%配置了骨料取代率为100%的再生火山岩粗骨料混凝土,并对其抗压强度和干缩性能进行试验研究,结果表明:再生火山岩混凝土28 d抗压强度比基准混凝土抗压强度降低约13%;干燥收缩应变约为基准混凝土的1.25倍。

  3. Synthesis of Zinc Oxide Nanoparticles and Their Effect on the Compressive Strength and Setting Time of Self-Compacted Concrete Paste as Cementitious Composites

    Directory of Open Access Journals (Sweden)

    Mohammad Reza Arefi

    2012-04-01

    Full Text Available In the present study, the mechanical properties of self-compacting concrete were investigated after the addition of different amounts of ZnO nanoparticles. The zinc oxide nanoparticles, with an average particle size of about 30 nm, were synthesized and their properties studied with the help of a scanning electron microscope (SEM and X-ray diffraction. The prepared nanoparticles were partially added to self-compacting concrete at different concentrations (0.05, 0.1, 0.2, 0.5 and 1.0%, and the mechanical (flexural and split tensile strength of the specimens measured after 7, 14, 21 and 28 days, respectively. The present results have shown that the ZnO nanoparticles were able to improve the flexural strength of self-compacting concrete. The increased ZnO content of more than 0.2% could increase the flexural strength, and the maximum flexural and split tensile strength was observed after the addition of 0.5% nanoparticles. Finally, ZnO nanoparticles could improve the pore structure of the self-compacted concrete and shift the distributed pores to harmless and less-harmful pores, while increasing mechanical strength.

  4. 含水量对冻结含盐粉土单轴抗压强度影响的试验研究%An Experimental Study of Influence of Water Content on Uniaxial Compression Strength of Frozen Salty Silt

    Institute of Scientific and Technical Information of China (English)

    陈锦; 李东庆; 邴慧; 邓友生

    2012-01-01

    In order to find the change law of uniaxial compression strength and failure strain of freezing salty silt under the influence of water content,natural saline soil was collected from the shore side of the Yellow River in Pingchuan district of Baiyin Municipality of Gansu Province as the sample.After leaching with distilled water,the soil was used to prepare specimens containing NaCl/Na2SO4 at salt content of 1.5% with different water contents.Analytically pure sodium sulfate and sodium chloride are used in the test.The test results indicate that when the water content was low,as the water content increasing,cementing power of ice increases,at the same time,ice endure more and more load with soil particles and crystals of salt,so the uniaxial compression strength of frozen salty soil will increase.When the water content increases to a certain degree,ice plays a leading role in the soil,the specimen presents the properties of ice,and the compression strength of ice is far less than that of mineral grains,so the uniaxial compression strength of frozen salty silt will decrease when the water content is over a given value.Failure strain has the similar change law with uniaxial compression strength changing with water content.%采用取自甘肃省白银市平川区黄河岸边的天然盐渍土,用蒸馏水洗去土中的盐分,配制成NaCl/Na2SO4含量为1.5%,含水量不同的试样,研究了冻结条件下含水量对冻结含盐粉土单轴抗压强度、破坏应变的影响.结果表明:当含水量较小时,随着含水量的增加,冰的胶结作用增强,并与土颗粒、盐晶体一起承受荷载,冻结含盐土的单轴抗压强度不断增大;当含水量超过某一值时,试样更多地呈现出冰的性质,而冰的强度远远小于矿物颗粒的强度,单轴抗压强度随含水量的增加而减小.随着含水量的变化,含盐土的破坏应变与单轴抗压强度有相似的变化规律.

  5. 胶凝砂砾石材料抗压强度影响因素研究%Study on the Influence Factors of Compressive Strength of CSG Material

    Institute of Scientific and Technical Information of China (English)

    柴启辉; 杨世锋; 孙明权

    2016-01-01

    As a new type of dam materials, the mechanical properties of CSG material are significantly affected by cement content, fly ash content, water binder ratio, sand ratio, aggregate gradation and age factors. In order to explore the influences of various factors on the compressive strength of the material, through a lot of experiments, this paper studied the variation laws of compressive strength and water cement ratio, sand ratio, cement content, fly ash content and other factors. When the engineering common sand ratio is in the range of 0.1⁃0.4, the optimal sand ratio is 0.2, corresponding to the optimal water binder ratio between 1.4 and 1.0. When the sand ratio is high, the upper bound of the optimal water binder ratio should be taken, and the lower value of the optimal water binder ratio is taken when the sand ratio is low. When the optimal sand ratio is 20%, the optimal water binder ratio is about 1.1. In every cubic meter of CSG materials, cement content increases by 10 kg, the 28 d compressive strength of the cube can increase by 15%⁃20%. With the increase of fly ash content per 10 kg, the compressive strength of cubic 28 d is increased, and the increase range is between 10% and 1%. The effects of specimen size and aggregate gradation on the compressive strength of the material are significant.%胶凝砂砾石材料作为一种新型的筑坝材料,力学特性受水泥用量、粉煤灰掺量、水胶比、砂率、骨料级配、龄期等因素的影响。通过大量不同配合比试验,研究胶凝砂砾石材料抗压强度随水胶比、砂率、水泥用量、粉煤灰掺量等因素变化的规律。砂率在工程常见范围0.1~0.4内时,胶凝砂砾石材料存在最优砂率,为0.2,对应最优水胶比为1.0~1.4;砂率高时最优水胶比取上限,反之取下限,最优砂率对应的最优水胶比为1.1左右。胶凝砂砾石材料中水泥用量每增加10 kg/m3,立方体试件28 d

  6. GFRP管钢骨高强混凝土偏压柱试验研究%EXPERIMENTAL RESEARCH ON GFRP COLUMNS FILLED WITH STEEL-REINFORCED HIGH-STRENGTH CONCRETE SUBJECTED TO ECCENTRIC COMPRESSION LOAD

    Institute of Scientific and Technical Information of China (English)

    王连广; 周乐

    2011-01-01

    Based on the eccentric compression experiments of 8 GFRP tubes filled with steel-reinforced high-strength concrete composite columns, the mechanism and failure modes of these columns were studied considering the variation of main effect Parameters, such as the GFRP tube fiber tangle angle, the GFRP tube thickness, the slenderness ratio and the eccentricity. The experimental results show that the bearing compressive capacity of composite columns obviously increases with the decrease of the fiber tangle angle and the thickness increase of GFRP tube, but decreases with the increase of the eccentricity and slenderness ratio. The theoretical calculating formula of GFRP columns filled with steel-reinforced high-strength concrete subjected to eccentric compression was proposed based on test study and theoretical analysis, and the calculated results agreed well with the experimental results.%通过8根GFRP管钢骨高强混凝土组合柱偏心受压试验,研究了GFRP管纤维缠绕角度、管壁厚度、长细比及偏心距等参数对组合柱受力性能的影响.试验结果表明:组合柱承载力随着GFRP管壁纤维缠绕角度的减小、管壁厚度的增加而提高,随着长细比增大、偏心距增加而降低.根据试验研究与理论分析,建立GFRP管钢骨高强混凝土偏心受压组合柱承载力计算公式,理论计算结果与试验结果吻合良好.

  7. 含分层损伤缝合复合材料层板的剩余压缩强度%Prediction of Residual Compressive Strength of Stitched Composite Laminates with a Delamination

    Institute of Scientific and Technical Information of China (English)

    孙浩; 许希武; 郭树祥

    2012-01-01

    Based on a progressive damage method, the mechanical behaviors of stitched composite laminates containing initial delamination were investigated. A finite element (FE) model was established to predict the residual compressive strength through ABAQUS. Laminate buckling and delamination propagation were considered during the analytical process. The failures of laminates , interlaminar and stitching were simulated by UMAT subroutine embedded truss elements were used to provide the bridge-forces of stitching. Hashin criterion and stiffness reduction method were introduced to predict fiber failure and matrix failure. The progressive damage process was investigated and the damage mechanisms were analyzed in detail. Effects of different stitching parameters on residual compressive strength were discussed. The predicted failure modes and strength have excellent agreement with experimental results. It shows that stitching increases laminate buckling load-capacity, restrains delamination propagation and increases the residual compressive strength.%基于渐进损伤方法,研究了含单脱层缝合复合材料层板在压缩载荷下的剩余强度。通过商用软件ABAQUS建立了含单脱层缝合复合材料层板剩余压缩强度计算模型,考虑了子层屈曲和分层扩展对剩余强度的影响。通过UMAT子程序实现了层板失效、层间失效和缝线失效的模拟。通过嵌入式杆单元结构模拟了缝线桥联作用及失效。采用Hashin准则及刚度折减法对纤维拉压、基体拉压失效进行了模拟。通过渐进损伤分析,揭示了缝合情况下含单脱层复合材料层板的失效机理,讨论了缝合参数对剩余压缩强度的影响。所预测的破坏模式和剩余强度结果与实验能较好地吻合。分析表明缝合可以明显提高含分层损伤复合材料层板的子层屈曲载荷,抑制分层扩展,并提高层板的剩余压缩强度。

  8. Chemical Stabilisation of Sand Part IX: Orthophthalate type Unsaturated Polyester Resin for Inducing Fast setting Behaviour and High Strength

    Directory of Open Access Journals (Sweden)

    B. P. Gupta

    1994-01-01

    Full Text Available Polymer concrete composites have been made from orthophthalate-type unsaturated polyester resin, methyl ethyl ketone peroxide as initiator, cobalt naphthenate as accelerator and desert sand as filler. Composites preferred using resin (10-25 per cent, initiator (4 per cent and accelerator (2 per cent with representative desert sand samples of different particle sizes (0.2-0.02 mm, 2-0.2 mm and 4-2 mm as filler recorded unconfined compression strength ranging from 4 to 442 kg/cm/sup 2/ after curing at 50 degree centigrade in an oven for 0.5-24 h. Using coarse and fine sand samples with 10 and 15 per cent resin systems the maximum strength of 391 and 326 kg/cm/sup 2/ respectively was attained after 2 h of curing at 50 degree centigrade. The fast setting resin system with strength in this range is quite adequate for the construction of chemically stabilised surfaces, which withstand trafficability of vehicles, operation of helicopters and aircraft's requiring a maximum strength up to 275 kg/cm/sup 2/. These composites may prove useful for rapid repair of roads, helipads and runways damaged during operational activities. A mathematical model has been developed for predicting resin percentage needed for obtaining composite material of requisite strength. The observed and model predicted values have been found to show close agreement.

  9. Dispersal and air entrainment in unconfined dilute pyroclastic density currents

    Science.gov (United States)

    Andrews, Benjamin J.

    2014-09-01

    Unconfined scaled laboratory experiments show that 3D structures control the behavior of dilute pyroclastic density currents (PDCs) during and after liftoff. Experiments comprise heated and ambient temperature 20 μm talc powder turbulently suspended in air to form density currents within an unobstructed 8.5 × 6 × 2.6-m chamber. Comparisons of Richardson, thermal Richardson, Froude, Stokes, and settling numbers and buoyant thermal to kinetic energy densities show good agreement between experimental currents and dilute PDCs. The experimental Reynolds numbers are lower than those of PDCs, but the experiments are fully turbulent; thus, the large-scale dynamics are similar between the two systems. High-frequency, simultaneous observation in three orthogonal planes shows that the currents behave very differently than previous 2D (i.e., confined) currents. Specifically, whereas ambient temperature currents show radial dispersal patterns, buoyancy reversal, and liftoff of heated currents focuses dispersal along narrow axes beneath the rising plumes. The aspect ratios, defined as the current length divided by a characteristic width, are typically 2.5-3.5 in heated currents and 1.5-2.5 in ambient temperature currents, reflecting differences in dispersal between the two types of currents. Mechanisms of air entrainment differ greatly between the two currents: entrainment occurs primarily behind the heads and through the upper margins of ambient temperature currents, but heated currents entrain air through their lateral margins. That lateral entrainment is much more efficient than the vertical entrainment, >0.5 compared to ˜0.1, where entrainment is defined as the ratio of cross-stream to streamwise velocity. These experiments suggest that generation of coignimbrite plumes should focus PDCs along narrow transport axes, resulting in elongate rather than radial deposits.

  10. Resistência à compressão do solo-cimento com substituição parcial do cimento Portland por resíduo cerâmico moído Compressive strength of soil-cement with partial replacement of the Portland cement by crushed ceramic waste

    Directory of Open Access Journals (Sweden)

    Rivanildo Dallacort

    2002-12-01

    Full Text Available Neste trabalho, apresenta-se o estudo experimental da resistência à compressão do solo-cimento, com substituição parcial do cimento Portland por resíduo cerâmico moído. Para tanto, foram ensaiados 81 espécimenes cilíndricos desse material à compressão, em que parte do cimento foi substituída por material cerâmico moído. Realizou-se uma programação fatorial, na qual três variáveis foram selecionadas para estudo: o teor de material ligante (cimento + resíduo cerâmico, a umidade do solo e o teor de resíduo cerâmico adicionado. É apresentado um estudo estatístico através de análise de variância da massa específica do material e da resistência a compressão. Tal estudo permitiu concluir-se que substituições de 25 e 57% do teor de cimento por material cerâmico podem produzir blocos de solo-cimento com resistências superiores a 2 MPa, com teor de material ligante de 6 e 8%, respectivamente.In this paper, an experimental study of the compressive strength of soil-cement with partial replacement of the Portland cement by crushed ceramic waste is presented and discussed. For this, eighty-one cylindrical specimens of soil-cement were tested, where part of cement percentage was replaced by crushed ceramic waste. The experiment was conducted in factorial design and three variables were selected and studied: the binding material content (cement + ceramic waste, soil moisture content and the ratio of ceramic waste. A statistical study using variance analysis of the specific mass and compressive strength of the material is presented. This study concluded that replacement ratios of 25 and 57% of the Portland cement by crushed ceramic material can be used to fabricate soil-cement bricks with strength higher than 2 MPa, for a binding material content of 6 and 8% respectively.

  11. 低强度砂浆灌孔砌块砌体抗压性能试验研究%EXPERIMENTAL RESEARCH ON COMPRESSIVE BEHAVIORS OF GROUTED BLOCK MASONRY WITH LOW-STRENGTH MORTAR

    Institute of Scientific and Technical Information of China (English)

    黄靓; 王辉; 陈胜云

    2012-01-01

    In order to study the effect of mortar strength on compressive behaviors of grouted concrete masonry,nine specimens using lime mortar were analyzed.According to failure pattern,cracking load,ultimate capacity and deformation capacity,a formula was provided to calculate the compressive capacity of grouted concrete masonry when the mortar strength is very low.The ratio of cracking load to ultimate load is very small,which affects the durability of masonry building.Therefore,this paper states that the mortar strength should be higher than a critical value when designing and constructing grouted concrete masonry.%为了研究低强度砂浆对灌孔砌块砌体抗压性能的影响,该文通过9个采用石灰砂浆砌筑的灌孔砌块砌体的抗压试验,对其抗压破坏形态、开裂荷载、极限荷载及变形能力进行了分析,提出了适用于砂浆强度很低的灌孔砌块砌体的抗压强度计算公式。分析表明:低强度砂浆砌块砌体的初裂荷载与极限荷载之比较小,而开裂荷载过低将会对砌体房屋的耐久性产生不利影响,因此,该文认为在进行灌孔砌块砌体的设计和施工时,砂浆的强度应得到保证,不能过低。

  12. 不同基底材料烤瓷冠抗压缩破坏力的对比研究%Comparative study on the compressive strength of porcelain crown with different base materials

    Institute of Scientific and Technical Information of China (English)

    吴洁; 陈志宇; 仇亚非; 李宁; 郭长军

    2015-01-01

    Objective:To compare the compressive strength of porcelain crown with Co-Cr,CAD/CAMpure titanium and CAD/CAM zirconia respectively.Methods:Metal models of simulating crown core of the ideal premolar were manufactured,digital data of the met-al model were obtained by CAD/CAMsystem,the basement crowns of Co-Cr,CAD/CAMpure titanium and CAD/CAMzirconia were respectively made(n =5),size of each crown was kept the same and the spcimens were set as group A,B and C respectively.Then masking porcelain and body porcelain were fired on basement crowns according to the instructions.The thickness of the porcelain was kept the same.All of the porcelain crowns were located on the Instron testing machine,the compression strength force values were measured.Data were statistically analysed by SPSS 1 3.0 software.The bonding surface of basement material and porcelain was observed by SEMafter compressive failure.Results:The compressive strength(N)of group A,B and C was 2 990 ±1 88,2 305 ±1 57,2 1 50 ± 1 31 ,A vs B or C,P 0.05.Conclusion:All the 3 base materials with porcelain crown satisfy the clinical require-ments.The compressive strength of Co-Cr porcelain crown is stronger than that of CAD/CAMpure titanium porcelain crown and CAD/CAMzirconia porcelain crown.%目的:比较钴铬烤瓷冠、CAD/CAM纯钛切削烤瓷冠和 CAD/CAM氧化锆全瓷冠的抗压缩破坏力。方法:用金属代型模拟前磨牙预备体,扫描代型获取数字化模型数据,通过计算机辅助设计制作系统,制作尺寸一致的钴铬基底冠、CAD/CAM纯钛切削基底冠和 CAD/CAM氧化锆基底冠试件各5个,分别设定为 A、B、C 3组,各组基底冠分别按产品说明涂塑烧结遮色瓷与体瓷,控制各试件厚度一致。在万能材料测试机上检测试件抗压缩破坏力值。采用 SPSS 13.0统计分析软件对数据进行统计分析,用扫描电镜观察基底材料与遮色瓷结合界面微观结构。结果:A、B、C 3组试件

  13. Relationship between small-strain shear modulus and growth of strength for stabilized silt%固化粉土小应变剪切模量与强度增长相关性研究

    Institute of Scientific and Technical Information of China (English)

    张涛; 刘松玉; 蔡国军

    2015-01-01

    小应变剪切模量和无侧限抗压强度是表征固化土刚度和强度特性的两个重要参数.简要介绍了弯曲元测试技术的原理及其在试验中存在的问题,采用压电陶瓷弯曲元测试技术对水泥和木质素固化剂固化粉土试样在不同养护龄期下的小应变剪切模量进行了测试,同时对相应龄期下试样进行了常规无侧限抗压强度试验,通过引入归一化参数G28和 UCS28对不同固化土的小应变剪切模量和无侧限抗压强度之间的相关关系进行分析,提出了固化土刚度与强度的相关性模型,可为地基处理中固化土的无损测试与加固效果评价提供新的方法.结果表明,水泥、木质素固化粉土的小应变剪切模量随养护龄期增加而增加,养护龄期28 d内增长显著,28 d后增长趋于平稳;相同类型固化土不论固化剂掺量多少,其小应变剪切模量随养护时间的发展在本质上是相同的;固化土归一化无侧限抗压强度表现出与小应变剪切模量相似的发展趋势;提出的固化土归一化模型可作为一种土体强度无损检测的新方法.%The small-strain shear modulus and unconfined compressive strength are two important parameters to characterize the stiffness and strength of stabilized soils. The fundamental and the main problems existing in the experiment of bender element technique are briefly reviewed. The small-strain shear modulus of cement and lignin stabilized silt are tested under different curing time by piezoelectric bender element technique. The conventional unconfined compressive strength test is also carried out on stabilized samples under different curing time. The relationships between the small-strain shear modulus and unconfined compressive strength of different stabilized soils are analyzed by introducing the normalized parametersG28 and UCS28. A stabilization model for the stiffness and strength of stabilized soils is proposed to provide a new method for

  14. Performance Appraisal of Controlled Low-strength Material Using Sewage Sludge and Refuse Incineration Bottom Ash

    Institute of Scientific and Technical Information of China (English)

    甄广印; 周海燕; 赵天涛; 赵由才

    2012-01-01

    This research evaluated the use of sewage sludge and refuse incineration bottom ash to replace calcium sulfoaluminate cement (CSA) in making controlled low-strength material (CLSM). Various properties of CLSM mixtures were characterized in terms of unconfined compressive strength, microstructure and leachability. It was found that the strength of tested CLSM mixtures ranged from 3.6 to 9.0 MPa, over the upper excavatable limit of 2.1 MPa. The micro-structural analysis revealed that sewage sludge and bottom ash were crystallochemically in- corporated within CLSM system_s by forming the needle-like ettringite (C3A'3CS'_H32) with exiguous tu.bers via the typical Pozzolanic Reaction, leading to a dense and low-porosity microst;'ucture. Furthermore,-the toxicity characteristic leaching procedure evidenced that the cumulative leachable metals in the leachate were much below the regulatory thresholds. The potential for us!ng sewage sludge and bottom ash!n CLSM makin.g was thus confirmed.

