An historical examination of concrete

International Nuclear Information System (INIS)

Mallinson, L.G.

1986-03-01

The requirement that concrete in nuclear waste repositories be stable physically and chemically for hundreds, if not thousands, of years has initiated studies of ancient and old concretes. The history of cement and concrete is described. The oldest know concrete, from Yugoslavia, is ca. 7,500 years old. Concrete was used in many ancient civilisations, including those of Egypt, Greece and Rome. Ancient concretes were usually based upon lime, but sometimes gypsum was used. Pure lime concretes hardened by atomospheric carbonation but the Ancients, in particular the Romans, also employed hydraulic limes and discovered pozzolanas to make superior concretes which, upon hardening, contained complex cementitious hydrates including calcium-silicate-hydrate (CSH), the principal binding element in Portland cement concrete. Portland cement was not invented until 1824 or later and consists principally of calcium silicates formed by clinkerisation of a mixture of limestone and clay in carefully measured proportions. The cement sets hydraulically to form, principally, calcium hydroxide and CSH, the latter being an amorphous or semi-amorphous substance of variable composition. The published literature relating to the analysis of old and ancient cements and concretes is reviewed. A suite of samples spanning the history of concrete has been obtained. A variety of physical and chemical techniques have been employed to characterise these samples. (author)

High performance concrete with blended cement

International Nuclear Information System (INIS)

Biswas, P.P.; Saraswati, S.; Basu, P.C.

2012-01-01

Principal objectives of the proposed project are two folds. Firstly, to develop the HPC mix suitable to NPP structures with blended cement, and secondly to study its durability necessary for desired long-term performance. Three grades of concrete to b considered in the proposed projects are M35, M50 and M60 with two types of blended cements, i.e. Portland slag cement (PSC) and Portland pozzolana cement (PPC). Three types of mineral admixtures - silica fume, fly ash and ground granulated blast furnace slag will be used. Concrete mixes with OPc and without any mineral admixture will be considered as reference case. Durability study of these mixes will be carried out

Portland cement concrete air content study.

Science.gov (United States)

1987-04-20

This study took the analysis of Portland cement concrete air content. Based on the information gathered, this study hold the results were : 1) air-entrained concrete was more durable than non-air entrained concrete all other factors being equal; 2) A...

Shrinkage deformation of cement foam concrete

Science.gov (United States)

Kudyakov, A. I.; Steshenko, A. B.

2015-01-01

The article presents the results of research of dispersion-reinforced cement foam concrete with chrysotile asbestos fibers. The goal was to study the patterns of influence of chrysotile asbestos fibers on drying shrinkage deformation of cement foam concrete of natural hardening. The chrysotile asbestos fiber contains cylindrical fiber shaped particles with a diameter of 0.55 micron to 8 microns, which are composed of nanostructures of the same form with diameters up to 55 nm and length up to 22 microns. Taking into account the wall thickness, effective reinforcement can be achieved only by microtube foam materials, the so- called carbon nanotubes, the dimensions of which are of power less that the wall pore diameter. The presence of not reinforced foam concrete pores with perforated walls causes a decrease in its strength, decreases the mechanical properties of the investigated material and increases its shrinkage. The microstructure investigation results have shown that introduction of chrysotile asbestos fibers in an amount of 2 % by weight of cement provides the finely porous foam concrete structure with more uniform size closed pores, which are uniformly distributed over the volume. This reduces the shrinkage deformation of foam concrete by 50%.

Response of a PGNAA setup for pozzolan-based cement concrete specimens

International Nuclear Information System (INIS)

Naqvi, A.A.; Garwan, M.A.; Maslehuddin, M.; Nagadi, M.M.; Al-Amoudi, O.S.B.; Raashid, M.

2010-01-01

Pozzolanic materials are added to Portland cement concrete to increase its durability, particularly corrosion-resistance. In this study the elemental composition of a pozzolanic cement concrete was measured non-destructively utilizing an accelerator-based Prompt Gamma Ray Neutron Activation Analysis (PGNAA) setup. The optimum size of the pozzolanic cement concrete specimen was obtained through Monte Carlo simulations. The simulation results were experimentally verified through the γ-ray yield measurement from the pozzolanic cement concrete specimens as a function of their radii. The concentration of the pozzolanic material in the cement concrete specimens was evaluated by measuring γ-ray yield for calcium and iron from pozzolanic cement concrete specimens containing 5-80 wt% pozzolan. A good agreement was noted between the experimental values and the Monte Carlo simulation results, indicating an excellent response of the KFUPM accelerator-based PGNAA setup for pozzolan based concrete.

Response of a PGNAA setup for pozzolan-based cement concrete specimens

Energy Technology Data Exchange (ETDEWEB)

Naqvi, A.A. [Department of Physics, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia)], E-mail: aanaqvi@kfupm.edu.sa; Garwan, M.A. [Department of Physics, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia); Maslehuddin, M. [Center for Engineering Research, Research Institute, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia); Nagadi, M.M. [Department of Physics, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia); Al-Amoudi, O.S.B. [Department of Civil Engineering, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia); Raashid, M. [Department of Physics, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia)

2010-04-15

Pozzolanic materials are added to Portland cement concrete to increase its durability, particularly corrosion-resistance. In this study the elemental composition of a pozzolanic cement concrete was measured non-destructively utilizing an accelerator-based Prompt Gamma Ray Neutron Activation Analysis (PGNAA) setup. The optimum size of the pozzolanic cement concrete specimen was obtained through Monte Carlo simulations. The simulation results were experimentally verified through the {gamma}-ray yield measurement from the pozzolanic cement concrete specimens as a function of their radii. The concentration of the pozzolanic material in the cement concrete specimens was evaluated by measuring {gamma}-ray yield for calcium and iron from pozzolanic cement concrete specimens containing 5-80 wt% pozzolan. A good agreement was noted between the experimental values and the Monte Carlo simulation results, indicating an excellent response of the KFUPM accelerator-based PGNAA setup for pozzolan based concrete.

Study of the performance of four repairing material systems for hydraulic structures of concrete dams

Directory of Open Access Journals (Sweden)

Kormann A. C. M.

2003-01-01

Full Text Available Four types of repairing materials are studied as function of either a conventional concrete or a reference-concrete (RefC, these are: polymer-modified cement mortar (PMor, steel fiber concrete (SFco, epoxy mortar (EMor and silica fume mortar (SFmo, to be applied in hydraulic structures surfaces subjected to a high velocity water flow. Besides the mechanical requests and wearing resistance of hydraulic concrete dam structures, especially the spillway surfaces, the high solar radiation, the environmental temperature and wet and dry cycles, contribute significantly to the reduction of their lifespan. RefC and the SFco were developed based on a usual concrete mixture used in slabs of spillways. The average RefC mixture used was 1: 1.61: 2.99: 0.376, with Pozzolan-modified Portland cement consumption of 425 kg/m³. EMor and PMor mixtures followed the information given by the manufacturers and lab experience. Tests on concrete samples were carried out in laboratory simulating normally found environmental situations in order to control the mechanical resistance and the aging imposed conditions, such as solar radiation and humidity. Also, physicochemical characterizing tests were made for all used materials. From the analyzed results, two of them presented a higher performance: the EMor and SFmo. SFco presented good adherence to the RefC and good mechanical performance. However, it also presented apparent metal corrosion in humidity tests, being indicated for use, with caution, as an intermediate layer in underwater repairs. In a general classification, considering all tests, including their field applications, the better performance material systems were EMor- SFmo> SFco> PMor.

Topics in cement and concrete research

OpenAIRE

Brouwers, Jos; Russel, M.I.; Basheer, P.A.M.

2007-01-01

The present paper addresses several topics in regard to the sustainable design and use of concrete. First, major features concerning the sustainable aspects of the material concrete are summarised. Then the major constituent, from an environmental point of view, cement is discussed in detail, particularly the hydration and application of slag cement. The intelligent combining of mineral oxides, which are found in clinker, slag, fly ashes etc., is designated as mineral oxide engineering. It re...

The Mechanism of Disintegration of Cement Concrete at High Temperatures

Directory of Open Access Journals (Sweden)

Jocius Vytautas

2016-10-01

Full Text Available Concrete is a composite material composed of a binder, aggregates, water and additives. Mixing of cement with water results in a number of chemical reactions known as cement hydration. Heating of concrete results in dehydration processes of cement minerals and new hydration products, which disintegrate the microstructure of concrete. This article reviews results of research conducted with Portland and alumina cement with conventional and refractory concrete aggregates. In civic buildings such common fillers as gravel, granite, dolomite or expanded clay are usually used. It is important to point out the differences between fillers because they constitute the majority of the concrete volume.

Applications of radioactive methods in cement concrete testing

International Nuclear Information System (INIS)

Dinakaran, M.; Vijayaraghavan, S.R.

1979-01-01

Basic principles regarding the neutron moderation technique and the successful application of this technique for determining the moisture and cement content in hardened concrete are briefly discussed. Since fast neutrons are converted into slow thermal neutrons by elastic scattering in the presence of hydrogen nuclei, it is possible to determine the moisture content in hardened cement concrete using precalibrated relationships. Also since most of the hydrogenous matter in concrete pertains to non-fixed water and hydrated cement compounds, an analysis of slow neutron counts on a sample at different non-fixed moisture contents make the estimation of cement content possible using the mathematical relationship between cement content, degree of hydration and the equivalent moisture content. The method developed is quick, non-destructive, and repeatable at the same time giving better accuracy when compared to conventional chemical methods. Use was also made of gamma ray transmission method for determining the differential density at various depths in a cement concrete pavement making use of cores cut from the pavement. Further, development proposed for determination of density at different depths of pavement in situ is also discussed. (auth.)

Achievement of 900kgf/cm[sup 2] super workable high strength concrete with belite portland cement. (elevator building of cement silo in Chichibu cement). Part 1. ; Development of cement for super workable high strength concrete. Ko belite kei cement de 900kgf/cm[sup 2] wo tassei (Chichibu cement cement sairo no elevaor to). 1. ; Koryudo kokyodo concrete yo no cement no kaihatsu

Energy Technology Data Exchange (ETDEWEB)

Tanaka, M.; Fukaya, Y.; Nawa, T. (Chichibu Cement Co. Ltd., Tokyo (Japan))

1993-08-01

This paper describes the features of high belite Portland cement which can make the super workable high strength concrete, and the properties of concrete using this. The super workable concrete is required an excellent segregation resistance property as well as high flow property. Since the high belite Portland cement contains a small amount of C[sub 3]S in the clinker, the amounts of C[sub 3]A and C[sub 4]AF can be reduced without hindering the calcination of clinker. Additionally, since it contains a large amount of C[sub 2]S with low heat of hydration, an increase in the temperature of members can be suppressed. 'Chichibu High Flow Cement' having characteristics of this high belite Portland cement was developed for the super workable high strength concrete. The concrete using the High Flow Cement exhibited the maximum flow value of 70cm. It also exhibited the strength of 1,075 kgf/cm[sup 2] at the age of 91 days, and 1,100 kgf/cm[sup 2] at the age of 14 days under insulating. 4 refs., 8 figs., 2 tabs.

Effect of Cement Composition in Lampung on Concrete Strength

OpenAIRE

Riyanto, Hery

2014-01-01

The strength and durability of concrete depends on the composition of its constituent materials ie fine aggregate, coarse aggregate, cement, water and other additives. The cement composition is about 10% acting as a binder paste material fine and coarse aggregates. In the Lampung market there are several brands of portland cement used by the community to make concrete construction. Although there is a standard of the government of portland cement composition, yet each brand of cement has diff...

Recycled materials in Portland cement concrete

Science.gov (United States)

2000-06-01

This report pertains to a comprehensive study involving the use of recycled materials in Portland cement concrete. Three different materials were studied including crushed glass (CG), street sweepings (SS), and recycled concrete (RC). Blast furnace s...

Preparing hydraulic cement from oil-shale residue

Energy Technology Data Exchange (ETDEWEB)

1921-08-28

A process for preparation of hydraulic cement from oil-shale residue is characterized in that, as flux is used, rich-in-lime poor-in-sulfur portland-cement clinker, by which the usual gypsum addition, is avoided.

Calcium Orthophosphate Cements and Concretes

Directory of Open Access Journals (Sweden)

Sergey V. Dorozhkin

2009-03-01

Full Text Available In early 1980s, researchers discovered self-setting calcium orthophosphate cements, which are a bioactive and biodegradable grafting material in the form of a powder and a liquid. Both phases form after mixing a viscous paste that after being implanted, sets and hardens within the body as either a non-stoichiometric calcium deficient hydroxyapatite (CDHA or brushite, sometimes blended with unreacted particles and other phases. As both CDHA and brushite are remarkably biocompartible and bioresorbable (therefore, in vivo they can be replaced with newly forming bone, calcium orthophosphate cements represent a good correction technique for non-weight-bearing bone fractures or defects and appear to be very promising materials for bone grafting applications. Besides, these cements possess an excellent osteoconductivity, molding capabilities and easy manipulation. Furthermore, reinforced cement formulations are available, which in a certain sense might be described as calcium orthophosphate concretes. The concepts established by calcium orthophosphate cement pioneers in the early 1980s were used as a platform to initiate a new generation of bone substitute materials for commercialization. Since then, advances have been made in the composition, performance and manufacturing; several beneficial formulations have already been introduced as a result. Many other compositions are in experimental stages. In this review, an insight into calcium orthophosphate cements and concretes, as excellent biomaterials suitable for both dental and bone grafting application, has been provided.

Low Shrinkage Cement Concrete Intended for Airfield Pavements

Science.gov (United States)

Małgorzata, Linek

2017-10-01

The work concerns the issue of hardened concrete parameters improvement intended for airfield pavements. Factors which have direct or indirect influence on rheological deformation size were of particular interest. The aim of lab testing was to select concrete mixture ratio which would make hardened concrete less susceptible to influence of basic operating factors. Analyses included two research groups. External and internal factors were selected. They influence parameters of hardened cement concrete by increasing rheological deformations. Research referred to innovative cement concrete intended for airfield pavements. Due to construction operation, the research considered the influence of weather conditions and forced thermal loads intensifying concrete stress. Fresh concrete mixture parameters were tested and basic parameters of hardened concrete were defined (density, absorbability, compression strength, tensile strength). Influence of the following factors on rheological deformation value was also analysed. Based on obtained test results, it has been discovered that innovative concrete, made on the basis of modifier, which changes internal structure of concrete composite, has definitely lower values of rheological deformation. Observed changes of microstructure, in connection with reduced deformation values allowed to reach the conclusion regarding advantageous characteristic features of the newly designed cement concrete. Applying such concrete for airfield construction may contribute to extension of its operation without malfunction and the increase of its general service life.

Mechanical properties of cement concrete composites containing nano-metakaolin

Science.gov (United States)

Supit, Steve Wilben Macquarie; Rumbayan, Rilya; Ticoalu, Adriana

2017-11-01

The use of nano materials in building construction has been recognized because of its high specific surface area, very small particle sizes and more amorphous nature of particles. These characteristics lead to increase the mechanical properties and durability of cement concrete composites. Metakaolin is one of the supplementary cementitious materials that has been used to replace cement in concrete. Therefore, it is interesting to investigate the effectiveness of metakaolin (in nano scale) in improving the mechanical properties including compressive strength, tensile strength and flexural strength of cement concretes. In this experiment, metakaolin was pulverized by using High Energy Milling before adding to the concrete mixes. The pozzolan Portland cement was replaced with 5% and 10% nano-metakaolin (by wt.). The result shows that the optimum amount of nano-metakaolin in cement concrete mixes is 10% (by wt.). The improvement in compressive strength is approximately 123% at 3 days, 85% at 7 days and 53% at 28 days, respectively. The tensile and flexural strength results also showed the influence of adding 10% nano-metakaolin (NK-10) in improving the properties of cement concrete (NK-0). Furthermore, the Backscattered Electron images and X-Ray Diffraction analysis were evaluated to support the above findings. The results analysis confirm the pores modification due to nano-metakaolin addition, the consumption of calcium hydroxide (CH) and the formation of Calcium Silicate Hydrate (CSH) gel as one of the beneficial effects of amorphous nano-metakaolin in improving the mechanical properties and densification of microstructure of mortar and concrete.

Effect of supplementary cementing materials on the concrete corrosion control

International Nuclear Information System (INIS)

Mejia de Gutierrez, R.

2003-01-01

Failure of concrete after a period of years, less than the life expected for which it was designed, may be caused by the environment to which it has been exposed or by a variety of internal causes. The incorporation of supplementary materials has at the Portland cement the purpose of improving the concrete microstructure and also of influence the resistance of concrete to environmental attacks. Different mineral by-products as ground granulated blast furnaces slag (GGBS), silica fume (SF), meta kaolin (MK), fly ash (FA) and other products have been used as supplementary cementing materials. This paper is about the behavior of concrete in the presence of mineral additions. Compared to Portland cements, blended cements show lower heat of hydration, lower permeability, greater resistance to sulphates and sea water. These blended cements find the best application when requirements of durability are regarded as a priority specially on high performance concrete: (Author) 11 refs

Heavyweight cement concrete with high stability of strength parameters

Science.gov (United States)

Kudyakov, Konstantin; Nevsky, Andrey; Danke, Ilia; Kudyakov, Aleksandr; Kudyakov, Vitaly

2016-01-01

The present paper establishes regularities of basalt fibers distribution in movable cement concrete mixes under different conditions of their preparation and their selective introduction into mixer during the mixing process. The optimum content of basalt fibers was defined as 0.5% of the cement weight, which provides a uniform distribution of fibers in the concrete volume. It allows increasing compressive strength up to 51.2% and increasing tensile strength up to 28.8%. Micro-structural analysis identified new formations on the surface of basalt fibers, which indicates the good adhesion of hardened cement paste to the fibers. Stability of concrete strength parameters has significantly increased with introduction of basalt fibers into concrete mix.

Laboratory evaluation of recycled concrete as aggregate in new concrete pavements.

Science.gov (United States)

2014-09-01

The Washington State Department of Transportation (WSDOT) has initiated a research project to investigate the use of recycled concrete as : aggregates (RCA) in Portland (hydraulic) cement concrete pavements (PCCP). The planned source for the RCA in t...

Alkali-activated blast furnace slag-zeolite cements and concretes

International Nuclear Information System (INIS)

Rakhimov, R.; Rakhimova, N.

2012-01-01

The aim of this work has been the study of alkali-activated slag-zeolite cements and concretes based on them. Various compositions have been tested and some characteristics such as the compressive strength have been measured versus zeolite additions. A table lists the specific surface area and particle size distributions of different cements. The conclusions of the study are the following. First, alkali-activated slag cements and concretes based on them are effective for immobilization of radioactive wastes and the production of building structures, designed for high radiation load. Secondly, zeolite-containing mineral additions are able to increase the immobilization capacity and radiation resistance of alkali-activated blast furnace slag cements and concretes. Thirdly, the efficiency of different zeolite-containing additions - 10% to increase alkali-activated blast furnace slag-zeolite cement strength was established. It is with alkaline components of water-glass, sodium carbonate, sodium sulphate. Fourth, the effective way of introducing zeolite additions in alkali-activated blast furnace slag-zeolite cement is inter-grinding of the slag and addition. Increase in strength of alkali-activated blast furnace slag-zeolite cement stone is 40% higher than that of the stone of a mixture of separately milled components. Fifth, Alkali-activated blast furnace slag-zeolite cements with zeolite-containing additions with a compressive strength of 10.1 to 140 MPa; alkali-activated blast furnace slag-zeolite cements mortars with compressive strength from 35.2 to 97.7 MPa; alkali-activated blast furnace slag-zeolite cements concretes with compressive strength up to 84.5 MPa and frost resistant up to 800 cycles were obtained

Topics in cement and concrete research

NARCIS (Netherlands)

Brouwers, Jos; Russel, M.I.; Basheer, P.A.M.

2007-01-01

The present paper addresses several topics in regard to the sustainable design and use of concrete. First, major features concerning the sustainable aspects of the material concrete are summarised. Then the major constituent, from an environmental point of view, cement is discussed in detail,

Optimization of superplasticizer in portland pozzolana cement mortar and concrete

Science.gov (United States)

Sathyan, Dhanya; Anand, K. B.; Mini, K. M.; Aparna, S.

2018-02-01

Chemical Admixtures are added to concrete at the time of mixing of its constituents to impart workability. The requirement of right workability is the essence of good concrete. It has been found that the use of optimum use of admixtures is very important since low dosage may result in loss of fluidity and over dosage could lead to segregation, bleeding, excessive air entrainment etc in concrete. Hence it is essential to find optimum dosage of superplasticizer for getting good strength and workability. But large number of trial tests are required in the field to find the saturation dosage of superplasticizer in concrete which requires more materials and consume more time. The paper deals with developing a co-relation between the quantity requirements of superplasticiser in mortar to that of cement concrete to get good workability. In this work for preparing mortar and concrete 4 brands of locally available Portland pozzolana cement (PPC) and superplasticizer (SP) belonging to 4 different families namely Polycarboxylate Ether (PCE), Lignosulphate (LS), Sulfonated Naphthalene Formaldehyde (SNF) and Sulfonated Melamine Formaldehyde (SMF) are used. Two different brands of SP’s are taken from each family. Workability study on the superplasticized mortar with cement to sand ratio 1:1.5 and water cement ratio of 0.4 was performed using marsh cone and flow table test and workability study on the concrete with same cement/sand ratio and water cement ratio was done using slump cone and flow table test. Saturation dosage of superplasticizer in mortar and concrete determined experimentally was compared to study the correlation between two. Compressive strength study on concrete cubes were done on concrete mixes with a superplasticizer dosage corresponding to the saturation dosage and a comparative study were done to analyse the improvement in the compressive strength with addition of superplasticizer from different family.

Hydraulic concrete composition and properties control system

OpenAIRE

PSHINKO O.M.; KRASNYUK A.V.; HROMOVA O.V.

2015-01-01

Purpose. Scientific work aims at the development and testing of information system to meet the challenges of concrete composition design and control (for railway structures and buildings) based on the physico-analytical method algorithm for hydraulic concrete composition calculation. Methodology. The proposed algorithm of hydraulic concrete composition calculation is based on the physicochemical mechanics and in particular on the rheology of elastic–viscous–plastic bodies. The system of canon...

Non-destructive analysis of chlorine in fly ash cement concrete

International Nuclear Information System (INIS)

Naqvi, A.A.; Garwan, M.A.; Nagadi, M.M.; Maslehuddin, M.; Al-Amoudi, O.S.B.; Khateeb-ur-Rehman

2009-01-01

Preventive measures against reinforcement corrosion in concrete require increasing concrete density to prevent the diffusion of chloride ions to the steel surface. Pozzolanic materials, such as fly ash (FA), silica fume (SF), and blast furnace slag (BFS) are added to concrete to increase its density. Monitoring the chloride concentration in concrete is required to assess the chances of reinforcement corrosion. In this study, FA was added to Portland cement concrete to increase its density. Prompt gamma neutron activation analysis (PGNAA) technique was utilized to analyze the concentration of chlorine in concrete. The chlorine concentration in the FA cement concrete was evaluated by determining the yield of 1.16, 1.95, 6.11, 6.62, 7.41, 7.79, and 8.58 MeV gamma-rays of chlorine from the FA concrete specimen containing 0.4-3.5 wt% chlorine. An excellent agreement was noted between the experimental yield of the prompt gamma-rays and the calculated yield obtained through the Monte Carlo simulations. The Minimum Detectable Concentration (MDC) of chlorine in FA cement concrete was also calculated. The best value of MDC limit of chlorine in the FA cement concrete was found to be 0.022±0.007 and 0.038±0.017 wt% for 1.16 and 6.11 MeV prompt gamma-rays, respectively. Within the statistical uncertainty, the lower bound of MDC meets the maximum permissible limit of 0.03 wt% of chlorine in concrete set by American Concrete Institute Committee 318.

Non-destructive analysis of chlorine in fly ash cement concrete

Energy Technology Data Exchange (ETDEWEB)

Naqvi, A.A. [Department of Physics, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia)], E-mail: aanaqvi@kfupm.edu.sa; Garwan, M.A.; Nagadi, M.M. [Department of Physics, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia); Maslehuddin, M. [Center for Engineering Research, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia); Al-Amoudi, O.S.B. [Department of Civil Engineering, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia); Khateeb-ur-Rehman [Department of Physics, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia)

2009-08-11

Preventive measures against reinforcement corrosion in concrete require increasing concrete density to prevent the diffusion of chloride ions to the steel surface. Pozzolanic materials, such as fly ash (FA), silica fume (SF), and blast furnace slag (BFS) are added to concrete to increase its density. Monitoring the chloride concentration in concrete is required to assess the chances of reinforcement corrosion. In this study, FA was added to Portland cement concrete to increase its density. Prompt gamma neutron activation analysis (PGNAA) technique was utilized to analyze the concentration of chlorine in concrete. The chlorine concentration in the FA cement concrete was evaluated by determining the yield of 1.16, 1.95, 6.11, 6.62, 7.41, 7.79, and 8.58 MeV gamma-rays of chlorine from the FA concrete specimen containing 0.4-3.5 wt% chlorine. An excellent agreement was noted between the experimental yield of the prompt gamma-rays and the calculated yield obtained through the Monte Carlo simulations. The Minimum Detectable Concentration (MDC) of chlorine in FA cement concrete was also calculated. The best value of MDC limit of chlorine in the FA cement concrete was found to be 0.022{+-}0.007 and 0.038{+-}0.017 wt% for 1.16 and 6.11 MeV prompt gamma-rays, respectively. Within the statistical uncertainty, the lower bound of MDC meets the maximum permissible limit of 0.03 wt% of chlorine in concrete set by American Concrete Institute Committee 318.

Use of cement in concrete according to European standard EN 206-1

Directory of Open Access Journals (Sweden)

Christoph Müller

2012-04-01

Full Text Available The manufacture of cements with several main constituents (blended cements is of particular importance with regard to reducing climatically relevant CO2 emissions in the cement industry. A wide variety of common cement products exists in the different EU Member States. They match local manufacturing conditions, throughout meeting particular climatic or other local conditions, including building practices. In general, all cements conforming to European Cement Standard EN 197-1 are suitable for the manufacture of concrete according to European Concrete Standard EN 206-1. Depending on the area of application, however, differences related to the cement type may possibly have to be taken into account to ensure the durability of the concretes manufactured with these cements. These regulations were laid down in National Application Documents (NADs to EN 206-1 dependent upon the exposure classes that a structural element is assigned to. This paper deals with the overall concept of EN 206-1 with regard to concrete durability. It gives an overview of the cement types used in Europe and the areas of application of cements conforming to EN 197-1 in concrete conforming to EN 206-1 and various national annexes. The option of combining several main constituents makes blended cements particularly well suited for combining the advantages of individual main constituents, and thus for developing these cements into even more robust systems. This process requires an integrated assessment of all requirements to be met by cements during manufacture and application. From a technical perspective these include the strength formation potential as well as good workability of the concrete and, in particular, the durability of the concrete made from these cements. The effects that the main constituents have with regard to properties relevant to durability can be utilized in particular in cements made from a combination of limestone/blastfurnace slag or limestone/fly ash as

INVESTIGATION OF CEMENT CONCRETE CONGLOMERATE SOLIDIFICATION PROCESS BY IMPEDANCE SPECTROSCOPY METHOD

Directory of Open Access Journals (Sweden)

S. N. Bandarenka

2015-01-01

Full Text Available One of the most prospective directions in preservation  and increase of service live of  road pavements is a construction of  automobile roads with cement concrete surface. Modern tendencies for provision of road construction quality presuppose a necessity to control processes of solidification and subsequent destruction of the material while forming and using cement concrete conglomerate being considered as a basic element of the road surface.  Multiyear practical experience of  automobile road operation using cement concrete pavements reveals an importance for monitoring  such processes as formation and destruction of cement concrete materials. An impedance spectroscopy method has been tried out and proposed as a tool for solution of the given problem.Experimental samples of cement concrete have been prepared for execution of tests, graded silica sand and granite chippings with particle size from 0.63 to 2.5 mm have been used as a fine aggregate in the samples. Dependencies of resistance (impedance on AC-current frequency  have been studied for samples of various nature and granulometric composition. The Gamry  G300 potentiostat has been used for measurement of complex impedance value. A spectrum analysis and calculation of equivalent circuit parameters calculation have been carried out while using EIS Spectrum Analyzer program.Comparison of impedance spectra for the prepared cement concrete samples have made it possible to reveal tendencies in changing spectrum parameters during solidification and subsequent contact with moisture in respect of every type of the sample. An equivalent electrical circuit has been developed that  characterizes physical and chemical processes which are accompanied by charge transfer in cement concrete conglomerate. The paper demonstrates a possibility to use an impedance spectroscopy for solution of a number of actual problems in the field of cement concrete technology problems. Particularly, the problems

Mechanical properties of Self-Consolidating Concrete incorporating Cement Kiln Dust

Directory of Open Access Journals (Sweden)

Mostafa Abd El-Mohsen

2015-04-01

Full Text Available Self-Consolidating Concrete (SCC has been widely used in both practical and laboratory applications. Selection of its components and their ratios depends, mainly, on the target mechanical and physical properties recommended by the project consultant. Partial replacement of cement in SCC with cheap available industrial by-product could produce environmentally durable concrete with similar properties of normal concrete. In the current research, SCC was produced by blending Cement Kiln Dust (CKD with cement in different ratios. Four mixes incorporating cement kiln dust with partial cement replacement of 10%, 20%, 30%, and 40% were produced and compared with a control mix of Normally Vibrated Concrete (NVC. Superplasticizer was used to increase the flow-ability of SCC mixes. The fresh and hardened mechanical properties of all mixes were determined and evaluated. Moreover, time-dependent behavior was investigated for all mixes in terms of drying shrinkage test. The shrinkage strain was measured for all specimens for a period of 120 days. Based on the experimental results, it was found that SCC mixture containing 20% cement replacement of CKD exhibited the highest mechanical strength compared to other SCC mixes and NVC mix as well. It was observed that the volumetric changes of specimens were directly proportional to the increase of the cement replacement ratio.

Prompt gamma-ray analysis of chlorine in superpozz cement concrete

Energy Technology Data Exchange (ETDEWEB)

Naqvi, A.A., E-mail: aanaqvi@kfupm.edu.sa [Department of Physics, King Fahd University of Petroleum and Minerals, Dhahran (Saudi Arabia); Kalakada, Zameer [Department of Civil Engineering, King Fahd University of Petroleum and Minerals, Dhahran (Saudi Arabia); Al-Matouq, Faris A. [Department of Physics, King Fahd University of Petroleum and Minerals, Dhahran (Saudi Arabia); Maslehuddin, M. [Center for Engineering Research, King Fahd University of Petroleum and Minerals, Dhahran (Saudi Arabia); Al-Amoudi, O.S.B. [Department of Civil Engineering, King Fahd University of Petroleum and Minerals, Dhahran (Saudi Arabia); Ur-Rehman, Khateeb [Department of Physics, King Fahd University of Petroleum and Minerals, Dhahran (Saudi Arabia)

2012-11-21

The chlorine concentration in Superpozz (SPZ) cement concrete was analyzed using a newly designed prompt gamma-ray neutron activation (PGNAA) setup utilizing a portable neutron generator. The setup, which mainly consists of a neutron source along with its moderator placed side by side with a shielded gamma-ray detector, allows determining chloride concentration in a concrete structure from one side. The setup has been tested through chlorine detection in chloride-contaminated Superpozz (SPZ) cement concrete specimens using 6.11 and 2.86{+-}3.10 MeV chlorine prompt gamma-rays. The optimum 0.032{+-}0.012 wt% value of Minimum Detectable Concentration (MDC) of chlorine in SPZ cement concrete measured in this study shows a successful application of a portable neutron generator in chloride analysis of concrete structure for corrosion studies.

Influence of increasing amount of recycled concrete powder on mechanical properties of cement paste

Science.gov (United States)

Topič, Jaroslav; Prošek, Zdeněk; Plachý, Tomáš

2017-09-01

This paper deals with using fine recycled concrete powder in cement composites as micro-filler and partial cement replacement. Binder properties of recycled concrete powder are given by exposed non-hydrated cement grains, which can hydrate again and in small amount replace cement or improve some mechanical properties. Concrete powder used in the experiments was obtained from old railway sleepers. Infrastructure offer more sources of old concrete and they can be recycled directly on building site and used again. Experimental part of this paper focuses on influence of increasing amount of concrete powder on mechanical properties of cement paste. Bulk density, shrinkage, dynamic Young’s modulus, compression and flexural strength are observed during research. This will help to determine limiting amount of concrete powder when decrease of mechanical properties outweighs the benefits of cement replacement. The shrinkage, dynamic Young’s modulus and flexural strength of samples with 20 to 30 wt. % of concrete powder are comparable with reference cement paste or even better. Negative effect of concrete powder mainly influenced the compression strength. Only a 10 % cement replacement reduced compression strength by about 25 % and further decrease was almost linear.

Prompt gamma analysis of fly ash, silica fume and Superpozz blended cement concrete specimen

Energy Technology Data Exchange (ETDEWEB)

Naqvi, A.A. [Department of Physics, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia)], E-mail: aanaqvi@kfupm.edu.sa; Garwan, M.A. [Department of Physics, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia); Maslehuddin, M. [Center for Engineering Research, Research Institute, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia); Nagadi, M.M. [Department of Physics, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia); Al-Amoudi, O.S.B. [Department of Civil Engineering, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia); Khateeb-ur-Rehman; Raashid, M. [Department of Physics, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia)

2009-09-15

Preventive measures against corrosion of reinforcing steel require making the concrete dense by adding pozzolanic materials, such as fly ash, silica fume, Superpozz, blast furnace slag, etc. to Portland cement. In order to obtain the desired strength and durability of concrete, it is desirable to monitor the concentration of the pozzolan in the blended cement concrete. Addition of pozzolan to blended cement changes the overall concentration of calcium and silicon in the blended cement concrete. The resulting variation in calcium and silicon gamma-ray yield ratio from blended cement concrete has found to have an inverse correlation with concentration of fly ash, silica fume, Superpozz, blast furnace slag in the blended cement concrete. For experimental verification of the correlation, intensities of calcium and silicon prompt gamma-ray due to capture of thermal neutrons in blended cement concrete samples containing 5-80% (by weight of cement) silica fume, fly ash and Superpozz were measured. The gamma-ray intensity ratio was measured from 6.42 MeV gamma-rays from calcium and 4.94 MeV gamma-ray from silicon. The experimentally measured values of calcium to silicon gamma-ray yield ratio in the fly ash, silica fume and Superpozz cement concrete specimens agree very well with the results of the Monte Carlo simulations.

