Sample records for unconfined compressive strength

  1. Effect of Sample Disturbance on Unconfined Compression Strength of Natural Marine Clays

    刘汉龙; 洪振舜


    Quantitatively correcting the unconfined compressive strength for sample disturbance is an important research project in the practice of ocean engineering and geotechnical engineering. In this study, the specimens of undisturbed natural marine clay obtained from the same depth at the same site were deliberately disturbed to different levels. Then, the specimens with different extents of sample disturbance were trimmed for both oedometer tests and unconfined compression tests. The degree of sample disturbance SD is obtained from the oedometer test data. The relationship between the unconfined compressive strength qu and SD is studied for investigating the effect of sample disturbance on qu. It is found that the value of qu decreases linearly with the increase in SD. Then, a simple method of correcting qu for sample disturbance is proposed. Its validity is also verified through analysis of the existing published data.

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

    Ali Ateş


    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.

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

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


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

    Tilak B. Vidya


    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.

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

    MolaAbasi, H.; Shooshpasha, I.


    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.

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

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


    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

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

    Chan-Gi Park


    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.

  8. The relationship between unconfined compressive strength and leachate concentration of stabilised contaminated sediment

    Kabir Aliyu, Mohammed; Tarmizi Abd Karim, Ahmad; -Ming Chan, Chee


    Solidification/Stabilization (S/S) treatment was used in this study to immobilise copper (Cu) in contaminated river sediment. The sediment was artificially contaminated by spiking the solution of Copper sulphate (CuSO4.5H2O) to so as to get an average of 1000 ppm target concentration. Portland composite cement and Rice husk ash (RHA) were used as S/S agents. The amount of cement added to the mixture was l0% and while rice husk ash at the rate of 5%, l0%, 15% and 20% to the total dry weight of the mixture and then was cured for 7, 14 and 28 days. The unconfined compressive strength test (UCS) and toxicity characteristic leaching procedure (TCLP) were used to evaluate the effectiveness of the S/S treatments. From the results obtained it indicates that the partial replacement of cement with RHA in the binder system has increased the strength and the leachate concentration of copper was less in the treated sediment samples if compared with the untreated ones.

  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

    马晓宇; 李平


    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. 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

    庄心善; 王功勋; 朱瑞赓; 田苾


    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.

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

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


    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...

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

    Mohd Zairul A. Abdul Rahman


    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.

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

    覃银辉; 刘付华; 周琦


    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.

  14. Saturated-Unsaturated flow in a Compressible Leaky-unconfined Aquifer

    Mishra, Phoolendra K; Kuhlman, Kristopher L


    An analytical solution is developed for three-dimensional flow towards a partially penetrating large-diameter well in an unconfined aquifer bounded below by an aquitard of finite or semi-infinite extent. The analytical solution is derived using Laplace and Hankel transforms, then inverted numerically. Existing solutions for flow in leaky unconfined aquifers neglect the unsaturated zone following an assumption of instantaneous drainage assumption due to Neuman [1972]. We extend the theory of leakage in unconfined aquifers by (1) including water flow and storage in the unsaturated zone above the water table, and (2) allowing the finite-diameter pumping well to partially penetrate the aquifer. The investigation of model-predicted results shows that leakage from an underlying aquitard leads to significant departure from the unconfined solution without leakage. The investigation of dimensionless time-drawdown relationships shows that the aquitard drawdown also depends on unsaturated zone properties and the pumping...

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

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


    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.

  16. Compressive strength of thick composite panels

    Branner, Kim; Berring, Peter


    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...

  17. Compressive strength of continuous fiber unidirectional composites

    Thompson, Ronald H.

    Dow and Rosen's work in 1965 formed an intellectual framework for compressive strength of unidirectional composites. Compressive strength was explained in terms of micro-buckling, in which filaments are beams on an elastic foundation. They made simplifying assumptions, with a two dimensional idealization and linearized material properties. This study builds on their model, recognizing that the shear mode of instability drives unidirectional compressive strength. As a necessary corollary, the predictive methods developed in this study emphasize correct representation of composite shear stiffness. Non-linear effects related to matrix material properties, fiber misalignment, three dimensional representation, and thermal prestrains are taken into account. Four work streams comprise this study: first, development of a closed form analytical model; second, empirical methods development and model validation; third, creation and validation of a unit cell finite element model; and fourth, a patent application that leverages knowledge gained from the first three work streams. The analytical model characterizes the non-linearity of the matrix both with respect to shear and compressive loading. This improvement on existing analyses clearly shows why fiber modulus affects composite shear instability. Accounting for fiber misalignment in the model and experimental characterization of the fiber misalignment continuum are important contributions of this study. A simple method of compressive strength measurement of a small diameter monofilament glass-resin composite is developed. Sample definition and preparation are original, and necessary technologies are easily assessable to other researchers in this field. This study shows that glass fiber composites have the potential for high compressive strength. This potential is reached with excellent fiber alignment and suitable matrix characteristics, and results are consistent with model predictions. The unit cell three dimensional

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

    Guodong Li


    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.

  19. Compressive strength of delaminated aerospace composites.

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


    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.

  20. Size effect on compressive strength of reactive powder concrete

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


    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%.

  1. Non-Uniform Compressive Strength of Debonded Sandwich Panels

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


    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...

  2. Optimization of compressive strength in admixture-reinforced cement-based grouts

    Sahin Zaimoglu, A.


    Full Text Available The Taguchi method was used in this study to optimize the unconfined (7-, 14- and 28-day compressive strength of cement-based grouts with bentonite, fly ash and silica fume admixtures. The experiments were designed using an L16 orthogonal array in which the three factors considered were bentonite (0%, 0.5%, 1.0% and 3%, fly ash (10%, 20%, 30% and 40% and silica fume (0%, 5%, 10% and 20% content. The experimental results, which were analyzed by ANOVA and the Taguchi method, showed that fly ash and silica fume content play a significant role in unconfined compressive strength. The optimum conditions were found to be: 0% bentonite, 10% fly ash, 20% silica fume and 28 days of curing time. The maximum unconfined compressive strength reached under the above optimum conditions was 17.1 MPa.En el presente trabajo se ha intentado optimizar, mediante el método de Taguchi, las resistencias a compresión (a las edades de 7, 14 y 28 días de lechadas de cemento reforzadas con bentonita, cenizas volantes y humo de sílice. Se diseñaron los experimentos de acuerdo con un arreglo ortogonal tipo L16 en el que se contemplaban tres factores: la bentonita (0, 0,5, 1 y 3%, las cenizas volantes (10, 20, 30 y 40% y el humo de sílice (0, 5, 10 y 20% (porcentajes en peso del sólido. Los datos obtenidos se analizaron con mediante ANOVA y el método de Taguchi. De acuerdo con los resultados experimentales, el contenido tanto de cenizas volantes como de humo de sílice desempeña un papel significativo en la resistencia a compresión. Por otra parte, las condiciones óptimas que se han identificado son: 0% bentonita, 10% cenizas volantes, 20% humo de sílice y 28 días de tiempo de curado. La resistencia a compresión máxima conseguida en las anteriores condiciones era de 17,1 MPa.

  3. 49 CFR 238.405 - Longitudinal static compressive strength.


    ... 49 Transportation 4 2010-10-01 2010-10-01 false Longitudinal static compressive strength. 238.405 Section 238.405 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD... II Passenger Equipment § 238.405 Longitudinal static compressive strength. (a) To form an...

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

    Othuman Mydin M.A.


    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.

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

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


    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.

  6. Compressive strength of brick masonry made with weak mortars

    Pedersen, Erik Steen; Hansen, Klavs Feilberg


    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...... (fm≈6 N/mm2) compression tests of masonry with perforated bricks show that the EC6 expression is not always safe for Danish masonry. This is probably because the tensile strength of the bricks also has an effect on the compressive strength of masonry when the mortar is stronger than weak lime mortar...

  7. Compressive Strength of Compacted Clay-Sand Mixes

    Faseel Suleman Khan


    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.

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

    Jin-Keun Kim; Seong-Tae Yi


    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.

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

    HE Zhen-jun; SONG Yu-pu


    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.

  10. The Compressive Strength of Carbon Fibre Reinforced Plastics.


    and resin properties . Therefore, throughout this Report the term compressive failure will imply a microbuckling failure mode. A microbuckling failure...Compressive strength of fibre reinforced composite materials. ASTM STP 580, pp 364-377 (1975) 16 D.B.S. Berry Handbook of resin properties . Part A - cast

  11. Evaluation of adhesive and compressive strength of glass ionomer cements.

    Ramashanker; Singh, Raghuwar D; Chand, Pooran; Jurel, Sunit Km; Tripathi, Shuchi


    The aim of the study was to assess, compare and evaluate the adhesive strength and compressive strength of different brands of glass ionomer cements to a ceramometal alloy. (A) Glass ionomer cements: GC Fuji II (GC Corporation, Tokyo), Chem Flex (Dentsply DeTrey, Germany), Glass ionomer FX (Shofu-11, Japan), MR dental (MR dental suppliers Pvt Ltd, England). (B) Ceramometal alloy (Ni-Cr: Wiron 99; Bego, Bremen, Germany). (C) Cold cure acrylic resin. (E) Temperature cum humidity control chamber. (F) Instron Universal Testing Machine. Four different types of Glass ionomer cements were used in the study. From each type of the Glass ionomer cements, 15 specimens for each were made to evaluate the compressive strength and adhesive strength, respectively. The 15 specimens were further divided into three subgroups of five specimens. For compressive strength, specimens were tested at 2, 4 and 12 h by using Instron Universal Testing Machine. To evaluate the adhesive strength, specimens were surface treated with diamond bur, silicone carbide bur and sandblasting and tested under Instron Universal Testing Machine. It was concluded from the study that the compressive strength as well as the adhesive bond strength of MR dental glass ionomer cement with a ceramometal alloy was found to be maximum compare to other glass ionomer cements. Sandblasting surface treatment of ceramometal alloy was found to be comparatively more effective for adhesive bond strength between alloy and glass ionomer cement.

  12. Compressive Strength of Longitudinally Stiffened GRP Panels

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


    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...

  13. Static strength of gold compressed up to 127 GPa

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


    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.

  14. Prediction of 28-day Compressive Strength of Concrete from Early Strength and Accelerated Curing Parameters

    T.R. Neelakantan; S. Ramasundaram; Shanmugavel, R.; R. Vinoth


    Predicting 28-day compressive strength of concrete is an important research task for many years. In this study, concrete specimens were cured in two phases, initially at room temperature for a maximum of 30 h and later at a higher temperature for accelerated curing for a maximum of 3 h. Using the early strength obtained after the two-phase curing and the curing parameters, regression equations were developed to predict the 28-day compressive strength. For the accelerated curing (higher temper...


    Radoslav Sovják


    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.

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

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


    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.

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

    Mehdi Nikoo


    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.


    R. EMADI


    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.

  19. The impact of water content and ionic diffusion on the uniaxial compressive strength of shale

    Talal AL-Bazali


    Experimental data showed that water content has a profound influence on the uniaxial compressive strength of shale. Testing has shown a great decrease in the uniaxial compressive strength as the water content increases. Regression analysis was used in this work to develop a general equation for predicting uniaxial compressive strength of shale from the available information on its water content and dry uniaxial compressive strength. The impact of ionic diffusion on the compressive strength...

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

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


    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

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

    Khuram Rashid


    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.

  2. Modelling the effect of shear strength on isentropic compression experiments

    Thomson, Stuart; Howell, Peter; Ockendon, John; Ockendon, Hilary


    Isentropic compression experiments (ICE) are a way of obtaining equation of state information for metals undergoing violent plastic deformation. In a typical experiment, millimetre thick metal samples are subjected to pressures on the order of 10 - 102 GPa, while the yield strength of the material can be as low as 10-2 GPa. The analysis of such experiments has so far neglected the effect of shear strength, instead treating the highly plasticised metal as an inviscid compressible fluid. However making this approximation belies the basic elastic nature of a solid object. A more accurate method should strive to incorporate the small but measurable effects of shear strength. Here we present a one-dimensional mathematical model for elastoplasticity at high stress which allows for both compressibility and the shear strength of the material. In the limit of zero yield stress this model reproduces the hydrodynamic models currently used to analyse ICEs. Numerical solutions of the governing equations will then be presented for problems relevant to ICEs in order to investigate the effects of shear strength compared with a model based purely on hydrodynamics.

  3. Predicting The Compression Strength Of Impact-Damaged Sandwich Panels

    Ratcliffe, James; Jackson, Wade; Schaff, Jeffery


    The objective of this work was to develop a technique for predicting the residual compression strength of sandwich panels containing impact damage in one facesheet. The technique was tailored to predict the strength of specimens that exhibit a failure mode involving the formation of kink bands at locations of peak strain in the region of impact damage. Under continued compression loading, the kink bands propagate in a stable manner perpendicular to the applied load. When a critical kink-band length is reached, growth becomes unstable corresponding to panel failure. The analysis follows in two sections. The first section calculates the far-field stress required for stable kink-band growth and the second calculates that required for unstable growth. The residual strength prediction is made when the stress for stable growth becomes equal to that for unstable kink-band growth. Initial comparisons between analysis and experiment show good agreement.

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

    Protosenya Anatoliy


    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.

  5. Compressive Strength of Concrete Containing Palm Kernel Shell Ash

    FADELE Oluwadamilola A


    Full Text Available This study examined the influence of varying palm kernel shell ash content, as supplementary cementitious material (SCM at specified water/cement ratios and curing ages on the compressive strength of concrete cubes samples. Palm kernel shell ash was used as a partial replacement for ordinary Portland cement (OPC up to 30% at 5% intervals using mix ratio 1:2:4. River sand with particles passing 4.75mmBS sieve and crushed aggregate of 20mm maximum size were used while the palm kernel shell ash used was ofparticles passing through 212μm BS sieve. The compressive strength of the test cubes (100mm were tested at 5 different curing ages of 3, 7, 14, 28 and 56 days. The result showed that test cube containing Palm kernel shell ash gained strength over a longer curing period compared with ordinary Portlandcement concrete samples and the strength varies with percentagePKSAcontent in the cube samples. The results showed that at 28 days test cubes containing 5%, 10%, 15%, 20%, 25% and 30% PKSA content achieved compressive strength of 26.1 MPa, 22.53MPa, 19.43 MPa, 20.43 MPa, 16.97 MPa and 16.5MPa compared to 29MPa of Ordinary Portland cement concrete cubes. It was concluded that for structural concrete works requiring a characteristic strength of 25Mpa,5% palm kernel shell ash can effectively replace ordinary Portland cement while up to 15% PKSA content can be used for concrete works requiring 20Mpa strength at 28 days

  6. Optimization of compressive strength of zirconia based dental composites

    U V Hambire; V K Tripathi


    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.

  7. Residual Compressive Strength of Laterized Concrete Subjected to Elevated Temperatures

    Robert M. Brooks


    Full Text Available This research presents the results of an experimental program to investigate the strength performance of laterized concrete (LATCON when subjected to elevated temperatures of 200, 400 and 600ºC. Six concrete mixes incorporating 0, 10, 20, 30, 40 and 50% Laterite as a replacement by weight of sand was prepared. After heat pretreatment specimens were cooled using either rapid cooling (water-cooling or natural cooling (air-cooling. An analysis of variance test shows that exposure temperature, cooling regime, and their interaction have a significant influence on the compressive strength of the samples. When subjected to the investigated temperatures specimens experienced strength losses that increased with temperature. This study further reveals that air-cooled concrete specimens maintained higher residual strength values than water-cooled specimens. A comparison of the residual compressive strength data obtained in this study with code provisions in Eurocode and CEB design curve shows that these codes could be applied to LATCON subjected to temperature below 400ºC.

  8. Tow collapse model for compression strength of textile composites

    Emehel, T.C.; Shivakumar, K.N. [North Carolina A and T State Univ., Greensboro, NC (United States)


    The unidirectional composite compression strength model based on microbuckling of fibers embedded in a rigid-plastic matrix was extended to multiaxial laminates and textile composites. The resulting expression is a function of matrix yield strength under the fiber constraint, fiber misalignment angle, fiber volume fraction, and the area fractions of various sets of inclined tows. The analysis was verified by experimentation. Compression tests were conducted on laminated, three-dimensional triaxially braided and orthogonally woven composites using the IITRI test specimen. The laminate specimens were made up of AS4/3501-6 graphite/epoxy composite with (0){sub 24}, (0/30/0/{minus}30){sub 3S}, and ((0/90)6/0){sub S} stacking sequence. Textile composites were made of BASF G30-500 graphite fiber tows (tow size is 6K) and Dow Chemicals Tactix 123 matrix. Fiber preform architecture of braided and woven composites before resin consolidation was 0/{+-}17 and 0/90, respectively and after consolidation it was about (7/{+-}20) and (5/90/90), respectively. The analysis agreed reasonably well with the test data for all cases considered. The axial fiber/tow misalignment angle for laminated, braided, and woven composites were about 4, 7, and 5 degrees, respectively. The compression strength was found to be strongly dependent on the percentage of axial tows and its misalignment angle. A small variation in the off-axis fiber/tow orientation had marginal effect on the compression strength. Hence, the off axis tow misalignment angle can be assumed to be same as the initial laminate or the two orientation angle.

  9. Compressive Strength of a Longitudinally Stiffened FRP Panel

    Riber, Hans Jørgen; Jensen, Jørgen Juncher; Pedersen, Preben Terndrup


    A structural analysis of a cross stiffened orthotropic FRP panel subjected to uni-axial compressive load is crarried out. Analytical Calculations of the strength of the panel are presented and compared to finite element analysis performed by different authors. Both analytica and finite element ap...... approaches confirm an identical failrue scenario. In the present case, the load carrying capacity of the stiffened panel is limited by the plate stiffener debonding stress....

  10. Estimation of concrete compressive strength using artificial neural network

    Kostić, Srđan; Vasović, Dejan


    In present paper, concrete compressive strength is evaluated using back propagation feed-forward artificial neural network. Training of neural network is performed using Levenberg-Marquardt learning algorithm for four architectures of artificial neural networks, one, three, eight and twelve nodes in a hidden layer in order to avoid the occurrence of overfitting. Training, validation and testing of neural network is conducted for 75 concrete samples with distinct w/c ratio and amount of superp...

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

    WANG Qiang; YAN Peiyu; KONG Xiangming; YANG Jinbo


    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.

  12. The impact of water content and ionic diffusion on the uniaxial compressive strength of shale

    Talal AL-Bazali


    Finally, the impact of ionic diffusion on the compressive strength of shale was carried out in the absence of both chemical osmosis and capillary forces. Results show that the invasion of sodium and calcium ions into shale reduced its compressive strength considerably while the invasion of potassium ions enhanced its compressive strength.

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

    J. Kováčik


    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.

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

    苏捷; 叶缙垚; 方志; 赵明华


    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.

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

    Marwan Mostafa


    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.

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

    Nikolić Irena


    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

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

    Valcuende, M.O.


    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

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

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


    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.

  19. Developing an artificial neural network model for predicting concrete’s compression strength and electrical resistivity

    Juan Manuel Lizarazo Marriaga


    Full Text Available The present study was conducted for predicting the compressive strength of concrete based on unit weight ultrasonic and pulse velocity (UPV for 41 different concrete mixtures. This research emerged from the need for a rapid test for predicting concrete’s compressive strength. The research was also conducted for predicting concrete’s electrical resistivity based on unit weight ultrasonic, pulse velocity (UPV and compressive strength with the same mixes. The prediction was made using simple regression analysis and artificial neural networks. The results revealed that artificial neural networks can be used for effectively predicting compressive strength and electrical resistivity.

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

    Keun-Hyeok Yang


    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.

  1. Empirical Formula for the Relationship between Compressive Strength and Test Temperature of Carbon/Polyimide Composites

    濱口, 泰正; Hamaguchi, Yasumasa


    T800H/PMR-15 carbon/polyimide composite possesses good specific strength and specific rigidity in the high-temperature region around 300C. This material is an advanced structural composite for use in elevons and other secondary structures of the unmanned space reentry vehicle HOPE-X. The author carried out basic strength evaluation tests on this material. Compressive strength data is especially important for structural design using composite materials. Compressive strength data was therefore ...

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

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


    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...

  3. Fatigue of concrete under compression: Database and proposal for high strength concrete

    Lantsoght, E.O.L.


    The compressive strength of concrete decreases as an element is subjected to cycles of loading. In a typical fatigue test for the concrete compressive strength, a concrete specimen (typically a cylinder) is loaded between a lower and upper stress limit. These limits are expressed as a fraction of th

  4. Prediction of potential compressive strength of Portland clinker from its mineralogy

    Svinning, K.; Høskuldsson, Agnar; Justnes, H.


    Based on a statistical model first applied for prediction of compressive strength up to 28 d from the microstructure of Portland cement, potential compressive strength of clinker has been predicted from its mineralogy. The prediction model was evaluated by partial least squares regression. The mi...

  5. Dataset of long-term compressive strength of concrete with manufactured sand.

    Ding, Xinxin; Li, Changyong; Xu, Yangyang; Li, Fenglan; Zhao, Shunbo


    This paper presents 186 groups compressive strength tests data of concrete with manufactured sand (MSC) in different curing age and 262 groups compressive strength tests data of MSC at 28 days collected from authors' experiments and other researches in China. Further interpretation and discussion were described in this issues.

  6. Fracture Energy-Based Brittleness Index Development and Brittleness Quantification by Pre-peak Strength Parameters in Rock Uniaxial Compression

    Munoz, H.; Taheri, A.; Chanda, E. K.


    Brittleness is a fundamental mechanical rock property critical to many civil engineering works, mining development projects and mineral exploration operations. However, rock brittleness is a concept yet to be investigated as there is not any unique criterion available, widely accepted by rock engineering community able to describe rock brittleness quantitatively. In this study, new brittleness indices were developed based on fracture strain energy quantities obtained from the complete stress-strain characteristics of rocks. In doing so, different rocks having unconfined compressive strength values ranging from 7 to 215 MPa were examined in a series of quasi-static uniaxial compression tests after properly implementing lateral-strain control in a closed-loop system to apply axial load to rock specimen. This testing method was essential to capture post-peak regime of the rocks since a combination of class I-II or class II behaviour featured post-peak stress-strain behaviour. Further analysis on the post-peak strain localisation, stress-strain characteristics and the fracture pattern causing class I-II and class II behaviour were undertaken by analysing the development of field of strains in the rocks via three-dimensional digital image correlation. Analysis of the results demonstrated that pre-peak stress-strain brittleness indices proposed solely based on pre-peak stress-strain behaviour do not show any correlation with any of pre-peak rock mechanical parameters. On the other hand, the proposed brittleness indices based on pre-peak and post-peak stress-strain relations were found to competently describe an unambiguous brittleness scale against rock deformation and strength parameters such as the elastic modulus, the crack damage stress and the peak stress relevant to represent failure process.

  7. Prediction of concrete compressive strength due to long term sulfate attack using neural network

    Ahmed M. Diab


    Full Text Available This work was divided into two phases. Phase one included the validation of neural network to predict mortar and concrete properties due to sulfate attack. These properties were expansion, weight loss, and compressive strength loss. Assessment of concrete compressive strength up to 200 years due to sulfate attack was considered in phase two. The neural network model showed high validity on predicting compressive strength, expansion and weight loss due to sulfate attack. Design charts were constructed to predict concrete compressive strength loss. The inputs of these charts were cement content, water cement ratio, C3A content, and sulfate concentration. These charts can be used easily to predict the compressive strength loss after any certain age and sulfate concentration for different concrete compositions.

  8. The Compressive Strength of High-Performance Concrete and Ultrahigh-Performance

    E. H. Kadri


    Full Text Available The compressive strength of silica fume concretes was investigated at low water-cementitious materials ratios with a naphthalene sulphonate superplasticizer. The results show that partial cement replacement up to 20% produce, higher compressive strengths than control concretes, nevertheless the strength gain is less than 15%. In this paper we propose a model to evaluate the compressive strength of silica fume concrete at any time. The model is related to the water-cementitious materials and silica-cement ratios. Taking into account the author's and other researchers’ experimental data, the accuracy of the proposed model is better than 5%.

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

    XIAO Lianzhen; WEI Xiaosheng


    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.

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

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


    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.

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


    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.

  12. A comparison study on the flexural strength and compressive strength of four resin-modified luting glass ionomer cements.

    Li, Yuan; Lin, Hong; Zheng, Gang; Zhang, Xuehui; Xu, Yongxiang


    The purpose of this study is to compare the differences in flexural strength and compressive strength between four resin-modified luting glass ionomer cements that are commonly used in clinics. Furthermore, this study investigates the influence of curing mode on the flexural strength and compressive strength of dual-cured resin-modified glass ionomer cements. Initially, flexural strength and compressive strength test specimens were prepared for RL, NR, GCP, and GCC. The RL group and NR group were cured by the light-curing mode and chemical-curing mode. Five specimens were prepared for each test group, and the flexural strength and compressive strength of each were measured. Data were analyzed by one-way ANOVA with SPSS 13.0. Furthermore, the fracture morphology of the flexural specimens was observed by SEM. The result of the mean flexural strength of each group is as follows: the NR light-cured group > NR chemically-cured group > GCP > RL light-cured group > GCC > RL chemically-cured group. More specifically, the flexural strength of the NR light-cured group ((42.903±4.242) MPa) is significantly higher (P NR chemically-cured group > NR light-cured group > GCC > RL light-cured group > RL chemically-cured group. Although the compressive strengths of the NR and GCP groups are higher than those of the GCC and RL groups, there are no significant differences (P>0.05) between NR and GCP, and no significant differences between GCC and RL. Furthermore, there are no significant differences (P>0.05) between the two curing modes on NR and RL. From the present study, it can be concluded that NR has superior flexural strength and compressive strength compared to the other three materials. Additionally, the curing mode can affect the flexural strength of dual-cured RMGIC because with the light-curing mode, the flexural strength is higher than with the chemical-curing mode. Therefore, light curing is an essential procedure when using dual-cured RMGIC in clinics.

  13. Research on compressive strength of recycled cement mortar after high temperature

    Zhang, Xianggang; Yang, Jianhui; Deng, Dapeng


    In order to study cube compressive strength of recycled fine aggregate cement mortar after different temperatures, with the affect parameters between replacement rate of recycled fine aggregate and temperature, 45 standard cube test blocks were designed and produced to carry out compressive strength test. The failure process and failure mode of test blocks were observed. Ultimate compressive strength of cube blocks were measured, the relations between cube compressive strength and the replacement rates of recycled fine aggregate under different temperatures as well as the relations between cube compressive strength and temperatures under different replacement rates were all analyzed, the influence change parameters made on cube compressive strength was discussed. The results showed: the failure process and the failure mode of recycled fine aggregate cement mortar and the failure process and the failure mode of nature is similar; when the temperature reached 400°C, the block has no burst phenomenon, but the colour of block into a dark pink; with the increase of recycled fine aggregate, the mass lose rate of block is increase; effect different temperature make on cube compressive strength of test block is not obvious when temperature keeps same for 3h.

  14. The influence of biocalcification on soil-cement interlocking block compressive strength

    Yoosathaporn, S.


    Full Text Available Description of the subject. Soil-cement interlocking block is used as the building block for many civil structures in Thailand. The addition of many alternative materials into interlocking block in order to improve compressive strength has been reported. However, there is currently no report on the influence of application of biocalcification or microbiologically induced calcite precipitation (MICP on interlocking block compressive strength. Objectives. This study aimed to investigate the effect of biocalcification on compressive strength of soil-cement interlocking block. Method. Soil bacterium, Bacillus pasteurii KCTC 3558, and Effective Microorganisms (EM were added into interlocking block before molding as the replacement of mixing water. The change of compressive strength in interlocking block at 3, 7, 14 and 28 days of incubation was determined. Results. At 28 days, the compressive strength of interlocking block supplemented with B. pasteurii KCTC 3558 and 5% EM were 7.38% and 9.79% significantly higher than control. Calcium carbonate crystals were also observed under scanning electron microscope which suggested that an increased compressive strength of interlocking block was caused by biocalcification. Conclusions. Our results showed that microbiologically induced calcite precipitation could help increasing the compressive strength of soil-cement interlocking block.

  15. [Effects of silicon carbide on the cure depth, hardness and compressive strength of composite resin].

    Wang, Ke; Lin, Yi'na; Liu, Xiaoqing


    The hardness, compressive strength and cure depth are important indices of the composite resin. This investigation was made with regard to the effects of silicon carbide on the cure depth, hardness and compressive strength of the light-curing composite resin. Different amounts of silicon carbide were added to the light-curing composite resin, which accounted for 0 wt%, 1 wt%, 0.6 wt%, 0.3 wt%, 0.1 wt%, 0.05 wt% and 0.005 wt% of the composite resin, respectively. The hardness, compressive strength and cure depth of the six afore-mentioned groups of composite resin were measured by the vernier caliper, the vickers hardness tester and the tensile strength of machine, respectively. The results showed that silicon carbide improved the hardness and compressive strength of the light-curing composite resin,when the concentration was 0.05 wt%. And the cure depth was close to that of control.

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

    Sudin M.A.S.


    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.

  17. Compressive strength of fiber reinforced composite materials. [composed of boron and epoxy

    Davis, J. G., Jr.


    Results of an experimental and analytical investigation of the compressive strength of unidirectional boron-epoxy composite material are presented. Observation of fiber coordinates in a boron-epoxy composite indicates that the fibers contain initial curvature. Combined axial compression and torsion tests were conducted on boron-epoxy tubes, and it was shown that the shear modulus is a function of axial compressive stress. An analytical model which includes initial curvature in the fibers and permits an estimate of the effect of curvature on compressive strength is proposed. Two modes of failure which may result from the application of axial compressive stress are analyzed, delamination and shear instability. Based on tests and analysis, failure of boron-epoxy under axial compressive load is due to shear instability.

  18. Effect of luting media on the compressive strengths of two types of all-ceramic crown.

    McCormick, J T; Rowland, W; Shillingburg, H T; Duncanson, M G


    This study evaluated the effect of selected luting media on the compressive strength of two types of all-ceramic crown. Tooth preparation was standardized; each preparation had a shoulder width of approximately 1.2 mm, and all internal preparation angles were rounded. Hi-Ceram and Dicor all-ceramic crowns were fabricated and cemented into the preparations with zinc phosphate, glass-ionomer, or composite resin cement. Coronal compressive fracture strengths were determined, using a set of unrestored teeth as a control. There were no statistically significant differences among the mean compressive strengths of the three luting media, and there was no statistically significant difference between the mean compressive strength of Dicor and that of the natural tooth control.

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

    Xingang Wang


    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.

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

    WANG Qiang; YAN Peiyu; FENG Jianwen


    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.

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

    Jensen, Find Mølholt


    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...

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

    Moelholt Jensen, F.


    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 post buckling behaviour of the compression flange is studied. Different compressive failure mechanisms are discussed and the limitations in using the Finite Element Method. A suggestion to the further work is made. (au)

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

    J BU; Z TIAN


    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.

  4. The influence of biocalcification on soil-cement interlocking block compressive strength

    Yoosathaporn, S.; Tiangburanatham, P.; Pathom-aree, W.