  15. 胶凝材料对胶凝砂砾石材料抗压强度的影响%Study on the Effect of the Amount of Cementitious Materials on the Compressive Strength of CSG Material

    Institute of Scientific and Technical Information of China (English)

    杨世锋; 柴启辉; 孙明权

    2016-01-01

    针对胶凝砂砾石材料水泥用量少、粉煤灰掺量多的特点,研究低水泥用量和粉煤灰掺量对材料前期、后期强度的影响规律。通过对不同水泥用量、粉煤灰掺量和不同龄期的胶凝砂砾石材料进行试验研究,得到不同胶凝材料用量下的强度区间,以及粉煤灰的最优掺量和粉煤灰掺量对材料后期强度的影响规律等。水泥用量每增加10 kg/m3,材料抗压强度可提高15%~20%。粉煤灰掺量占胶凝材料总量(水泥+粉煤灰)的50%为最优掺量,此时强度出现峰值;掺量占胶凝材料总量(水泥+粉煤灰)的40%左右为经济掺量,即掺入粉煤灰提高材料强度的效率最高。在胶凝砂砾石材料中,粉煤灰掺量的增加对其抗压强度有提高作用,其中对前期(28 d)强度影响较小;粉煤灰用量每增加10 kg/m3,后期(90 d)强度提高幅度为5%~18%,其影响随着砂率的增大而减小。%In view of the characteristics of CSG material of low cement content and much fly ash content, it studied the effect of low cement content and fly ash content on the early stage of the material and the influence of the late strength was very important. Through a large number of experimental studies on the different amount of cement, fly ash content and different age period of CSG materials, the strength interval of materials with different cementitious materials, the fly ash of the optimal mixing and the fly ash amount of materials later strength influences were obtained. The compressive strength of the material can be increased by 20%⁃15% with the increase of the amount of cement per 10 kg. When the amount of fly ash is 50% of the total amount of cementitious materials ( cement+fly ash) , it is the"optimal dosage", at this time the intensity of peak. When the amount of fly ash is 40% of the total amount of cementitious materials ( cement+fly ash ) , it is the"economical dosage

  16. 基于正交试验的EPS混合土抗压强度的研究%Compressive Strength of Heterogeneous Soil Mixed with Expanded Polystyrene Based on Orthogonal Experiments

    Institute of Scientific and Technical Information of China (English)

    眭小龙; 何明胜; 付小建

    2011-01-01

    保温轻质混凝土空心砌块--生土组合墙体结构是由EPS混合土为内芯、轻质混凝土砌块为外模组成的一种新型结构形式.本文以该结构形式的内芯材料EPS混合土为研究对象,将EPS、水泥、水作为主要参数,对EPS混合土进行了抗压强度试验研究.通过正交试验设计了16组试件,分析了各因素对混合土抗压强度的影响规律,得出EPS含量对EPS混合土抗压强度的影响最大,水泥含量和用水量次之;给出了各因素与EPS混合土抗压强度之间的关系曲线,得出最佳配合比,最佳水平为:水泥用量30%,EPS用量1%,用水量30%.通过对最优工程条件下真值变动半径的计算,得到了最优配合比的真值变动范围在1.108~2.778之间.%The composite masonry of thermal-insulating lightweight concrete hollow block (is a new type of structure with expanded polystyrenesoil (EPS)as its inner core and the lightweight concrete block as its external model. This paper takes the inner core material-EPS-soil(heterogeneous soil mixed with expanded polystyrene) of this version as its research subject, with EPS,cement and water as its main parameters. Experiment for compressive strength of EPS-soil was carried out. 16 groups of samples are designed through the orthogonal test, the influence factors law to compressive strength of EPSsoil has been analyzed. EPS content is the most significant influencing factor in the compressive strength of EPS-soil, with cement content as the less and water content the least influencing factors the influence factors' relational curves to compressive strength of EPS-soil have been given,and the optimum mix ratio is advanced, that is: cement content 30%, EPS content 1%, water content 30%.Through calculating the truth-value variable radius under optimal project condition, the mobility scale of the optimum mix radio 's truth-value was gained between 1.108~2.778.

  17. Effect of Autoclaved Schedule for Compressive Strength of Hematite Tailing Bricks%蒸压制度对赤铁矿尾矿蒸压砖强度的影响

    Institute of Scientific and Technical Information of China (English)

    赵云良; 张一敏; 陈铁军

    2012-01-01

    Effect of autoclaved schedule for compressive strength of hematite tailing-lime-yellow sand system was studied. The suitable autoclaved schedule was that rise time, autoclave pressure, autoclave time, and decompression time were 2.1 h, 1. 2 MPa, 6 h and 3. 5 h, respectively, when the quality ratio of hematite tailings: lime: yellow sands was equal to 70:15:15 and forming pressure was 20 MPa. The mechanism of Effect of autoclaved schedule for compressive strength was discussed by XRD and DSC. The results show that in the hydration reaction process, hydrogarnet is firstly generated, and then CSH( 1) and high-strength tobermorite under the condition of 1. 2 MPa autoclaved pressure. With autoclave continuing, tobermorite is gradated into relative low-strength xonotlite.%研究了蒸压制度对赤铁矿尾矿-石灰-黄沙体系蒸压砖抗压强度的影响,确定了原料中尾矿、石灰、黄沙的质量比为70∶15∶15,成型压力为20 MPa的砖坯的适宜蒸压制度为∶升压时间2.1h,蒸汽压力1.2 MPa,恒压时间6h,降压时间3.5h.利用XRD 、DSC对蒸压砖抗压强度形成机理进行了探讨,结果表明,赤铁矿尾矿-石灰-黄沙体系在1.2MPa蒸汽压力下首先生成了水石榴石,而后生成CSH(Ⅰ)凝胶和高强度的托勃莫来石,随着蒸压时间的延长,托勃莫来石逐渐转化成强度相对较低的硬硅钙石.

  18. Modeling particulate self-healing materials and application to uni-axial compression

    NARCIS (Netherlands)

    Herbst, O.; Luding, S.

    2008-01-01

    Using an advanced history dependent contact model for DEM simulations, including elasto-plasticity, viscosity, adhesion, and friction, pressure-sintered tablets are formed from primary particles. These tablets are subjected to unconfined uni-axial compression until and beyond failure. For fast and s

  19. The Grilled Effect of Particle's Distribution of Calsine Coke's at 900oC Temperature upon the Electric Resistivity, Hardness and CompressiveStrength Analysis

    International Nuclear Information System (INIS)

    Investigation of Calsine Coke's particle's distribution by grilledtreatment at 900 oC temperature upon the electric resistivity, hardness andcompressive strength analysis had been done. The Calsine Coke's were crushedand sieved to get a particle size about 63; 90; 106 μm, then mixed thevariety size particle with 33 % tar pitch 125 μm, be heated, shaped andpressed to be pellet. The pellets were grilled at 900 oC temperature during30 minutes and then these were analyzed. The whole analysis using 2-b mixedwas the best, particle ratio were 63:106 = 1:2 and pointed the electricresistivity 2.63 Ωm, the hardness 5.9 kg/mm2 and the compressivestrength 1600 N. (author)

  20. Characteristics of structural loess strength and preliminary framework for joint strength formula

    OpenAIRE

    Rong-jian LI; Jun-ding LIU; Yan, Rui; Zheng, Wen; Sheng-jun SHAO

    2014-01-01

    The strength of structural loess consists of the shear strength and tensile strength. In this study, the stress path, the failure envelope of principal stress ( line), and the strength failure envelope of structurally intact loess and remolded loess were analyzed through three kinds of tests: the tensile strength test, the uniaxial compressive strength test, and the conventional triaxial shear strength test. Then, in order to describe the tensile strength and shear strength of structural loes...

  1. The Influence of Recycled Sand on Construction Workability and Compressive Strength of Mortar%再生砂对砂浆的施工和易性及抗压强度的影响

    Institute of Scientific and Technical Information of China (English)

    段邦政; 鄢朝勇; 朱攀; 肖枭; 孙少君

    2011-01-01

    Construction waste in HuBei Xiangyang region can be recycled by screening the crushed sand, part or all of the recycled sand to replace natural sand in constuction mortar,with fly ash extract as admixture to produce recycled aggregate mortar. It is researched on the influence of recycled sand on mortar workability and compressive strength. Under the same circumstances of mortar liquidity, with the recycled sand content increased,mortar's retention tends to increase and water’s dosage tends to increase too. When the recycled sand replace 40% of the recycled aggregate mortar, the mortar gets the good aggregate gradation and strength.%将湖北襄阳地区的建筑垃圾粉碎筛分得到再生砂,以再生砂部分或全部取代建筑砂浆中的天然砂,用粉煤灰作为掺加料,制作再生砂浆,研究再生砂对砂浆和易性及抗压强度的影响.在砂浆流动性基本相同的情况下,随再生砂掺量增加,砂浆的用水量明显增大、保水性趋于提高.再生砂浆在再生砂取代量为40%时获得良好的骨料级配,强度提高.

  2. Time-effect Analysis of Concrete Compressive Strength Based on the B3 Model under Sulphate Attack%硫酸盐侵蚀环境下基于B3模型的混凝土抗压强度时效分析

    Institute of Scientific and Technical Information of China (English)

    贺志远; 滕海文; 赵卓; 李晖

    2013-01-01

    基于B3模型,建立了持续荷载下混凝土抗压强度的时效模型.通过考虑持续荷载和硫酸盐共同作用对混凝土截面有效应力的影响,建立了持续荷载和硫酸盐共同作用下混凝土抗压强度的时效模型.经分析,持续荷载和环境因素是影响混凝土抗压强度时效水平主要的因素,而混凝土强度等级对强度时效水平的影响较小.%Based on the B3 model of concrete creep and shrinkage,this paper established the time-effect model of concrete compressive strength under sustained load.By considering effects of sustained load and sulphate attack on the section effective stress,the paper further developed the time-effect model of concrete compressive strength under sustained load and sulphate attack.Based on analysis,the sustained load and environment are the main factors that affect the time-variation of concrete compressive strength; and the strength grade of concrete has little influence on the time-variation of concrete compressive strength.

  3. Ultimate Bearing Strength of Post-tensioned Local Anchorage Zones in Lightweight Concrete

    OpenAIRE

    Axson, Daniel Peter

    2008-01-01

    Currently, NCHRP Report 356 has published an equation to estimate the ultimate strength of the local zone in normal weight concrete. The local zone is the area of concrete directly ahead of the bearing plate. The equation can be broken into two distinct parts: unconfined bearing strength of concrete enhanced by the A/Ab ratio and the enhancement of strength due to the presence of confining. Research has shown that the strength enhancement of the A/Ab ratio and confining reinfor...

  4. 干湿循环下复合固废填料配比对强度的影响%Effect of Mixture Proportions on Compressive Strength of Composite Geomaterial Subjected to Drying-Wetting Cycles

    Institute of Scientific and Technical Information of China (English)

    何忠意; 邓安; 周亚东; 王海波

    2011-01-01

    Nine series of samples of composite lightweight geomaterials were produced by mixing waste foundry sand, fly ash, expanded polystyrene (EPS) bead, water and Portland cement in proportions, which were exposed to designated drying-wetting(D-W) cycles. Uniaxial compression tests were carried out on the samples to investigate the effect of mix proportions onto the structural integrity of the geomate-rial. Results indicate that the geomaterial offers promise as soil-cement mixtures after up to 8 D-W cycles. Along with increase of cement content, the compressive strength of the geomaterial gains in initial 2-3 D-W actions. To add fly ash properly enhances the strength gain and D-W resistance of the geomaterial. Although EPS addition prompts the light weight of the geomaterial, its addition, if above l%(by mass) , will lead to strength loss. Optimal mix proportions for the geomaterial are suggested.%通过对不同配比的9组复合固废轻质填料(简称轻质填料)试样在不同干湿循环次数下的单轴抗压强度试验,分析了干湿循环下各组分掺入比对轻质填料抗压强度的影响.结果表明:轻质填料经历8次干湿循环后仍有较好的力学性能,达到或超过水泥土的强度要求.随着水泥掺量的增加,轻质填料在早期干湿循环过程中强度提高,有助于后期抗干湿循环.适量掺入粉煤灰,有利于提高轻质填料的强度及抗干湿循环能力.聚苯乙烯颗粒超过1%(质量分数),会衰减轻质填料的强度和降低其抗干湿破坏的能力.提出了轻质填料的配比范围.

  5. 二氧化碳腐蚀对油井水泥石抗压强度的影响%EFFECT OF CARBON DIOXIDE CORROSION ON COMPRESSIVE STRENGTH OF OILWELL CEMENT

    Institute of Scientific and Technical Information of China (English)

    张景富; 王宇; 徐明; 赵强

    2009-01-01

    利用扫描电子显微镜、强度测试仪检测了不同条件下二氧化碳腐蚀油井水泥的产物、微观结构及抗压强度,研究了二氧化碳腐蚀油井水泥的机理及腐蚀对水泥强度的影响,分析和评价出了适合于大庆油田不同温度深井条件的水泥浆体系.结果表明:二氧化碳对油井水泥的腐蚀作用本质在于二氧化碳能够与水泥的水化产物发生化学作用,生成了各种不同晶体结构的CaCO3产物,使原有的水泥石微观结构遭到破坏,导致腐蚀后水泥石的强度下降;温度和二氧化碳分压增高;改善水泥石抗腐蚀能力应以有效改善水泥水化产物及微观结构为基础,添加抗腐蚀填充材料能有效改善水泥浆体系的抗腐蚀能力.%The composition of the corrosion products, the microstructures and the compressive strength of corroded cement samples were examined by scanning electron microscopy and strength testing under different corrosion conditions by carbon dioxide (CO2). The corrosion mechanism of oilwell cement by CO2 and the effects of CO2 corrosion on the compressive strength of oilwell cement were investigated. Oiiwell cement slurries suitable for the deep wells at different temperatures in the Daqing oil field were analyzed. The results show that the cement corrosion by CO2 occurs by the destruction of the microstructure formed by the original hydration products of oiiweU cement. This destruction is affected by CaCO3, with different crystal structrue, which is produced by the chemical reaction between CO2 and the original hydration products. For the cement corrosion by CO2, the compressive strength decreased with increaseing the curing temperature and the CO2 differential pressure. The development of anti-corrosive cement systems should be based on the effective improvement of the hydration products and the microstructure of cement stone. A corrosion resisting additive named DCR used can effectively improve the corrosion

  6. Pumping from unconfined aquifers of limited saturated thickness with reference to wellpoints and horizontal wells

    Science.gov (United States)

    Rushton, K. R.; Brassington, F. C.

    2016-03-01

    Groundwater in unconfined aquifers of limited saturated thickness can be a valuable resource but frequently it is not developed because conventional boreholes are unsuitable. However, successful exploitation of shallow unconfined aquifers has been achieved using either a line of wellpoints or horizontal wells extending for more than 100 m. The flow processes by which wellpoints and horizontal wells collect water from unconfined aquifers are explored by developing conceptual and computational models. Several representative examples are considered and it is found that similar discharges occur if the wellpoints are closely spaced. The sensitivity of the yield to physical dimensions of the wells and aquifers is explored; the impact of alternative aquifer parameters is also examined. Results from these computational models are used to identify the causes of air entry into wellpoint systems; the prevention of air entry into horizontal wells is also considered. This evaluation demonstrates that wellpoint systems and horizontal wells can efficiently abstract water from unconfined aquifers of limited saturated thickness provided that precautions are taken to prevent air entry.

  7. Microfracturing of coal due to interaction with CO 2 under unconfined conditions

    NARCIS (Netherlands)

    Hol, S.; Spiers, C.J.; Peach, C.J.

    2012-01-01

    Laboratory experiments conducted in the past century have shown that exposure of coal to CO2 under unconfined, hydrostatic conditions leads to reversible adsorption and swelling. However, several authors also report irreversible changes in sorption capacity, sample volume, equilibration time and bri

  8. 钢筋混凝土构件基于修正压力场理论的受剪承载力计算%SHEAR STRENGTH OF REINFORCED CONCRETE MEMBERS BASED ON MODIFIED COMPRESSION FIELD THEORY

    Institute of Scientific and Technical Information of China (English)

    魏巍巍; 贡金鑫

    2011-01-01

    Based on the modified compression field theory, this paper develops an equation to calculate the shear capacity considering the shear contribution of concrete in compression, the shear stress transmitted across crack interface, and the contribution of stirrups based on shear failure mechanism of reinforced concrete members. The proposed equation is verified through a comparison with the experimental results from different sources (275 in total). It was found that consistency between shear strength calculated using the derived expressions and test data were well. So it is suitable for shear analysis and design of reinforced concrete beams.%在经典修正压力场理论的基础上做了进一步的研究,根据钢筋混凝土受弯构件的剪切破坏机理,考虑上部受压区混凝土和下部受拉区骨料咬合力及箍筋共同提供受剪承载力,推导出截面的受剪承载力表达式.与所收集的国内外有腹筋梁的275个试验结果的比较表明,采用该文提出的受剪承载力表达式计算的受剪承载力与试验结果的变异性较小,可用于钢筋混凝土梁的抗剪分析和设计.

  9. Influence of Axial Compression Loads on the Strength of Helical Buckling Tubing String%轴向压力对螺旋屈曲管柱强度安全性影响分析

    Institute of Scientific and Technical Information of China (English)

    钟大虎; 夏辉; 窦益华; 曹银萍

    2014-01-01

    为校核螺旋屈曲管柱的强度安全性,基于弹簧理论与第四强度理论,推导出螺旋屈曲状态下管柱内、外侧相当应力的计算公式,并以油田常用规格油套管为例,探讨了轴向压力对管柱内、外侧最大相当应力的影响。算例结果表明,螺旋屈曲管柱内侧最大相当应力恒大于外侧;管柱内、外侧最大相当应力随轴向压力的增大而增大。轴向压力由200KN 增大至800KN 时,管柱内、外侧最大相当应力分别增大170%和413.8%。研究弥补了传统管柱力学分析的不足,提供了螺旋屈曲管柱安全性研究新方法,同时也可为现场安全施工提供参考。%To make clear stress distribution and variation of helical buckling tubing string, the formulas of equivalent stresses inside and outside of the tubing string were deduced based on the spring theory and the fourth strength theory. Taking tubing string and casing commonly used in oilfield as object, stress calculation programs were compiled to explore the influence of axial compression load on equivalent VonMises stress. From the analysis, we can see that the equivalent VonMises stresses inside of the helical buckling tubing string were higher than that outside. The equivalent VonMises stress increased with the axial compression load, and the increase is 170 percent and 413.8 percent respectively for stress inside and outside of the tubing string with compression load increased from 200KN to 800KN. The proposed method used for the helical buckling tubing string covered the shortage of traditional tubular mechanics effectively and can also provide reference for the field application.