Prompt gamma analysis of fly ash, silica fume and Superpozz blended cement concrete specimen

International Nuclear Information System (INIS)

Naqvi, A.A.; Garwan, M.A.; Maslehuddin, M.; Nagadi, M.M.; Al-Amoudi, O.S.B.; Khateeb-ur-Rehman,; Raashid, M.

2009-01-01

Preventive measures against corrosion of reinforcing steel require making the concrete dense by adding pozzolanic materials, such as fly ash, silica fume, Superpozz, blast furnace slag, etc. to Portland cement. In order to obtain the desired strength and durability of concrete, it is desirable to monitor the concentration of the pozzolan in the blended cement concrete. Addition of pozzolan to blended cement changes the overall concentration of calcium and silicon in the blended cement concrete. The resulting variation in calcium and silicon gamma-ray yield ratio from blended cement concrete has found to have an inverse correlation with concentration of fly ash, silica fume, Superpozz, blast furnace slag in the blended cement concrete. For experimental verification of the correlation, intensities of calcium and silicon prompt gamma-ray due to capture of thermal neutrons in blended cement concrete samples containing 5-80% (by weight of cement) silica fume, fly ash and Superpozz were measured. The gamma-ray intensity ratio was measured from 6.42 MeV gamma-rays from calcium and 4.94 MeV gamma-ray from silicon. The experimentally measured values of calcium to silicon gamma-ray yield ratio in the fly ash, silica fume and Superpozz cement concrete specimens agree very well with the results of the Monte Carlo simulations.

Mechanical properties of Self-Consolidating Concrete incorporating Cement Kiln Dust

OpenAIRE

El-Mohsen, Mostafa Abd; Anwar, Ahmed M.; Adam, Ihab A.

2015-01-01

Self-Consolidating Concrete (SCC) has been widely used in both practical and laboratory applications. Selection of its components and their ratios depends, mainly, on the target mechanical and physical properties recommended by the project consultant. Partial replacement of cement in SCC with cheap available industrial by-product could produce environmentally durable concrete with similar properties of normal concrete. In the current research, SCC was produced by blending Cement Kiln Dust (CK...

Electrically conductive Portland cement concrete.

Science.gov (United States)

1986-01-01

There is a need for an effective, simple-to-install secondary anode system for use in the cathodic protection of reinforced concrete bridge decks. In pursuit of such a system, carbon fibers and carbon black were incorporated in portland cement concre...

The characterization of cement waste form for final disposal of decommissioning concrete wastes

International Nuclear Information System (INIS)

Lee, Yoon-ji; Lee, Ki-Won; Min, Byung-Youn; Hwang, Doo-Seong; Moon, Jei-Kwon

2015-01-01

Highlights: • Decommissioning concrete waste recycling and disposal. • Compressive strength of cement waste form. • Characteristic of thermal resistance and leaching of cement waste form. - Abstract: In Korea, the decontamination and decommissioning of KRR-1, 2 at KAERI have been under way. The decommissioning of the KRR-2 was finished completely by 2011, whereas the decommissioning of KRR-1 is currently underway. A large quantity of slightly contaminated concrete waste has been generated from the decommissioning projects. The concrete wastes, 83ea of 200 L drums, and 41ea of 4 m 3 containers, were generated in the decommissioning projects. The conditioning of concrete waste is needed for final disposal. Concrete waste is conditioned as follows: mortar using coarse and fine aggregates is filled with a void space after concrete rubble pre-placement into 200 L drums. Thus, this research developed an optimizing mixing ratio of concrete waste, water, and cement, and evaluated the characteristics of a cement waste form to meet the requirements specified in the disposal site specific waste acceptance criteria. The results obtained from a compressive strength test, leaching test, and thermal cycling test of cement waste forms conclude that the concrete waste, water, and cement have been suggested as an optimized mixing ratio of 75:15:10. In addition, the compressive strength of the cement waste form was satisfied, including a fine powder up to a maximum of 40 wt% in concrete debris waste of about 75%. According to the scale-up test, the mixing ratio of concrete waste, water, and cement is 75:10:15, which meets the satisfied compressive strength because of an increase in the particle size in the waste

Flexural strength of structural concrete repaired with HBPMM cement

International Nuclear Information System (INIS)

Memon, G.H.; Khaskheli, G.B.; Kumar, A.

2009-01-01

To repair damaged concrete structures, Dadabhoy Cement Factory in Sindh has launched a product known as HBPMM (Hi-Bond Polymer Modified Mortar) cement. HBPMM is used to repair various concrete structures in Pakistan but the experimental back up regarding the real performance of the product, as far as flexural strength of concrete is concerned, is not well known yet. This study is thus aimed to investigate the flexural strength of structural concrete repaired with HBPMM compared to that repaired with OPC (Ordinary Portland Cement). In total 32 concrete beams (6x6x18) having compressive strength of 3000 and 5000 psi were manufactured. To obtain flexural strength of the beams, these were splitted by using a UTM (Universal Testing Machine). Beams were then repaired with different applications of HBPMM and OPC. After 28 days of curing, the repaired beams were re-splitted to determine the flexural strength of repaired beams. Results show that both HBPMM and OPC are not very effective. However, the performance of HBPMM remained slightly better than that of OPC. Both OPC and HBPMM remained more efficient in case of 5000 psi concrete than that of 3000 psi concrete. Flexural strength of repaired beams could be increased by increasing application of the repairing material. (author)

Effect of Water-Cement Ratio on Pore Structure and Strength of Foam Concrete

Directory of Open Access Journals (Sweden)

Zhongwei Liu

2016-01-01

Full Text Available Foam concrete with different dry densities (400, 500, 600, 700, and 800 kg/m3 was prepared from ordinary Portland cement (P.O.42.5R and vegetable protein foaming agent by adjusting the water-cement ratio through the physical foaming method. The performance of the cement paste adopted, as well as the structure and distribution of air pores, was characterized by a rheometer, scanning electron microscope, vacuum water saturation instrument, and image analysis software. Effects of the water-cement ratio on the relative viscosity of the cement paste, as well as pore structure and strength of the hardened foam concrete, were discussed. Results showed that water-cement ratio can influence the size, distribution, and connectivity of pores in foam concrete. The compressive strength of the foam concrete showed an inverted V-shaped variation law with the increase in water-cement ratio.

STRESS-STRAIN STATE OF ROCKFILL DAM DOUBLE-LAYER FACE MADE OF REINFORCED CONCRETE AND SOIL-CEMENT CONCRETE

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Sainov Mikhail Petrovich

2017-05-01

Full Text Available There was studied the stress-strain state of 215 m high rockfill dam where the seepage-control element is presented by a reinforced concrete face of soil-cement concrete placed on the under-face zone. Calculations were carried out for two possible variants of deformability of rock outline taking into account the non-linearity of its deformative properties. It was obtained that the reinforced concrete face and the soil-cement concrete under-face zone work jointly as a single construction - a double-layer face. As the face assembly resting on rock is made with a sliding joint the scheme of its static operation is similar to the that of the beam operation on the elastic foundation. At that, the upstream surface of the double-layer face is in the compressed zone and lower one is in the tensile zone. This protects the face against cracking on the upstream surface but threatens with structural failure of soil-cement concrete. In order to avoid appearance of cracks in soil-cement concrete part due to tension it is necessary to achieve proper compaction of rockfill and arrange transverse joints in the double-layer face.

The characterization of cement waste form for final disposal of decommissioned concrete waste

International Nuclear Information System (INIS)

Lee, K.W.; Lee, Y.J.; Hwang, D.S.; Moon, J.K.

2015-01-01

Since the decommissioning of nuclear plants and facilities, large quantities of slightly contaminated concrete waste have been generated. In Korea, the decontamination and decommissioning of the KRR-1, 2 at the KAERI have been under way. In addition, 83 drums of 200 l, and 41 containers of 4 m 3 of concrete waste were generated. Conditioning of concrete waste is needed for final disposal. Concrete waste is conditioned as follows: mortar using coarse and fine aggregates is filled into a void space after concrete rubble pre-placement into 200 l drums. Thus, this research developed an optimizing mixing ratio of concrete waste, water, and cement, and evaluated the characteristics of a cement waste form to meet the requirements specified in the disposal site specific waste acceptance criteria. The results obtained from compressive strength test, leaching test, and thermal cycling test of cement waste forms conclude that the concrete waste, water, and cement have been suggested to have 75:15:10 as the optimized mixing ratio. In addition, the compressive strength of cement waste form was satisfied, including fine powder up to a maximum 40 wt% in concrete debris waste of about 75%. (authors)

Radiological impact of cement, concrete and admixtures in Spain

International Nuclear Information System (INIS)

Chinchon-Paya, S.; Piedecausa, B.; Hurtado, S.; Sanjuan, M.A.; Chinchon, S.

2011-01-01

It has been analyzed samples of portland cement (PC) with and without admixtures, samples of calcium aluminate cement (CAC) with different content of Al 2 O 3 and specimens of concrete made with PC and CAC using High Resolution Gamma Spectrometry. The activity concentration index (I) is much less than 0.5 mSv y -1 for all the concrete specimens according to the Radiation protection document 112 of the European Commission. The PC without admixtures (CEM I 52,5 R) and the PC with addition of limestone (CEM II/BL 32,5 N) also have an I value much lower than 0.5 and the PC with the addition of fly ash and blast furnace slag (CEM IV/B (V) 32,5 N and III/A 42.5 N/SR) have an I value close to 0.6. The I value of the CAC used in the manufacture of structural precast concrete is of the order of 1 mSv y -1 . Some of the CAC used in refractory concrete reaches a value close to 2 mSv y -1 . - Highlights: → The activity values (I) of spanish portland cement and admixtures studied are similar to those described by other authors. → For the first time in scientific publications we have shown results of several calcium aluminate cements (CAC). → CAC used in structural concrete has an approximate I value = 1 (similar to blast furnace slag and fly ash). → One type of CAC with Al 2 O 3 content of 51% used in refractory concretes has a value of I = 2.

Comparison of modified sulfur cement and hydraulic cement for encapsulation of radioactive and mixed wastes

International Nuclear Information System (INIS)

Kalb, P.D.; Heiser, J.H. III; Colombo, P.

1990-01-01

The majority of solidification/stabilization systems for low-level radioactive waste (LLW) and mixed waste, both in the commercial sector and at Department of Energy (DOE) facilities, utilize hydraulic cement (such as portland cement) to encapsulate waste materials and yield a monolithic solid waste form for disposal. Because hydraulic cement requires a chemical hydration reaction for setting and hardening, it is subject to potential interactions between elements in the waste and binder that can retard or prevent solidification. A new and innovative process utilizing modified sulfur cement developed by the US Bureau of Mines has been applied at Brookhaven National Laboratory (BNL) for the encapsulation of many of these problem wastes. Modified sulfur cement is a thermoplastic material, and as such, it can be heated above its melting point, combined with dry waste products to form a homogeneous mixture, and cooled to form a monolithic solid product. Under sponsorship of the DOE, research and development efforts at BNL have successfully applied the modified sulfur cement process for treatment of a range of LLWs including sodium sulfate salts, boric acid salts, and incinerator bottom ash and for mixed waste contaminated incinerator fly ash. Process development studies were conducted to determine optimal waste loadings for each waste type. Property evaluation studies were conducted to test waste form behavior under disposal conditions by applying relevant performance testing criteria established by the Nuclear Regulatory Commission (for LLW) and the Environmental Protection Agency (for hazardous wastes). Based on both processing and performance considerations, significantly greater waste loadings were achieved using modified sulfur cement when compared with hydraulic cement. Technology demonstration of the modified sulfur cement encapsulation system using production-scale equipment is scheduled for FY 1991

Ageing of portland cement concrete cured under moist conditions

NARCIS (Netherlands)

Yu, Z.; Ye, G.; Van Breugel, K.; Chen, W.

2014-01-01

Deterioration of microstructure in cement concrete will cause changes in the transport properties of the concrete. Transport properties at different ages of the concrete provide information about the microstructural changes of the material. A way to measure the transport properties, i.e. the

Production of more durable and sustainable concretes using volcanic scoria as cement replacement

International Nuclear Information System (INIS)

Al-Swaidani, A. M.

2017-01-01

The objective of the study is to investigate strength and durability-related properties of volcanic scoria-based cements. Compressive and tensile strength development of mortars and concretes containing volcanic scoria with replacement levels ranging from 10 to 35% was investigated. Water permeability, chloride penetrability and porosity of concretes cured for 2, 7, 28, 90 and 180 days were also examined. Results revealed that volcanic scoria could be suitable for making blended cements. The strength of mortar/concrete containing volcanic scoria was lower than that of plain cement mortar/concrete at all ages. However, at 90 day curing, the strengths of volcanic scoria-based mortars/concretes were comparable to those of plain cement. In addition, water permeability, chloride penetrability and porosity of scoria-based concretes were much lower than those of plain concrete. Further, the results were statistically analysed and estimation equations have been developed to predict the studied properties. SEM/EDX analysis was employed, as well. [es

Cement and concrete options paper

International Nuclear Information System (INIS)

1999-10-01

Greenhouse gas emissions associated with the production of concrete are projected to increase from 10.5 million tonnes in 1990 to almost 14 million tonnes in 2010. Over half of this amount will be non-energy related emissions of carbon dioxide resulting from the conversion of limestone to lime. According to this report by industry experts, the industry has an excellent record of improving energy efficiency and there are few easy gains remaining. Nevertheless, improvements in energy efficiency and fuel use, increased use of concrete where it can be shown to result in net reduction of GHG emissions, and partial replacement of cement by supplementary cementitious materials that involve no additional generation of GHGs, could yield an approximate reduction in carbon dioxide emissions of nearly seven million tons in 2010. The industry proposes three measures to realise these benefits: (1) encouraging replacement of fossil fuels by otherwise waste material, (2) encouraging increased use of concrete in constructing houses and roads, and (3) encouraging increased use of supplementary cementing materials. The industry is opposed to carbon or energy taxes that increase the cost of doing business, on the grounds that such taxes would adversely affect the industry's competitive position internationally. tabs

Design and application of environmentally effective concrete with usage of chrysotile-cement waste

OpenAIRE

Egorova Lada; Semenov Vyacheslav; Pligina Anna; Askhadullin Aizat

2016-01-01

Construction is resource-demanding industry, characterized by a large volume of waste. Particularly chrysotile cement waste obtained both in production and in dismantling over age chrysotile-cement products: corrugated asbestos boards and flat sheets, chrysotile-cement tubes. We propose to use dry chrysotile-cement waste as recycled aggregate for concrete. Based on developed compositions and identified properties of heavy concrete with chrysotile-cement waste introduce this technology to the ...

Effects of Admixtures on the Properties of Corn Cob Ash Cement Concrete

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Akeem Ayinde RAHEEM

2010-12-01

Full Text Available The study investigated the effects of admixtures on the properties of corn cob ash (CCA cement concrete. The workability and compressive strength of CCA cement concrete incorporated with accelerator, plasticizer and water reducing and retarding were carried out. The dosage of admixture incorporated was: 0.124litre per 15.55kg of cementitious material based on the recommendation by BS EN 934-2.The results revealed that admixtures generally improve the workability of corn cob ash cement concrete. The compressive strength obtained at 28th day for concrete without admixture (The Control was 29.82N/mm2, while for concrete with accelerator, plasticizer, and water reducing and retarding it was 32.80 N/mm2, 38.51 N/mm2 and 34.09 N/mm2 respectively. These results showed that CCA cement concrete incorporated with accelerator achieved greater strength at early ages. With plasticizer, it achieved very high strength at both young and old ages; while with water reducing and retarding it achieved greater strength at old ages alone.

Analysis of CCRL proficiency cements 151 and 152 using the Virtual Cement and Concrete Testing Laboratory

International Nuclear Information System (INIS)

Bullard, Jeffrey W.; Stutzman, Paul E.

2006-01-01

To test the ability of the Virtual Cement and Concrete Testing Laboratory (VCCTL) software to predict cement hydration properties, characterization of mineralogy and phase distribution is necessary. Compositional and textural characteristics of Cement and Concrete Reference Laboratory (CCRL) cements 151 and 152 were determined via scanning electron microscopy (SEM) analysis followed by computer modeling of hydration properties. The general procedure to evaluate a cement is as follows: (1) two-dimensional SEM backscattered electron and X-ray microanalysis images of the cement are obtained, along with a measured particle size distribution (PSD); (2) based on analysis of these images and the measured PSD, three-dimensional microstructures of various water-to-cement ratios are created and hydrated using VCCTL, and (3) the model predictions for degree of hydration under saturated conditions, heat of hydration (ASTM C186), setting time (ASTM C191), and strength development of mortar cubes (ASTM C109) are compared to experimental measurements either performed at NIST or at the participating CCRL proficiency sample evaluation laboratories. For both cements, generally good agreement is observed between the model predictions and the experimental data

Modification of cement concrete by multilayer carbon nano-tubes

International Nuclear Information System (INIS)

Yakovlev, G.I.; Pervushin, G.N.; Pudov, I.A.; Korzhenko, A.

2012-01-01

The compact structure of protective concrete-conservative on the basis of Portland cement modified by carbon nano-dispersed systems has been studied. Multilayer carbon nano-tubes Graphistrength TM by 'Arkema' dispersed in hydrodynamic plant in the solution of surfactant Polyplast SP-1 have been used as modifying additives. The bending strength of fine grain concrete has been observed to increase by 45.1% and compression strength - by 96.8%. The concrete strength increase is related to morphological changes of crystalline hydrate new formations providing the formation of less defective structure of cement matrix of high density, preventing the migration of radionuclides into the environment in the process of radioactive waste conservation

Changes of strength characteristics of pervious concrete due to variations in water to cement ratio

Science.gov (United States)

Kovac, M.; Sicakova, A.

2017-10-01

Pervious concrete is considered to be a sustainable pavement material due to high water permeability. The experiment presented in this paper was aimed at study the influence of water to cement ratio on both the compressive and splitting tensile strength of pervious concrete. Typically, less water content in concrete mixture leads to less porosity of cement paste and thus it provides desirable mechanical properties. In case of conventional dense concrete, the lower is the water to cement ratio, the higher or better is the strength, density and durability of concrete. This behaviour is not quite clear in case of pervious concrete because of low amount of cement paste present. Results of compressive and splitting tensile strength of pervious concrete are discussed in the paper while taking into account values measured after 2 and 28 days of hardening and variations in water to cement ratio. The results showed that changes of water to cement ratio from 0.25 to 0.35 caused only slight differences in strength characteristics, and this applied to both types of tested strength.

Design and application of environmentally effective concrete with usage of chrysotile-cement waste

Directory of Open Access Journals (Sweden)

Egorova Lada

2016-01-01

Full Text Available Construction is resource-demanding industry, characterized by a large volume of waste. Particularly chrysotile cement waste obtained both in production and in dismantling over age chrysotile-cement products: corrugated asbestos boards and flat sheets, chrysotile-cement tubes. We propose to use dry chrysotile-cement waste as recycled aggregate for concrete. Based on developed compositions and identified properties of heavy concrete with chrysotile-cement waste introduce this technology to the production of foundation wall blocks. The studies confirmed the possibility of using chrysotile-cement aggregate and fine screening of crushing as a secondary coarse and fine aggregates for concrete with proper quality without increasing the cost of the product. Environmental safety of the obtained products was ensured. The direction for implementation of the research project was proposed.

Effects of Particle Size and Cement Replacement of LCD Glass Powder in Concrete

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Seong Kyum Kim

2017-01-01

Full Text Available The high quality liquid crystal display (LCD processing waste glass (LPWG generated from the manufacturing process of Korea’s LCD industries, having the world’s highest technological level and production, was finely ground into particles smaller than cement particles (higher fineness than OPC to verify their applicability and performance as a replacement for cement. For a concrete mix having a W/B ratio of 0.44, cement was replaced with LPWG glass powder (LGP at ratios of 5, 10, 15, and 20% (LGP12 and 5 and 10% (LGP5 according to the particle size to prepare test cylinder specimens, which were tested with respect to air contents, slump in fresh concrete, and compressive strength and splitting tensile strength of hardened concrete. The microstructure of the concrete specimens was analyzed through Scanning Electron Microscopy (SEM, Energy Dispersive X-ray (EDX, and a Mercury Intrusion Porosimetry (MIP. Replacement of cement with LGP for cement could effectively decrease the quantity of cement used due to the excellent performance of LGP. It may positively contribute to the sustainable development of the cement industry as well as waste recycling and environment conservation on a national scale.

Potential Mixture of POFA and SCBA as Cement Replacement in Concrete – A Review

Directory of Open Access Journals (Sweden)

Ali Noorwirdawati

2017-01-01

Full Text Available Concrete is an important material used in all kind of building construction and ordinary Portland cement (OPC is one of an important element in the production of concrete. However, the production of cement causes a problem because of high CO2 emission to atmosphere. The manufacture of 1 tonnes of cement would produce approximately released 1 tonnes of CO2. So, the need to search another material that can replace a cement with same properties and environmental friendly are crucial. The suitable material to replace cement has to be a pozzolanic materials. This is because pozzolanic materials has cementitious properties and high silica content. Palm oil fuel ash (POFA and sugarcane bagasse ash (SCBA are the material that suitable to replace cement because of high silica content. The use of POFA and SCBA in concrete has been studied by many researcher and it has been proved to improve the mechanical strength of the concrete either in normal concrete, high strength concrete or lightweight concrete. This paper would discuss the overview of the previous study on the cement replacement by POFA and SCBA and the potential of the both materials to be mix together to improve its properties. The chemical element which will be the focus point is SiO4, MgO, CaO and SO3, while the physical and mechanical properties such as workability, specific gravity, compressive strength and tensile strength will also be reviewed.

Properties, sustainability and elevated temperature behavior of concrete containing Portland limestone cement

Science.gov (United States)

El-Hawary, Moetaz; Ahmed, Mahmoud

2017-09-01

The utilization of some type of cheap filler as partial cement replacement is an effective way of improving concrete sustainability. With the recent trends to reduce water to cement ratio and improve compaction, there is no enough space or water for complete hydration of cement. This means that actually, a portion of mixed cement acts as expensive filler. Replacing this portion with cheaper filler that requires less energy to produce is, therefore, beneficial. Crushed limestone is the most promising filler. This work is to investigate the effect of the amount of limestone fillers on the sustainability and the fresh and mechanical properties of the resulting concrete. A rich mix is designed with a low water/cement ratio of 0.4. Lime is introduced as a replacement percentage of cement. Ratios of 0, 10, 20 and 30% were used. Slump, compressive strength, specific gravity and water absorption are evaluated for every mix. In addition, the effect of the amount of lime on the residual strength of concrete subjected to elevated temperatures is also investigated. Samples are subjected to six different temperature stations of 20, 100, 200, 300, 500 and 700°C for six hours before being cooled and subsequently tested for compressive strength and specific gravity. Sustainability of the tested mixes is evaluated through reductions in the emitted carbon dioxide, energy and reduction in cost. Based on the annual use of concrete in Kuwait, the sustainability benefits resulting from the use of limestone filler in Kuwait are evaluated and assessed. The paper is concluded with the recommendation of the use of 15% limestone filler as partial cement replacement where the properties and the behavior under high temperature of the resulting concrete are almost the same as those of conventional concrete with considerable cost and sustainability benefits.

Potential of Carbon Nanotube Reinforced Cement Composites as Concrete Repair Material

Directory of Open Access Journals (Sweden)

Tanvir Manzur

2016-01-01

Full Text Available Carbon nanotubes (CNTs are a virtually ideal reinforcing agent due to extremely high aspect ratios and ultra high strengths. It is evident from contemporary research that utilization of CNT in producing new cement-based composite materials has a great potential. Consequently, possible practical application of CNT reinforced cementitious composites has immense prospect in the field of applied nanotechnology within construction industry. Several repair, retrofit, and strengthening techniques are currently available to enhance the integrity and durability of concrete structures with cracks and spalling, but applicability and/or reliability is/are often limited. Therefore, there is always a need for innovative high performing concrete repair materials with good mechanical, rheological, and durability properties. Considering the mechanical properties of carbon nanotubes (CNTs and the test results of CNT reinforced cement composites, it is apparent that such composites could be used conveniently as concrete repair material. With this end in view, the applicability of multiwalled carbon nanotube (MWNT reinforced cement composites as concrete repair material has been evaluated in this study in terms of setting time, bleeding, and bonding strength (slant shear tests. It has been found that MWNT reinforced cement mortar has good prospective as concrete repair material since such composites exhibited desirable behavior in setting time, bleeding, and slant shear.

A micromechanical four-phase model to predict the compressive failure surface of cement concrete

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A. Caporale,

2014-07-01

Full Text Available In this work, a micromechanical model is used in order to predict the failure surface of cement concrete subject to multi-axial compression. In the adopted model, the concrete material is schematised as a composite with the following constituents: coarse aggregate (gravel, fine aggregate (sand and cement paste. The cement paste contains some voids which grow during the loading process. In fact, the non-linear behavior of the concrete is attributed to the creation of cracks in the cement paste; the effect of the cracks is taken into account by introducing equivalent voids (inclusions with zero stiffness in the cement paste. The three types of inclusions (namely gravel, sand and voids have different scales, so that the overall behavior of the concrete is obtained by the composition of three different homogenizations; in the sense that the concrete is regarded as the homogenized material of the two-phase composite constituted of the gravel and the mortar; in turn, the mortar is the homogenized material of the two-phase composite constituted of the sand inclusions and a (porous cement paste matrix; finally, the (porous cement paste is the homogenized material of the two-phase composite constituted of voids and the pure paste. The pure paste represents the cement paste before the loading process, so that it does not contain voids or other defects due to the loading process. The abovementioned three homogenizations are realized with the predictive scheme of Mori-Tanaka in conjunction with the Eshelby method. The adopted model can be considered an attempt to find micromechanical tools able to capture peculiar aspects of the cement concrete in load cases of uni-axial and multi-axial compression. Attributing the non-linear behavior of concrete to the creation of equivalent voids in the cement paste provides correspondence with many phenomenological aspects of concrete behavior. Trying to improve this correspondence, the influence of the parameters of the

Low-shrink airfield cement concrete with respect to thermal resistance

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Linek Małgorzata

2017-01-01

Full Text Available The paper presents theoretical background to the occurrence and propagation of imposed thermal load deep inside the structure of airfield pavement. The standard composition of low-shrink cement concrete intended for airfield pavements was presented. The influence of recurring temperature changes on the extent of shrinkage deformations was assessed. The obtained lab test results, combined with observations and analysis of changes of the hardened concrete microstructure, allowed the authors to draw conclusions. It was proven that the suggested concrete mix composition makes it possible to obtain the concrete type of better developed internal microstructure. More micro air voids and reduced distance between the voids were proven, which provides increased frost resistance of concrete. The change of size, structure and quantity of the hydration products in the cement matrix and better developed contact sections resulted in the improvement of the mechanical parameters of hardened concrete. Low-shrink concrete in all analysed cases proved to have increased resistance to the variable environmental conditions. Increased concrete resistance is identified through reduced registered shrinkage deformations and growth of mechanical parameters of concrete. Low-shrink concrete used for airfield structure guarantees extended time of reliable pavement operation.

Estimation of minimum detectable concentration of chlorine in the blast furnace slag cement concrete

Energy Technology Data Exchange (ETDEWEB)

Naqvi, A.A., E-mail: aanaqvi@kfupm.edu.s [Department of Physics, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia); Maslehuddin, M. [Center for Engineering Research, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia); Garwan, M.A.; Nagadi, M.M. [Department of Physics, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia); Al-Amoudi, O.S.B. [Department of Civil Engineering, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia); Khateeb-ur-Rehman,; Raashid, M. [Department of Physics, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia)

2011-01-01

The Prompt Gamma Neutron Activation Analysis technique was used to measure the concentration of chloride in the blast furnace slag (BFS) cement concrete to assess the possibility of reinforcement corrosion. The experimental setup was optimized using Monte Carlo calculations. The BFS concrete specimens containing 0.8-3.5 wt.% chloride were prepared and the concentration of chlorine was evaluated by determining the yield of 6.11, 6.62, 7.41, 7.79 and 8.58 MeV gamma-rays. The Minimum Detectable Concentration (MDC) of chlorine in the BFS cement concrete was estimated. The best value of MDC limit of chlorine in the BFS cement concrete was found to be 0.034 {+-} 0.011 and 0.038 {+-} 0.012 wt.% for 6.11 and 6.62 MeV prompt gamma-rays. Within the statistical uncertainty the lower bound of the measured MDC of chlorine in the BFS cement concrete meets the maximum permissible limit of 0.03 wt.% of chloride set by the American Concrete Institute.

Concrete research using blended cements

International Nuclear Information System (INIS)

Butler, W.B.

2001-01-01

Concrete research increasingly involves the use of mixes containing one or more of the supplementary cementitious materials (SCMs), often in conjunction with chemical admixtures. The influence of materials is commonly evaluated on the basis of water/ cement or water/ binder ratio and SCM content as a percentage of total binder, with dosage level of chemical admixture varied to maintain workability. As a result, more than one variable is introduced at a time and the objectives of the research may not be achieved. The significance of water/ cement ratio and addition rates of admixtures are examined from a practical standpoint with suggestions for more appropriate means of evaluation of the influence of individual materials. Copyright (2001) The Australian Ceramic Society

STRESSES IN CEMENT-CONCRETE PAVEMENT SURFACING CAUSED BY THERMAL SHOCK

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M. K. Pshembaev

2016-01-01

Full Text Available It is necessary to mention specially so-called thermal shock among various impacts on highway surface. Ice layer is formed on a concrete surface during the winter period of pavement surfacing operation. Sodium chloride which lowers temperature of water-ice transition temperature and causes ice thawing at negative temperature is usually used to remove ice from the pavement surface. Consequently, temperature in the concrete laying immediately under a thawing ice layer is coming down with a run that leads to significant stresses. Such phenomenon is known as a thermal shock with a meaning of local significant change in temperature. This process is under investigation, it has practical importance for an estimation of strength and longevity of a cement-concrete pavement surfacing and consequently it is considered as rather topical issue. The purpose of investigations is to develop a mathematical model and determination of shock blow permissible gradients for a cementconcrete road covering. Finite difference method has been used in order to determine stressed and deformed condition of the cement-concrete pavement surfacing of highways. A computer program has been compiled and it permits to carry out calculation of a road covering at various laws of temperature distribution in its depth. Regularities in distribution of deformation and stresses in the cement-concrete pavement surfacing of highways at thermal shock have been obtained in the paper. A permissible parameter of temperature distribution in pavement surfacing thickness has been determined in the paper. A strength criterion based on the process of micro-crack formation and development in concrete has been used for making calculations. It has been established that the thermal shock causes significant temperature gradients on the cement-concrete surfacing that lead to rather large normal stresses in the concrete surface layer. The possibility of micro-crack formation in a road covering is

TECHNOLOGY AND EFFICIENCY OF PEAT ASH USAGE IN CEMENT CONCRETE

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G. D. Liakhevich

2015-01-01

Full Text Available One of the main ways to improve physical and mechanical properties of cement concrete is an introduction of ash obtained due to burning of fossil fuels into concrete mix. The concrete mixes with ash are characterized by high cohesion, less water gain and disintegration. At the same time the concrete has high strength, density, water resistance, resistance to sulfate corrosion. The aim of this paper is to explore the possibility to use peat ash and slag of peat enterprises of the Republic of Belarus in the concrete for improvement of its physical and mechanical properties and characteristics of peat ash, slag, micro-silica, cement, superplasticizing agent. Compositions and technology for preparation of concrete mixes have been developed and concrete samples have been have been fabricated and tested in the paper. It has been shown that the concrete containing ash, slag obtained due to burning of peat in the industrial installations of the Usiazhsky and Lidsky Peat Briquette Plants and also MK-85-grade micro-silica NSPKSAUsF-1-grade superplasticizing agent have concrete tensile strength within 78–134 MPa under axial compression and 53 MPa – for the control composition. This index is 1.5–2.5 times more than for the sample containing no additives.The usage of peat ash, slag together with MK-85-grade micro-silica and NSPKSAUsF-1-grade superplasticizing agent for fabrication of concrete and reinforced bridge and tunnel structures will provide the following advantages: reduction of cross-sectional area of structures while maintaining their bearing capacity due to higher value of tensile strength in case of axial compression; higher density, waterand gas tightness due to low water cement ratio; high resistance to aggressive environment due to lower content of capillary pores that ensures bridge structure longevity; achievement of environmental and social impacts.

Preparation of hydraulic cement from oil-shale

Energy Technology Data Exchange (ETDEWEB)

1921-08-28

A process for the preparation of hydraulic cement from oil-shale or oil-shale residue is characterized in that, the oil-shale or shale-coke together with a slight amount of marl is burned under sintering conditions and the residue obtained is ground to a fine dust.

Contrastive Numerical Investigations on Thermo-Structural Behaviors in Mass Concrete with Various Cements

Science.gov (United States)

Zhou, Wei; Feng, Chuqiao; Liu, Xinghong; Liu, Shuhua; Zhang, Chao; Yuan, Wei

2016-01-01

This work is a contrastive investigation of numerical simulations to improve the comprehension of thermo-structural coupled phenomena of mass concrete structures during construction. The finite element (FE) analysis of thermo-structural behaviors is used to investigate the applicability of supersulfated cement (SSC) in mass concrete structures. A multi-scale framework based on a homogenization scheme is adopted in the parameter studies to describe the nonlinear concrete behaviors. Based on the experimental data of hydration heat evolution rate and quantity of SSC and fly ash Portland cement, the hydration properties of various cements are studied. Simulations are run on a concrete dam section with a conventional method and a chemo-thermo-mechanical coupled method. The results show that SSC is more suitable for mass concrete structures from the standpoint of temperature control and crack prevention. PMID:28773517

Optimizing the hydraulic program of cementing casing strings

Energy Technology Data Exchange (ETDEWEB)

Novakovic, M

1984-01-01

A technique is described for calculating the optimal parameters of the flow of plugging mud which takes into consideration the geometry of the annular space and the rheological characteristics of the muds. The optimization algorithm was illustrated by a block diagram. Examples are given for practical application of the optimization programs in production conditions. It is stressed that optimizing the hydraulic cementing program is effective if other technical-technological problems in cementing casing strings have been resolved.