    Description of the subject. Soil-cement interlocking block is used as the building block for many civil structures in Thailand. The addition of many alternative materials into interlocking block in order to improve compressive strength has been reported. However, there is currently no report on the influence of application of biocalcification or microbiologically induced calcite precipitation (MICP) on interlocking block compressive strength. Objectives. This study aimed to investigate the ef...

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

    Anneza L. H.


    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.

  6. Unfired clay bricks – moisture properties and compressive strength

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


    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...

  7. Derivation of the Bi-axial Bending, Compression and Shear Strengths of Timber Beams

    Van der Put, T.A.C.M.


    The derivation is given of the combined bi-axial bending, compression and shear strength of timber beams. As for other materials the elastic–full plastic limit design approach applies, which is known to precisely explain and predict uniaxial bending strength behaviour. The derivation is based on cho

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

    JIANG Hong-bin; LI Long-fei


    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.

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

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


    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.

  10. Achievement of Early Compressive Strength in Concrete Using Sporosarcina pasteurii Bacteria as an Admixture

    Rakesh Chidara


    Full Text Available Often it is observed, attainment of early compressive strength in concrete is a challenge. Researchers have tried various admixtures to achieve the objective. This work addresses the issue of achieving early compressive strength in concrete using a bacterium called Sporosarcina pasteurii. The bacterium is characterised with the ability to precipitate calcium carbonate in the presence of any carbonate source and is known for its resistive capacity in extreme temperature and pressure zones. To establish the objective of gain in early strength around 192 concrete cubes were tested at 3, 7, 14, and 28 days and the results compared with controlled concrete. The bacterium was used in combination of chemicals and the dosage proportions were altered to achieve the desired M20 compressive strength at 28 days.

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

    Janković Ksenija


    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.

  12. Non-Uniform Compressive Strength of Debonded Sandwich Panels

    Berggreen, Carl Christian; Simonsen, Bo Cerup


    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.......(2005)., shows that the model is indeed able to predict the failure modes and the residual strength of damaged panels with accuracy sufficient for practical applications. This opens up for a number of important engineering applications, for example risk-based inspection and repair schemes....

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

    Weerheijm, J.


    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

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

    O'Brien, T. Kevin; Krueger, Ronald


    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.

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

    Hongying Dong


    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.

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

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


    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.

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

    LI Q M; LU Y B


    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.

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

    Yan MA; Alun


    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.

  19. In situ strength of coal bed based on the size effect study on the uniaxial compressive strength

    Gonzatti C.; Zorzi L.; Agostini I.M.; Fiorentini J.A.; Viero A.P.; Philipp R.P.


    In the early 1990s, the Foundation for Science and Technology of Rio Grande do Sul State (CIENTEC) developed a pioneering study in Brazil, related to the simultaneous mining of multiple coal seams. One of the activities included detailed studies on the geomechanical characterization of materials present in the Irapua coal seam, under exploitation in the A-Sangao Mine, located near the city of Criciuma-SC, within the South-Catarinense coalfield. The goal of the laboratory tests was to define the behavior of the uniaxial compressive strength of the Irapua coal seam and establish a first approximation for the in situ strength value of this coal seam, since existing knowledge is solely based on practical mining experience over the years. Large samples of the coal seam were collected, using special techniques to maintain the integrity of the material, and a set of 56 uniaxial compression tests in cubic specimens, with side length ranging from 4.5 to 31 cm, were conducted in laboratory. This paper describes the experimen-tal techniques used in the assays, and also presents the uniaxial compression strength results obtained. Moreover, important aspects of this type of study are considered, highlighting the size effect for the carbonaceous bed and the estimation of in situ strength values for the Irapua coal seam.

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

    Videla, C.


    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

  1. Dynamic compressive and tensile strengths of spark plasma sintered alumina

    Girlitsky, I.; Zaretsky, E.; Kalabukhov, S.; Dariel, M. P.; Frage, N.


    Fully dense submicron grain size alumina samples were manufactured from alumina nano-powder using Spark Plasma Sintering and tested in two kinds of VISAR-instrumented planar impact tests. In the first kind, samples were loaded by 1-mm tungsten impactors, accelerated to a velocity of about 1 km/s. These tests were aimed at studying the Hugoniot elastic limit (HEL) of Spark Plasma Sintering (SPS)-processed alumina and the decay, with propagation distance, of the elastic precursor wave. In the tests of the second kind, alumina samples of 3-mm thickness were loaded by 1-mm copper impactors accelerated to 100-1000 m/s. These tests were aimed at studying the dynamic tensile (spall) strength of the alumina specimens. The tensile fracture of the un-alloyed alumina shows a monotonic decline of the spall strength with the amplitude of the loading stress pulse. Analysis of the decay of the elastic precursor wave allowed determining the rate of the irreversible (inelastic) strains in the SPS-processed alumina at the initial stages of the shock-induced inelastic deformation and to clarify the mechanisms responsible for the deformation. The 1-% addition of Cr2O3 decreases the HEL of the SPS-processed alumina by 5-% and its spall strength by 50% but barely affects its static properties.

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

    Sujeong Lee


    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.

  3. Compressive Strength of Volcanic Ash/Ordinary Portland Cement Laterized Concrete

    Olusola K. O.


    Full Text Available This study investigates the effect of partial replacement of cement with volcanic ash (VA on the compressive strength of laterized concrete. A total of 192 cubes of 150mm dimensions were cast and cured in water for 7, 14, 21, and 28 days of hydration with cement replacement by VA and sand replacement by laterite both ranging from 0 to 30% respectively, while a control mix of 28-day target strength of 25 N/mm2 was adopted. The results show that the density and compressive strength of concrete decreased with increase in volcanic ash content. The 28-day, density dropped from 2390 kg/m3 to 2285 kg/m3 (i.e. 4.4% loss and the compressive strength from 25.08 N/mm2 to 17.98 N/mm2 (i.e. 28% loss for 0-30% variation of VA content with no laterite introduced. The compressive strength also decreased with increase in laterite content; the strength of the laterized concrete however increases as the curing age progresses.

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

    Setyawan, Paryanto Dwi; Sugiman, Saputra, Yudhi


    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.

  5. A Study of Compressive Strength Characteristics of Laterite Sand Hollow Blocks

    Abiodun Olanipekun


    Full Text Available This paper presents the results of experimental investigations carried out on partial replacement of sand with laterite as it affects the compressive strength of sandcrete hollow blocks. Two mix proportions (1:6 and 1:8 were used with laterite content varying between 0 and 50% at 10% intervals. Hand and machine compaction methods were used. Curing was done by sprinkling water on the specimens. The results showed that for each mix proportion and compaction method, the compressive strength decreases with increase in laterite content. Machine compacted hollow sandcrete blocks made from mix ratio 1:6 and with up to 10% laterite content is found suitable and hence recommended for building construction having attained a 28-day compressive strength of 2.07N/mm2 as required by the Nigerian Standards.

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

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


    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 ℃.

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

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


    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.

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

    Bali Ika


    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.

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

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


    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.

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

    FENQ Qi; TAN Jia-hua


    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.

  11. Prediction of Human Vertebral Compressive Strength Using Quantitative Computed Tomography Based Nonlinear Finite Element Method

    Ahad Zeinali


    Full Text Available Introduction: Because of the importance of vertebral compressive fracture (VCF role in increasing the patients’ death rate and reducing their quality of life, many studies have been conducted for a noninvasive prediction of vertebral compressive strength based on bone mineral density (BMD determination and recently finite element analysis. In this study, QCT-voxel based nonlinear finite element method is used for predicting vertebral compressive strength. Material and Methods: Four thoracolumbar vertebrae were excised from 3 cadavers with an average age of 42 years. They were then put in a water phantom and were scanned using the QCT. Using a computer program prepared in MATLAB, detailed voxel based geometry and mechanical characteristics of the vertebra were extracted from the CT images. The three dimensional finite element models of the samples were created using ANSYS computer program. The compressive strength of each vertebra body was calculated based on a linearly elastic-linearly plastic model and large deformation analysis in ANSYS and was compared to the value measured experimentally for that sample. Results: Based on the obtained results the QCT-voxel based nonlinear finite element method (FEM can predict vertebral compressive strength more effectively and accurately than the common QCT-voxel based linear FEM. The difference between the predicted strength values using this method and the measured ones was less than 1 kN for all the samples. Discussion and Conclusion: It seems that the QCT-voxel based nonlinear FEM used in this study can predict more effectively and accurately the vertebral strengths based on every vertebrae specification by considering their detailed geometric and densitometric characteristics.

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

    MENG Xian-hong; SONG Yu-pu


    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.

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

    Alireza Adl


    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.

  14. The Effects of Different Curing Methods on the Compressive Strength of Terracrete

    O. Alake


    Full Text Available This research evaluated the effects of different curing methods on the compressive strength of terracrete. Several tests that included sieve analysis were carried out on constituents of terracrete (granite and laterite to determine their particle size distribution and performance criteria tests to determine compressive strength of terracrete cubes for 7 to 35 days of curing. Sand, foam-soaked, tank and open methods of curing were used and the study was carried out under controlled temperature. Sixty cubes of 100 × 100 × 100mm sized cubes were cast using a mix ratio of 1 part of cement, 1½ part of latrite, and 3 part of coarse aggregate (granite proportioned by weight and water – cement ratio of 0.62. The result of the various compressive strengths of the cubes showed that out of the four curing methods, open method of curing was the best because the cubes gained the highest average compressive strength of 10.3N/mm2 by the 35th day.

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

    Rattanasak, U; Jaturapitakkul, C; Sudaprasert, T


    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.

  16. Prediction of compressive strength up to 28 days from microstructure of Portland cement

    Svinning, K.; Høskuldsson, Agnar; Justnes, H.


    The influence of the characteristics or the microstructure of Portland cement on compressive strength up to 28 days has been statistically investigated by application of partial least square (PLS) analysis. The main groups of characteristics were mineralogy and superficial microstructure represen...

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

    Ali Nazari; Shadi Riahi


    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.

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

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


    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.

  19. Effect of Impact Damage and Open Hole on Compressive Strength of Hybrid Composite Laminates

    Hiel, Clement; Brinson, H. F.


    Impact damage tolerance is a frequently listed design requirement for composites hardware. The effect of impact damage and open hole size on laminate compressive strength was studied on sandwich beam specimens which combine CFRP-GFRP hybrid skins and a syntactic foam core. Three test specimen configurations have been investigated for this study. The first two were sandwich beams which were loaded in pure bending (by four point flexure). One series had a skin damaged by impact, and the second series had a circular hole machined through one of the skins. The reduction of compressive strength with increasing damage (hole) size was compared. Additionally a third series of uniaxially loaded open hole compression coupons were tested to generate baseline data for comparison with both series of sandwich beams.

  20. Damage Characteristics and Residual Strength of Composite Sandwich Panels Impacted with and Without Compression Loading

    McGowan, David M.; Ambur, Damodar R.


    The results of an experimental study of the impact damage characteristics and residual strength of composite sandwich panels impacted with and without a compression loading are presented. Results of impact damage screening tests conducted to identify the impact-energy levels at which damage initiates and at which barely visible impact damage occurs in the impacted facesheet are discussed. Parametric effects studied in these tests include the impactor diameter, dropped-weight versus airgun-launched impactors, and the effect of the location of the impact site with respect to the panel boundaries. Residual strength results of panels tested in compression after impact are presented and compared with results of panels that are subjected to a compressive preload prior to being impacted.

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

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


    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.

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

    Alohan Omoregie


    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

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

    Sobhnamayan F


    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.

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

    Angel Alvarez-Arenal


    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.

  5. Effect of dilute tungsten alloying on the dynamic strength of tantalum under ramp compression

    Alexander, C. S.; Brown, J. L.; Millett, J. C. F.; Whiteman, G.; Asay, J. R.; Bourne, N. K.


    The strength of tantalum and tantalum alloys are of considerable interest due to their widespread use in both military and industrial applications. Previous work has shown that strength in these materials is tied to dislocation density and mobility within the microstructure. Accordingly, strength has been observed to increase with dilute alloying which serves to increase the dislocation density. In this study, we examine the effect of alloying on the strength of a dilute tantalum-tungsten alloy (2.5 weight percent W) under ramp compression. The strength of the alloy is measured using the ``self-consistent'' technique which examines the response under longitudinal unloading from peak compression. The results are compared to previous studies of pure tantalum and dilute tantalum-tungsten alloys under both shock and ramp compression and indicate strengthening of the alloy when compared to pure tantalum. Sandia National Labs is a multi-program laboratory managed and operated by Sandia Corp., a wholly owned subsidiary of Lockheed Martin Corp., for the U.S. Department of Energy's National Nuclear Security Administration under Contract DE-AC04-94AL85000.

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

    Akaninyene Afangide Umoh


    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.

  7. Influence of uncoated and coated plastic waste coarse aggregates to concrete compressive strength

    Purnomo Heru


    Full Text Available The use of plastic waste as coarse aggregates in concrete is part of efforts to reduce environmental pollution. In one hand the use of plastic as aggregates can provide lighter weight of the concrete than concrete using natural aggregates, but on the other hand bond between plastic coarse aggregates and hard matrix give low concrete compressive strength. Improvement of the bond between plastic coarse aggregate and hard matrix through a sand coating to plastic coarse aggregate whole surface is studied. Sand used to coat the plastic aggregates are Merapi volcanic sand which are taken in Magelang. Three mixtures of polypropylene (PP coarse plastic aggregates, Cimangkok river sand as fine aggregates, water and Portland Cement Composite with a water-cement ratio of 0.28, 0.3 and 0.35 are conducted. Compression test are performed on concrete cylindrical specimens with a diameter of 10 cm and a height of 20 cm. The results in general show that concrete specimens using plastic aggregates coated with sand have higher compressive strength compared to those of concrete specimens using plastic aggregates without sand coating. The bond improvement is indirectly indicated by the betterment of concrete compressive strength.

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

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


    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.

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

    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

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

    Sair Kahraman; Tekin Yeken


    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.


    Xie Zonghong; Anthony J. Vizzini; Tang Qingru


    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.

  12. A Finite Element Analysis for Predicting the Residual Compressive Strength of Impact-Damaged Sandwich Panels

    Ratcliffe, James G.; Jackson, Wade C.


    A simple analysis method has been developed for predicting the residual compressive strength of impact-damaged sandwich panels. The method is tailored for honeycomb core-based sandwich specimens that exhibit an indentation growth failure mode under axial compressive loading, which is driven largely by the crushing behavior of the core material. The analysis method is in the form of a finite element model, where the impact-damaged facesheet is represented using shell elements and the core material is represented using spring elements, aligned in the thickness direction of the core. The nonlinear crush response of the core material used in the analysis is based on data from flatwise compression tests. A comparison with a previous analysis method and some experimental data shows good agreement with results from this new approach.

  13. A Finite Element Analysis for Predicting the Residual Compression Strength of Impact-Damaged Sandwich Panels

    Ratcliffe, James G.; Jackson, Wade C.


    A simple analysis method has been developed for predicting the residual compression strength of impact-damaged sandwich panels. The method is tailored for honeycomb core-based sandwich specimens that exhibit an indentation growth failure mode under axial compression loading, which is driven largely by the crushing behavior of the core material. The analysis method is in the form of a finite element model, where the impact-damaged facesheet is represented using shell elements and the core material is represented using spring elements, aligned in the thickness direction of the core. The nonlinear crush response of the core material used in the analysis is based on data from flatwise compression tests. A comparison with a previous analysis method and some experimental data shows good agreement with results from this new approach.

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

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


    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)

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

    Vijaykumar H.K


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

    Wilfrido Martínez-Molina


    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.

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

    Sakshi Gupta


    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.

  18. Prediction of Compressive Strength of Concrete Using Artificial Neural Network and Genetic Programming

    Palika Chopra


    Full Text Available An effort has been made to develop concrete compressive strength prediction models with the help of two emerging data mining techniques, namely, Artificial Neural Networks (ANNs and Genetic Programming (GP. The data for analysis and model development was collected at 28-, 56-, and 91-day curing periods through experiments conducted in the laboratory under standard controlled conditions. The developed models have also been tested on in situ concrete data taken from literature. A comparison of the prediction results obtained using both the models is presented and it can be inferred that the ANN model with the training function Levenberg-Marquardt (LM for the prediction of concrete compressive strength is the best prediction tool.

  19. Comparative Investigation on Brazing Behavior, Compressive Strength, and Wear Properties of Multicrystalline CBN Abrasive Grains

    Wen-Feng Ding


    Full Text Available In order to fabricate the abrasive wheels with good grain self-sharpening capacity, two types of multicrystalline CBN grains, that is, polycrystalline CBN (PCBN and binderless CBN (BCBN, were brazed using Cu-Sn-Ti alloy, respectively. Comparative investigation on the brazing interface, compressive strength, and wear properties of the different grains was carried out. Results obtained show that the PCBN grains have more intricate reaction, more complicated resultants, and thicker reaction layer than the BCBN counterparts under the identical brazing conditions. Though the average compressive strength of the PCBN grains is similar to that of BCBN ones, stronger self-sharpening action by virtue of the microfracture behavior takes place with BCBN grains during grinding. As a consequence, compared to the brazed PCBN wheels and the conventional monocrystalline CBN (MCBN ones, longer service life is obtained for the brazed BCBN wheels.

  20. An Exploratory Compressive Strength Of Concrete Containing Modified Artificial Polyethylene Aggregate (MAPEA)

    Hadipramana, J.; Mokhatar, S. N.; Samad, A. A. A.; Hakim, N. F. A.


    Concrete is widely used in the world as building and construction material. However, the constituent materials used in concrete are high cost when associated with the global economic recession. This exploratory aspires to have an alternative source of replacing natural aggregate with plastic wastes. An investigation of the Modified Artificial Polyethylene Aggregate (MAPEA) as natural aggregate replacement in concrete through an experimental work was conducted in this study. The MAPEA was created to improve the bonding ability of Artificial Polyethylene Aggregate (APEA) with the cement paste. The concrete was mixed with 3%, 6%, 9%, and 12% of APEA and MAPEA for 14 and 28 curing days, respectively. Furthermore, the compressive strength test was conducted to find out the optimum composition of MAPEA in concrete and compared to the APEA concrete. Besides, this study observed the influence and behaviour of MAPEA in concrete. Therefore, the Scanning Electron Microscopy was applied to observe the microstructure of MAPEA and APEA concrete. The results showed the use of high composition of an artificial aggregate resulted inferior strength on the concrete and 3% MAPEA in the concrete mix was highest compressive strength than other content. The modification of APEA (MAPEA) concrete increased its strength due to its surface roughness. However, the interfacial zone cracking was still found and decreased the strength of MAPEA concrete especially when it was age 28 days.

  1. Prediction of concrete compressive strength considering humidity and temperature in the construction of nuclear power plants

    Kwon, Seung Hee; Jang, Kyung Pil [Department of Civil and Environmental Engineering, Myongji University, Yongin (Korea, Republic of); Bang, Jin-Wook [Department of Civil Engineering, Chungnam National University, Daejeon (Korea, Republic of); Lee, Jang Hwa [Structural Engineering Research Division, Korea Institute of Construction Technology (Korea, Republic of); Kim, Yun Yong, E-mail: [Structural Engineering Research Division, Korea Institute of Construction Technology (Korea, Republic of)


    Highlights: • Compressive strength tests for three concrete mixes were performed. • The parameters of the humidity-adjusted maturity function were determined. • Strength can be predicted considering temperature and relative humidity. - Abstract: This study proposes a method for predicting compressive strength developments in the early ages of concretes used in the construction of nuclear power plants. Three representative mixes with strengths of 6000 psi (41.4 MPa), 4500 psi (31.0 MPa), and 4000 psi (27.6 MPa) were selected and tested under various curing conditions; the temperature ranged from 10 to 40 °C, and the relative humidity from 40 to 100%. In order to consider not only the effect of the temperature but also that of humidity, an existing model, i.e. the humidity-adjusted maturity function, was adopted and the parameters used in the function were determined from the test results. A series of tests were also performed in the curing condition of a variable temperature and constant humidity, and a comparison between the measured and predicted strengths were made for the verification.

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

    Zhang, Zuhua; Wang, Hao


    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.

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

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


    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...

  4. Prediction of Compressive Strength of Concrete Using Artificial Neural Network and Genetic Programming

    Palika Chopra; Rajendra Kumar Sharma; Maneek Kumar


    An effort has been made to develop concrete compressive strength prediction models with the help of two emerging data mining techniques, namely, Artificial Neural Networks (ANNs) and Genetic Programming (GP). The data for analysis and model development was collected at 28-, 56-, and 91-day curing periods through experiments conducted in the laboratory under standard controlled conditions. The developed models have also been tested on in situ concrete data taken from literature. A comparison o...

  5. Influence of Incorporating Fluoroapatite Nanobioceramic on the Compressive Strength and Bioactivity of Glass Ionomer Cement

    Khaghani M


    Full Text Available Statement of Problem: In order to increase the performance of glass ionomer cement, it is reinforced with metal powders, short fibers, bioceramics and other materials. Fluoroapatite(Ca10(PO46F2 is found in dental enamel and is usually used in dental materials due to its good chemical and physical properties. Objectives: In this study, the effects of the addition of synthesized fluoroapatite nanoceramic on the compressive strength and bioactivity of glass ionomer cement were investigated. Materials and Methods: The synthesized fluoroapatite nanoceramic particles (~ 70 nm were incorporated into as-prepared glass ionomer powder and were characterized using X-ray diffraction (XRD, Fourier transform infrared spectroscopy (FTIR and scanning electron microscopy (SEM. Moreover, the compressive strength values of the modified glass ionomer cements with 0, 1, 3 and 5 wt% of fluoroapatite were evaluated. Results: Results showed that glass ionomer cement containing 3 wt%fluoroapatite nanoparticles exhibited the highest compressive strength (102.6± 4 compared to the other groups, including control group. Furthermore, FTIR and SEM investigations indicated that after soaking the glass ionomer cement- 3 wt% fluoroapatite composite in the simulated body fluid solution, the intensity of O-H, P-O and C-O absorption bands increased as a result of the formation of apatite layer on the surface of the sample, and the rather flat and homogeneous surface of the cement became more porous and inhomogeneous. Conclusions: Addition of synthesized nano-fluoroapatite to as-prepared glass ionomer cement enhanced the compressive strength as well as nucleation of the calcium phosphate layer on the surface of the composite. This makes it a good candidate for dentistry and orthopedic applications.

  6. Mesoscopic Numerical Computation of Compressive Strength and Damage Mechanism of Rubber Concrete

    Z. H. Xie


    Full Text Available Evaluations of both macroscopic and mesoscopic strengths of materials have been the topic of a great deal of recent research. This paper presents the results of a study, based on the Walraven equation of the production of a mesoscopic random aggregate structure containing various rubber contents and aggregate sizes. On a mesoscopic scale, the damage mechanism in the rubber concrete and the effects of the rubber content and aggregate-mortar interface on the rubber concrete’s compressive resistance property were studied. The results indicate that the random aggregate structural model very closely approximates the experimental results in terms of the fracture distribution and damage characteristics under uniaxial compression. The aggregate-mortar interface mechanical properties have a substantial impact on the test sample’s strength and fracture distribution. As the rubber content increases, the compressive strength and elastic modulus of the test sample decrease proportionally. This paper presents graphics of the entire process from fracture propagation to structural failure of the test piece by means of the mesoscopic finite-element method, which provides a theoretical reference for studying the damage mechanism in rubber concrete and performing parametric calculations.

  7. Effect of chlorhexidine gluconate on porosity and compressive strength of a glass ionomer cement

    Luana Mafra MARTI

    Full Text Available INTRODUCTION:For presenting wide antibacterial activity, chlorhexidine (CHX has been extensively used in dentistry and can be easily incorporated into the glass ionomer cement (GIC and consequently released into the oral cavity.AIM: The aim of this study was porosity and compression strength of a GIC, that was added to different concentrations of CHX.MATERIAL AND METHOD: Specimens were prepared with GIC (Ketac Molar Esaymix and divided into 4 groups according to the concentration of CHX: control, 0.5% and 1% and 2% (n = 10. For analysis of pores specimens were fractured with the aid of hammer and chisel surgical, so that the fracture was performed in the center of the specimens, dividing it in half and images were obtained from a scanning electron microscope (SEM analyzed in Image J software. The compressive strength test was conducted in a mechanical testing machine (EMIC - Equipment and Testing Systems Ltd., Joseph of the Pines, PR, Brazil. Statistical analysis was performed by ANOVA, Tukey test. Significance level of 5%.RESULT: No statistically significant changes between the study groups was observed both for the number of pores as well as for the compressive strength.CONCLUSION: The use of GIC associated with CHX gluconate 1% and 2% is the best option to be used in dental practice.

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

    H. S. Zhang


    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.

  9. Modeling of Hydration, Compressive Strength, and Carbonation of Portland-Limestone Cement (PLC Concrete

    Xiao-Yong Wang


    Full Text Available Limestone is widely used in the construction industry to produce Portland limestone cement (PLC concrete. Systematic evaluations of hydration kinetics, compressive strength development, and carbonation resistance are crucial for the rational use of limestone. This study presents a hydration-based model for evaluating the influences of limestone on the strength and carbonation of concrete. First, the hydration model analyzes the dilution effect and the nucleation effect of limestone during the hydration of cement. The degree of cement hydration is calculated by considering concrete mixing proportions, binder properties, and curing conditions. Second, by using the gel–space ratio, the compressive strength of PLC concrete is evaluated. The interactions among water-to-binder ratio, limestone replacement ratio, and strength development are highlighted. Third, the carbonate material contents and porosity are calculated from the hydration model and are used as input parameters for the carbonation model. By considering concrete microstructures and environmental conditions, the carbon dioxide diffusivity and carbonation depth of PLC concrete are evaluated. The proposed model has been determined to be valid for concrete with various water-to-binder ratios, limestone contents, and curing periods.

  10. Prediction of compression strength of high performance concrete using artificial neural networks

    Torre, A.; Garcia, F.; Moromi, I.; Espinoza, P.; Acuña, L.


    High-strength concrete is undoubtedly one of the most innovative materials in construction. Its manufacture is simple and is carried out starting from essential components (water, cement, fine and aggregates) and a number of additives. Their proportions have a high influence on the final strength of the product. This relations do not seem to follow a mathematical formula and yet their knowledge is crucial to optimize the quantities of raw materials used in the manufacture of concrete. Of all mechanical properties, concrete compressive strength at 28 days is most often used for quality control. Therefore, it would be important to have a tool to numerically model such relationships, even before processing. In this aspect, artificial neural networks have proven to be a powerful modeling tool especially when obtaining a result with higher reliability than knowledge of the relationships between the variables involved in the process. This research has designed an artificial neural network to model the compressive strength of concrete based on their manufacturing parameters, obtaining correlations of the order of 0.94.

  11. Influence of ultrasonic setting on compressive and diametral tensile strengths of glass ionomer cements

    Terezinha Jesus Esteves Barata


    Full Text Available The aim of this study was to assess the influence of ultrasonic wave propagation on the compressive (CS and diametral tensile (DTS strengths of glass ionomer cements (GICs. Three variables were evaluated: conventional GICs, ultrasonic excitation and storage time (1 hour, 24 hours and 7 days. Bovine teeth molds were used for simulating a clinical ultrasonic excitation. The data were submitted to three-way ANOVA and Tukey tests (P < 0.05. All the tested conventional GICs presented an increase in strength from 1 hour to 7 days for CS and DTS. Ultrasonic excitation resulted in a statistically significant increase in the CS, but showed no statistically significant difference in the DTS. Regardless the GICs tested the increase in strength was maturation time-dependent for all groups.

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

    Huai-Shuai Shang


    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.

  13. Strength and failure behaviour of spark plasma sintered steel-zirconia composites under compressive Loading

    Krueger, L.; Decker, S.; Ehinger, D. [Institute of Materials Engineering, TU Bergakademie Freiberg (Germany); Ohser-Wiedemann, R.; Martin, S.; Martin, U.; Seifert, H.J. [Institute of Materials Science, TU Bergakademie Freiberg (Germany)


    Several composites, consisting of a metastable austenitic steel matrix and varying amounts of MgO partially stabilized zirconia particles (Mg-PSZ), were produced through spark plasma sintering (SPS). Compression tests were carried out at room temperature in a wide range of strain rate (4 . 10{sup -4} s{sup -1}, 2 . 10{sup -3} s{sup -1}, 10{sup -1} s{sup -1}, 1 s{sup -1}, 10{sup 2} s{sup -1}). In conjunction with subsequent microstructural investigations, the mechanical material behaviour was clarified. All composites showed a good ductility and a high strength. The strength increased with an increase of the ceramic content and with higher strain rates. Both, the martensitic transformation of the steel matrix and of the ceramic particles, could be proved at all strain rates. In this study no significant influence of the strain rate on the amount of transformed ceramic could be detected while the steel matrix showed less {alpha}'-martensite after compression at rising strain rates. Local material failure occurred around 0.3 true compressive strain depending on the applied strain rate and the amount of the Mg-PSZ powder. The main reason for the damage is the relatively weak ceramic-ceramic interface within the ceramic clusters. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  14. 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

    Hidayat Irpan


    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.

  15. 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

    Hidayat, Irpan; Siauwantara, Alice


    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.

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

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


    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.

  17. A Study of the Efficiency of High-strength, Steel, Cellular-core Sandwich Plates in Compression

    Johnson, Aldie E , Jr; Semonian, Joseph W


    Structural efficiency curves are presented for high-strength, stainless-steel, cellular-core sandwich plates of various proportions subjected to compressive end loads for temperatures of 80 F and 600 F. Optimum proportions of sandwich plates for any value of the compressive loading intensity can be determined from the curves. The efficiency of steel sandwich plates of optimum proportions is compared with the efficiency of solid plates of high-strength steel and aluminum and titanium alloys at the two temperatures.

  18. Zeolite-silver-zinc nanoparticles: Biocompatibility and their effect on the compressive strength of mineral trioxide aggregate

    Samiei, Mohammad; Ghasemi, Negin; Asl-Aminabadi, Naser; Divband, Baharak; Golparvar-Dashti, Yasamin


    Background This study was carried out to evaluate the biocompatibility of zeolite-silver-zinc (Ze-Ag-Zn) nanoparticles and their effect on the compressive strength of Mineral Trioxide Aggregate (MTA). Material and Methods Biocompatibility was evaluated by an MTT assay on the pulmonary adenocarcinoma cells with 0.05, 0.1, 0.25, 0.5, 1 and 5 mg/mL concentrations of Ze-Ag-Zn. For compressive strength test, four groups containing 15 stainless-steel cylinders with an internal diameter of 4 and a height of 6 mm were prepared and MTA (groups 1 and 2) or MTA + 2% Ze-Ag-Zn (groups 3 and 4) were placed in the cylinders. The compressive strength was evaluated using a universal testing machine 4 days after mixing in groups 1 and 3, and 21 days after mixing in groups 2 and 4. Results There was no significant difference between cytotoxicity of different concentrations. The highest (52.22±18.92 MPa) and lowest (19.57±5.76 MPa) compressive strength were observed in MTA group after 21 days and in MTA + 2% Ze-Ag-Zn group after four days, respectively. The effect of time and 2% Ze-Ag-Zn on the compressive strength were significant (P<0.05). Mixing MTA with Ze-Ag-Zn significantly reduced and passage of time from day four to 21 significantly increased the compressive strength. Conclusions Mixing MTA with 2% Ze-Ag-Zn had an adverse effect on the compressive strength of MTA, but this combination had no cytotoxic effects. Key words:Compressive strength, Cytotoxicity, Mineral Trioxide Aggregate, Nanoparticle, Zeolite-Silver-Zinc. PMID:28298974

  19. In-Situ Welding Carbon Nanotubes into a Porous Solid with Super-High Compressive Strength and Fatigue Resistance


    Carbon nanotube (CNT) and graphene-based sponges and aerogels have an isotropic porous structure and their mechanical strength and stability are relatively lower. Here, we present a junction-welding approach to fabricate porous CNT solids in which all CNTs are coated and welded in situ by an amorphous carbon layer, forming an integral three-dimensional scaffold with fixed joints. The resulting CNT solids are robust, yet still highly porous and compressible, with compressive strengths up to 72...