  10. Some factors affecting the compressive strength of nickel slag autoclaved product%影响镍渣蒸压制品抗压强度的因素研究

    Institute of Scientific and Technical Information of China (English)

    余涛; 曹德光; 刘文威; 李浩璇; 陆石强

    2013-01-01

    试验利用镍渣、水泥熟料、熟石灰、电石渣等原料制备镍渣蒸压制品,探索了成型压力、增强剂加入量、加水量和蒸养制度等因素对镍渣蒸压制品抗压强度的影响规律.结果表明,本试验合适的成型压力为15~20 MPa,增强剂的最佳加入量为0.5%,合理的加水量为8.57%~10.00%,最佳的蒸压养护温度为180℃或190℃,对应的蒸压养护时间为8h或9h.此外,使用电石渣代替熟石灰利用相同工艺条件制备蒸压制品的抗压强度无明显差异.%Prepared from autoclaved product of nickel slag,cement clinker,slaked lime,carbide slag,the experiment studied some factors that affecting the compressive strength of nickel slag autoclaved product,such as molding pressure,content of enhancer,content of water added,steam curing system and so on.The results show that the suitable molding pressure is 15~20 MPa;the optimum enhancer content is 0.5%;the reasonable amount of water added is 8.57%~10.00%;the best autoclaving temperature is 180 ℃ or 190 ℃;autoclaving time is eight or nine hours.In addition,under the same process conditions,autoclaved product was successfully prepared if using carbide slag instead of slaked lime,and the compressive strength of autoclaved product had no significant difference.

  11. Effect of Pulverized Fuel Ashes on Autogenous Shrinkage and Compressive Strength of Cement Pastes%粉煤灰对水泥浆体自收缩和抗压强度的影响

    Institute of Scientific and Technical Information of China (English)

    郝成伟; 邓敏; 莫立武; 刘开伟

    2011-01-01

    Autogenous shrinkage of cement pastes with different contents of pulverized fuel ashes(PFA) and different water-to-binder ratio were measured by a shrinkage test device. Compressive strength of sealed cement paste were also measured. The influence of PFA on the pore structures and micrograph of hydration products were investigated through mercury intrusion porosimetry(MIP) and scanning electron microscopy(SEM) , on which the influence mechanism was analyzed. Experimental results demonstrated that autogenous shrinkage of cement pastes decreased with the increased contents of PFA at early age (before 7 d) , this may be ascribed to inhibition of PFA on the shrinkage. After 7 d, however, both autogenous shrinkage, and compressive strength of cement pastes increased. This may be attributed to decrease of pore radius and densification of cement hydration products due to the pozzolanic reaction of fly ash.%设计组装了水泥浆体自收缩测量装置,进行了不同粉煤灰掺量和水胶比的水泥浆体自收缩和抗压强度测试,采用压汞测孔仪(MIP)、扫描电镜(SEM)等测试技术研究了粉煤灰对水泥浆体孔结构、产物形貌等微观结构的影响,并对其影响机理进行了分析.结果表明:粉煤灰能够有效抑制水泥浆体的早期自收缩,在7d前,其自收缩随着粉煤灰掺量的增加而减小;与纯硅酸盐水泥浆体相比,粉煤灰水泥浆体7d后的抗压强度增幅较大,但自收缩增长速率也趋于增大;火山灰反应引起的孔径细化、水化产物结构致密是粉煤灰影响水泥浆体自收缩和抗压强度的根本原因.

  12. Morphological and Strength Properties of Tanjung Bin Coal Ash Mixtures for applied in Geotechnical Engineering Work

    Directory of Open Access Journals (Sweden)

    Abd. Rahim Awang

    2012-01-01

    Full Text Available In Malaysia, coal has been used as a raw material to generate electricity since 1988. In the past, most of the wastage of coal burning especially the bottom ash was not managed properly as it was dumped in the waste pond and accumulated drastically.This paper focuses on some properties of coal ash mixtures (fly  ash and bottom ash mixtures from Tanjung Bin power plant. The characteristics studied were morphological properties, compaction behaviour and strength properties. Strength properties of coal ash mixtures are carried out by conducting direct shear test and unconfined compression test. Besides, morphology and mineralogy of coal ash mixtures are studied using scanning electron microscope (SEM and x-ray diffraction (XRD. The coal ash mixtures were compacted at 95% of maximum dry density, sealed and cured for 0, 14, and 28 days before they were analysed for shear strength, morphological and mineralogical analyses. The shear strength of coal ash mixtures varied depending on the fly ash compositions. The maximum shear strength was obtained at mixture with 50%FA: 50%BA and the value increased with curing periods. The friction angle obtained ranged from 27° to 37°. Morphological analysis showed that the number of irregular shaped particles increased confirming change in material type with curing period. From mineralogical analysis, the crystalline compounds present in Tanjung Bin coal ash were Mullite, Quartz, Calcium Phosphide, Calcite, Cristobalite and Hematite. It can be concluded that the coal ash mixtures can advantageously be applied in the construction of embankments, roads, reclamation and fill behind retaining structures.

  13. 掺活化煤矸石粉、粉煤灰水泥砂浆抗压强度预测%Prediction of compressive strength of cement mortars with fly ash and activated coal gangue

    Institute of Scientific and Technical Information of China (English)

    周双喜; 陈益民; 张文生

    2006-01-01

    The pozzolanic activity of coal gangue, which is calcining at 500 to 1 000 ℃, differs distinctly. The simplex-centroid design with upper and lower bounds of component proportion is adopted to study the compressive strength of mortars made with ternary blends of cement, activated coal gangue and fly ash. Based on the results of a minimum of seven design points, three special cubic polynomial models are used to establish the strength predicating equations at different ages for mortars. Five experimental checkpoints were also designed to verify the precision of the equations. The most frequent errors of the predicted values are within 3%. A simple and practical way is provided for determining the optimal proportion of two admixtures when they are used in concrete.%煤矸石经不同的温度(500~1000 ℃)热活化后,其辅助胶凝性能相差很大.为了研究双掺活化煤矸石与粉煤灰对水泥强度性能的影响,运用单纯形-中心设计方法,并确立各组分的上下限,通过7组砂浆实验,得出活化煤矸石粉、粉煤灰多元复合水泥不同龄期强度数学模型,并利用5组砂浆实验,对强度预测方程的精确性进行了研究.实验结果表明方程的计算值与实验测量值相差很小,误差范围在3%以下.为配制多种混合材的复合水泥最优配比提供了一个简单实用的方法.

  14. Revisiting the Bjerrum’s correction factor:Use of the liquidity index for assessing the effect of soil plasticity on undrained shear strength

    Institute of Scientific and Technical Information of China (English)

    Kamil Kayabali; Ozgur Akturk; Mustafa Fener; Orhan Dikmen; Furkan Hamza Harputlugil

    2015-01-01

    The undrained shear strength (su) of fine-grained soils that can be measured in situ and in laboratory is one of the key geotechnical parameters. The unconfined compression test (UCT) is widely used in lab-oratory to measure this parameter due to its simplicity; however, it is severely affected by sample disturbance. The vane shear test (VST) technique that is less sensitive to sample disturbance involves a correction factor against the soil plasticity, commonly known as the Bjerrum’s correction factor, m. This study aims to reevaluate the Bjerrum’s correction factor in consideration of a different approach and a relatively new method of testing. Atterberg limits test, miniature VST, and reverse extrusion test (RET) were conducted on 120 remolded samples. The effect of soil plasticity on undrained shear strength was examined using the liquidity index instead of Bjerrum’s correction factor. In comparison with the result obatined using the Bjerrum’s correction factor, the undrained shear strength was better represented when su values were correlated with the liquidity index. The results were validated by the RET, which was proven to take into account soil plasticity with a reliable degree of accuracy. This study also shows that the RET has strong promise as a new tool for testing undrained shear strength of fine-grained soils.

  15. Revisiting the Bjerrum's correction factor: Use of the liquidity index for assessing the effect of soil plasticity on undrained shear strength

    Directory of Open Access Journals (Sweden)

    Kamil Kayabali

    2015-12-01

    Full Text Available The undrained shear strength (su of fine-grained soils that can be measured in situ and in laboratory is one of the key geotechnical parameters. The unconfined compression test (UCT is widely used in laboratory to measure this parameter due to its simplicity; however, it is severely affected by sample disturbance. The vane shear test (VST technique that is less sensitive to sample disturbance involves a correction factor against the soil plasticity, commonly known as the Bjerrum's correction factor, μ. This study aims to reevaluate the Bjerrum's correction factor in consideration of a different approach and a relatively new method of testing. Atterberg limits test, miniature VST, and reverse extrusion test (RET were conducted on 120 remolded samples. The effect of soil plasticity on undrained shear strength was examined using the liquidity index instead of Bjerrum's correction factor. In comparison with the result obatined using the Bjerrum's correction factor, the undrained shear strength was better represented when su values were correlated with the liquidity index. The results were validated by the RET, which was proven to take into account soil plasticity with a reliable degree of accuracy. This study also shows that the RET has strong promise as a new tool for testing undrained shear strength of fine-grained soils.

  16. Non-linear model for compression tests on articular cartilage.

    Science.gov (United States)

    Grillo, Alfio; Guaily, Amr; Giverso, Chiara; Federico, Salvatore

    2015-07-01

    Hydrated soft tissues, such as articular cartilage, are often modeled as biphasic systems with individually incompressible solid and fluid phases, and biphasic models are employed to fit experimental data in order to determine the mechanical and hydraulic properties of the tissues. Two of the most common experimental setups are confined and unconfined compression. Analytical solutions exist for the unconfined case with the linear, isotropic, homogeneous model of articular cartilage, and for the confined case with the non-linear, isotropic, homogeneous model. The aim of this contribution is to provide an easily implementable numerical tool to determine a solution to the governing differential equations of (homogeneous and isotropic) unconfined and (inhomogeneous and isotropic) confined compression under large deformations. The large-deformation governing equations are reduced to equivalent diffusive equations, which are then solved by means of finite difference (FD) methods. The solution strategy proposed here could be used to generate benchmark tests for validating complex user-defined material models within finite element (FE) implementations, and for determining the tissue's mechanical and hydraulic properties from experimental data.

  17. 4种窝沟封闭剂微渗漏及抗压强度的比较实验%Comparative study on microleakage and compressive strength of four fissure sealants

    Institute of Scientific and Technical Information of China (English)

    蔡雅; 沈家平

    2013-01-01

    目的:比较4种窝沟封闭剂的微渗漏及抗压强度,为临床选择使用提供实验室依据.方法:收集12 ~16周岁志愿者因正畸治疗需要而新鲜拔除的前磨牙28个,并将其随机分为A、B、C、D4组(n=7),分别用Helioseal F、VOCO Fissurit F、AscentTM和ClinproTM封闭(牙合)面及颊、舌侧窝沟;冷热循环100次后,分别从每组中各随机抽取5个用20 mg/L的亚甲蓝染色检查微渗漏;所余2个用扫描电镜观察窝沟封闭剂与牙体组织结合界面及两者之间的密合度.取4种窝沟封闭剂分别制作直径4 mm,厚4 mm的盘状标本各9个,置于生理盐水中37℃下浸泡.分别于浸泡后ld、28 d、63 d后测定各标本的抗压强度(n=3).结果:4种封闭剂之间微渗漏评分均无显著性差异(P>0.05);扫描电镜观察显示,VOCO Fissurit F与牙釉质完全结合在一起,并渗透到窝沟底部,Helioseal F、AscentTM、ClinproTM虽与釉质结合较紧密但窝沟底部的封闭剂中有气泡或断裂.4种封闭剂中AscentTM组3个时间点的抗压强度均高于其他3组(P<0.05),而另3组各时间点内两两相比均无统计学差异(P>0.05).结论:VOCO Fissurit F的边缘密合性相对较好;AscentTM的抗压强度较高.%AIM:To evaluate the microleakage and compressive strength of 4 fissure sealants.METHODS:28 caries-free premolars extracted for orthodontic reasons from 12-16 years old volunteers were collected and randomly divided into 4 groups(n =7).Fissures were respectively sealed with Helioseal F,VOCO Fissurit F,AscentMT,and ClinproMT pit and fissure sealant.Then the teeth were thermocyclinged for 100 times.5 teeth in each group were stained with 20 mg/L methylene blue for 24 hours,and then were sectioned for the evaluation of microleakage.The remaining 2 teeth in each group were used for the observation of marginal adaptability of fissure sealants with tooth interface by SEM.9 disc-like specimens (with the thickness on 4mm diameter on 4mm) were prepared

  18. Stress-Strain Relationship of High-Strength Steel Fiber Reinforced Concrete in Compression%钢纤维高强混凝土单轴压缩下应力应变关系

    Institute of Scientific and Technical Information of China (English)

    严少华; 钱七虎; 孙伟; 尹放林

    2001-01-01

    在实际工程中推广应用钢纤维高强混凝土,要了解其基本力学性能.采用MTS815.03型液压伺服刚性压力试验机,对钢纤维含量为0~6%、抗压强度在65~120MPa范围的4种钢纤维高强混凝土,进行单轴压缩荷载作用下的应力应变全过程试验.结合试验给出全曲线的方程,并分析钢纤维对抗压强度、弹性模量、韧度、泊松比等的影响.试验表明,当钢纤维长度大于或接近于最大集料尺寸时,钢纤维高强混凝土具有较高的抗压强度和韧度,是一种优良的新型建筑材料.%It is necessary to research the basic mechanical performance inorder to use high-strength steel fiber reinforced concrete (HSFC) in practical engineering. Tests are conducted to characterize the stress-strain relationship of HSFC in compression by MTS815.03 rock testing machine. The concrete strength investigated ranges from 65 to 120 MPa and the volume fraction of steel fiber ranges from 0 to 6%. Based on the test data, an analytical model is proposed to generate the complete stress-strain curve for HSFC. The elastic modulus and toughness and Poisson’s ration of HSFC are also calculated in this paper. It is also proved by tests that HSFC is a good building material with high strength and high toughness when steel fibers are longer than the size of aggregate in concrete.

  19. 饱和粉细砂水泥土强度特性试验研究%Experimental study on characteristics strength of cement soil saturated sand

    Institute of Scientific and Technical Information of China (English)

    魏建菊

    2015-01-01

    新建铁路格尔木至库尔勒线DK16+108-DK56+950段经过草滩、湿地、沼泽等地段,由于地下水位较高或常年积水,粉土、粉细砂呈松散、饱和状,强度低,工程性质差,设计拟采用水泥土搅拌桩对该段地基进行加固处理.通过试验对水泥、粉煤灰与饱和粉细砂搅拌后的无侧限抗压强度增长规律进行研究,探讨了饱和粉细砂水泥土无侧限抗压强度与"二灰"(水泥、粉煤灰掺合料)掺入比、养护龄期的关系.试验结果表明:水泥对饱和粉细砂具有良好的固化作用;饱和粉细砂的无侧限抗压强度随二灰掺入比的增大呈指数形式增长,随养护龄期的增大呈幂函数形式增长;回归分析表明具有良好的线性相关性,可以用28d强度对90d强度进行预测.%Golmud to Korla DK16+108-DK56+950 new railway through the marsh,swamp wetland, such as. Because of the high underground water level or perennial water, Silt, silty sand is loose, saturated, low strength, poor engineering properties, The design of the cement soil mixing pile in the foundation reinforcement treatment.Through the test of cement, fly ash and saturated sand after mixing theunconfined compressive strength increasing rule research, Discussion on the saturated sand cement soil unconfined compressivestrength and the "two ash" (cement, fly ash admixture) incorporationratio, curing age. Test results show that: the cement has good curing effect of saturated silty sand;Saturated sand soil unconfined compressive strength ratio increasesexponentially with the two ash incorporation, with increase of curing period as a power function of growth; Regression analysis showed that has a good linear correlation, 28d can be used to predict the strength of the strength of 90d.

  20. Three-dimensional conceptual model for the Hanford Site unconfined aquifer system: FY 1994 status report

    Energy Technology Data Exchange (ETDEWEB)

    Thorne, P.D.; Chamness, M.A.; Vermeul, V.R.; Macdonald, Q.C.; Schubert, S.E.

    1994-11-01

    This report documents work conducted during the fiscal year 1994 to development an improved three-dimensional conceptual model of ground-water flow in the unconfined aquifer system across the Hanford Site Ground-Water Surveillance Project, which is managed by Pacific Northwest Laboratory. The main objective of the ongoing effort to develop an improved conceptual model of ground-water flow is to provide the basis for improved numerical report models that will be capable of accurately predicting the movement of radioactive and chemical contaminant plumes in the aquifer beneath Hanford. More accurate ground-water flow models will also be useful in assessing the impacts of changes in facilities and operations. For example, decreasing volumes of operational waste-water discharge are resulting in a declining water table in parts of the unconfined aquifer. In addition to supporting numerical modeling, the conceptual model also provides a qualitative understanding of the movement of ground water and contaminants in the aquifer.

  1. Three dimensional analysis of unconfined seepage in earth dams by the weak form quadrature element method

    Science.gov (United States)

    Yuan, Shuai; Zhong, Hongzhi

    2016-02-01

    It remains challenging to determine the unknown free surface in three dimensional unconfined seepage in earth dams. A number of iterations are frequently required which make the problem computationally expensive. In the present research, a weak form quadrature element formulation is presented for three dimensional analysis of unconfined seepage which is an extension of the recently established method for two dimensional seepage problems. "Free points" are introduced by the interpolation of which the free surfaces are smoothly approximated. Grid lines are constructed in the element and the "free points" are confined to the lines when updated. An interpolatory scheme for locating the exit points is proposed. Formulations and procedures of the method are given in detail. Results of numerical examples are compared with available analytical solutions and numerical solutions in the literature and agreement is reached demonstrating the efficiency and reliability of the present formulation.

  2. Compression strength of composite primary structural components

    Science.gov (United States)

    Johnson, Eric R.

    1994-01-01

    The linear elastic response is determined for an internally pressurized, long circular cylindrical shell stiffened on the inside by a regular arrangement of identical stringers and identical rings. Periodicity of this configuration permits the analysis of a portion of the shell wall centered over a generic stringer-ring joint; i.e., a unit cell model. The stiffeners are modeled as discrete beams, and the stringer is assumed to have a symmetrical cross section and the ring an asymmetrical section. Asymmetery causes out-of-plane bending and torsion of the ring. Displacements are assumed as truncated double Fourier series plus simple terms in the axial coordinate to account for the closed and pressure vessel effect (a non-periodic effect). The interacting line loads between the stiffeners and the inside shell wall are Lagrange multipliers in the formulation, and they are also assumed as truncated Fourier series. Displacement continuity constraints between the stiffeners and shell along the contact lines are satisfied point-wise. Equilibrium is imposed by the principle of virtual work. A composite material crown panel from the fuselage of a large transport aircraft is the numerical example. The distributions of the interacting line loads, and the out-of-plane bending moment and torque in the ring, are strongly dependent on modeling the deformations due to transverse shear and cross-sectional warping of the ring in torsion. This paper contains the results from the semiannual report on research on 'Pressure Pillowing of an Orthogonally Stiffened Cylindrical Shell'. The results of the new work are illustrated in the included appendix.

  3. Robust evidence for random fractal scaling of ground water levels in unconfined aquifers

    OpenAIRE

    Little, Max A.; Bloomfield, John P.