Influence of particle packing density on the rheology of low cement content concrete

NARCIS (Netherlands)

Fennis-Huijben, S.A.A.M.; Grunewald, S.; Walraven, J.C.; Den Uijl, J.A.

2012-01-01

Optimizing concrete mixtures with regard to cement content is one of the most important solutions in sustainable concrete design. Workability o f these low cement content or ecological mixtures is very important. Eleven mortar mixtures are presented, which show how a higher packing density can be

Properties of Non-Structural Concrete Made with Mixed Recycled Aggregates and Low Cement Content.

Science.gov (United States)

López-Uceda, Antonio; Ayuso, Jesús; López, Martin; Jimenez, José Ramón; Agrela, Francisco; Sierra, María José

2016-01-26

In spite of not being legally accepted in most countries, mixed recycled aggregates (MRA) could be a suitable raw material for concrete manufacturing. The aims of this research were as follows: (i) to analyze the effect of the replacement ratio of natural coarse aggregates with MRA, the amount of ceramic particles in MRA, and the amount of cement, on the mechanical and physical properties of a non-structural concrete made with a low cement content; and (ii) to verify if it is possible to achieve a low-strength concrete that replaces a greater amount of natural aggregate with MRA and that has a low cement content. Two series of concrete mixes were manufactured using 180 and 200 kg/m³ of CEM II/A-V 42.5 R type Portland cement. Each series included seven concrete mixes: one with natural aggregates; two MRA with different ceramic particle contents; and one for each coarse aggregate replacement ratio (20%, 40%, and 100%). To study their properties, compressive and splitting tensile strength, modulus of elasticity, density, porosity, water penetration, and sorptivity, tests were performed. The results confirmed that the main factors affecting the properties analyzed in this research are the amount of cement and the replacement ratio; the two MRAs used in this work presented a similar influence on the properties. A non-structural, low-strength concrete (15 MPa) with an MRA replacement ratio of up to 100% for 200 kg/m³ of cement was obtained. This type of concrete could be applied in the construction of ditches, sidewalks, and other similar civil works.

Micro Mechanics and Microstructures of Major Subsurface Hydraulic Barriers: Shale Caprock vs Wellbore Cement

Science.gov (United States)

Radonjic, M.; Du, H.

2015-12-01

Shale caprocks and wellbore cements are two of the most common subsurface impermeable barriers in the oil and gas industry. More than 60% of effective seals for geologic hydrocarbon bearing formations as natural hydraulic barriers constitute of shale rocks. Wellbore cements provide zonal isolation as an engineered hydraulic barrier to ensure controlled fluid flow from the reservoir to the production facilities. Shale caprocks were deposited and formed by squeezing excess formation water and mineralogical transformations at different temperatures and pressures. In a similar process, wellbore cements are subjected to compression during expandable tubular operations, which lead to a rapid pore water propagation and secondary mineral precipitation within the cement. The focus of this research was to investigate the effect of wellbore cement compression on its microstructure and mechanical properties, as well as a preliminary comparison of shale caprocks and hydrated cement. The purpose of comparative evaluation of engineered vs natural hydraulic barrier materials is to further improve wellbore cement durability when in contact with geofluids. The micro-indentation was utilized to evaluate the change in cement mechanical properties caused by compression. Indentation experiments showed an overall increase in hardness and Young's modulus of compressed cement. Furthermore, SEM imaging and Electron Probe Microanalysis showed mineralogical alterations and decrease in porosity. These can be correlated with the cement rehydration caused by microstructure changes as a result of compression. The mechanical properties were also quantitatively compared to shale caprock samples in order to investigate the similarities of hydraulic barrier features that could help to improve the subsurface application of cement in zonal isolation. The comparison results showed that the poro-mechanical characteristics of wellbore cement appear to be improved when inherent pore sizes are shifted to

Effect of supplementary cementing materials on the concrete corrosion control

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Mejía de Gutiérrez, R.

2003-12-01

Full Text Available Failure of concrete after a period of years, less than the life expected for which it was designed, may be caused by the environment to which it has been exposed or by a variety of internal causes. The incorporation of supplementary materials has at the Portland cement the purpose of improving the concrete microstructure and also of influence the resistance of concrete to environmental attacks. Different mineral by-products as ground granulated blast furnace slag (GGBS, silica fume (SF, metakaolin (MK, fly ash (FA and other products have been used as supplementary cementing materials. This paper is about the behavior of concrete in the presence of mineral additions. Compared to Portland cements, blended cements show lower heat of hydration, lower permeability, greater resistance to sulphates and sea water. These blended cements find the best application when requirements of durability are regarded as a priority specially on high performance concrete.

La falla del concreto en un tiempo inferior a la vida útil para la cual se diseñó puede ser consecuencia del medio ambiente al cual ha estado expuesto o de algunas otras causas de tipo interno. La incorporación de materiales suplementarios al cemento Portland tiene el propósito de mejorar la microestructura del concreto y también de contribuir a la resistencia del concreto a los ataques del medio ambiente. Diferentes minerales y subproductos tales como escorias granuladas de alto horno, humo de sílice, metacaolín, ceniza volante y otros productos han sido usados como materiales suplementarios cementantes. Este documento presenta el comportamiento del hormigón en presencia de diferentes adiciones. Los cementos adicionados, comparados con los cementos Portland muestran bajos calores de hidratación, baja permeabilidad, mayor resistencia a sulfatos y a agua de mar. Estos cementos adicionados encuentran un campo de aplicación importante cuando los requerimientos de durabilidad son

Preparing hydraulic cement from oil-shale slag

Energy Technology Data Exchange (ETDEWEB)

1921-11-19

A process for the preparation of hydraulic cementing material from oil shale or oil-shale slag according to Patent 411,584 is characterized by the fact that the oil-shale slag is added to burnt marl, blast-furnace slag, and the like, whereupon the mixture is milled to dust in the known way.

Radon exhalation study from cement, cement slabs and concrete slabs with variation in fly ash

International Nuclear Information System (INIS)

Sharma, Nisha; Singh, Jaspal

2012-01-01

Fly ash is a waste product from coal-fired power plants. Fly ash has become a subject of world-wide interest in recent years because of its diverse uses, e.g. in the manufacture of concrete for building purposes, for the filling of underground cavities, or as a component of building material. The fly ash may contain enhanced levels of the natural radionuclides in the uranium and thorium series and by using the fly ash in building materials, the radiation levels in houses may thus be technologically enhanced. Because of its relatively high radionuclide contents (including 226 Ra), fly ash may, however, present a potential hazard to the population through its radon emanation, which would be highly undesirable. Since fly ash is frequently used as a building material, the idea of the experiment was to mix fly ash in different proportions in the cement in the powder form, cemented slabs and concrete slabs to study the combined behaviors. Alpha sensitive LR-115 type II plastic track detector, commonly known as Solid State Nuclear Track Detectors (SSNTDs), were used to measure the radon concentration. The alpha particles emitted from the radon causes the radiation damaged tracks. The chemical etching in NaOH at 60°C for about 90 minutes was done to reveal these latent tracks, which were then scanned and counted by an optical microscope of suitable magnification. By calculating the track density of registered tracks, the radon concentrations were determined. In case of cement in the powder form and in cemented slab, starting from the pure cement, fly ash was added up to 70% by weight. In this case the radon exhalation rate has increased by addition of fly ash in the cement and in case of concrete slabs by the addition of fly ash in the cement the radon exhalation increases up to 60% and then decreases. Therefore, on the basis of our investigations we concluded that in general radon exhalation rate increases with the addition of fly ash. (author)

Properties of Non-Structural Concrete Made with Mixed Recycled Aggregates and Low Cement Content

Science.gov (United States)

López-Uceda, Antonio; Ayuso, Jesús; López, Martin; Jimenez, José Ramón; Agrela, Francisco; Sierra, María José

2016-01-01

In spite of not being legally accepted in most countries, mixed recycled aggregates (MRA) could be a suitable raw material for concrete manufacturing. The aims of this research were as follows: (i) to analyze the effect of the replacement ratio of natural coarse aggregates with MRA, the amount of ceramic particles in MRA, and the amount of cement, on the mechanical and physical properties of a non-structural concrete made with a low cement content; and (ii) to verify if it is possible to achieve a low-strength concrete that replaces a greater amount of natural aggregate with MRA and that has a low cement content. Two series of concrete mixes were manufactured using 180 and 200 kg/m3 of CEM II/A-V 42.5 R type Portland cement. Each series included seven concrete mixes: one with natural aggregates; two MRA with different ceramic particle contents; and one for each coarse aggregate replacement ratio (20%, 40%, and 100%). To study their properties, compressive and splitting tensile strength, modulus of elasticity, density, porosity, water penetration, and sorptivity, tests were performed. The results confirmed that the main factors affecting the properties analyzed in this research are the amount of cement and the replacement ratio; the two MRAs used in this work presented a similar influence on the properties. A non-structural, low-strength concrete (15 MPa) with an MRA replacement ratio of up to 100% for 200 kg/m3 of cement was obtained. This type of concrete could be applied in the construction of ditches, sidewalks, and other similar civil works. PMID:28787874

Collaboration of polymer composite reinforcement and cement concrete

Science.gov (United States)

Khozin, V. G.; Gizdatullin, A. R.

2018-04-01

The results of experimental study of bond strength of cement concrete of different types with fiber reinforcing polymer (FRP) bars are reported. The reinforcing bars were manufactured of glass fibers and had a rebar with different types of the surface relief formed by winding a thin strip impregnated with a binder or by “sanding”. The pullout tests were carried out simultaneously for the steel reinforcing ribbed bars A400. The impact of friction, adhesion and mechanical bond on the strength of bonds between FRP and concrete was studied. The influence of the concrete strength and different operation factors on the bond strength of concrete was evaluated.

Influence of Aggregate Coated with Modified Sulfur on the Properties of Cement Concrete

Directory of Open Access Journals (Sweden)

Swoo-Heon Lee

2014-06-01

Full Text Available This paper proposes the mixing design of concrete having modified sulfur-coated aggregate (MSCA to enhance the durability of Portland cement concrete. The mechanical properties and durability of the proposed MSCA concrete were evaluated experimentally. Melting-modified sulfur was mixed with aggregate in order to coat the aggregate surface at a speed of 20 rpm for 120 s. The MSCA with modified sulfur corresponding to 5% of the cement weight did not significantly affect the flexural strength in a prism concrete beam specimen, regardless of the water-cement ratio (W/C. However, a dosage of more than 7.5% decreased the flexural strength. On the other hand, the MSCA considerably improved the resistance to the sulfuric acid and the freezing-thawing, regardless of the sulfur dosage in the MSCA. The coating modified sulfur of 5% dosage consequently led to good results for the mechanical properties and durability of MSCA concrete.

Eco-friendly GGBS Concrete: A State-of-The-Art Review

Science.gov (United States)

Saranya, P.; Nagarajan, Praveen; Shashikala, A. P.

2018-03-01

Concrete is the most commonly used material in the construction industry in which cement is its vital ingredient. Although the advantages of concrete are many, there are side effects leading to environmental issues. The manufacturing process of cement emits considerable amount of carbon dioxide (CO2). Therefore is an urgent need to reduce the usage of cement. Ground Granulated Blast furnace Slag (GGBS) is a by-product from steel industry. It has good structural and durable properties with less environmental effects. This paper critically reviews the literatures available on GGBS used in cement concrete. In this paper, the literature available on GGBS are grouped into engineering properties of GGBS concrete, hydraulic action of GGBS in concrete, durability properties of GGBS concrete, self- compacting GGBS concrete and ultrafine GGBS are highlighted. From the review of literature, it was found that the use of GGBS in concrete construction will be eco-friendly and economical. The optimum percentage of replacement of cement by GGBS lies between 40 - 45 % by weight. New materials that can be added in addition to GGBS for getting better strength and durability also highlighted.

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

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Xiao-Yong Wang

2017-01-01

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.

LOW WATER DEMAND CEMENTS - WAY OF EFFICIENT USE OF CLINKER AND MINERAL FILLERS IN CONCRETES

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Khokhryakov Oleg Viktorovich

2017-10-01

Full Text Available Subject: the provisions in the updated edition of the technical specifications for cements are analyzed. A trend to decrease the clinker volume in Portland cement due to the wider use of mineral additives, up to 95%, was observed. Research objectives: substantiation of the most complete and efficient use of Portland cement and mineral additives in the composition of low water demand cements. Materials and methods: portland cement, mineral additives and superplasticizer were used as raw materials for obtaining cements of low water demand. The experimental methods comply with the current standards. Results: comparative properties of low water demand cements and cements with mineral additives are presented. The properties of cement-water suspensions of these binders have been studied, and, on their basis, heavy concretes have been made. The results of the grindability of Portland cement and mineral components with a superplasticizer are given. Conclusions: it is shown that the cement of low water demand, in which the advantages of both Portland cement and mineral additives are more fully and efficiently presented, complies with the tendency to decrease the clinker volume to the greatest degree. It is established that the clinker volume index for heavy concrete prepared on low water demand cement is almost four times lower than that for heavy concrete based on common Portland cement.

Freezing temperature protection admixture for Portland cement concrete

Science.gov (United States)

1996-10-01

A number of experimental admixtures were compared to Pozzutec 20 admixture for their ability to protect fresh concrete from freezing and for increasing the rate of cement hydration at below-freezing temperatures. The commercial accelerator and low-te...

Upscaling the Use of Mixed Recycled Aggregates in Non-Structural Low Cement Concrete.

Science.gov (United States)

López-Uceda, Antonio; Ayuso, Jesús; Jiménez, José Ramón; Agrela, Francisco; Barbudo, Auxiliadora; De Brito, Jorge

2016-02-02

This research aims to produce non-structural concrete with mixed recycled aggregates (MRA) in upscaled applications with low-cement content. Four slabs were executed with concrete made with different ratios of coarse MRA (0%, 20%, 40% and 100%), using the mix design, the mixing procedures and the facilities from a nearby concrete production plant. The analysis of the long-term compressive and splitting tensile strengths in concrete cores, extracted from the slabs, allowed the highlighting of the long-term high strength development potential of MRA incorporation. The study of cast specimens produced in situ under the same conditions as the slabs showed, firstly, that the use of MRA has a great influence on the properties related to durability, secondly, that the loss of compressive strength for total MRA incorporation relative to control concrete increases proportionally with the class strength, and, thirdly, that the mechanical properties (including Schmidt hammer results) from the concrete slabs showed no significant differences relative to the control concrete for coarse aggregates replacements up to 40%. Therefore, this upscaled experimental study supports the application of concrete with 100% coarse MRA incorporation and low cement content in non-structural civil works such as bike lanes, gutters, ground slabs, leveling surfaces, and subgrades for foundations. To the best of the authors' knowledge, there have not been any upscaled applications of concrete with MRA and low cement content.

Upscaling the Use of Mixed Recycled Aggregates in Non-Structural Low Cement Concrete

Directory of Open Access Journals (Sweden)

Antonio López-Uceda

2016-02-01

Full Text Available This research aims to produce non-structural concrete with mixed recycled aggregates (MRA in upscaled applications with low-cement content. Four slabs were executed with concrete made with different ratios of coarse MRA (0%, 20%, 40% and 100%, using the mix design, the mixing procedures and the facilities from a nearby concrete production plant. The analysis of the long-term compressive and splitting tensile strengths in concrete cores, extracted from the slabs, allowed the highlighting of the long-term high strength development potential of MRA incorporation. The study of cast specimens produced in situ under the same conditions as the slabs showed, firstly, that the use of MRA has a great influence on the properties related to durability, secondly, that the loss of compressive strength for total MRA incorporation relative to control concrete increases proportionally with the class strength, and, thirdly, that the mechanical properties (including Schmidt hammer results from the concrete slabs showed no significant differences relative to the control concrete for coarse aggregates replacements up to 40%. Therefore, this upscaled experimental study supports the application of concrete with 100% coarse MRA incorporation and low cement content in non-structural civil works such as bike lanes, gutters, ground slabs, leveling surfaces, and subgrades for foundations. To the best of the authors’ knowledge, there have not been any upscaled applications of concrete with MRA and low cement content.

Alkali silica reaction (ASR) in cement free alkali activated sustainable concrete.

Science.gov (United States)

2016-12-19

This report summarizes the findings of an experimental evaluation into alkali silica : reaction (ASR) in cement free alkali-activated slag and fly ash binder concrete. The : susceptibility of alkali-activated fly ash and slag concrete binders to dele...

Natural radioactivity levels and danger ratio in cements, concretes and mortars used in construction

International Nuclear Information System (INIS)

Meneses, J.; Pacheco, C.; Avila, J. M.; Miro, C.

2010-01-01

We have determined the natural radiation level in three types of adhesive cements, five types of concrete and two types of mortars of different strength normally used in the construction field. Of these materials, both concrete and mortars were prepared in our laboratories, cements the contrary were of a commercial nature.

Microwave processing of cement and concrete materials – towards an industrial reality?

International Nuclear Information System (INIS)

Buttress, Adam; Jones, Aled; Kingman, Sam

2015-01-01

Each year a substantial body of literature is published on the use of microwave to process cement and concrete materials. Yet to date, very few if any have lead the realisation of a commercial scale industrial system and is the context under which this review has been undertaken. The state-of the–art is evaluated for opportunities, and the key barriers to the development of new microwave-based processing techniques to enhance production, processing and recycling of cement and concrete materials. Applications reviewed include pyro-processing of cement clinker; accelerated curing, non-destructive testing and evaluation (NDT&E), and end-of-life processing including radionuclide decontamination

Assessment of aggregates- cement paste border in concretes containing silica fume and fly ash

Directory of Open Access Journals (Sweden)

Ali Sademomtazi

2017-12-01

Full Text Available The bond between aggregate and cement paste, called the interfacial transition zone (ITZ is an important parameter that effect on the mechanical properties and durability of concrete. Transition zone microstructure and porosity (pores of cement paste or concrete are affected by the type and properties of materials used which evaluated in this research. On the other hand, the use of efficient, low-cost and reliable method is particularly important for evaluating of concrete performance against the chloride ion penetration and its relationships with transition zone as a suitable index to assess the durability. So far, various methods to approach the electrical Indices are presented. In this research, the effect of pozzolanic materials fly ash (10%, 20% and 30% and silica fume (5% and 10% as substitute of cement by weight in binary and ternary mixtures on the fresh and hardened concrete properties were investigated. To determine mechanical properties, the compressive strength, splitting tensile strength and modulus of elasticity tests were performed. Also, water penetration depth, porosity, water sorptivity, specific electrical resistivity, rapid chloride penetration test (RCPT and rapid chloride migration test (RCMT tests were applied to evaluate concrete durability. To examine the border of aggregate and cement paste morphology of concrete specimens, scanning electron microscope images (SEM was used. The fresh concrete results showed that the presence of silica fume in binary and ternary mixtures reduced workability and air content but fly ash increased them. Adding silica fume to mixtures of containing flay ash while increasing mechanical strength reduced the porosity and pores to 18%. The presence of pozzolanic materials in addition to increasing bond quality and uniformity of aggregate-cement matrix border a considerably positive effect on the transport properties of concrete.

THE EFFECT OF PLASTICIZER ON MECHANICAL PROPERTIES OF THE CEMENT PASTE WITH FINE GROUND RECYCLED CONCRETE

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Jaromír Hrůza

2017-11-01

Full Text Available This article deals with the usage of recycled concrete, which arises from the demolition of concrete structures. The work is focused on the development of mechanical properties (Young's modulus, compressive and flexural strength depending amount of plasticizer in the mixture. In the experiment were prepared three sets of samples with different amounts of plasticizer (0, 0.5 and 1.0 wt. % of cement. Each pair always contained reference samples (only cement and 35 wt. % of fine ground recycled concrete. One of the main reasons for the use of finely ground recycled concrete was a certain substitution of cement in the mixture, which is the most expensive component. Development of Young's modulus was measured by the nondestructive method. The aim of the experiment was to determine the effect of plasticizer on the resulting physical and mechanical properties of cement pastes with fine ground recycled concrete.

Determination of transmission factors of concretes with different water/cement ratio, curing condition, and dosage of cement and air entraining agent

International Nuclear Information System (INIS)

Sahin, Remzi; Polat, Recep; Icelli, Orhan; Celik, Cafer

2011-01-01

Highlights: → We determined transmission factors of parameters affecting properties of concrete. → The most important parameter is W/C ratio for attenuation of radiation of concrete. → Taguchi Method provides an appropriate methodology for parameter reduction. - Abstract: This study focuses on determination of transmission factors of main parameters affecting the properties of both normal- and heavy-weight concrete in order to increase knowledge and understanding of radiation attenuation in concrete at a later age. Water/cement (W/C) ratio, curing condition, cement quantity and air entraining agent (AEA) were selected as the main parameters. Eight energy values have been selected within the energy interval of 30.85-383.85 keV to be used in the radiation source. The Taguchi Method was used as the method of optimization. It was determined in the study that the most important parameter affecting the attenuation of the radiation of the concrete is the W/C ratio and the concretes produced with the lowest level of W/C ratio absorb more radiation. However, it was also determined that there was a combined effect between the W/C ratio and the cement dosage.

Influence of Blended Cements with Calcareous Fly Ash on Chloride Ion Migration and Carbonation Resistance of Concrete for Durable Structures.

Science.gov (United States)

Glinicki, Michał A; Jóźwiak-Niedźwiedzka, Daria; Gibas, Karolina; Dąbrowski, Mariusz

2016-01-02

The objective of this paper is to examine the possible use of new blended cements containing calcareous fly ash in structural concrete, potentially adequate for structural elements of nuclear power plants. The investigation included five new cements made with different contents of non-clinker constituents: calcareous fly ash, siliceous fly ash, ground granulated blastfurnace slag, and a reference cement-ordinary Portland cement. The influence of innovative cements on the resistance of concrete to chloride and carbonation exposure was studied. Additionally, an evaluation of the microstructure was performed using optical microscopy on concrete thin sections. Test results revealed a substantial improvement of the resistance to chloride ion penetration into concrete containing blended cements. The resistance was higher for increased clinker replacement levels and increased with curing time. However, concrete made with blended cements exhibited higher depth of carbonation than the Portland cement concrete, except the Portland-fly ash cement with 14.3% of calcareous fly ash. The thin sections analysis confirmed the values of the carbonation depth obtained from the phenolphthalein test. Test results indicate the possible range of application for new cements containing calcareous fly ash.

Effect of Metakaolin and Slag blended Cement on Corrosion Behaviour of Concrete

Science.gov (United States)

Borade, Anita N.; Kondraivendhan, B.

2017-06-01

The present paper is aimed to investigate the influence of Metakaolin (MK) and Portland slag Cement (PSC) on corrosion behaviour of concrete. For this purpose, Ordinary Portland Cement (OPC) was replaced by 15% MK by weight and readymade available PSC were used. The standard concrete specimens were prepared for both compressive strength and half- cell potential measurement. For the aforesaid experiments, the specimens were cast with varying water to binder ratios (w/b) such as 0.45, 0.5 and 0.55 and exposed to 0%, 3%, 5% and 7.5% of sodium chloride (NaCl) solution. The specimens were tested at wide range of curing ages namely 7, 28, 56, 90 and 180 days. The effects of MK, w/b ratio, age, and NaCl exposure upon concrete were demonstrated in this investigation along with the comparison of results of both MK and PSC concrete were done. It was also observed that concrete with MK shows improved performance as compared to concrete with PSC.

Influence of Blended Cements with Calcareous Fly Ash on Chloride Ion Migration and Carbonation Resistance of Concrete for Durable Structures

Directory of Open Access Journals (Sweden)

Michał A. Glinicki

2016-01-01

Full Text Available The objective of this paper is to examine the possible use of new blended cements containing calcareous fly ash in structural concrete, potentially adequate for structural elements of nuclear power plants. The investigation included five new cements made with different contents of non-clinker constituents: calcareous fly ash, siliceous fly ash, ground granulated blastfurnace slag, and a reference cement—ordinary Portland cement. The influence of innovative cements on the resistance of concrete to chloride and carbonation exposure was studied. Additionally, an evaluation of the microstructure was performed using optical microscopy on concrete thin sections. Test results revealed a substantial improvement of the resistance to chloride ion penetration into concrete containing blended cements. The resistance was higher for increased clinker replacement levels and increased with curing time. However, concrete made with blended cements exhibited higher depth of carbonation than the Portland cement concrete, except the Portland-fly ash cement with 14.3% of calcareous fly ash. The thin sections analysis confirmed the values of the carbonation depth obtained from the phenolphthalein test. Test results indicate the possible range of application for new cements containing calcareous fly ash.

Identification of the sources of organic compounds that decalcify cement concrete and generate alcohols and ammonia gases

Energy Technology Data Exchange (ETDEWEB)

Tomoto, Takashi [Technical Research Institute, Obayashi Road Corporation, 4-640 Shimokiyoto, Kiyose, Tokyo, 204-0011 (Japan); Moriyoshi, Akihiro [Material Science Laboratory, Hokkaido University, 2-1-9-10 Kiyota, Kiyota-ku, Sapporo, 004-0842 (Japan); Sakai, Kiyoshi [Department of Environmental Health, Nagoya City Public Health Research Institute, 1-11 Hagiyama-cho, Mizuho-ku, Nagoya, 467-8615 (Japan); Shibata, Eiji [Department of Health and Psychosocial Medicine, Aichi Medical University School of Medicine, Nagakute-cho, Aichi, 480-1195 (Japan); Kamijima, Michihiro [Department of Occupational and Environmental Health, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya, 466-8550 (Japan)

2009-09-15

This study identifies the emission sources of various types of airborne organic compounds, which deteriorate cement concrete by penetrating into the concrete together with moisture. The study used high-performance liquid chromatography and gas chromatograph mass spectrometry. The results show that the types of organic compounds contained in decalcified cement concrete were very similar to those found in the total suspended compounds in the air, and that the source of the emissions was particles of exhaust from diesel vehicles and radial tires used in summer. Such organic compounds include substances suspected of having endocrine disrupting properties. Hydrolysis occurs when these substances penetrate into highly alkaline cement concrete, and leads to deterioration of the cement concrete and the release of alcohols and ammonia gases which pollute indoor air and may be a cause of the sick building syndrome. (author)

PROPERTIES AND MICROSTRUCTURE OF CEMENT PASTE INCLUDING RECYCLED CONCRETE POWDER

Directory of Open Access Journals (Sweden)

Jaroslav Topič

2017-02-01

Full Text Available The disposal and further recycling of concrete is being investigated worldwide, because the issue of complete recycling has not yet been fully resolved. A fundamental difficulty faced by researchers is the reuse of the recycled concrete fines which are very small (< 1 mm. Currently, full recycling of such waste fine fractions is highly energy intensive and resulting in production of CO2. Because of this, the only recycling methods that can be considered as sustainable and environmentally friendly are those which involve recycled concrete powder (RCP in its raw form. This article investigates the performance of RCP with the grain size < 0.25 mm as a potential binder replacement, and also as a microfiller in cement-based composites. Here, the RCP properties are assessed, including how mechanical properties and the microstructure are influenced by increasing the amount of the RCP in a cement paste (≤ 25 wt%.

Water dynamics in hardened ordinary Portland cement paste or concrete: from quasielastic neutron scattering.

Science.gov (United States)

Bordallo, Heloisa N; Aldridge, Laurence P; Desmedt, Arnaud

2006-09-14

Portland cement reacts with water to form an amorphous paste through a chemical reaction called hydration. In concrete the formation of pastes causes the mix to harden and gain strength to form a rock-like mass. Within this process lies the key to a remarkable peculiarity of concrete: it is plastic and soft when newly mixed, strong and durable when hardened. These qualities explain why one material, concrete, can build skyscrapers, bridges, sidewalks and superhighways, houses, and dams. The character of the concrete is determined by the quality of the paste. Creep and shrinkage of concrete specimens occur during the loss and gain of water from cement paste. To better understand the role of water in mature concrete, a series of quasielastic neutron scattering (QENS) experiments were carried out on cement pastes with water/cement ratio varying between 0.32 and 0.6. The samples were cured for about 28 days in sealed containers so that the initial water content would not change. These experiments were carried out with an actual sample of Portland cement rather than with the components of cement studied by other workers. The QENS spectra differentiated between three different water interactions: water that was chemically bound into the cement paste, the physically bound or "glassy water" that interacted with the surface of the gel pores in the paste, and unbound water molecules that are confined within the larger capillary pores of cement paste. The dynamics of the "glassy" and "unboud" water in an extended time scale, from a hundred picoseconds to a few nanoseconds, could be clearly differentiated from the data. While the observed motions on the picosecond time scale are mainly stochastic reorientations of the water molecules, the dynamics observed on the nanosecond range can be attributed to long-range diffusion. Diffusive motion was characterized by diffusion constants in the range of (0.6-2) 10(-9) m(2)/s, with significant reduction compared to the rate of diffusion

Concrete decontamination by electro-hydraulic scabbling

Energy Technology Data Exchange (ETDEWEB)

Goldfarb, V.; Gannon, R. [Textron Defense System, Everett, MA (United States)

1995-10-01

Textron Defense Systems (TDS) is developing an electro-hydraulic device that has the potential for faster, safer, and less expensive scabbling of contaminated concrete surfaces. In the device, shock waves and cavitating bubbles are produced in water by the electric pulses, and the direct and reflected shock waves impinging on the concrete surface result in the crushing and cracking of the concrete. Pulse energy, frequency, and traverse speed control the depth of the scabbling action. Performance thus far has demonstrated the capability of a prototype unit to process a swath 24 inches wide, up to 3/4 inch deep at a linear velocity of up to 6 feet per hour, i.e., at a scabbling rate of 12 sq. ft. per hour.

Concrete decontamination by electro-hydraulic scabbling

International Nuclear Information System (INIS)

Goldfarb, V.; Gannon, R.

1995-01-01

Textron Defense Systems (TDS) is developing an electro-hydraulic device that has the potential for faster, safer, and less expensive scabbling of contaminated concrete surfaces. In the device, shock waves and cavitating bubbles are produced in water by the electric pulses, and the direct and reflected shock waves impinging on the concrete surface result in the crushing and cracking of the concrete. Pulse energy, frequency, and traverse speed control the depth of the scabbling action. Performance thus far has demonstrated the capability of a prototype unit to process a swath 24 inches wide, up to 3/4 inches deep at a linear velocity of up to 6 feet per hour, i.e., at a scabbling rate of 12 sq. ft. per hour

Carbonation around near aggregate regions of old hardened concrete cement paste

International Nuclear Information System (INIS)

Tam, Vivian W.Y.; Gao, X.F.; Tam, C.M.

2005-01-01

Analogous with most modern cities, waste disposal is a pressing issue due to limited landfill and public filling (land reclamation) areas in Hong Kong in which construction and demolition (C and D) waste forms the major source. Concrete, apportioning the largest portion of C and D waste, has the greatest potential for recycling. However, the knowledge on micro-structural behavior of concrete waste is immature to give adequate details on the macro-behavior of concrete waste. This paper attempts to examine the problems of recycling old concrete by investigating the microstructure and phase transformation of the concrete samples collected from buildings with 46 and 37 years of services. From the results of Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM) examination, it is found that there are a lot of pores at the near layers of aggregate where carbonation of the hardened cement paste (HCP) is high. The pores may be generated as a result of poor workmanship such as insufficient concrete mixing time, trapping of air voids beneath coarse aggregate, inappropriate water to cement ratio, and the microclimate conditions such as humidity that affects the demand on water from the aggregate during mixing

Cement Type Influence on Alkali-Silica Reaction in Concrete with Crushed Gravel Aggregate

Science.gov (United States)

Rutkauskas, A.; Nagrockienė, D.; Skripkiūnas, G.

2017-10-01

Alkali-silica reaction is one of the chemical reactions which have a significant influence for durability of concrete. During alkali and silica reaction, silicon located in aggregates of the concrete, reacts with high alkali content. This way in the micropores of concrete is forming hygroscopic gel, which at wet environment, expanding and slowly but strongly destroying concrete structures. The goal of this paper- to determine the influence of cement type on alkali-silica reaction of mortars with crushed gravel. In the study crushed gravel with fraction 4/16 mm was used and four types of cements tested: CEM I 42.5 R; CEM I 42.5 SR; CEM II/A-S 42.5; CEM II/A-V 52.5. This study showed that crushed gravel is low contaminated on reactive particles containing of amorphous silica dioxide. The expansion after 14 days exceed 0.054 %, by RILEM AAR-2 research methodology (testing specimen dimension 40×40×160 mm). Continuing the investigation to 56 days for all specimens occurred alkaline corrosion features: microcracking and the surface plaque of gel. The results showed that the best resistance to alkaline corrosion after 14 days was obtained with cement CEM I 42.5 SR containing ash additive, and after 56 days with cement CEM II/A-V 52.5 containing low alkali content. The highest expansion after 14 and 56 days was obtained with cement CEM I 42.5 R without active mineral additives.

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

Directory of Open Access Journals (Sweden)

FAREED AHMED MEMON

2010-10-01

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

Cementing Efficiency of Low Calcium Fly Ash in Fly Ash Concretes

OpenAIRE

T. D. Gunneswara Rao; Mudimby Andal

2014-01-01

Research on the utilization of fly ash will no longer refer the fly ash as a waste material of thermal power plants. Use of fly ash in concrete making, makes the concrete economical as well as durable. The fly ash is being added to the concrete in three ways namely, as partial replacement to cement, as partial replacement to fine aggregates and as admixture. Addition of fly ash to the concrete in any one of the form mentioned above, makes the concrete more workable and durable than the conven...