  20. Compressive Strength Properties of Natural Gas Hydrate Pellet by Continuous Extrusion from a Twin-Roll System

    Yun-Hoo Lee; Bong-Hwan Koh; Heung Soo Kim; Myung Ho Song


    This study investigates the compressive strength of natural gas hydrate (NGH) pellet strip extruded from die holes of a twin-roll press for continuous pelletizing (TPCP). The lab-scale TPCP was newly developed, where NGH powder was continuously fed and extruded into strip-type pellet between twin rolls. The system was specifically designed for future expansion towards mass production of solid form NGH. It is shown that the compressive strength of NGH pellet strip heavily depends on parameters...

  1. Effect Of Crumb Rubber On Compressive Strength Of Fly Ash Based Geopolymer Concrete

    Azmi Ahmad Azrem


    Full Text Available This study explores the effect of different percentage of crumb rubber on compressive strength of fly ash based geopolymer concrete. This research attempted to produce rubberized geopolymer concrete as an environmentally friendly, lightweight and durable product. Crumb rubber with ranged size from 73 μm to 375 μm was used in order to replace fine aggregates in geopolymer concrete. The replacements of crumb rubber were 0%, 5%, 10%, 15% and 20% in the fly ash based geopolymer concrete. The ratio of fly ash to alkaline activator was 2.5 and the ratio of Na2SiO3 to NaOH was fixed at 2.0. After the curing process, the strengths of the samples were tested on days 7 and 28. The results show that there is a reduction in all compressive strength for crumb rubber mixture, but still higher than normal rubberized concrete. Rubberized geopolymer concrete is a suitable solution in some non structural applications.

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

    Prabhat Ranjan Prem; B H Bharatkumar; Nagesh R Iyer


    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.

  3. Comparative study on compressive strength of Self cured SCC and Normally cured SCC

    Ms. Akanksha A. Patil


    Full Text Available Curing is the process of maintaining proper moisture content particularly within 28 days to promote optimum cement hydration immediately after placement. Self-compacting concrete is made up of admixture i.e. superplasticizer. In recent years, self-compacting concrete (SCC has gained wide use for placement in congested reinforced concrete structures with difficult casting conditions. Also various curing methods are adopted in the construction industry especially for vertical structures, inaccessible areas s.a. high rise buildings, water scarce areas etc. In such structures conventional curing is not practically possible in most of the cases. But we need efficient curing which improves the strength and durability of concrete. In the present work, comparison of compressive strength of normally cured SCC and SCC cured with self curing material i.e. wax based, white pigmented, membrane forming concrete curing compound has been done. This study is investigating that weather the use of self curing compound is economical or not in remote areas of water without compromising with the compressive strength of concrete.

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

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


    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.

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

    Ortega, J. M.


    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.

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

    Alexandre Costa Reis BRITO


    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.

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

    Bali Ika; Kushartomo Widodo; Jonathan


    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 c...

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

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


    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.

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

    Ahmadian Khoshemehr Leila


    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.

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

    Yu Chang-Li


    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.

  11. Long-Term Isothermal Aging Effects on Carbon Fabric-Reinforced PMR-15 Composites: Compression Strength

    Bowles, Kenneth J.; Roberts, Gary D.; Kamvouris, John E.


    A study was conducted to determine the effects of long-term isothermal thermo-oxidative aging on the compressive properties of T-650-35 fabric reinforced PMR-15 composites. The temperatures that were studied were 204, 260, 288, 316, and 343 C. Specimens of different geometries were evaluated. Cut edge-to-surface ratios of 0.03 to 0.89 were fabricated and aged. Aging times extended to a period in excess of 15,000 hours for the lower temperature runs. The unaged and aged specimens were tested in compression in accordance with ASTM D-695. Both thin and thick (plasma) specimens were tested. Three specimens were tested at each time/temperature/geometry condition. The failure modes appeared to be initiated by fiber kinking with longitudinal, interlaminar splitting. In general, it appears that the thermo-oxidative degradation of the compression strength of the composite material may occur by both thermal (time-dependent) and oxidative (weight-loss) mechanisms. Both mechanisms appear to be specimen-thickness dependent.

  12. Development of ultra-lightweight slurries with high compressive strength for use in oil wells

    Suzart, J. Walter P. [Halliburton Company, Houston, TX (United States); Farias, A.C. [PETROBRAS S.A., Rio de Janeiro, RJ (Brazil); Ribeiro, Danilo; Fernandes, Thiago; Santos, Reened [Halliburton Energy Services Aberdeen, Scotland (United Kingdom)


    Formations with low fracture gradients or depleted reservoirs often lead to difficult oil well cementing operations. Commonly employed cement slurries (14.0 to 15.8 lb/gal), generate an equivalent circulating density (ECD) higher than the fracture gradient and ultimately lead to formation damage, lost circulation and a decreased top of cement. Given the high price of oil, companies are investing in those and other wells that are difficult to explore. Naturally, lightweight cement slurries are used to reduce the ECD (10.0 to 14.0 lb/gal), using additives to trap water and stabilize the slurry. However, when the density reaches 11.0 lb/gal, the increase in water content may cause a change in characteristics. The focus of this study is extreme cases where it is necessary to employ ultra-lightweight cement slurries (5.5 to 10.0 lb/gal). Foamed slurries have been widely used, and the objective is to set an alternative by developing cement slurries containing uncompressible microspheres, aiming for a density of 7.5 lb/gal as well as high compressive strength. Another benefit in contrast to preparing foamed cement slurries is that there is no requirement for special equipment in the field. Routine laboratory tests such as fluid-loss control, sedimentation, thickening time, free water, compressive strength, and rheology (at room and high temperatures) were performed. Thus, it was concluded that the proposed cement slurries can be used in oil wells. (author)

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

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


    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.

  14. Influence of Curing Age and Mix Composition on Compressive Strength of Volcanic Ash Blended Cement Laterized Concrete

    Babafemi A.J.


    Full Text Available This study investigates the influence of curing age and mix proportions on the compressive strength of volcanic ash (VA blended cement laterized concrete. A total of 288 cubes of 100mm dimensions were cast and cured in water for 3, 7, 28, 56, 90 and 120 days of hydration with cement replacement by VA and sand replacement by laterite both ranging from 0 to 30% respectively while a control mix of 28-day target strength of 25N/mm2 (using British Method was adopted. The results show that the compressive strength of the VA-blended cement laterized concrete increased with the increase in curing age but decreased as the VA and laterite (LAT contents increased. The optimum replacement level was 20%LAT/20%VA. At this level the compressive strength increased with curing age at a decreasing rate beyond 28 days. The target compressive strength of 25N/mm2 was achieved for this mixture at 90 days of curing. VA content and curing age was noted to have significant effect (α ≤ 0.5 on the compressive strength of the VA-blended cement laterized concrete.

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

    Sherif El-Gamal


    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.

  16. Determination of Uniaxial Compressive Strength of Ankara Agglomerate Considering Fractal Geometry of Blocks

    Coskun, Aycan; Sonmez, Harun; Ercin Kasapoglu, K.; Ozge Dinc, S.; Celal Tunusluoglu, M.


    The uniaxial compressive strength (UCS) of rock material is a crucial parameter to be used for design stages of slopes, tunnels and foundations to be constructed in/on geological medium. However, preparation of high quality cores from geological mixtures or fragmented rocks such as melanges, fault rocks, coarse pyroclastic rocks, breccias and sheared serpentinites is often extremely difficult. According to the studies performed in literature, this type of geological materials may be grouped as welded and unwelded birmocks. Success of preparation of core samples from welded bimrocks is slightly better than unwelded ones. Therefore, some studies performed on the welded bimrocks to understand the mechanical behavior of geological mixture materials composed of stronger and weaker components (Gokceoglu, 2002; Sonmez et al., 2004; Sonmez et al., 2006; Kahraman, et al., 2008). The overall strength of bimrocks are generally depends on strength contrast between blocks and matrix; types and strength of matrix; type, size, strength, shape and orientation of blocks and volumetric block proportion. In previously proposed prediction models, while UCS of unwelded bimrocks may be determined by decreasing the UCS of matrix considering the volumetric block proportion, the welded ones can be predicted by considering both UCS of matrix and blocks together (Lindquist, 1994; Lindquist and Goodman, 1994; Sonmez et al., 2006 and Sonmez et al., 2009). However, there is a few attempts were performed about the effect of blocks shape and orientation on the strength of bimrock (Linqduist, 1994 and Kahraman, et al., 2008). In this study, Ankara agglomerate, which is composed of andesite blocks and surrounded weak tuff matrix, was selected as study material. Image analyses were performed on bottom, top and side faces of cores to identify volumetric block portions. In addition to the image analyses, andesite blocks on bottom, top and side faces were digitized for determination of fractal

  17. Dynamics of unconfined spherical flames

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


    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.

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

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


    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.

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

    Vaishali Sahu


    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.

  20. Repeatability and Reproducibility of Compression Strength Measurements Conducted According to ASTM E9

    Luecke, William E.; Ma, Li; Graham, Stephen M.; Adler, Matthew A.


    Ten commercial laboratories participated in an interlaboratory study to establish the repeatability and reproducibility of compression strength tests conducted according to ASTM International Standard Test Method E9. The test employed a cylindrical aluminum AA2024-T351 test specimen. Participants measured elastic modulus and 0.2 % offset yield strength, YS(0.2 % offset), using an extensometer attached to the specimen. The repeatability and reproducibility of the yield strength measurement, expressed as coefficient of variations were cv(sub r)= 0.011 and cv(sub R)= 0.020 The reproducibility of the test across the laboratories was among the best that has been reported for uniaxial tests. The reported data indicated that using diametrically opposed extensometers, instead of a single extensometer doubled the precision of the test method. Laboratories that did not lubricate the ends of the specimen measured yield stresses and elastic moduli that were smaller than those measured in laboratories that lubricated the specimen ends. A finite element analysis of the test specimen deformation for frictionless and perfect friction could not explain the discrepancy, however. The modulus measured from stress-strain data were reanalyzed using a technique that finds the optimal fit range, and applies several quality checks to the data. The error in modulus measurements from stress-strain curves generally increased as the fit range decreased to less than 40 % of the stress range.

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

    Sair Kahraman; Michael Alber


    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%.

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

    Waldemir Rodrigues


    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.

  3. Compressive Strength Properties of Natural Gas Hydrate Pellet by Continuous Extrusion from a Twin-Roll System

    Yun-Hoo Lee


    Full Text Available This study investigates the compressive strength of natural gas hydrate (NGH pellet strip extruded from die holes of a twin-roll press for continuous pelletizing (TPCP. The lab-scale TPCP was newly developed, where NGH powder was continuously fed and extruded into strip-type pellet between twin rolls. The system was specifically designed for future expansion towards mass production of solid form NGH. It is shown that the compressive strength of NGH pellet strip heavily depends on parameters in the extrusion process, such as feeding pressure, pressure ratio, and rotational speed. The mechanism of TPCP, along with the compressive strength and density of pellets, is discussed in terms of its feasibility for producing NGH pellets in the future.

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

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


    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.

  5. Characterization of compression strength of granite-epoxy composites using design of experiments

    Antonio Piratelli-Filho


    Full Text Available This paper presents a processing study of the polymer matrix composite (PMC developed with an epoxy polymeric matrix reinforced with particulate ceramic granite. This PMC composite has been reported to be used as structural parts of machine tools and Coordinate Measuring Machines due to its superior vibration damping characteristics and reduced processing cycle over cast iron. The investigated processing variables were epoxy content and particle size and the mechanical characterization was carried out by compressive tests. Rejects of granite with particle size smaller than 500 µm were prepared by crushing, milling and classification operations. The powder was mixed with different compositions of epoxy resin, between 15 and 20% in weight. An experiment was planned and executed according to the Factorial design technique using two variables at two levels. The obtained cylindrical samples were submitted to compressive strength tests and the results showed a maximum resistance of 114.23 MPa at 20 wt. (% epoxy, value close to that of the literature.

  6. A Numerical Study on the Edgewise Compression Strength of Sandwich Structures with Facesheet-Core Disbonds

    Bergan, Andrew C.


    Damage tolerant design approaches require determination of critical damage modes and flaw sizes in order to establish nondestructive evaluation detection requirements. A finite element model is developed to assess the effect of circular facesheet-core disbonds on the strength of sandwich specimens subjected to edgewise compressive loads for the purpose of predicting the critical flaw size for a variety of design parameters. Postbuckling analyses are conducted in which an initial imperfection is seeded using results from a linear buckling analysis. Both the virtual crack closure technique (VCCT) and cohesive elements are considered for modeling disbond growth. Predictions from analyses using the VCCT and analyses using cohesive elements are in good correlation. A series of parametric analyses are conducted to investigate the effect of core thickness and material, facesheet layup, facesheet-core interface properties, and curvature on the criticality of facesheet-core disbonds of various sizes. The results from these analyses provide a basis for determining the critical flaw size for facesheet-core disbonds subjected to edgewise compression loads and, therefore, nondestructive evaluation flaw detection requirements for this configuration.

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

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


    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.

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

    Ramin Hosseini Kupaei


    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.

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

    ZhenYa Liu; JingYu Liu; QingZhi Wang; JianKun Liu


    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.

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

    S.H. Adnan


    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.

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

    于昌利; LEE Joo-sung



  12. Structural strength of cancellous specimens from bovine femur under cyclic compression

    Kaori Endo


    Full Text Available The incidence of osteoporotic fractures was estimated as nine million worldwide in 2000, with particular occurrence at the proximity of joints rich in cancellous bone. Although most of these fractures spontaneously heal, some fractures progressively collapse during the early post-fracture period. Prediction of bone fragility during progressive collapse following initial fracture is clinically important. However, the mechanism of collapse, especially the gradual loss of the height in the cancellous bone region, is not clearly proved. The strength of cancellous bone after yield stress is difficult to predict since structural and mechanical strength cannot be determined a priori. The purpose of this study was to identify whether the baseline structure and volume of cancellous bone contributed to the change in cancellous bone strength under cyclic loading. A total of fifteen cubic cancellous bone specimens were obtained from two 2-year-old bovines and divided into three groups by collection regions: femoral head, neck, and proximal metaphysis. Structural indices of each 5-mm cubic specimen were determined using micro-computed tomography. Specimens were then subjected to five cycles of uniaxial compressive loading at 0.05 mm/min with initial 20 N loading, 0.3 mm displacement, and then unloading to 0.2 mm with 0.1 mm displacement for five successive cycles. Elastic modulus and yield stress of cancellous bone decreased exponentially during five loading cycles. The decrease ratio of yield stress from baseline to fifth cycle was strongly correlated with bone volume fraction (BV/TV, r = 0.96, p < 0.01 and structural model index (SMI, r = − 0.81, p < 0.01. The decrease ratio of elastic modulus from baseline to fifth cycle was also correlated with BV/TV (r = 0.80, p < 0.01 and SMI (r = − 0.78, p < 0.01. These data indicate that structural deterioration of cancellous bone is associated with bone strength after yield stress. This study suggests that

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

    Bilgehan, Mahmut


    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


    W.S.B. Dwandaru


    Full Text Available As the world is growing rapidly, people need better building materials such as mortar. The aim of this research is to determine the effect of adding silver nanoparticle solution towards the porosity and compressive strength of mortar. This research was started by making silver nanoparticle solution from nitrate silver (AgNO3. The solution is then characterized using Uv-Vis spectrophotometer. 5 mM silver nanoparticle is added in the process of mortar production with volume variation of the silver nanoparticle solution. The porosity, compressive strength, and the content of mortar were determined by digital scale, universal testing machine, and X-ray diffraction, respectively. For silver nanoparticle solution volumes of (in mL 0, 5, 10, 15, 20, and 25 the porosity obtained are (in % 20.38, 19.48, 19.42, 18.9, 17.8, and 17.5, respectively. The best increase in compressive strength is obtained for (in MPa 29,068, 29,308, and 31,385, with nanoparticle solution volumes of (in mL 5, 10, and 15   Keywords: mortar, silver nanoparticle, compressive strength

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

    Dowling, Adam H


    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.




    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.

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

    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: [Advanced Cement-Based Materials Research Unit, Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand)


    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.

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

    Márta Kurutz


    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

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

    Kruszka Leopold


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

    ZHANG Biao; QIAN Fatang; DUAN Xinglong; WU Bolin


    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.

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

    Rolando, A.


    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.

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

    S. M. Alamgir Kabir


    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.

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

    Neela Deshpande


    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.

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

    Fareed Ahmed Memon


    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.

  5. In-Situ Welding Carbon Nanotubes into a Porous Solid with Super-High Compressive Strength and Fatigue Resistance

    Lin, Zhiqiang; Gui, Xuchun; Gan, Qiming; Chen, Wenjun; Cheng, Xiaoping; Liu, Ming; Zhu, Yuan; Yang, Yanbing; Cao, Anyuan; Tang, Zikang


    Carbon nanotube (CNT) and graphene-based sponges and aerogels have an isotropic porous structure and their mechanical strength and stability are relatively lower. Here, we present a junction-welding approach to fabricate porous CNT solids in which all CNTs are coated and welded in situ by an amorphous carbon layer, forming an integral three-dimensional scaffold with fixed joints. The resulting CNT solids are robust, yet still highly porous and compressible, with compressive strengths up to 72 MPa, flexural strengths up to 33 MPa, and fatigue resistance (recovery after 100,000 large-strain compression cycles at high frequency). Significant enhancement of mechanical properties is attributed to the welding-induced interconnection and reinforcement of structural units, and synergistic effects stemming from the core-shell microstructures consisting of a flexible CNT framework and a rigid amorphous carbon shell. Our results provide a simple and effective method to manufacture high-strength porous materials by nanoscale welding.

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

    Prahara, E.; Meilani


    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.

  7. Embedded NMR Sensor to Monitor Compressive Strength Development and Pore Size Distribution in Hydrating Concrete

    Floriberto Díaz-Díaz


    Full Text Available In cement-based materials porosity plays an important role in determining their mechanical and transport properties. This paper describes an improved low–cost embeddable miniature NMR sensor capable of non-destructively measuring evaporable water loss and porosity refinement in low and high water-to-cement ratio cement-based materials. The sensor consists of two NdFeB magnets having their North and South poles facing each other, separated by 7 mm to allow space for a Faraday cage containing a Teflon tube and an ellipsoidal RF coil. To account for magnetic field changes due to temperature variations, and/or the presence of steel rebars, or frequency variation due to sample impedance, an external tuning circuit was employed. The sensor performance was evaluated by analyzing the transverse magnetization decay obtained with a CPMG measurement from different materials, such as a polymer phantom, fresh white and grey cement pastes with different w/c ratios and concrete with low (0.30 and high (0.6 w/c ratios. The results indicated that the sensor is capable of detecting changes in water content in fresh cement pastes and porosity refinement caused by cement hydration in hardened materials, even if they are prepared with a low w/c ratio (w/c = 0.30. The short lifetime component of the transverse relaxation rate is directly proportional to the compressive strength of concrete determined by destructive testing. The r2 (0.97 from the linear relationship observed is similar to that obtained using T2 data from a commercial Oxford Instruments 12.9 MHz spectrometer.

  8. Effect of high temperature curing on the compressive strength of concrete incorporating large volumes of fly ash

    Rivera-Villarreal, R. [Universidad Autonoma de Nuevo Leon, Monterrey (Mexico)


    The effect of using different types of heat treatment on the compressive strength of concrete with and without large volumes of fly ash was studied. Curing of concrete is important to obtain a good quality concrete, but it is important to keep concrete from drying until the originally water-filled space in fresh cement paste has been filled to the desired extent by the products of hydration. In hot weather, high temperature promotes faster drying of concrete so a given degree of hydration is reached more rapidly than at lower temperatures. The provision of moist curing is advantageous because of a gradual gain in strength and because of reduced plastic shrinkage and drying shrinkage-cracking. The portland cement content in all the mixtures used in this study was 200 kg per cubic metre and the amount of fly ash varied from 0 to 33, 43, 50 and 56 per cent by mass of the total binder. A superplasticizer was used to obtain 200-220 mm slump. The compressive strength was tested at 3, 7, 14, 28, 56 days and at 6 months. Results showed that, using ASTM standard curing, the compressive strength of portland cement concrete made at 35 degrees C was reduced by about 12 per cent at 28 days compared to that of the concrete made at 23 degrees C. The AASHTO curing strength was found to be a bit higher than with the ASTM curing. The concrete made at 35 degrees C showed no loss of strength when continuous moist-curing was applied. The fly ash concrete mixtures that were cast at 35 degrees C were cured by covering them with membrane curing compounds and placed under ambient conditions. It was crucial to allow enough curing water to promote the pozzolanic reaction. The membrane curing did not allow the ingress of water to the concrete mass. 6 refs., 4 tabs., 13 figs.

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

    CHEN Yimin; ZHOU Shuangxi; ZHANG Wensheng


    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.

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

    Chandan Kumar


    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:

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

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


    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.

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



    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.

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

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


    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.

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

    Anjana Raut


    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.

  15. 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

    彭红涛; 张琪; 李乃胜; 王德发


    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

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

    Li, Wangnan; Cai, Hongneng; Li, Chao


    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.

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

    Forood Torabian Isfahani


    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.

  18. Compressive strength behaviour of low- and medium-strength concrete specimens confined with carbon fibres in defective implementation conditions: an experimental study

    M. Fernández-Cánovas


    Full Text Available This behaviour of low- and medium-strength concrete specimens confined with carbon fibre-reinforced polymer (CFRP was analysed in three loading cycles. In some cases, stress levels were achieved that produced intemal microcracks, which allowed residual rigidity and the behaviour of completely microcraked concrete specimens to be studied. The specimens were subsequently tested to compression to the fracture point. Specimens reinforced in accordance with no manufacturing defects (100% CFRP reinforcement and major manufacturing defects (50% CFRP reinforcement were assessed for effectiveness and behaviour of the confined elements in less than ideal conditions. Results show that confinement was higher in low-resistance concretes, that the behaviour of reinforced specimens was unaffected by defective implementation conditions and that the reinforced specimens were less rigid than the non-reinforced specimens when tested up to 40% of ultimate fracture strength.

  19. Evaluation of strength-enhancing factors of a ductile binder in direct compression of sodium bicarbonate and calcium carbonate powders.

    Mattsson, S; Nyström, C


    This study evaluated the effectiveness of a ductile binder in direct compression of sodium bicarbonate and calcium carbonate powders. Properties associated with both the binder and the compound were studied. The addition of binder materials, such as polyethylene glycols (PEGs) of differing molecular weights or microcrystalline cellulose, generally resulted in an increase in the axial tensile strength of the corresponding compacts. The increase in tablet strength was generally greater with the PEGs than with microcrystalline cellulose. The results indicate that the improvement in tablet strength caused by the binder is dependent on properties of both the binder and the compound. By utilising different methods it was established that the fracture during tablet strength testing mainly occurred around the compound particles. As a consequence of this, it appears that the ability of the binder to fill the voids between the compound particles is a determinative factor for increasing tablet strength. The binder appeared to have less effect when added to compounds that fragmented during compaction. Characteristics of the binder resulting in the greatest decrease in porosity, and thus the greatest increase in the tensile strength of the compound, included a high degree of plastic deformation with a limited elastic component and a small particle size. Obviously, the amount of binder added to the mixture also affected the results.

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

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


    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.

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

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


    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.

  2. Statistical Study on Cement-Soil Mixture Strength

    YU Zhiqiang; CAO Yonghua; YAN Shuwang


    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.

  3. 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.

    Dowling, Adam H


    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).

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

    S. S, Pathak


    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.

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

    İnce, İsmail; Fener, Mustafa


    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.

  6. Micro-computed tomography assisted distal femur metaphyseal blunt punch compression for determining trabecular bone strength in mice.

    Sankar, Uma; Pritchard, Zachary J; Voor, Michael J


    Shorter generation time and the power of genetic manipulation make mice an ideal model system to study bone biology as well as bone diseases. However their small size presents a challenge to perform strength measurements, particularly of the weight-bearing cancellous bone in the murine long bones. We recently developed an improved method to measure the axial compressive strength of the cancellous bone in the distal femur metaphysis in mice. Transverse micro-computed tomography image slices that are 7µm thick were used to locate the position where the epiphysis-metaphysis transition occurs. This enabled the removal of the distal femur epiphysis at the exact transition point exposing the full extent of metaphyseal trabecular bone, allowing more accurate and consistent measurement of its strength. When applied to a murine model system consisting of five month old male wild-type (WT) and Ca(2+)/calmodulin dependent protein kinase kinase 2 (CaMKK2) knockout (KO) Camkk2(-/-) mice that possess recorded differences in trabecular bone volume, data collected using this method showed good correlation between bone volume fraction and strength of trabecular bone. In combination with micro-computed tomography and histology, this method will provide a comprehensive and consistent assessment of the microarchitecture and tissue strength of the cancellous bone in murine mouse models.

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

    In-Mo Lee


    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.

  8. Theory of DDT in unconfined flames

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


    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.

  9. Experimental investigation and empirical modelling of FDM process for compressive strength improvement

    Anoop K. Sood


    Full Text Available Fused deposition modelling (FDM is gaining distinct advantage in manufacturing industries because of its ability to manufacture parts with complex shapes without any tooling requirement and human interface. The properties of FDM built parts exhibit high dependence on process parameters and can be improved by setting parameters at suitable levels. Anisotropic and brittle nature of build part makes it important to study the effect of process parameters to the resistance to compressive loading for enhancing service life of functional parts. Hence, the present work focuses on extensive study to understand the effect of five important parameters such as layer thickness, part build orientation, raster angle, raster width and air gap on the compressive stress of test specimen. The study not only provides insight into complex dependency of compressive stress on process parameters but also develops a statistically validated predictive equation. The equation is used to find optimal parameter setting through quantum-behaved particle swarm optimization (QPSO. As FDM process is a highly complex one and process parameters influence the responses in a non linear manner, compressive stress is predicted using artificial neural network (ANN and is compared with predictive equation.

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

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


    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.


    Zlatko Briševac


    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.

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

    Mashimo, Tsutomu, E-mail:; 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)


    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.

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

    Pudjisuryadi, P.


    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.


    V. P. Fetisov


    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.

  15. An experimental investigation into the damage resistance and compression-after-impact strength of T800H/3900-2

    Vietinghoff, H.; Poon, C.; Straznicky, P. V.; Gould, R.


    An experimental investigation was conducted into impact behavior of a Toray T800H/3900-2 material system, a system representative of the most recent generation of toughened graphite-epoxy composites selected for use in several new airframes. In the investigation, test specimens featuring quasi-isotropic and midplane symmetric layup with 24 plies were fabricated and impacted at five different impact energy levels, resulting in damage ranging from barely visible to severe. Damage was characterized using nondestructive and destructive inspection, including ultrasound and x-ray techniques, and the specimens were then compressively loaded to failure. The carefully controlled set of experiments resulted in a detailed three dimensional characterization of the damage induced in the selected laminate layup for a range of impact energies. Compression after impact testing resulted in a correlation of impact energy and damage area with residual compressive strength. The results will be used to calibrate and test the analytical prediction methods being developed as part of a project on impact resistance and tolerance of composite materials, and as reference data on the material system.

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

    Sergio Giovanny Valbuena Porras


    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.

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

    Ersoy Hakan


    Full Text Available


    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


    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

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

    João Alexandre Paschoalin Filho


    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.

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

    Piladaeng Nawarat


    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.

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

    KOU Shicong; C S Poon


    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.

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

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


    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.

  2. Influence of artificially-induced porosity on the compressive strength of calcium phosphate bone cements.

    Mouzakis, Dionysios; Zaoutsos, Stefanos Polymeros; Bouropoulos, Nikolaos; Rokidi, Stamatia; Papanicolaou, George


    The biological and mechanical nature of calcium phosphate cements (CPC's) matches well with that of bone tissues, thus they can be considered as an appropriate environment for bone repair as bone defect fillers. The current study focuses on the experimental characterization of the mechanical properties of CPCs that are favorably used in clinical applications. Aiming on evaluation of their mechanical performance, tests in compression loading were conducted in order to determine the mechanical properties of the material under study. In this context, experimental results occurring from the above mechanical tests on porous specimens that were fabricated from three different porous additives, namely albumin, gelatin and sodium alginate, are provided, while assessment of their mechanical properties in respect to the used porous media is performed. Additionally, samples reinforced with hydroxyapatite crystals were also tested in compression and the results are compared with those of the above tested porous CPCs. The knowledge obtained allows the improvement of their biomechanical properties by controlling their structure in a micro level, and finds a way to compromise between mechanical and biological response.

  3. Elevated Temperature, Residual Compressive Strength of Impact-Damaged Sandwich Structure Manufactured Out-of-Autoclave

    Grimsley, Brian W.; Sutter, James K.; Burke, Eric R.; Dixon, Genevieve D.; Gyekenyesi, Thomas G.; Smeltzer, Stanley S.


    Several 1/16th-scale curved sandwich composite panel sections of a 10 m diameter barrel were fabricated to demonstrate the manufacturability of large-scale curved sections using minimum gauge, [+60/-60/0]s, toughened epoxy composite facesheets co-cured with low density (50 kilograms per cubic meters) aluminum honeycomb core. One of these panels was fabricated out of autoclave (OoA) by the vacuum bag oven (VBO) process using Cycom(Registered Trademark) T40-800b/5320-1 prepreg system while another panel with the same lay-up and dimensions was fabricated using the autoclave-cure, toughened epoxy prepreg system Cycom(Registered Trademark) IM7/977-3. The resulting 2.44 m x 2 m curved panels were investigated by non-destructive evaluation (NDE) at NASA Langley Research Center (NASA LaRC) to determine initial fabrication quality and then cut into smaller coupons for elevated temperature wet (ETW) mechanical property characterization. Mechanical property characterization of the sandwich coupons was conducted including edge-wise compression (EWC), and compression-after-impact (CAI) at conditions ranging from 25 C/dry to 150 C/wet. The details and results of this characterization effort are presented in this paper.