    2010-01-01

    This study introduces new approaches to improve the statistical robustness of techniques for quantifying the fractal scaling of groundwater levels, and uses these techniques to investigate scaling of groundwater levels from a consolidated permeable carbonate aquifer. Six groundwater level time series and an associated river stage time series from the unconfined Chalk aquifer (a dual-porosity, fractured limestone aquifer) in the Pang–Lambourn catchment, UK, have been analysed. Surrogate data o...

  4. Stepwise pumping approach to improve free phase light hydrocarbon recovery from unconfined aquifers

    OpenAIRE

    Cooper, Grant; Peralta, R. C.; Kaluarachchi, Jagath J.

    1995-01-01

    A stepwise, time-varying pumping approach is developed to improve free phase oil recovery of light non-aqueous phase liquids {LNAPL) from a homogeneous, unconfined aquifer. Stepwise pumping is used to contain the floating oil plume and obtain efficient free oil recovery. The pumping approach is developed using detailed simulations, multiple linear regression and graphical plots. The approach uses ARMOS©, an areal two-dimensional multiphase flow, finite-element simulation model. Systematic sim...

  5. The Effects of Eggshell Ash on Strength Properties of Cement-stabilized Lateritic

    Directory of Open Access Journals (Sweden)

    Okonkwo U. N

    2012-04-01

    Full Text Available Eggshell ash obtained by incinerating Fowls’ eggshells to ash has been established to be a good accelerator for cement-bound materials and this would be useful for road construction work at the peak of rainy seasons for reducing setting time of stabilized road pavements. However this should be achieved not at the expense of other vital properties of the stabilized matrix. This is part of the effort in adding value to agricultural materials which probably cause disposal problems. Thus this study aimed at determining the effect of eggshell ash on the strength properties of cement-stabilized lateritic soil. The lateritic soil was classified to be A-6(2 in AASHTO rating system and reddish-brown clayey sand (SC in the Unified Classification System. Constant cement contents of 6% and 8% were added to the lateritic soil with variations in eggshell ash content of 0% to 10% at 2% intervals. All proportions of cement and eggshell ash contents were measured in percentages by weight of the dry soil. The Compaction test, California Bearing Ratio test, Unconfined Compressive Strength test and Durability test were carried out on the soil-cement eggshell ash mixtures. The increase in eggshell ash content increased the Optimum Moisture Content but reduced the Maximum Dry Density of the soil-cement eggshell ash mixtures. Also the increase in eggshell ash content considerably increased the strength properties of the soil-cement eggshell ash mixtures up to 35% in the average but fell short of the strength requirements except the durability requirement was satisfied.

  6. Compressed Teleportation

    CERN Document Server

    Jaffe, Arthur; Wozniakowski, Alex

    2016-01-01

    In a previous paper we introduced holographic software for quantum networks, inspired by work on planar para algebras. This software suggests the definition of a compressed transformation. Here we utilize the software to find a CT protocol to teleport compressed transformations. This protocol serves multiple parties with multiple persons.

  7. Validation of hydraulic tomography in an unconfined aquifer: A controlled sandbox study

    Science.gov (United States)

    Zhao, Zhanfeng; Illman, Walter A.; Yeh, Tian-Chyi J.; Berg, Steven J.; Mao, Deqiang

    2015-06-01

    In this study, we demonstrate the effectiveness of hydraulic tomography (HT) that considers variably saturated flow processes in mapping the heterogeneity of both the saturated and unsaturated zones in a laboratory unconfined aquifer. The successive linear estimator (SLE) developed by Mao et al. (2013c) for interpreting HT in unconfined aquifers is utilized to obtain tomograms of hydraulic conductivity (K), specific storage (Ss), and the unsaturated zone parameters (pore size parameter (α) and saturated water content (θs)) for the Gardner-Russo's model. The estimated tomograms are first evaluated by visually comparing them with stratigraphy visible in the sandbox. Results reveal that the HT analysis is able to accurately capture the location and extent of heterogeneity including high and low K layers within the saturated and unsaturated zones, as well as reasonable distribution patterns of α and θs for the Gardner-Russo's model. We then validate the estimated tomograms through predictions of drawdown responses of pumping tests not used during the inverse modeling effort. The strong agreement between simulated and observed drawdown curves obtained by pressure transducers and tensiometers demonstrates the robust performance of HT that considers variably saturated flow processes in unconfined aquifers and the unsaturated zone above it. In addition, compared to the case using the homogeneous assumption, HT results, as expected, yield significantly better predictions of drawdowns in both the saturated and unsaturated zones. This comparison further substantiates the unbiased and minimal variance of HT analysis with the SLE algorithm.

  8. 脱硫石膏-粉煤灰地聚合物抗压强度和反应机理%Compressive Strength and Mechanism of Geopolymers from Flue Gas Desulferization Gypsum and Fly Ash

    Institute of Scientific and Technical Information of China (English)

    郭晓潞; 施惠生

    2012-01-01

    The sodium water glass activated geopolymers were prepared from solid wastes of fly ash and flue gas desulfurization gypsum (FGDG). Compressive strength and mechanism of these geopolymers were also studied by using X ray diffraction (XRD) and scanning electron microscopy (SEM). When the FGDG baked at 800℃ for 1 h the FGDG had a more flabby structure and disfigurement, and became more active. The blend of 90% of fly ash and 10% of FGDG baked at 800℃ for 1 h was activated by sodium water glass, and the geopolymer was formed and the specimens were demoulded. The compressive strength of these geopolyme specimens cured at 23℃ for 28 days or at 75℃ for 8 h reached 37. 0 MPa. Activated by alkali activator and sulfate activator, geopolymerization products and hydration products of geopolymeric gel, zeolite, and ettringite etc. were formed. Preparation of geopolymes from fly ash and FGDG is beneficial for utilizing of multi industrial wastes, especially, the wastes containing silicate, aluminum, and sulfate.%经钠水玻璃激发固体废弃物脱硫石膏和粉煤灰,成功研制了脱硫石膏-粉煤灰地聚合物,研究了该地聚合物的抗压强度,并采用X射线衍射分析(XRD)和扫描电镜(SEM)等测试方法研究了其反应机理.研究表明:经800℃焙烧1h后的脱硫石膏结构松弛、缺陷多、活性大,以10%掺量取代粉煤灰,经钠水玻璃激发形成的地聚合物,在75℃养护8h或在23℃养护至28 d,抗压强度均可达37.0 MPa.此反应体系中,碱激发与硫酸盐激发作用共存,地聚合反应与水化反应同时进行,生成了地聚合物凝胶、类沸石以及钙矾石等反应产物.脱硫石膏-粉煤灰地聚合物的成功研制,为实现多种工业废弃物的共处置利用,尤其是含硅铝相的工业废弃物和含硫酸钙的工业废弃物的共处置打下了理论基础.

  9. Shear Strength of Remoulding Clay Samples Using Different Methods of Moulding

    Science.gov (United States)

    Norhaliza, W.; Ismail, B.; Azhar, A. T. S.; Nurul, N. J.

    2016-07-01

    Shear strength for clay soil was required to determine the soil stability. Clay was known as a soil with complex natural formations and very difficult to obtain undisturbed samples at the site. The aim of this paper was to determine the unconfined shear strength of remoulded clay on different methods in moulding samples which were proctor compaction, hand operated soil compacter and miniature mould methods. All the samples were remoulded with the same optimum moisture content (OMC) and density that were 18% and 1880 kg/m3 respectively. The unconfined shear strength results of remoulding clay soils for proctor compaction method was 289.56kPa with the strain 4.8%, hand operated method was 261.66kPa with the strain 4.4% and miniature mould method was 247.52kPa with the strain 3.9%. Based on the proctor compaction method, the reduction percentage of unconfined shear strength of remoulded clay soil of hand operated method was 9.66%, and for miniature mould method was 14.52%. Thus, because there was no significant difference of reduction percentage of unconfined shear strength between three different methods, so it can be concluded that remoulding clay by hand operated method and miniature mould method were accepted and suggested to perform remoulding clay samples by other future researcher. However for comparison, the hand operated method was more suitable to form remoulded clay sample in term of easiness, saving time and less energy for unconfined shear strength determination purposes.

  10. Compressive strain-dependent bending strength property of Al{sub 2}O{sub 3}-ZrO{sub 2} (1.5 mol% Y{sub 2}O{sub 3}) composites performance by HIP

    Energy Technology Data Exchange (ETDEWEB)

    Reyes-Rojas, A. [Centro de Investigacion en Materiales Avanzados S.C. (CIMAV), Miguel de Cervantes 120, Complejo Industrial Chihuahua, Cd. de Chihuahua, Chihuahua (Mexico)], E-mail: armando_reyesmx@yahoo.com.mx; Esparza-Ponce, H. [Centro de Investigacion en Materiales Avanzados S.C. (CIMAV), Miguel de Cervantes 120, Complejo Industrial Chihuahua, Cd. de Chihuahua, Chihuahua (Mexico); De la Torre, S.D. [Centro de Investigacion e Innovacion Tecnologica (CIITEC)-IPN, D.F. Mexico (Mexico); Torres-Moye, E. [Centro de Investigacion en Materiales Avanzados S.C. (CIMAV), Miguel de Cervantes 120, Complejo Industrial Chihuahua, Cd. de Chihuahua, Chihuahua (Mexico)

    2009-04-15

    Nanometric powders and sintered ceramics of Al{sub 2}O{sub 3}-ZrO{sub 2} (1.5 mol% Y{sub 2}O{sub 3}) prepared by hot isostatic pressing HIP have been studied. A detailed crystallographic study has been performed through X-ray diffraction, Williamson-Hall method, Rietveld method and high-resolution electron microscopy HREM analysis. The crystallographic structure data, such as domain size, lattice parameters, wt% phase, and micro-strain direction have been obtained using Rietveld refinement and Williamson-Hall methods. The results revealed that the compressive strain ({epsilon}) increased from 0.56 to 1.18 (10{sup -3}) as the t-ZrO{sub 2} content increased too. The HREM interface study conducted along the [0 0 0 1]Al{sub 2}O{sub 3}||[0 0 1]ZrO{sub 2} zone axis revealed a micro-strain lattice distortion accumulated at the grain boundary due to the ZrO{sub 2} martensitic phase transformation on cooling, t-ZrO{sub 2} grains coalescence and to the grain growth of {alpha}-Al{sub 2}O{sub 3} which cause elongated tetragonal crystals. Micro-strain lattice distortion is adjusted by the shear displacements of the planes (1 1 0) and (11-bar0) along [1-bar10] and [1-bar1-bar0] crystallographic directions, respectively; these planes are arrested by the (101-bar0) alumina plane. In this case, semi-coherent interfaces were observed along the grain boundary. It is verified that the bending strength increased in connection with the strain accumulation and amount of tetragonal structure.

  11. 一种复配表面施胶剂对瓦楞纸板边压强度的影响%Effect of Compound Surface Sizing Agent on Edgewise Compression Strength of Corrugated Paperboard

    Institute of Scientific and Technical Information of China (English)

    郝笑梦; 张新昌

    2012-01-01

    分别以氧化淀粉、CMC和SAE类表面合成施胶剂为强化助剂,对瓦楞纸板进行了表面涂覆试验,研究了其边压强度变化情况;将上述施胶剂复配,以分散剂CMC用量、氧化淀粉与SAE混合溶液的质量分数、氧化淀粉与SAE配比、施胶温度为因素,应用正交试验法进行复配效果研究。试验结果表明,氧化淀粉、SAE和CMC的复配,比单独使用具有更好的增强效果。试验获得的最佳瓦楞纸板强化工艺参数是:CMC质量分数为5%,氧化淀粉与SAE混合溶液质量分数为9%,氧化淀粉与SAE质量比为1:10,施胶温度为85℃。%The edgewise compression strength of corrugated paperboard with oxidized starch,CMC,SAE synthesized surface sizing agent was studied.The effects of the amount of CMC,which was the dispersant,the mixed solution of oxidized starch and SAE,the proportion of oxidized starch and SAE,and the sizing temperature were investigated.The results showed that the combination of oxidized starch,CMC,SAE has better strengthening effect than used alone.The optimum technical strengthening conditions of corrugated board are 5%CMC,9% mass fraction of mixed solution of oxidized starch and SAE,1:10 mass ratio of oxidized starch and SAE,and sizing temperature 85 ℃.

  12. Study on Compressive Strength of 2 . 5 D Woven Composite Materials using Puck′s Criteria%基于Puck准则的2.5 D机织复合材料压缩性能研究

    Institute of Scientific and Technical Information of China (English)

    季乐; 周光明; 王新峰; 孙琎; 王宇

    2016-01-01

    Parametric models of 2 . 5 D fiber reinforced composite material were established with density of warp and weft by Catia software. By the professional tools HyperMesh,the mesh was generated. Based up-on this,boundary periodical condition was embed using Fortran. The damage constitution model of the composites based on Puck criteria was carried out by VUMAT subroutine in Abaqus. The damage of the bonded interface was simulated by cohesive element. Through the progressive damage analysis, woven structure's module ,longitude compressive strength and fracture trace were accessed. The results of simula-tion were analyzed,and were compared with the experimental results,which were obtained from the speci-men using RTM method. The experiments certified that simulation is reasonable.%利用CATIA软件以经纬密为参数建立了2.5D纤维增强浅交弯联复合材料的参数化有限元模型,在Hy-perMesh专业网格划分工具中划分周期性网格,编写了Fortran程序嵌入周期性边界条件。采用Abaqus软件中VU-MAT子程序功能编写了基于Puck准则的材料损伤本构模型,通过渐进损伤分析,得到了机织织物宏观弹性模量以及经向压缩强度、破坏路径,并对破坏结果进行了分析。利用RTM工艺复合成型试件并进行力学测试,实验结果证实了仿真分析的准确性。

  13. Dynamic strength of reaction-sintered boron carbide ceramic

    Science.gov (United States)

    Savinykh, A. S.; Garkushin, G. V.; Razorenov, S. V.; Rumyantsev, V. I.

    2015-06-01

    The shock compression wave profiles in three modifications of boron carbide ceramic are studied in the compressive stress range 3-19 GPa. The Hugoniot elastic limit and the spall strength of the materials are determined. It is confirmed that the spall strength of high-hardness ceramic changes nonmonotonically with the compressive stress in a shock wave.

  14. 粉煤灰对硅酸盐水泥-铝酸盐水泥-硬石膏体系性能的影响%Influence of fly ash on compressive strength with portland cement-aluminate cement-anhydrite system

    Institute of Scientific and Technical Information of China (English)

    李海南; 马保国; 张承志

    2014-01-01

    This paper studies the influence of amount of mixed fly ash (0 %, 10 %, 20 %, 30 %) on compressive strength with portland cement-aluminate cement-anhydrite system. Experimental results show that with the increase of fly ash, the compressive and transverse strength decreases; With the prolonging of curing age, the compressive and transverse strength decrease slowly.%研究了不同掺量的粉煤灰(0%,10%,20%,30%)对硅酸盐水泥-铝酸盐水泥-硬石膏三元复合体系力学性能的影响。试验结果表明:随着粉煤灰掺量的增加,该三元体系浆体的抗压、抗折强度均减小,但减小的程度不一致,与养护龄期有关。随着养护龄期的延长,砂浆抗压、抗折强度降低幅度减小。这可能是由于在浆体水化后期,粉煤灰的火山灰作用起了一定的作用。

  15. Silicon powder-experimental study on the influence of the fly ash to the strength of cement-soil%双掺粉煤灰硅粉对水泥土抗压强度影响试验研究

    Institute of Scientific and Technical Information of China (English)

    李俊哲; 方光秀

    2016-01-01

    以吉林省延吉市砂土作为研究对象,对双掺硅粉—粉煤灰水泥土进行了无侧限抗压强度试验,分析不同粉煤灰、硅粉掺量以及各龄期对硅粉—粉煤灰水泥土抗压强度的影响,结果表明:随粉煤灰与硅粉掺量的增加,水泥土后期强度基本呈增大趋势,随着粉煤灰掺量的增加,早期抗压强度逐渐减小,后期抗压强度则明显提高,掺硅粉不仅显著改善水泥土早期抗压强度,且明显提高其后期抗压强度。%Taking the sand in Yanji city as the research object,we made an unconfined compressive strength test on the silica fume and fly ash cement. We studied on the effect of silica fume and fly ash cement compressive strength when it was mixed with different amount of fly ash and silica fume. The results showed that:the cement soil strength showed a trend of increase with the increase of fly ash and fume content,in the ear-ly stage,with the content of fly ash increasing,the comprehensive strength decreases gradually,but in the latter stage,it is obviously improved, silica fume can not only significantly improve the early strength of cement soil but also make great influence on the later strength.

  16. Kajian Efektifitas Penggunaan Semen dan Limbah Karbit Terhadap Stabilitas Tanah Lempung Dengan Pengujian Kuat Tekan Bebas (Unconfined Compression Test)

    OpenAIRE

    Yesika, Faraditha

    2016-01-01

    Tanah mempunyai peranan yang sangat penting sebagai media pondasi untuk menyebarkan beban bangunan kedalamnya.Kondisi tanah di setiap tempat sangatlah berbeda karena tanah secara ilmiah merupakan material yang rumit dan sangat bervariasi.Apabila suatu tanah yang terdapat di lapangan bersifat sangat lepas atau sangat lunak sehingga tidak sesuai untuk pembangunan, maka tanah tersebut sebaiknya distabilisasi.Bahantambahyangbiasadigunakanuntukstabilisasi tanahantaralain,semen,kapur, abuterbang,ab...

  17. Application of relevance vector machine to prediction of compressive strength of coral concrete%相关向量机在珊瑚混凝土抗压强度预测中的应用

    Institute of Scientific and Technical Information of China (English)

    李仲欣; 韦灼彬; 沈锦林

    2016-01-01

    Relevance vector machine is introduced to regress and predict the compressive strength of coral concrete on a small sample, comparing with back propagation of neural network and least square support vector machine,it is found that relevance vector machine owns benign generalization ability so that over fitting which occurs in neural network could be avoided,not only the prediction accuracy of relevance vector machine is no worse than least square support vector machine,but also it can provide the confidence interval of predicted value;single-factor importance,single-factor effects and two-factor interaction are analyzed through the using of explanatory system estab-lished by relevance vector regression,results of simulation tests are coincide with that of actual test.It is indicated that relevance vector ma-chine is reliable tool for predicting performance of concrete,it can provide a guidance to the design and optimization of mixture.%应用相关向量机对珊瑚混凝土小样本数据进行回归和预测,与BP神经网络和最小二乘支持向量机的比较发现:相关向量机具有良好的泛化能力,避免了神经网络易出现的过拟合现象,不仅预测准确率不低于最小二乘支持向量机,而且能输出预测值的置信区间;利用相关向量机回归构建解释体系,分析配合比中各组分的重要性、单因子效应及两因素间交互作用,仿真结果与实际结果一致。相关向量机是混凝土性能预测的可靠工具,可为配合比设计和优化提供指导。

  18. Numerical study of two-phase unconfined fuel-air cloud characteristics to consider its detonability

    International Nuclear Information System (INIS)

    A numerical simulation is introduced to study the characteristics of unconfined fuel-air mixture in order to study its detonability. A modified version of KIVA-3V code is used to model the dispersal process. Some models are applied to determine the initial conditions, and a comparison is made between the results of these models. The outcome of this study can be used to predict the best time and position for secondary ignition action to detonate the cloud. A theoretical consideration along with a comparison with other works is made for validation. (author)

  19. An experimental approach to strain pattern and folding in unconfined and/or partitioned transpressional deformation

    Science.gov (United States)

    Ghosh, N.; Chakra, M.; Chattopadhyay, A.