Yemen watched from cement plant construction work. Cement plant koji wo toshite mita Yemen

Energy Technology Data Exchange (ETDEWEB)

Furuta, M [Kajima Corp., Tokyo (Japan)

1993-06-25

Construction of a cement plant was planned at southern part of Yemen. This is a cement plant with annual production 500,000 tons. The term of work was from January, 1990 to February, 1993. The present paper describes an outline the construction of this Cement Plant, the nationality and living environment in Yemen, and construction equipment which was used. The construction work consisted of 113,000m[sup 3] of digging, 82,000m[sup 3] of backfilling, 66,100m[sup 3] of concreting, and 29,285m[sup 3] of asphalt pavement. Reinforcing steel weighing 6,400 tons and steel frame weighing 3,600 tons were totally used. Equipment weighing 7,912 tons and electric devices weighing 1,299 tons were totally installed. For this construction work, two crawler cranes, six hydraulic cranes, aggregate plant, concrete mixers, and construction equipment, such as bulldozers, shovels, and dumpers, were brought from Japan. 5 figs.

Development of Mix Design Method in Efforts to Increase Concrete Performance Using Portland Pozzolana Cement (PPC)

Science.gov (United States)

Krisnamurti; Soehardjono, A.; Zacoeb, A.; Wibowo, A.

2018-01-01

Earthquake disaster can cause infrastructure damage. Prevention of human casualties from disasters should do. Prevention efforts can do through improving the mechanical performance of building materials. To achieve high-performance concrete (HPC), usually used Ordinary Portland Cement (OPC). However, the most widely circulating cement types today are Portland Pozzolana Cement (PPC) or Portland Composite Cement (PCC). Therefore, the proportion of materials used in the HPC mix design needs to adjust to achieve the expected performance. This study aims to develop a concrete mix design method using PPC to fulfil the criteria of HPC. The study refers to the code/regulation of concrete mixtures that use OPC based on the results of laboratory testing. This research uses PPC material, gravel from Malang area, Lumajang sand, water, silica fume and superplasticizer of a polycarboxylate copolymer. The analyzed information includes the investigation results of aggregate properties, concrete mixed composition, water-binder ratio variation, specimen dimension, compressive strength and elasticity modulus of the specimen. The test results show that the concrete compressive strength achieves value between 25 MPa to 55 MPa. The mix design method that has developed can simplify the process of concrete mix design using PPC to achieve the certain desired performance of concrete.

Surface treatment of reinforced cement concrete mixtures of hpcm type

OpenAIRE

Vyrozhemsky, V.; Krayushkina, K.

2006-01-01

One of the most perspective ways of pavement roughness and durability improvement is the arrangement of thin cement concrete layer surface treatment reinforced with different types of fiber. The name of this material is known abroad as HPCM (High Performance Cementious Materials) durable thin layer concrete pavement in a thickness of 1 cm, dispersion-like reinforced with metal or polymer fibers. To enhance bind properties the stone material grade 3 7mm is applied on the top of concrete surfac...

Study on cold weather concreting using low-heat cement

International Nuclear Information System (INIS)

Hama, Yukio; Ryu Koto; Tomosawa, Fuminori

2004-01-01

In this paper, properties of frost damage at early age and strength development and thermal crack were studied, for purposes of application to the mass concrete of low-heat cement in cold weather, by means of concrete experiments and temperature analysis by finite element method. The experiments and the analysis result showed that the strength for resistance to frost damage at early age was 5N/mm 2 , the concrete strength correction value in terms of curing temperature was calculated approximately, and was effective in the resistance of thermal crack. And then, the application ranges of construction procedures were investigated. (author)

Durability of saw-cut joints in plain cement concrete pavements : [technical summary].

Science.gov (United States)

2011-01-01

The main objective of this study was to evaluate factors influencing the durability of the joints in portland cement concrete pavement in the state of Indiana. : The scope of the research included the evaluation of the absorption of water in concrete...

Aspects of clay/concrete interactions

International Nuclear Information System (INIS)

Oscarson, D.W.; Dixon, D.A.; Onofrei, M.

1997-01-01

In the Canadian concept for nuclear fuel waste management, both clay-based materials and concrete are proposed for use as barriers, seals or supporting structures. The main concern when clays and concrete are in proximity is the generation of a high-pH environment by concrete since clay minerals are relatively unstable at high pH. Here we examine the OH - -generating capacity of two high-performance concretes when in contact with several solutions. We also investigate various aspects of claylconcrete interactions. They are: (1) the alkalimetric titration of clay suspensions, (2) the effect of Ca(OH) 2 (portlandite) on the swelling and hydraulic properties of compacted bentonite, and (3) the influence of cement grout on a backfill clay retrieved from the 900-d Buffer/Container Experiment at the Underground Research Laboratory of AECL. The results indicate that although high-performance concretes establish significantly lower poresolution pH (9 to 10) than does ordinary portland cement, the pH is still somewhat higher than that of clay/groundwater systems of about pH 8. Hence, even if high-performance concrete is used in a disposal vault, the potential still exists for clay minerals to alter over long periods of time if in contact with this concrete. The data show, however, that clays have a substantial buffering capacity, and clay-based barriers can thus neutralize much of the OH - potentially released from concrete in a vault. Moreover, even after reacting for 120 d at 85 o C with up to 5 wt.% Ca(OH) 2 , compacted bentonite (dry density = 1.2 Mg/m 3 ) retains much of its swelling capacity and has a permeability low enough (hydraulic conductivity ≤ 10 -11 m/s) to ensure that molecular diffusion will be the main transport mechanism through compacted clay-based barriers. Furthermore, according to X-ray diffractometry, the clay mineral component of backfill was not altered by contact with a cement grout for 900 d in the Buffer/Container Experiment

Corrosion Resistance of Calcium Aluminate Cement Concrete Exposed to a Chloride Environment.

Science.gov (United States)

Ann, Ki Yong; Cho, Chang-Geun

2014-01-28

The present study concerns a development of calcium aluminate cement (CAC) concrete to enhance the durability against an externally chemically aggressive environment, in particular, chloride-induced corrosion. To evaluate the inhibition effect and concrete properties, CAC was partially mixed with ordinary Portland cement (OPC), ranging from 5% to 15%, as a binder. As a result, it was found that an increase in the CAC in binder resulted in a dramatic decrease in the setting time of fresh concrete. However, the compressive strength was lower, ranging about 20 MPa, while OPC indicated about 30-35 MPa at an equivalent age. When it comes to chloride transport, there was only marginal variation in the diffusivity of chloride ions. The corrosion resistance of CAC mixture was significantly enhanced: its chloride threshold level for corrosion initiation exceeded 3.0% by weight of binder, whilst OPC and CAC concrete indicated about 0.5%-1.0%.

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

Energy Technology Data Exchange (ETDEWEB)

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

2014-08-15

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

Performance of Periwinkle Shell Ash Blended Cement Concrete Exposed to Magnesium Sulphate

Directory of Open Access Journals (Sweden)

Umoh A.A.

2013-01-01

Full Text Available The study examined the compressive strength of periwinkle shell ash (PSA blended cement concrete in magnesium sulphate medium. Specimens were prepared from designed characteristics strength of 25 MPa. The cement replacement with PSA ranged between 0 and 40% by volume. A total of 180 cube specimens were cast and cured in water. At 28 days curing, 45 specimens each were transferred into magnesium sulphate of 1%, 3%, and 5% solution, while others were continuously cured in water and tested at 62, 92, and 152 days. The results revealed a higher loss in compressive strength with the control mix, and that it increases with increased in MgSO4 concentration and exposure period, whereas, the attack on the PSA blended cement concrete was less and the least value recorded by 10% PSA content. Therefore, the study concluded that the optimum percentage replacement of cement with 10% PSA could mitigate magnesium sulphate attack.

Effect of Slag Content and Hardening Accelerator Dosage on the Physico Mechanical Properties of Cement and Concrete

International Nuclear Information System (INIS)

Derabla, R.; Mokrani, I.; Benmalek, M.L.

2011-01-01

Our contribution consists at the study of the effect of (0 %, 0.2 % and 0.34 %) dosage of an hardening accelerating plasticizer (Plastocrete 160, produced by Sika Aldjazair) on the properties of normal mortar and concretes prepared with portland cement artificial of Hadjar Soud cement factory (Skikda - Algeria) with addition of (10 % and 20 %) of granulated blast furnace slag finely crushed of the El Hadjar blast furnace (Annaba - Algeria). The tests are focused to the physical and mechanical characteristics of elaborated materials to knowing: setting time, porosity, water absorption capacity and the test of compressive strength at 2, 7 and 28 days. The results obtained show clearly the reliability of the additive used to accelerate the hardening and to obtain high strengths at early age, which increase by increasing of the additive dosage. For the slag, its low hydraulic capacity does not make it profitable than at the long term (beyond 28 days). (author)

INFLUENCE OF WATER-TO-CEMENT RATIO ON AIR ENTRAILMENT IN PRODUCTION OF NON-AUTOCLAVED FOAM CONCRETE USING TURBULENCE CAVITATION TECHNOLOGY

Directory of Open Access Journals (Sweden)

Gorshkov Pavel Vladimirovich

2012-10-01

Full Text Available Non-autoclaved foam concrete is an advanced thermal insulation material. Until recently, foam concrete production has been based on separate preparation of foam and solution, followed by their blending in a mixer. The situation changed when high-quality synthetic foaming agents and turbulence cavitation technology appeared on the market. Every model provides a dependence between the foam concrete strength and the water-to-cement ratio. According to the water-cement ratio we can distinguish strong concrete mixtures (with the water-to-cement ratio equal to 0.3…0.4 and ductile ones (with the water-to-cement ratio equal to 0.5…0.7. Strong concrete mixtures are more durable. The lower the water-to-cement ratio, the higher the foam concrete strength. However super-plastic substances cannot be mixed by ordinary turbulent mixers. Foam concrete produced using the turbulence cavitation technology needs air-entraining, its intensity being dependent on several factors. One of the main factors is the amount of free water, if it is insufficient, the mixture will not be porous enough. A researcher needs to identify the optimal water-to-cement ratio based on the water consumption rate. Practical production of prefabricated concrete products and structures has proven that the reduction of the water-to-cement ratio improves the strength of the product. The task is to find the water-to-cement ratio for the foam concrete mixture to be plastic enough for air entraining. An increase in the ratio causes loss in the strength. The ratio shall vary within one hundredth points. Super-plasticizers are an alternative solution.

Microstructure and properties of styrene acrylate polymer cement concrete

NARCIS (Netherlands)

Undetermined, U.

1995-01-01

The paper systematically describes the evolution of the microstructure of a styrene acrylate polymer cement concrete in relation to its mechanical properties and durability. The results presented and discussed at the present paper involve the interaction of the polymer dispersion with portland

Waste Cellulose from Tetra Pak Packages as Reinforcement of Cement Concrete

Directory of Open Access Journals (Sweden)

Gonzalo Martínez-Barrera

2015-01-01

Full Text Available The development of the packaging industry has promoted indiscriminately the use of disposable packing as Tetra Pak, which after a very short useful life turns into garbage, helping to spoil the environment. One of the known processes that can be used for achievement of the compatibility between waste materials and the environment is the gamma radiation, which had proved to be a good tool for modification of physicochemical properties of materials. The aim of this work is to study the effects of waste cellulose from Tetra Pak packing and gamma radiation on the mechanical properties of cement concrete. Concrete specimens were elaborated with waste cellulose at concentrations of 3, 5, and 7 wt% and irradiated at 200, 250, and 300 kGy of gamma dose. The results show highest improvement on the mechanical properties for concrete with 3 wt% of waste cellulose and irradiated at 300 kGy; such improvements were related with the surface morphology of fracture zones of cement concrete observed by SEM microscopy.

Strengthening of Concrete Structures with cement based bonded composites

DEFF Research Database (Denmark)

Täljsten, Björn; Blanksvärd, Thomas

2008-01-01

Polymers). The method is very efficient and has achieved world wide attention. However, there are some drawbacks with the use of epoxy, e.g. working environment, compatibility and permeability. Substituting the epoxy adherent with a cement based bonding agent will render a strengthening system...... with improved working environment and better compatibility to the base concrete structure. This study gives an overview of different cement based systems, all with very promising results for structural upgrading. Studied parameters are structural retrofit for bending, shear and confinement. It is concluded...

Carbon Nanofiber Cement Sensors to Detect Strain and Damage of Concrete Specimens Under Compression.

Science.gov (United States)

Galao, Oscar; Baeza, F Javier; Zornoza, Emilio; Garcés, Pedro

2017-11-24

Cement composites with nano-additions have been vastly studied for their functional applications, such as strain and damage sensing. The capacity of a carbon nanofiber (CNF) cement paste has already been tested. However, this study is focused on the use of CNF cement composites as sensors in regular concrete samples. Different measuring techniques and humidity conditions of CNF samples were tested to optimize the strain and damage sensing of this material. In the strain sensing tests (for compressive stresses up to 10 MPa), the response depends on the maximum stress applied. The material was more sensitive at higher loads. Furthermore, the actual load time history did not influence the electrical response, and similar curves were obtained for different test configurations. On the other hand, damage sensing tests proved the capability of CNF cement composites to measure the strain level of concrete samples, even for loads close to the material's strength. Some problems were detected in the strain transmission between sensor and concrete specimens, which will require specific calibration of each sensor one attached to the structure.

Compressive strength, flexural strength and thermal conductivity of autoclaved concrete block made using bottom ash as cement replacement materials

International Nuclear Information System (INIS)

Wongkeo, Watcharapong; Thongsanitgarn, Pailyn; Pimraksa, Kedsarin; Chaipanich, Arnon

2012-01-01

Highlights: ► Autoclaved aerated concrete were produced using coal bottom ash as a cement replacement material. ► Coal bottom ash was found to enhance concrete strengths. ► Thermal conductivity of concrete was not significantly affected. ► X-ray diffraction and thermal analysis show tobermorite formation. -- Abstract: The bottom ash (BA) from Mae Moh power plant, Lampang, Thailand was used as Portland cement replacement to produce lightweight concrete (LWC) by autoclave aerated concrete method. Portland cement type 1, river sand, bottom ash, aluminium powder and calcium hydroxide (Ca(OH) 2 ) were used in this study. BA was used to replace Portland cement at 0%, 10%, 20% and 30% by weight and aluminium powder was added at 0.2% by weight in order to produce the aerated concrete. Compressive strength, flexural and thermal conductivity tests were then carried out after the concrete were autoclaved for 6 h and left in air for 7 days. The results show that the compressive strength, flexural strength and thermal conductivity increased with increased BA content due to tobermorite formation. However, approximately, 20% increase in both compressive (up to 11.61 MPa) and flexural strengths (up to 3.16 MPa) was found for mixes with 30% BA content in comparison to just around 6% increase in the thermal conductivity. Thermogravimetry analysis shows C–S–H formation and X-ray diffraction confirm tobermorite formation in bottom ash lightweight concrete. The use of BA as a cement replacement, therefore, can be seen to have the benefit in enhancing strength of the aerated concrete while achieving comparatively low thermal conductivity when compared to the results of the control Portland cement concrete.

Nanotechnology-Based Performance Improvements For Portland Cement Concrete - Phase I

Science.gov (United States)

2012-08-16

A fundamental understanding of the nano-structure of Portland cement concrete (PCC) is the key to realizing significant breakthroughs regarding high performance and susta : (MBTC 2095/3004) using molecular dynamics (MD) provided new understanding of ...

Compressive Strength of Volcanic Ash/Ordinary Portland Cement Laterized Concrete

Directory of Open Access Journals (Sweden)

Olusola K. O.

2010-01-01

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.

HYDRO-ABRASIVE RESISTANCE AND MECHANICAL PROPERTIES OF CONCRETE WITH ADDED FLY ASH

OpenAIRE

Ristić, Nenad; Grdić, Zoran; Topličić-Ćurčić, Gordana

2015-01-01

The durability of hydraulic engineering structures mostly depends on the resistance of their concrete surfaces to mechanical abrasion. In this paper, we study the hydro-abrasive resistance and mechanical properties of concrete in which cement is partially replaced with fly ash in various proportions. To evaluate these concretes, we measured their compressive strength, flexural strength, static modulus of elasticity, ultrasound velocity through concrete, and sclerometer rebound. The hydro-abra...

Effect of Ground Waste Concrete Powder on Cement Properties

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Xianwei Ma

2013-01-01

Full Text Available The paste/mortar attached to the recycled aggregate decreases the quality of the aggregate and needs to be stripped. The stripped paste/mortar is roughly 20% to 50% in waste concrete, but relevant research is very limited. In this paper, the effects of ground waste concrete (GWC powder, coming from the attached paste/mortar, on water demand for normal consistency, setting time, fluidity, and compressive strength of cement were analyzed. The results show that the 20% of GWC powder (by the mass of binder has little effect on the above properties and can prepare C20 concrete; when the sand made by waste red clay brick (WRB replaces 20% of river sand, the strength of the concrete is increased by 17% compared with that without WRB sand.

The influence of calcium nitrate on setting and hardening rate of Portland cement concrete at different temperatures

Science.gov (United States)

Kičaitė, A.; Pundienė, I.; Skripkiūnas, G.

2017-10-01

Calcium nitrate in mortars and concrete is used as a multifunctional additive: as set accelerator, plasticizer, long term strength enhancer and as antifreeze admixture. Used binding material and the amount of calcium nitrate, affect the characteristics of the concrete mixture and strength of hardened concrete. The setting time of the initial and the final binding at different temperatures of hardening (+ 20 °C and + 5 °C) of the pastes made of different cements (Portland cement CEM I 42.5 R and Portland limestone cement CEM II/A-LL 42.5 R) and various amounts of calcium nitrate from 1 % until 3 % were investigated. The effect of calcium nitrate on technological characteristics of concrete mixture (the consistency of the mixture, the density, and the amount of air in the mixture), on early concrete strength after 2 and 7 days, as well as on standard concrete strength after 28 days at different temperatures (at + 20 °C and + 5 °C) were analysed.

Cement manufacture and the environment - Part I: Chemistry and technology

Science.gov (United States)

Van Oss, H. G.; Padovani, A.C.

2002-01-01

Hydraulic (chiefly portland) cement is the binding agent in concrete and mortar and thus a key component of a country's construction sector. Concrete is arguably the most abundant of all manufactured solid materials. Portland cement is made primarily from finely ground clinker, which itself is composed dominantly of hydraulically active calcium silicate minerals formed through high-temperature burning of limestone and other materials in a kiln. This process requires approximately 1.7 tons of raw materials perton of clinker produced and yields about 1 ton of carbon dioxide (CO2) emissions, of which calcination of limestone and the combustion of fuels each contribute about half. The overall level of CO2 output makes the cement industry one of the top two manufacturing industry sources of greenhouse gases; however, in many countries, the cement industry's contribution is a small fraction of that from fossil fuel combustion by power plants and motor vehicles. The nature of clinker and the enormous heat requirements of its manufacture allow the cement industry to consume a wide variety of waste raw materials and fuels, thus providing the opportunity to apply key concepts of industrial ecology, most notably the closing of loops through the use of by-products of other industries (industrial symbiosis). In this article, the chemistry and technology of cement manufacture are summarized. In a forthcoming companion article (part II), some of the environmental challenges and opportunities facing the cement industry are described. Because of the size and scope of the U.S. cement industry, the analysis relies primarily on data and practices from the United States.

Recycling of Reclaimed Asphalt Pavement in Portland Cement Concrete

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Salim Al-Oraimi

2009-06-01

Full Text Available Reclaimed Asphalt Pavement (RAP is the result of removing old asphalt pavement material. RAP consists of high quality well-graded aggregate coated with asphalt cement. The removal of asphalt concrete is done for reconstruction purposes, resurfacing, or to obtain access to buried utilities. The disposal of RAP represents a large loss of valuable source of high quality aggregate. This research investigates the properties of concrete utilizing recycled reclaimed asphalt pavement (RAP. Two control mixes with normal aggregate were designed with water cement ratios of 0.45 and 0.5. The control mixes resulted in compressive strengths of 50 and 33 MPa after 28 days of curing. The coarse fraction of RAP was used to replace the coarse aggregate with 25, 50, 75, and 100% for both mixtures. In addition to the control mix (0%, the mixes containing RAP were evaluated for slump, compressive strength, flexural strength, and modulus of elasticity. Durability was evaluated using surface absorption test.

Durability of saw-cut joints in plain cement concrete pavements.

Science.gov (United States)

2011-01-01

The objective of this project was to evaluate factors influencing the durability of the joints in portland cement concrete : pavement in the state of Indiana. Specifically this work evaluated the absorption of water, the absorption of deicing solutio...

Laboratory investigation of the performances of cement and fly ash modified asphalt concrete mixtures

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Suched Likitlersuang

2016-09-01

Full Text Available The influence of filler materials on volumetric and mechanical performances of asphalt concrete was investigated in this study. The AC60/70 asphalt binder incorporating with cement and fly ash as filler materials was mixed with limestone following the Marshall mix design method. The filler contents of cement and/or fly ash were varied. The non-filler asphalt concrete mixtures of the AC60/70 and the polymer modified asphalt were prepared for the purpose of comparison. The investigation programme includes the indirect tensile test, the resilient modulus test and the dynamic creep test. The tests are conducted under the humid temperate environments. All tests were then carried out under standard temperature (25 °C and high temperature (55 °C by using a controlled temperature chamber via the universal testing machine. The wet-conditioned samples were prepared to investigate the moisture susceptibility. Results show that cement and/or fly ash were beneficial in terms of improved strength, stiffness and stripping resistance of asphalt mixture. In addition, the combined use of cement and fly ash can enhance rutting resistance at wet and high temperature conditions. The results indicate that the strength, stiffness and moisture susceptibility performances of the asphalt concrete mixtures improved by filler are comparable to the performance of the polymer modified asphalt mixture. Keywords: Asphalt concrete, Filler, Resilient modulus, Dynamic creep test, Moisture susceptibility

Assessment of the influence of fly ash additive on the tightness of concrete with furnace cement CEM IIIA 32,5N

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Anna Szcześniak

2017-12-01

Full Text Available The analysis of influence of fly ash additive to concrete on the basis of cement CEM IIIA 32,5 N on the tightness and strength was presented in the paper. Researches were carried out for three types of concrete made with the use of CEM IIIA 32,5N LH HSR NA cement. The basic recipe of concrete does not contain the additive of fly ash, while two other concretes contain the fly ash additive in an amount of 25% and 33% of the cement mass. Laboratory investigations of the concrete samples were carried out under conditions of long-term maturation in the range of the water tightness and the depth of water penetration in concrete, compressive strength and tensile strength of concrete at splitting. Keywords: concrete testing, furnace cement, fly ash additive, water tightness of concrete, strength of concrete

A Review for Characterization of Silica Fume and Its Effects on Concrete Properties

OpenAIRE

Mohammad Panjehpour; Abang Abdullah Abang Ali; Ramazan Demirboga

2011-01-01

Mineral additions which are also known as mineral admixtures have been used in Portland cement for many years. There are two types of additions which are commonly mixed into the Portland clinker or blended directly with cement these days. They are crystalline, also known as hydraulically inactive additions and pozzolanic, which are hydraulically active additions. Silica fume is very reactive pozzolan, while it is used in concrete because of its fine particles, large surface area and high SiO2...

Influence of packing and dispersion of particles on the cement content of concretes

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B. L. DAMINELI

Full Text Available Abstract Due to environmental issues, the concrete chain seeks to reduce CO2 emissions. However, growing demand from developing countries causes the increase of CO2 emissions in production to exceed decreases generated by industrial actions, such as improving kilns and clinker replacement. New strategies are important. Changes in the concrete formulation, making it more efficient, can help if these changes produce concrete with the same performance and lower cement consumption. In this regard, the improvement of packing and dispersion of particles increases this efficiency. The better the packing, the lower the volume of voids between particles, thereby requiring lower fluid content (water to permit flow. The dispersion of the particles also decreases the water content for the same fluidity. The less the water content, the smaller the water/cement (w/c ratio, and the greater the resistance. Thus, both strategies increase the efficiency by uncoupling obtaining fluidity from the water content. This study investigated the influence of packing and dispersion on the efficiency of cement use in concrete. The increase of packing and the complete dispersion of fine particles has been shown to improve efficiency, as measured by the ratio between binder consumption and compressive strength (the performance parameter used in most practical applications.

Normal and refractory concretes for LMFBR applications. Volume 1. Review of literature on high-temperature behavior of portland cement and refractory concretes. Final report

International Nuclear Information System (INIS)

Bazant, Z.P.; Chern, J.C.; Abrams, M.S.; Gillen, M.P.

1982-06-01

The extensive literature on the properties and behavior at elevated temperature of portland cement concrete and various refractory concretes was reviewed to collect in concise form the physical and chemical properties of castable refractory concretes and of conventional portland cement concretes at elevated temperature. This survey, together with an extensive bibliography of source documents, is presented in Volume 1. A comparison was made of these properties, the relative advantages of the various concretes was evaluated for possible liquid metal fast breeder reactor applications, and a selection was made of several materials of interest for such applications. Volume 2 concludes with a summary of additional knowledge needed to support such uses of these materials together with recommendations on research to provide that knowledge

Effect of Partial Replacement of Cement by Mixture of Glass Powder and Silica Fume Upon Concrete Strength

OpenAIRE

Khan , Abdul Ghayoor; Khan , Bazid

2017-01-01

International audience; All over the world the most common consuming construction material is concrete. It is well know that concrete is the combination of cement, aggregates and water. The production of cement results in the formation of carbon dioxide gas causes the environmental pollution. About 7 percent of carbon dioxide gas is evolved from cement industries to atmosphere. Keeping in view about the environmental pollution which may leads to some serious issues of health, so it is essenti...

Evaluation of Strength Characteristics of Laterized Concrete with Corn Cob Ash (CCA) Blended Cement

Science.gov (United States)

Ikponmwosa, E. E.; Salau, M. A.; Kaigama, W. B.

2015-11-01

Agricultural wastes are dumped in landfills or left on land in which they constitute nuisance. This study presents the results of investigation of strength characteristics of reinforced laterized concrete beams with cement partially replaced with corn cob (agricultural wastes) ash (CCA). Laterized concrete specimen of 25% laterite and 75% sharp sand were made by blending cement with corn cob ash at 0 to 40% in steps of 10%. A concrete mix ratio of 1:2:4 was used to cast 54 cubes of 150×150×150mm size and 54 beams of dimension 750×150×150mm. The results show that the consistency and setting time of cement increased as the percentage replacement of cement with CCA increased while the workability and density of concrete decreased as the percentage of CCA increased. There was a decrease in compressive strength when laterite was introduced to the concrete from 25.04 to 22.96N/mm2 after 28 days and a continual reduction in strength when CCA was further added from 10% to 40% at steps of 10%. Generally, the beam specimens exhibited majorly shear failure with visible diagonal cracks extending from support points to the load points. The corresponding central deflection in beams, due to two points loading, increased as the laterite was added to the concrete mix but reduced and almost approaching that of the control as 10% CCA was added. The deflection then increased as the CCA content further increased to 20%, 30% and 40% in the mix. It was also noted that the deflection of all percentage replacement including 40% CCA is less than the standard recommended maximum deflection of the beam. The optimal flexural strength occurred with 10% CCA content.

Investigation on the Rheological Behavior of Fly Ash Cement Composites at Paste and Concrete Level

Science.gov (United States)

Thiyagarajan, Hemalatha; Mapa, Maitri; Kushwaha, Rakhi

2018-06-01

Towards developing sustainable concrete, nowadays, high volume replacement of cement with fly ash (FA) is more common. Though the replacement of fly ash at 20-30% is widely accepted due to its advantages at both fresh and hardened states, applicability and acceptability of high volume fly ash (HVFA) is not so popular due to some adverse effects on concrete properties. Nowadays to suit various applications, flowing concretes such as self compacting concrete is often used. In such cases, implications of usage of HVFA on fresh properties are required to be investigated. Further, when FA replacement is beyond 40% in cement, it results in the reduction of strength and in order to overcome this drawback, additions such as nano calcium carbonate (CC), lime sludge (LS), carbon nano tubes (CNT) etc. are often incorporated to HVFA concrete. Hence, in this study, firstly, the influence of replacement level of 20-80% FA on rheological property is studied for both cement and concrete. Secondly, the influence of additions such as LS, CC and CNT on rheological parameters are discussed. It is found that the increased FA content improved the flowability in paste as well as in concrete. In paste, the physical properties such as size and shape of fly ash is the reason for increased flowability whereas in concrete, the paste volume contributes dominantly for the flowability rather than the effect due to individual FA particle. Reduced density of FA increases the paste volume in FA concrete thus reducing the interparticle friction by completely coating the coarse aggregate.

Modified composite material developed on the basis of no-fines asphalt concrete

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Mikhasek Andrey

2017-01-01

Full Text Available Being a composite material, asphalt concrete is widely used in hydraulic engineering and road construction. The paper proves one of asphalt concrete modification, which includes first creating a skeleton of no-fines concrete and then its washing-down with bituminous materials by a hot procedure, can be successfully used in hydraulic structures Modified composite material based on no-fines asphalt concrete has a harder skeleton because of links from cement stone and has a technological advantage, as through the proposed technology it allows to reduce the cost of filling porous spaces. This technology allows to conclude that concrete aggregate with size fractions of 120 mm or less and frost resistance of 50 cycles and less can be recommended for fastening of slopes.

Cement treated recycled crushed concrete and masonry aggregates for pavements

NARCIS (Netherlands)

Xuan, D.X.

2012-01-01

This research is focusing on the characterization of the mechanical and deformation properties of cement treated mixtures made of recycled concrete and masonry aggregates (CTMiGr) in relation to their mixture variables. An extensive laboratory investigation was carried out, in which the mechanical

Aggregate-cement paste transition zone properties affecting the salt-frost damage of high-performance concretes

International Nuclear Information System (INIS)

Cwirzen, Andrzej; Penttala, Vesa

2005-01-01

The influence of the cement paste-aggregate interfacial transition zone (ITZ) on the frost durability of high-performance silica fume concrete (HPSFC) has been studied. Investigation was carried out on eight non-air-entrained concretes having water-to-binder (W/B) ratios of 0.3, 0.35 and 0.42 and different additions of condensed silica fume. Studies on the microstructure and composition of the cement paste have been made by means of environmental scanning electron microscope (ESEM)-BSE, ESEM-EDX and mercury intrusion porosimetry (MIP) analysis. The results showed that the transition zone initiates and accelerates damaging mechanisms by enhancing movement of the pore solution within the concrete during freezing and thawing cycles. Cracks filled with ettringite were primarily formed in the ITZ. The test concretes having good frost-deicing salt durability featured a narrow transition zone and a decreased Ca/Si atomic ratio in the transition zone compared to the bulk cement paste. Moderate additions of silica fume seemed to densify the microstructure of the ITZ

Properties of fresh and hardened sustainable concrete due to the use of palm oil fuel ash as cement replacement

Science.gov (United States)

Hamada, Hussein M.; Jokhio, Gul Ahmed; Mat Yahaya, Fadzil; Humada, Ali M.

2018-04-01

Palm oil fuel ash (POFA) is a by-product resulting from the combustion of palm oil waste such as palm oil shell and empty fruit bunches to generate electricity in the palm oil mills. Considerable quantities of POFA thus generated, accumulate in the open fields and landfills, which causes atmospheric pollution in the form of generating toxic gases. Firstly, to protect the environment; and secondly, having excellent properties for this purpose; POFA can be and has been used as partial cement replacement in concrete preparation. Therefore, this paper compiles the results obtained from previous studies that address the properties of concrete containing POFA as cement replacement in fresh and hardened states. The results indicate that there is a great potential to using POFA as cement replacement because of its ability to improve compressive strength, reduce hydration heat of cement mortar and positively affect other fresh and hardened concrete properties. The paper recommends that conducting further studies to exploit high volume of POFA along with other additives as cement replacement while maintaining high quality of concrete can help minimize CO2 emissions due to concrete.

HYDRATION PROCESS AND MECHANICAL PROPERTIES OF CEMENT PASTE WITH RECYCLED CONCRETE POWDER AND SILICA SAND POWDER

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Jaroslav Topič

2017-11-01

Full Text Available Recycled concrete powder (RCP mostly consisting of cement paste could be reused as partial cement replacement. The aim of this paper is to compare hydration and mechanical properties of RCP and two types of silica sand powder (SSP. Comparison of those materials combined with cement can highlight the binder properties of recycled concrete powder. Using of two types of SSP also show an influence of their fines on hydration process and mechanical properties. Particle size analysis and calorimetric measurement were carried out and mechanical properties such as bulk density, dynamic Young’s modulus and compression strength were examine. Calorimetric measurement proves the presence of exposed non-hydrated particles in RCP that can react again. However lower density of old cement paste in RCP overweight the mentioned potential of RCP and mechanical properties are decreasing compared with reference cement paste and cement paste SSP.

Achievement of 900kgf/cm[sup 2] super workable high strength concrete with belite Portland cement (elevator building of cement silo in Chichibu cement). 2. ; Application to the actual structure. Ko belite kei cement de 900kgf/cm[sup 2] wo tassei (Chichibu cement cement silo no elevator to). 2. ; Jitsukozobutsu eno tekiyo

Energy Technology Data Exchange (ETDEWEB)

Yoda, K.; Sakuramoto, F. (Kajima Corp., Tokyo (Japan))

1993-08-01

For the purpose of rationalization of concrete works, the super workable high strength concrete was applied to the underground part of elevator building of cement silo in the Kumagaya Works, Chichibu Cement, and was successfully put into practice. Quality control values of the super workable high strength concrete were 65[plus minus]5cm in the slump flow and 900kgf/cm[sup 2] in the compressive strength at the age of 28 days. Addition of the admixture was 1.25% of the unit cement amount. Based on the linear correlation between the slump flow and mixer load immediately before discharge, the slump flow was controlled by the mixer load. Property of the fresh concrete, fluidity, compacting property, material segregation resistance property, and strength property were examined by using a sidewall test model. For all tests, satisfactory properties were obtained. Subsequently, the actual structure was successfully constructed. As a result, laborsaving and improvement of productivity were confirmed for the super workable high strength concrete work. 3 refs., 8 figs., 4 tabs.