  4. Modeling and analysis of porosity and compressive strength of gradient Al2O3-ZrO2 ceramic filter using BP neural network

    Li Qiang


    Full Text Available BP neural network was used in this study to model the porosity and the compressive strength of a gradient Al2O3-ZrO2 ceramic foam filter prepared by centrifugal slip casting. The influences of the load applied on the epispastic polystyrene template (F, the centrifugal acceleration (v and sintering temperature (T on the porosity (P and compressive strength (σ of the sintered products were studied by using the registered three-layer BP model. The accuracy of the model was verified by comparing the BP model predicted results with the experimental ones. Results show that the model prediction agrees with the experimental data within a reasonable experimental error, indicating that the three-layer BP network based modeling is effective in predicting both the properties and processing parameters in designing the gradient Al2O3-ZrO2 ceramic foam filter. The prediction results show that the porosity percentage increases and compressive strength decreases with an increase in the applied load on epispastic polystyrene template. As for the influence of sintering temperature, the porosity percentage decreases monotonically with an increase in sintering temperature, yet the compressive strength first increases and then decreases slightly in a given temperature range. Furthermore, the porosity percentage changes little but the compressive strength first increases and then decreases when the centrifugal acceleration increases.

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

    Ali Arab; Roslan Ahmad; Zainal Arifin Ahmad


    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.

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

    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)


    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.

  7. Shape memory and transformation behavior of high strength 60NiTi in compression

    Kaya, I.


    This study investigates the transformation behavior of highly Ni-rich 60NiTi alloys after aging at 600 °C for 3 h. After 600 °C-3h aging, R-phase disappeared and alloy transformed in one step. The latent heats of austenite to martensite and martensite to austenite transformations were 13 Jg-1 and 16.4 Jg-1, respectively, for 600 °C-3h aged alloy. The elastic strain energy of 0.75 Jg-1 was obtained in aged alloy. The maximum recoverable transformation strain of 1.7% is obtained under 500 MPa in compression. The superelastic behavior was observed accompanied with a recoverable strain of 1.4%, even high stress level of 1000 MPa is applied.

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

    Y. Luna-Galiano


    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.

  9. Effects of altered crystalline structure and increased initial compressive strength of calcium sulfate bone graft substitute pellets on new bone formation.

    Urban, Robert M; Turner, Thomas M; Hall, Deborah J; Infanger, Susan I; Cheema, Naveed; Lim, Tae-Hong; Moseley, Jon; Carroll, Michael; Roark, Michael


    A new, modified calcium sulfate has been developed with a different crystalline structure and a compressive strength similar to many calcium phosphate materials, but with a resorption profile only slightly slower than conventional surgical-grade calcium sulfate. A canine bilateral defect model was used to compare restoration of defects treated with the modified calcium sulfate compared to treatment using conventional calcium sulfate pellets after 6, 13, and 26 weeks. The modified calcium sulfate pellets were as effective as conventional calcium sulfate pellets with regard to the area fraction and compressive strength of newly formed bone in the treated bone defects. Mechanical testing demonstrated that the initial compressive strength of the modified material was increased nearly three-fold compared to that of conventional surgical-grade calcium sulfate. This increase potentially allows for its use in a broader range of clinical applications, such as vertebral and subchondral defects.

  10. Novel tricalcium silicate/magnesium phosphate composite bone cement having high compressive strength, in vitro bioactivity and cytocompatibility.

    Liu, Wenjuan; Zhai, Dong; Huan, Zhiguang; Wu, Chengtie; Chang, Jiang


    Although inorganic bone cements such as calcium phosphate cements have been widely applied in orthopaedic and dental fields because of their self-setting ability, development of high-strength bone cement with bioactivity and biodegradability remains a major challenge. Therefore, the purpose of this study is to prepare a tricalcium silicate/magnesium phosphate (C3S/MPC) composite bone cement, which is intended to combine the excellent bioactivity of C3S with remarkable self-setting properties and mechanical strength of MPC. The self-setting and mechanical properties, in vitro induction of apatite formation and degradation behaviour, and cytocompatibility of the composite cements were investigated. Our results showed that the C3S/MPC composite cement with an optimal composition had compressive strength up to 87 MPa, which was significantly higher than C3S (25 MPa) and MPC (64 MPa). The setting time could be adjusted between 3 min and 29 min with the variation of compositions. The hydraulic reaction products of the C3S/MPC composite cement were composed of calcium silicate hydrate (CSH) derived from the hydration of C3S and gel-like amorphous substance. The C3S/MPC composite cements could induce apatite mineralization on its surface in SBF solution and degraded gradually in Tris-HCl solution. Besides, the composite cements showed good cytocompatibility and stimulatory effect on the proliferation of MC3T3-E1 osteoblast cells. Our results indicated that the C3S/MPC composite bone cement might be a new promising high-strength inorganic bioactive material which may hold the potential for bone repair in load-bearing site.

  11. Use of steel fibres recovered from waste tyres as reinforcement in concrete: pull-out behaviour, compressive and flexural strength.

    Aiello, M A; Leuzzi, F; Centonze, G; Maffezzoli, A


    The increasing amount of waste tyres worldwide makes the disposition of tyres a relevant problem to be solved. In the last years over three million tons of waste tyres were generated in the EU states [ETRA, 2006. Tyre Technology International - Trends in Tyre Recycling.]; most of them were disposed into landfills. Since the European Union Landfill Directive (EU Landfill, 1999) aims to significantly reduce the landfill disposal of waste tyres, the development of new markets for the tyres becomes fundamental. Recently some research has been devoted to the use of granulated rubber and steel fibres recovered from waste tyres in concrete. In particular, the concrete obtained by adding recycled steel fibres evidenced a satisfactory improvement of the fragile matrix, mostly in terms of toughness and post-cracking behaviour. As a consequence RSFRC (recycled steel fibres reinforced concrete) appears a promising candidate for both structural and non-structural applications. Within this context a research project was undertaken at the University of Salento (Italy) aiming to investigate the mechanical behaviour of concrete reinforced with RSF (recycled steel fibres) recovered from waste tyres by a mechanical process. In the present paper results obtained by the experimental work performed up to now are reported. In order to evaluate the concrete-fibres bond characteristics and to determine the critical fibre length, pull-out tests were initially carried out. Furthermore compressive strength of concrete was evaluated for different volume ratios of added RSF and flexural tests were performed to analyze the post-cracking behaviour of RSFRC. For comparison purposes, samples reinforced with industrial steel fibres (ISF) were also considered. Satisfactory results were obtained regarding the bond between recycled steel fibres and concrete; on the other hand compressive strength of concrete seems unaffected by the presence of fibres despite their irregular

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

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


    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.

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

    Fatih Yapıcı


    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.

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

    A.R. Gaifullin


    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

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

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


    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.

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

    Hernández, E. F.


    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.

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

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


    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.

  18. Influencing Factors of Compression Strength of Asphalt Mixture in Cold Region%寒区沥青混合料抗压强度影响因素

    韦佑坡; 马骉; 司伟


    针对寒区低温特点,对沥青混合料进行室内单轴压缩试验,分析温度、油石比、沥青种类和级配对混合料抗压强度的影响.结果表明,混合料抗压强度随温度的升高而降低;对比不同最大公称粒径的沥青混合料的抗压强度可知,SBR改性AC - 16混合料的抗压强度高于AC - 13;存在对应于抗压强度达到最大值时的最佳油石比,约在6.0%~7.0%之间;SBR改性沥青混合料的低温抗压性能明显优于l30#道路石油沥青混合料.混合料抗压强度值的对数与温度及油石比的关系符合二元一次函数关系.用SPSS相关分析方法分析各影响因素对混合料抗压特性的影响程度可知,温度和沥青种类对抗压强度影响较大.%Aimed at the climate feature of low temperature in cold region, the influence of temperature, asphalt-aggregate ratio, asphalt types and aggregate gradation on the compression strength of asphalt mixture was analysed by indoor uniaxial compression test. The results show that (1) the compressive strength become lower with the increase of temperature; (2) based on comparing strengths of asphalt mixture in different nominal maximum sizes of aggregate, the compression strength of SBR modified AC-16 asphalt mixture is better than that of AC-13; (3) corresponds to maximum compressive strength of asphalt mixture, there exists the optimum asphalt-aggregate ratio between 6. 0% -7. 0% ; (4) the compressive properties of SBR modified asphalt mixture is superior to that of paving asphalt mixture No. 100 under low temperature; (5) the relation of the logarithm of the compression strength with temperature and asphalt-aggregate ratio approximately obeys two-variable linear function. The results also revealed that temperature and asphalt types have greatly affect on compression strength of asphalt mixture among influencing factors based on correspondence analysis of SPSS.

  19. Compression versus first shock strength in indirect-drive NIF implosions

    Landen, Otto; Celliers, Peter; Robey, Harry; Berzak Hopkins, Laura; Haan, Steve; Lindl, John


    NIF indirect-drive cryogenic DT implosions have used a variety of multi-shock pulse shapes to implode capsules with in-flight fuel adiabats ranging from 1.5 to 4. At a given design adiabat, the stagnated convergence ratio and fuel areal density inferred from the neutron image size and the ratio of downscattered to primary neutron yield shows variability that can be ascribed to shot-to-shot differences in shock timing, ablator dopant level and duration of coast phase. However, the locus of maxima in convergence and fuel areal density is shown to depend principally on the first shock strength that is measured by separate shock timing shots. No clear secondary dependence on hot electron preheat levels that vary by orders of magnitude between designs is observed. The scalings, which include all NIF indirect-drive implosions shot to date, are fitted using an analytic 1D implosion model. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA27344.

  20. HSDP II Drill Core: Preliminary Rock Strength Results and Implications to Flank Stability, Mauna Kea Volcano

    Thompson, N.; Watters, R. J.; Schiffman, P.


    Selected portions of the 3-km HSDP II core were tested to provide unconfined rock strength data from hyaloclastite alteration zones and pillow lavas. Though the drilling project was not originally intended for strength purpose, it is believed the core can provide unique rock strength insights into the flank stability of the Hawaiian Islands. The testing showed that very weak rock exists in the hyaloclastite abundant zones in the lower 2-km of the core with strength dependent on the degree of consolidation and type of alteration. Walton and Schiffman identified three zones of alteration, an upper incipient alteration zone (1080-1335m), a smectitic zone (1405-1573m) and a lower palagonitic zone from about 1573 m to the base of the core. These three zones were sampled and tested together with pillow lava horizons for comparison. Traditional cylindrical core was not available as a consequence of the entire core having been split lengthwise for archival purposes. Hence, point load strength testing was utilized which provides the unconfined compressive strength on irregular shaped samples. The lowest unconfined strengths were recorded from incipient alteration zones with a mean value of 9.5 MPa. Smectitic alteration zones yielded mean values of 16.4 MPa, with the highest measured alteration strengths from the palagonite zones with a mean value of 32.1 MPa. As anticipated, the highest strengths were from essentially unaltered lavas with a mean value of 173 MPa. Strength variations of between one to two orders of magnitude were identified in comparing the submarine hyaloclastite with the intercalated submarine lavas. The weakest zones within the hyaloclastites may provide horizons for assisting flank collapse by serving as potential thrust zones and landslide surfaces.

  1. Factors affecting early compressive strength of alkali activated fly ash (OPC-free concrete

    Palomo, A.


    Full Text Available This paper presents the findings of experimental research into the chief characteristics of a new type of concrete made solely with alkali activated fly ash (AAFA: i.e., free of ordinary Portland cement (OPC. The results of testing to determine specific properties of the fresh concrete and the development of its mechanical strength showed that most of the factors that affect the manufacture and final properties of Portland cement concrete (water/cement ratio, curing conditions, etc. also impact the preparation and final quality of this new material. A number of parameters specific to AAFA concrete (nature and concentration of alkali present in the system were also explored to determine their role in the setting and hardening process.Este trabajo presenta los resultados de una investigación experimental llevada a cabo para evaluar las principales características de un nuevo tipo de hormigón fabricado solamente con ceniza volante activada alcalinamente (AAFA; es decir, sin cemento Portland comercial (OPC. Los resultados de los ensayos realizados para determinar las propiedades específicas del hormigón fresco y el desarrollo de resistencias mecánicas mostraron que la mayoría de los factores que afectan al proceso de fabricación y a las propiedades finales de los hormigones de cemento Portland (relación agua/cemento, condiciones de curado, etc. también afectan a la preparación y calidad final de estos nuevos materiales. También fueron estudiados otros parámetros específicos de los hormigones de AAFA (la naturaleza y concentración del álcali presente en el sistema para determinar su papel en el proceso de fraguado y endurecimiento.

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

    Sakthieswaran Natarajan


    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.

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

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


    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.

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

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


    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

  5. Description of Primary Education 1st Grade Students' Forms of Holding a Pencil as well as Their Grip and Compression Strengths

    Temur, Turan


    This study aimed to examine how first grade students in primary education held and gripped a pencil and their compressive strength using a descriptive research method. The participants of the research comprises first grade students attending a private school in the city center of Ankara (n=79). All of the four different sections in this private…

  6. 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

    宫家良; 姚文杰


    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.

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

    Asokan Pappu


    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

  8. Arrows of time in unconfined systems

    Barbour, Julian


    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.


    Zhenjun He; Yupu Song


    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.

  10. 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

    Iftekhair Ibnul Bashar


    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.

  11. 基于水灰比准则的水泥土无侧限抗压强度预测%On forecasting of unconfined compressive strength of cement soil based on water cement ratio criterion

    张帅; 钱峰



  12. Hybrid microscaffold-based 3D bioprinting of multi-cellular constructs with high compressive strength: A new biofabrication strategy

    Tan, Yu Jun; Tan, Xipeng; Yeong, Wai Yee; Tor, Shu Beng


    A hybrid 3D bioprinting approach using porous microscaffolds and extrusion-based printing method is presented. Bioink constitutes of cell-laden poly(D,L-lactic-co-glycolic acid) (PLGA) porous microspheres with thin encapsulation of agarose-collagen composite hydrogel (AC hydrogel). Highly porous microspheres enable cells to adhere and proliferate before printing. Meanwhile, AC hydrogel allows a smooth delivery of cell-laden microspheres (CLMs), with immediate gelation of construct upon printing on cold build platform. Collagen fibrils were formed in the AC hydrogel during culture at body temperature, improving the cell affinity and spreading compared to pure agarose hydrogel. Cells were proven to proliferate in the bioink and the bioprinted construct. High cell viability up to 14 days was observed. The compressive strength of the bioink is more than 100 times superior to those of pure AC hydrogel. A potential alternative in tissue engineering of tissue replacements and biological models is made possible by combining the advantages of the conventional solid scaffolds with the new 3D bioprinting technology. PMID:27966623

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

    González-Taboada, I.


    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

  14. Stochastic uncertainty analysis for unconfined flow systems

    Liu, Gaisheng; Zhang, Dongxiao; Lu, Zhiming


    A new stochastic approach proposed by Zhang and Lu (2004), called the Karhunen-Loeve decomposition-based moment equation (KLME), has been extended to solving nonlinear, unconfined flow problems in randomly heterogeneous aquifers. This approach is on the basis of an innovative combination of Karhunen-Loeve decomposition, polynomial expansion, and perturbation methods. The random log-transformed hydraulic conductivity field (InKS) is first expanded into a series in terms of orthogonal Gaussian standard random variables with their coefficients obtained as the eigenvalues and eigenfunctions of the covariance function of InKS- Next, head h is decomposed as a perturbation expansion series ??A(m), where A(m) represents the mth-order head term with respect to the standard deviation of InKS. Then A(m) is further expanded into a polynomial series of m products of orthogonal Gaussian standard random variables whose coefficients Ai1,i2(m)...,im are deterministic and solved sequentially from low to high expansion orders using MODFLOW-2000. Finally, the statistics of head and flux are computed using simple algebraic operations on Ai1,i2(m)...,im. A series of numerical test results in 2-D and 3-D unconfined flow systems indicated that the KLME approach is effective in estimating the mean and (co)variance of both heads and fluxes and requires much less computational effort as compared to the traditional Monte Carlo simulation technique. Copyright 2006 by the American Geophysical Union.

  15. Experimental Study on Unconfined Vapor Cloud Explosion

    毕明树; ABULITI; Abudula


    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.

  16. 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

    李海鹏; 朱元林; 潘卫东


    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.

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

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


    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.

  18. Compressive and diametral tensile strength of glass ionomer cements Resistência à compressão e à tração diametral de cimentos de ionômero de vidro

    Eduardo Bresciani; Terezinha de Jesus Esteves Barata; Ticiane Cestari Fagundes; Akimi Adachi; Marina Martins Terrin; Maria Fidela de Lima Navarro


    The aim of this study was to compare, in different periods of time, the compressive and diametral tensile strength of a traditional high viscous glass ionomer cement: Fuji IX (GC Corporation), with two new Brazilian GIC's: Vitro-Molar (DFL) and Bioglass R (Biodinamica), all indicated for the Atraumatic Restorative Treatment (ART) technique. Fifteen disk specimens (6.0mm diameter x 3.0mm height) for the diametral tensile strength (DTS) test and fifteen cylindrical specimens (6.0mm diameter x 1...

  19. Unconfined Aquifer Flow Theory - from Dupuit to present

    Mishra, Phoolendra K


    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 ...

  20. Modeling Decomposition of Unconfined Rigid Polyurethane Foam



    The decomposition of unconfined rigid polyurethane foam has been modeled by a kinetic bond-breaking scheme describing degradation of a primary polymer and formation of a thermally stable secondary polymer. The bond-breaking scheme is resolved using percolation theory to describe evolving polymer fragments. The polymer fragments vaporize according to individual vapor pressures. Kinetic parameters for the model were obtained from Thermal Gravimetric Analysis (TGA). The chemical structure of the foam was determined from the preparation techniques and ingredients used to synthesize the foam. Scale-up effects were investigated by simulating the response of an incident heat flux of 25 W/cm{sup 2} on a partially confined 8.8-cm diameter by 15-cm long right circular cylinder of foam which contained an encapsulated component. Predictions of center, midradial, and component temperatures, as well as regression of the foam surface, were in agreement with measurements using thermocouples and X-ray imaging.

  1. Modeling Decomposition of Unconfined Rigid Polyurethane Foam



    The decomposition of unconfined rigid polyurethane foam has been modeled by a kinetic bond-breaking scheme describing degradation of a primary polymer and formation of a thermally stable secondary polymer. The bond-breaking scheme is resolved using percolation theory to describe evolving polymer fragments. The polymer fragments vaporize according to individual vapor pressures. Kinetic parameters for the model were obtained from Thermal Gravimetric Analysis (TGA). The chemical structure of the foam was determined from the preparation techniques and ingredients used to synthesize the foam. Scale-up effects were investigated by simulating the response of an incident heat flux of 25 W/cm{sup 2} on a partially confined 8.8-cm diameter by 15-cm long right circular cylinder of foam that contained an encapsulated component. Predictions of center, midradial, and component temperatures, as well as regression of the foam surface, were in agreement with measurements using thermocouples and X-ray imaging.

  2. Nitrate reduction in an unconfined sandy aquifer

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


    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...... processes of O2 and NO3- occur at rates that are fast compared to the rate of downward water transport. Nitrate-contaminated groundwater contains total contents of dissolved ions that are two to four times higher than in groundwater derived from the forested area. The persistence of the high content...... of total dissolved ions in the NO3- free anoxic zone indicates the downward migration of contaminants and that active nitrate reduction is taking place. Nitrate is apparently reduced to N2 because both nitrite and ammonia are absent or found at very low concentrations. Possible electron donors...

  3. Effects of augmented trunk stabilization with external compression support on shoulder and scapular muscle activity and maximum strength during isometric shoulder abduction.

    Jang, Hyun-jeong; Kim, Suhn-yeop; Oh, Duck-won


    The aim of the present study was to investigate the effects of augmented trunk stabilization with external compression support (ECS) on the electromyography (EMG) activity of shoulder and scapular muscles and shoulder abductor strength during isometric shoulder abduction. Twenty-six women volunteered for the study. Surface EMG was used to monitor the activity of the upper trapezius (UT), lower trapezius (LT), serratus anterior (SA), and middle deltoid (MD), and shoulder abductor strength was measured using a dynamometer during three experimental conditions: (1) no external support (condition-1), (2) pelvic support (condition-2), and (3) pelvic and thoracic supports (condition-3) in an active therapeutic movement device. EMG activities were significantly lower for UT and higher for MD during condition 3 than during condition 1 (p Shoulder abductor strength was significantly higher during condition 3 than during condition 1 (p shoulder abduction and increasing shoulder abductor strength.

  4. Predicting model on ultimate compressive strength of Al2O3-ZrO2 ceramic foam filter based on BP neural network

    Yu Jingyuan


    Full Text Available In present study, BP neural network model was proposed for the prediction of ultimate compressive strength of Al2O3-ZrO2 ceramic foam filter prepared by centrifugal slip casting. The inputs of the BP neural network model were the applied load on the epispastic polystyrene template (F, centrifugal acceleration (v and sintering temperature (T, while the only output was the ultimate compressive strength (σ. According to the registered BP model, the effects of F, v, T on σ were analyzed. The predicted results agree with the actual data within reasonable experimental error, indicating that the BP model is practically a very useful tool in property prediction and process parameter design of the Al2O3-ZrO2 ceramic foam filter prepared by centrifugal slip casting.

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

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


    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.

  6. Molecular-Level Study of the Effect of Prior Axial Compression/Torsion on the Axial-Tensile Strength of PPTA Fibers


    strength and appre- ciable changes in the associated probability density function. Keywords effect of compression and torsion, Kevlar , PPTA, 1. Introduction The work described in the present manuscript concerns p- phenylene terephthalamide (PPTA) polymeric fibers such as Kevlar ...Engineering Innovation Building, Clemson, SC 29634-0921; and C.-F. Yen and B.A. Cheeseman, Army Research Laboratory—Weapons & Materials Research Directorate


    皮文山; 周红标; 胡金平


    Aimed at the main facts of concrete compressive strength, a multi-factor 3-layer BP network model was set up using BP artificial neural network for the prediction of concrete compressive strength, with cement, blast furnace slag, fly ash, water, superplasticizer, coarse aggregate, fine aggregate and age as the model input parameters, and concrete compressive strength as the model output parameter. The results show that the maximum predicted error of BP neural network model is less than 20 , the average error is 5.99 ,and the concrete compressive strength artificial neural network model has higher prediction accuracy.%在阐述BP人工神经网络原理的基础上,针对影响强度的主要因素,建立了多因子混凝土抗压强度3层BP网络模型,以每立方混凝土中水泥、高炉矿渣粉、粉煤灰、水、减水剂、粗集料和细集料含量及置放天数作为模型输入参数,混凝土抗压强度值作为模型的输出,对混凝土抗压强度进行了预测.实验结果表明:所建BP神经网络混凝土抗压强度预测模型最大误差绝对值都小于20%,平均误差为7.33%,模型具有较高预测精度.

  8. Effect of niobium and carbon on microstructure and compressive yield strength of as cast ESR Fe-8.5Al alloy

    Baligidad, R.G.; Dutta, A.; Rao, A.S.


    The effect of niobium (1.5 and 3.5 wt-%) addition on the microstructure and mechanical properties of as cast ESR Fe-8.5Al-0.1C alloy has been studied. Alloys were prepared by a combination of air induction melting with flux cover (AIMFC) and electroslag remelting (ESR). As cast ESR alloys were characterised using an optical microscope, a scanning electron microscope (SEM) and an electron probe microanalyser (EPMA). Compression tests were carried out on as cast ESR alloy samples at temperatures up to 800{sup o}C. Addition of 1.5 wt-% Nb to Fe-8.5Al-0.1C alloy resulted in a marginal improvement in the compressive yield strength at test temperatures up to 1073 K, whereas addition of 3.5 wt-% Nb significantly improved the strength. This significant improvement in the room and high temperature compressive strength may be attributed to solid solution strengthening as well as precipitation hardening by the presence of fine and higher volume fractions of niobium and niobium carbide precipitates, in contrast to the relatively soft Fe{sub 3}AlC{sub 0.5} precipitates present in the Fe-8.5Al-0.1C alloy. (author)


    孙晓雪; 赵吉坤; 张永兴; 杜林勇


    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.

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

    Taehyoung Kim


    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

  11. Modeling Contamination of Shallow Unconfined Aquifers Through Infiltration Beds

    Ostendorf, D. W.


    We model the transport of a simply reactive contaminant through an infiltration bed and underlying shallow, one-dimensional, unconfined aquifer with a plane, steeply sloping bottom in the assumed absence of dispersion and downgradient dilution. The effluent discharge and ambient groundwater flow under the infiltration beds are presumed to form a vertically mixed plume marked by an appreciable radial velocity component in the near field flow region. The near field analysis routes effluent contamination as a single linear reservoir whose output forms a source plane for the one-dimensional, far field flow region downgradient of the facility; the location and width of the source plane reflect the relative strengths of ambient flow and effluent discharge. We model far field contaminant transport, using an existing method of characteristics solution with frame speeds modified by recharge, bottom slope, and linear adsorption, and concentrations reflecting first-order reaction kinetics. The near and far field models simulate transport of synthetic detergents, chloride, total nitrogen, and boron in a contaminant plume at the Otis Air Force Base sewage treatment plant in Barnstable County, Massachusetts, with reasonable accuracy.


    Adewunmi Omobolaji ADENAIYA


    Full Text Available The need for environmental sustainability calls for a radical change from the use of synthetic wood preservatives which persist in the environment even after wood has been taken out of service. There has therefore been a growing interest in the development of efficacious biocides from plants, prompting the exploration of castor seed oil as a potential wood antifungal in this study due to its reported antimicrobial properties. Thus, this study aimed at evaluating the resistance of castor oil treated P. caribaea wood against two strains of wood basidiomycetes. Five trees of Pinus caribaea were harvested at Shasha Forest Reserve, Osun State. Wood samples were obtained from the top, middle and base of the trees. The samples were conditioned and treated with four formulated fungicides prepared from mechanically extracted oil of castor seeds. The treated and control samples were inoculated with Sclerotium rolfsii (Brown rot and Ganoderma lucidum (White rot for 24 weeks. Parameters such as oil yield, preservative absorption, weight loss and compressive strength of the treated wood samples were determined. ANOVA was used in analyzing the data generated. Results show that the oil yield of the seed of the plant is 41.75%. The preservative absorption of the wood ranged between 114.85 - 277.12 (Kgm-3 , weight loss (1.36 - 15.85% and MCS// (33.05 - 48.35N/mm2 . Sampling height and preservative concentration significantly influenced weight loss of the wood (p<0.05. The 30% preservative concentration performed best, having the least weight loss (1.71% and 1.61% and highest MCS// (47.06N/mm2 and 44.65N/mm2 after exposure to S. rolfsii and G. lucidum, respectively. The brown rot (4.12% was more virulent than the white rot (3.66% on the basis of wood weight loss, however, the MCS// results indicated otherwise. It is concluded that castor seed oil is effective in protecting wood against white and brown rot fungi.

  13. Experimental Study on the Residual Strength of Coal Under Low Confinement

    Gao, Fuqiang; Kang, Hongpu


    In underground coal mining, coal rib failure of longwall entries is almost certain due to the relative weakness of coal and the presence of high mining-induced stresses. To maintain the coal's capability of sustaining large loads after failure and substantial deformation, it is crucial to understand its post-peak behavior and subsequently, its residual strength. In this study, triaxial compression tests were performed on a total of 51 coal specimens that were classified into two groups based on the existence of calcite grains. Particular emphasis was given to evaluating the residual strength of the coal specimens. It was found that the presence of calcite grains has significant effect on the brittleness of the coal. Coal specimens containing calcite grains have lower frictional strength than specimens without calcite grains. The tests demonstrated that splitting is completely suppressed when the confinement exceeds 10 % of the coal's unconfined compressive strength. The Coulomb and Hoek-Brown failure criteria satisfactorily fit the coals' the peak strength data over the entire confining stress range. The Hoek-Brown failure criterion satisfactorily fits the residual strength data. The parameter m for residual strength is significantly greater than that of the peak strength for both groups of coal. It was also found that as the confinement increases, the increase in residual strength is greater than the increase in peak strength.

  14. 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



    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.

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

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


    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.

  16. Strength and deformation characteristics of carbonated reactive magnesia treated silt soil

    CAI Guang-hua; LIU Song-yu; DU Yan-jun; ZHANG Ding-wen; ZHENG Xu


    A series of unconfined compression tests (UCTs) were conducted to investigate the effects of content of reactive magnesia (MgO) and carbonation time on the engineering properties including apparent characteristics, stress-strain relation, and deformation and strength characteristics of reactive MgO treated silt soils. The soils treated with reactive MgO at various contents were subjected to accelerated carbonation for different periods of time and later, UCTs were performed on them. The results demonstrate that the reactive MgO content and carbonation time have remarkable influences on the aforementioned engineering properties of the soils. It is found that with the increase in reactive MgO content, the unconfined compressive strength (qu) increases at a given carbonation time (<10 h), whereas the water content and amounts of crack of the soils decrease. A threshold content of reactive MgO exists at approximately 25% and a critical carbonation time exists at about 10 h for the development ofqu. A simple yet practical strength-prediction model, by taking into account two variables of reactive MgO content and carbonation time, is proposed to estimatequ of carbonated reactive MgO treated soils. A comparison of the predicated values of qu with the measured ones indicates that the proposed model has satisfactory accuracy.

  17. Nematode Locomotion in Unconfined and Confined Fluids

    Bilbao, Alejandro; Vanapalli, Siva; Blawzdziewicz, Jerzy


    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...

  18. Nematode locomotion in unconfined and confined fluids

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


    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.

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

    HAO Chengwei; DENG Min; MO Liwu; LIU Kaiwei


    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.

  20. 三种复合树脂贴面的抗压实验研究%Experimental Study on Compressive Strength of Three Kinds of Composite Resin Veneer



    Objective: To study the compressive strength of 3 kinds of composite resin veneer so as to provide a scientific basis forclinical application. Methods: Thirty anterior teeth were just extracted and then, their labial surfaces of crowns were restoredwith 3 kinds of light cured composite resin veneer. The most stress and compressive strength of the 3 kinds of prosthesiswere tested. Results: The compressive strength of Tetric ceram was higher than those of Charisma and Durafill (P <0.05).There was no significant difference between Charisma and Durafill (P>0.05). Conclusion: The Tetric ceram is a kind ofexcellent prosthetic material as veneer constraction.%目的:对3种复合树脂贴面的抗压强度进行实验比较,为临床应用提供依据。方法:采用新鲜的30颗人离体前牙,以3种不同光固化树脂贴面,测试每组试件的最大压力和抗压强度。结果:瓷化树脂较卡瑞斯玛、杜拉菲勒的抗压强度为优(P<O.05)。卡瑞斯玛与杜拉菲勒之间差异无显著性(P>0.05)。结论:瓷化树脂具有良好特性及美观效果,可作为一种较好的贴面材料。

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

    McAllister, Iain Wilson; Crichton, George C


    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...

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

    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

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

    Alva Edy Tontowi


    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.

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

    Mohammad Doustmohammadi


    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.

  5. 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

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


    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)

  6. Study on compressive strength of ancient brick wall of the mosque in Qiqihar city%基于齐齐哈尔市清真寺古砖墙抗压强度研究



    以齐齐哈尔市清真寺为对象,进行了古代砖墙的抗压强度检测.根据检测结果,得出抗压强度沿墙体高度的变化趋势;给出古代砖的抗压强度与现在普通烧结砖的抗压强度的对比.%As object, the compressive strength test of the ancient brick wall of Mosque in qiqihaer city has been done .According to the test results , it is concluded that the variation trends of compressive strength along the wall height and has given the compressive strength of ancient brick compared with the strength of the now common sintered brick.