    2014-01-01

    Three different series of experiments were carried out with pitch (bitumen) and/or composite pitch-plasticine models to observe the spatial and temporal changes of strain pattern and/or fold styles in a tectonic zone undergoing sinistral-sense unconfined transpression. In the first series, rectangular pitch models with circular strain markers, when subjected to vertically and laterally unconstrained transpression, showed that the circular markers deformed into ellipses with long axes (maximum instantaneous stretching axis: ISAmax) oriented plasticine layer placed over the pitch block initiated parallel to the long axis of the finite strain ellipse in transpression and rotated anticlockwise with increasing strain.

  20. Strength Measurements of Archive K Basin Sludge Using a Soil Penetrometer

    Energy Technology Data Exchange (ETDEWEB)

    Delegard, Calvin H.; Schmidt, Andrew J.; Chenault, Jeffrey W.

    2011-12-06

    Spent fuel radioactive sludge present in the K East and K West spent nuclear fuel storage basins now resides in the KW Basin in six large underwater engineered containers. The sludge will be dispositioned in two phases under the Sludge Treatment Project: (1) hydraulic retrieval into sludge transport and storage containers (STSCs) and transport to interim storage in Central Plateau and (2) retrieval from the STSCs, treatment, and packaging for shipment to the Waste Isolation Pilot Plant. In the years the STSCs are stored, sludge strength is expected to increase through chemical reaction, intergrowth of sludge crystals, and compaction and dewatering by settling. Increased sludge strength can impact the type and operation of the retrieval equipment needed prior to final sludge treatment and packaging. It is important to determine whether water jetting, planned for sludge retrieval from STSCs, will be effective. Shear strength is a property known to correlate with the effectiveness of water jetting. Accordingly, the unconfined compressive strengths (UCS) of archive K Basin sludge samples and sludge blends were measured using a pocket penetrometer modified for hot cell use. Based on known correlations, UCS values can be converted to shear strengths. Twenty-six sludge samples, stored in hot cells for a number of years since last being disturbed, were identified as potential candidates for UCS measurement and valid UCS measurements were made for twelve, each of which was found as moist or water-immersed solids at least 1/2-inch deep. Ten of the twelve samples were relatively weak, having consistencies described as 'very soft' to 'soft'. Two of the twelve samples, KE Pit and KC-4 P250, were strong with 'very stiff' and 'stiff' consistencies described, respectively, as 'can be indented by a thumb nail' or 'can be indented by thumb'. Both of these sludge samples are composites collected from KE Basin floor and

  1. Effect of desliming of sulphide-rich mill tailings on the long-term strength of cemented paste backfill.

    Science.gov (United States)

    Ercikdi, Bayram; Baki, Hakan; İzki, Muhammet

    2013-01-30

    This paper presents the effect of desliming on the short- and long-term strength, stability and rheological properties of cemented paste backfill (CPB) produced from two different mill tailings. A 28-day unconfined compressive strength (UCS) of ≥1.0 MPa and the maintenance of stability over 224 days of curing were selected as the design criteria for the evaluation of paste backfill performance. Desliming induced some changes in the physical, chemical, mineralogical and rheological properties of the tailings. CPB mixture of the deslimed tailings achieved the required consistency at a lower water to cement ratio. The short-term UCSs of CPB samples of the deslimed tailings were found to be 30-100% higher than those samples of the reference tailings at all the binder dosages and curing times. CPB samples of the deslimed tailings achieved the long-term stability at relatively low binder dosages (e.g. 5 wt% c.f. ≥6.1% for the reference tailings). It was also estimated that desliming could allow a 13.4-23.1% reduction in the binder consumption depending apparently on the inherent characteristics of the tailings. Over the curing period, generation of sulphate and acid by the oxidation of pyrite present in the tailings was also monitored to correlate with the strength losses observed in the long term. Scanning electron microscope (SEM) and Mercury Intrusion Porosimetry (MIP) analyses provided an insight into the microstructure of CPB and the formation of secondary mineral phases (i.e. gypsum) confirming the beneficial effect of desliming. These findings suggest that desliming can be suitably exploited for CPB of sulphide-rich mill tailings to improve the strength and stability particularly in the long term and to reduce binder consumption. PMID:23220652

  2. 混杂纤维自密实混凝土孔结构对抗压强度影响的试验研究%Experimental Study on the Influence of Pore Structure of Hybrid Fibers Self-compacting Concrete on Compressive Strength

    Institute of Scientific and Technical Information of China (English)

    骆冰冰; 毕巧巍

    2012-01-01

    采用压汞法对混杂纤维自密实混凝土进行微观孔结构试验,并进行抗压强度试验,分析了混杂纤维自密实混凝土孔结构的孔隙率、孔径尺寸与级配、孔分布特征与强度的关系,得出混杂纤维自密实混凝土孔结构与抗压强度的关系趋势.研究结果表明,在自密实混凝土中混杂掺人玄武岩纤维和聚丙烯纤维,其微观孔结构的改善对抗压强度的提高有着直接的影响.%This research used the method of mercury injection to test micro pore structure for mixed basalt fiber and polypropylene fiber of self-compacting concrete, tested the compressive strength of each specimen,and analyzed the hybrid fibers of self-compacting concrete with the pore structure of porosity, pore size and gradation,pore distribution characteristics and the relationship of the strength,then get the relationship between hybrid fiber of self-compacting concrete pore structure and compressive strength. The results showed that adding basalt fiber and polypropylene fiber in self-compacting concrete had a directly effect on improving the micro pore structure to raise the compressive strength.

  3. Approximate solutions for Forchheimer flow during water injection and water production in an unconfined aquifer

    Science.gov (United States)

    Mathias, Simon A.; Moutsopoulos, Konstantinos N.

    2016-07-01

    Understanding the hydraulics around injection and production wells in unconfined aquifers associated with rainwater and reclaimed water aquifer storage schemes is an issue of increasing importance. Much work has been done previously to understand the mathematics associated with Darcy's law in this context. However, groundwater flow velocities around injection and production wells are likely to be sufficiently large such as to induce significant non-Darcy effects. This article presents a mathematical analysis to look at Forchheimer's equation in the context of water injection and water production in unconfined aquifers. Three different approximate solutions are derived using quasi-steady-state assumptions and the method of matched asymptotic expansion. The resulting approximate solutions are shown to be accurate for a wide range of practical scenarios by comparison with a finite difference solution to the full problem of concern. The approximate solutions have led to an improved understanding of the flow dynamics. They can also be used as verification tools for future numerical models in this context.

  4. Vertical contamination in the unconfined groundwater at the Hanford Site, Washington

    International Nuclear Information System (INIS)

    Disposal to the ground at Hanford of large volumes of low- and intermediate-level wastes in the local unconfined groundwater flow system has raised concern about the movement and distribution of this waste. Previous work produced information on the horizontal movement of the waste, but little or no information exists on its vertical distribution within the unconfined groundwater flow system. In 1975 Phase I of a study was started to determine the vertical distribution of contaminants in three existing wells (699-28-40, 699-31-31, and 699-37-43). Because of negative results, only one well that produced positive results (699-31-31) was chosen for Phase II. Phase II consisted of tests conducted on this well by a testing company, with samples cross-checked by two different laboratories. Phase III was a cooperative study with Rockwell Hanford Operations, which included the installation, testing, and sampling of piezometers. The data were then analyzed using predictive codes and models in order to determine if vertical movement did occur. The present groundwater flow system shows some vertical contamination. However, concentrations are relatively higher near the surface of the flow system, indicating possible radial flow patterns from the groundwater mounds known to have developed under the chemical processing area disposal sites. Upward flow from deeper aquifers may be diluting the contaminant and masking a possible downward migration of contaminants

  5. Basin-scale conceptual groundwater flow model for an unconfined and confined thick carbonate region

    Science.gov (United States)

    Mádl-Szőnyi, Judit; Tóth, Ádám

    2015-11-01

    Application of the gravity-driven regional groundwater flow (GDRGF) concept to the hydrogeologically complex thick carbonate system of the Transdanubian Range (TR), Hungary, is justified based on the principle of hydraulic continuity. The GDRGF concept informs about basin hydraulics and groundwater as a geologic agent. It became obvious that the effect of heterogeneity and anisotropy on the flow pattern could be derived from hydraulic reactions of the aquifer system. The topography and heat as driving forces were examined by numerical simulations of flow and heat transport. Evaluation of groups of springs, in terms of related discharge phenomena and regional chloride distribution, reveals the dominance of topography-driven flow when considering flow and related chemical and temperature patterns. Moreover, heat accumulation beneath the confined part of the system also influences these patterns. The presence of cold, lukewarm and thermal springs and related wetlands, creeks, mineral precipitates, and epigenic and hypogenic caves validates the existence of GDRGF in the system. Vice versa, groups of springs reflect rock-water interaction and advective heat transport and inform about basin hydraulics. Based on these findings, a generalized conceptual GDRGF model is proposed for an unconfined and confined carbonate region. An interface was revealed close to the margin of the unconfined and confined carbonates, determined by the GDRGF and freshwater and basinal fluids involved. The application of this model provides a background to interpret manifestations of flowing groundwater in thick carbonates generally, including porosity enlargement and hydrocarbon and heat accumulation.

  6. Compressive beamforming

    DEFF Research Database (Denmark)

    Xenaki, Angeliki; Mosegaard, Klaus

    2014-01-01

    Sound source localization with sensor arrays involves the estimation of the direction-of-arrival (DOA) from a limited number of observations. Compressive sensing (CS) solves such underdetermined problems achieving sparsity, thus improved resolution, and can be solved efficiently with convex...

  7. Wellhead compression

    Energy Technology Data Exchange (ETDEWEB)

    Harrington, Joe [Sertco Industries, Inc., Okemah, OK (United States); Vazquez, Daniel [Hoerbiger Service Latin America Inc., Deerfield Beach, FL (United States); Jacobs, Denis Richard [Hoerbiger do Brasil Industria de Equipamentos, Cajamar, SP (Brazil)

    2012-07-01

    Over time, all wells experience a natural decline in oil and gas production. In gas wells, the major problems are liquid loading and low downhole differential pressures which negatively impact total gas production. As a form of artificial lift, wellhead compressors help reduce the tubing pressure resulting in gas velocities above the critical velocity needed to surface water, oil and condensate regaining lost production and increasing recoverable reserves. Best results come from reservoirs with high porosity, high permeability, high initial flow rates, low decline rates and high total cumulative production. In oil wells, excessive annulus gas pressure tends to inhibit both oil and gas production. Wellhead compression packages can provide a cost effective solution to these problems by reducing the system pressure in the tubing or annulus, allowing for an immediate increase in production rates. Wells furthest from the gathering compressor typically benefit the most from wellhead compression due to system pressure drops. Downstream compressors also benefit from higher suction pressures reducing overall compression horsepower requirements. Special care must be taken in selecting the best equipment for these applications. The successful implementation of wellhead compression from an economical standpoint hinges on the testing, installation and operation of the equipment. Key challenges and suggested equipment features designed to combat those challenges and successful case histories throughout Latin America are discussed below.(author)

  8. Compressive Fatigue in Wood

    DEFF Research Database (Denmark)

    Clorius, Christian Odin; Pedersen, Martin Bo Uhre; Hoffmeyer, Preben;

    1999-01-01

    An investigation of fatigue failure in wood subjected to load cycles in compression parallel to grain is presented. Small clear specimens of spruce are taken to failure in square wave formed fatigue loading at a stress excitation level corresponding to 80% of the short term strength. Four...... frequencies ranging from 0.01 Hz to 10 Hz are used. The number of cycles to failure is found to be a poor measure of the fatigue performance of wood. Creep, maximum strain, stiffness and work are monitored throughout the fatigue tests. Accumulated creep is suggested identified with damage and a correlation...

  9. Strength Training

    Science.gov (United States)

    ... person's own weight to build muscles and strength. Olympic lifting, or powerlifting, which people often think of ... in the group effectively. Here are some basic rules to follow in strength training: Start with body ...

  10. MANAGEMENT MODEL OF UNCONFINED AQUIFER SYSTEM WITH SMALL THICKNESS WITH RESPECT TO DRAWDOWN BASED ON TWO-LEVEL RESPONSE MATRIX

    Institute of Scientific and Technical Information of China (English)

    Cai-Zhi SUN; Wei ZOU; Xue-Yu LIN

    2004-01-01

    In the management of unconfined aquifer systems, if the thickness of the aquifer is very small and the drawdown is relatively big, errors may arise when the superposition principle is adopted.directly. In allusion to this limitation, a new management model for the management of unconfined aquifer systems called two-level response matrix method is put forward. This method is applied in groundwater resources management in Shenyang city. The managing results show that this methodcan, in some degree, increase the efficiency of management and decrease the risk of management.

  11. Mechanical properties of similar material under uniaxial compression and the strength error sources%相似材料单轴压缩力学性能及强度误差来源分析

    Institute of Scientific and Technical Information of China (English)

    洛锋; 杨本生; 郝彬彬; 孙利辉; 付明明

    2013-01-01

    In this paper, in order to improve the accuracy of similar simulation experiment, we tested the stress-strain behaviors of similar material specimens with different compositions (sand-plaster, sand-cement-plaster) and proportions by uniaxial compression testing, analyzed the mechanical properties and post-peak failure characteristics, and investigated the error sources during the production of similar material models and testing of specimens. The results show that: 1) The two similar materials both show good elastic-plastic properties in the loading process, thus, they can be used to simulate different rock mass; 2) The post-peak strain-softening processes of the two materials are smooth, and the residual strengths are stable; 3) Due to the insufficient cementation and primary damage of the similar materials, abnormal pressure-relief and stress fluctuations are prone to appear in the loading process, and the main failure modes are the tensile failures and conjugate shear fracturings; 4) Human factors affect a lot during the production procedures of similar material models, thus, in order to increase the accuracy of similar material experiment, we put forward the error sources in the preparation and test processes and try to avoid them.%为提高相似材料模型试验的模拟精度,通过单轴压缩测试了2种不同材料(砂-石膏、砂-水泥-石膏)、不同配比试件的应力-应变特性,分析其力学性能、破坏特征,并探讨了相似材料模型制作及试件测试过程中的误差来源.研究结果表明:1)2种相似材料试件在加载过程中均能表现出良好的弹塑性性质,可针对不同试验岩体进行模拟仿真;2)2种相似材料试件峰后软化段平稳,残余强度稳定;3)由于相似材料体胶结不够充分,原发损伤多,加载过程中易出现异常卸压和应力波动,破坏特征主要以张裂和共轭双剪为主;4)相似材料模型制作过程中,人为因素影响较大,提出了配

  12. In situ stress magnitude and rock strength in the Nankai accretionary complex: a novel approach using paired constraints from downhole data in two wells

    Science.gov (United States)

    Huffman, K. A.; Saffer, D. M.; Dugan, B.

    2016-07-01

    We present a method to simultaneously constrain both far-field horizontal stress magnitudes ( S hmin and S Hmax) and in situ rock unconfined compressive strength (UCS), using geophysical logging data from two boreholes located 70 m apart that access the uppermost accretionary prism of the Nankai subduction zone . The boreholes sample the same sediments and are affected by the same tectonic stress field, but were drilled with different annular pressures, thus providing a unique opportunity to refine estimates of both in situ stress magnitudes and rock strength. We develop a forward model to predict the angular width of compressional wellbore failures (borehole breakouts), and identify combinations of S Hmax and UCS that best match breakout widths observed in resistivity images from the two boreholes. The method requires knowledge of S hmin, which is defined by leak-off tests conducted during drilling. Our results define a normal to strike-slip stress regime from 900 to 1386 m below seafloor, consistent with observations from seismic and core data. Our analysis also suggests that in situ values of UCS are generally slightly lower that commonly assumed on the basis of published empirical relations between UCS and P-wave velocity.

  13. 激发剂对石煤提钒尾渣地聚合物性能与微观结构的影响%Effects of Activator on Compressive Strength and Microstructures of Stone Coal Aciding Vanadium Tailings Based Geopolymer

    Institute of Scientific and Technical Information of China (English)

    胡芳芳; 张一敏; 陈铁军; 包申旭; 刘涛

    2014-01-01

    The effects of different activators on compressive strength and microstructures of stone coal aciding vanadium tailings-based geopolymers were studied. It shows that the effects of activators kinds and amounts on the geopolymers compressive strength of each age is great; the differences of activative effect with different activators kinds is big. It is observed that the optimum amounts of NaOH, KOH andNa2SiO3 are 13%, 18%and 20%, respectively. The compressive strength of stone coal aciding vanadium tailings-based geopolymers is low using NaOH and KOH activators, meanwhile theNa2SiO3 consumption is too much. The activative effect intensiifes when NaOH mixs withNa2SiO3, the compressive strength improves observably. But an excess of NaOH orNa2SiO3 can reduce its compressive strength. When NaOH content is 12% with the mass ratio of NaOH and Na2SiO3 of 1.0, the compressive strength of products reaches the maximum of 28MPa. The microstructures of different alkali-activation geopolymers are analyzed based on XRD, FTIR and SEM. The result can approve that have been a degree of polymerization in the geopolymer with the generation of amorphous material. The kinds of activators have no effect on the state of microscopic structure of geopolymers.%研究了不同激发剂对以石煤提钒尾渣为主要原料制备的地聚合物抗压强度和微观结构的影响。结果表明,激发剂的种类和掺量对地聚合物材料各龄期的抗压强度均有较大影响;不同种类碱激发剂激发效果差异较大,分别存在不同最佳掺量:NaOH为13%,KOH为18%, Na2SiO3为20%。NaOH和KOH纯碱激发剂合成的地聚合物抗压强度较低,Na2SiO3激发剂合成的地聚合物耗碱量大。采用NaOH与Na2SiO3复合激发剂后,显著增大了地聚合物的抗压强度,但过多的NaOH或Na2SiO3均会导致其抗压强度降低,当NaOH掺量为12%,Na2SiO3与NaOH质量比为1.0时,制品28 d抗压强度达到最大值28 MPa。利用XRD、FTIR

  14. Effects of Alkali-activator on Compressive Strength of Casting Dust-fly Ash Based Geopolymer%碱激发剂对铸造粉尘-粉煤灰基地质聚合物抗压强度的影响

    Institute of Scientific and Technical Information of China (English)

    王敏; 吴勇生; 李如燕; 孙可伟

    2013-01-01

    以粉煤灰和铸造粉尘为主要原料,以KOH、NaOH、Na2SiO3、K2SiO3和水玻璃为碱激发剂,制备地质聚合物.研究了不同激发剂对铸造粉尘-粉煤灰基地质聚合物抗压强度的影响.结果表明:不同浓度的NaOH和KOH溶液的激发效果较差,制备的铸造粉尘-粉煤灰基地质聚合物的抗压强度较低.NaOH和KOH溶液与K2SiO3溶液混配复合激发剂可提高铸造粉尘-粉煤灰基地质聚合物的抗压强度.水玻璃溶液激发效果最好,随着水玻璃溶液模数的增加,铸造粉尘-粉煤灰基地质聚合物的抗压强度逐渐提高;当水玻璃模数为1.2时,铸造粉尘基地质聚合物28 d抗压强度达到最大,为21.4 MPa;继续增大水玻璃模数,铸造粉尘-粉煤灰基地质聚合物28 d抗压强度趋于下降.%Casting dust-fly ash based geopolymer has been synthesized by using fly ash and casting dust as main raw materials,KOH,NaOH,Na2SiO3,K2SiO3 and water glass as activators.The effects of different alkali-activators on compressive strength of casting dust-fly ash based geopolymer were studied.The study showed that the activation effects of NaOH and KOH solution with different concentration are weak and the compressive strength of casting dust-fly ash based geopolymer is low.The activation effects are enhanced when NaOH or KOH solution mixes with K2SiO3 solution,and the compressive strength improves too.The water glass solution shows the best activation effect,the compressive strength of casting dust-fly ash based geopolymer increases with increasing modulus of water glass solution.When the modulus of water glass solution is 1.2,the 28 d compressive strength is 21.4 MPa.The compressive strength of geopolymer decreases with the increase of the modulus when it is greater than 1.2.