Microencapsulated phase change materials for enhancing the thermal performance of Portland cement concrete and geopolymer concrete for passive building applications

International Nuclear Information System (INIS)

Cao, Vinh Duy; Pilehvar, Shima; Salas-Bringas, Carlos; Szczotok, Anna M.; Rodriguez, Juan F.; Carmona, Manuel; Al-Manasir, Nodar; Kjøniksen, Anna-Lena

2017-01-01

Highlights: • Microencapsulated phase change materials give high energy storage capacity concrete. • Microcapsule addition increases the porosity of concrete. • Thermal and mechanical properties are linked to the enhanced concrete porosity. • Agglomerated microcapsules have strong impact on the concrete properties. • Microcapsules caused geopolymer to become more energy efficient than Portland cement. - Abstract: Concretes with a high thermal energy storage capacity were fabricated by mixing microencapsulated phase change materials (MPCM) into Portland cement concrete (PCC) and geopolymer concrete (GPC). The effect of MPCM on thermal performance and compressive strength of PCC and GPC were investigated. It was found that the replacement of sand by MPCM resulted in lower thermal conductivity and higher thermal energy storage, while the specific heat capacity of concrete remained practically stable when the phase change material (PCM) was in the liquid or solid phase. Furthermore, the thermal conductivity of GPC as function of MPCM concentration was reduced at a higher rate than that of PCC. The power consumption needed to stabilize a simulated indoor temperature of 23 °C was reduced after the addition of MPCM. GPC exhibited better energy saving properties than PCC at the same conditions. A significant loss in compressive strength was observed due to the addition of MPCM to concrete. However, the compressive strength still satisfies the mechanical European regulation (EN 206-1, compressive strength class C20/25) for concrete applications. Finally, MPCM-concrete provided a good thermal stability after subjecting the samples to 100 thermal cycles at high heating/cooling rates.

Nanotechnological applied tasks of the increase in the efficiency of the hardening processes of cement concrete

Directory of Open Access Journals (Sweden)

Chernishov Evgeny Mihalovich

2017-02-01

Full Text Available The scientific basis of the solution to the applied tasks of concrete technology through the use of «nano» tools, which provide the organization of the heterogeneous process of cement hydration and hardening, has been characterized. It is shown that the introduction of nanoadditives enables the direct regulation of the processes of structure formation in cement systems at the nanolevel. The effectiveness of the use of «nano» tools has been proposed to evaluate by means of complex criteria characterizing quantitatively the change in the activation energy, the rate of the process and time of its completion τ, the size and power consumption of the technology E while ensuring quality levels specified by R. According to the criteria, the monitoring of the results of the research has been made. Moreover, the most effective nanomodifying admixtures of two types have been identified. Type I is a compound nanoadditive based on nanoparticles SiO2 in combination with a superplasticizer, which mechanism of action is associated and also characterized by the increase in specific strength per unit measure the degree of cement hydration by 1.25–1.35 times. Engineering problems have been formulated. Moreover, the solutions are indicated for increasing the energy efficiency of the factory production of reinforced concrete products and structures. These solutions predetermine the reduction in the value of the maximum temperature for the curing of concrete, the reduction of the duration of the achievement of the required degree of cement hydration while concrete hardens, the reduction of time of cement concrete hardening to reach the regulated values of its strength, the increase in concrete strength per unit of cement consumption per m3 and energy efficiency of concrete hardening process in the preparation of reinforced concrete products. with the catalytic role in the processes of phase formation of nanoparticles of hydrated compounds. Type II is a

Hydraulic activity of belite cement from class C coal fly ash. Effect of curing and admixtures

OpenAIRE

Goñi, S., Guerrero, A.

2006-01-01

[EN] The effect of curing method and a water-reducing additive on the hydraulic activity of high lime content (ASTM type C) fly ash belite cement (FABC-2-W) is reported. A class C fly ash was subjected to hydrothermal treatment and subsequent calcination to synthesize FABC. Hydraulic activity was evaluated in the cement paste over 180 days from the physically bound water content as determined by thermogravimetric analysis and the degree of hydration, in turn found with...

Studies of ancient concrete as analogs of cementitious sealing materials for a repository in tuff

Energy Technology Data Exchange (ETDEWEB)

Roy, D.M.; Langton, C.A.

1989-03-01

The durability of ancient cementitious materials has been investigated to provide data applicable to determining the resistance to weathering of concrete materials for sealing a repository for storage of high-level radioactive waste. Because tuff and volcanic ash are used in the concretes in the vicinity of Rome, the results are especially applicable to a waste repository in tuff. Ancient mortars, plasters, and concretes collected from Rome, Ostia, and Cosa dating to the third century BC show remarkable durability. The aggregates used in the mortars, plasters, and concretes included basic volcanic and pyroclastic rocks (including tuff), terra-cotta, carbonates, sands, and volcanic ash. The matrices of ancient cementitious materials have been characterized and classified into four categories: (1) hydraulic hydrated lime and hydrated lime cements, (2) hydraulic aluminous and ferruginous hydrated lime cements ({plus_minus} siliceous components), (3) pozzolana/hydrated lime cements, and (4) gypsum cements. Most of the materials investigated are in category (3). The materials were characterized to elucidate aspects of the technology that produced them and their response to the environmental exposure throughout their centuries of existence. Their remarkable properties are the result of a combination of chemical, mineralogical, and microstructural factors. Their durability was found to be affected by the matrix mineralogy, particle size, and porosity; aggregate type, grading and proportioning; and the methodology of placement. 30 refs.

On Deterioration Mechanism of Concrete Exposed to Freeze-Thaw Cycles

Science.gov (United States)

Trofimov, B. Ya; Kramar, L. Ya; Schuldyakov, K. V.

2017-11-01

At present, concrete and reinforced concrete are gaining ground in all sectors of construction including construction in the extreme north, on shelves, etc. Under harsh service conditions, the durability of reinforced concrete structures is related to concrete frost resistance. Frost resistance tests are accompanied by the accumulation of residual dilation deformations affected by temperature-humidity stresses, ice formation and other factors. Porosity is an integral part of the concrete structure which is formed as a result of cement hydration. The prevailing hypothesis of a deterioration mechanism of concrete exposed to cyclic freezing, i.e. the hypothesis of hydraulic pressure of unfrozen water in microcapillaries, does not take into account a number of phenomena that affect concrete resistance to frost aggression. The main structural element of concrete, i.e. hardened cement paste, contains various hydration products, such as crystalline, semicrystalline and gel-like products, pores and non-hydrated residues of clinker nodules. These structural elements in service can gain thermodynamic stability which leads to the concrete structure coarsening, decrease in the relaxation capacity of concrete when exposed to cycling. Additional destructive factors are leaching of portlandite, the difference in thermal dilation coefficients of hydration products, non-hydrated relicts, aggregates and ice. The main way to increase concrete frost resistance is to reduce the macrocapillary porosity of hardened cement paste and to form stable gel-like hydration products.

High Strength Lightweight Concrete Made with Ternary Mixtures of Cement-Fly Ash-Silica Fume and Scoria as Aggregate

OpenAIRE

YAŞAR, Ergül; ATIŞ, Cengiz Duran; KILIÇ, Alaettin

2014-01-01

This paper presents part of the results of an ongoing laboratory study carried out to design a structural lightweight high strength concrete (SLWHSC) made with and without ternary mixtures of cement-fly ash-silica fume. In the mixtures, lightweight basaltic-pumice (scoria) aggregate was used. A concrete mixture made with lightweight scoria, and another lightweight scoria concrete mixture incorporating 20% fly ash and 10% silica fume as a cement replacement, were prepared. Two normal...

The maximum percentage of fly ash to replace part of original Portland cement (OPC) in producing high strength concrete

Science.gov (United States)

Mallisa, Harun; Turuallo, Gidion

2017-11-01

This research investigates the maximum percent of fly ash to replace part of Orginal Portland Cement (OPC) in producing high strength concrete. Many researchers have found that the incorporation of industrial by-products such as fly ash as in producing concrete can improve properties in both fresh and hardened state of concrete. The water-binder ratio was used 0.30. The used sand was medium sand with the maximum size of coarse aggregate was 20 mm. The cement was Type I, which was Bosowa Cement produced by PT Bosowa. The percentages of fly ash to the total of a binder, which were used in this research, were 0, 10, 15, 20, 25 and 30%; while the super platicizer used was typed Naptha 511P. The results showed that the replacement cement up to 25 % of the total weight of binder resulted compressive strength higher than the minimum strength at one day of high-strength concrete.

Concrete decontamination by Electro-Hydraulic Scabbling (EHS). Topical report

International Nuclear Information System (INIS)

1996-01-01

Electro-Hydraulic Scabbling (EHS) technology and equipment for decontaminating concrete structures from radionuclides, organic substances, and hazardous metals is being developed by Textron Systems Division (TSD). This wet scabbling technique involves the generation of powerful shock waves and intense cavitation by a strong pulsed electric discharge in a water layer at the concrete surface. The high pressure impulse results in stresses which crack and peel off a concrete layer of a controllable thickness. Scabbling produces contaminated debris of relatively small volume which can be easily removed, leaving clean bulk concrete. This new technology is being developed under Contract No. DE-AC21-93MC30164. The project objective is to develop and demonstrate a cost-efficient, rapid, controllable process to remove the surface layer of contaminated concrete while generating minimal secondary waste. The primary target of this program is uranium-contaminated concrete floors which constitute a substantial part of the contaminated area at DOE weapon facilities

Long-term heat storage in calcium sulfoaluminate cement (CSA) based concrete

Energy Technology Data Exchange (ETDEWEB)

Kaufmann, Josef P.; Winnefeld, Frank [Empa Swiss Federal Laboratories for Materials Science and Technology, Duebendorf (Switzerland). Lab. for Concrete and Construction Chemistry

2011-07-01

In general, the selection of materials proposed for solar heat storage is based on one of two principal processes: sensible heat storage or latent heat storage. Sensible heat storage utilizes the specific heat capacity of a material, while latent heat storage is based on the change in enthalpy (heat content) associated with a phase change of the material. Long time sensible heat storage requires excellent thermal insulation whereas latent heat storage allows permanent (seasonal) storage without significant energy losses and any special insulation. Ettringite, one of the cement hydration products, exhibits a high dehydration enthalpy. Calcium sulfoaluminate cement based concrete containing a high amount of ettringite is henceproposed as an efficient latent heat storage material. Compared to conventional heat storage materials this innovative concrete mixture has a high loss-free storage energy density (> 100-150 kWh/m{sup 3}) which is much higher than the one of paraffin or the (loss-sensitive) sensible heat of water. Like common concrete the CSA-concrete is stable and even may carry loads. The dehydration of the CSA-concrete is achieved at temperatures below 100 C. The rehydration process occurs as soon as water (liquid or vapor) is added. In contrast to paraffin, the phase change temperature is not fixed and the latent heat may be recovered at any desired temperature. Furthermore the heat conductivity of this material is high, so that the energy transfer from/to an exchange medium is easy. Additionally CSA-concrete is not flammable and absolutely safe regarding any health aspects. The cost of such CSA-concrete isin the order of normal concrete. The main application is seen in house heating systems. Solar heat, mostly generated during the summer period by means of roof collectors, can be stored in CSA-concrete until the winter. A part or even the whole annual heatingenergy may be produced and saved locally by the householder himself. Additional applications may be

Effects of chemical and mineral additives and the water/cement ratio on the thermal resistance of Portland cement concrete

International Nuclear Information System (INIS)

Cesar, Leandro Cesar Dias; Morelli, Arnaldo C.; Baldo, Joao Baptista

1998-01-01

The exposure of Portland concrete to high temperatures (>250 deg C) can damage drastically the microstructural integrity of the material. Since the water/cement ratio as well as the inclusion of superplasticizers and mineral additives (silica fume) can alter constitutively and micro structurally the material, in this work it was investigated per effect of these additions on the damage resistance of portland concrete after exposure to high temperatures. (author)

Studies on the corrosion resistance of reinforced steel in concrete with ground granulated blast-furnace slag--An overview.

Science.gov (United States)

Song, Ha-Won; Saraswathy, Velu

2006-11-16

The partial replacement of clinker, the main constituent of ordinary Portland cement by pozzolanic or latent hydraulic industrial by-products such as ground granulated blast furnace slag (GGBFS), effectively lowers the cost of cement by saving energy in the production process. It also reduces CO2 emissions from the cement plant and offers a low priced solution to the environmental problem of depositing industrial wastes. The utilization of GGBFS as partial replacement of Portland cement takes advantage of economic, technical and environmental benefits of this material. Recently offshore, coastal and marine concrete structures were constructed using GGBFS concrete because high volume of GGBFS can contribute to the reduction of chloride ingress. In this paper, the influence of using GGBFS in reinforced concrete structures from the durability aspects such as chloride ingress and corrosion resistance, long term durability, microstructure and porosity of GGBFS concrete has been reviewed and discussed.

Palm Oil Fuel Ash (POFA and Eggshell Powder (ESP as Partial Replacement for Cement in Concrete

Directory of Open Access Journals (Sweden)

Mohamad Mazizah Ezdiani

2018-01-01

Full Text Available This study is an attempt to partially replace Ordinary Portland cement (OPC in concrete with palm oil fuel ash (POFA and eggshell powder (ESP. The mix proportions of POFA and ESP were varied at 10% of cement replacement and compared with OPC concrete as control specimen. The fineness of POFA is characterized by passing through 300 μm sieve and ESP by passing through 75 μm sieve. Compressive strength testing was conducted on concrete specimens to determine the optimum mix proportion of POFA and ESP. Generally the compressive strength of OPC concrete is higher compared to POFA-ESP concrete. Based on the results of POFA-ESP concrete overall, it shows that the optimum mix proportion of concrete is 6%POFA:4% ESP achieved compressive strength of 38.60 N/mm2 at 28 days. The compressive strength of OPC concrete for the same period was 42.37 N/mm2. Higher water demand in concrete is needed due to low fineness of POFA that contributing to low compressive strength of POFA-ESP concrete. However, the compressive strength and workability of the POFA-ESP concrete were within the ranges typically encountered in regular concrete mixtures indicating the viability of this replacement procedure for structural and non-structural applications.

Palm Oil Fuel Ash (POFA) and Eggshell Powder (ESP) as Partial Replacement for Cement in Concrete

Science.gov (United States)

Ezdiani Mohamad, Mazizah; Mahmood, Ali A.; Min, Alicia Yik Yee; Nur Nadhira A., R.

2018-03-01

This study is an attempt to partially replace Ordinary Portland cement (OPC) in concrete with palm oil fuel ash (POFA) and eggshell powder (ESP). The mix proportions of POFA and ESP were varied at 10% of cement replacement and compared with OPC concrete as control specimen. The fineness of POFA is characterized by passing through 300 μm sieve and ESP by passing through 75 μm sieve. Compressive strength testing was conducted on concrete specimens to determine the optimum mix proportion of POFA and ESP. Generally the compressive strength of OPC concrete is higher compared to POFA-ESP concrete. Based on the results of POFA-ESP concrete overall, it shows that the optimum mix proportion of concrete is 6%POFA:4% ESP achieved compressive strength of 38.60 N/mm2 at 28 days. The compressive strength of OPC concrete for the same period was 42.37 N/mm2. Higher water demand in concrete is needed due to low fineness of POFA that contributing to low compressive strength of POFA-ESP concrete. However, the compressive strength and workability of the POFA-ESP concrete were within the ranges typically encountered in regular concrete mixtures indicating the viability of this replacement procedure for structural and non-structural applications.

Sodium carbonate activated slag as cement replacement in autoclaved aerated concrete

NARCIS (Netherlands)

Yuan, B.; Straub, C.; Segers, S.; Yu, Q.; Brouwers, H.J.H.

2017-01-01

This paper aims to study the suitability of fully replacing cement by sodium carbonate activated slag in producing autoclaved aerated concrete (AAC). The material properties of the product are characterized in terms of green strength development, mechanical properties, pore related properties such

Study on concrete with partial replacement of cement by rice husk ash

Science.gov (United States)

Kaarthik Krishna, N.; Sandeep, S.; Mini, K. M.

2016-09-01

Increase in the demand of conventional construction materials and the need for providing a sustainable growth in the construction field has prompted the designers and developers to opt for ‘alternative materials’ feasible for use in construction. For this objective, the use of industrial waste products and agricultural byproducts are very constructive. These industrial wastes and agricultural by products such as Fly Ash, Rice Husk Ash, Silica Fume, and Slag can be replaced instead of cement because of their pozzolanic behavior, which otherwise requires large tract of lands for dumping. In the present investigation, Rice Husk Ash has been used as an admixture to cement in concrete and its properties has been studied. An attempt was also done to examine the strength and workability parameters of concrete. For normal concrete, mix design is done based on Indian Standard (IS) method and taking this as reference, mix design has been made for replacement of Rice Husk Ash. Four different replacement levels namely 5%, 10%, 15% and 20% are selected and studied with respect to the replacement method.

Special protective concretes

International Nuclear Information System (INIS)

Bouniol, P.

2001-01-01

Concrete is the most convenient material when large-scale radiation protection is needed. Thus, special concretes for nuclear purposes are used in various facilities like reactors, reprocessing centers, storage sites, accelerators, hospitals with nuclear medicine equipment, food ionization centers etc.. The recent advances made in civil engineering for the improvement of concrete durability and compactness are for a large part transposable to protection concretes. This article presents the basic knowledge about protection concretes with the associated typological and technological aspects. A large part is devoted to the intrinsic properties of concretes and to their behaviour in irradiation and temperature conditions: 1 - definition and field of application of special protective concretes; 2 - evolution of concepts and technologies (durability of structures, techniques of formulation, new additives, market evolution); 3 - design of protective structures (preliminary study, radiation characteristics, thermal constraints, damping and dimensioning, mechanical criteria); 4 - formulation of special concretes (general principles, granulates, hydraulic binders, pulverulent additives, water/cement ratio, reference composition of some special concretes); 5 - properties of special concretes (damping and thermo-mechanical properties); 6 - induced-irradiation and temperature phenomena (activation, radiolysis, mineralogical transformations, drying, shrinking, creep, corrosion of reinforcement). (J.S.)

Synthesis document on the long life behavior of packages: phenomenological reference document ''concrete packages'' 2004

International Nuclear Information System (INIS)

Richet, C.; Le Bescop, P.; Galle, Ch.; Peycelon, H.; Bejaoui, S.; Pointeau, I.; L'Hostis, V.; Bary, B.

2004-12-01

In the framework of the law of 1991 on the radioactive wastes management, the CEA realized studies on the long time behavior of packages based on concrete for storage and disposal. This document takes stock on the 2003 and 2004 studies. It presents the cement materials specificities, their durability, the transport and the retention in the hydraulic binders, the couplings between degradation and hydraulic properties evolution of solutes and mechanic. The studies are applied to the the evaluation of ''CLT '' concrete packages. (A.L.B.)

Stainless and Galvanized Steel, Hydrophobic Admixture and Flexible Polymer-Cement Coating Compared in Increasing Durability of Reinforced Concrete Structures

Science.gov (United States)

Tittarelli, Francesca; Giosuè, Chiara; Mobili, Alessandra

2017-08-01

The use of stainless or galvanized steel reinforcements, a hydrophobic admixture or a flexible polymer-cement coating were compared as methods to improve the corrosion resistance of sound or cracked reinforced concrete specimens exposed to chloride rich solutions. The results show that in full immersion condition, negligible corrosion rates were detected in all cracked specimens, except those treated with the flexible polymer-cement mortar as preventive method against corrosion and the hydrophobic concrete specimens. High corrosion rates were measured in all cracked specimens exposed to wet-dry cycles, except for those reinforced with stainless steel, those treated with the flexible polymer-cement coating as restorative method against reinforcement corrosion and for hydrophobic concrete specimens reinforced with galvanized steel reinforcements.

Selected Bibliography on Fiber-Reinforced Cement and Concrete. Supplement Number 4.

Science.gov (United States)

1982-08-01

Building Industry," L’Industria Italiana del Cemento , Vol 50, No. 12, Dec 1980, pp 1135-1144. 19. Bartos, P., "Pullout Failure of Fibres Embedded in Cement...Vol 43, No. 11, Nov 1977, pp 561-564. 21. Bassan, M., "Model of Behavior of Fiber-Reinforced Concretes Under Impact Stresses," il Cemento , Vol 74, No...Pastes," il Cemento , Vol 75, No. 3, Jul-Sep 1978, pp 277-284. 210. Mills, R. H., "Age-Embrittlement of Glass-Reinforced Concrete Containing Blastfurance

HIGHLY EFFECTIVE CHEMICAL MODIFIERS FOR PRODUCTION OF CONCRETES WITH PRE-SET PROPERTIES

Directory of Open Access Journals (Sweden)

Tkach Evgeniya Vladimirovna

2012-10-01

Full Text Available The paper demonstrates the application of industrial by-products and recycled materials. Waterproofing admixtures improve the structure and the properties of the cement stone. Development and preparation of highly effective waterproofing modifiers of durable effect, as well as development of the process procedure parameters, including mixing, activation, heat treatment, etc. are to be implemented. The composition of waterproofing modifiers is to be fine-tuned to synergize the behaviour of various ingredients of cement systems to assure the substantial improvement of their strength, freeze- and corrosion resistance. Multi-functional waterproofing admixtures were used to produce highly effective modified concretes. The key idea of the new method of modifying cement-based building materials is that the waterproofing admixture concentration is to exceed 10% of the weight of the binding agent within the per-unit weight of the cement stone, given that its strength does not deteriorate. GKM-type modifier coupled with organo-mineral waterproofing admixture concentration agent GT-M may be recommended for mass use in the manufacturing of hydraulic concrete and reinforced concrete products. Overview of their practical implementation has proven that waterproofing modifier GKM-S, if coupled with waterproofing admixture concentration agent GT-M, improves the corrosion control inside the cement stone and makes it possible to manufacture durable concrete and reinforced concrete products that demonstrate pre-set physical and processing behaviour. Comprehensive concrete modification by modifier GKM-S and waterproofing admixture concentration agent GT-M may be regarded as one of the most ambitious methods of production of highly effective waterproof concretes.

Nano-modified cement composites and its applicability as concrete repair material

Science.gov (United States)

Manzur, Tanvir

Nanotechnology or Nano-science, considered the forth industrial revolution, has received considerable attention in the past decade. The physical properties of a nano-scaled material are entirely different than that of bulk materials. With the emerging nanotechnology, one can build material block atom by atom. Therefore, through nanotechnology it is possible to enhance and control the physical properties of materials to a great extent. Composites such as concrete materials have very high strength and Young's modulus but relatively low toughness and ductility due to their covalent bonding between atoms and lacking of slip systems in the crystal structures. However, the strength and life of concrete structures are determined by the microstructure and mass transfer at nano scale. Cementitious composites are amenable to manipulation through nanotechnology due to the physical behavior and size of hydration products. Carbon nanotubes (CNT) are nearly ideal reinforcing agent due to extremely high aspect ratios and ultra high strengths. So there is a great potential to utilize CNT in producing new cement based composite materials. It is evident from the review of past literature that mechanical properties of nanotubes reinforced cementitious composites have been highly variable. Some researches yielded improvement in performance of CNT-cement composites as compared to plain cement samples, while other resulted in inconsequential changes in mechanical properties. Even in some cases considerable less strengths and modulus were obtained. Another major difficulty of producing CNT reinforced cementitious composites is the attainment of homogeneous dispersion of nanotubes into cement but no standard procedures to mix CNT within the cement is available. CNT attract more water to adhere to their surface due to their high aspect ratio which eventually results in less workability of the cement mix. Therefore, it is extremely important to develop a suitable mixing technique and an

Properties of backfilling material for solidifying miscellaneous waste using recycled cement from waste concrete

International Nuclear Information System (INIS)

Matsuda, Atsuo; Yamamoto, Kazuo; Konishi, Masao; Iwamoto, Yoshiaki; Yoshikane, Toru; Koie, Toshio; Nakashima, Yoshio.

1997-01-01

A large reduction of total radioactive waste is expected, if recycled cement from the waste concrete of decommissioned nuclear power plants would be able to be used the material for backfilling mortar among the miscellaneous waste. In this paper, we discuss the hydration, strength and consistency of recycled cement compared with normal portland cement. The strength of recycled cement mortar is lower than that of normal portland cement mortar on the same water to cement ratio. It is possible to obtain the required strength to reduce the water to cement ratio by using of high range water-reducing AE agent. According to reducing of water to cement ratio, the P-type funnel time of mortar increase with the increase of its viscosity. However, in new method of self-compactability for backfilling mortar, it became evident that there was no difference between the recycled cement and normal portland cement on the self-compactability. (author)

Portland cement concrete pavement review of QC/QA data 2000 through 2009.

Science.gov (United States)

2011-04-01

This report analyzes the Quality Control/Quality Assurance (QC/QA) data for Portland cement concrete pavement : (PCCP) awarded in the years 2000 through 2009. Analysis of the overall performance of the projects is accomplished by : reviewing the Calc...

An Experimental Study On Carbonation Of Plain And Blended Cement Concrete

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Yunusa Alhassan

2017-08-01

Full Text Available This paper presents a laboratory investigation on the early age properties and carbonation of concrete containing Ground Granulated Blast Furnace GGBS in an inland environment. Properties of concrete made with GGBS blended cement was characterized in terms of physical and chemical composition at early-age. In addition the effects of inland exposure condition on the durability performance of companion concrete were also investigated in the medium term. Concrete cubes were made using various concrete mixtures of water-binder ratios wb 0.40 0.50 0.60 0.75 and binder contents 300 350 400 450 kgm3. Concrete cube of 100 mm size were cast and cured in water for 3 7 or 28 days then characterized at early-ages in terms of its physical and chemical properties. Companion concrete samples were exposed indoor or outdoors to undergo carbonation under natural environment. At the end of the varying exposure period 6 12 18 and 24 months the concrete cube samples were characterized in terms of carbonation depths. The results of the concrete early-age properties and medium-term durability characterisation were analyzed. The results show that increased knowledge of concrete materials concrete early-age properties and its exposure conditions are vital in durability considerations for RC structures.

Comparative Study of Portland Cement-based and Zeolite-based Concretes in Terms of Hexavalent Chromium Leaching

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Oravec Jozef

2016-12-01

Full Text Available The paper presents the results of the leaching study of Portland cement-based and zeolite-based concretes regarding water soluble hexavalent chromium. Three leaching water media (distilled water, rain water, and Britton-Robinson buffer of various pH values were under investigation. The correlation between pH and leached-out concentrations of chromium was not confirmed. The content of hexavalent water-soluble chromium in leachates of zeolite-based concretes was found to be higher than that in leachates of Portland cement-based samples.

Influence of the waste glass in the axial compressive strength of Portland cement concrete

International Nuclear Information System (INIS)

Miranda Junior, E.J.P.; Paiva, A.E.M.

2012-01-01

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

Recycled Portland cement concrete pavements : Part II, state-of-the art summary.

Science.gov (United States)

1979-01-01

This report constitutes a review of the literature concerning recycling of portland cement concrete pavements by crushing the old pavement and reusing the crushed material as aggregate in a number of applications. A summary of the major projects cond...

Blasted copper slag as fine aggregate in Portland cement concrete.

Science.gov (United States)

Dos Anjos, M A G; Sales, A T C; Andrade, N

2017-07-01

The present work focuses on assessing the viability of applying blasted copper slag, produced during abrasive blasting, as fine aggregate for Portland cement concrete manufacturing, resulting in an alternative and safe disposal method. Leaching assays showed no toxicity for this material. Concrete mixtures were produced, with high aggregate replacement ratios, varying from 0% to 100%. Axial compressive strength, diametrical compressive strength, elastic modulus, physical indexes and durability were evaluated. Assays showed a significant improvement in workability, with the increase in substitution of fine aggregate. With 80% of replacement, the concrete presented lower levels of water absorption capacity. Axial compressive strength and diametrical compressive strength decreased, with the increase of residue replacement content. The greatest reductions of compressive strength were found when the replacement was over 40%. For tensile strength by diametrical compression, the greatest reduction occurred for the concrete with 80% of replacement. After the accelerated aging, results of mechanic properties showed a small reduction of the concrete with blasted copper slag performance, when compared with the reference mixture. Results indicated that the blasted copper slag is a technically viable material for application as fine aggregate for concrete mixtures. Copyright © 2017 Elsevier Ltd. All rights reserved.

Experimental characterization of the concrete behaviour under high confinement: influence of the saturation ratio and of the water/cement ratio

International Nuclear Information System (INIS)

Vu, X.H.

2007-08-01

The objective of this thesis is to experimentally characterize the influence of the saturation ratio and of the water/cement ratio of concrete on its behaviour under high confinement. This thesis lies within a more general scope of the understanding of concrete behaviour under severe loading situations (near field detonation or ballistic impacts). A near field detonation or an impact on a concrete structure generate very high levels of stress associated with complex loading paths in the concrete material. To validate concrete behaviour models, experimental results are required. The work presented in this thesis concerns tests conducted using a static triaxial press that allows to obtain stress levels of the order of the giga Pascal. The porous character of concrete and the high confinement required on the one hand, a development of a specimen protection device, and on the other hand, a development of an instrumentation with strain gauges, which is unprecedented for such high confinements. Hydrostatic and triaxial tests, conducted on the one hand on model materials and on the other hand on concrete, allowed to validate the developed experimental procedures as well as the technique of strain and stress measurements. The studies concerning the influence of the saturation ratio and of the water/cement ratio of concrete on its behaviour required the formulation of a plain baseline concrete and of two modified concretes with different water/cement ratios. The analysis of triaxial tests performed on the baseline concrete shows that the saturation ratio of concrete has a major influence on its static behaviour under high confinement. This influence is particularly marked for the concrete loading capacity and for the shape of limit state curves for saturation ratios greater than 50%. The concrete loading capacity increases with the confinement pressure for tests on dry concrete whereas beyond a given confinement pressure, it remains limited for wet or saturated concrete

Statistical analysis of electrical resistivity as a tool for estimating cement type of 12-year-old concrete specimens

NARCIS (Netherlands)

Polder, R.B.; Morales-Napoles, O.; Pacheco, J.

2012-01-01

Statistical tests on values of concrete resistivity can be used as a fast tool for estimating the cement type of old concrete. Electrical resistivity of concrete is a material property that describes the electrical resistance of concrete in a unit cell. Influences of binder type, water-to-binder

Petrographic Analysis of Portland Cement Concrete Cores from Pease Air National Guard Base, New Hampshire

Science.gov (United States)

2016-11-01

Petrographic Analysis of Portland Cement Concrete Cores from Pease Air National Guard Base, New Hampshire E n g in e e r R e s e a rc h a n d...id, age of the concrete being evaluated and tests performed...4 3 Preface This study was conducted in support of the Air Force Civil Engineer Center (AFCEC) to assess concrete obtained from Pease

A Generic Procedure for the Assessment of the Effect of Concrete Admixtures on the Sorption of Radionuclides on Cement: Concept and Selected Results

International Nuclear Information System (INIS)

Glaus, M.A.; Laube, A.; Van Loon, L.R.

2004-01-01

A screening procedure is proposed for the assessment of the effect of concrete admixtures on the sorption of radionuclides by cement. The procedure is both broad and generic, and can thus be used as input for the assessment of concrete admixtures which might be used in the future. The experimental feasibility and significance of the screening procedure are tested using selected concrete admixtures: i.e. sulfonated naphthalene-formaldehyde condensates, lignosulfonates, and a plasticiser used at PSI for waste conditioning. The effect of these on the sorption properties of Ni(II), Eu(III) and Th(IV) in cement is investigated using crushed Hardened Cement Paste (HCP), as well as cement pastes prepared in the presence of these admixtures. Strongly adverse effects on the sorption of the radionuclides tested are observed only in single cases, and under extreme conditions: i.e. at high ratios of concrete admixtures to HCP, and at low ratios of HCP to cement pore water. Under realistic conditions, both radionuclide sorption and the sorption of isosaccharinic acid (a strong complexant produced in cement-conditioned wastes containing cellulose) remain unaffected by the presence of concrete admixtures, which can be explained by the sorption of them onto the HCP. The pore-water concentrations of the concrete admixtures tested are thereby reduced to levels at which the formation of radionuclide complexes is no longer of importance. Further, the Langmuir sorption model, proposed for the sorption of concrete admixtures on HCP, suggests that the HCP surface does not become saturated, at least for those concrete admixtures tested. (author)

A Generic Procedure for the Assessment of the Effect of Concrete Admixtures on the Sorption of Radionuclides on Cement: Concept and Selected Results

Energy Technology Data Exchange (ETDEWEB)

Glaus, M.A.; Laube, A.; Van Loon, L.R

2004-03-01

A screening procedure is proposed for the assessment of the effect of concrete admixtures on the sorption of radionuclides by cement. The procedure is both broad and generic, and can thus be used as input for the assessment of concrete admixtures which might be used in the future. The experimental feasibility and significance of the screening procedure are tested using selected concrete admixtures: i.e. sulfonated naphthalene-formaldehyde condensates, lignosulfonates, and a plasticiser used at PSI for waste conditioning. The effect of these on the sorption properties of Ni(II), Eu(III) and Th(IV) in cement is investigated using crushed Hardened Cement Paste (HCP), as well as cement pastes prepared in the presence of these admixtures. Strongly adverse effects on the sorption of the radionuclides tested are observed only in single cases, and under extreme conditions: i.e. at high ratios of concrete admixtures to HCP, and at low ratios of HCP to cement pore water. Under realistic conditions, both radionuclide sorption and the sorption of isosaccharinic acid (a strong complexant produced in cement-conditioned wastes containing cellulose) remain unaffected by the presence of concrete admixtures, which can be explained by the sorption of them onto the HCP. The pore-water concentrations of the concrete admixtures tested are thereby reduced to levels at which the formation of radionuclide complexes is no longer of importance. Further, the Langmuir sorption model, proposed for the sorption of concrete admixtures on HCP, suggests that the HCP surface does not become saturated, at least for those concrete admixtures tested. (author)

Degradation of normal portland and slag cement concrete under load, due to reinforcement corrosion

International Nuclear Information System (INIS)

Philipose, K.E.; Beaudoin, J.J.; Feldman, R.F.