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

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


    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.

  8. Deflagration-to-Detonation Transition in Unconfined Media

    Poludnenko, Alexei; Gardiner, Thomas; Oran, Elaine


    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.

  9. Experimental Investigation on Compressive Strength of Cast-in-situ Phosphogypsum%现浇磷石膏抗压强度的试验研究

    张华刚; 吴琴; 贾晓飞; 陈红鸟; 马克俭; 赵敏; 谢光亚


    On the basis of previous researches and engineering practice,total 52 cubic and 33 prismatic phosphogypsum specimens were made by a water/cement ratio of 0 .43 ,where nine mix proportions for phosphogypsum were involved according to the different mixture of phosphorous slag micro-powder,hy-drated lime,cement,water reducer and retarder.Furthermore,total 8 one-second scale wall models using the 7th mix proportion were also made for axial compression tests.Experimental results combined with the earlier research show that the compressive strength of cast-in-situ phosphogypsum wall is about 0.68 times the prism compressive strength,while the latter is about 0.8 times cube compressive strength.Additional-ly,the recommended value of material weight is around 14.0 kN/m3 to 15.0 kN/m3 .Based on the reliabil-ity analysis of engineering examples,the material partial coefficient of cast-in-situ phosphogypsum is rec-ommended as 1 .9 ,and the standard value and design value of phosphogypsum compressive strength are given according to the mix proportion examined in this paper.%在改性研究及工程实践基础上,对磷石膏掺入磷渣微粉、熟石灰、水泥、减水剂和缓凝剂确定了9种材料配合比,按水灰比为0.43制作了52个立方体试件和33个棱柱体试件进行抗压强度试验,还按第7种配合比制作8个比例为1/2的墙体模型进行轴心受压试验,结合前期研究结果确定现浇磷石膏的抗压强度值.结果表明,棱柱体抗压强度约为立方体抗压强度的0.8倍,墙体中的现浇磷石膏抗压强度约为棱柱体抗压强度的0.68倍,材料容重可取14.0~15.0 kN/m3.以工程实例为基础进行了可靠度分析,建议现浇磷石膏的材料分项系数取1.9,并给出了按本文材料配合比的抗压强度标准值及设计值.

  10. Comparison of the compression strength of human vertebral bodies with the mass and density of apatite: a study by 31P NMR spectroscopy.

    Brown, C E; Srinivasan, R; Sigmann, P; Myklebust, J B; Battocletti, J H


    The force needed to fracture individual human thoracic and lumbar vertebral bodies is compared with the mass and density of apatite. 31P NMR spectrometry was used to quantify the apatite, because it permits the mineral content of bone to be determined noninvasively with minimal nonspecific interference from the organic matrix or from variations in composition of the marrow. Experiments were performed with bones of similar structure and function from a single individual with no history of trabecular fractures, to compensate for the effects of the other variables that affect bone strength. The coefficient of correlation between compression strength and the volume density (i.e., g/cm3) of apatite was 0.95. The correlation of strength with the mass (i.e., grams) of apatite in a vertebral body also was reasonably good, r = 0.82, but correlations with areal density (i.e., g/cm2) and linear density (i.e., g/cm) were much poorer.

  11. Stability of Strength and Deformation Characteristics of Expanded Polystyrene (EPS within the Time of Long-Term Investigation of Creep Strain under Permanent Compressive Loading

    Saulius VAITKUS


    Full Text Available The results of investigation of strength (s10 %, scr and deformability (E characteristics of expanded polystyrene specimens are presented. The results are based on the short-term compression in the organization of long-term creep study. For the experiments identical specimens stored 5 years at ambient temperature (23 ±2 °C and relative humidity (50 ±5 % as well specimens after removal long-term loading were used. There were established, that difference between experimental values of stress and initial modulus of tested expanded polystyrene specimens with confidence probability P = 90 % (on-sided test is negligible (random.DOI:

  12. 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

    陈云龙; 马菊荣; 刘海峰; 宋建夏


    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%。

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

    A. Kurzawa


    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.

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

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


    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.

  15. Hydraulic Tomography to Characterization of Heterogeneity of Unconfined Aquifers

    Zhu, J.; Yeh, T. J.


    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

  16. 欧特克发布基于BIM的概念设计软件--Autodesk Infrastructure Modeler 2012%Investigation of Stability of Axial Compressed Member of High Strength Steel


    One of the research emphases of application and investigation of high strength steel are laid on stability of axial compressed member. After analyzing stability of high strength steel and limitations of design method for stability of high strength steel analyzed, combined with the function of stability analysis of large finite element analysis software ANSYS and model test, stability for axial compressed members of high strength steel are researched, and formulae which parameter includes yield strength of material and slenderness ratio of member is put forward for calculation stability coefficient of axial compressed member of high strength steel. Some important conclusions are arrived at. The research is significant for application and investigation of high strength steel in future.%欧特克有限公司宣布,欧特克建筑信息模型(BIM)基础设施产品组合新增面向概念设计的Autodesk Infrastructure Modeler 2012软件。基于BIM的基础设施产品组合主要用于规划、设计、建设和管理更具可持续性的基础设施。新产品将与2012版欧特克基础设施设计套件配套,可帮助业内专业人士提高效率,并消除工作过程中产生的浪费。

  17. Test of correlation between compressive strength and resistivity of fiber reinforced concrete%纤维混凝土抗压强度与电阻率相关性试验研究

    元成方; 赵卓; 李晓红


    选取了6种常用的工程纤维,开展纤维混凝土电阻率测试与抗压强度试验,研究分析纤维品种及龄期对混凝土抗压强度和电阻率的影响,建立纤维混凝土抗压强度和电阻率的定量关系。研究结果表明:掺入不同品种的纤维后,混凝土的抗压强度和电阻率均有不同程度提高,纤维自身的弹性模量和抗拉强度对混凝土抗压强度影响显著。混凝土抗压强度随电阻率的增高而增大,二者具有良好的非线性关系。根据混凝土电阻率测试结果,可对混凝土的强度发展趋势进行预测,也可基于混凝土抗压强度测试结果,间接评价混凝土的混凝土损伤程度和钢筋锈蚀速率。%The resistivity test and compressive strength test of fiber reinforced concrete were conducted,and the effects of fiber varieties and age on the concrete compressive strength and resistivity were studied. Then,the quantitative correlation between compressive strength and electrical resistivity of the fiber concrete was established. The results show that the compressive strength and resistivity of different varieties fiber concrete are improved in different degree,and the effect of elastic modulus and tensile strength of the fiber itself on compressive strength of concrete is significantly. The compressive strength of concrete increases with the increase of resistivity,which the two have good nonlinear correlation. According to the test results of concrete resistivity,the compressive strength development of concrete can be predicted,also the damage degree of concrete or steel corrosion rate can be evaluated base on the test results of concrete strength.

  18. Dynamic triaxial compression experiments on Cor-Tuf specimens

    Mondal, Alex B.

    A set of dynamic triaxial compression experiments at 50 MPa, 100 MPa, and 200 MPa confinement have been conducted with a modified Kolsky bar on cylindrical ultra high strength concrete Cor-Tuf specimens of diameter 19 mm and length of 12.7 mm. The experiment is composed of a hydrostatic phase which occurs at a quasi-static strain rate followed by a dynamic shear phase which occurs at a high strain rate. A set of 28 experiments were conducted at strain rates of 100 s-1 and 200 s-1. The experiments show that the fracture strength of the material increases under the test conditions. The specimens showed higher strength in the dynamic confined experiments than both the quasi-static TXC tests and the unconfined dynamic tests. The strength increase was attributed to specimen size difference and not a strain rate or confinement effect. Although the trend towards brittle ductile transition is observed the specimens were not tested in a high enough confinement for the phase change to occur.


    夏多田; 何明胜; 唐艳娟; 付小建; 石磊巍


    保温砌模轻质混凝土空心砌块混合生土复合墙体结构是由聚苯乙烯颗粒( EPS)混合土为内芯、轻质陶粒混凝土砌块为外模组成的一种新型复合砌块砌体结构形式,具有保温、抗震和整体好的特性,非常适合村镇低层建筑。考虑不同的内芯材料强度和不同的砌筑砂浆强度,对9组复合砌块砌体抗压试件进行试验研究,分析内芯强度和砂浆强度对复合砌块砌体抗压强度的影响。试验结果表明:内芯材料强度对复合砌体抗压强度贡献最大,影响显著;砂浆强度对复合砌体抗压强度影响较小;空心砌块砌体的抗压强度明显低于复合砌块砌体的抗压强度。%The composite masonry of thermal-insulating lightweight concrete hollow block is a new type of structure with composite polystyrene ( EPS) soil as its inner core and the lightweight ceramsite concrete block as its external mould, because it makes the heat preservation and anti-seismic and integrity as a whole , suitable for buildings in village and town .Considering the different strength of filling materials and different strength of masonry mortar , compressive strength of 9 group specimens of composite block masonry was tested , analyzed the effects of different inner core strength and different mortar strength on the compressive strength of composite block masonry .The test results show that the inner core strength has the largest contribution to the compressive strength of composite masonry , whose influence is significant; mortar strength has weak effect on compressive strength of composite masonry; the compressive strength of hollow block masonry is markedly lower than that of composite block masonry .

  20. Spontaneous Transition of Turbulent Flames to Detonations in Unconfined Media

    Poludnenko, Alexei Y; Oran, Elaine S


    Deflagration-to-detonation transition (DDT) can occur in environments ranging from experimental and industrial systems to astrophysical thermonuclear (type Ia) supernovae explosions. Substantial progress has been made in explaining the nature of DDT in confined systems with walls, internal obstacles, or pre-existing shocks. It remains unclear, however, whether DDT can occur in unconfined media. Here we use direct numerical simulations (DNS) to show that for high enough turbulent intensities unconfined, subsonic, premixed, turbulent flames are inherently unstable to DDT. The associated mechanism, based on the nonsteady evolution of flames faster than the Chapman-Jouguet deflagrations, is qualitatively different from the traditionally suggested spontaneous reaction wave model, and thus does not require the formation of distributed flames. Critical turbulent flame speeds, predicted by this mechanism for the onset of DDT, are in agreement with DNS results.

  1. TNT Equivalency of Unconfined Aerosols of Propylene Oxide

    A. Apparao


    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:

  2. 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



    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

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

    Foad Changizi; Abdolhosein Haddad


    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.

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

    Cristina OLARESCU


    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.

  5. 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

    王甲春; 阎培渝


    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 .

  6. The strength/moisture relations and hydraulic conductivity of Mexican tepetate

    Nimlos, T.J. (Univ. of Montana, Missoula (USA)); Hillery P.A. (Environmental Information Center, Helena, MT (USA))


    Indurated soil material formed from volcanic-ash-flow tuff is widespread in the Pacific rim portions of Latin America. This material is called tepetate in Mexico where, in some areas, all soil overlying tepetate has been removed by erosion, leaving a barren landscape with a very slowly permeable surface that contributes to overland flow and flooding. Reclamation of this land involves ripping to break up the upper part of the tepetate or terracing to retain water so that it may infiltrate. Tepetate strength and hydraulic conductivity influence both treatments. The authors determined the change in tepetate strength with moisture. Unconfined compressive strength of eight typical samples was measured at four moisture contents. Strength declined with increasing moisture, especially in samples of high or moderate strength. These data suggest that tepetate of moderate or high strength should be reclaimed during the wet season, whereas low-strength tepetate can be reclaimed at any season. They also determined tepetate's saturated hydraulic conductivity; it varied from 1.5 {times} 10{sup {minus}7} to 36.0 {times} 10{sup {minus}7} m/s. These low values demonstrate the very slowly permeable nature of tepetate and account for the extensive erosion and flooding frequency.

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

    Omar I. Abdelkarim


    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.

  8. 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

    贾广测; 吴相豪; 朱涛


    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.

  9. 活性粉末混凝土疲劳后剩余抗压强度试验研究%Experimental study on residual compressive strength of RPC under fatigue loading

    余自若; 安明喆; 郑帅泉


    In order to investigate the evolution law of residual compressive strength for reactive powder concrete ( RPC) under fatigue loading, the fatigue tests were carried out.24 cylinders were cast for testing and divided into 3 groups.By measuring the compressive strength of some RPC specimens, the relationship between initial compressive strength and resonance frequency was established firstly.On that basis, the constant amplitude and two-stage amplitude fatigue tests were carried and the residual compressive strength of RPC specimens were measured after fatigue.Experimental results show that the attenuation of post-fatigue residual compressive strength of RPC decreased with increase of recycle ratio.On the other hand, the attenuation rate increased with increase of recycle ratio.An fitting formula about the attenuation of post-fatigue residual compressive strength and recycle ratio was deduced.The calculated values which come from fitting formula are in good agreement with measured values.%为研究经受疲劳荷载作用后活性粉末混凝土(RPC)的剩余抗压强度变化规律,对3组共24个RPC圆柱体试件,进行疲劳试验研究.通过静载试验建立RPC抗压强度和谐振频率之间的关系,推算出各疲劳试件的初始抗压强度;在此基础上,对RPC试件进行轴压单级和两级疲劳加载试验,并实测试件在疲劳荷载作用一定次数后的剩余抗压强度.实测结果表明:RPC在单级疲劳后剩余抗压强度的衰减率随循环寿命比的增大而减小,而衰减速率则随着循环寿命比的增大而增大.根据实测值得到RPC单级和两级疲劳加载后剩余抗压强度衰减率与循环寿命比之间关系的拟合公式,计算结果与实测结果吻合良好.

  10. Two-dimensional physical-based inversion of confined and unconfined aquifers under unknown boundary conditions

    Jiao, Jianying; Zhang, Ye


    An inverse method is developed to simultaneously estimate multiple hydraulic conductivities, source/sink strengths, and boundary conditions, for two-dimensional confined and unconfined aquifers under non-pumping or pumping conditions. The method incorporates noisy observed data (hydraulic heads, groundwater fluxes, or well rates) at measurement locations. With a set of hybrid formulations, given sufficient measurement data, the method yields well-posed systems of equations that can be solved efficiently via nonlinear optimization. The solution is stable when measurement errors are increased. The method is successfully tested on problems with regular and irregular geometries, different heterogeneity patterns and variances (maximum Kmax/Kmin tested is 10,000), and error magnitudes. Under non-pumping conditions, when error-free observed data are used, the estimated conductivities and recharge rates are accurate within 8% of the true values. When data contain increasing errors, the estimated parameters become less accurate, as expected. For problems where the underlying parameter variation is unknown, equivalent conductivities and average recharge rates can be estimated. Under pumping (and/or injection) conditions, a hybrid formulation is developed to address these local source/sink effects, while different types of boundary conditions can also exert significant influences on drawdowns. Local grid refinement near wells is not needed to obtain accurate results, thus inversion is successful with coarse inverse grids, leading to high computation efficiency. Furthermore, flux measurements are not needed for the inversion to succeed; data requirement of the method is thus not much different from that of interpreting classic well tests. Finally, inversion accuracy is not sensitive to the degree of nonlinearity of the flow equations. Performance of the inverse method for confined and unconfined aquifer problems is similar in terms of the accuracy of the estimated parameters

  11. 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

    徐晓; 崔智骁


    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.


    吴世莲; 陆林侦; 曹明国; 查光玉


    Objective To study the influences of three kinds of disinfection methods on compressive strength of oral gypsum models. Methods On physical multi - function experimental bench the compressive strength of oral gypsum models was tested after microwave disinfection, pressure steam sterilization and ultraviolet irradiation disinfection. Results The compressive strength of three kinds of gypsum models including plaster, dental stone, high strength dental stone treated by microwave disinfection was slightly lower than that of the control group, but the difference had no statistical significance (P > 0.05). In addition to the gypsum models of high strength dental stone, the compressive strength of the other two kinds of gypsum models treated by ultraviolet irradiation disinfection was slightly lower too. The compressive strength of three kinds of gypsum models treated by pressure steam sterilization was significantly lower than that of the control group. Differences between the two groups of data were statistically significant (P < 0. 01). Conclusion Disinfection by microwave heating and ultraviolet irradiation do not obviously affect the compressive strength of oral gypsum models, but disinfection by pressure steam sterilization obviously affect the compressive strength of oral gypsum models.%目的 研究三种消毒方法对口腔石膏模型压缩强度的影响.方法 采用物理多功能试验台,对微波消毒法、压力蒸汽灭菌法和紫外线照射法消毒后的口腔石膏模型压缩强度进行了测试.结果 微波消毒法处理后的熟石膏、硬石膏和超硬石膏模型等种类石膏模型的压缩强度均略低于对照组压缩强度,但两组数据差异没有显著统计学意义(p>0.05);紫外线照射消毒法除超硬石膏模型之外,对另两种模型压缩强度也略有降低.压力蒸汽灭菌处理后的三种石膏模型的压缩强度明显低于对照,两组数据比较差异有显著统计学意义(p<0.01).结论 微

  13. 基于 RBF 神经网络的变电站混凝土立柱抗压强度评定%Assessment of Compressive Strength of Substation Concrete Column Based on RBF Neural Network

    熊亮; 赵俊锴


    Assessment of compressive strength of substation concrete column is an important foundation of damage degree and bearing capacity of construction.An RBF neural network model (RBF-NN )is applied to assessing compressive strength of concrete by ultrasonic and rebound combined method.An experimental method is given for compressive strength of concrete test by ultrasonic and rebound combined method.It is proved that RBF-NN model has higher evaluation precision than that of regression calculation by experimental test and emulation analysis.%变电站混凝土立柱抗压强度的评定是判断变电站混凝土结构损伤程度、剩余承载力的重要依据。设计了一个 RBF 神经网络模型,将其应用于超声回弹综合法评定变电站混凝土立柱抗压强度,给出了用超声回弹法进行混凝土强度测试的方法。经试验测试和仿真分析表明,所提出的 RBF 神经网络比传统的回归计算方法具有更高的评估精度。

  14. 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

    何锦云; 王陆陆


    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.

  15. Analytic solutions for unconfined groundwater flow over a stepped base

    Fitts, Charles R.; Strack, Otto D. L.


    Two new exact solutions are presented for uniform unconfined groundwater flow over a stepped base; one for a step down in the direction of flow, the other for a step up in the direction of flow. These are two-dimensional solutions of Laplace's equation in the vertical plane, and are derived using the hodograph method and conformal mappings on Riemann surfaces. The exact solutions are compared with approximate one-dimensional solutions which neglect the resistance to vertical flow. For small horizontal hydraulic gradients typical of regional groundwater flow, little error is introduced by neglecting the vertical resistance to flow. This conclusion may be extended to two-dimensional analytical models in the horizontal plane, which neglect the vertical resistance to flow and treat the aquifer base as a series of flat steps.

  16. Physical model simulations of seawater intrusion in unconfined aquifer

    Tanapol Sriapai


    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.

  17. 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

    何锦云; 毛明明


    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.

  18. 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

    安芃芃; 刘文晓; 杨有海


    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

  19. 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

    刘思海; 侍克斌; 吴福飞


    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.


    方瑾; 郑双七


    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。

  1. 含水率对砖砌体抗压强度影响的试验研究%Water content effects on compression strength of brick masonry members

    韩冰; 王伟; 王元丰


    Bearing-capacity of Masonry will be influenced if soaked in flood, and it may even collapse.Therefore, it's necessary to investigate the effects of different water content on compression strength of masonry material to pursue rules how water content influences the characteristics of masonry material, and to determine rational strength of the material. In this paper, experiments are carried out to measure compression strength of brick masonry members under different soaking time. Through comparing their strength of the members with no soaking, soaking to 2 days, 7 days and 14 days, some rules of strength development of brick masonry soaked in water are acquired.%由于洪水浸泡,砌体结构的承载能力将会受到影响,甚至出现倒塌.为了掌握不同含水率对砖砌体结构强度的影响规律,确定浸泡后结构的承载能力,有必要对含水率影响砖砌体抗压强度进行研究.通过对不同浸泡时间的砖砌体试件的抗压强度进行测试,对比了不浸泡、浸泡2 d、7 d、14d砖砌体试件的抗压强度,得到了砖砌体试件抗压强度随浸泡时间的变化规律.

  2. 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

    张瑞敏; 柴寿喜; 魏厚振; 徐良


    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

  3. Modeling cross-hole slug tests in an unconfined aquifer

    Malama, Bwalya; Brauchler, Ralf; Bayer, Peter


    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 ...

  4. Modeling cross-hole slug tests in an unconfined aquifer

    Malama, Bwalya; Kuhlman, Kristopher L.; Brauchler, Ralf; Bayer, Peter


    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.

  5. Experimental Research on the Compressive Strength of Rammed Earth Using Penetration Method%贯入法检测夯土材料抗压强度试验研究



    To facilitate the field testing of material strength for rammed earth structures and utilize the existing equip -ment ,the penetration method was proposed as non-destructive test (NDT) method for rammed earth material .According to the penetration tests and the strength tests on rammed earth test blocks ,the relationship between penetration value and strength was investigated .The results indicate that there exists an exponential function between penetration value and test block strength .The special strength formula for measuring the strength of rammed earth material by mortar penetrometer can be obtained .From vertical compression test results of an earth wall ,it can be seen that the proposed method is relia-bile ,convenient ,and has good prospects .%为提高夯土建筑材料强度现场检测的便利性,利用现有仪器设备,提出将夯土材料贯入法作为材料强度的无损检测方法。分别对夯土试块进行贯入试验与强度试验,研究夯土材料贯入值与试块强度之间的规律。试验表明,材料贯入值与试块强度存在指数函数关系,可得到砂浆贯入仪测量夯土材料强度的无损检测专用公式。通过墙体实例测试,该方法可靠,便捷,具有较好的应用前景。

  6. Improvement of magnetic hysteresis loss, corrosion resistance and compressive strength through spark plasma sintering magnetocaloric LaFe11.65Si1.35/Cu core-shell powders

    Caiyin You


    Full Text Available 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.

  7. 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


    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。

  8. 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

    柴启辉; 杨世锋; 孙明权


    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

  9. 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

    陈锦; 李东庆; 邴慧; 邓友生


    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.

  10. Chemical Stabilisation of Sand Part IX: Orthophthalate type Unsaturated Polyester Resin for Inducing Fast setting Behaviour and High Strength

    B. P. Gupta


    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.

  11. Synthesis of Zinc Oxide Nanoparticles and Their Effect on the Compressive Strength and Setting Time of Self-Compacted Concrete Paste as Cementitious Composites

    Mohammad Reza Arefi


    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.

  12. 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

    孙浩; 许希武; 郭树祥


    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。


    璩继立; 赵冬雪; 李贝贝


    To improve the characteristics of the low Shanghai clay strength and easy destroy, the dispersed palm was mixed into Shanghai clay with different mass reinforcement ratio and aspect ratio to do unconfined compressive strength test and Brazilian splitting test, then the impact of reinforced conditions on the compressive strength and tensile strength was explored.The results showed that compared with plain soil, palm reinforced soil could increase the compressive strength and tensile strength of Shanghai clay. The most appropriate reinforcement ratio of compressive strength and tensile strength in test was 1.00%.The best palm length was 4 mm, the optimum aspect ratio was 1∶3.Compared with plain soil, the improved degree of tensile strength by reinforcement was higher than that of the compressive strength.Meanwhile it was analyzed the mechanism of raising the strength of palm reinforced soil.%为改良上海黏土强度低,易发生破坏的特性,将分散的棕榈片以不同质量加筋率、长宽比等加入上海黏土中进行抗压强度试验和巴西劈裂试验,来探究加筋条件对棕榈加筋土抗压强度和抗拉强度的影响。试验结果表明:与素土相比,棕榈加筋土可提高上海黏土的抗压强度和抗拉强度。抗压强度和抗拉强度最适宜的加筋率为1.00%,最佳棕榈长度为4 mm,最优长宽比为1∶3。相对于素土,加筋对抗拉强度的提高幅度高于抗压强度。同时对棕榈加筋土强度提高的机理进行分析。


    黄靓; 王辉; 陈胜云


    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。

  15. 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

    吴洁; 陈志宇; 仇亚非; 李宁; 郭长军


    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

  16. 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

    张涛; 刘松玉; 蔡国军


    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

  17. Modeling particulate self-healing materials and application to uni-axial compression

    Herbst, Olaf; Luding, Stefan


    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

  18. Compressive Strength of 2D-C/SiC Composite at High Temperature in Air%2D-C/SiC复合材料在空气中的高温压缩强度研究

    牛学宝; 张程煜; 乔生儒; 韩栋; 李玫


    研究了二维碳纤维增强碳化硅基复合材料(2 D-C/SiC)在空气介质中的高温压缩强度.材料采用1K T300碳纤维平纹布经叠层和缝合制成预制体为增强体,经等温化学气相浸渗制备而成.试样表面用化学气相沉积工艺沉积SiC涂层.测试方向为垂直于炭布叠层方向,测试温度为室温,700℃,1100℃和1300℃.使用扫描电子显微镜观察了材料的断口.结果表明:室温~700℃,2D-C/SiC的压缩强度随温度升高逐渐增大,温度高于700℃后,材料的压缩强度缓慢降低.导致2D-C/SiC的压缩强度随温度变化的主要原因为纤维和基体热膨胀系数不同引起的残余应力随温度升高逐渐变小和高温下材料的氧化损伤.%The compressive strength of a two dimensional carbon fiber reinforced silicon carbide composite (2D-C/SiC) at elevated temperature in air was studied. The plain weaved carbon cloth was applied as reinforcement, made of stacked and seamed 1K T300 carbon fiber cloth. The 2D-C/SiC was prepared by isothermal chemical vapor infiltration. The specimens were coated with SiC by chemical vapor deposition. The tests were conducted at room temperature, 700°C , 1100°C and 1300°C respectively, and the loading direction was perpendicular to 2D-C/SiC plane. The fractured surface of the specimens was observed by a scanning electron microscope. The results show that the compressive strength increases gradually with increasing the temperature from room temperature to 700°C , while it decreases gradually when the temperature was above 700°C. The residual stress caused by the mismatch between the thermal expansion coefficients of the fiber and matrix, and the oxidation products play important roles in determining the compressive strength.

  19. Performance Appraisal of Controlled Low-strength Material Using Sewage Sludge and Refuse Incineration Bottom Ash

    甄广印; 周海燕; 赵天涛; 赵由才


    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.

  20. 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

    杨世锋; 柴启辉; 孙明权


    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

  1. 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

    眭小龙; 何明胜; 付小建


    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.

  2. 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

    赵云良; 张一敏; 陈铁军


    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.

  3. 钢管高强混凝土压弯构件滞回性能的研究%Research on hysteretic behavior of high strength concrete filled steel tubular member under compression and bending

    王湛; 甄永辉


    In this paper, the force-displacement hysteretic loops of high strength concrete filled steel tubular members under compression and bending are calculated using element method with a steel constitutive model which is suitable for multiaxial cyclic loading and for a concrete modified bounding surface model for multiaxial cyclic compression. Six new tests were carried out on steel tubes filled with concrete with a cube strength of 77N/mm2. The theoretical lateral force-displacement hysteretic loops are compared with these tests and tests by other experimenters and the results are discussed.%本文根据适用于三向周期受力的钢材本构关系模型,和适用于三向周期受力改进的混凝土本构关系的边界面模型,采用有限元法对钢管高强混凝土压弯构件的荷载-位移滞回曲线进行了理论分析,并进行了6个核心混凝土的强度为77N/mm2的钢管高强混凝土压弯构件滞回性能的试验研究。将理论分析和本试验研究及其他试验研究结果进行了对比,分析了荷载-位移滞回曲线的特点。

  4. Hawaiian Volcano Flank Stability Appraised From Strength Testing the Hawaiian Scientific Drilling Project's (HSDP) 3.1-km Drill Core

    Thompson, N.; Watters, R. J.; Schiffman, P.


    Strength results from limited testing of HSDP core samples reveal significant differences in their unconfined compressive and shear strength. The median strength values show a progressive increase from the incipient (2.4 MPa) to smectitic (4.2 MPa) to palagonitic (9.4 MPa) alteration zones. The strength differences include differences among hyaloclastites as a function of their alteration, as well as differences between hyaloclastites and the various forms of lava flows and intrusive bodies. The unconfined compressive strengths of extrusive submarine and subaerial lavas and intrusive rocks from the HSDP core samples are much greater than that of any of the hyaloclastites, and range from 82 to 150 MPa. The cohesive shear strengths of hyaloclastites increase successively with depth and type of alteration (from 0.9 MPa for the incipient zone to 3.2 MPa for the palagonite zone). Conversely, the frictional strengths of the hyaloclastites show a decrease with increasing depth and alteration zone (from 17.6° for hyaloclastites from the incipient zone to 13.7° for the palagonitic zone). The Mohr strength envelope changes from a linear relationship at shallow depth to become curvilinear with increasing depth and consequently shows higher cohesion and lower friction. Comparison of the three groups of the altered hyaloclastites showed that they had p values < 0.05, and that the mean strength results from the incipient, smectitic and palagonitic altered hyaloclastites were significantly different from each other. The greatest difference was calculated between the mean value of the palagonitic alteration and the mean values from the smectitic and incipient alteration though subsequent statistical testing showed that the means of the incipient and smectitic alteration were not significantly different from each other. The palagonitic mean remains significantly different from both the incipient and smectitic means. No statistically significant difference was found in comparing

  5. 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

    段邦政; 鄢朝勇; 朱攀; 肖枭; 孙少君


    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.


    郭力群; 李安露; 彭兴黔


    针对福建土楼墙身夯土材料强度的无损检测方法进行研究。通过对回弹仪工作原理以及夯土材料强度的研究,对回弹仪进行加大弹击杆端的改进以提高其测试精度,结合夯土试块的抗压强度试验建立起不同年代夯土材料专用测强曲线。并通过现场实测,验证改进后回弹仪的适用性,为在役土楼的现场无损检测打下了基础,有助于进一步完善土楼保护措施。%It was studied the nondestructive testing methods of rammed-earth material strength of tulou wall .Through the research of working principle of the rebound hammer and rammed-earth material mechanical properties , the area of the rod end of the rebound hammer was enlarged to improve the detection precision .Combined with the compressive strength test of rammed earth cubes , the testing strength curves of rammed-earth material in different chron were set up .And through the field test , it was verified the applicability of the improved rebound hammer , which laid a foundation for field detection of the tulou ( earth-building ) in service , and contributed to improving protection measures .

  7. "Compressed" Compressed Sensing

    Reeves, Galen


    The field of compressed sensing has shown that a sparse but otherwise arbitrary vector can be recovered exactly from a small number of randomly constructed linear projections (or samples). The question addressed in this paper is whether an even smaller number of samples is sufficient when there exists prior knowledge about the distribution of the unknown vector, or when only partial recovery is needed. An information-theoretic lower bound with connections to free probability theory and an upper bound corresponding to a computationally simple thresholding estimator are derived. It is shown that in certain cases (e.g. discrete valued vectors or large distortions) the number of samples can be decreased. Interestingly though, it is also shown that in many cases no reduction is possible.