  15. Finite-difference interblock transmissivity for unconfined aquifers and for aquifers having smoothly varying transmissivity

    Science.gov (United States)

    Goode, D.J.; Appel, C.A.

    1992-01-01

    More accurate alternatives to the widely used harmonic mean interblock transmissivity are proposed for block-centered finite-difference models of ground-water flow in unconfined aquifers and in aquifers having smoothly varying transmissivity. The harmonic mean is the exact interblock transmissivity for steady-state one-dimensional flow with no recharge if the transmissivity is assumed to be spatially uniform over each finite-difference block, changing abruptly at the block interface. However, the harmonic mean may be inferior to other means if transmissivity varies in a continuous or smooth manner between nodes. Alternative interblock transmissivity functions are analytically derived for the case of steady-state one-dimensional flow with no recharge. The second author has previously derived the exact interblock transmissivity, the logarithmic mean, for one-dimensional flow when transmissivity is a linear function of distance in the direction of flow. We show that the logarithmic mean transmissivity is also exact for uniform flow parallel to the direction of changing transmissivity in a two- or three-dimensional model, regardless of grid orientation relative to the flow vector. For the case of horizontal flow in a homogeneous unconfined or water-table aquifer with a horizontal bottom and with areally distributed recharge, the exact interblock transmissivity is the unweighted arithmetic mean of transmissivity at the nodes. This mean also exhibits no grid-orientation effect for unidirectional flow in a two-dimensional model. For horizontal flow in an unconfined aquifer with no recharge where hydraulic conductivity is a linear function of distance in the direction of flow the exact interblock transmissivity is the product of the arithmetic mean saturated thickness and the logarithmic mean hydraulic conductivity. For several hypothetical two- and three-dimensional cases with smoothly varying transmissivity or hydraulic conductivity, the harmonic mean is shown to yield

  16. Analysis of the Influential Factors of the Slump and the Discreteness of the Compressive Strength of Site-Mixed Concrete%现场混凝土坍落度和抗压强度离散性的影响因素分析

    Institute of Scientific and Technical Information of China (English)

    曹文明; 邢振贤; 马荣佳

    2012-01-01

    By the orthogonal design method,a test study is made,in the paper,of the ratio of water to binder,sand ratio,the temperature of the mixed materials,the curing temperature,and the sand moisture,all of which are referred to as the control factors affecting the slump and compressive strength of the concrete of CFG piles.These control factors are quantitatively analyzed,by the range analysis and variance analysis methods,to find out to what extent these factors will affect the the slump and compressive strength of the site-mixed concrete.The research shows that sand moisture is the main influential factor that affects the slump of the site-mixed concrete while the temperature of the concrete that has just been turned out and the environmental temperature significantly influence the discreteness of the compressive strength of the concrete of CFG piles.%运用正交设计法对影响CFG桩混凝土坍落度和抗压强度的水胶比、砂率、拌合物温度、养护温度以及砂子含水率等控制因素进行了试验研究,采用极差分析和方差分析方法定量分析了这几个主要控制因素对搅拌站现场混凝土拌合物坍落度和抗压强度的影响程度。研究发现,砂子含水率是影响现场混凝土坍落度的主要因素,拌合物的出机温度和环境温度成为CFG桩现场混凝土抗压强度离散性的显著影响因素。

  17. EXPERIMENTAL STUDY ON REALKALIZATION REPAIR OF CONCRETE COMPRESSIVE STRENGTH AFTER HIGH-TEMPERATURE BASED ON MICROSTRUCTURE ANALYSIS%基于微观结构分析的再碱化对高温后混凝土抗压强度修复试验研究

    Institute of Scientific and Technical Information of China (English)

    熊焱; 吴迪; 刘赋安

    2013-01-01

    该文对高温作用经再碱化修复后的混凝土进行了压汞测孔试验及抗压强度试验,研究了混凝土微观结构与其宏观力学性能之间的关系.试验结果表明,高温后混凝土的抗压强随着温度升高呈现下降的趋势,混凝土的微观结构变差,粗大孔明显增多;经再碱化修复后,混凝土的抗压强度得到一定程度的提高,微观结构得到明显改善,粗大孔明显减少.混凝土微观结构的变化与其宏观力学性能一致,说明了再碱化可以一定程度的修复高温作用后混凝土的力学性能,同时改善混凝土的耐久性能.%The experiments of mercury intrusion porosimetry and compressive strength of concrete after high temperature are performed,and the relationship between microstructure and mechanical properties of concrete is investigated.The results show that the compressive strength of concrete decreased with the temperature increased,the microstructure of concrete becomes worse,and the macro porous has evident increase.After realkalization,the compressive strength of concrete is improved to some extent,the microstructure is improved obviously,and the macro porous is decreased significantly.The variation of microstructure in concrete is in consistence with the change of mechanical properties,which draws a conclusion that the realkalization repairing can recover the mechanical property and the durability of concrete after high temperature.

  18. Strength Modeling of High-Strength Concrete with Hybrid Fibre Reinforcement

    Directory of Open Access Journals (Sweden)

    A. Ravichandran

    2009-01-01

    Full Text Available The low tensile strength and limited ductility, the unavoidable deficiency, of concrete can be overcome by the addition of fibres. High strength concrete (HSC of 60 MPa containing hybrid fibres, combination of steel and polyolefin fibres, at different volume fraction of 0.5, 1.0, 1.5 and 2.0% were compared in terms of compressive, splitting tensile strength and flexural properties with HSC containing no fibres. Test results showed that the fibres when used in hybrid form could result in enhanced flexural toughness compared to steel fibre reinforced concrete [HSFRC]. The compressive strength of the fibre-reinforced concrete reached maximum at 1.5% volume fractions and the splitting tensile strength and modulus of rupture improved with increasing volume fraction. Strength models were established to predict the compressive and splitting tensile strength and modulus of rupture of the fibre-reinforced concrete. The models give prediction matching the measurements.

  19. Dynamic Strength of Materials

    Science.gov (United States)

    Chhabildas, Lalit

    2011-06-01

    Historically when shock loading techniques became accessible in the early fifties it was assumed that materials behave like fluids implying that materials cannot support any shear stresses. Early and careful investigation in the sixties by G. R. Fowles in aluminum indicated otherwise. When he compared his Hugoniot compression measurements to hydrostatic pressure compression measurements in the pressure volume plane he noticed that the shock data lay above the hydrostatic compression curve - which laid the ground work for what is the basis for elastic-plastic theories that exist today. In this talk, a brief historical perspective on strength measurements in materials will be discussed including how time-resolved techniques have played a role in allowing estimates of the strength of materials at over Mbar stress. This is crucial especially at high stresses since we are determining values that are small compared to the loading stress. Even though we have made considerable progress in our understanding of materials, there are still many anomalies and unanswered questions. Some of these anomalies are fertile grounds for further and future research and will be mentioned.

  20. Influence of Compacting Rate on the Properties of Compressed Earth Blocks

    Directory of Open Access Journals (Sweden)

    Humphrey Danso

    2016-01-01

    Full Text Available Compaction of blocks contributes significantly to the strength properties of compressed earth blocks. This paper investigates the influence of compacting rates on the properties of compressed earth blocks. Experiments were conducted to determine the density, compressive strength, splitting tensile strength, and erosion properties of compressed earth blocks produced with different rates of compacting speed. The study concludes that although the low rate of compaction achieved slightly better performance characteristics, there is no statistically significant difference between the soil blocks produced with low compacting rate and high compacting rate. The study demonstrates that there is not much influence on the properties of compressed earth blocks produced with low and high compacting rates. It was further found that there are strong linear correlations between the compressive strength test and density, and density and the erosion. However, a weak linear correlation was found between tensile strength and compressive strength, and tensile strength and density.

  1. The influence of low-permeability cap on capillary pressure during pumping in unconfined aquifer

    Institute of Scientific and Technical Information of China (English)

    黄辉; 钱家忠; 匡星星; 陈冰宇; 马雷; 吴亚楠

    2013-01-01

    The pumping test in an unconfined aquifer with and without a low-permeability soil was studied experimentally to reveal the influence of the negative air pressure (NP) caused by the upper layer on the water content(w), the water pressure(Pw), as well as on the capillary pressure(Pc). The study demonstrates that the NP generated in the vadose zone during pumping in the capper aquifer has a significant influence onw,wP andPc. ThecP obtained from the capped aquifer is smaller than that without the upper layer. After the NP reaches a peak, the influence of the NP onPc is gradually declined as the air inflows through the upper layer which makes the NP gradually return to zero. When the air pressure returns to the atmospheric pressure,Pc in the vadose zone is only correlated withPw, the same as the case with no upper layer.

  2. Injection of Zero Valent Iron into an Unconfined Aquifer Using Shear-Thinning Fluids

    Energy Technology Data Exchange (ETDEWEB)

    Truex, Michael J.; Vermeul, Vincent R.; Mendoza, Donaldo P.; Fritz, Brad G.; Mackley, Rob D.; Oostrom, Martinus; Wietsma, Thomas W.; Macbeth, Tamzen

    2011-02-18

    Approximately 190 kg of two micron-diameter zero-valent iron (ZVI) particles were injected into a test zone in the top two meters of an unconfined aquifer within a trichloroethene (TCE) source area. A shear-thinning fluid was used to enhance ZVI delivery in the subsurface to a radial distance of up to four meters from a single injection well. The ZVI particles were mixed in-line with the injection water, shear-thinning fluid, and a low concentration of surfactant. ZVI was observed at each of the seven monitoring wells within the targeted radius of influence during injection. Additionally, all wells within the targeted zone showed low TCE concentrations and primarily dechlorination products present 44 days after injection. These results suggest that ZVI can be directly injected into an aquifer with shear-thinning fluids and extends the applicability of ZVI to situations where other emplacement methods may not be viable.

  3. A study of compressibility and compactibility of directly compressible tableting materials containing tramadol hydrochloride.

    Science.gov (United States)

    Mužíková, Jitka; Kubíčková, Alena

    2016-09-01

    The paper evaluates and compares the compressibility and compactibility of directly compressible tableting materials for the preparation of hydrophilic gel matrix tablets containing tramadol hydrochloride and the coprocessed dry binders Prosolv® SMCC 90 and Disintequik™ MCC 25. The selected types of hypromellose are Methocel™ Premium K4M and Methocel™ Premium K100M in 30 and 50 % concentrations, the lubricant being magnesium stearate in a 1 % concentration. Compressibility is evaluated by means of the energy profile of compression process and compactibility by the tensile strength of tablets. The values of total energy of compression and plasticity were higher in the tableting materials containing Prosolv® SMCC 90 than in those containing Disintequik™ MCC 25. Tramadol slightly decreased the values of total energy of compression and plasticity. Tableting materials containing Prosolv® SMCC 90 yielded stronger tablets. Tramadol decreased the strength of tablets from both coprocessed dry binders.

  4. A study of compressibility and compactibility of directly compressible tableting materials containing tramadol hydrochloride

    Directory of Open Access Journals (Sweden)

    Mužíková Jitka

    2016-09-01

    Full Text Available The paper evaluates and compares the compressibility and compactibility of directly compressible tableting materials for the preparation of hydrophilic gel matrix tablets containing tramadol hydrochloride and the coprocessed dry binders Prosolv® SMCC 90 and Disintequik™ MCC 25. The selected types of hypromellose are Methocel™ Premium K4M and Methocel™ Premium K100M in 30 and 50 % concentrations, the lubricant being magnesium stearate in a 1 % concentration. Compressibility is evaluated by means of the energy profile of compression process and compactibility by the tensile strength of tablets. The values of total energy of compression and plasticity were higher in the tableting materials containing Prosolv® SMCC 90 than in those containing Disintequik™ MCC 25. Tramadol slightly decreased the values of total energy of compression and plasticity. Tableting materials containing Prosolv® SMCC 90 yielded stronger tablets. Tramadol decreased the strength of tablets from both coprocessed dry binders.

  5. A study of compressibility and compactibility of directly compressible tableting materials containing tramadol hydrochloride.

    Science.gov (United States)

    Mužíková, Jitka; Kubíčková, Alena

    2016-09-01

    The paper evaluates and compares the compressibility and compactibility of directly compressible tableting materials for the preparation of hydrophilic gel matrix tablets containing tramadol hydrochloride and the coprocessed dry binders Prosolv® SMCC 90 and Disintequik™ MCC 25. The selected types of hypromellose are Methocel™ Premium K4M and Methocel™ Premium K100M in 30 and 50 % concentrations, the lubricant being magnesium stearate in a 1 % concentration. Compressibility is evaluated by means of the energy profile of compression process and compactibility by the tensile strength of tablets. The values of total energy of compression and plasticity were higher in the tableting materials containing Prosolv® SMCC 90 than in those containing Disintequik™ MCC 25. Tramadol slightly decreased the values of total energy of compression and plasticity. Tableting materials containing Prosolv® SMCC 90 yielded stronger tablets. Tramadol decreased the strength of tablets from both coprocessed dry binders. PMID:27383891

  6. Leachability and strength of kaolin stabilized with cement and rubber

    Directory of Open Access Journals (Sweden)

    Meei-Hoan Ho

    2011-07-01

    Full Text Available Yearly, the disposal of used tyres is a major environmental problem for countries all over the world. This causes environmental hazards such as uncontrolled fire, consume landfill space, breeding ground for mosquitoes and contaminating the soil and vegetation. Hence, urgent steps were identified to produce new methods of recycling the waste tyres to solve this hazard. This study reviews the feasibility of using waste tyres in the form of rubber chips with cement to stabilize soft clay and the effect to the environment. The focus of this study was mainly the strength and leachability characteristics of kaolin as base clay, admixed with cement as the binder and rubber chips as an additive. Leaching test is used to evaluate the performance of cementitious materials for stabilization and solidification (S & S of hazardous materials such as waste or contaminated soil. In this study, cylindrical stabilized clay specimens were prepared with various rubber chips contents and cement, and then aged for 28 days. Cylindrical specimens were then subjected to unconfined compressive strength test (using Geocomp LoadTrac II and the specimens were later dried in oven at 105° before tested for leaching tests. These leaching methods are Acid Neutralization Capacity Test (ANC and Synthetic Precipitation Leaching Procedure (SPLP. The solidified samples were checked on six different heavy metals, namely copper, chromium, cadmium, arsenic, zinc and plumbum. Analysis was carried out by relating the effects of 0, 2 or 4 % cement as well as 0, 5, 10 and 15 % rubber chips addition to the base clay and its leachability. As observed, the curing of specimen for 28 days was in a range of 66.24 to 249.4 kPa. Specimen with 4 % cement is able to produce ANC9 of about 0.13 meq HNO3/g specimen. However specimen with 0 % and 2 % cement for different rubberchips content shows that the specimen do not have the capacity to neutralize acid at pH 9. Therefore, more cement (> 4 % is

  7. Internal stress and yield strength of copper films on substrates

    Institute of Scientific and Technical Information of China (English)

    Zhang Jian-Min; Zhang Yan; Xu Ke-Wei

    2005-01-01

    Internal stress and yield strength of pure copper films on substrates were characterized by x-ray diffraction and thermal-cycle substrate curvature methods. The internal stress was of tension, and decreased with increasing workinggas (argon) pressure and increased with increasing film thickness. Tensile yield strength of copper films on steel substrate was reciprocal to the film thickness. Similarly, the compressive yield strength depended strongly on the film thickness:the thinner the film thickness, the larger the compressive yield strength.

  8. STRENGTH OF NANOMODIFIED HIGH-STRENGTH LIGHTWEIGHT CONCRETES

    Directory of Open Access Journals (Sweden)

    NOZEMTСEV Alexandr Sergeevich

    2013-02-01

    Full Text Available The paper presents the results of research aimed at development of nanomodified high-strength lightweight concrete for construction. The developed concretes are of low average density and high ultimate compressive strength. It is shown that to produce this type of concrete one need to use hollow glass and aluminosilicate microspheres. To increase the durability of adhesion between cement stone and fine filler the authors offer to use complex nanodimensinal modifier based on iron hydroxide sol and silica sol as a surface nanomodifier for hollow microspheres. It is hypothesized that the proposed modifier has complex effect on the activity of the cement hydration and, at the same time increases bond strength between filler and cement-mineral matrix. The compositions for energy-efficient nanomodified high-strength lightweight concrete which density is 1300…1500 kg/m³ and compressive strength is 40…65 MPa have been developed. The approaches to the design of high-strength lightweight concrete with density of less than 2000 kg/m³ are formulated. It is noted that the proposed concretes possess dense homogeneous structure and moderate mobility. Thus, they allow processing by vibration during production. The economic and practical implications for realization of high-strength lightweight concrete in industrial production have been justified.

  9. 再生混凝土块体替代率对混凝土立方体抗压强度的影响%An Experimental Study on Influence of Replacement Rate of Recycled Concrete Block Contents on the Cube Compressive Strength of Recycled Aggregate Concrete

    Institute of Scientific and Technical Information of China (English)

    俞鑫; 王振波; 孙焱焱

    2012-01-01

    废弃混凝土破碎成小块体,将替代率分别为0%,20%,和30%的再生混凝土块体和现浇混凝土混合放入200 mm×200 mm×200 mm的立方体试模中,制成再生混凝土混合试块。对再生混凝土混合试块进行立方体抗压试验,测出不同块体替代率下混凝土试块的抗压强度,试验结果表明随着再生混凝土块体替代率的增加,再生混凝土混合试块强度降低。%Broken waste concrete into small blocks, mixing with the nature concrete into the 200*200*200 cube experimental mold , made from recycled concrete mixed blocks, the rate of substitution of recycled con- crete block is 0%, 20% and 30%. Through the cube compressive test, measured compressive strength of con- crete test block under different substitution rate, the results indicated that with increased replacement rate of recycled concrete blocks, try recycled concrete mixing reduced, the strength of the recycled concrete mixed blocks is reduced.

  10. 锂渣复合粉煤灰高性能混凝土早期抗压强度影响因素的比较分析%The Comparative Analysis of Influence on the Early Compressive strength of lithium Slag Compound Fly Ash High Performance Concrete

    Institute of Scientific and Technical Information of China (English)

    周海雷; 杨恒阳; 努尔开力·依孜特罗甫; 侍克斌

    2012-01-01

    Lithium slag compound fly ash high performance concrete was made by the orthogonal experiment design method, the preparation of the use of poor analysis and variance analysis method to analyze the impact that the water-binder ratio, lithium slag mix content and the fly ash for lithium slag compound fly ash of high performance concrete compressive strength of the early. Lithium slag on lithium slag compound fly ash high performance concrete compressive strength has significance effects Dmng early. Dmng analysis of the poor, poor relative difference degree was introduced the concept.%运用正交试验设计的方法配制锂渣复合粉煤灰高性能混凝土,运用极差分析和方差分析的方法分析了水胶比、锂渣掺量和粉煤灰掺量对锂渣复合粉煤灰高性能混凝土的早期抗压强度的影响,得出锂渣较粉煤灰对锂渣复合粉煤灰高性能混凝土早期抗压强度影响显著.在进行极差分析时,引入了极差相对差异度这一概念.