1992-08-01

The corrosion of reinforcement is one of the major degradation mechanisms of reinforced concrete elements. The majority of studies published on concrete-steel corrosion have been conducted on unstressed specimens. Structural concrete, however, is subjected to substantial strain near the steel reinforcing bars that resist tensile loads, which results in a system of microcracks. This report presents the initial results of an investigation to determine the effect of applied load and microcracking on the rate of ingress of chloride ion and corrosion of steel in concrete. Simply-supported concrete beam specimens were loaded to give a maximum strain of about 600 με on the tension face. Chloride ion ingress on cores taken from loaded specimens was monitored using energy-dispersive X-ray analysis techniques. Corrosion current and rate measurements using linear polarization electrochemical techniques were also obtained on the same loaded specimens. Variables investigated included two concrete types, two steel cover-depths, three applied load levels, bonded and unbonded rebars and the exposure of tension and compression beam faces to chloride solution. One concrete mixture was made with type 10 Portland cement, the other with 75% blast furnace slag, 22% type 50 cement and 3% silica fume. The rate of chloride ion ingress into reinforced concrete, and hence the time for chloride ion to reach the reinforcing steel, is shown to be dependent on applied load and the concrete quality. The dependence of corrosion process descriptors - passive layer formation, initiation period and propagation period - on the level of applied load is discussed. (Author) (6 refs., 3 tabs., 10 figs.)

Diffusion under water-saturated conditions in PFA/OPC-based structural concrete

International Nuclear Information System (INIS)

Harris, A.W.; Nickerson, A.K.

1990-05-01

A substantial proportion of the volume of the UK radioactive waste repository is likely to be composed of materials based on hydraulic cements. This includes the structural components, which are likely to be manufactured from concrete. The mass transport characteristics of dissolved species for a typical structural concrete, based on a mixture of pulverised fuel ash and ordinary Portland cement, have been measured in a water-saturated condition. Both the water permeability and the diffusion parameters (for caesium, strontium and iodide ion and tritiated water diffusion) are low compared to values obtained for other structural concretes. The intrinsic diffusion coefficients for iodide and caesium ions are in the range 2-5x10 -14 m 2 s -1 . There is no evidence of significant sorption of any of the diffusants studied. (author)

Evaluating portland cement concrete degradation by sulphate exposure through artificial neural networks modeling

International Nuclear Information System (INIS)

Oliveira, Douglas Nunes de; Bourguignon, Lucas Gabriel Garcia; Tolentino, Evandro; Costa, Rodrigo Moyses; Tello, Cledola Cassia Oliveira de

2015-01-01

A concrete is durable if it has accomplished the desired service life in the environment in which it is exposed. The durability of concrete materials can be limited as a result of adverse performance of its cement-paste matrix or aggregate constituents under either chemical or physical attack. Among other aggressive chemical exposures, the sulphate attack is an important concern. Water, soils and gases, which contain sulphate, represent a potential threat to the durability of concrete structures. Sulphate attack in concrete leads to the conversion of the hydration products of cement to ettringite, gypsum, and other phases, and also it leads to the destabilization of the primary strength generating calcium silicate hydrate (C-S-H) gel. The formation of ettringite and gypsum is common in cementitious systems exposed to most types of sulphate solutions. The present work presents the application of the neural networks for estimating deterioration of various concrete mixtures due to exposure to sulphate solutions. A neural networks model was constructed, trained and tested using the available database. In general, artificial neural networks could be successfully used in function approximation problems in order to approach the data generation function. Once data generation function is known, artificial neural network structure is tested using data not presented to the network during training. This paper is intent to provide the technical requirements related to the production of a durable concrete to be used in the structures of the Brazilian near-surface repository of radioactive wastes. (author)

Evaluating portland cement concrete degradation by sulphate exposure through artificial neural networks modeling

Energy Technology Data Exchange (ETDEWEB)

Oliveira, Douglas Nunes de; Bourguignon, Lucas Gabriel Garcia; Tolentino, Evandro, E-mail: tolentino@timoteo.cefetmg.br [Centro Federal de Educacao Tecnologica de Minas Gerais (CEFET-MG), Timoteo, MG (Brazil); Costa, Rodrigo Moyses, E-mail: rodrigo@moyses.com.br [Universidade de Itauna, Itauna, MG (Brazil); Tello, Cledola Cassia Oliveira de, E-mail: tellocc@cdtn.br [Centro de Desenvolvimento da Tecnologia Nucelar (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil)

2015-07-01

A concrete is durable if it has accomplished the desired service life in the environment in which it is exposed. The durability of concrete materials can be limited as a result of adverse performance of its cement-paste matrix or aggregate constituents under either chemical or physical attack. Among other aggressive chemical exposures, the sulphate attack is an important concern. Water, soils and gases, which contain sulphate, represent a potential threat to the durability of concrete structures. Sulphate attack in concrete leads to the conversion of the hydration products of cement to ettringite, gypsum, and other phases, and also it leads to the destabilization of the primary strength generating calcium silicate hydrate (C-S-H) gel. The formation of ettringite and gypsum is common in cementitious systems exposed to most types of sulphate solutions. The present work presents the application of the neural networks for estimating deterioration of various concrete mixtures due to exposure to sulphate solutions. A neural networks model was constructed, trained and tested using the available database. In general, artificial neural networks could be successfully used in function approximation problems in order to approach the data generation function. Once data generation function is known, artificial neural network structure is tested using data not presented to the network during training. This paper is intent to provide the technical requirements related to the production of a durable concrete to be used in the structures of the Brazilian near-surface repository of radioactive wastes. (author)

Corrosion rate of rebars from linear polarization resistance and destructive analysis in blended cement concrete after chloride loading

NARCIS (Netherlands)

Polder, R.B.; Peelen, W.H.A.; Bertolini, L.; Guerriere, M.

2002-01-01

Concrete specimens with various binders including Portland cement, fly ash, blast furnace slag and composite cement and three water-to-cement ratios were subjected to cyclic wetting with salt solution and drying. Specimens contained six mild steel bars at two cover depths and two activated titanium

Pore structure modification of cement concretes by impregnation with sulfur-containing compounds

Directory of Open Access Journals (Sweden)

YANAKHMETOV Marat Rafisovich

2015-02-01

Full Text Available The authors study how the impregnation with sulfur-containing compounds changes the concrete pore structure and how it influences on the water absorption and watertightness. The results of this research indicate that impregnation of cement concrete with water-based solution of polysulphide modifies pore structure of cement concrete in such a way that it decreases total and effective porosity, reduces water absorption and increases watertightness. The proposed impregnation based on mineral helps to protect for a long time the most vulnerable parts of buildings – basements, foundations, as well as places on the facades of buildings exposed to rain, snow and groundwater. Application of the new product in the construction industry can increase the durability of materials, preventing the destruction processes caused by weathering, remove excess moisture in damp basements. The surfaces treated by protective compounds acquire antisoiling properties for a long time, and due to reduced thermal conductivity the cost of heating buildings is decreased. The effectiveness of the actions and the relatively low cost of proposed hydrophobizator makes it possible to spread widely the proposed protection method for building structures.

Temperature Characteristics of Porous Portland Cement Concrete during the Hot Summer Session

Directory of Open Access Journals (Sweden)

Liqun Hu

2017-01-01

Full Text Available Pavement heats the near-surface air and affects the thermal comfort of the human body in hot summer. Because of a large amount of connected porosity of porous Portland cement concrete (PPCC, the thermal parameters of PPCC are much different from those of traditional Portland cement concrete (PCC. The temperature change characteristics of PPCC and the effects on surrounding environment are also different. A continuous 48-hour log of temperature of a PCC and five kinds of PPCC with different porosity were recorded in the open air in the hot summer. The air temperatures at different heights above concrete specimens were tested using self-made enclosed boxes to analyze the characteristics of near-surface air temperature. The output heat flux of different concrete specimens was calculated. The results show that the PPCC has higher temperature in the daytime and lower temperature in the nighttime and larger temperature gradient than the PCC. The air temperature above PPCC is lower than that of PCC after solar radiation going to zero at night. The total output heat flux of PPCC is slightly smaller in the daytime and significantly smaller at night than that of PCC. The results of tests and calculations indicate that PPCC contributes to the mitigation of heating effect of pavement on the near-surface air.

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

Directory of Open Access Journals (Sweden)

Babafemi A.J.

2012-01-01

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.

Porous concrete mixtures for pervious urban pavements

Directory of Open Access Journals (Sweden)

Castro, J.

2007-08-01

Full Text Available The present study aimed to analyze the hydraulic and mechanical behaviour of a series of roller-compacted, laboratory porous concrete mixtures. The mix design variables examined were the actual void ratio in the hardened concrete and the water/cement ratio. From these results the better dosages from the mechanical and hydraulical behaviour point of view were determined. One of the designs developed was found to exhibit excellent hydraulic capacity and 20% greater strength than the mixtures recommended in the literature. Moreover, concrete with an actual void ratio of only 14% was observed to meet permeability requirements. Maximum flexural strength of concretes with different w/c ratios was achieved with a cement paste content of 250 l/m3. Relationships were found between the void ratio and both 28-day concrete permeability and flexural strength. Finally, the doses exhibiting the best mechanical and hydraulic performance were identified.El trabajo realizado en este estudio consistió en analizar el comportamiento de diferentes dosificaciones de mezclas de hormigón poroso, fabricadas en laboratorio y compactadas con rodillo pesado para simular las condiciones de terreno. Las variables consideradas para el diseño de las mezclas fueron el porcentaje real de huecos en el hormigón endurecido y la razón agua/cemento. A partir de estos resultados se determinaron las dosificaciones que presentan mejor comportamiento desde el punto de vista mecánico e hidráulico. Los resultados muestran que existe una dosificación de hormigón poroso, distinta a las encontradas actualmente en la literatura internacional, que permite obtener resistencias hasta 20% más altas, manteniendo todavía una excelente capacidad hidráulica. Se determinó que una permeabilidad suficiente se puede obtener con un porcentaje real de huecos de 14%, y que agregar pasta de cemento en una proporción de 250 l/m3 permite maximizar la resistencia a flexotracción de hormigones que

Another look at the deterioration of calcium aluminate cement concrete

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Jambor, Jaromir

1996-03-01

Full Text Available Potential degradation of concrete structures made of calcium aluminate cement (CAC is well known and is caused by transformation (conversion of the thermodynamically metastable into stable calcium aluminate hydrate phases. This recrystallization is influenced by temperature and humidity; the structural degradation of the concrete itself thus its loss of strength, is strongly related to the pore structure of the hydrated cement paste, the critical parameters being the total volume of pores below 15-20 nm and the median micropore radius. This constitutes a novel procedure for evaluation of existing CAC concrete structure.

La degradación potencial de estructuras de hormigón elaboradas con cemento aluminoso (CA es bien conocida. Este deterioro está causado por la recristalización (conversión de las fases del aluminato cálcico que son termodinámicamente metastables, en fases estables. En esta recristalización influye la temperatura y la humedad. Tanto la degradación del propio hormigón, como su pérdida de resistencias están relacionadas estrechamente con la estructura porosa de la pasta del cemento hidratado, siendo parámetros críticos el volumen total de los poros inferiores a 15-20 nm y el tamaño medio de los radios de los microporos. Esto constituye un nuevo procedimiento para evaluar las estructuras existentes de hormigón de cemento aluminoso (CA.

Reuse of By-Products from Ready-Mixed Concrete Plants for the Production of Cement Mortars

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Monika Zervaki

2013-06-01

Full Text Available This study was motivated by the necessity to recycle sludge water resulting from washing out concrete mixing trucks - a problem of both environmental and economic importance for the ready-mixed concrete industry. Sludge water from ready-mixed concrete plants as well as dry sludge, which is derived from the settling of the water, are hazardous for disposal due to their high pH value (pH>11.5. In this work, cement mortars were composed using either sludge water after various treatment, or dry sludge in several ratios. The cement mortars were tested for their workability and strength development. The purpose of this experimental design was to prove that sludge water, as well as sludge in a wet or dry form, can be used in the production of mortars without degrading any of their properties.

Strength development in concrete with wood ash blended cement and use of soft computing models to predict strength parameters.

Science.gov (United States)

Chowdhury, S; Maniar, A; Suganya, O M

2015-11-01

In this study, Wood Ash (WA) prepared from the uncontrolled burning of the saw dust is evaluated for its suitability as partial cement replacement in conventional concrete. The saw dust has been acquired from a wood polishing unit. The physical, chemical and mineralogical characteristics of WA is presented and analyzed. The strength parameters (compressive strength, split tensile strength and flexural strength) of concrete with blended WA cement are evaluated and studied. Two different water-to-binder ratio (0.4 and 0.45) and five different replacement percentages of WA (5%, 10%, 15%, 18% and 20%) including control specimens for both water-to-cement ratio is considered. Results of compressive strength, split tensile strength and flexural strength showed that the strength properties of concrete mixture decreased marginally with increase in wood ash contents, but strength increased with later age. The XRD test results and chemical analysis of WA showed that it contains amorphous silica and thus can be used as cement replacing material. Through the analysis of results obtained in this study, it was concluded that WA could be blended with cement without adversely affecting the strength properties of concrete. Also using a new statistical theory of the Support Vector Machine (SVM), strength parameters were predicted by developing a suitable model and as a result, the application of soft computing in structural engineering has been successfully presented in this research paper.

Study on the Utilization of Paper Mill Sludge as Partial Cement Replacement in Concrete

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Nazar A.M. Md

2014-03-01

Full Text Available A major problem arising from the widespread use of forestry biomass and processed timber waste as fuel is related to the production of significant quantities of ash as a by-product from the incineration of such biomasses. A major portion (approximately 70% of the wood waste ash produced is land-filled as a common method of disposal. If the current trend continues with waste products, such as paper mill sludge landfills, a large amount of space would be required by 2020. A revenue study was conducted as a result of investigations into the use of paper mill sludge as recycled materials and additives in concrete mixes for use in construction projects. The study had to provide the assurance that the concrete produced had the correct mechanical strength. Concrete mixes containing paper mill sludge were prepared, and their basic strength characteristics such as the compressive strength, flexural strength, ultra pulse velocity and dynamic modulus elasticity were tested. Four concrete mixes, i.e. a control mix, and a 10%, 20%, and 30% mix of paper mill sludge as cement replacement for concrete were prepared with a DoE mix design by calculating the weight of cement, sand and aggregate. The performance of each concrete specimen was compared with the strength of the control mix. As a result, when the percentage of paper mill sludge in the concrete increased, the strength decreased. Overall, a high correlation was observed between density and strength of the concrete containing paper mill sludge.

Characterization and formulation of a new eco-friendly hydraulic binder based on combination of inorganic and organic admixtures

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Khudhair M.H.R.

2018-01-01

Full Text Available This work aims to valorize a mineral and natural resources such as the Limestone Fillers (F-Lime and the Natural Pozzolan (PN by incorporating them into the formulation matrix of cement or concrete. In order to minimize the CO2 emissions into the atmosphere, to reduce the energy and raw materials consumption and as well as, to improve the physical and mechanical properties in fresh cement paste and of mortar or concrete in the hardened state. In this present manuscript, we substituted the clinker by the combination between the F-Lime and NP at 40% by weight of cement with steps of 5% with the admixture of superplasticizers. The influences of the incorporation of these additions on physical and mechanical properties of mortar or concrete in the fresh cement paste and hardened state were evaluated. The obtained results by different formulations elaborated to show that the replacement a part of clinker by the mixing of F-Lime and PN has produced a new hydraulic binder eco-friendly and durable with improved physicochemical, physical and mechanical properties. These results show that we have succeeded to manufacture, characteristic and formulated of new ecofriendly hydraulic binder and sustainable with improved physical, chemical, and mechanical properties while minimizing greenhouse gas emissions on one hand and the reducing the energy raw materials consumption on the other hand.

Corrosion potential: influence of moisture, water-cement ratio, chloride content and concrete cover

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M. H. F. Medeiros

Full Text Available ABSTRACT The method of measuring the corrosion potential is used as an electrochemical tool for helping the monitoring of the corrosion of reinforcements of concrete structures. As a criterion for evaluating results it is common to use intervals of corrosion potential and their correlation with corrosion probability, as precognizes ASTM C 876:2015. With this criterion, it is possible to establish an overview of the thermodynamic situation of corrosion in the structure or in the test specimen in laboratory. However, the method is influenced by several factors related with the concrete, the environment and with procedures adopted at the moment of executing the readings. Aiming to provide information to guide the technical and scientific environment regarding the right use of this type of non-destructive testing, the objective of this work is to evaluate some possible factors influencing the reading of corrosion potential, such as: moisture content of the concrete, water/cement ratio, thickness of the concrete cover and degree of contamination by chlorides. Results indicate that moisture and degree of contamination of the concrete by chloride ions had a tendency of making the corrosion potential more electronegative. Besides, it was verified that the influence of the cover is different for the case of contaminated concrete (1% of chlorides by mass of cement and not contaminated with chlorides: the influence of the thickness of the cover, in the case of concrete contaminated by chlorides, was inversely proportional, in other words, the greater the cover thickness is, the less electronegative the value of the corrosion potential will be. On the other hand, in cases of concretes without chlorides, the effect of the cover thickness in the readings or corrosion potential was irrelevant. All this information was proved with 95% of statistical significance.

Properties and durability of metakaolin blended cements: mortar and concrete

Directory of Open Access Journals (Sweden)

Abbas, Rafik

2010-12-01

Full Text Available This article explores the effect of metakaolin, a pozzolan, on concrete performance. Compressive and splitting tensile strength were found for specimens cured for up to 360 and 90 days, respectively. Changes were recorded in the compressive strength of specimens exposed to salt (chloride and sulfatechloride solutions, and chloride penetration and binding capacity were measured. The findings were compared to the results for concrete prepared with ordinary Portland (OPC and moderate heat of hydration (Type II cement. MK was found to have a very positive effect on 28-day concrete strength, due to microstructure improvement of the hydrated cement. Replacing cement with metakaolin effectively raised concrete resistance to chloride attack. Concrete containing metakaolin proved to be substantially more durable in sulfate-chloride environment.

En este trabajo se estudia el efecto del metacaolín sobre las prestaciones del hormigón. Las probetas curadas a 360 y 90 días se sometieron a ensayos de resistencia a compresión y de tracción indirecta respectivamente. Se hizo un seguimiento de la resistencia a la compresión de los materiales ante el ataque de sales (soluciones de cloruro y de sulfato-cloruro y, se midió la penetración de cloruros y la capacidad de los hormigones de inmovilizar estos iones. Los resultados se compararon con los obtenidos con hormigones elaborados con cemento pórtland ordinario (OPC y, con cemento de calor de hidratación moderado (tipo II. El MK resultó influir muy positivamente en la resistencia del hormigón a 28 días debido a la mejora de la microestructura del cemento hidratado. La sustitución de cemento por metacaolín aumentó la resistencia del hormigón al ataque de cloruros. El hormigón con metacaolín demostró ser más duradero en entornos de sulfato-cloruro que los hormigones elaborados con OPC o con cemento de tipo II. Los perfiles de concentración de cloruros a distintas profundidades y la

Cement replacement materials. Properties, durability, sustainability

International Nuclear Information System (INIS)

Ramezanianpour, Ali Akbar

2014-01-01

The aim of this book is to present the latest findings in the properties and application of Supplementary Cementing Materials and blended cements currently used in the world in concrete. Sustainability is an important issue all over the world. Carbon dioxide emission has been a serious problem in the world due to the greenhouse effect. Today many countries agreed to reduce the emission of CO2. Many phases of cement and concrete technology can affect sustainability. Cement and concrete industry is responsible for the production of 7% carbon dioxide of the total world CO2 emission. The use of supplementary cementing materials (SCM), design of concrete mixtures with optimum content of cement and enhancement of concrete durability are the main issues towards sustainability in concrete industry.

Strength development in concrete with wood ash blended cement and use of soft computing models to predict strength parameters

Directory of Open Access Journals (Sweden)

S. Chowdhury

2015-11-01

Full Text Available In this study, Wood Ash (WA prepared from the uncontrolled burning of the saw dust is evaluated for its suitability as partial cement replacement in conventional concrete. The saw dust has been acquired from a wood polishing unit. The physical, chemical and mineralogical characteristics of WA is presented and analyzed. The strength parameters (compressive strength, split tensile strength and flexural strength of concrete with blended WA cement are evaluated and studied. Two different water-to-binder ratio (0.4 and 0.45 and five different replacement percentages of WA (5%, 10%, 15%, 18% and 20% including control specimens for both water-to-cement ratio is considered. Results of compressive strength, split tensile strength and flexural strength showed that the strength properties of concrete mixture decreased marginally with increase in wood ash contents, but strength increased with later age. The XRD test results and chemical analysis of WA showed that it contains amorphous silica and thus can be used as cement replacing material. Through the analysis of results obtained in this study, it was concluded that WA could be blended with cement without adversely affecting the strength properties of concrete. Also using a new statistical theory of the Support Vector Machine (SVM, strength parameters were predicted by developing a suitable model and as a result, the application of soft computing in structural engineering has been successfully presented in this research paper.

Using Cementitious Materials Such as Fly Ash to Replace a Part of Cement in Producing High Strength Concrete in Hot Weather

Science.gov (United States)

Turuallo, Gidion; Mallisa, Harun

2018-03-01

The use of waste materials in concrete gave many advantages to prove the properties of concrete such as its workability, strength and durability; as well to support sustaianable development programs. Fly ash was a waste material produced from coal combustion. This research was conducted to find out the effect of fly ash as a part replacement of cement to produce high strength concrete. The fly ash, which was used in this research, was taken from PLTU Mpanau Palu, Central Sulawesi. The water-binder ratio used in this research was 0.3 selected from trial mixes done before. The results of this research showed that the strength of fly ash concretes were higher than concrete with PCC only. The replacement of cement with fly ash concrete could be up to 20% to produce high strength concrete.

Long-term chloride migration coefficient in slag cement-based concrete and resistivity as an alternative test method

NARCIS (Netherlands)

van Noort, R.; Hunger, M.; Spiesz, P.R.

2016-01-01

This article reports on investigations of the resistivity and chloride migration coefficient (DRCM) obtained in the accelerated Rapid Chloride Migration test for slag cement-based concretes. Determinations of the resistivity and DRCM were performed on 47 different concrete compositions, up to the

Results from five years of treatability studies using hydraulic binders to stabilize low-level mixed waste at the INEL

International Nuclear Information System (INIS)

Gering, K.L.; Schwendiman, G.L.

1997-01-01

This paper summarizes work involving bench-scale solidification of nonincinerable, land disposal restricted low-level mixed waste. Waste forms included liquids, sludges, and solids; treatment techniques included hydraulic systems (Portland cement with and without additives), proprietary commercial formulations, and sulphur polymer cement. Solidification was performed to immobilize hazardous heavy metals (including mercury, lead, chromium, and cadmium), and volatile and semivolatile organic compounds. Pretreatment options for mixed wastes are discussed, using a decision tree based on the form of mixed waste and the type of hazardous constituents. Hundreds of small concrete monoliths were formed for a variety of waste types. The experimental parameters used for the hydraulic concrete systems include the ratio of waste to dry binder (Portland cement, proprietary materials, etc.), the total percentage of water in concrete, and the amount of concrete additives. The only parameter that was used for the sulfur polymer-based monoliths is ratio of waste to binder. Optimum concrete formulations or open-quotes recipesclose quotes for a given type of waste were derived through this study, as based on results from the Toxicity Characteristic Leaching Procedure analyses and a free liquids test. Overall results indicate that high waste loadings in the concrete can be achieved while the monolithic mass maintains excellent resistance to leaching of heavy metals. In our study the waste loadings in the concrete generally fell within the range of 0.5 to 2.0 kg mixed waste per kg dry binder. Likewise, the most favorable amount of water in concrete, which is highly dependent upon the concrete constituents, was determined to be generally within the range of 300 to 330 g/kg (30-33% by weight). The results of this bench-scale study will find applicability at facilities where mixed or hazardous waste solidification is a planned or ongoing activity. 19 refs., 1 fig., 5 tabs

Production and characterization of setting hydraulic cements based on calcium phosphate

International Nuclear Information System (INIS)

Oliveira, Luci C. de; Rigo, Eliana C.S.; Santos, Luis A dos; Boschi, Anselmo Ortega; Carrodeguas, Raul G.

1997-01-01

Setting hydraulic cements based on calcium phosphate has risen great interest in scientific literature during recent years due to their total bio compatibility and to the fact that they harden 'in situ', providing easy handling and adaptation to the shape and dimensions of the defect which requires correction, differently from the predecessors, the calcium phosphate ceramics (Hydroxy apatite, β-tri calcium phosphate, biphasic, etc) in the shape of dense or porous blocks and grains. In the work, three calcium-phosphate cement compositions were studied. The resulting compositions were characterized according to the following aspects: setting times, pH, mechanical resistance, crystalline phases, microstructure and solubility in SBF (Simulated Body Fluid). The results show a potential use for the compositions. (author)

Release of U(VI) from spent biosorbent immobilized in cement concrete blocks

Energy Technology Data Exchange (ETDEWEB)

Venkobachar, C.; Iyengar, L.; Mishra, U.K.; Chauhan, M.S. [Indian Inst. of Tech., Kanpur (India)

1995-12-01

This paper deals with cementation as the method for the disposal of spent biosorbent, Ganoderma lucidum (a wood rotting macrofungi) after it is used for the removal of Uranium. Results on the uranium release during the curing of cement-concrete (CC) blocks indicated that placing the spent sorbent at the center of the blocks during their casting yields better immobilization of uranium as compared to the homogeneous mixing of the spent sorbent with the cement. Short term leach tests indicated that the uranium release was negligible in simulated seawater, 1.8% in 0.2 N sodium carbonate and 6.0% in 0.2 N HCl. The latter two leachates were used to represent the extreme environmental conditions. It was observed that the presence of the spent biosorbent up to 5% by weight did not affect the compressive strength of CC blocks. Thus cementation technique is suitable for the immobilization of uranium loaded biosorbent for its ultimate disposal.

Release of U(VI) from spent biosorbent immobilized in cement concrete blocks

International Nuclear Information System (INIS)

Venkobachar, C.; Iyengar, L.; Mishra, U.K.; Chauhan, M.S.

1995-01-01

This paper deals with cementation as the method for the disposal of spent biosorbent, Ganoderma lucidum (a wood rotting macrofungi) after it is used for the removal of Uranium. Results on the uranium release during the curing of cement-concrete (CC) blocks indicated that placing the spent sorbent at the center of the blocks during their casting yields better immobilization of uranium as compared to the homogeneous mixing of the spent sorbent with the cement. Short term leach tests indicated that the uranium release was negligible in simulated seawater, 1.8% in 0.2 N sodium carbonate and 6.0% in 0.2 N HCl. The latter two leachates were used to represent the extreme environmental conditions. It was observed that the presence of the spent biosorbent up to 5% by weight did not affect the compressive strength of CC blocks. Thus cementation technique is suitable for the immobilization of uranium loaded biosorbent for its ultimate disposal

Modified electrical survey for effective leakage detection at concrete hydraulic facilities

Science.gov (United States)

Lee, Bomi; Oh, Seokhoon

2018-02-01

Three original electrode arrays for the effective leakage detection of concrete hydraulic facilities through electrical resistivity surveys are proposed: 'cross-potential', 'direct-potential' and modified tomography-like arrays. The main differences with respect to the commonly used arrays are that the current line-sources are separated from potential pole lines and floated upon the water. The potential pole lines are located directly next to the facility in order to obtain intuitive data and useful interpretations of the internal conditions of the hydraulic facility. This modified configuration of the array clearly displays the horizontal variation of the electrical field around the damaged zones of the concrete hydraulic facility, and any anomalous regions that might be found between potential poles placed across the facilities. In order to facilitate the interpretation of these modified electrical surveys, a new and creative way of presenting the measurements is also proposed and an inversion approach is provided for the modified tomography-like array. A numerical modeling and two field tests were performed to verify these new arrays and interpretation methods. The cross and direct potential array implied an ability to detect small variations of the potential field near the measurement poles. The proposed array showed the overall potential distribution across the hydraulic facility which may be used to assist in the search of trouble zones within the structure, in combination with the traditional electrical resistivity array.

Determination of coefficient of thermal expansion for Portland Cement Concrete pavements for MEPDG Implementation

Science.gov (United States)

2012-10-01

The Coefficient of Thermal Expansion (CTE) is an important parameter in Portland Cement Concrete (PCC) pavement analysis and design as it is directly proportional to the magnitude of temperature-related pavement deformations throughout the pavement s...

Performance of Waterless Concrete

Science.gov (United States)

Toutanji, Houssam; Evans, Steve; Grugel, Richard N.

2010-01-01

The development of permanent lunar bases is constrained by performance of construction materials and availability of in-situ resources. Concrete seems a suitable construction material for the lunar environment, but water, one of its major components, is an extremely scarce resource on the Moon. This study explores an alternative to hydraulic concrete by replacing the binding mix of concrete (cement and water) with sulfur. Sulfur is a volatile element on the lunar surface that can be extracted from lunar soils by heating. Sulfur concrete mixes were prepared to investigate the effect of extreme environmental conditions on the properties of sulfur concrete. A hypervelocity impact test was conducted, having as its target a 5-cm cubic sample of sulfur concrete. This item consisted of JSC-1 lunar regolith simulant (65%) and sulfur (35%). The sample was placed in the MSFC Impact Test Facility s Micro Light Gas Gun target chamber, and was struck by a 1-mm diameter (1.4e-03 g) aluminum projectile at 5.85 km/s. In addition, HZTERN code, provided by NASA was used to study the effectiveness of sulfur concrete when subjected to space radiation.

Experimental Study on Modification of Concrete with Asphalt Admixture

Science.gov (United States)

Bołtryk, Michał; Małaszkiewicz, Dorota; Pawluczuk, Edyta

2017-10-01

Durability of engineering structures made of cement concrete with high compressive strength is a very vital issue, especially when they are exposed to different aggressive environments and dynamic loads. Concrete resistance to weathering actions and chemical attack can be improved by combined chemical and mechanical modification of concrete microstructure. Asphalt admixture in the form of asphalt paste (AP) was used for chemical modification of cement composite microstructure. Concrete structure was formed using special technology of compaction. A stand for vibro-vibropressing with regulated vibrator force and pressing force was developed. The following properties of the modified concrete were tested: compressive strength, water absorption, freeze-thaw resistance, scaling resistance in the presence of de-icing agents, chloride migration, resistance to CO2 and corrosion in aggressive solutions. Corrosion resistance was tested alternately in 1.8% solutions of NH4Cl, MgSO4, (NH2)2CO and CaCl2, which were altered every 7 days; the experiment lasted 9.5 months. Optimum compaction parameters in semi-industrial conditions were determined: ratio between piston stress (Qp ) and external top vibrator force (Po ) in the range 0.4÷-0.5 external top vibrator force 4 kN. High strength concretes with compressive strength fcm = 60÷70 MPa, very low water absorption (barrier formed in pores of cement hydrates against dioxide and chloride ions. Concrete specimens containing AP 4% c.m. and consolidated by vibro-vibropressing method proved to be practically resistant to highly corrosive environment. Vibro-vibropressing compaction technology of concrete modified with AP can be applied in prefabrication plants to produce elements for road, bridge and hydraulic engineering constructions.

Usage of Crushed Concrete Fines in Decorative Concrete

Science.gov (United States)

Pilipenko, Anton; Bazhenova, Sofia

2017-10-01

The article is devoted to the questions of usage of crushed concrete fines from concrete scrap for the production of high-quality decorative composite materials based on mixed binder. The main problem in the application of crushed concrete in the manufacture of decorative concrete products is extremely low decorative properties of crushed concrete fines itself, as well as concrete products based on them. However, crushed concrete fines could have a positive impact on the structure of the concrete matrix and could improve the environmental and economic characteristics of the concrete products. Dust fraction of crushed concrete fines contains non-hydrated cement grains, which can be opened in screening process due to the low strength of the contact zone between the hydrated and non-hydrated cement. In addition, the screening process could increase activity of the crushed concrete fines, so it can be used as a fine aggregate and filler for concrete mixes. Previous studies have shown that the effect of the usage of the crushed concrete fines is small and does not allow to obtain concrete products with high strength. However, it is possible to improve the efficiency of the crushed concrete fines as a filler due to the complex of measures prior to mixing. Such measures may include a preliminary mechanochemical activation of the binder (cement binder, iron oxide pigment, silica fume and crushed concrete fines), as well as the usage of polycarboxylate superplasticizers. The development of specific surface area of activated crushed concrete fines ensures strong adhesion between grains of binder and filler during the formation of cement stone matrix. The particle size distribution of the crushed concrete fines could achieve the densest structure of cement stone matrix and improve its resistance to environmental effects. The authors examined the mechanisms of structure of concrete products with crushed concrete fines as a filler. The results of studies of the properties of

Study of behavior of concrete and cement based composite materials exposed to high temperatures

OpenAIRE

Bodnárová, L.; Horák, D.; Válek, J.; Hela, R.; Sitek, L. (Libor)

2013-01-01

The paper describes possibilities of observation of behaviour of concrete and cement based composite material exposed to high temperatures. Nowadays, for large-scale tests of behaviour of concrete exposed to high temperatures, testing devices of certified fire testing stations in the Czech Republic and surrounding states are used. These tests are quite expensive. For experimental verification of smaller test specimens, a testing device was built at the Technical University in Brno, wher...

New Medium for Isolation of Bacteria From Cement Kiln Dust with a Potential to Apply in Bio-Concrete

Science.gov (United States)

Alshalif, A. F.; Irwan, J. M.; Othman, N.; Al-Gheethi, A.

2018-04-01

The present study aimed to introduce a new isolation medium named kiln dust medium (KDM) for recovering of bacteria from cement kiln dust with high pH (>pH 11) without the need for nutrients additives. The cement kiln dust samples were collected from five different areas of Cement Industries of Malaysia Berhad (CIMA). The bacterial isolates were recovered on KDM by direct plating technique. The chemical components for all collected samples were identified using X-ray fluorescence (XRF). The primary identification for the bacterial isolates indicated that these bacteria belongs to Bacillus spp. Based on the morphological characteristics. The growth curve of the bacterial strains was monitored using the optical density (OD) with 650 nm wavelength, which in role confirmed that all isolated bacteria had the ability to grow successfully in the proposed medium. The ability of the bacterial strains to grow at high pH reflects their potential in the bio-concrete applications (aerated and non-aerated concrete). These findings indicated that the cement kiln dust samples from Cement Industries represent the most appropriate source for bacteria used in the bioconcrete.