  8. Elasticity, shear strength, and equation of state of molybdenum and gold from x-ray diffraction under nonhydrostatic compression to 24 GPa

    Duffy, Thomas S. [Department of Geosciences, Princeton University, Princeton, New Jersey 08544 (United States); Shen, Guoyin [Consortium for Advanced Radiation Sources, The University of Chicago, 5640 South Ellis Avenue, Chicago, Illinois 60637 (United States); Shu, Jinfu [Geophysical Laboratory and Center for High-Pressure Research, Carnegie Institution of Washington, 5251 Broad Branch Road NW, Washington, DC 20015 (United States); Mao, Ho-Kwang [Geophysical Laboratory and Center for High-Pressure Research, Carnegie Institution of Washington, 5251 Broad Branch Road NW, Washington, DC 20015 (United States); Hemley, Russell J. [Geophysical Laboratory and Center for High-Pressure Research, Carnegie Institution of Washington, 5251 Broad Branch Road NW, Washington, DC 20015 (United States); Singh, Anil K. [Materials Science Division, National Aerospace Laboratories, Bangalore 5600 17, (India)


    Lattice strains were measured as a function of the angle {psi} between the diffracting plane normal and the stress axis of a diamond anvil cell in a layered sample of molybdenum and gold. The sample was compressed over the range 5-24 GPa and the lattice strains were measured using energy-dispersive x-ray diffraction. As {psi} is varied from 0 degree sign to 90 degree sign , the mean lattice parameter of molybdenum increases by up to 1.2% and that of gold increases by up to 0.7%. A linear relationship between Q(hkl), which is related to the slope of the measured d spacing versus 1-3 cos{sup 2} {psi} relation, and 3{gamma}(hkl), a function of the Miller indices of the diffracting plane, is observed for both materials as predicted by theory. The pressure dependence of the uniaxial stress t for gold from this and other recent studies is given by t=0.06+0.015P, where P is the pressure in GPa. The uniaxial stress in molybdenum can be described by t=0.46+0.13P. Using gold as an internal pressure standard, the equation of state of molybdenum depends strongly on {psi}. The bulk modulus obtained from a Birch-Murnaghan fit varies from 210 to 348 GPa as {psi} varies from 0 degree sign to 90 degree sign . However, an equation of state in good agreement with shock and ultrasonic isotherms is obtained for {psi}=54.7 degree sign where the deviatoric contribution to the lattice strain vanishes. Second-order elastic moduli for gold and molybdenum are obtained from the data. The results are generally consistent with an earlier x-ray study and with extrapolations of low-pressure ultrasonic data. The pressure dependence of the shear modulus C{sub 44} is smaller for the x-ray data than predicted by extrapolation of ultrasonic data. (c) 1999 American Institute of Physics.

  9. Effect of Raw Materials and Their Ratio on Compressive Strength of Magnesium Phosphate Cement%原材料及配比对磷酸镁水泥强度的影响

    齐召庆; 徐哲; 孙运亮; 丁建华; 张时豪; 姜自超


    The influence of M/P ratio (mass ratio of MgO and K2HPO4), water/cement ratio (W/C), borax content, MgO specific surface area on the early strength of magnesium phosphate cement was studied. And microstructure of magnesium phosphate cement was analyzed by using scanning electron microscope (SEM). The results show that the compressive strength of magnesium phosphate cement at the age of 1h decreases with the increase of M/P ratio, when hydration age is 3 d and 7 d, M/P ratio is 4:1,magnesium phosphate cement stone has the highest strength, the highest intensity can reach to 74.68 MPa; water-binder ratio has little effect on early strength of magnesium phosphate cement;when hydration age is 7 d, the strength decreases with the increase of water-binder ratio; in the early hydration, with the increasing of borax content, crystal of magnesium phosphate cement hydration products becomes small, the structure becomes loose, the crystal defect increases, so its strength decreases; in the later hydration, the structure becomes compact, the strength after 7 d has little change. Within 7 d, the strength of the magnesium phosphate cement increases with increasing of MgO specific surface area.%研究了 M/P 比值(MgO 与 K2HPO4的质量比),水胶比(W/C),硼砂掺量,MgO 比表面积对磷酸镁水泥早期强度的影响,采用扫描电子显微镜对磷酸镁水泥的微观形貌进行了表征。结果表明:磷酸镁水泥1 h的抗压强度随 M/P 比值的增大而减小,在水化龄期为3 d 和7 d 时,M/P 比值为4:1时磷酸镁水泥石的强度最高,最高强度达到了74.68 MPa,水胶比对磷酸镁水泥石早期强度影响不大,7 d 强度随着水胶比的增大而减小,磷酸镁水泥在水化早期随着硼砂掺量的增加,水化产物晶体变得细小,晶体缺陷增多,结构疏松,其强度随着硼砂掺量增加而降低,后期水化产物连接成一体,结构致密,7 d 的强度几乎



  11. Non-linear model for compression tests on articular cartilage.

    Grillo, Alfio; Guaily, Amr; Giverso, Chiara; Federico, Salvatore


    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.

  12. 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

    钟大虎; 夏辉; 窦益华; 曹银萍


    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.

  13. Morphological and Strength Properties of Tanjung Bin Coal Ash Mixtures for applied in Geotechnical Engineering Work

    Abd. Rahim Awang


    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.

  14. 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

    余涛; 曹德光; 刘文威; 李浩璇; 陆石强


    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.

  15. 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

    郝成伟; 邓敏; 莫立武; 刘开伟


    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.

  16. 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

    周双喜; 陈益民; 张文生


    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.

  17. The Effect of Steel Corrosion on Bond Strength in Concrete Structures

    FANG Cong-qi; KOU Xin-jian


    The effect of steel corrosion on the behavior of bond between steel and the surrounding concrete was in vestigated. Pullout tests were carried out to demonstrate bond stress-slip response for reinforcing steel bars of a series of corrosion level. Specimens either confined or unconfined were investigated for evaluation of the effect of confinement on bond strength and failure mode. Also, the tests were analyzed using nonlinear finite element analysis. It was shown that for both confined and unconfined steel bars, bond strength generally decreases as the corrosion level increases when corrosion level is relatively high. Confinement was demonstrated to provide excellent means to conteract bond loss for corroded reinforcing steel bars. It was shown that unconfined specimens generally split at a small slip with a large crack width and result in splitting failure while confined specimens contribute to a small crack width and generally cause a pullout failure. The analysis results agree reasonably well with the experiments.

  18. Revisiting the Bjerrum’s correction factor:Use of the liquidity index for assessing the effect of soil plasticity on undrained shear strength

    Kamil Kayabali; Ozgur Akturk; Mustafa Fener; Orhan Dikmen; Furkan Hamza Harputlugil


    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.

  19. Revisiting the Bjerrum's correction factor: Use of the liquidity index for assessing the effect of soil plasticity on undrained shear strength

    Kamil Kayabali


    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.

  20. 饰面瓷厚度对氧化锆全瓷冠抗压缩破坏力的影响%Influence of veneering porcelain thickness on the compressive strength of zirconia all-ceramic crown

    王晓雪; 仇亚非; 袁硕; 张钊; 郭长军


    目的:研究饰面瓷厚度对氧化锆全瓷冠抗压缩破坏力的影响。方法:常规 CAD-CAM制作氧化锆筒状基底冠25个,厚度均为0.5 mm,随机分为 A、B、C、D、E 5组,饰面瓷厚度依次为0.5、1.0、1.5、2.0、2.5 mm。万能材料试验机测试各组试件抗压缩破坏力值。采用 SPSS13.0统计软件对测试结果进行统计分析。用扫描电镜(SEM)观察试件断裂面微观结构。结果:A ~E 组试件抗压缩破坏力值依次为:(1279.96±42.85)N、(2235.44±50.14)N、(2216.38±48.97)N、(2169.22±60.40)N、(2028.70±47.37)N。A 组、E 组氧化锆全瓷修复体的抗压缩破坏力值均低于其他3组(P <0.01);其余组间抗压缩破坏力值无统计学差异(P >0.05)。扫描电子显微镜观察发现,A 组、E 组氧化锆全瓷修复体基底瓷-饰面瓷结合界面处不平坦,较为疏松;饰瓷层出现气孔及微裂纹增多、增大。结论:饰面瓷厚度低于1.0 mm 及高于2.0 mm 时,修复体的微观结构可能会受到影响,从而氧化锆全瓷冠整体抗压缩破坏力的性能受影响,建议临床应用时严格控制饰面瓷厚度。%Objective:To explore the influence of the veneering porcelain thickness on the compressive strength of zirconia all-ceramic crown.Methods:25 zirconia basement crowns with the thickness of 0.5 mm were made by CAD-CAMsystem,and then were divided into 5 groups randomly with the veneering porcelain thickness of 0.5(A),1.0(B),1.5(C),2.0(D)and 2.5 mm(E)respectively. The compressive strength of the samples was measured by a testing machine.Statistical analysis was conducted by SPSS13.0 software. The microstructure of the fractured bonding interface of the specimens was observed by scanning electron microscope(SEM).Results:The compressive strength in group A,B,C,D and E were:(1 279.96 ±42.85)N,(2 235.44 ±50.14)N,(2 216.38 ±48.97)N, (2 169.22 ±60

  1. 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

    蔡雅; 沈家平


    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

  2. Observation on compressive strength of veneers on mottled teeth after pulse Nd:YAG laser irradiation%氟斑牙经脉冲Nd:YAG激光照射后贴面抗压强度观察

    夏永华; 张丹丹


    Objective To analyze experimentally the compressive strength of veneers on mottled teeth after Dul8e Nd:YAG laser irradiation.Methods Sixty motded teeth were extracted,including thirty maxdlary central incisors and thirty maxillary lateral incisors and each were divided equally into two groups randomly(experimental groups and control groups).The former were irradiated by pulse Nd:YAG lafer and then etched by 37%phosphorus acid.The latter only etched by 37%phosphorus acid.All the teeth were restored by composite resin veneers and tested with Instron 4505 electronic testing machine.The average collapse loads of the veneers of incisors were tested. The maximal compressive loads of the samples were obtained,then the experimental results were analyzed.Results The average collapse loads of central incisors of test groups and control groups were(0.342±0.053),(0.289±0.041) kN respectively,with a signiticant difference(t=3.16,P<0.05).The average collapse loads of lateral incisors of test groups and control groups were(0.321±0.041),(0.208 ±0.032)kN respectively.There was a significant difference when they were compared(t=7.66,P<0.05).Conclusions The compressive strength of the veneers incneases significandv when the mottled teeth are irradiated by pulse Nd:YAG laser.This method is worthy of recommending.%目的 观察氟斑牙经脉冲Nd:YAG激光照射后贴面的抗压强度变化.方法 取因各种原因而拔除的人上颌中切、侧切氟斑牙各30颗,每种切牙均分成试验组和对照组,每组15颗.试验组牙齿以脉冲Nd:YAG激光照射后.再以37%的磷酸酸蚀;而对照组牙齿只用37%的磷酸酸蚀,然后所有牙齿做树脂贴面,在Instron 4505电子万能试验机上进行压缩试验,测定切牙的试验组、对照组贴面的平均破坏载荷.结果 试验组和对照组中切牙贴面平均破坏载荷分别为(0.342 4-0.053)、(0.289±0.041)kN,试验组明显高于对照组,两组比较差异有统计学意义(t=3.16,P<0.05);试验

  3. 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



    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.

  4. 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

    严少华; 钱七虎; 孙伟; 尹放林


    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.

  5. Experimental study on ultimate bearing capacity of axially compressed high strength steel columns%高强钢焊接箱形柱轴心受压极限承载力试验研究

    李国强; 王彦博,; 陈素文


    An experimental and theoretical study was presented on ultimate bearing capacity of axially compressed high strength steel columns. The experimental program included 7 welded box columns of 3 different cross sections which were welded with 11 mm-thick Q460 high strength steel plates made in China. The FEA models were built up according to measured sizes of members and tension coupon test results. And initial geometric imperfections and residual stress were taken into account in the FEA models. The experimental result shows that the stability coefficients of welded box columns of high strength steel are higher than the values of type c column curve in GB 50017--2003, and even higher than the values of type b curve for most of the specimens. However, due to the limited test result, the adoption of type b curve needs further verification. The FEA result agrees well with experimental result and could be a valid supplement of test data.%为了研究高强钢中厚板焊接箱形柱的极限承载力,以11 mm厚国产Q460高强钢中厚板制作了7个焊接箱形柱进行轴心受压试验。试件共包含宽厚比8、12、18三种截面,长细比分别为35、50、70。根据试件的实测尺寸、钢材的力学性能建立有限元模型,以初始缺陷的形式考虑了试件的初始挠度、初始偏心及焊接残余应力,分析预测了试件的极限承载力。试验结果表明,高强钢焊接箱形柱稳定系数采用GB 50017—2003《钢结构设计规范》中的c类截面柱子曲线偏保守,试验结果平均曲线更接近b类截面曲线,但仍需进一步验证。分析结果表明,考虑了初始缺陷的有限元模型可准确预测柱的极限承载力,可以作为试验数据的补充。

  6. Three-dimensional conceptual model for the Hanford Site unconfined aquifer system: FY 1994 status report

    Thorne, P.D.; Chamness, M.A.; Vermeul, V.R.; Macdonald, Q.C.; Schubert, S.E.


    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.

  7. The Effects of Eggshell Ash on Strength Properties of Cement-stabilized Lateritic

    Okonkwo U. N


    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.

  8. Stepwise pumping approach to improve free phase light hydrocarbon recovery from unconfined aquifers


    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...

  9. Validation of hydraulic tomography in an unconfined aquifer: A controlled sandbox study

    Zhao, Zhanfeng; Illman, Walter A.; Yeh, Tian-Chyi J.; Berg, Steven J.; Mao, Deqiang


    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.

  10. Shear Strength of Remoulding Clay Samples Using Different Methods of Moulding

    Norhaliza, W.; Ismail, B.; Azhar, A. T. S.; Nurul, N. J.


    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.

  11. 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

    郭晓潞; 施惠生


    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.

  12. 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

    郝笑梦; 张新昌


    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 ℃.

  13. 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

    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:; 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)


    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.

  14. 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

    李俊哲; 方光秀


    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.

  15. Dynamic strength of reaction-sintered boron carbide ceramic

    Savinykh, A. S.; Garkushin, G. V.; Razorenov, S. V.; Rumyantsev, V. I.


    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.

  16. 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

    李海南; 马保国; 张承志


    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。

  17. An Experimental Study of Unconfined Hydrogen/Oxygen and Hydrogen/Air Explosions

    Richardson, Erin; Skinner, Troy; Blackwood, James; Hays, Michael; Bangham, Mike; Jackson, Austin


    Development tests are being conducted to characterize unconfined Hydrogen/air and Hydrogen/Oxygen blast characteristics. Most of the existing experiments for these types of explosions address contained explosions, like shock tubes. Therefore, the Hydrogen Unconfined Combustion Test Apparatus (HUCTA) has been developed as a gaseous combustion test device for determining the relationship between overpressure, impulse, and flame speed at various mixture ratios for unconfined reactions of hydrogen/oxygen and hydrogen/air. The system consists of a central platform plumbed to inject and mix component gasses into an attached translucent bag or balloon while monitoring hydrogen concentration. All tests are ignited with a spark with plans to introduce higher energy ignition sources in the future. Surrounding the platform are 9 blast pressure "Pencil" probes. Two high-speed cameras are used to observe flame speed within the combustion zone. The entire system is raised approx. 6 feet off the ground to remove any ground reflection from the measurements. As of this writing greater than 175 tests have been performed and include Design of Experiments test sets. Many of these early tests have used bags or balloons between approx. 340L and approx. 1850L to quantify the effect of gaseous mixture ratio on the properties of interest. All data acquisition is synchronized between the high-speed cameras, the probes, and the ignition system to observe flame and shock propagation. Successful attempts have been made to couple the pressure profile with the progress of the flame front within the combustion zone by placing a probe within the bag. Overpressure and impulse data obtained from these tests are used to anchor engineering analysis tools, CFD models and in the development of blast and fragment acceleration models.

  18. Wellhead compression

    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)


    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)

  19. Compressive beamforming

    Xenaki, Angeliki; Mosegaard, Klaus


    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...

  20. Strength Measurements of Archive K Basin Sludge Using a Soil Penetrometer

    Delegard, Calvin H.; Schmidt, Andrew J.; Chenault, Jeffrey W.


    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. Approximate solutions for Forchheimer flow during water injection and water production in an unconfined aquifer

    Mathias, Simon A.; Moutsopoulos, Konstantinos N.


    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.


    Cai-Zhi SUN; Wei ZOU; Xue-Yu LIN


    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.

  3. In situ stress magnitude and rock strength in the Nankai accretionary complex: a novel approach using paired constraints from downhole data in two wells

    Huffman, K. A.; Saffer, D. M.; Dugan, B.


    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.

  4. 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

    洛锋; 杨本生; 郝彬彬; 孙利辉; 付明明


    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

  5. Experimental research on the strength characteristic of unsaturated structural loess%非饱和结构性黄土的强度特性试验研究

    马秀婷; 邵生俊; 杨春鸣; 李小林


    The loess is structural and unsaturated.Direct shear tests on intact loess and remold loess are firstly carried out by controlling the matric suction of unsaturated soil.Then the effect of the matric suction on the net stress strength index,parameter (φ)b in the Fredlund shear strength formula and parameter x in the Bishop effective stress formula of unsaturated soil is analyzed respectively.The experimental results show that net stress strength index increases with the increasing matric suction,(φ)b and x decreases with the increasing matric suction,and under the same matric suction,the net stress strength index,(φ)b and x of the intact loess are all larger than those of the remold loess.Besides,the unconfined compressive strengths of the intact loess,remold loess and saturated loess are measured by means of the single axial compression instrument.According to the definition of structural indices,the structural index of intact loess and remold loess with different water contents are obtained based on the unconfined compressive strength.Finally,the relationship among the net stress strength index and parameters (φ)b,x and structural index is also explored.The values of (φ)b and x unsaturated loess have the monotonic variation with the structural index.Under the same configuration conditions,the values of (φ)b and x of the intact loess are greater than those of the remolded loess,which reflects the differences in structural traits of the two types of unsaturated soil.%黄土既有非饱和性,又有结构性.首先在控制基质吸力的条件下进行了原状黄土与重塑黄土的非饱和直接剪切试验,分析了两种结构性状非饱和土的基质吸力对净应力强度指标、Fredlund抗剪强度公式中参数(φ)b、以及Bisho 抗剪强度公式中参数x的影响.表明两种土的黏聚力随基质吸力的增大而增大,(φ)b和X均随基质吸力的增大而减小;在相同基质吸力条件下,原状黄土的黏聚力、(Ψ)b和x均

  6. Influence of Compacting Rate on the Properties of Compressed Earth Blocks

    Humphrey Danso


    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.

  7. 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

    王敏; 吴勇生; 李如燕; 孙可伟


    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.

  8. 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

    胡芳芳; 张一敏; 陈铁军; 包申旭; 刘涛


    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

  9. A study of compressibility and compactibility of directly compressible tableting materials containing tramadol hydrochloride.

    Mužíková, Jitka; Kubíčková, Alena


    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.

  10. 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

    曹文明; 邢振贤; 马荣佳


    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。

  11. 热压温度及板材密度对竹木复合层积材顺纹抗压强度的影响%Influence of hot-pressing temperature and board density on compressive strength of bamboo-wood composite LVL

    张晓春; 蒋身学; 张齐生


    通过单因变量两因素重复试验,以毛竹竹篾和桦木单板为原料,使用酚醛树脂胶黏剂压制竹木复合层积材,分析热压温度及板材密度对竹木复合层积材顺纹抗压强度的影响.结果表明,在试验选定因素水平范围内,热压温度和板材密度对竹木复合层积材顺纹抗压强度影响显著,板材顺纹抗压强度随热压温度的升高而增强,但145℃与160℃两水平之间差异并不显著;不同密度对板材顺纹抗压强度的影响差异显著,板材的顺纹抗压强度随板材密度的增大而增大;在其他工艺参数相对不变的情况下,热压温度与板材密度的交互作用对板材顺纹抗压强度的影响并无显著的影响.%Two-factor experiments were carried out to study the effects of hot-pressing temperature and board density on compressive strength of bamboo-wood composite LVL. The tested boards were made from bamboo strips near bamboo green and birch veneers using phenolic-formaldehyde adhesive. The results showed that hot-pressing temperature and board density had a significant effect on the compressive strength parallel to the grain, which was enhanced with the rise of hot-pressing temperature. But the value difference between 145℃ and 155 ℃ was not significant. Board density had a significant effect n the compressive strength, which increased with the increase of board density. The interaction of hot-pressing temperature and board density had no significant effect on the compressive strength parallel to the grain.

  12. Strength Modeling of High-Strength Concrete with Hybrid Fibre Reinforcement

    A. Ravichandran


    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.

  13. Injection of Zero Valent Iron into an Unconfined Aquifer Using Shear-Thinning Fluids

    Truex, Michael J.; Vermeul, Vincent R.; Mendoza, Donaldo P.; Fritz, Brad G.; Mackley, Rob D.; Oostrom, Martinus; Wietsma, Thomas W.; Macbeth, Tamzen


    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.

  14. The influence of low-permeability cap on capillary pressure during pumping in unconfined aquifer

    黄辉; 钱家忠; 匡星星; 陈冰宇; 马雷; 吴亚楠


    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.

  15. A new package in MODFLOW to simulate unconfined groundwater flow in sloping aquifers.

    Wang, Quanrong; Zhan, Hongbin; Tang, Zhonghua


    The nonhorizontal-model-layer (NHML) grid system is more accurate than the horizontal-model-layer grid system to describe groundwater flow in an unconfined sloping aquifer on the basis of MODFLOW-2000. However, the finite-difference scheme of NHML was based on the Dupuit-Forchheimer assumption that the streamlines were horizontal, which was acceptable for slope less than 0.10. In this study, we presented a new finite-difference scheme of NHML based on the Boussinesq assumption and developed a new package SLOPE which was incorporated into MODFLOW-2000 to become the MODFLOW-SP model. The accuracy of MODFLOW-SP was tested against solution of Mac Cormack (1969). The differences between the solutions of MODFLOW-2000 and MODFLOW-SP were nearly negligible when the slope was less than 0.27, and they were noticeable during the transient flow stage and vanished in steady state when the slope increased above 0.27. We established a model considering the vertical flow using COMSOL Multiphysics to test the robustness of constrains used in MODFLOW-SP. The results showed that streamlines quickly became parallel with the aquifer base except in the narrow regions near the boundaries when the initial flow was not parallel to the aquifer base. MODFLOW-SP can be used to predict the hydraulic head of an unconfined aquifer along the profile perpendicular to the aquifer base when the slope was smaller than 0.50. The errors associated with constrains used in MODFLOW-SP were small but noticeable when the slope increased to 0.75, and became significant for the slope of 1.0.

  16. Leachability and strength of kaolin stabilized with cement and rubber

    Meei-Hoan Ho


    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

  17. Internal stress and yield strength of copper films on substrates

    Zhang Jian-Min; Zhang Yan; Xu Ke-Wei


    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.

  18. Compression Enhanced Shear Yield Stress of Electrorheological Fluid

    ZHANG Min-Liang; TIAN Yu; JIANG Ji-Le; ZHU Xu-Li; MENG Yong-Gang; WEN Shi-Zhu


    @@ 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.

  19. 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

    周海雷; 杨恒阳; 努尔开力·依孜特罗甫; 侍克斌


    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.


    NOZEMTСEV Alexandr Sergeevich


    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.

  1. HRB500级高强钢筋偏心受压截面对称配筋设计研究%Study of cross-section symmetrical reinforcement design reinforced with HRB500 high-strength steel bars under eccentric compression

    曾亮; 华建民; 兰定筠; 袁渊


    通过对新GB 50010-2010《混凝土结构设计规范》中增加的HRB500级高强钢筋用于偏心受压构件时的截面对称配筋进行研究,得到HRB500级高强钢筋偏心受压构件大小偏心受压的判别条件,以及对应的截面配筋计算方法;同时,对HRB500级高强钢筋对应的Nu-Mu相关曲线进行讨论.本文研究结论为高强钢筋偏心受压构件对称配筋截面设计提供了具体判别条件和计算方法.%Through the study of eccentric compression cross-section symmetrical reinforcement design reinforced with HRB500 highstrength steel bars,which adds into the new Code for the Design of Concrete Structures GB50010-2010 recently,it gets the criterion for large and small eccentricity of eccentric compression member,and the corresponding cross-section reinforcement calculation method.Furthermore,it discusses the Nu-Mu interaction curve of HRB500 high-strength steel bars.The conclusion will provide specific criterion and calculation method for eccentric compression cross-section symmetrical reinforcement design reinforced with high-strength steel bars.

  2. Compressive Fatigue in Wood

    Clorius, Christian Odin; Pedersen, Martin Bo Uhre; Hoffmeyer, Preben;


    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...... is observed between stiffness reduction and accumulated creep. A failure model based on the total work during the fatigue life is rejected, and a modified work model based on elastic, viscous and non-recovered viscoelastic work is experimentally supported, and an explanation at a microstructural level...

  3. Uniaxial Compressive Properties of Ultra High Toughness Cementitious Composite

    CAI Xiangrong; XU Shilang


    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.

  4. Compressive Sensing Over Networks

    Feizi, Soheil; Effros, Michelle


    In this paper, we demonstrate some applications of compressive sensing over networks. We make a connection between compressive sensing and traditional information theoretic techniques in source coding and channel coding. Our results provide an explicit trade-off between the rate and the decoding complexity. The key difference of compressive sensing and traditional information theoretic approaches is at their decoding side. Although optimal decoders to recover the original signal, compressed by source coding have high complexity, the compressive sensing decoder is a linear or convex optimization. First, we investigate applications of compressive sensing on distributed compression of correlated sources. Here, by using compressive sensing, we propose a compression scheme for a family of correlated sources with a modularized decoder, providing a trade-off between the compression rate and the decoding complexity. We call this scheme Sparse Distributed Compression. We use this compression scheme for a general multi...

  5. Compression limits in cascaded quadratic soliton compression

    Bache, Morten; Bang, Ole; Krolikowski, Wieslaw;


    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....

  6. Satellite data compression

    Huang, Bormin


    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-

  7. Establishment of earth tides effect on water level fluctuations in an unconfined hard rock aquifer using spectral analysis

    Maréchal, Jean-Christophe; Ahmed, Shakeel; Lachassagne, Patrick


    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.


    程起有; 童小燕; 陈刘定; 姚磊江; 李斌


    采用落锤冲击试验系统对平纹编织碳纤维增强碳化硅复合材料平板试样进行低速冲击,冲击能量为1.5~9J.冲击试验后,采用超声C扫描得到冲击损伤的大小.对含冲击损伤的试样进行压缩试验,通过与未冲击试样的压缩强度比较,得到冲击试样的剩余压缩强度.并对比了编织陶瓷基复合材料和树脂基复合材料的损伤阻抗和损伤容限.结果显示:随着冲击能量的增加,冲击力峰值、复合材料损伤面积和凹坑深度明显增加,到达峰值冲击力的时间减小.冲击能量的增加会导致冲击损伤面积的增加,而损伤面积的增加会导致剩余压缩强度的明显降低.相对于编织纤维增强树脂基复合材料,编织纤维增强陶瓷基复合材料的损伤阻抗较低,但损伤容限较高.%An experimental study was carried out to investigate the low-velocity impact characteristics and the strength after impact of plain woven carbon fiber reinforced silicon carbide composite.The test specimens were impacted using a dropped.weight impact test apparatus with an instrumented spherical tip.Non-destructive test methods were then utilized to characterize and quantify the impact damage.The residual compressive strengths of composites after impact were determined.The impact damage resistance and tolerance of woven fiber-reinforced ceramic.matrix composite were compared with those of woven fiber-reinforced polymer-matrix composite.The resuits show that a circular indentation on the impacted surface of specimens is formed in the impact.The peak load and the diameter and depth of indentation increase with the increase of the impact energy.The time reached to impact the peak load decrease with the increase of impact energy.According to observation of optical photographs and the image characteristics of samples obtained by ultrasonic C-scan after impact,the impact damage areas increase with the increase of impact energy.With the increase of impact

  9. Analysis of three-dimensional groundwater flow toward a radial collector well in a finite-extent unconfined aquifer

    C.-S. Huang; J.-J. Chen; H.-D. Yeh


    This study develops a three-dimensional mathematical model for describing transient hydraulic head distributions due to pumping at a radial collector well (RCW) in a rectangular confined or unconfined aquifer bounded by two parallel streams and no-flow boundaries. The governing equation with a point-sink term is employed. A first-order free surface equation delineating the water table decline induced by the well is considered. The head solution for the point sink is derived ...

  10. Approximate analysis of three-dimensional groundwater flow toward a radial collector well in a finite-extent unconfined aquifer

    C.-S. Huang; J.-J. Chen; H.-D. Yeh


    This study develops a three-dimensional (3-D) mathematical model for describing transient hydraulic head distributions due to pumping at a radial collector well (RCW) in a rectangular confined or unconfined aquifer bounded by two parallel streams and no-flow boundaries. The streams with low-permeability streambeds fully penetrate the aquifer. The governing equation with a point-sink term is employed. A first-order free surface equation delineating the water table decline ind...

  11. Modeling the Impact of Carbon Dioxide Leakage into an Unconfined, Oxidizing Carbonate Aquifer

    Bacon, Diana H.; Qafoku, Nikolla; Dai, Zhenxue; Keating, Elizabeth; Brown, Christopher F.


    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.

  12. Unconfined, melt edge electrospinning from multiple, spontaneous, self-organized polymer jets

    Wang, Qingqing; Curtis, Colin K.; Muthuraman Thoppey, Nagarajan; Bochinski, Jason R.; Gorga, Russell E.; Clarke, Laura I.


    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.

  13. Variability in bacteria and virus-like particle abundances during purging of unconfined aquifers.

    Roudnew, Ben; Lavery, Trish J; Seymour, Justin R; Jeffries, Thomas C; Mitchell, James G


    Standard methodologies for sampling the physicochemical conditions of groundwater recommend purging a bore for three bore volumes to avoid sampling the stagnant water within a bore and instead gain samples representative of the aquifer. However, there are currently no methodological standards addressing the amount of purging required to gain representative biological samples to assess groundwater bacterial and viral abundances. The objective of this study was to examine how bacterial and viral abundances change during the purging of bore volumes. Six bores infiltrating into unconfined aquifers were pumped for five or six bore volumes each and bacteria and virus-like particles (VLPs) were enumerated from each bore volume using flow cytometry. In examination of the individual bores trends in bacterial abundances were observed to increase, decrease, or remain constant with each purged bore volume. Furthermore, triplicates taken at each bore volume indicated substantial variations in VLP and bacterial abundances that are often larger than the differences between bore volumes. This indicates a high level of small scale heterogeneity in microbial community abundance in groundwater samples, and we suggest that this may be an intrinsic feature of bore biology. The heterogeneity observed may be driven by bottom up processes (variability in the distribution of organic and inorganic nutrients), top-down processes (grazing and viral lysis), physical heterogeneities in the bore, or technical artifacts associated with the purging process. We suggest that a more detailed understanding of the ecology underpinning this variability is required to adequately describe the microbiological characteristics of groundwater ecosystems.