  11. Compression Enhanced Shear Yield Stress of Electrorheological Fluid

    Institute of Scientific and Technical Information of China (English)

    ZHANG Min-Liang; TIAN Yu; JIANG Ji-Le; ZHU Xu-Li; MENG Yong-Gang; WEN Shi-Zhu

    2009-01-01

    @@ Shear tests of an electrorheological fluid with pre-applied electric field and compression along the field direction are carried out. The results show that pre-compressions can increase the shear yield stress up to ten times. Under the same external electric field strength, a higher compressive strain corresponds to a larger shear yield stress enhancement but with slight current density decrease, which shows that the particle interaction potentials are not increased by compressions but the compression-induced chain aggregation dominates the shear yield stress improvement. This pre-compression technique might be useful [or developing high performance flexible ER or magnetorheological couplings.

  12. Effect of curing temperature and curing time on compressive strength of fly ash geopolymer concrete%养护温度及时间对粉煤灰基地质聚合物混凝土强度发展的影响

    Institute of Scientific and Technical Information of China (English)

    谢子令; 李显

    2014-01-01

    Using sand and crushed rock as aggregate,fly ash and some silica fume as precursor,sodium hydroxide and water glass as ac-tivator,a geopolymer concrete was produced.The effect of curing temperature and age times on the compressive strength of the fly ash geopolymer concrete were studied.The results show that the compressive strength of the geopolymer concrete increases lineally with curing temperature in the range of 20℃to 80℃.When the curing temperature is further increased up to 100℃,a 3.1%decrease in compressive strength will be observed as compared to that cured at 80℃.This is due to high temperature curing induced microcracks formed on the sur-face of the samples.As well as the curing time concerned,the compressive strength increased at initial curing periods and gradually tended to level off at later period.The tendency can been captured by an exponential decay function.Further analysis revealed that increasing initial curing temperature can enhanced the geopolymerization process,and then achieved high compression strength in a short time as compared to the samples curing at ambient temperature.%以砂、碎石为骨料,粉煤灰及少量的硅灰为胶凝材料,水玻璃、氢氧化钠为激发剂制备了地质聚合物混凝土,测试了不同养护温度及时间下粉煤灰基地质聚合物混凝土的抗压强度,旨在揭示养护温度及龄期对粉煤灰基地质聚合物混凝土强度发展的影响规律。结果表明:在20~80℃之间,提高养护温度可以提高粉煤灰基地质聚合物混凝土的抗压强度,并呈现线性增长的关系,进一步提高养护温度会导致试样表面微裂纹的产生,进而导致抗压强度有所下降;地质聚合物混凝土的抗压强度随龄期的增加而增大,并趋于稳定,该趋势可用指数函数加以描述;早期的高温养护会加速聚合化反应速度,降低聚合化反应时间,即高温短时养护可达到低温长时养护的效果。

  13. A Numerical Stress-strain Response Model of All Grades of Concretes under Uniaxial Compression

    Institute of Scientific and Technical Information of China (English)

    WANG Yongwei; PU Xincheng; WANG Zhijun

    2006-01-01

    An important problem facing stress-strain response modeling of concrete is the complexity of the compressive strength grades. 21 groups of specimens with different cubic compressive strength (56.3-164.9 MPa) have been numerically analyzed. Using only the compressive strength, a stress-strain response model of different concrete grade was established. The numerical simulation model not only quantitatively reproduces the relationship of uniaxial compressive strength, peak value stress and cubic compressive strength, but realizes the consistence of the ascending branch of stress-strain curves with different strength grades by introducing the correction coefficient k. The results indicate k increases gradually from 0 to approximate 1 with the increase of the compressive strength, corresponding to the transition from the paracurve to straight line branch in stress-strain curves. When k is 0, the model is identical to the Hognestad equation. A good agreement with the experiment data was obtained.

  14. Small Barriers Trigger Liftoff of Unconfined Dilute Heated Laboratory Density Currents

    Science.gov (United States)

    Fauria, K.; Andrews, B. J.; Manga, M.

    2015-12-01

    Dilute pyroclastic density currents (PDCs) are hot, turbulent, particle-laden flows that propagate because they are denser than air. PDCs can traverse tens to hundreds of kilometers and surmount ridges 100s of m tall, yet the effects of complex topography on PDC liftoff and runout distance are uncertain. Here we used scaled laboratory experiments to explore how barriers affect dilute density current dynamics and the occurrence of liftoff. We created dilute density currents by heating and suspending 20 μm diameter talc in air in an 8.5 x 6.1 x 2.6 m tank. We scaled the currents with respect to Froude, densimetric and thermal Richardson, particle Stokes and Settling numbers such that they were dynamically similar to natural PDCs. While currents were fully turbulent, their Reynolds numbers were not as high as those for natural PDCs. We performed the first set of experiments in a laterally unconfined volume, used laser sheets to illuminate the currents, measured bulk sedimentation rates down the current centerlines, and positioned four to twenty-four cm tall ridge-like barriers in the path of the currents. We found that relatively small barriers (~ half the current height) caused PDC liftoff. By comparison, conservation of kinetic and potential energy predicts that incompressible density currents are able to surmount barriers twice their height. Furthermore, we observed increased sedimentation immediately upstream of barriers and conclude that small barriers initiated buoyancy reversal through a combination of increased air entrainment and sedimentation. We conducted a second set of experiments with the same thermal scaling and mass flux rates but where the currents were laterally confined within a 0.6 m wide channel. We found that small barriers also triggered liftoff of confined currents, but that the body of these currents reattached after liftoff. Those results suggest that lateral confinement inhibits buoyancy reversal by limiting the surface area of the current

  15. Uniaxial Compressive Properties of Ultra High Toughness Cementitious Composite

    Institute of Scientific and Technical Information of China (English)

    CAI Xiangrong; XU Shilang

    2011-01-01

    Uniaxial compression tests were conducted to characterize the main compressive performance of ultra high toughness cementitious composite(UHTCC)in terms of strength and toughness and to obtain its stress-strain relationships.The compressive strength investigated ranges from 30 MPa to 60 MPa.Complete stress-strain curves were directly obtained,and the strength indexes,including uniaxial compressive strength,compressive strain at peak stress,elastic modulus and Poisson's ratio,were calculated.The comparisons between UHTCC and matrix were also carried out to understand the fiber effect on the compressive strength indexes.Three dimensionless toughness indexes were calculated,which either represent its relative improvement in energy absorption capacity because of fiber addition or provide an indication of its behavior relative to a rigid-plastic material.Moreover,two new toughness indexes,which were named as post-crack deformation energy and equivalent compressive strength,were proposed and calculated with the aim at linking up the compressive toughness of UHTCC with the existing design concept of concrete.The failure mode was also given.The study production provides material characteristics for the practical engineering application of UHTCC.

  16. 基于结合强度的金属塑料复合材料压制成型%Compression Molding of Metal-Plastic Composite Based on Bonding Strength

    Institute of Scientific and Technical Information of China (English)

    黄殿凯; 徐健伟; 李进; 骆志高

    2013-01-01

    利用聚醚砜(PES)与金属间结合性能高的特点,采用模压成型的工艺,制备了一种PES/金属复合材料。通过划痕实验对材料的结合性能进行了研究,并利用整个划刻过程的声发射信号的监测来确定涂层被破坏时的临界载荷值。结果表明,采用模压成型法能制得结合性能优良的复合材料。%A kind of polyethersulfone(PES)/metal composite was made by compression molding process based on good bonding property between PES and metal. The bonding ability of composite material was discussed through scratch test and the critical load value which damaged the coating was obtained by monitoring the acoustic emission signal during scratch test. The results show that the composite which has excellent bonding property can be made by compression molding process.

  17. Establishment of earth tides effect on water level fluctuations in an unconfined hard rock aquifer using spectral analysis

    CERN Document Server

    Maréchal, Jean-Christophe; Ahmed, Shakeel; Lachassagne, Patrick

    2010-01-01

    Short-interval water level measurements using automatic water level recorder in a deep well in an unconfined crystalline rock aquifer at the campus of NGRI, near Hyderabad shows a cyclic fluctuation in the water levels. The observed values clearly show the principal trend due to rainfall recharge. Spectral analysis was carried out to evaluate correlation of the cyclic fluctuation to the synthetic earth tides as well as groundwater withdrawal time series in the surrounding. It was found that these fluctuations have considerably high correlation with earth tides whereas groundwater pumping does not show any significant correlation with water table fluctuations. It is concluded that earth tides cause the fluctuation in the water table. These fluctuations were hitherto unobserved during manual observations made over larger time intervals. It indicates that the unconfined aquifer is characterised by a low porosity.

  18. Fractal image compression

    OpenAIRE

    Žemlo, Gražina

    2004-01-01

    One of the images compression methods – fractal image compression is analyzed in the work. After work carried out, it is possible to state, that selecting parameters of method of fractal compression depends on user’s demands.

  19. Unconfined, melt edge electrospinning from multiple, spontaneous, self-organized polymer jets

    Science.gov (United States)

    Wang, Qingqing; Curtis, Colin K.; Muthuraman Thoppey, Nagarajan; Bochinski, Jason R.; Gorga, Russell E.; Clarke, Laura I.

    2014-12-01

    Commercial grade polyethylene is melt electrospun from a thin film of unconfined molten polymer on a heated, electrically-grounded plate. Under the influence of an applied electric field, the melt spontaneously forms fingering perturbations at the plate edge which then evolve into emitting fiber-forming jets. Jet-to-jet spacing (˜5 mm), which is dependent on the applied voltage amplitude, is in agreement with estimates from a simple theoretical treatment. The broad applicability of the approach is verified by spinning a second polymer—polycaprolactone. In both cases, the fabricated fibers are similar in quality to those obtained under needle melt electrospinning; however for this method, there are no nozzles to clog and an enhanced production rate up to 80 mg min-1 is achieved from approximately 20-25 simultaneous parallel jets. The process of jet formation, effective flow rates, cone-jet diameters, as well as limits on jet density and differences with polymer type are compared with theoretical models. This particular approach allows facile, high throughput micro- and nano-fiber formation from a wide variety of thermoplastics and other high viscosity fluids without the use of solvents or the persistent issues of clogging and pumping that hamper traditional methods, resulting in mechanically strong meso-scale fibers highly desirable for industrial applications.

  20. Analysis of an unconfined aquifer subject to asynchronous dual-tide propagation

    Science.gov (United States)

    Rotzoll, K.; El-Kadi, A. I.; Gingerich, S.B.

    2008-01-01

    Most published solutions for aquifer responses to ocean tides focus on the one-sided attenuation of the signal as it propagates inland. However, island aquifers experience periodic forcing from the entire coast, which can lead to integrated effects of different tidal signals, especially on narrow high-permeability islands. In general, studies disregard a potential time lag as the tidal wave sweeps around the island. We present a one-dimensional analytical solution to the ground water flow equation subject to asynchronous and asymmetric oscillating head conditions on opposite boundaries and test it on data from an unconfined volcanic aquifer in Maui. The solution considers sediment-damping effects at the coastline. The response of Maui Aquifers indicate that water table elevations near the center of the aquifer are influenced by a combination of tides from opposite coasts. A better match between the observed ground water head and the theoretical response can be obtained with the proposed dual-tide solution than with single-sided solutions. Hydraulic diffusivity was estimated to be 2.3 ?? 107 m 2/d. This translates into a hydraulic conductivity of 500 m/d, assuming a specific yield of 0.04 and an aquifer thickness of 1.8 km. A numerical experiment confirmed the hydraulic diffusivity value and showed that the y-intercepts of the modal attenuation and phase differences estimated by regression can approximate damping factors caused by low-permeability units at the boundary.

  1. Modeling the Impact of Carbon Dioxide Leakage into an Unconfined, Oxidizing Carbonate Aquifer

    Energy Technology Data Exchange (ETDEWEB)

    Bacon, Diana H.; Qafoku, Nikolla; Dai, Zhenxue; Keating, Elizabeth; Brown, Christopher F.

    2016-01-01

    Multiphase, reactive transport modeling was used to identify the mechanisms controlling trace metal release under elevated CO2 conditions from a well-characterized carbonate aquifer. Modeling was conducted for two experimental scenarios: batch experiments to simulate sudden, fast, and short-lived release of CO2 as would occur in the case of well failure during injection, and column experiments to simulate more gradual leaks such as those occurring along undetected faults, fractures, or well linings. Observed and predicted trace metal concentrations are compared to groundwater concentrations from this aquifer to determine the potential for leaking CO2 to adversely impact drinking water quality. Finally, a three-dimensional multiphase flow and reactive-transport simulation of CO2 leakage from an abandoned wellbore into a generalized model of the shallow, unconfined portion of the aquifer is used to determine potential impacts on groundwater quality. As a measure of adverse impacts on groundwater quality, both the EPA’s MCL limits and the maximum trace metal concentration observed in the aquifer were used as threshold values.

  2. EXPERIMENTAL STUDY OF AIRFLOW INDUCED BY PUMPING TESTS IN UNCONFINED AQUIFER WITH LOW-PERMEABILITY CAP

    Institute of Scientific and Technical Information of China (English)

    HUANG Hui; QIAN Jia-zhong; KUANG Xing-xing; CHEN Zhou; LI Ru-zhong

    2012-01-01

    The airflow in unsaturated soils is an issue of great importance in various fields such as in agricultural,nuclear,environmental engineering.However,up to now,little attention was paid to the generation of the airflow induced by a pumping test in an unconfined aquifer with a low-permeability cap and its influence on the pumping test.In this paper,pumping tests were carried out experimentally in the aquifer with a low-permeability cap in ordcr to study the influence of the airflow induced by the pumping on the drawdown of the tests.It is shown that:(1) there is an airflow with negative pressure generated by the pumping tests,(2) the Negative air Pressure (NP) is increased with the pumping rate but decreased with the radial distance,and (3) the NP also changes with the initial water table.The results provide a good basis for further theoretical study of the airflow induced by pumping.

  3. Compression limits in cascaded quadratic soliton compression

    DEFF Research Database (Denmark)

    Bache, Morten; Bang, Ole; Krolikowski, Wieslaw;

    2008-01-01

    Cascaded quadratic soliton compressors generate under optimal conditions few-cycle pulses. Using theory and numerical simulations in a nonlinear crystal suitable for high-energy pulse compression, we address the limits to the compression quality and efficiency.......Cascaded quadratic soliton compressors generate under optimal conditions few-cycle pulses. Using theory and numerical simulations in a nonlinear crystal suitable for high-energy pulse compression, we address the limits to the compression quality and efficiency....

  4. Satellite data compression

    CERN Document Server

    Huang, Bormin

    2011-01-01

    Satellite Data Compression covers recent progress in compression techniques for multispectral, hyperspectral and ultra spectral data. A survey of recent advances in the fields of satellite communications, remote sensing and geographical information systems is included. Satellite Data Compression, contributed by leaders in this field, is the first book available on satellite data compression. It covers onboard compression methodology and hardware developments in several space agencies. Case studies are presented on recent advances in satellite data compression techniques via various prediction-

  5. 再生细骨料湿度状态及掺量对混凝土工作性及抗压强度的影响%Influence of the moisture states and content of recycled fine aggregate on the workability and compressive strength of concrete

    Institute of Scientific and Technical Information of China (English)

    陈远远; 季韬; 江其东; 梁咏宁

    2013-01-01

    The total water-cement ratio of recycled fine aggregate concrete was kept the same.The moisture states (namely air-dried (AD),oven-dried (OD) and saturated surface-dried (SSD)states) and content of recycled fine aggregate were varied.The initial slump and the slump loss,the 3,7 and 28 d compressive strengths of recycled fine aggregate concrete were measured.The test results show that,for the same total water-cement ratio,when the recycled fine aggregate content is the same,the initial slump and the slump loss of concrete decrease and the 3,7 and 28 d compressive strengths of recycled fine aggregate concrete increase with the increase of the moisture of recycled fine aggregate from oven-dried,air-dried to saturated surface-dried states.For the same moisture state,the initial slump increases,the slump loss decreases and the 3,7 and 28 d compressive strengths of recycled fine aggregate concrete decrease with the increase of recycled fine aggregate content.%保持再生细骨料混凝土的总水灰比一致,变化再生细骨料的湿度状态(气干、烘干和饱和面干)及掺量,测出新拌再生细骨料混凝土初始坍落度和坍落度损失,以及3、7和28 d再生细骨料混凝土的抗压强度.研究结果表明:在总水灰比不变的情况下,当再生细骨料掺量一定时,随着其湿度状态从烘干到气干再到饱和面干的变化,混凝土的初始坍落度与坍落度损失减小,混凝土3、7和28 d抗压强度增大;当再生细骨料保持任一湿度状态时,随着其在混凝土中掺量的增大,混凝土的初始坍落度增大,坍落度损失减小,混凝土3、7和28 d抗压强度减小.

  6. 信息动态%Size Effect on Strength of Ultra-high Strength Concrete RPC

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    Reactive Powder Concrete (RPC)is a new kind of ultra-high strength cement based composite with excellent mechanics performance and durability. In order to make RPC used in structural engineering effectively,size effect on strength of the ultra high strength concrete RPC specimen is experimental studied and the mechanism is analyzed in this paper. Test results show that if the 4 cm cube compressive strength is the control strength,conversion coefficients of 10 em cube compressive strength at 150 MPa and 200 MPa grade are 0.81 and 0.76 respectively; conversion coefficients of 10 cm× 10 cm× 30 cm prism compressive strength at 150 MPa and 200 MPa grade are 0.71 and 0. 63 respectively; the size effect conversion coefficient tends to decrease with the increase of control strength, the larger the specimen size, the lower the compressive strength. RPC is a typical brittle material. It extends instability quickly after cracking;damage concentrated in the local area,and therefore appears higher size effect.

  7. Effects of Waste Glass (WG on the Strength Characteristics of Cement Stabilized Expansive Soil

    Directory of Open Access Journals (Sweden)

    I.A.Ikara

    2015-11-01

    Full Text Available The study investigates the suitability of using waste glass (WG as admixture to cement stabilized black cotton soil (BCS for roads, fills and embankment. The soil was classified as A-7-5 and CH according to the American Association of State Highway and Transport Officials (AASHTO and the Unified Soil Classification System (USCS Classifications. Chemical analysis revealed that WG is rich in main oxides such as Silicon Oxide (69.2, Aluminium Oxide (2.29, Iron Oxide (1.57, Calcium Oxide (15.1 and Sodium Oxide (8.75. The soil was stabilized with 0, 2, 4, 6 and 8% cement and 0, 5 10, 15 and 20% WG by weight of the dry soil. Laboratory tests were carried out using the Standard Proctor (SP compactive efforts, California Bearing Ratio (CBR, Unconfined Compressive Strength (UCS, and compaction characteristics tests to evaluate the effectiveness of WG on Ordinary Portland cement (OPC stabilized BCS. The results obtained showed a decrease in the plasticity index (PI, liquid limit (LL, plastic limit (PL and increase Maximum Dry Density (MDD with increase in WG content in all cement proportions used and as compared to the values obtained for the natural soil. The peak 7 days UCS values of 1152kN/m2 was obtained at 8% OPC and 20% WG. Similarly, highest CBR value of 53.8% was obtained at an optimum blend of 8% OPC/20%WG. The results indicate that there is a potential in the use of WG as admixture to strengthen Black cotton soils.