Effect of temperature on structural quality of the cement paste and high-strength concrete with silica fume

International Nuclear Information System (INIS)

Janotka, Ivan; Nuernbergerova, Terezia

2005-01-01

Experimental investigation conducted to study the thermo-mechanical properties of concrete at Temelin (Czech Republic), Mochovce (Slovakia), and Penly (France) nuclear power plants reveals structural integrity degradation between 100 and 200 deg C due to both a loss of water bound in hydrated cement minerals and subsequently air void formation. Test results indicate changes in strength, average pore radius and calculated permeability coefficients for Mochovce specimens exposed to temperatures up to 400 deg C. It demonstrates that the permeability coefficient measured on the basis of pore sizes using mercury intrusion porosimetry is suitable technique for the evaluation of concrete quality. It confirms that strength and permeability coefficient are equivalent structural quality variables of concrete. At 400 deg C gel-like hydration products are decomposed, at 600 deg C Ca(OH) 2 is dehydroxylated, and CaCO 3 dissociation to CaO and CO 2 accompanied with the re-crystallisation of non-binding phases from hydrated cement under re-combustion are dominant processes between 600 and 800 deg C. This stage of concrete is characterised by the collapse of its structural integrity, revealing residual compressive strength. This paper reports high-strength concrete behaviour subjected to temperatures up to 200 deg C. In accordance with previous results, research studies of structure-property relation show the changes in strength, dynamic modulus of elasticity, strain-stress behaviour, and shrinkage-induced deformations influenced by a hydrate phase decomposition. Volume reduction of the hydrate phase due to the loss of bound water mass is the cause of air void formation, and pore structure coarsening. The main attention is herein devoted to the evaluation of utility property decrease of high-strength concrete and microstructure degradation of the cement paste with the same composition than that in concrete when attacked by elevated temperatures

Properties of ambient cured blended alkali activated cement concrete

Science.gov (United States)

Talha Junaid, M.

2017-11-01

This paper presents results of the development and strength properties of ambient-cured alkali activated geopolymer concrete (GPC). The study looks at the strength properties, such as compressive strength, splitting tensile strength, and elastic modulus of such concretes and its dependency on various parameters. The parameters studied in this work are the type and proportions of pre-cursor materials, type of activator and their respective ratios and the curing time. Two types of pre-cursor material; low calcium fly ash (FA) and ground granulated blast furnace slag (GGBFS) were activated using different proportions of sodium silicate and sodium hydroxide solutions. The results indicate that ambient cured geopolymer concrete can be manufactured to match strength properties of ordinary Portland cement concrete (OPC). The strength properties of GPC are dependent on the type and ratio of activator and the proportion of GGBFS used. Increasing the percentage of GGBFS increased the compressive and tensile strengths, while reducing the setting time of the mix. The effect of GGBFS on strength was more pronounced in mixes that contained sodium silicate as activator solution. Unlike OPC, ambient-cured GPC containing sodium silicate gain most of their strength in the first 7 days and there is no change in strength thereafter. However, GPC mixes not containing sodium silicate only achieve a fraction of their strength at 7 days and extended curing is required for such concretes to gain full strength. The results also indicate that the elastic modulus values of GPC mixes without sodium silicate are comparable to OPC while mixes with sodium silicate have elastic modulus values much lower than ordinary concrete.

Results of Laboratory Tests of the Filtration Characteristics of Clay-Cement Concrete

Energy Technology Data Exchange (ETDEWEB)

Sol’skii, S. V., E-mail: solskiysv@vniig.ru; Lopatina, M. G., E-mail: LoptainaMG@vniig.ru; Legina, E. E.; Orishchuk, R. N.; Orlova, N. L. [B. E. Vedeneev All-Russia Research Institute of Hydraulic Engineering (VNIIG) (Russian Federation)

2017-01-15

Laboratory studies of the filtration characteristics of clay-cement concrete materials for constructing filtering diaphragms of earth dams by the method of secant piles are reported. Areas for further study aimed at improving the quality of construction, increasing operational safety, and developing a standards base for the design, construction, and operation of these systems are discussed.

Chloride Diffusion and Acid Resistance of Concrete Containing Zeolite and Tuff as Partial Replacements of Cement and Sand.

Science.gov (United States)

Mohseni, Ehsan; Tang, Waiching; Cui, Hongzhi

2017-03-31

In this paper, the properties of concrete containing zeolite and tuff as partial replacements of cement and sand were studied. The compressive strength, water absorption, chloride ion diffusion and resistance to acid environments of concretes made with zeolite at proportions of 10% and 15% of binder and tuff at ratios of 5%, 10% and 15% of fine aggregate were investigated. The results showed that the compressive strength of samples with zeolite and tuff increased considerably. In general, the concrete strength increased with increasing tuff content, and the strength was further improved when cement was replaced by zeolite. According to the water absorption results, specimens with zeolite showed the lowest water absorption values. With the incorporation of tuff and zeolite, the chloride resistance of specimens was enhanced significantly. In terms of the water absorption and chloride diffusion results, the most favorable replacement of cement and sand was 10% zeolite and 15% tuff, respectively. However, the resistance to acid attack reduced due to the absorbing characteristic and calcareous nature of the tuff.

Behavior of Plain Concrete of a High Water-Cement Ratio after Freeze-Thaw Cycles

OpenAIRE

Shang, Huai-Shuai; Yi, Ting-Hua; Song, Yu-Pu

2012-01-01

An experimental study of plain concrete specimens of water-cement ratio 0.55, subjected to 0, 15, 25, 40, 50 and 75 cycles of freeze-thaw was completed. The dynamic modulus of elasticity (DME), weight loss, compressive strength, tensile strength, flexural strength, cleavage strength and stress-strain relationships of plain concrete specimens suffering from freeze-thaw cycles were measured. The experimental results showed that the strength decreased as the freeze-thaw cycles were repeated. A c...

Some Guides to Discovery About Elm Trees, Owls, Cockroaches, Earthworms, Cement and Concrete.

Science.gov (United States)

Busch, Phyllis S.

The introduction emphasizes the need for environmental and conservation education, and advocates an inquiry approach. Outdoor resources available to every school are listed. Detailed suggestions are made for investigating cement and concrete, cockroaches, earthworms, elm trees, and owls. In each case general background information and a list of…

Determination of Temperature Rise and Temperature Differentials of CEMII/B-V Cement for 20MPa Mass Concrete using Adiabatic Temperature Rise Data

Science.gov (United States)

Chee Siang, GO

2017-07-01

Experimental test was carried out to determine the temperature rise characteristics of Portland-Fly-Ash Cement (CEM II/B-V, 42.5N) of Blaine fineness 418.6m2/kg and 444.6m2/kg respectively for 20MPa mass concrete under adiabatic condition. The estimation on adiabatic temperature rise by way of CIRIA C660 method (Construction Industry Research & Information Information) was adopted to verify and validate the hot-box test results by simulating the heat generation curve of the concrete under semi-adiabatic condition. Test result found that Portland fly-ash cement has exhibited decrease in the peak value of temperature rise and maximum temperature rise rate. The result showed that the temperature development and distribution profile, which is directly contributed from the heat of hydration of cement with time, is affected by the insulation, initial placing temperature, geometry and size of concrete mass. The mock up data showing the measured temperature differential is significantly lower than the technical specifications 20°C temperature differential requirement and the 27.7°C limiting temperature differential for granite aggregate concrete as stipulated in BS8110-2: 1985. The concrete strength test result revealed that the 28 days cubes compressive strength was above the stipulated 20MPa characteristic strength at 90 days. The test demonstrated that with proper concrete mix design, the use of Portland flyash cement, combination of chilled water and flake ice, and good insulation is effective in reducing peak temperature rise, temperature differential, and lower adiabatic temperature rise for mass concrete pours. As far as the determined adiabatic temperature rise result was concern, the established result could be inferred for in-situ thermal properties of 20MPa mass concrete application, as the result could be repeatable on account of similar type of constituent materials and concrete mix design adopted for permanent works at project site.

Concretes with ternary composite cements. Part III: multicriteria optimization

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Irassar, E. F.

2007-06-01

Full Text Available Optimization methods are tools of vital importance in composite material design, where large numbers of components and design criteria must be taken into account. The formulation of today’s separately milled custommade cements is a clear example of just such a case, for the components must be proportioned to yield mortars and concretes with the proper balance of durability, strength, financial and environmental features. Multicriteria optimization has been used to develop many materials, although its application in cement formulation has yet to be explored. The present paper discusses the use of an objective function to jointly optimize sorptivity and compressive strength in limestone- (up to 20% and/or granulated blast furnace slag- (up to 20% additioned Portland cement concrete.Los métodos de optimización constituyen una herramienta de vital importancia en el diseño de materiales compuestos, donde la cantidad de componentes de la mezcla y los criterios de diseño que deben tenerse en cuenta en el proceso de fabricación son numerosos. En la actualidad, la formulación de un cemento a medida (tailor made a partir del proceso de molienda separada es un claro ejemplo de ello, pues las proporciones relativas de las componentes de la mezcla deben permitir luego obtener morteros y hormigones con el equilibrio justo entre los requerimientos durables, mecánicos, económicos y ecológicos que se soliciten. La optimización por multicriterios ha sido empleada en el desarrollo de diversos materiales, sin embargo, su aplicación en la formulación del cemento no ha sido aún explorada. En este trabajo se presenta la optimización conjunta de la capacidad de absorción y la resistencia a compresión de hormigones elaborados con cemento Portland con caliza (hasta un 20% y/o escoria granulada de alto horno (hasta un 20% utilizando la función objetivo.

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

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Othuman Mydin M.A.

2014-01-01

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

Optimization of mix design by using superplasticized cement

International Nuclear Information System (INIS)

Khaskheli, G.B.; Kumar, A.; Umrani, A.N.

2009-01-01

Superplasticizers are high range water reducers which are capable of producing high-strength concrete with low permeability. Recently a cement factory in Sindh has launched SPC (Superplasticized Cement) which contains the required amount of superplasticizers. It is needed to investigate its performance compared to that of OPC (Ordinal-Y Portland Cement). This study is framed to optimize various strengths of structural concrete through the use of SPC of the cement factory. In total 288 cubes (6x6x6) were cast and tested for four different compressive strength of concrete (8000, 6000, 5000 and 4000 psi) manufactured with two brands of cement (OPC and SPC) of the cement factory and two different coarse aggregate sizes (40 and 20 mm) at three different curing ages (7,14 and 28 days). The effect on compressive strength of structural concrete was also observed by adopting 5 and 10% reduction in cement content of the superplasticized cement. Results have indicated that structural concrete made with superplasticized cement could give higher compressive strength than that of OPC at all the curing ages, and 10% saving in cement content could be achieved by using superplasticized cement. Structural concrete made with superplasticized cement could attain higher strength in a shorter period of time, and workability of structural concrete could be increased by using SPC. (author)

In situ test plan for concrete materials using low alkaline cement at Horonobe URL

International Nuclear Information System (INIS)

Kobayashi, Yasushi; Yamada, Tsutomu; Nakayama, Masashi; Matsui, Hiroya; Matsuda, Takeshi; Konishi, Kazuhiro; Iriya, Keishiro; Noda, Masaru

2007-03-01

HLW (high-level radioactive waste) repository is to be constructed at depths of over three hundred meters below the surface. Shotcrete and lining will be used for safety under construction and operational period. Concrete is a kind of composite material which is constituted by aggregate, cement and additives. Low alkaline cement has been developed from the viewpoint of long term stability of the barrier systems which would be influenced by high alkaline arising from cement material. HFSC (Highly Fly-ash contained Silica-fume Cement) is one of a low alkaline cement, which contains silica fume and coal ash. It has been developed in Japan Atomic Energy Agency (JAEA). JAEA are now implementing the construction of the under ground research laboratory (URL) at Horonobe for the purpose of research in deep geological science and repository engineering technology. This report shows the in situ test plan for shotcrete using HFSC at Horonobe URL with identifying requirements for cement materials to be used in HLW repository, and also reviews major literatures of low alkaline cement. This in situ test plan is aiming to assess the performance of HFSC shotcrete in terms of mechanics, workability, durability, and so on. (author)

Some Mechanical Properties of Concrete by using Manufactured Blended Cement with Grinded Local Rocks

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Zena K. Abbas Al-Anbori

2016-03-01

Full Text Available he use of blended cement in concrete provides economic, energy savings, and ecological benefits, and also provides. Improvement in the properties of materials incorporating blended cements. The major aim of this investigation is to develop blended cement technology using grinded local rocks . The research includes information on constituent materials, manufacturing processes and performance characteristics of blended cements made with replacement (10 and 20 % of grinded local rocks (limestone, quartzite and porcelinite from cement. The main conclusion of this study was that all types of manufactured blended cement conformed to the specification according to ASTM C595-12 (chemical and physical requirements. The percentage of the compressive strength for blended cement with 10% replacement are (20, 11 and 5 % , (2 , 12 and, 13 % and (18, 15 and 16 % for limestone , quartzite and porcelinite respectively at (7,28 and 90days for each compare to the reference mix, while blended cement with 20% replacement are (-3, -5 and -11 ,(6, -4% and -5 and (6, 4 and 6 % for limestone , quartzite and porcelinite respectively at (7, 28 and 90days compare to the reference mix .The other mechanical properties (flexural tensile strength and splitting tensile strength are the same phenomena of increase and decrease in compressive strength. The results indicated that the manufacture Portland-limestone cement, Portland-quartzite cement and Portland-porcelinite cement with 10% replacement of cement with improvable mechanical properties while the manufacture Portland-porcelinite cement with 20% replacement of cement with slight improvable mechanical properties and more economical cost.

Hydration kinetics of cement composites with varying water-cement ratio using terahertz spectroscopy

Science.gov (United States)

Ray, Shaumik; Dash, Jyotirmayee; Devi, Nirmala; Sasmal, Saptarshi; Pesala, Bala

2015-03-01

Cement is mixed with water in an optimum ratio to form concrete with desirable mechanical strength and durability. The ability to track the consumption of major cement constituents, viz., Tri- and Dicalcium Silicates (C3S, C2S) reacting with water along with the formation of key hydration products, viz., Calcium-Silicate-Hydrate (C-S-H) which gives the overall strength to the concrete and Calcium Hydroxide (Ca(OH)2), a hydration product which reduces the strength and durability, using an efficient technique is highly desirable. Optimizing the amount of water to be mixed with cement is one of the main parameters which determine the strength of concrete. In this work, THz spectroscopy has been employed to track the variation in hydration kinetics for concrete samples with different water-cement ratios, viz., 0.3, 0.4, 0.5 and 0.6. Results show that for the sample with water-cement ratio of 0.3, significant amount of the C3S and C2S remain unreacted even after the initial hydration period of 28 days while for the cement with water-cement ratio of 0.6, most of the constituents get consumed during this stage. Analysis of the formation of Ca(OH)2 has been done which shows that the concrete sample with water-cement ratio of 0.6 produces the highest amount of Ca(OH)2 due to higher consumption of C3S/C2S in presence of excess water which is not desirable. Samples with water-cement ratio of 0.4 and 0.5 show more controlled reaction during the hydration which can imply formation of an optimized level of desired hydration products resulting in a more mechanically strong and durable concrete.

SELF-HEALING CAPACITY OF CONCRETE - COMPUTER SIMULATION STUDY OF UNHYDRATED CEMENT STRUCTURE

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Huan He

2011-05-01

Full Text Available Aggregate occupies at least three-quarters of the volume of concrete, so its impact on concrete's properties is large. The aggregate's influence on the non-hydrated part of the matured paste is assessed by concurrent algorithm-based computer simulation system SPACE in this paper. A distinction is made between interfacial zones (ITZs and bulk paste. Containers with rigid boundaries were employed for the production of series of cement pastes. They were subjected to quantitative microstructure analysis. Relevant gradient structures in the ITZ and bulk are presented and discussed. The relevance of this structure information for possible selfhealing of cracks is briefly discussed.

Manufacturing of concrete with residues from iron ore exploitation using the technology of radioactive waste cementation

Energy Technology Data Exchange (ETDEWEB)

Versieux, Juniara L.; Lameiras, Fernando S.; Tello, Cledola Cassia Oliveira de, E-mail: juniarani@gmail.com, E-mail: fsl@cdtn.br, E-mail: tellocc@cdtn.br [Centro de Desenvolvimento da Tecnologia Nucelar (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil)

2015-07-01

Radioactive wastes from various segments of economy are immobilized by cementation, because of availability and widespread use in civil construction of cement. New cementitious materials are developed in CDTN using mining residues based on cementing techniques of radioactive wastes. Special procedures were developed to obtain concrete with the use of super plasticizers in which natural sand was totally replaced by mining residues. The motivation for this research is the exploration of banded iron formations (BIF) as iron ore in 'Quadrilatero Ferrifero' of Minas Gerais, where huge amounts of residues are generated with great concern about the environmental sustainability and safety of dams for residue storage. The exploitation of river sand causes many negative impacts, which leads to interest in its replacement by another raw material in mortar and concrete manufacturing. The use of BIF mining residues were studied for manufacturing of concrete pavers to contribute to reducing the impact caused by extraction of natural sand and use of mining residues. Previously developed procedures with total replacement of natural sand for mining residues were modified, including use of gravel to obtain pavers with improved properties. Four different mixtures were tested, in which the proportion of gravel and super plasticizer was varied. Monitored properties of pavers, among others, were compression resistance, water absorption, and void volume. With addition of gravel, the pavers had higher void index than those made only with mortar, and higher resistance to compression after 28 days of curing (an average of 18MPa of those made with mortar to 24MPa of those made with concrete). (author)

Manufacturing of concrete with residues from iron ore exploitation using the technology of radioactive waste cementation

International Nuclear Information System (INIS)

Versieux, Juniara L.; Lameiras, Fernando S.; Tello, Cledola Cassia Oliveira de

2015-01-01

Radioactive wastes from various segments of economy are immobilized by cementation, because of availability and widespread use in civil construction of cement. New cementitious materials are developed in CDTN using mining residues based on cementing techniques of radioactive wastes. Special procedures were developed to obtain concrete with the use of super plasticizers in which natural sand was totally replaced by mining residues. The motivation for this research is the exploration of banded iron formations (BIF) as iron ore in 'Quadrilatero Ferrifero' of Minas Gerais, where huge amounts of residues are generated with great concern about the environmental sustainability and safety of dams for residue storage. The exploitation of river sand causes many negative impacts, which leads to interest in its replacement by another raw material in mortar and concrete manufacturing. The use of BIF mining residues were studied for manufacturing of concrete pavers to contribute to reducing the impact caused by extraction of natural sand and use of mining residues. Previously developed procedures with total replacement of natural sand for mining residues were modified, including use of gravel to obtain pavers with improved properties. Four different mixtures were tested, in which the proportion of gravel and super plasticizer was varied. Monitored properties of pavers, among others, were compression resistance, water absorption, and void volume. With addition of gravel, the pavers had higher void index than those made only with mortar, and higher resistance to compression after 28 days of curing (an average of 18MPa of those made with mortar to 24MPa of those made with concrete). (author)

Determination of permeability to gases of concrete used as repository for radioactive wastes; Determinacao da permeabilidade a gas em concreto usado em repositorios para rejeitos radioativos

Energy Technology Data Exchange (ETDEWEB)

Miyake, Eloisa Tamie

1994-12-31

Concrete is widely used in final radioactive waste repository construction and must have well defined characteristics. The permeability is a property that allows to evaluate the durability of concrete which guarantee the protection of the surroundings. Durable concretes have low permeability which reduces liquids intrusion into the repository and decreases the probability of leaching of soluble radioactive compounds and gases escapes to the human habitat. This work includes: the construction of a camera to measure the permeability coefficient of hydraulic products, by using gaseous nitrogen as a permeation fluid; determination of characteristics of material used in concrete compositions; and tests in concretes with different compositions in which ordinary Portland cement and blast-furnace cement were used. (author). 61 refs., 33 figs., 16 tabs.

Cementation of Nuclear Graphite Using Geopolymers

International Nuclear Information System (INIS)

Girke, N.A.; Steinmetz, H-J.; Bukaemsky, A.; Bosbach, D.; Hermann, E.; Griebel, I.

2016-01-01

Geopolymers are solid aluminosilicate materials usually formed by alkali hydroxide or alkali silicate activation of solid precursors such as coal fly ash, calcined clay and/or metallurgical slag. Today the primary application of geopolymer technology is in the development of alternatives to Portland-based cements. Variations in the ratio of aluminium to silicon, and alkali to silicon or addition of structure support, produce geopolymers with different physical and mechanical properties. These materials have an amorphous three-dimensional structure that gives geopolymers certain properties, such as fire and acid resistance, low leach rate, which make them an ideal substitute for ordinary Portland cement (OPC) in a wide range of applications especially in conditioning and storage of radioactive waste. Therefore investigations have been initiated on how and to which amount graphite as a hydrophobic material can be mixed with cement or concrete to form stable waste products and which concretes fulfil the necessary specifications best. As a result, geopolymers have been identified as a promising matrix for graphite containing nuclear wastes. With geopolymers, both favourable properties in the cementation process and a high long time structural stability of the products can be achieved. Investigations include: • direct mixing of graphite with geopolymers with or without sand as a mechanically stabilizing medium; • production of cement-graphite granulates as intermediate products and embedding of these granulates in geopolymer; • coating of formed graphite pieces with geopolymer.The report shows that carbon in the form of graphite can both be integrated with different grain size spectra as well as shaped in the hydraulic binder geopolymer and meets the requirements for a stable long-term immobilisation. (author)

Sand Cement Brick Containing Recycled Concrete Aggregate as Fine-Aggregate Replacement

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Sheikh Khalid Faisal

2017-01-01

Full Text Available Nowadays, the usage amount of the concrete is increasing drastically. The construction industry is a huge consumer of natural consumer. It is also producing the huge wastage products. The usage of concrete has been charged to be not environmentally friendly due to depletion of reserve natural resources, high energy consumption and disposal issues. The conservation of natural resources and reduction of disposal site by reuse and recycling waste material was interest possibilites. The aim of this study is to determine the physical and mechanical properties of sand cement brick containing recycled concrete aggregate and to determine the optimum mix ratio containing recycled concrete aggregate. An experiment done by comparing the result of control specimen using 100% natural sand with recycled concrete aggregate replacement specimen by weight for 55%, 65%, and 75%. The sample was tested under density, compressive strength, flexural strength and water absorption to study the effect of using recycled concrete aggregate on the physical and mechanical properties of bricks. The result shows that the replacement of natural sand by recycled concrete aggregate at the level of 55% provide the highest compressive and flexural strength compared to other percentage and control specimen. However, if the replacement higher than 55%, the strength of brick was decreased for compressive and flexural strength, respectively. The relationship of compressive-flexural strength is determined from statistical analysis and the predicted result can be obtained by using equation ff,RCA = 0.5375 (fc0.3272.

Compressive strength of concrete by partial replacement of cement with metakaolin

Science.gov (United States)

Ganesh, Y. S. V.; Durgaiyya, P.; Shivanarayana, Ch.; Prasad, D. S. V.

2017-07-01

Metakaolin or calcined kaolin, other type of pozzolan, produced by calcination has the capability to replace silica fume as an alternative material. Supplementary cementitious materials have been widely used all over the world in concrete due to their economic and environmental benefits; hence, they have drawn much attention in recent years. Mineral admixtures such as fly ash, rice husk ash, silica fume etc. are more commonly used SCMs. They help in obtaining both higher performance and economy. Metakaolin is also one of such non - conventional material, which can be utilized beneficially in the construction industry. This paper presents the results of an experimental investigations carried out to find the suitability of metakaolin in production of concrete. In the present work, the results of a study carried out to investigate the effects of Metakaolin on compressive strength of concrete are presented. The referral concrete M30 was made using 43 grade OPC and the other mixes were prepared by replacing part of OPC with Metakaolin. The replacement levels were 5%, 10%, 15% and 20%(by weight) for Metakaolin. The various results, which indicate the effect of replacement of cement by metakalion on concrete, are presented in this paper to draw useful conclusions.

POROUS STRUCTURE OF ROAD CONCRETE

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M. K. Pshembaev

2016-01-01

Full Text Available Having a great number of concrete structure classifications it is recommended to specify the following three principal types: microstructure – cement stone structure; mesostructure – structure of cement-sand mortar in concrete; macrostucture – two-component system that consists of mortar and coarse aggregate. Every mentioned-above structure has its own specific features which are related to the conditions of their formation. Thus, microstructure of cement stone can be characterized by such structural components as crystal intergrowth, tobermorite gel, incompletely hydrated cement grains and porous space. The most important technological factors that influence on formation of cement stone microstructure are chemical and mineralogical cement composition, its grinding fineness, water-cement ratio and curing condition. Specific cement stone microstructure is formed due to interrelation of these factors. Cement stone is a capillary-porous body that consists of various solid phases represented predominantly by sub-microcrystals of colloidal dispersion. The sub-microcrystals are able adsorptively, osmotically and structurally to withhold (to bind some amount of moisture. Protection of road concrete as a capillary-porous body is considered as one of the topical issues. The problem is solved with the help of primary and secondary protection methods. Methods of primary protection are used at the stage of designing, preparation and placing of concrete. Methods of secondary protection are applied at the operational stage of road concrete pavement. The paper considers structures of concrete solid phase and characteristics of its porous space. Causes of pore initiation, their shapes, dimensions and arrangement in the concrete are presented in the paper. The highest hazard for road concrete lies in penetration of aggressive liquid in it and moisture transfer in the cured concrete. Water permeability of concrete characterizes its filtration factor which

Reinforcing of Cement Composites by Estabragh Fibres

Science.gov (United States)

Merati, A. A.

2014-04-01

The influence of Estabragh fibres has been studied to improve the performance characteristics of the reinforced cement composites. The concrete shrinkage was evaluated by counting the number of cracks and measuring the width of cracks on the surface of concrete specimens. Although, the Estabragh fibres lose their strength in an alkali environment of cement composites, but, the ability of Estabragh fibres to bridge on the micro cracks in the concrete matrix causes to decrease the width of the cracks on the surface of the concrete samples in comparison with the plain concrete. However, considering the mechanical properties of specimens such as bending strength and impact resistance, the specimens with 0.25 % of Estabragh fibre performed better in all respects compared to the physical and mechanical properties of reinforced cement composite of concrete. Consequently, by adding 0.25 % of Estabragh fibres to the cement composite of concrete, a remarkable improvement in physical and mechanical properties of fibre-containing cement composite is achieved.

Cast in place temperature 5 influence on fresh concrete made with limestone filler and blended cement

Directory of Open Access Journals (Sweden)

Soria, E. A.

2003-12-01

Full Text Available Properties of fresh concrete play a relevant role on placing and consolidation; and its design strength and durability depends on them. It is well known too that the concrete temperature during placing affects all its properties in different ways and extent. This paper presents the influence of placing temperature of concretes made with portland cement, limestone filer cement and blended cement, commercially available, on slump, slump loss, setting time and bleeding. The results show that generally when concrete temperature rises, the bleeding and slump fall down and the slump loss and setting time are accelerated. However, regardless of the strength class the type of cement affects the value of these variations

Las propiedades de los hormigones en estado fresco desempeñan un papel fundamental durante las operaciones de colocación y compactación de los mismos y de ellas depende, en gran medida, que se alcance en el estado endurecido la resistencia y la durabilidad de diseño. Es sabido, además, que la temperatura que alcanza un hormigón durante dichas operaciones, afecta en mayor o menor grado a todas sus propiedades, de manera diferente. En el presente trabajo se analizó la influencia de la temperatura de colocación sobre el asentamiento, la pérdida del asentamiento en el tiempo, los tiempos de fraguado y la exudación, en hormigones elaborados con cemento portland normal, fillerizado y compuesto, de procedencia comercial. Los resultados han mostrado, en general, que con el aumento de la temperatura de colocación disminuyen la exudación y el asentamiento; mientras que la pérdida de asentamiento y los tiempos de fraguado se aceleran. Sin embargo, las magnitudes de dichas variaciones resultan a su vez muy influenciadas por el tipo de cemento utilizado, aun siendo de la misma clase resistente.

3.7. Technical and economic aspects of the application of cement concretes obtained from local minerals

International Nuclear Information System (INIS)

Saidov, D.Kh.

2011-01-01

This article is devoted to technical and economic aspects of the application of cement concretes obtained from local minerals. The following composite materials obtained from local raw materials were considered: mineral (cement, lime), inorganic (phosphates, sodium silicate), organic (phenol formaldehyde, epoxide, urea-formaldehyde, carbamide, acryl, organosilicon, furfural aniline). It was concluded that from technical and economical points of view the most effective materials were: mineral composite materials, crude shale oils and ligno sulphonates.

Performance of geopolymer concrete in fire

OpenAIRE

Zhao, Ren

2017-01-01

Portland cement concrete is a world-wide used construction material. However, when Portland cement concrete is exposed to fire, its mechanical properties are deteriorated. The deterioration of concrete is generally caused by the decomposition of the Portland cement hydrate or the thermal incompatibility between cement paste and aggregate. Spalling, which is a violent or non-violent breaking off of layers or pieces of concrete from the surface of a structural element, may also occur when the c...

Ultrafine particles in concrete: Influence of ultrafine particles on concrete properties and application to concrete mix design

Energy Technology Data Exchange (ETDEWEB)

Vogt, Carsten

2010-07-01

In this work, the influence of ultrafine particles on concrete properties was investigated. In the context of this work, ultrafine particles (reactive and inert materials) are particles finer than cement. Due to the development of effective superplasticizers, the incorporation of ultrafine particles in concrete is nowadays possible. Different minerals, usually considered inert, were tested. These minerals were also used in combination with reactive silica fume. The modified Andreassen model was used to optimise the particle size distribution and thus the packing density of the complete mix composition. Heat of hydration, compressive strength, shrinkage, frost resistance and the microstructure were investigated.The influence of different ultrafine inert materials on the cement hydration was investigated. The results show that most of the minerals have an accelerating effect. They provide nucleation sites for hydration products and contribute in that way to a faster dissolution of cement grains. Minerals containing calcium were found to influence the early stage of hydration as well. These minerals shortened the dormant period of the cement hydration, the effect is known from limestone filler in self-compacting concrete. In a first test series on concrete, different ultrafine inert particles were used to replace cement. That was done in several ways; with constant water content or constant w/c. The results from this test series show that the best effect is achieved when cement is replaced by suitable ultrafines while the w/c is kept constant. In doing so, the compressive strength can be increased and shrinkage can be reduced. The microstructure is improved and becomes denser with improved packing at microlevel. Efficiency factors (k values) for the ultrafine inert materials were calculated from the compressive strength results. The k values are strongly dependent on the mode of cement replacement, fineness and type of the replacement material and curing time. Drying

Performance Evaluation and Field Application of Porous Vegetation Concrete Made with By-Product Materials for Ecological Restoration Projects

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Hwang-Hee Kim

2016-03-01

Full Text Available The purpose of this study was to evaluate the performance of porous vegetation concrete block made from blast furnace slag cement containing industrial by-products such as blast furnace slag aggregate and powder. The blocks were tested for void ratio, compressive strength and freeze-thaw resistance to determine the optimal mixing ratio for the porous vegetation block. An economic analysis of the mixing ratio showed that the economic efficiency increased when blast furnace slag aggregate and cement were used. Porous vegetation concrete blocks for river applications were designed and produced. Hydraulic safety, heavy metal elution and vegetation tests were completed after the blocks were applied in the field. The measured tractive force ranged between 7.0 kg/m2 for fascine revetment (vegetation revetment and 16.0 kg/m2 for stone pitching (hard revetment, which ensured sufficient hydraulic stability in the field. Plant growth was measured after the porous vegetation concrete block was placed in the field. Seeds began to sprout one week after seeding; after six weeks, the plant length exceeded 300 mm. The average coverage ratio reached as high as 90% after six weeks of vegetation. These results clearly indicated that the porous vegetation concrete block was suitable for environmental restoration projects.

LIGHTWEIGHT CONCRETE BASED GRANSHLAK

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NETESA M. I.

2016-02-01

Full Text Available Raising of problem. Concrete advisable to obtain a low strength with local secondary resources for recycling and reduce the environmental burden on the environment. But it is important to design such concrete compositions with a reduced flow of cement. It is known that the coefficient of efficiency of use of cement in the concrete of the heavy and B10 is less than about 0.5, which is almost two times smaller than in class B15 concrete and above. Even lower coefficient of efficiency in light concrete cement low strength. Therefore, it is important to find patterns determining the composition of lightweight concrete based on local-products industry with more efficient use of cement in them. Purpose.. Based on the analysis of earlier research results, including with the use of methods of mathematical planning of experiments to determine the concrete contents, which can provide the requirements for the underlying layers of the floor, the compressive strength of which should correspond to the class B5. It is important to provide the required strength at minimum flow of the cement, which is the most expensive and energy-intensive part of concrete. Conclusion. Analysis of the test results of control samples of concrete in 28-day-old, the following laws. The required tensile strength of concrete compressive strength of 7.0 MPa can be obtained in the test range when used in formulations as a filler as the Dnieper hydroelectric power station fly ash and tailings Krivoy Rog iron ore YuGOK. To ensure providing the required characteristic strength of the concrete in the underlying layers of the floor is advisable to use a nominal composition per cubic meter of concrete: cement 160 kg granshlaka Plant named after Petrovsky, 675 kg of fly ash Dnieper HPP 390 kg, 400 kg of sand, 230 liters of water. Thus, while ensuring rational grain composition components can obtain the desired strength lightweight concrete based granshlaka plant Petrovsky, using as fillers

Early age volume changes in concrete due to chemical shrinkage of cement paste

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Ebensperger, L.

1991-12-01

Full Text Available Unrestrained early age volume changes due to chemical shrinkage in cement pastes, mortars and concretes have been determined. The measurements were performed on sealed and unsealed samples which were stored under water. The chemical shrinkage of unsealed specimens represents the amount of absorbed water due to the chemical reaction of the cement It depends only on the cement content of the sample and does not lead to changes of the external dimensions. However the chemical shrinkage of sealed specimens is connected with a real volume change due to self-desiccation and the effect of internal pressures. The shrinkage depends in this case on the restraining effect of coarse aggregates as well as the cement content. The chemical shrinkage measured on sealed concretes was much higher than the one expected to ocurr on concretes, because normally an equalization of pressure takes place to some extent in the interior of the concrete. The use of expansive additives showed that they may compensate the chemical shrinkage, but its dosage is very sensitive and should be defined exactly for each case particularly.