  14. The Influenced of Compression on Properties of Binderless Compressed Veneer Made from Oil Palm Trunk

    Norhafizah Saari


    Full Text Available Binderless compressed veneer panels from oil palm trunk consisted of 5 layers of oil palm trunk veneers were made with 3 different thickness, 7 mm, 10 mm and 15 mm. The panels were pressed at temperature of 180 °C with pressure 5 MPa at duration time of 20 minutes. The veneers were pressed without using any synthetic adhesive in the manufacturing process. Mechanical and physical properties such as flexural test, thickness swelling and water absorption, density and compression ratio were observed and evaluated based on Japanese Agricultural Standard 2003 (JAS. The findings showed that binderless compressed veneer panels that undergo pressing process with thickness bar 7 mm showed the highest value of flexural strength compared to other type of panels. Dimensional stability such as thickness swelling and water absorption showed relationship with compression ratio. Based on the results, the compression ratio did influenced the properties of binderless compressed veneer panel made from oil palm trunk.

  15. 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

    陈远远; 季韬; 江其东; 梁咏宁


    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.

  16. Influence of Hot-pressing Press and Board Density on Compressive Strength of Bamboo-wood Composite Laminated Veneer Lumber%热压压力及板材密度对竹木复合层积材顺纹抗压强度的影响

    张晓春; 朱芋锭; 姚迟强; 李延军; 张齐生


    Two-factor experiments were carried out to study the effects of hot-pressing pressure and board density on compressive strength of bamboo-wood composite LVL. And the microscopic structure of the boards was observed by scanning electron microscopy. The tested boards were made from bamboo strips near bamboo green and birch veneers using phenol-formaldehyde adhesive. The results showed that the compressive strength parallel to the grain was first enhanced and then reduced significantly with the rise of hot-pressing pressure, and was significantly enhanced with the rise of board density. The interaction of hot-pressing pressure and board density had no significant effect on the compressive strength parallel to the grain. Scanning electron micrographs showed that the board internal structure was damaged in a certain degree when the hot-pressing pressure rose to a certain level.%通过单因变量两因素重复试验,以毛竹竹篾和桦木单板为原料,使用酚醛树脂胶黏剂压制竹木复合层积材,分析热压压力及板材密度对竹木复合层积材顺纹抗压强度的影响,并利用扫描电子显微镜对竹木复合层积材的微观构造进行了观察.结果表明,在试验选定因素水平范围内,热压压力和板材密度对竹木复合层积材顺纹抗压强度影响显著,板材顺纹抗压强度随热压压力的升高先增大而后减小,且各水平间差异显著;不同密度对板材顺纹抗压强度的影响差异显著,板材的顺纹抗压强度随板材密度的增大而增大;在其他工艺参数相对不变的情况下,热压压力与板材密度的交互作用对板材顺纹抗压强度的影响并无显著的影响.扫描电镜照片显示,热压压力升至一定水平,板材内部结构受到一定程度的损伤.

  17. Strength Training

    ... en español Entrenamiento de la fuerza muscular Strength training is a vital part of a balanced exercise routine that includes aerobic activity and flexibility exercises. Regular aerobic exercise, such as running or ...

  18. Strength Training

    ... strengthens your heart and lungs. When you strength train with weights, you're using your muscles to ... see there are lots of different ways to train with weights. Try a few good basic routines ...

  19. Effects of Waste Glass (WG on the Strength Characteristics of Cement Stabilized Expansive Soil



    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.

  20. Artificial Neural Network Model for Predicting Compressive

    Salim T. Yousif


    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.

  1. 信息动态%Size Effect on Strength of Ultra-high Strength Concrete RPC


    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.

  2. Research on Influencing Factors on Asphalt Mixture Shear Strength%沥青混合料抗剪强度影响因素研究

    高燕希; 曾红雄; 张东省


    针对沥青路面抗剪强度不足而容易导致推移、拥包、车辙等早期病害的现象,基于沥青路面弹性层状理论,通过有限元建立符合实际受力的贯入模型;由单轴贯入试验分别得到不同级配、相同级配有无填加矿粉、不同油石比、不同沥青种类、不同集料类型沥青混合料的最大剪应力并分别结合1组相应的无侧限抗压强度进而计算出材料的c、φ值.通过数据分析后,初步总结出影响沥青混合料抗剪强度变化的一般规律.%To cope with the lower shear strength of asphalt pavement leading to early diseases such as slippage, upheaval and rutting, based on asphah pavement layered elastic theory, the penetration model in line with the actual forcing was established through finite element method. The maximum shear stresses of asphalt mixture with different gradations, same gradation with/without filled mineral fines, different asphalt contents, different asphalt types and different aggregate types were obtained from uniaxial penetration test, then c and φ values of these materials were calculated respectively with a group of corresponding unconfined compressive strength. Through data analysis, the regularity of impact on asphalt mixture shear strength was summed up initially.

  3. Understanding tectonic stress and rock strength in the Nankai Trough accretionary prism, offshore SW Japan

    Huffman, Katelyn A.

    Understanding the orientation and magnitude of tectonic stress in active tectonic margins like subduction zones is important for understanding fault mechanics. In the Nankai Trough subduction zone, faults in the accretionary prism are thought to have historically slipped during or immediately following deep plate boundary earthquakes, often generating devastating tsunamis. I focus on quantifying stress at two locations of interest in the Nankai Trough accretionary prism, offshore Southwest Japan. I employ a method to constrain stress magnitude that combines observations of compressional borehole failure from logging-while-drilling resistivity-at-the-bit generated images (RAB) with estimates of rock strength and the relationship between tectonic stress and stress at the wall of a borehole. I use the method to constrain stress at Ocean Drilling Program (ODP) Site 808 and Integrated Ocean Drilling Program (IODP) Site C0002. At Site 808, I consider a range of parameters (assumed rock strength, friction coefficient, breakout width, and fluid pressure) in the method to constrain stress to explore uncertainty in stress magnitudes and discuss stress results in terms of the seismic cycle. I find a combination of increased fluid pressure and decreased friction along the frontal thrust or other weak faults could produce thrust-style failure, without the entire prism being at critical state failure, as other kinematic models of accretionary prism behavior during earthquakes imply. Rock strength is typically inferred using a failure criterion and unconfined compressive strength from empirical relations with P-wave velocity. I minimize uncertainty in rock strength by measuring rock strength in triaxial tests on Nankai core. I find strength of Nankai core is significantly less than empirical relations predict. I create a new empirical fit to our experiments and explore implications of this on stress magnitude estimates. I find using the new empirical fit can decrease stress

  4. Simulation of the transfer of hydrocarbons in unconfined aquifer in tropical zone: the case of benzene

    Agnès Kouamé, Amenan; Jaboyedoff, Michel; Derron, Marc-Henri; Kouamé, Kan Jean


    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

  5. Uniaxial Compression Analysis and Microdeformation Characterization of Kevin Dome Anhydrite Caprock

    Malenda, M. G.; Frash, L.; Carey, J. W.


    The Department of Energy currently manages the Regional Carbon Sequestration Partnership (RCSP) in efforts to develop techniques to characterize promising CO2 storage sites, efficient and durable technology for injection, and suitable regulations for future CO2 storage. Within the RCSP, the Montana State University-Bozeman led Big Sky Carbon Sequestration Project has focused on potential CO2 storage sites, including the Kevin Dome in northern Montana. The 750mi2 large dome lies along the north-southwest trending Sweetgrass Arch and is a natural CO2 reservoir with the potential to produce one million tonnes of CO2. The Project intends to extract and reinject this one million tonnes of CO2back into the water-leg of the Dome within the dolomitic, middle Duperow Formation to monitor impacts on the surrounding environment and communities. The caprock system includes extremely low porosity dolomite in the upper Duperow that is overlain by the anhydrite-dominated Potlatch caprock. Core was extracted by the Project from the Wallawein 22-1 well. Six 1"-diameter sub-samples were taken at depths of 3687 and 3689' of the 4"-diameter core in both vertical and horizontal directions. Unconfined uniaxial compression tests were conducted at room temperature using an Instron 4483 load frame with a 150kN load cell operated at a strain rate of 6.835-5mm per second. Samples were instrumented with four strain gages to record elastic moduli and characterize fracture behavior. The Potlatch anhydrite has demonstrated to be both strong and stiff with an average uniaxial compressive strength of 150.62±23.95MPa, a Young's modulus of 89.96±10.22GPa, and a Poisson's ratio of 0.32±0.05. These three variables are essential to developing geomechanical models that assess caprock responses to injection during CO2 sequestration. Petrographic characterizations of the fractured samples reveal an 80% groundmass of subeuhedral anhydrite crystals measuring 97-625μm and 20% 0.12-1mm wide veins

  6. Geochemical Impacts of Leaking CO2 from Subsurface Storage Reservoirs to Unconfined and Confined Aquifers

    Qafoku, Nikolla; Brown, Christopher F.; Wang, Guohui; Sullivan, E. C.; Lawter, Amanda R.; Harvey, Omar R.; Bowden, Mark


    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

  7. Unconfined Groundwater Quality based on the Settlement Unit in Surakarta City

    Munawar Cholil


    Full Text Available The quality of groundwater of unonfined aquifer with growing population density is endangered by population. This may cause serious problem as greatest portion of the population utility groundwater of unconfined aquifer as their drinking water. This research is aim at studying the difference in quality of groundwater of unonfined aquifer in Surakarta Munipicality by settlement units, and studying the impact settlement factors and groundwater depth on the quality of groundwater of unonfined aquifer. The research was executed by a survey methhod, taking 44 units of groundwater of unonfined aquifer samples at stratified proportional random from 44 villages. The samples were analyzed at the laboratory of Local Drinking Water Company (PDAM of Surakarta. Data were analyzed using by stiff diagram, variance analysis, and multiple regression. The research reveals that there is very little differences in the quality of free groundwater in Surakarta, as it is shown by same chemical properties. Several chemical properties were found very high in concentration, but the rest were simultaniously low. On the basis of minimum quality of drinking water coli content have exeeded the allowed limit for drinking water. Among the settlement units observed, there were no significant differences in the physical, chemical (except pH, bacteriological factors. This means that differences among various depth of water. Electrical onductivity (EC, Na, Mg, H2CO3, H2SO4, and NH3 were found different among various depth of water table. Major chemical conentration were significant with geology formation. Population density, built up areas, size of settlement, building density, and the condition of drainage simultaniously affect the quality of free ground water. No differences among settlement units was observed the most important fators determining the free groundwater quality was population density.

  8. Analytical solutions of seawater intrusion in sloping confined and unconfined coastal aquifers

    Lu, Chunhui; Xin, Pei; Kong, Jun; Li, Ling; Luo, Jian


    Sloping coastal aquifers in reality are ubiquitous and well documented. Steady state sharp-interface analytical solutions for describing seawater intrusion in sloping confined and unconfined coastal aquifers are developed based on the Dupuit-Forchheimer approximation. Specifically, analytical solutions based on the constant-flux inland boundary condition are derived by solving the discharge equation for the interface zone with the continuity conditions of the head and flux applied at the interface between the freshwater zone and the interface zone. Analytical solutions for the constant-head inland boundary are then obtained by developing the relationship between the inland freshwater flux and hydraulic head and combining this relationship with the solutions of the constant-flux inland boundary. It is found that for the constant-flux inland boundary, the shape of the saltwater interface is independent of the geometry of the bottom confining layer for both aquifer types, despite that the geometry of the bottom confining layer determines the location of the interface tip. This is attributed to that the hydraulic head at the interface is identical to that of the coastal boundary, so the shape of the bed below the interface is irrelevant to the interface position. Moreover, developed analytical solutions with an empirical factor on the density factor are in good agreement with the results of variable-density flow numerical modeling. Analytical solutions developed in this study provide a powerful tool for assessment of seawater intrusion in sloping coastal aquifers as well as in coastal aquifers with a known freshwater flux but an arbitrary geometry of the bottom confining layer.

  9. A potential-based inversion of unconfined steady-state hydraulic tomography.

    Cardiff, M; Barrash, W; Kitanidis, P K; Malama, B; Revil, A; Straface, S; Rizzo, E


    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.

  10. Determining the mechanical strength of CO2-induced reaction zones in wellbore cement: is it worth it?

    Hangx, Suzanne; Marcelis, Fons; van der Linden, Arjan; Liteanu, Emilia


    CO2 injection, either for long-term CO2 storage (CCS) or Enhanced Oil Recovery (EOR), strongly hinges on maintaining storage integrity. Injection and legacy wells penetrating the caprock pose one of the most likely points of leakage. In order to be able to predict the long-term integrity of such wellbores, it's important to understand their chemical, hydrological and mechanical behaviour, and how it may change due to CO2 exposure. Generally, in response to CO2/brine/cement interactions, a number of different reaction zones are observed, each with their own chemical, and hence mechanical, signature. To aid mechanical modelling efforts, assessing the risk of cement failure caused by stress and temperature changes, knowledge is required of the strength of each of these zones. We performed experiments on Class G Portland cement to investigate the chemical-mechanical coupling due to CO2-exposure. Batch reaction experiments, in the presence of CO2-rich brine, were performed under typical storage conditions (T = 65° C, PCO2 = 8 MPa) for various periods of time (1, 2, 3, 4, 5 and 6 months). After exposure, mechanical tests were performed on the observed reaction zones, using the so-called core scratching technique, to evaluate the unconfined compressive strength (UCS) as a function of exposure time. Chemical analyses (CT-imaging, SEM microscopy, EDX chemical analysis) showed the formation of three reaction zones, similarly to what has been observed in other studies. Measurements of the mechanical strength of these different zones showed highly variable results. Such variations have also been observed in other studies, using different measurement techniques. The large variability in strength measurements is most likely an inherent result of the heterogenic nature of cement, which affects the extent and location of reaction throughout the sample. This begs the question: is it worth studying the mechanical strength of reaction-induced zones in cement? Or will it suffice to

  11. Ultimate Strength of Ship Structural Plate with Pitting Corrosion Damnification Under Uniaxial Compression%点蚀损伤船体板格单轴压缩极限强度

    张岩; 黄一


    为了能够简单准确地计算服役期内点蚀损伤船体板格的极限强度,选择腐蚀体积为点蚀损伤板的主要评估参数,结合实际船体板格的腐蚀损伤特点,采用有限元数值计算方法,分析点蚀坑形状、有限元单元类型、蚀坑分布和蚀坑深度对板极限强度的影响,以及板的初始柔度、初始变形、长宽比和板边缘线性载荷因子对板极限强度折减因子的影响,并利用回归分析方法,建立了基于腐蚀体积的点蚀损伤船体板格极限强度折减因子的计算公式.结果表明,整套公式的计算结果与有限元计算结果的相对误差仅有极少量在5%,~6%,之间,绝大部分在5%,以内,可用于服役期内点蚀损伤船体板格的安全评估.%To simply and accurately calculate the ultimate strength of ship structural plates with corrosion damnifica-tion during the service lives of ships,the corrosion volume loss was used as the most important assessment parameter of the plate with corrosion damnification.On the basis of the characteristics of the actual hull structural plates,the effects of some parameters(the shape of pits,the type of finite elements,the distribution of pits and the depth of pits)on the ultimate strength and the effects of some parameters(the initial slenderness,the initial geometric deflec-tion and the aspect of plates and the linear load factors at the plate edges)on ultimate strength reduction factor were studied by the nonlinear finite element analyses.The ultimate strength reduction factor formulae based on the corro-sion volume loss were obtained by regression analysis approach.The results show that most of the relative errors be-tween the calculating value by the formulae and finite element analysis result are below 5%, and only very few is 5%,—6%,.The formulae can be used in the safety assessment of ship structural plates with pitting corrosion damnifi-cation during their service lives.

  12. Experimental Study on Coal-Breaking Pressure for Compressed Air


    Based on lab model experiments and through the limit analysis, the theoretical formula of calculauoncoal-breaking pressure with compressed air was derived. The experimental result shows that blasting pressure mustexceed 84.0 MPa to break coal with compressive strength of 13.2 MPa. The research provides an important theoretical basis for the design of airshooting mining and industrial tests.

  13. Compressive Failure of Fibre Reinforced Materials

    Jensen, Henrik Myhre


    Compressive failure of uni-directional fibre composites by the kink band mechanism is analysed taking into account effects of residual stresses. Two criteria for determining the strength of the composite material have been investigated: Kink band formation at a bifurcation stress in a composite...

  14. Temperature Effects on Brain Tissue in Compression

    Rashid, Badar; Gilchrist, Michael; 10.1016/j.jmbbm.2012.04.005


    Extensive research has been carried out for at least 50 years to understand the mechanical properties of brain tissue in order to understand the mechanisms of traumatic brain injury (TBI). The observed large variability in experimental results may be due to the inhomogeneous nature of brain tissue and to the broad range of test conditions. However, test temperature is also considered as one of the factors influencing the properties of brain tissue. In this research, the mechanical properties of porcine brain have been investigated at 22C (room temperature) and at 37C (body temperature) while maintaining a constant preservation temperature of approximately 4-5C. Unconfined compression tests were performed at dynamic strain rates of 30 and 50/s using a custom made test apparatus. There was no significant difference (p = 0.8559 - 0.9290) between the average engineering stresses of the brain tissue at the two different temperature conditions. The results of this study should help to understand the behavior of bra...

  15. Characteristics of structural loess strength and preliminary framework for joint strength formula

    Rong-jian LI; Jun-ding LIU; Rui YAN; Wen ZHENG; Sheng-jun SHAO


    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.

  16. A influência do número de barras na resistência à compressão axial dos fixadores externos monoplanares em modelos de tíbias de poliuretano The influence of the number of bars on the axial compressive strength of uniplanar external fixators in polyurethane tibia models

    Márcio Hiroaki Kume


    Full Text Available OBJETIVO: Analisar a resistência (rigidez do sistema de fixação externa tubular uniplanar, com hastes de conexão única e dupla, com traços de fraturas estáveis e instáveis. MÉTODOS: Foram utilizados 48 modelos semelhantes à tíbia. Em todos foi deixado um intervalo de 0,5 cm entre os fragmentos e realizados cortes com angulações de 15º e 45º para simular fraturas estáveis e instáveis, respectivamente. Os modelos foram divididos em quatro grupos de acordo com o traço fraturário (15º e 45º e o número de barras metálicas na montagem (1 e 2 barras. Os modelos de prova foram adaptados à uma máquina de testes Instron®, pelas suas extremidades, e submetidos à compressão axial até que os fragmentos tiveram contato total. Avaliou-se a força necessária para efetuar o completo contato dos fragmentos do modelo. RESULTADOS: As forças instabilizadoras na montagem do fixador com barra dupla foram bastante superiores às com barra única. Observou-se ainda que o grupo com barra única instável apresentou variabilidade muito menor que os demais grupos, ou seja, apresenta resultados mais homogêneos, além de ter apresentado a menor média. CONCLUSÃO: A montagem do fixador externo com uma haste longitudinal dupla nos modelos estudados é mais estável que as demais quando submetidas à uma força de compressão axial.OBJECTIVE: This is an experimental study with the objective of analyses the increase of rigidity in synthetic tibia bones with external fixators, with single and double connecting rods and with stable and unstable fracture patterns. METHODS: The external fixators were used in the monoplanar, half pin configuration submitted to an axial compression load using the connecting bar in different patterns. Forty-eight similar models to the human tibia had been used. In all the models were left an interval of 0,5 cm between the fragments and were made cuts of 15º and 45º to simulate stable and unstable fracture patterns

  17. 水灰比对再生混凝土抗压强度影响的研究%Study of Water Cement Ratios on Compressive Strength of Recycled Concrete



    指出了再生混凝土是将废弃混凝土经过清洗、破碎、分级,并按一定比例相互配合后得到的,是将再生骨料作为部分或者全部骨料配置的混凝土。水灰比是影响混凝土的抗压强度的主要因素。不同的水灰比对混凝土的其它方面的性能也有一定的影响。在相同的水灰比下,普通混凝土的性能与再生混凝土的性能又是否存在着差异,是试验研究的问题。试验采用不同的水灰比,将再生混凝土与普通混凝土的强度进行了比较,分析了不同水灰比对再生混凝土强度的影响。%Recycled concrete is made of waste concrete by cleaning ,crushing ,grading and under a certain proportion of mutual cooperation ,and is configured by concrete recycled aggregate as part of or all of the aggregate .The water cement ratio influences the strength of concrete ,and different water cement ratios also influence concrete′s other properties .This test focuses on the problems of whether there are some influences on the recycled concrete performance and whether there are differences between the performance of ordinary concrete and recycled concrete performance in the same water cement ratio .By adopting different water -cement ratios to the recycled concrete and normal concrete strength ,it compares their durability ,carbonation resistance .Finally ,it analyzes the influences of different water cement ratios on the properties of recycled concrete .

  18. Hydromorphology of the Unconfined Groundwater in the South of Klaten District (Data Before Earthquake Mei 27th 2006

    Langgeng Wahyu Santosa


    Full Text Available There are some characteristics and distributions of unconfined groundwater variation in the research area. Those are related to a system of water supply and consumptive use for drinking water. Variation of the groundwater characteristic depends on variation of morphology. Therefore, it is needed to delineate hydromorphology units of the regions as a base on groundwater resources management, especially for drinking water. The aims of the research are: (1 to study of the characteristic and distribution of unconfined groundwater variations base on landform units, (2 to study the factors that affect such variations, and (3 to establish the hydromorphology units of the regions for groundwater resources management, especially for drinking water. The method used in this research is landform approach and field survey. The sampling method is stratified sampling, based on landform as the analysis approach. Result of the research shows that there are some variations of groundwater characteristic at each landform. Landforms which have good groundwater characteristic are Hydromorphology Unit of Fluvio Volcanic Plain of Young Merapi (except Bayat region and Hydromorphology Unit of Volcanic Foot Plain of Young Merapi. At those units, there are good quality of groundwater, bicarbonate water (hydrochemical type I, having low electric conductivity, shallow of water table, low in fluctuation, and middle to fast class in aquifer permeability. Those units are the most potential unconfined groundwater resources management for drinking water. The units which have poor groundwater characteristic are Hidromorphology Unit in Bayat Region, including Undulating Alluvial Plain, Fluvio Volcanic Plain of Young Merapi, and Swamp Alluvial Plain. Generally, the groundwater quality is medium to poor, the hydrochemical type is Va (initiation process of connate water and type III (evaporate water, shallow up to medium of water table, and low to middle class of aquifer permeability

  19. A Compressive Superresolution Display

    Heide, Felix


    In this paper, we introduce a new compressive display architecture for superresolution image presentation that exploits co-design of the optical device configuration and compressive computation. Our display allows for superresolution, HDR, or glasses-free 3D presentation.

  20. Isostatic compression of buffer blocks. Middle scale

    Ritola, J.; Pyy, E. [VTT Technical Research Centre of Finland, Espoo (Finland)


    Manufacturing of buffer components using isostatic compression method has been studied in small scale in 2008 (Laaksonen 2010). These tests included manufacturing of buffer blocks using different bentonite materials and different compression pressures. Isostatic mould technology was also tested, along with different methods to fill the mould, such as vibration and partial vacuum, as well as a stepwise compression of the blocks. The development of manufacturing techniques has continued with small-scale (30 %) blocks (diameter 600 mm) in 2009. This was done in a separate project: Isostatic compression, manufacturing and testing of small scale (D = 600 mm) buffer blocks. The research on the isostatic compression method continued in 2010 in a project aimed to test and examine the isostatic manufacturing process of buffer blocks at 70 % scale (block diameter 1200 to 1300 mm), and the aim was to continue in 2011 with full-scale blocks (diameter 1700 mm). A total of nine bentonite blocks were manufactured at 70 % scale, of which four were ring-shaped and the rest were cylindrical. It is currently not possible to manufacture full-scale blocks, because there is no sufficiently large isostatic press available. However, such a compression unit is expected to be possible to use in the near future. The test results of bentonite blocks, produced with an isostatic pressing method at different presses and at different sizes, suggest that the technical characteristics, for example bulk density and strength values, are somewhat independent of the size of the block, and that the blocks have fairly homogenous characteristics. Water content and compression pressure are the two most important properties determining the characteristics of the compressed blocks. By adjusting these two properties it is fairly easy to produce blocks at a desired density. The commonly used compression pressure in the manufacturing of bentonite blocks is 100 MPa, which compresses bentonite to approximately


    Dario Di Giuseppe


    Full Text Available This study focusses on the distribution of main anions and nitrogen species in the unconfined aquifer of a recently reclaimed land. In a 6 ha experimental field, 10 piezometers for water level measurement and groundwater sampling have been installed. After one year of monitoring, results show that the high chloride and ammonium concentrations are due to inherited from the previous brackish conditions and to organic matter mineralization, respectively. Seasonal variations and Cl/Br ratio show that the 1 m deep sub surface drainage system is the main factor conditioning the chemical characteristics and the piezometric depth of the aquifer. 

  2. Desorption Behavior of Trichloroethene and Tetrachloroethene in U.S. Department of Energy Savannah River Site Unconfined Aquifer Sediments

    Riley, Robert G.; Szecsody, Jim E.; Mitroshkov, Alexandre V.; Brown, Christopher F.


    The DOE Savannah River Site (SRS) is evaluating the potential applicability of the monitored natural attenuation (MNA) process as a contributor to the understanding of the restoration of its unconfined groundwater aquifer known to be contaminated with the chlorinated hydrocarbon compounds trichloroethylene (TCE) and tetrachloroethylene (PCE). This report discusses the results from aqueous desorption experiments on SRS aquifer sediments from two different locations at the SRS (A/M Area; P-Area) with the objective of providing technically defensible TCE/PCE distribution coefficient (Kd) data and data on TCE/PCE reversible and irreversible sorption behavior needed for further MNA evaluation.

  3. Effective pressure interface law for transport phenomena between an unconfined fluid and a porous medium using homogenization

    Marciniak-Czochra, Anna


    We present modeling of the incompressible viscous flows in the domain containing an unconfined fluid and a porous medium. For such setting a rigorous derivation of the Beavers-Joseph-Saffman interface condition was undertaken by J\\"ager and Mikeli\\'c [SIAM J. Appl. Math. \\rm 60 (2000), p. 1111-1127] using the homogenization method. So far the interface law for the pressure was conceived and confirmed only numerically. In this article we justify rigorously the pressure jump condition using the corresponding boundary layer.

  4. Hydrodynamic influences of tidal fluctuations and beach slopes on benzene transport in unconfined, sandy costal aquifers

    Ni, C.-F.; Wei, Y.-M.


    Oil spills in oceans have led to severe environment and ecosystem problems due to high toxicity substances, large spatial extents, and long temporal durations. The BTEX compounds are key indexes generally used for identifications of such contamination events and also for quantifications of residual substances after remediations. Benzene is one of the BTEX compounds, which is recognized to be high toxicity and may threat near-shore ecosystem and human safety. Therefore, the understanding of benzene transport in costal aquifers is critical for predictions of contaminated zones and managements and organizations of remediation plans. In this study a numerical investigation was conducted to quantify the influence of tidal fluctuations and beach slopes on benzene transport in an unconfined coastal aquifer. More specifically, three different tidal amplitudes and three beach slopes were considered in the two-dimensional HYDROGEOCHEM model to characterize the spatial and temporal behavior of the benzene transport. Simulation results show that tidal fluctuations will lead to shallow seawater circulations near the ground surface where the high tides can reach periodically. Such local circulation flows will trap benzene plume and the plume may migrate to the deeper aquifer, depending on the amplitudes of tides and the surface slopes of the coastal lines. The sine curve tides with 0.5 m amplitudes will create circulation plume sizes of about 50m in length and 20m in depth, while the circulation plume sizes for tides with 1.0 m amplitudes will significantly increase to approximately 150 m in length and 60 m in depth. Additionally, double the beach slopes and keep the same tidal amplitude will lead to 40 m plume movement toward the land. The amplitude of tidal fluctuation is the key factor to decide when and where a benzene plume reaches a largest depth. In general, the plume with tidal amplitude of 0.5 m requires 50 days to reach 90% of the largest depth. However, the plume with

  5. Artificial sweeteners as waste water markers in a shallow unconfined aquifer

    Bichler, Andrea; Muellegger, Christian; Hofmann, Thilo


    One key factor in groundwater quality management is the knowledge of flow paths and recharge. In coupled ground- and surface water systems the understanding of infiltration processes is therefore of paramount importance. Recent studies show that artificial sweeteners - which are used as sugar substitutes in food and beverages - are suitable tracers for domestic wastewater in the aquatic environment. As most rivers receive sewage discharges, artificial sweeteners might be used for tracking surface waters in groundwater. In this study artificial sweeteners are used in combination with conventional tracers (inert anions Cl-, SO42-, stable water isotopes δ18O, δ2H) to identify river water infiltration and the influence of waste water on a shallow unconfined aquifer used for drinking water production. The investigation area is situated in a mesoscale alpine head water catchment. The alluvial aquifer consists of quaternary gravel deposits and is characterized by high hydraulic permeability (kfmax 5 x 10-2 ms-1), high flow velocities (vmax 250 md-1) and a considerable productivity (2,5 m3s-1). A losing stream follows the aquifer in close proximity and is susceptible to infiltrate substantial volumes of water into the alluvial sediments. Water sampling campaigns in March and July 2012 confirmed the occurrence of artificial sweeteners (Acesulfam ACE, Sucralose SUC, Saccharin SAC and Cyclamat CYC) at the investigated site. The local sewage treatment plant was identified as point source of artificial sweeteners in the river water, with ACE concentrations up to 0,6 μgL-1. ACE concentrations in groundwater where approximately of one order of magnitude lower: ACE was present in 33 out of 40 sampled groundwater wells with concentrations up to 0,07 μgL-1, thus indicating considerable influence of sewage water loaded surface water throughout the aquifer. Elevated concentrations of ACE and SAC in single observation wells denote other sources of locally limited contamination

  6. Part 1: Vadose-zone column studies of toluene (enhanced bioremediation) in a shallow unconfined aquifer

    Tindall, J.A.; Friedel, M.J.; Szmajter, R.J.; Cuffin, S.M.


    The objectives of the laboratory study described in this paper were (1) to determine the effectiveness of four nutrient solutions and a control in stimulating the microbial degradation of toluene in the unsaturated zone as an alternative to bioremediation methodologies such as air sparging, in situ vitrification, or others (Part I), and (2) to compare the effectiveness of the addition of the most effective nutrient solution from Part I (modified Hoagland type, nitrate-rich) and hydrogen peroxide (H2O2) on microbial degradation of toluene for repeated, simulated spills in the unsaturated zone (Part II). For Part 1, fifteen columns (30-cm diameter by 150-cm height), packed with air-dried, 0.25-mm, medium-fine sand, were prepared to simulate shallow unconfined aquifer conditions. Toluene (10 mL) was added to the surface of each column, and soil solution and soil gas samples were collected from the columns every third day for 21 days. On day 21, a second application of toluene (10 mL) was made, and the experiment was run for another 21 days. Solution 4 was the most effective for microbial degradation in Part I. For Part II, three columns were designated nutrient-rich 3-day toluene columns and received toluene injections every 3 days; three columns were designated as nutrient-rich 7-day columns and received toluene injections every 7 days; and two columns were used as controls to which no nutrient was added. As measured by CO2 respiration, the initial benefits for aerobic organisms from the O2 enhancement were sustained by the bacteria for only a short period of time (about 8 days). Degradation benefits from the nutrient solution were sustained throughout the experiment. The O2 and nutrient-enhanced columns degraded significantly more toluene than the control columns when simulating repeated spills onto the unsaturated zone, and demonstrated a potentially effective in situ bioremediation technology when used immediately or within days after a spill. The combined usage

  7. Microbunching and RF Compression

    Venturini, M.; Migliorati, M.; Ronsivalle, C.; Ferrario, M.; Vaccarezza, C.