  8. Characterization of Strength of Intact Brittle Rock Considering Confinement-Dependent Failure Processes

    Science.gov (United States)

    Kaiser, Peter K.; Kim, Bo-Hyun

    2015-01-01

    unconfined compression tests (UCS) alone, the confined strength may be underestimated by as much as 50 % (on average). If triaxial data with a limited confinement range (e.g., σ3 ≪ 0.5 UCS due to cell pressure limitations) are used, the confined strength may be overestimated. Therefore, the application of standard data fitting procedures, without consideration of confinement-dependent failure mechanisms, may lead to erroneous intact rock strength parameters when applied to brittle rocks, and consequently, by extrapolation, to correspondingly erroneous rock mass strength parameters. It follows that the strength characteristics of massive rock differ significantly in the direct vicinity of excavation from that which is remote with higher confinement. Therefore, it is recommended to adopt a differentiated approach to obtain intact rock strength parameters for engineering problems at lower confinement (near excavation; e.g., excavation stability assessment or support design), and at elevated confinement (typically, when the confinement exceeds about 10 % of the UCS) as might be encountered in wide pillar cores.

  9. Artificial Neural Network Model for Predicting Compressive

    Directory of Open Access Journals (Sweden)

    Salim T. Yousif

    2013-05-01

    Full Text Available   Compressive strength of concrete is a commonly used criterion in evaluating concrete. Although testing of the compressive strength of concrete specimens is done routinely, it is performed on the 28th day after concrete placement. Therefore, strength estimation of concrete at early time is highly desirable. This study presents the effort in applying neural network-based system identification techniques to predict the compressive strength of concrete based on concrete mix proportions, maximum aggregate size (MAS, and slump of fresh concrete. Back-propagation neural networks model is successively developed, trained, and tested using actual data sets of concrete mix proportions gathered from literature.    The test of the model by un-used data within the range of input parameters shows that the maximum absolute error for model is about 20% and 88% of the output results has absolute errors less than 10%. The parametric study shows that water/cement ratio (w/c is the most significant factor  affecting the output of the model.     The results showed that neural networks has strong potential as a feasible tool for predicting compressive strength of concrete.

  10. Simulation of the transfer of hydrocarbons in unconfined aquifer in tropical zone: the case of benzene

    Science.gov (United States)

    Agnès Kouamé, Amenan; Jaboyedoff, Michel; Derron, Marc-Henri; Kouamé, Kan Jean

    2016-04-01

    Groundwater is the largest global reserves of continental freshwater (Bosca, 2002) and also an important source of drinking water in many parts of the world (Brassington. 2007). However, this resource is today threatened by pollution such as inadequate supply of drinking water services, inaccessibility and / or dilapidated sanitation facilities and excessive use fertilizers, and industrial wastewater and solid waste pesticides (Boubacar, 2010) and the rapid urbanization in great cities (Foster, 2001). Abidjan, the largest city in Côte d'Ivoire is also facing pollution problems such as illegal dumping of waste, waste oil spilled garages, land application of domestic and industrial wastewater, automotive workshops, overexploitation of sand in the Ebrié lagoon, open waste dump of Akouédo and the spill of about 400,000 liters of toxic waste from the ship "Probo Koala" in August 2006. The Abidjan aquifer or the Continental terminal aquifer is the main source of supply drinking water. It is mainly composed of sandy and it is an unconfined aquifer as a whole (Jourda, 1987). According to Gilli and al., (2012), the recharge of unconfined aquifers comes mostly from the infiltration of surface water including rainwater. These waters on their transport in the basement could carry certain pollutants into groundwater. Kouamé (2007) reports a potential groundwater pollution of the "Continental terminal" aquifer in Abidjan. In addition to the cases cited pollution, there has been a proliferation of service stations in the district of Abidjan and this can cause possible pollution. We deemed it necessary to conduct a study on the groundwater pollution of Abidjan by oil in general. We chose benzene to simulate organic pollution in case of accident. To observe the likely evolution of such contaminants in the subsurface, we developed hydrogeological models that couple groundwater flow and benzene transport with FEFLOW software in steady and transient states. The models are composed

  11. 煅烧硅藻土对再生混凝土抗压强度影响研究%Experimental study on the influence of calcined diatomite on compressive strength of recycled concrete

    Institute of Scientific and Technical Information of China (English)

    岳志鑫; 李佰寿

    2015-01-01

    对三组不同掺量的煅烧硅藻土再生细石混凝土与普通细石混凝土做了对比试验,指出三组再生混凝土7d强度随着硅藻土掺量的增加而降低;28 d强度均低于普通混凝土;硅藻土掺量3%的混凝土强度略高,建议煅烧硅藻土掺量控制在3%以内。%Three groups of recycled fine aggregate concrete and normal fine concrete were done contrast test. Recycled concrete 7 d strength grad-ually reduce with the increase of diatomite proportion,research shows that:the three groups of recycled concrete 28 d strength were lower than that of normal concrete,higher for the concrete with 3% proportion. Suggest calcined diatomite proportion control within 3%.

  12. 高温后粗砂岩常规三轴压缩变形与强度特征分析%ANALYSIS OF STRENGTH AND CONVENTIONAL TRIAXIAL COMPRESSION DEFORMATION CHARACTERS OF COARSE SANDSTONE AFTER HIGH TEMPERATURE

    Institute of Scientific and Technical Information of China (English)

    苏承东; 韦四江; 杨玉顺; 秦本东

    2015-01-01

    通过对经历400℃~1000℃高温后的粗砂岩进行常规三轴压缩试验,分析试样变形、强度和破坏特征与温度、围压的关系。结果表明:经历400℃高温后的试样围压高于20 MPa时,试样峰值强度附近出现明显屈服平台,经历超过600℃以上高温的试样均具有明显峰值点,随温度升高试样的塑性减弱脆性增强;400℃以内高温对试样的变形参数影响不大,经历超过400℃以上高温的试样的弹性模量、变形模量和极限应变随围压增加单调增加呈正相关性;试样的弹性模量和变形模量随温度升高单调降低,而峰值应变随温度升高单调增加。高温后试样峰值强度随围压增大而单调增加,符合Coulomb强度准则,综合围压影响系数为6.541;800℃以内高温对试样黏聚力、内摩擦角影响不明显,经历1000℃高温后的试样黏聚力急剧降低,内摩擦角稍有增加;800℃以内高温对粗砂岩具有强化作用,扣除围压影响后试样材料强度与温度呈正相关,超过800℃以上高温使试样强度有所弱化,试样材料强度与温度呈负相关性;高温后试样的试验破坏角和理论破坏角基本一致,高温对试样破坏角影响较小,试验破坏角随围压增加而单调减小,围压对试样破坏角的影响大于温度的影响。%The relationship between rock samples′ deformation,strength and failure characters and temperature, confining pressure was analysed by common conventional triaxial tests of coarse sandstone after high temperature rangeing from 400℃~1 000℃. Obvious yielding plateau nearby peak strength appears when confining pressure was higher than 20 MPa after 400℃,but all samples have obvious peak strength points after 600℃. With the increase of temperature,samples have much weaker plastic characteristic and stronger brittleness. Temperature within 400℃ has little influence on deformation characters of

  13. Study on the Bearing Capacity of High Strength Large Size Equal Angles Steels Under Axially Loaded Compression%高强大规格等边角钢轴压承载力研究

    Institute of Scientific and Technical Information of China (English)

    赵楠; 李正良; 刘红军

    2013-01-01

    进行了19个长细比λ=30~90的Q420 L220 mm×20 mm角钢试件的轴压试验研究.结果表明:此类构件在长细比λ>45时,以弯曲失稳破坏为主;长细比λ≤45时,以弯扭失稳为主.研究了现行钢结构规范中防止局部屈曲宽厚比限值公式和计算弯扭失稳的换算长细比取值公式的适用性.采用逆算单元长度法得到了大规格等边角钢的柱子曲线,研究了此类构件与普通规格等边角钢的差异以及肢厚、肢宽和钢材强度等对柱子曲线的影响.提出了高强大规格等边角钢轴压构件的承载力计算方法.并且研究了高强大规格等边角钢两端偏心受压的柱子曲线,给出了长细比修正系数的建议公式.%The axial compression member test was conducted to investigate the stability performance of these members, including nineteen Q420 L220×20 specimens which slenderness ratio(λ) ranged from 30~90. The test results showed that when slendemess is λ > 45, flexural buckling was observed and when slenderness is λ ≤45, local or flexural-torsion or torsion buckling was observed. The applicability of local buckling wide thickness ratio formula and flexural-torsional buckling conversion slenderness ratio formula was researched. By means of inverse calculation segment length method, the column curve of the large size equal angle was got. The comparison with common size angle and parameter analysis was made. Calculation method of bearing capacity of large size equal angle was given. Two ends eccentric compression column curve was also researched, and a suggestion formula of slenderness ratio correction coefficient was given.

  14. Analytical and numerical analyses of an unconfined aquifer test considering unsaturated zone characteristics

    Science.gov (United States)

    Moench, A.F.

    2008-01-01

    A 7-d, constant rate aquifer test conducted by University of Waterloo researchers at Canadian Forces Base Borden in Ontario, Canada, is useful for advancing understanding of fluid flow processes in response to pumping from an unconfined aquifer. Measured data include not only drawdown in the saturated zone but also volumetric soil moisture measured at various times and distances from the pumped well. Analytical analyses were conducted with the model published in 2001 by Moench and colleagues, which allows for gradual drainage but does not include unsaturated zone characteristics, and the model published in 2006 by Mathias and Butler, which assumes that moisture retention and relative hydraulic conductivity (RHC) in the unsaturated zone are exponential functions of pressure head. Parameters estimated with either model yield good matches between measured and simulated drawdowns in piezometers. Numerical analyses were conducted with two versions of VS2DT: one that uses traditional Brooks and Corey functional relations and one that uses a RHC function introduced in 2001 by Assouline that includes an additional parameter that accounts for soil structure and texture. The analytical model of Mathias and Butler and numerical model of VS2DT with the Assouline model both show that the RHC function must contain a fitting parameter that is different from that used in the moisture retention function. Results show the influence of field-scale heterogeneity and suggest that the RHC at the Borden site declines more rapidly with elevation above the top of the capillary fringe than would be expected if the parameters were to reflect local- or core-scale soil structure and texture.

  15. Estimating specific yield and storage change in an unconfined aquifer using temporal gravity surveys

    Science.gov (United States)

    Gehman, Carter L.; Harry, Dennis L.; Sanford, William E.; Stednick, John D.; Beckman, Nathaniel A.

    2009-04-01

    Two high-precision gravity surveys were conducted to determine groundwater mass changes at a managed groundwater recharge site in northeastern Colorado. Gravity data were collected during pumping and two months after pumping ceased. During pumping, gravity was lower by as much as 46 μGal near the pumping wells and higher by as much as 90 μGal near the recharge ponds in comparison to data collected after pumping had ceased. These differences are attributed to changes in groundwater mass associated with drawdown and infiltration. Inverse modeling of the gravity data indicates a 5.1 × 105 m3 decrease in storage beneath the recharge ponds between the two surveys, which we attribute to dissipation of the groundwater mound created by recharge during pumping. This estimate of the change in groundwater storage is made independently of assumptions of physical properties of the aquifer. Dividing the change in water volume per unit area determined from the gravity modeling by the change in water level measured in wells provides an estimate of specific yield (Sy) of 0.21 ± 0.03, which is within the range of specific yield estimates derived from aquifer tests at the site. Water level changes predicted from the gravity data agree on average to within ±0.45 m of those measured, which we take to be an estimate of the uncertainty in water table depth predictions that can be obtained from gravimetric data in unconfined aquifers. The study covers a 3.2 km2 area, providing a prototype for similar studies at larger scales.

  16. Geochemical Impacts of Leaking CO2 from Subsurface Storage Reservoirs to Unconfined and Confined Aquifers

    Energy Technology Data Exchange (ETDEWEB)

    Qafoku, Nikolla; Brown, Christopher F.; Wang, Guohui; Sullivan, E. C.; Lawter, Amanda R.; Harvey, Omar R.; Bowden, Mark

    2013-04-15

    Experimental research work has been conducted and is undergoing at Pacific Northwest National Laboratory (PNNL) to address a variety of scientific issues related with the potential leaks of the carbon dioxide (CO2) gas from deep storage reservoirs. The main objectives of this work are as follows: • Develop a systematic understanding of how CO2 leakage is likely to influence pertinent geochemical processes (e.g., dissolution/precipitation, sorption/desorption and redox reactions) in the aquifer sediments. • Identify prevailing environmental conditions that would dictate one geochemical outcome over another. • Gather useful information to support site selection, risk assessment, policy-making, and public education efforts associated with geological carbon sequestration. In this report, we present results from experiments conducted at PNNL to address research issues related to the main objectives of this effort. A series of batch and column experiments and solid phase characterization studies (quantitative x-ray diffraction and wet chemical extractions with a concentrated acid) were conducted with representative rocks and sediments from an unconfined, oxidizing carbonate aquifer, i.e., Edwards aquifer in Texas, and a confined aquifer, i.e., the High Plains aquifer in Kansas. These materials were exposed to a CO2 gas stream simulating CO2 gas leaking scenarios, and changes in aqueous phase pH and chemical composition were measured in liquid and effluent samples collected at pre-determined experimental times. Additional research to be conducted during the current fiscal year will further validate these results and will address other important remaining issues. Results from these experimental efforts will provide valuable insights for the development of site-specific, generation III reduced order models. In addition, results will initially serve as input parameters during model calibration runs and, ultimately, will be used to test model predictive capability and

  17. Improving the Dupuit-Forchheimer Approximation for Free Surface Flow in an Unconfined Aquifer

    Science.gov (United States)

    Knight, J. H.

    2003-12-01

    The classical Dupuit-Forchheimer (DF) approximation for groundwater free surface flow in an unconfined aquifer assumes that the vertical component of the seepage velocity is zero. This assumption is expected to be least accurate when there is non-zero accretion at the free surface. The DF approximation leads to a nonlinear diffusion equation satisfied by the height of the free surface. The general principles of integral methods used by Yves Parlange are to assume some simple approximate shape for some unknown function, and then to choose the parameters of this function to satisfy some known integral relation of the flow system. The DF approximation is improved by assuming that the vertical velocity component is zero at the impermeable horizontal base, and increases linearly to its unknown value at the free surface. The well known Guirinsky potential which depends only on the free surface height corresponds to the DF assumptions. Youngs used an integral relation to define a new potential which depends on the free surface height and also on the vertical velocity component, and which for steady flow satisfies a Poisson equation in the horizontal coordinates. We use the assumption of linear variation of vertical velocity to calculate an approximation to the Youngs potential. In some simple flow systems such as the classical dam problem this leads to a simple differential equation for the free surface height, which can be solved numerically. ln some cases simple explicit approximations can be found for quantities of interest, such as the maximum free surface height between drainage ditches.

  18. Effects of hydrogeological properties on sea-derived benzene transport in unconfined coastal aquifers.

    Science.gov (United States)

    Li, Wei-Ci; Ni, Chuen-Fa; Tsai, Chia-Hsing; Wei, Yi-Ming

    2016-05-01

    This paper presents numerical investigations on quantifying the hydrodynamic effects of coastal environment factors, including tidal fluctuations, beach slopes, hydraulic conductivity, and hydraulic gradients on sea-derived benzene transport in unconfined coastal aquifers. A hydrologic transport and mixed geochemical kinetic/equilibrium reactions in saturated-unsaturated media model was used to simulate the spatial and temporal behaviors of the density flow and benzene transport for various hydrogeological conditions. Simulation results indicated that the tidal fluctuations lead to upper saline plumes (USPs) near the groundwater and seawater interfaces. Such local circulation zones trapped the seaward benzene plumes and carried them down in aquifers to the depth depending on the tide amplitudes and beach slopes across the coastal lines. Comparisons based on different tidal fluctuations, beach slopes, hydraulic conductivity, and hydraulic gradient were systematically conducted and quantified. The results indicated that areas with USPs increased with the tidal amplitude and decreased with the increasing beach slope. However, the variation of hydraulic conductivity and hydraulic gradient has relatively small influence on the patterns of flow fields in the study. The increase of the USP depths was linearly correlated with the increase of the tidal amplitudes. The benzene reactive transport simulations revealed that the plume migrations are mainly controlled by the local flow dynamics and constrained in the USP circulation zones. The self-cleaning process of a coastal aquifer is time-consuming, typically requiring double the time of the contamination process that the benzene plume reach the bottom of a USP circulation zone. The presented systematic analysis can provide useful information for rapidly evaluating seaward contaminants along a coastal line with available hydrogeological properties. PMID:27106208

  19. A potential-based inversion of unconfined steady-state hydraulic tomography.

    Science.gov (United States)

    Cardiff, M; Barrash, W; Kitanidis, P K; Malama, B; Revil, A; Straface, S; Rizzo, E

    2009-01-01

    The importance of estimating spatially variable aquifer parameters such as transmissivity is widely recognized for studies in resource evaluation and contaminant transport. A useful approach for mapping such parameters is inverse modeling of data from series of pumping tests, that is, via hydraulic tomography. This inversion of field hydraulic tomographic data requires development of numerical forward models that can accurately represent test conditions while maintaining computational efficiency. One issue this presents is specification of boundary and initial conditions, whose location, type, and value may be poorly constrained. To circumvent this issue when modeling unconfined steady-state pumping tests, we present a strategy that analyzes field data using a potential difference method and that uses dipole pumping tests as the aquifer stimulation. By using our potential difference approach, which is similar to modeling drawdown in confined settings, we remove the need for specifying poorly known boundary condition values and natural source/sink terms within the problem domain. Dipole pumping tests are complementary to this strategy in that they can be more realistically modeled than single-well tests due to their conservative nature, quick achievement of steady state, and the insensitivity of near-field response to far-field boundary conditions. After developing the mathematical theory, our approach is first validated through a synthetic example. We then apply our method to the inversion of data from a field campaign at the Boise Hydrogeophysical Research Site. Results from inversion of nine pumping tests show expected geologic features, and uncertainty bounds indicate that hydraulic conductivity is well constrained within the central site area. PMID:19178572

  20. Characteristics of structural loess strength and preliminary framework for joint strength formula

    Institute of Scientific and Technical Information of China (English)

    Rong-jian LI; Jun-ding LIU; Rui YAN; Wen ZHENG; Sheng-jun SHAO

    2014-01-01

    The strength of structural loess consists of the shear strength and tensile strength. In this study, the stress path, the failure envelope of principal stress ( Kf line), and the strength failure envelope of structurally intact loess and remolded loess were analyzed through three kinds of tests:the tensile strength test, the uniaxial compressive strength test, and the conventional triaxial shear strength test. Then, in order to describe the tensile strength and shear strength of structural loess comprehensively and reasonably, a joint strength formula for structural loess was established. This formula comprehensively considers tensile and shear properties. Studies have shown that the tensile strength exhibits a decreasing trend with increasing water content. When the water content is constant, the tensile strength of the structurally intact soil is greater than that of remolded soil. In the studies, no loss of the originally cured cohesion in the structurally intact soil samples was observed, given that the soil samples did not experience loading disturbance during the uniaxial compressive strength test, meaning there is a high initial structural strength. The results of the conventional triaxial shear strength test show that the water content is correlated with the strength of the structural loess. When the water content is low, the structural properties are strong, and when the water content is high, the structural properties are weak, which means that the water content and the ambient pressure have significant effects on the stress-strain relationship of structural loess. The established joint strength formula of structural loess effectively avoids overestimating the role of soil tensile strength in the traditional theory of Mohr-Coulomb strength.