    Velocity bunching (or RF compression) represents a promising technique complementary to magnetic compression to achieve the high peak current required in the linac drivers for FELs. Here we report on recent progress aimed at characterizing the RF compression from the point of view of the microbunching instability. We emphasize the development of a linear theory for the gain function of the instability and its validation against macroparticle simulations that represents a useful tool in the evaluation of the compression schemes for FEL sources.

  8. Compressing Binary Decision Diagrams

    Hansen, Esben Rune; Satti, Srinivasa Rao; Tiedemann, Peter


    The paper introduces a new technique for compressing Binary Decision Diagrams in those cases where random access is not required. Using this technique, compression and decompression can be done in linear time in the size of the BDD and compression will in many cases reduce the size of the BDD to 1...

  9. Compressing Binary Decision Diagrams

    Rune Hansen, Esben; Srinivasa Rao, S.; Tiedemann, Peter

    The paper introduces a new technique for compressing Binary Decision Diagrams in those cases where random access is not required. Using this technique, compression and decompression can be done in linear time in the size of the BDD and compression will in many cases reduce the size of the BDD to 1...

  10. Hyperspectral data compression

    Motta, Giovanni; Storer, James A


    Provides a survey of results in the field of compression of remote sensed 3D data, with a particular interest in hyperspectral imagery. This work covers topics such as compression architecture, lossless compression, lossy techniques, and more. It also describes a lossless algorithm based on vector quantization.

  11. Compressed gas manifold

    Hildebrand, Richard J.; Wozniak, John J.


    A compressed gas storage cell interconnecting manifold including a thermally activated pressure relief device, a manual safety shut-off valve, and a port for connecting the compressed gas storage cells to a motor vehicle power source and to a refueling adapter. The manifold is mechanically and pneumatically connected to a compressed gas storage cell by a bolt including a gas passage therein.

  12. Effects of Clay Content of Sand on Workability and Compressive Strength of Concrete%砂石含泥量对混凝土工作性及抗压强度的影响

    刘红霞; 韩晓虎


    砂石是现代建筑中不可缺少的材料之一,含泥量是混凝土用砂石骨料质量标准中一项重要的指标,含泥量高可能引起需水量的增加,使混凝土拌合物的工作性及混凝土强度受到影响。但目前关于骨料含泥量在混凝土中的影响,尚无系统的试验和足够的数据证明。本文通过不同含泥量的砂、石配制混凝土进行试验研究,总结其对混凝土性能的影响规律,为配制合理等级的混凝土提供试验数据和理论依据。%The sand is one of the materials indispensable to modern architecture, and the clay content is an important indicator of the concrete mixing sand gravel aggregate. High clay content may cause the increase in water demand, which affects the workability of concrete mixture and the strength of concrete. But the impact of clay content of aggregate on the concrete can not yet be proved by systematic test and enough data. This paper conducted test and study of different clay content of sand and stone concrete, summarized their impact law on concrete performance, to provide experimental data and theoretical basis for the preparation of concrete with reasonable level.

  13. Recycled Concrete Strength and Deformation Performance Tests in Triaxial Compressive State%三轴受压状态下再生混凝土强度与变形性能试验研究

    潘秀英; 鹿群; 张勇; 苑利飞; 吕萧


    In order to investigate the variation of recycled concrete strength in the triaxial stress state with the different replacement ratios of recycled coarse aggregate, the experiments of Ф 50 mm × 100 mm solid cylinders were conducted by RMT-150C, and the cylinders were made into three different strengths (C20, C30, C40)and five different replacement ratios (0, 30%, 50%, 70%, 100%) of recycled coarse aggregate. The effects of different recycled coarse aggregate replacement ratios on the triaxial strength, peak strain and stress-strain curve of recycled concrete were analyzed. Test results show that the failure mode of recycled concrete are similar to that of the ordinary concrete, whereas the final failure mode of recycled coarse aggregate is quite different from that of the natural aggregate. With the increase of recycled coarse aggregate replace- ment ratios, the peak stress of C20 concrete firstly increases and then decreases ; when the recycled coarse aggregate re- placement ratio is 50%, the peak stress of C20 recycled concrete is about 10% higher than natural concrete; the regularity of peak stress of C30 concrete is not obvious with the increase of the recycled coarse aggregate replacement ratios, but the peak stress of recycled concrete was lower than natural concrete peak stress; the average peak stress of C40 concrete is reduced when the ratio of recycled coarse aggregate replacement is increased; when the ratio of recycled coarse aggregate replace- ment is 100%, the peak stress of recycled concrete is about 15% lower than natural concrete peak stress. In the triaxial stress state, the recycled concrete stress-strain curve shape is similar to natural concrete stress-strain curve shape.%为了研究三轴受力状态下再生混凝土强度随再生粗骨料取代率的变化规律,通过RMT-150C对三种强度等级(C20、C30、C40)五种再生粗骨料取代率(0、30%、50%、70%、100%)的混凝土Ф50mm×100mm圆柱体进行三轴抗

  14. Correlations between direct and indirect strength test methods

    Kallu Raj; Roghanchi Pedram


    The difficulties associated with performing direct compression strength tests on rocks lead to the devel-opment of indirect test methods for the rock strength assessment. Indirect test methods are simple, more economical, less time-consuming, and easily adaptable to the field. The main aim of this study was to derive correlations between direct and indirect test methods for basalt and rhyolite rock types from Carlin trend deposits in Nevada. In the destructive methods, point load index, block punch index, and splitting tensile strength tests are performed. In the non-destructive methods, Schmidt hammer and ultrasonic pulse velocity tests are performed. Correlations between the direct and indirect compression strength tests are developed using linear and nonlinear regression analysis methods. The results show that the splitting tensile strength has the best correlation with the uniaxial compression strength. Furthermore, the Poisson’s ratio has no correlation with any of the direct and indirect test results.

  15. Materiais para modelagem: avaliacão dos tempos de presa, das resistências à tração e compressão e das particulas (MEV = Materials for molding: assessing the setting time, tensile and compressive strengths, and particles (SEM

    Casemiro, Luciana Assirati


    Full Text Available Este trabalho comparou os tempos de presa inicial e final e as resistências à tração diametral e compressão de gessos utilizados em odontologia (natural, sintético e reforçado com resina. Os ensaios mecânicos foram realizados nos tempos de 1h e 24h após a manipulação, sendo os resultados submetidos à análise estatística (Anova two way, Tuckey P < 0,05. As partículas foram analisadas em microscópio eletrônico de varredura, procurando-se estabelecer correlações com as propriedades avaliadas. Observou-se que o gesso natural possui propriedades mecânicas superiores e maior tempo de presa que os demais. As partículas do mesmo material se apresentaram maiores que as dos outros gessos, sendo as do gesso reforçado com resina as menores de todas. Conclui-se que há relação direta entre o tamanho das partículas e as propriedades avaliadas, como pode ser observado, por exemplo, para o gesso natural (maiores partículas e maiores valores nos testes realizados

  16. A distributed compressive sensing technique for data gathering in Wireless Sensor Networks

    Masoum, Alireza; Meratnia, Nirvana; Havinga, Paul J.M.


    Compressive sensing is a new technique utilized for energy efficient data gathering in wireless sensor networks. It is characterized by its simple encoding and complex decoding. The strength of compressive sensing is its ability to reconstruct sparse or compressible signals from small number of meas

  17. A New Analytical Solution for Tide-Induced Groundwater Fluctuations in An Unconfined Aquifer with A Sloping Beach

    KONG Jun; SONG Zhi-yao; XIN Pei; SHEN Cheng-ji


    Deriving analytical solutions for tide-induced groundwater fluctuations in unconfined aquifers confronts two problems:(1) As the Boussinesq equation itself contains nonlinear terms,the “secular term” would be generated in derivation,thus making perturbation solution unable to be deduced to higher order; (2) for aquifers with sloping beaches,the perturbation parameter in existing analytical solution integrating the beach slope and hydrogeological property would be sometimes larger than 1.So the application of perturbation solutions is relatively limited.Furthermore,as the beach slope decreases,the error of analytical solution would gradually increase.Given that water table over-height would increase the aquifer thickness and speed up wave propagation,this paper integrates over-height into the perturbation parameter and adjusts boundary conditions to settle the problem of “secular term” and to derive a new high-order analytical solution for nonlinear Boussinesq equation in terms of sloping beaches.Results show that the new analytical solution is more reasonable,and the analytical accuracy is obviously improved in comparison with the existing analytical solution for a gentle slope.The new analytical solution provides a theoretical basis for analyzing the propagation characteristics (e.g.,wave length and over-height variation) of tide-induced groundwater wave in unconfined aquifers,particularly those with sloping beaches.

  18. Strength and durability of concrete modified by sulfur-based impregnating compounds

    MASSALIMOV Ismail Alexandrovich; YANAKHMETOV Marat Rafisovich; CHUYKIN Alexander Eugenyevich


    The aim of the research was to determine how sulfur-containing compound impregnation influences on concrete compressive strength and the impact resistance of concrete tiles. The results of these studies indicate that impregnation of vibropressed concrete paving tiles and concrete samples of dif-ferent strength classes with aqueous solutions based on calcium polysulfide leads to a significant increase of compressive strength and impact resistance. These data show that the strength of the pr...

  19. Damage Evolution and Strength Influence Factors of Compression Loaded Composite Laminates with an Open Hole%复合材料开口板压缩载荷下损伤扩展及强度影响因素研究

    姚辽军; 赵美英


    针对复合材料开口结构在压缩载荷下损伤扩展问题,采用累积损伤方法,对典型铺层方式下层合板压缩强度和损伤扩展规律进行了数值模拟研究。研究结果表明:不同铺层方式对含孔层合板的强度特性和损伤扩展形式有显著影响。在此基础之上,进一步研究了不同开口尺寸、不同铺层比例对层合板压缩强度的影响。%The damage evolutions of compression loaded composite laminates with circle cutout were simulated based on the three-dimension progressive damage model.Good agreement was found between the analytical and experimental results.The results showed that the ply stacking-sequence could significantly influence the damage propagations of each layer.Based on the validated finite element model,the influence of ply stacking-ratio on the strength of composite laminates was analysed.

  20. Evaluación in vitro de la resistencia compresiva de un sellante resinoso fluorado pre y post liberación de flúor In vitro compressive strength of fluoride-containing resin-based sealant before and after fluoride release

    C Vergara


    Full Text Available Objetivo: Evaluar in vitro la resistencia compresiva de un sellante resinoso fluorado (F pre y post liberación de flúor luego de la inmersión en agua. Método: Se utilizaron 40 probetas de 6 mm de alto y 20 mm de diámetro de sellante resinoso fluorado (FluroShield, Brasil, Dentsply y de sellante no fluorado (Concise(TM Light Cured White Sealant, USA, 3M ESPE. Las probetas fueron divididas en cuatro grupos, dos de sellante resinoso fluorado (F1 y F2 y dos de control (C1 y C2. Un grupo de probetas de sellante fluorado y un grupo del control (F1/C1 se mantuvieron sin exposición al agua, mientras que los grupos restantes (F2/C2 fueron inmersos en agua destilada por 30 días. Se midió la liberación de flúor desde el grupo F2 mediante el método de electrodo selectivo los días 1, 2, 3 y 30. Posteriormente se midió la resistencia compresiva mediante una máquina de ensayos mecánicos universales (Lloyd, LR 100, UK con una velocidad de cruceta de 1 mm/min. Las comparaciones entre los grupos F1 vs F2 y C1 vs C2 se analizaron con t-Student. El nivel de significancia se estableció a 0.05. Resultados: La resistencia compresiva en MPa antes y después de la inmersión en agua para el sellante resinoso fluorado fue 337.2 y 337.4, mientras que la del sellante control fue 203.8 y 213.4. Para ambos grupos las diferencias observadas no fueron significativas. Se observó un patrón de liberación de flúor inicial de 1.9 ppm durante las primeras 24 horas para luego decaer a 0.0 ppm al tercer día de liberación. Conclusión: La liberación de flúor desde un sellante resinoso fluorado no afectó su resistencia compresiva en este estudio in vitro.Aim: To evaluate in vitro compressive strength of fluoride-containing resin-based sealant (F before and after fluoride release in water. Materials and Methods: We used 40 specimens with 6 mm of height and 20 mm of diameter using fluoride-containing resin-based sealant (FluroShield,Brasil, Dentsply and non

  1. Celiac Artery Compression Syndrome

    Mohammed Muqeetadnan


    Full Text Available Celiac artery compression syndrome is a rare disorder characterized by episodic abdominal pain and weight loss. It is the result of external compression of celiac artery by the median arcuate ligament. We present a case of celiac artery compression syndrome in a 57-year-old male with severe postprandial abdominal pain and 30-pound weight loss. The patient eventually responded well to surgical division of the median arcuate ligament by laparoscopy.

  2. Fluffy dust forms icy planetesimals by static compression

    Kataoka, Akimasa; Okuzumi, Satoshi; Wada, Koji


    Context: In planetesimal formation theory, several barriers have been proposed, which are bouncing, fragmentation, and radial drift problems. To understand the structure evolution of dust aggregates is a key in the planetesimal formation. Dust grains become fluffy by coagulation in protoplanetary disks. However, once they become fluffy, they are not sufficiently compressed by collisional compression to form compact planetesimals. Aims: We aim to reveal the pathway of the dust structure evolution from dust grains to compact planetesimals. Methods: Using the compressive strength formula, we analytically investigate how fluffy dust aggregates are compressed by static compression due to ram pressure of the disk gas and self gravity of the aggregates in protoplanetary disks. Results: We reveal the pathway of the porosity evolution from dust grains via fluffy aggregates to form planetesimals, circumventing the barriers in planetesimal formation. The aggregates are compressed by the disk gas to the density of 10^{-3...

  3. Electromechanical behavior of carbon nanotube fibers under transverse compression

    Li, Yuanyuan; Lu, Weibang; Sockalingam, Subramani; Gu, Bohong; Sun, Baozhong; Gillespie, John W.; Chou, Tsu-Wei


    Although in most cases carbon nanotube (CNT) fibers experience axial stretch or compression, they can also be subjected to transverse compression, for example, under impact loading. In this paper, the electromechanical properties of both aerogel-spun and dry-spun CNT fibers under quasi-static transverse compressive loading are investigated for the first time. Transverse compression shows a nonlinear and inelastic behavior. The compressive modulus/strength of the aerogel-spun and dry-spun CNT fibers are about 0.21 GPa/0.796 GPa and 1.73 GPa/1.036 GPa, respectively. The electrical resistance goes through three stages during transverse compressive loading/unloading: initially it decreases, then it increases during the loading, and finally it decreases upon unloading. This study extends our knowledge of the overall properties of CNT fibers, and will be helpful in promoting their engineering applications.

  4. Concrete Strength for Fire Safety Design

    Hertz, Kristian Dahl


    Idealized data are derived for the compressive strength of a number of concretes for fire safety design. The data are derived from the authors own research including test series not published before and from more than 400 other test series comprising approximately 3000 specimens known from...

  5. Stiffness of compression devices

    Giovanni Mosti


    Full Text Available This issue of Veins and Lymphatics collects papers coming from the International Compression Club (ICC Meeting on Stiffness of Compression Devices, which took place in Vienna on May 2012. Several studies have demonstrated that the stiffness of compression products plays a major role for their hemodynamic efficacy. According to the European Committee for Standardization (CEN, stiffness is defined as the pressure increase produced by medical compression hosiery (MCH per 1 cm of increase in leg circumference.1 In other words stiffness could be defined as the ability of the bandage/stockings to oppose the muscle expansion during contraction.

  6. Compressed sensing & sparse filtering

    Carmi, Avishy Y; Godsill, Simon J


    This book is aimed at presenting concepts, methods and algorithms ableto cope with undersampled and limited data. One such trend that recently gained popularity and to some extent revolutionised signal processing is compressed sensing. Compressed sensing builds upon the observation that many signals in nature are nearly sparse (or compressible, as they are normally referred to) in some domain, and consequently they can be reconstructed to within high accuracy from far fewer observations than traditionally held to be necessary. Apart from compressed sensing this book contains other related app

  7. Wavelet image compression

    Pearlman, William A


    This book explains the stages necessary to create a wavelet compression system for images and describes state-of-the-art systems used in image compression standards and current research. It starts with a high level discussion of the properties of the wavelet transform, especially the decomposition into multi-resolution subbands. It continues with an exposition of the null-zone, uniform quantization used in most subband coding systems and the optimal allocation of bitrate to the different subbands. Then the image compression systems of the FBI Fingerprint Compression Standard and the JPEG2000 S

  8. 颈环高度对 CAD/CAM氧化锆全瓷冠抗压碎性能的影响%The influence of cervical collar height on the compressive strength of CAD/CAM zirconia-ceramic restora-tion

    周新文; 刘希云


    Objective:To evaluate the influence of cervical collar height on the compressive strength of CAD/CAMzirconia-ceramic restoration.Methods:Zirconia cores were manufactured and divided into 5 groups (n =1 0)based on the cervical collar height(mm):0.0(A),1 .0(B),1 .5(C),2.0(D)and 2.5(E).After veneered with porcelain,all the samples were cemented on the metal tooth analog and then mounted in an universal test machine.The force was applied at a crosshead speed of 1 mm/min until catastrophic fail-ure occurred.Fracture loads and failure modes were recorded.Results:Mean of the fracture strength values(kN)in group A,B,C, D and E were 0.95 ±0.39,1 .29 ±0.50,1 .54 ±0.28,2.04 ±0.1 9 and 2.27 ±0.53 respectively(among groups,P <0.05).Two types of fracture modes were observed:chipping of the veneering porcelain and fracture of the veneering porcelain together with the framework.Conclusion:Zirconia coping design with 1 .5 mm cervical collar height may increase the compressive strength of CAD/CAMzirconia-ceramic restoration.%目的:比较不同颈环高度对 CAD/CAM氧化锆全瓷冠抗压碎力的影响。方法:设计制作具有不同颈环高度(mm)的氧化锆基底冠,分别为0(A 组)、1.0(B 组)、1.5(C 组)、2.0(D 组)、2.5(E 组),每组10颗。常规堆筑、烧结饰面瓷后,将样本粘接固定在金属代型上进行抗压碎力测试,记录样本发生破坏时的瞬间力值和折裂形式。结果:各组抗压碎力(kN)测试结果分别为:A 组0.95±0.39、B 组1.29±0.50、C 组1.54±0.28、D 组2.04±0.19、E 组2.27±0.53,5组整体比较,P <0.05。全瓷冠的破坏形式表现为单纯饰面瓷剥脱、饰面瓷剥脱合并基底冠破损2种类型。结论:当颈环高度≥1.5 mm 时,能够显著提高氧化锆全瓷冠的抗压能力。

  9. Strength of Concrete Containing Basalt Fibre

    Parvez Imraan Ansari


    Full Text Available This paper presents the comparative study of effect of basalt fibre on compressive and split tensile strength of M40 grade concrete. The basalt fibre was mixed in concrete by (0.5%, 1%, and 1.5% of its total weight of cement in concrete. Results indicated that the strength increases with increase of basalt fibre content up to 1.0% beyond that there is a reduction in strength on increasing basalt fibre. The results show that the concrete specimen with 1.0% of basalt fibre gives better performance when it compared with 0.5%and 1.5% basalt fibre mix in concrete specimens.

  10. Strength of Concrete Containing Basalt Fibre


    This paper presents the comparative study of effect of basalt fibre on compressive and split tensile strength of M40 grade concrete. The basalt fibre was mixed in concrete by (0.5%, 1%, and 1.5%) of its total weight of cement in concrete. Results indicated that the strength increases with increase of basalt fibre content up to 1.0% beyond that there is a reduction in strength on increasing basalt fibre. The results show that the concrete specimen with 1.0% of basalt fibre gives be...

  11. A mini slug test method for determination of a local hydraulic conductivity of an unconfined sandy aquifer

    Hinsby, Klaus; Bjerg, Poul Løgstrup; Andersen, Lars J.;


    from level to level and thereby establish vertical profiles of the hydraulic conductivity. The head data from the test well are recorded with a 10 mm pressure transducer, and the initial head difference required is established by a small vacuum pump. The method described has provided 274 spatially......A new and efficient mini slug test method for the determination of local hydraulic conductivities in unconfined sandy aquifers is developed. The slug test is performed in a small-diameter (1 inch) driven well with a 0.25 m screen just above the drive point. The screened drive point can be driven...... distributed measurements of a local hydraulic conductivity at a tracer test site at Vejen, Denmark. The mini slug test results calculated by a modified Dax slug test analysing method, applying the elastic storativity in the Dax equations instead of the specific yield, are in good accordance with the results...



    Lab experiment and mathematical simulation Modular three dimensional finite difference groundwater (MODFLOW) were performed in a soil tank to simulate the hydrogeochemical interaction between lake and typical unconfined aquifer. Results show that the velocity decreases exponentially with the transect distance on seepage face. The maximal velocity occurs at the top point of seepage face. The obliquity of seepage face has a great influence on the maximum and distribution of seepage velocity. With the increase of the obliquity of seepage face, the maximal velocity decreases quickly and the velocity distribution becomes much more even. Most of groundwater flow and pollutant flux discharges through a narrow portion near the top of seepage face. The flow and mass concentrated in the narrow portion increase with the decrease of the obliquity of seepage face. These will benefit to design a reasonable and economical scenario to manage lakeshore and to control the pollution of lake water near lakeshore.

  13. Estimation of temporal and spatial variations in groundwater recharge in unconfined sand aquifers using Scots pine inventories

    P. Ala-aho


    Full Text Available Climate change and land use are rapidly changing the amount and temporal distribution of recharge in northern aquifers. This paper presents a novel method for distributing Monte Carlo simulations of 1-D soil profile spatially to estimate transient recharge in an unconfined esker aquifer. The modeling approach uses data-based estimates for the most important parameters controlling the total amount (canopy cover and timing (depth of the unsaturated zone of groundwater recharge. Scots pine canopy was parameterized to leaf area index (LAI using forestry inventory data. Uncertainty in the parameters controlling soil hydraulic properties and evapotranspiration was carried over from the Monte Carlo runs to the final recharge estimates. Different mechanisms for lake, soil, and snow evaporation and transpiration were used in the model set-up. Finally, the model output was validated with independent recharge estimates using the water table fluctuation method and baseflow estimation. The results indicated that LAI is important in controlling total recharge amount, and the modeling approach successfully reduced model uncertainty by allocating the LAI parameter spatially in the model. Soil evaporation compensated for transpiration for areas with low LAI values, which may be significant in optimal management of forestry and recharge. Different forest management scenarios tested with the model showed differences in annual recharge of up to 100 mm. The uncertainty in recharge estimates arising from the simulation parameters was lower than the interannual variation caused by climate conditions. It proved important to take unsaturated depth and vegetation cover into account when estimating spatially and temporally distributed recharge in sandy unconfined aquifers.

  14. Natural Recharge to the Unconfined Aquifer System on the Hanford Site from the Greater Cold Creek Watershed: Progress Report 2004

    Waichler, Scott R.; Wigmosta, Mark S.; Coleman, Andre M.


    Movement of contaminants in groundwater at the Hanford Site is heavily dependent on recharge to the unconfined aquifer. As the effects of past artificial discharges dissipate, the water table is expected to return to more natural conditions, and natural recharge will become the driving force when evaluating future groundwater flow conditions and related contaminant transport. Previous work on the relationship of natural recharge to groundwater movement at the Hanford Site has focused on direct recharge from infiltrating rainfall and snowmelt within the area represented by the Sitewide Groundwater Model (SGM) domain. However, part of the groundwater recharge at Hanford is provided by flow from Greater Cold Creek watershed (GCC), a large drainage area on the western boundary of the Hanford Site that includes Cold Creek Valley, Dry Creek Valley, and the Hanford side of Rattlesnake Mountain. This study was undertaken to estimate the recharge from GCC, which is believed to enter the unconfined aquifer as both infiltrating streamflow and shallow subsurface flow. To estimate recharge, the Distributed Hydrology-Soil-Vegetation Model (DHSVM) was used to simulate a detailed water balance of GCC from 1956 to 2001 at a spatial resolution of 200~m and a temporal resolution of one hour. For estimating natural recharge to Hanford from watersheds along its western and southwestern boundaries, the most important aspects that need to be considered are 1)~distribution and relative magnitude of precipitation and evapotranspiration over the watershed, 2)~streamflow generation at upper elevations and infiltration at lower elevations during rare runoff events, and 3)~permeability of the basalt bedrock surface underlying the soil mantle.

  15. Modelling the effects of porous media deformation on the propagation of water-table waves in a sandy unconfined aquifer

    Jazayeri Shoushtari, Seyed Mohammad Hossein; Cartwright, Nick


    This paper examines the influence of porous media deformation on water-table wave dispersion in an unconfined aquifer using a numerical model which couples Richards' equation to the poro-elastic model. The study was motivated by the findings of Shoushtari et al. (J Hydrol 533:412-440, 2016) who were unable to reproduce the observed wave dispersion in their sand flume data with either numerical Richards' equation models (assuming rigid porous media) or existing analytic solutions. The water-table wave dispersion is quantified via the complex wave number extracted from the predicted amplitude and phase profiles. A sensitivity analysis was performed to establish the influence of the main parameters in the poro-elastic model, namely Young's modulus (E) and Poisson's ratio (ν). For a short oscillation period (T = 16.4 s), the phase lag increase rate (k i) is sensitive to the chosen values of E and ν, demonstrating an inverse relationship with both parameters. Changes in the amplitude decay rate (k r), however, were negligible. For a longer oscillation period (T = 908.6 s), variations in the values of E and ν resulted in only small changes in both k r and k i. In both the short and long period cases, the poro-elastic model is unable to reproduce the observed wave dispersion in the existing laboratory data. Hence porous media deformation cannot explain the additional energy dissipation in the laboratory data. Shoushtari SMH, Cartwright N, Perrochet P, Nielsen P (2016) The effects of oscillation period on groundwater wave dispersion in a sandy unconfined aquifer: sand flume experiments and modelling. J Hydrol 533:412-440.

  16. Modelling the effects of porous media deformation on the propagation of water-table waves in a sandy unconfined aquifer

    Jazayeri Shoushtari, Seyed Mohammad Hossein; Cartwright, Nick


    This paper examines the influence of porous media deformation on water-table wave dispersion in an unconfined aquifer using a numerical model which couples Richards' equation to the poro-elastic model. The study was motivated by the findings of Shoushtari et al. (J Hydrol 533:412-440, 2016) who were unable to reproduce the observed wave dispersion in their sand flume data with either numerical Richards' equation models (assuming rigid porous media) or existing analytic solutions. The water-table wave dispersion is quantified via the complex wave number extracted from the predicted amplitude and phase profiles. A sensitivity analysis was performed to establish the influence of the main parameters in the poro-elastic model, namely Young's modulus ( E) and Poisson's ratio ( ν). For a short oscillation period ( T = 16.4 s), the phase lag increase rate ( k i) is sensitive to the chosen values of E and ν, demonstrating an inverse relationship with both parameters. Changes in the amplitude decay rate ( k r), however, were negligible. For a longer oscillation period ( T = 908.6 s), variations in the values of E and ν resulted in only small changes in both k r and k i. In both the short and long period cases, the poro-elastic model is unable to reproduce the observed wave dispersion in the existing laboratory data. Hence porous media deformation cannot explain the additional energy dissipation in the laboratory data. Shoushtari SMH, Cartwright N, Perrochet P, Nielsen P (2016) The effects of oscillation period on groundwater wave dispersion in a sandy unconfined aquifer: sand flume experiments and modelling. J Hydrol 533:412-440.

  17. Compression Ratio Adjuster

    Akkerman, J. W.


    New mechanism alters compression ratio of internal-combustion engine according to load so that engine operates at top fuel efficiency. Ordinary gasoline, diesel and gas engines with their fixed compression ratios are inefficient at partial load and at low-speed full load. Mechanism ensures engines operate as efficiently under these conditions as they do at highload and high speed.

  18. Strength Characteristics of Groundnut Leaf/Stem Ash (GLSA) Concrete

    Oseni, O. W.; Audu, M. T.


    The compressive strength properties of concrete are substantial factors in the design and construction of concrete structures. Compressive strength directly affects the degree to which the concrete can be able to carry a load over time. These changes are complemented by deflections, cracks etc., in the structural elements of concrete. This research investigated the effect of groundnut leaf/stem ash (GLSA) on the compressive strength of concrete at 0%, 5 %, 10 % and 15 % replacements of cement. The effect of the water-cement ratio on properties such as the compressive strength, slump, flow and workability properties of groundnut leaf/stem ash (GLSA) mixes with OPC were evaluated to determine whether they are acceptable for use in concrete structural elements. A normal concrete mix with cement at 100 % (i.e., GLSA at 0%) with concrete grade C25 that can attain an average strength of 25 N/mm2 at 28 days was used as a control at design water-cement ratios of 0.65 and grading of (0.5-32) mm from fine to coarse aggregates was tested for: (1) compressive strength, and the (2) slump and flow Test. The results and observations showed that the concrete mixes from GLSA at 5 - 15 % ratios exhibit: pozzolanic properties and GLSA could be used as a partial replacement for cement at these percentage mix ratios compared with the control concrete; an increase in the water-cement ratio showed a significant decrease in the compressive strength and an increase in workability. Therefore, it is important that all concrete mixes exude an acceptably designed water-cement ratio for compressive strength characteristics for use in structures, water-cement ratio is a significant factor.

  19. Spectral Animation Compression

    Chao Wang; Yang Liu; Xiaohu Guo; Zichun Zhong; Binh Le; Zhigang Deng


    This paper presents a spectral approach to compress dynamic animation consisting of a sequence of homeomor-phic manifold meshes. Our new approach directly compresses the field of deformation gradient defined on the surface mesh, by decomposing it into rigid-body motion (rotation) and non-rigid-body deformation (stretching) through polar decompo-sition. It is known that the rotation group has the algebraic topology of 3D ring, which is different from other operations like stretching. Thus we compress these two groups separately, by using Manifold Harmonics Transform to drop out their high-frequency details. Our experimental result shows that the proposed method achieves a good balance between the reconstruction quality and the compression ratio. We compare our results quantitatively with other existing approaches on animation compression, using standard measurement criteria.

  20. Hyphal content determines the compression strength of Candida albicans biofilms

    Paramonova, Ekaterina; Krom, Bastiaan P.; van der Mei, Henny C.; Busscher, Henk J.; Sharma, Prashant K.


    Candida albicans is the most frequently isolated human fungal pathogen among species causing biofilm-related clinical infections. Mechanical properties of Candida biofilms have hitherto been given no attention, despite the fact that mechanical properties are important for selection of treatment or d