Se han determinado los cambios volumétricos que ocurren en pastas de cemento, morteros y hormigones a edad temprana debido al efecto de la retracción química. Las mediciones se realizaron en probetas selladas y no selladas sumergidas bajo agua. La retracción química en probetas no selladas representa la cantidad de agua absorbida debido a la reacción química del cemento. Depende solamente del contenido de cemento de la probeta y no produce ningún cambio en las dimensiones de la probeta. Por el contrario, la retracción química en probetas selladas está relacionada con un cambio volumétrico real debido al efecto de la autodesecación y presiones internas. La retracción en este caso depende tanto de la restricción que imponen los áridos, como del contenido de cemento. La retracción química medida en hormigones sellados

Durability of concrete: characterization and modeling of physical and chemical degradation of cement

International Nuclear Information System (INIS)

Adenot, Frederic

1992-01-01

Within the frame of nuclear waste management, and more particularly waste storage by confinement in parcels, concrete and geological environment, this research aims at predicting the durability of a concrete paste and of all concrete works. This prediction is based on a material characterization (determination of the thickness and composition of the attacked area) whatever the degradation duration is. The adopted approach is to model concrete lixiviation and to compare model results with experimental results. The model is also used to assess the influence of a great number of parameters, and to simulate non experimented cases. Thus, the author reports a bibliographical study on cement, and presents the equations of a lixiviation model. He reports experiments aimed at verifying modelling hypotheses and at acquiring necessary data. The model is then numerically solved, and applied to an experimental case. Experimental results are compared with modelling results, and a prediction is performed for a 300 year-duration [fr

Innovation based on tradition : Blast furnace slag cement for durable concrete structures in Norway?

NARCIS (Netherlands)

Polder, R.B.; Nijland, T.; De Rooij, M.; Larsen, C.K.; Pedersen, B.

2014-01-01

Blast furnace slag cement (BFSC) has been used to build reinforced concrete structures in marine and road environment in The Netherlands for nearly a century. The experience is good and structures with long service lives can be obtained, as has been shown by several field studies. This is caused by

Content of heavy metals and chemical composition of the hydraulic cement marketed in Costa Rica

International Nuclear Information System (INIS)

Venegas Padilla, Jimmy; Calderon Jimenez, Bryan; Sibaja Brenes, Jose Pablo; Salazar Delgado, Jorge; Rodriguez Castro, Ellen

2017-01-01

The concentration of heavy metals, specifically lead (Pb), chromium (Cr), and mercury (Hg), and also the chemical composition (CaO, SiO 2 , Al 2 O 3 , Fe 2 O 3 among others) were quantified of the hydraulic cement marketed in Costa Rica. The physical parameters of density and fineness confirmed the homogeneity of the samples to determinate accurately the content of the major components and heavy metals in the cements. The mineralogical constitution was determined by X-ray Fluorescence (XRF). Specifically, the cements showed a mass fraction in the range of (61.22 - 63.12) % of CaO, (18.10 - 26.14) % of SiO 2 , (3.70 - 6.05) % of Al 2 O 3 , (2.57 - 3.36) % Fe 2 O 3 and (0.60 - 4.09) % de MgO. Other components such as MgO, TiO 2 , K 2 O, P 2 O 5 , Na 2 O and Mn 2 O 3 were found on an average mass fraction lower than 1%. Moreover, using the ignition test results and assuming a complete decomposition of the limestone, it was possible to estimate (indirectly) the content of CaCO 3 and CaO given by the raw materials. The metal content of the heavy metals was determined using Flame Atomic Absorption Spectroscopy (FAAS), Electrothermal Atomic Absorption Spectroscopy (ETAAS), and Cold Vapor Atomic Absorption Spectroscopy (CVAAS). The analysis demonstrated that the Pb in cements is present in different concentrations ranging the (2.45 ± 0.72) mg kg -1 to the (8.95 ± 1.34) mg kg -1 . Chromium (Cr) was presented in higher concentrations of (10.69 ± 0.92) mg kg-1. The Hg concentration was below 0.141 ± 0.021 mg kg -1 . In general terms, the hydraulic cements marketed and used in Costa Rica have a suitable chemical composition compared with some cements marketed in Germany. The results of the content of heavy metals presented in this study provide significant information for future studies in the area of toxicology, ecotoxicology, standardization and national regulation. (author) [es

Effect of heat treatment upon the mechanical and poro-mechanical behaviour of cement-based materials: hydraulic properties and morphological changes

International Nuclear Information System (INIS)

Chen, Xiao-Ting

2009-01-01

This work investigates the effects of morphological changes of a cement-based material subjected to heat treatment (up to 400 C). For a model W/C=0.5 mortar, we have characterized experimentally hydraulic behaviour (gas permeability), mechanical behaviour (in uniaxial compression, hydrostatic compression with or without deviatoric stress) and poro-mechanical behaviour (incompressibility moduli Kb, Ks and Biot's coefficient b) after a heating/cooling cycle. We have also developed an original experiment aimed at quantifying the accessible pore space volume under hydrostatic compression. The creation of occluded porosity under high confinement is confirmed, which justifies the observed decrease of solid matrix rigidity Ks under high confinement. A gas retention phenomenon was identified under simultaneous thermal and hydrostatic loadings for mortar, and industrial concretes (provided by CERIB and ANDRA). A predictive thermo-elasto-plastic model with isotropic damage and a micro-mechanical approach, which represents micro-cracking, are coupled in order to analyze or predict the evolution of mechanical and poro-elastic properties after heat cycling. (author)

Barium aluminate cement: its application

International Nuclear Information System (INIS)

Drozdz, M.; Wolek, W.

1975-01-01

The technology of manufacturing barium aluminate cement from barium sulfate and alumina, using a rotary kiln for firing the clinker is described. The method of granulation of the homogenized charge was used. Conditions of using the ''to mud'' method in industry were indicated. The physical and chemical properties of barium aluminate cement are determined and the quality of several batches of cement prepared on a semi-industrial scale and their suitability for making highly refractory concretes are tested. The optimal composition of the concretes is determined as a function of the mixing water and barium aluminate cement contents. Several experimental batches of concretes were used in the linings of furnaces in the steel industry. The suitability of these cements for use in fields other than steelmaking is examined. It is established that calcium aluminate cement has certain limited applications [fr

Wet versus dry cement pastes and concretes: a mathematical approach to their strength and fracture properties

International Nuclear Information System (INIS)

Suarez Antola, R.

2006-12-01

The fracture process of a continuous matrix in a porous medium under the combined effect of filtration and external mechanical loads is considered. Taking into account the differences between the failure mechanisms of cement paste under tension and its failure mechanisms under compression, an analytical approach to the relation between water flow and fracture in saturated porous Portland cement pastes is developed. The well known differences in behaviour between the flexural and compressive strengths of wet and dry Portland cement pastes is explained. The extension of the obtained results to the flexural and compressive strength of normal concrete is briefly discussed, including suggestions for further experimental and digital simulation work

Self-healing of polymer modified concrete

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Abd_Elmoaty M. Abd_Elmoaty

2011-06-01

Full Text Available Self healing phenomenon of concrete has been observed in traditional, fibrous, self compacting concrete. This phenomenon occurred mainly due to the presence of unhydrated cement particles in the presence of water. Mechanism of polymer in concrete depends on creating a layer and net of polymer around cement particles which enhances the properties of polymer modified concrete. This mechanism may affect the self healing of this type of concrete. This work aims to study the presence of the self healing phenomenon in polymer modified concrete and the related parameters. An experimental investigation on self healing of polymer modified concrete was undertaken. In this research work, effect of polymer type, polymer dose, cement content, cement type, w/cm ratio and age of damage were studied. The healing process extended up to 60 days. Ultrasonic pulse velocity measurements were used to evaluate the healing process. Results indicated that, the self healing phenomenon existed in polymer modified concrete as in traditional concrete. The increase of polymer dose increases the healing degree at the same healing time. This increase depends on polymer type. Also, the decrease of w/cm ratio reduces the self healing degree while the use of Type V Portland cement improves the self healing process compared with Type I Portland cement. Cement content has an insignificant effect on healing process for both concrete with and without polymer. In addition, the increase of damage age decreases the efficiency of self healing process.

[Endodontics in motion: new concepts, materials and techniques 1. Hydraulic Calcium Silicate Cements].

Science.gov (United States)

Moinzadeh, A T; Jongsma, L; de Groot-Kuin, D; Cristescu, R; Neirynck, N; Camilleri, J

2015-01-01

Hydraulic Calcium Silicate Cements (HCSCs) constitute a group of materials that have become increasingly popular in endodontics since the introduction of Mineral Trioxide Aggregate (MTA) in the 1990s. MTA is Portland cement to which bismuth oxide has been added to increase its radiopacity. The most important property of MTA is its capacity to set in water or a humid environment. However, MTA also has important limitations, for example, it's difficult to work with and can discolour teeth. Recently, numerous products based on HCSC chemistry, which can be considered as modifications of MTA intended to reduce its limitations, have become available on the market. Despite their potential advantages, all of these materials have their own specific limitations that are currently insufficiently known and investigated.

The influence of the amount addition and kind of the active silica fume in the mechanical properties of the cement Portland concrete

International Nuclear Information System (INIS)

Silva, I.J. da; Melo, A.B. de; Liborio, J.B.L.; Souza, M.F. de

1998-01-01

This study presents an evaluation of the influence of the amount addition and of active silica type deriving from residues of the production of Iron-Silicon alloys of brasilian industries, on the mechanical properties of the concrete made with basaltic aggregates with D max ≥9,5 mm using Portland cements CP II E 32. The study has for objective to evaluate the efficiency of the active silica on the mechanical resistance of the high performance concrete (CAD), when used in substitution of the Portland cement, even so maintaining the same amount of agglomerant material. They are appraised amount of 5%, 8%, 10%, 12% and 15% of active silica in relation to Portland cement mass. The results suggest that for the appraised silicas there is little efficiency. Other aspects related to the mixtures just with addictive water reducers are commented with the purpose of also providing a high performance concrete. (author)

Polymer reinforcement of cement systems

International Nuclear Information System (INIS)

Swamy, R.N.

1979-01-01

In the last couple of decades several cement- and concrete-based composites have come into prominence. Of these, cement-polymer composites, like cement-fibre composites, have been recognised as very promising, and considerable research and development on their properties, fabrication methods and application are in progress. Of the three types of concrete materials which incorporate polymers to form composites, polymer impregnated concrete forms a major development in which hardened concrete is impregnated with a liquid monomer which is subsequently polymerized to form a rigid polymer network in the pores of the parent material. In this first part of the extensive review of the polymer reinforcement of cement systems, the process technology of the various monomer impregnation techniques and the properties of the impregnated composite are assessed critically. It is shown that the high durability and superior performance of polymer impregnated concrete can provide an economic and competitive alternative in in situ strengthening, and in other areas where conventional concrete can only at best provide adequate performance. The review includes a section on radiation-induced polymerization. (author)

Thermal-hydraulic assessment of concrete storage cubicle with horizontal 3013 canisters

Energy Technology Data Exchange (ETDEWEB)

HEARD, F.J.

1999-04-08

The FIDAP computer code was used to perform a series of analyses to assess the thermal-hydraulic performance characteristics of the concrete plutonium storage cubicles, as modified for the horizontal placement of 3013 canisters. Four separate models were developed ranging from a full height model of the storage cubicle to a very detailed standalone model of a horizontal 3013 canister.

Thermal-hydraulic assessment of concrete storage cubicle with horizontal 3013 canisters

International Nuclear Information System (INIS)

Heard, F.J.

1999-01-01

The FIDAP computer code was used to perform a series of analyses to assess the thermal-hydraulic performance characteristics of the concrete plutonium storage cubicles, as modified for the horizontal placement of 3013 canisters. Four separate models were developed ranging from a full height model of the storage cubicle to a very detailed standalone model of a horizontal 3013 canister

Development of Concrete Paving Blocks Prepared from Waste Materials without Portland Cement

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Charin NAMARAK

2018-02-01

Full Text Available This experiment used three types of waste materials: calcium carbide residue, fly ash, and recycled concrete aggregate to develop concrete paving blocks. The blocks had calcium carbide residue and fly ash as a binder without ordinary Portland cement (OPC and combined with 100 % of recycled concrete aggregate. The concrete paving blocks were 10 × 10 × 20 cm and were formed using a pressure of 6 or 8 MPa. The binder-to-aggregate ratio was held constant at 1:3 by weight, while the water-to-binder ratios were 0.30, 0.35, and 0.40. The effects of the water-to-binder ratios and fineness of the binder on the compressive strength, flexural strength, abrasion resistance, and water absorption of the concrete paving blocks were determined and compared with those of TIS 827 and ASTM C1319 standards. The results revealed that by applying this procedure, we were able to produce an excellence concrete paving block without using OPC. The compressive strength of the concrete paving blocks made from these waste materials was 41.4 MPa at 28 days and increased to 45.3 MPa at 60 days. Therefore, these waste materials can be used as raw materials to manufacture concrete paving blocks without OPC that meet the requirements of 40 MPa and 35 MPa specified by the TIS 827 and ASTM C1319 standards, respectively.DOI: http://dx.doi.org/10.5755/j01.ms.24.1.17566

EFFECT OF SEA WATER ON THE STRENGTH OF POROUS CONCRETE CONTAINING PORTLAND COMPOSITE CEMENT AND MICROFILAMENT POLYPROPYLENE FIBER

OpenAIRE

TJARONGE, M.W

2011-01-01

The aim of this research is to study the influence of sea water on the strength of porous concrete containing Portland Composite cement and micro monofilament polypropylene fibre. The specimens of porous concrete were immersed in the sea water up to 28 days. The compressive strength test and flexural strength test were carried out at 3, 7 and 28 days in order to investigate the strength development. The test result indicated that the strength of porous concrete can develop in t...

Potential of Hollow Glass Microsphere as Cement Replacement for Lightweight Foam Concrete on Thermal Insulation Performance

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Shahidan Shahiron

2017-01-01

Full Text Available Global warming can be defined as a gradual increase in the overall temperature of the earth’s atmosphere. A lot of research work has been carried out to reduce that heat inside the residence such as the used of low density products which can reduce the self-weight, foundation size and construction costs. Foamed concrete it possesses high flow ability, low self-weight, minimal consumption of aggregate, controlled low strength and excellent thermal insulation properties. This study investigate the characteristics of lightweight foamed concrete where Portland cement (OPC was replaced by hollow glass microsphere (HGMs at 0%, 3%, 6%, 9% by weight. The density of wet concrete is 1000 kg/m3 were tested with a ratio of 0.55 for all water binder mixture. Lightweight foamed concrete hollow glass microsphere (HGMs produced were cured by air curing and water curing in tank for 7, 14 and 28 days. A total of 52 concrete cubes of size 100mm × 100mm × 100mm and 215mm × 102.5mm × 65mm were produced. Furthermore, Scanning Electron Microscope (SEM and X-ray fluorescence (XRF were carried out to study the chemical composition and physical properties of crystalline materials in hollow glass microspheres. The experiments involved in this study are compression strength, water absorption test, density and thermal insulation test. The results show that the compressive strength of foamed concrete has reached the highest in 3% of hollow glass microsphere with less water absorption and less of thermal insulation. As a conclusion, the quantity of hollow glass microsphere plays an important role in determining the strength and water absorption and also thermal insulation in foamed concrete and 3% hollow glass microspheres as a replacement for Portland cement (OPC showed an optimum value in this study as it presents a significant effect than other percentage.

Comparison on Heat of Hydration between Current Concrete for NPP and High Fluidity Concrete including Pozzolan Powders

International Nuclear Information System (INIS)

Noh, Jea Myoung; Cho, Myung Sug

2010-01-01

Nuclear power plant (NPP) concrete structures are exposed to many construction factors that lower the quality of concrete due to densely packed reinforcements and heat of hydration since they are mostly constructed with mass concrete. The concrete currently being used in Korean NPPs is mixed with Type I cement and fly ash. However, there is a demand to improve the performance of concrete with reduced heat of hydration and superior constructability. Many advantages such as improving workability and durability of concrete and decreasing heat of hydration are introduced by replacing cement with pozzolan binders. Therefore, the manufacturing possibility of high fluidity concrete should be investigated through applying multi-component powders blended with pozzolan binders to the concrete structure of NPPs, while the researches on properties, characteristic of hydration, durability and long-term behavior of high fluidity concrete using multi-component cement should be carried out. High fluidity concrete which is made using portland cement and pozzlonan powders such as fly ash and blast furnace slag has better properties on heat of hydration than the concrete currently in use for NPPs

Sulfur polymer cement, a solidification and stabilization agent for hazardous and radioactive wastes

International Nuclear Information System (INIS)

Darnell, G.R.

1992-01-01

Hydraulic cements have been the primary radioactive waste stabilization agents in the United States for 50 years. Twelve years ago, Brookhaven National Laboratory was funded by the Department of Energy's Defense Low-Level Waste Management Program to test and develop sulfur polymer cement (SPC). It has stabilized routine wastes as well as some troublesome wastes with high waste-to-agent ratios. The Department of Energy's Hazardous Waste Remedial Action Program joined the effort by providing funding for testing and developing sulfur polymer cement as a hazardous-waste stabilization agent. Sulfur polymer cement has passed all the laboratory scale tests required by the US Environmental Protection Agency and US Nuclear Regulatory Commission. Two decades of tests by the US Bureau of Mines and private concrete contractors indicate this agent is likely to exceed other agents in longevity. This bulletin provides technical data from pertinent tests conducted by these various entities

Suitability of geopolymeric concretes for nuclear waste disposal

International Nuclear Information System (INIS)

Ipatti, A.; Kallio, L.

1991-12-01

Concrete barriers are in essential role in most of the disposal concepts for nuclear waste. As to the binders, the used high-quality, strong and dense concretes may be based both on the present types of cements and on new types of special cements. One feasible special cement discussed in this literature report is the geopolymeric cement, which is, at its cleanest, a completely lime-free binder composed mainly of aluminium silicates. However, in 1990 the lime-free aluminium silicate cement had not yet reached the stage of development required of a widely marketed factory product. On the other hand, as an applicable product the development work started as early as in the 70s in France and in the USA has reached a blended cement consisting both of geopolymeric and Portland cements. The main advantages of the geopolymeric concrete compared to the ordinary Portland cement concrete are based on richer and stronger chemical bonds of the cement stone. The strong three-dimensional networks of bonds make the geopolymeric concrete stronger, denser and, above all, more ductile. The geopolymeric concrete is particularly suitable for hazardous waste applications, since hazardous materials have been found to be locked inside the geopolymeric networks. The properties of the geopolymeric cements and concretes and the implemented applications seem to be highly promising, but as to the nuclear waste applications there is not sufficient amount of reliable experimental information available yet. The domestic cement and concrete industry will be in key position in accumulation of information and operating experiences. (orig.)

Evolution of sorption properties in large-scale concrete structures accounting for long-term physical-chemical concrete degradation - 59297

International Nuclear Information System (INIS)

Perko, Janez; Jacques, Diederik; Mallants, Dirk; Seetharam, Suresh

2012-01-01

Long-term safety of radioactive waste disposal facilities relies on the longevity of natural or engineered barriers designed to minimize the migration of contaminants from the facility into the environment. Especially near surface disposal facilities, such as planned by ONDRAF/NIRAS for the Dessel site in Belgium, long-term safety relies almost exclusively on the containment ability of the engineered barriers (EB) with concrete being the most important EB material used. Concrete is preferred over other materials mainly due to its favourable chemical properties resulting in a high chemical retention capacity, and owing to its good hydraulic isolation properties. However, due to the long time frames typically involved in safety assessment, the chemical, physical and mechanical properties of concrete evolve in time. The alterations in concrete mineralogy also cause changes in pH and sorption behaviour for many radionuclides during chemical degradation processes. Application of dynamic sorption of concrete requires an adequate knowledge of long-term concrete degradation processes, knowledge of the effect of changing mineralogy to sorption of radionuclides and knowledge of large-scale system behaviour over time. Moreover, when applied to safety assessment models, special attention is required to assure robustness and transparency of the implementation. The discussion in this paper focuses on the sorption properties of concrete; selection of data, rescaling issues and on the hypotheses used to build a robust and yet transparent dynamic model for large-scale concrete structures for assessing the long-term performance. In this paper we summarize the steps required for the appropriate use of sorption values for large-scale cementitious components accounting for long-term concrete degradation in safety assessment studies. Four steps were recognized through the safety assessment in the framework of the license application for the near-surface disposal facility in Dessel

The effect of fly ash and coconut fibre ash as cement replacement materials on cement paste strength

Science.gov (United States)

Bayuaji, R.; Kurniawan, R. W.; Yasin, A. K.; Fatoni, H. AT; Lutfi, F. M. A.

2016-04-01

Concrete is the backbone material in the construction field. The main concept of the concrete material is composed of a binder and filler. Cement, concrete main binder highlighted by environmentalists as one of the industry are not environmentally friendly because of the burning of cement raw materials in the kiln requires energy up to a temperature of 1450° C and the output air waste CO2. On the other hand, the compound content of cement that can be utilized in innovation is Calcium Hydroxide (CaOH), this compound will react with pozzolan material and produces additional strength and durability of concrete, Calcium Silicate Hydrates (CSH). The objective of this research is to explore coconut fibers ash and fly ash. This material was used as cement replacement materials on cement paste. Experimental method was used in this study. SNI-03-1974-1990 is standard used to clarify the compressive strength of cement paste at the age of 7 days. The result of this study that the optimum composition of coconut fiber ash and fly ash to substitute 30% of cement with 25% and 5% for coconut fibers ash and fly ash with similar strength if to be compared normal cement paste.

High Early-Age Strength Concrete for Rapid Repair

Science.gov (United States)

Maler, Matthew O.

The aim of this research was to identify High Early-Age Strength (HES) concrete batch designs, and evaluate their suitability for use in the rapid repair of highways and bridge decks. To this end, two criteria needed to be met; a minimum compressive strength of 20.68 MPa (3000 psi) in no later than 12 hours, and a drying shrinkage of less than 0.06 % at 28 days after curing. The evaluations included both air-entrained, and non-air-entrained concretes. The cement types chosen for this study included Type III and Type V Portland cement and "Rapid Set"--a Calcium Sulfoaluminate (CSA) cement. In addition, two blended concretes containing different ratios of Type V Portland cement and CSA cement were investigated. The evaluation of the studied concretes included mechanical properties and transport properties. Additionally, dimensional stability and durability were investigated. Evaluations were conducted based on cement type and common cement factor. Fresh property tests showed that in order to provide a comparable workability, and still remain within manufactures guideline for plasticizer, the water-to-cement ratio was adjusted for each type of cement utilized. This resulted in the need to increase the water-to-cement ratio as the Blaine Fineness of the cement type increased (0.275 for Type V Portland cement, 0.35 for Type III Portland cement, and 0.4 for Rapid Set cement). It was also observed that negligible changes in setting time occurred with increasing cement content, whereas changes in cement type produced notable differences. The addition of air-entrainment had beneficial effect on workability for the lower cement factors. Increasing trends for peak hydration heat were seen with increases in cement factor, cement Blaine Fineness, and accelerator dosage. Evaluation of hardened properties revealed opening times as low as 5 hours for Type V Portland cement with 2.0 % accelerator per cement weight and further reduction in opening time by an hour when accelerator

Influence of chemical bonding of chlorides with aluminates in cement hidratation process on corrosion steel bars in concrete

Directory of Open Access Journals (Sweden)

Bikić Farzet H.

2010-01-01

Full Text Available The presence of chlorides in concrete is a permanent subject of research because they cause corrosion of steel bars. Chlorides added to the concrete during preparation, as accelerators of the bonding of cement minerals process, enter into reaction with aluminates, creating a phase known as chloroaluminate hydrates. In everyday conditions the product of chemical bonding between chlorides and aluminates is usually monochloridealuminate C3A·CaCl2·Hx, better known as Friedel's salt. In this paper, the influence of chemical bonding of chlorides with aluminates during the process of cement hydration on corrosion of steel bars in concrete was investigated. The process of chlorides bonding with aluminates yielding monochloride aluminate is monitored by XRD analyses. It was found that the amount of chlorides bonding with aluminates increases with an increase of temperature, and as a result, reduces the amount of 'free' chlorides in concrete. Potentiodynamic measurements have shown that increase in temperature of the heat treatment of working electrodes by chlorides leads to a reduction of steel bars corrosion as a result of either the increase of the monochloride-aluminate content or the decrease of free chlorides amount. Chlorides bound in chloroaluminate hydrates do not cause activation of steel bars corrosion in concrete. It was also proven that the increase of free chlorides concentration in the concrete leads to intensification of steel bars corrosion. This additionally approves that free chlorides are only the activators of process of steel bars corrosion in the concrete.

The durability of concrete containing a high-level of fly ash or a ternary blend of supplementary cementing materials

Science.gov (United States)

Gilbert, Christine M.

The research for this study was conducted in two distinct phases as follows: Phase 1: The objective was to determine the effect of fly ash on the carbonation of concrete. The specimens made for this phase of the study were larger in size than those normally used in carbonation studies and were are meant to more accurately reflect real field conditions. The results from early age carbonation testing indicate that the larger size specimens do not have a measured depth of carbonation as great as that of the smaller specimens typically used in carbonation studies at the same age and under the same conditions. Phase 2: The objective was to evaluate the performance of ternary concrete mixes containing a ternary cement blend consisting of Portland cement, slag and Type C fly ash. It was found that concrete mixtures containing the fly ash with the lower calcium (CaO) content (in binary or ternary blends) provided superior durability performance and resistance to ASR compared to that of the fly ash with the higher CaO content. Ternary blends (regardless of the CaO content of the fly ash) provided better overall durability performance than binary blends of cementing materials or the control.

Study on cement mortar and concrete made with sewage sludge ash.

Science.gov (United States)

Chang, F C; Lin, J D; Tsai, C C; Wang, K S

2010-01-01

This study investigated the feasibility of reusing wastewater sludge ash in construction materials to replace partial materials. Wastewater sludge sampled from thermal power plant was burned into sludge ash at 800°C in the laboratory. The sludge incineration ash has low heavy metal including Pb, Cd, Cr and Cu, so it belongs to general enterprise waste. The chemical composition of sludge incineration ash was summed up in SiO₂, CaO, Fe₂O₃ and MgO. Then the wastewater sludge ash is also found to be a porous material with irregular surface. When the sludge ash was used to replace mortar or concrete cement, its water-adsorption capability will result in the reduction of mortar workability and compressive strength. Cement is being substituted for sludge ash, and 10 percent of sludge ash is more appropriate. Sludge ash is reused to take the place of construction materials and satisfies the requests of standard specification except for higher water absorption.

The effect of bond characteristics between steel slag fine aggregate and cement paste on mechanical properties of concrete and mortar

International Nuclear Information System (INIS)

Yuji, W.

1988-01-01

The ordinary fine aggregate in concrete has been replaced by ground and sieved steel slag fine aggregate, treated and exposed to air for three months. Compared with concrete made from natural sand, properties such as compressive strength, flexural strength, elastic modules, permeability and abrasion resistance are considerably improved. The improvement increases with a decrease in w/c ratio, an increase in curing time and an increase in the replacement weight of sand. These results are due to the fact that the steel slag contains some active minerals such as C/sub 3/S, C/sub 2/S, C/sub 4/AF, etc., and shows favorable surface physical characteristics that improve the bond between steel slag particles and cement paste. The results of XRD, SEM and EPM microhardness showed that there are heavier concentration of ions, with finer crystals and a lower degree of CH orientation at the interfacial zone between steel slag particles and cement paste. The study also found small cementitious and fibrous C-S-H crystals growing from the fine aggregate, which are linked with hydrated products form cement paste making the bond and structural characteristic more favorable with cement. The steel slag fine aggregate is an active mineral similar to cement. The bond between the aggregate and cement paste is strengthened both physically and chemically

Sustainable Concrete Technology

Directory of Open Access Journals (Sweden)

Sim J.

2015-12-01

Full Text Available The growing concern over global warming and significant ecological changes requires sustainable development in all fields of science and technology. Concrete not only consumes huge amount of energy and natural sources, but also emits large amount of CO2, mainly due to the production of cement. It is evident that such large amount of concrete production has put significant impact on the energy, resource, environment, and ecology of the society. Hence, how to develop the concrete technology in a sustainable way has become a significant issue. In this paper, some of Korean researches for sustainable development of concrete are presented. These are sustainable strengthening for deteriorated concrete structure, sustainable reinforcement of new concrete structure, sustainable concrete using recycled aggregate and supplementary cementing materials and finally application of each technique to precast concrete.

Objectification of Modulus Elasticity of Foam Concrete Poroflow 17-5 on the Subbase Layer

Directory of Open Access Journals (Sweden)

Hájek Matej

2016-05-01

Full Text Available Principles of sustainable development create the need to develop new building materials. Foam concrete is a type of lightweight concrete that has many advantages compared to conventional building materials, for example low density and thermal insulation characteristics. With current development level, any negatively influencing material features are constantly eliminated as well. This paper is dealing with substitution of hydraulically bound mixtures by cement foam concrete Poroflow 17-5. The executed assessment is according to the methodology of assessing the existing asphalt pavements in Slovak Republic. The ex post calculation was used to estimate modulus range for Poroflow 17-5 based on the results of static load tests conducted using the Testing Experiment Equipment.

Development of an eco-friendly Ultra-High Performance Concrete (UHPC) with efficient cement and mineral admixtures uses

NARCIS (Netherlands)

Yu, R.; Spiesz, P.R.; Brouwers, H.J.H.

2015-01-01

This paper addresses the development of an eco-friendly Ultra-High Performance Concrete (UHPC) with efficient cement and mineral admixtures uses are investigated. The modified Andreasen & Andersen particle packing model is utilized to achieve a densely compacted cementitious matrix. Fly ash (FA),

The Impact of Coal Combustion Fly Ash Used as a Supplemental Cementitious Material on the Leaching of Constituents from Cements and Concretes

Science.gov (United States)

The objective of this report is to compare the leaching of portland cement-based materials that have been prepared with and without coal combustion fly ash to illustrate whether there is evidence that the use of fly ash in cement and concrete products may result in increased leac...

Multi-scale modeling of the thermo-hydro- mechanical behaviour of heterogeneous materials. Application to cement-based materials under severe loads

International Nuclear Information System (INIS)

Grondin, Frederic Alain

2005-01-01

The work of modeling presented here relates to the study of the thermo-hydro- mechanical behaviour of porous materials based on hydraulic binder such as concrete, High Performance Concrete or more generally cement-based materials. This work is based on the exploitation of the Digital Concrete model, of the finite element code Symphonie developed in the Scientific and Technical Centre for Building (CSTB), in coupling with the homogenization methods to obtain macroscopic behaviour laws drawn from the Micro-Macro relations. Scales of investigation, macroscopic and microscopic, has been exploited by simulation in order to allow the comprehension fine of the behaviour of cement-based materials according to thermal, hydrous and mechanical loads. It appears necessary to take into account various scales of modeling. In order to study the behaviour of the structure, we are brought to reduce the scale of investigation to study the material more particularly. The research tasks presented suggest a new approach for the identification of the multi-physic behaviour of materials by simulation. In complement of the purely experimental approach, based on observations on the sample with measurements of the apparent parameters on the macroscopic scale, this new approach allows to obtain the fine analysis of elementary mechanisms in acting within the material. These elementary mechanisms are at the origin of the evolution of the macroscopic parameters measured in experimental tests. In this work, coefficients of the thermo-hydro-mechanical behaviour law of porous materials and the equivalent hydraulic conductivity were obtained by a multi-scales approach. Applications has been carried out on the study of the damaged behaviour of cement-based materials, in the objective to determine the elasticity tensor and the permeability tensor of a High Performance Concrete at high temperatures under a mechanical load. Also, the study of the strain evolution of cement-based materials at low

Mechanical Properties of Lightweight Concrete Using Recycled Cement-Sand Brick as Coarse Aggregates Replacement

Science.gov (United States)

Joohari, Ilya; Farhani Ishak, Nor; Amin, Norliyati Mohd

2018-03-01

This paper presents the result of replacing natural course aggregate with recycled cement-sand brick (CSB) towards the mechanical properties of concrete. Natural aggregates were used in this study as a control sample to compare with recycled coarse aggregates. This study was also carried to determine the optimum proportion of coarse aggregates replacement to produce lightweight concrete. Besides, this study was conducted to observe the crack and its behaviour development during the mechanical testing. Through this study, four types of concrete mixed were prepared, which were the control sample, 25%, 50% and 75% replacement of CSB. The test conducted to determine the effectiveness of recycled CSB as coarse aggregates replacement in this study were slump test, density measurement, compression test, and flexural test and. The strength of concrete was tested at 7 days and 28 days of curing. From the results obtained, the optimum proportion which produced the highest strength is 25% replacement of recycled CSB. The compressive and flexural strength has decreased by 10%-12% and 4%-34% respectively compared to the control sample. The presence of recycled coarse aggregates in sample has decreased the density of concrete by 0.8%-3% compared to the control sample.

Modelling porewater chemistry in hydrated Portland cement

International Nuclear Information System (INIS)

Berner, U.R.

1987-01-01

Extensive employment of concrete is foreseen in radioactive waste repositories. A prerequisite for modelling the interactions between concrete and formation waters is characterization of the concrete system. Available experimental data from high pressure squeezing of cement pore-water indicate that, besides the high pH due to alkali hydroxide dissolution, cement composition itself influences the solubility determining solid phases. A model which simulates the hydration of Portland cement assuming complete hydration of the main clinker minerals is presented. The model also includes parameters describing the reactions between the cement and blending agents. Comparison with measured pore-water data generally gives a consistent picture and, as expected, the model gives correct predictions for pure Portland cements. For blended cements, the required additional parameters can, to some extent, be derived from pore-water analysis. 14 references, 1 figure, 4 tables

Setting temperature evolution of nitrate radwaste immobilized in ordinary portland cement

International Nuclear Information System (INIS)

Rzyski, B.M.; Suarez, A.A.

1988-01-01

Materials based on hydraulic cements such as ordinary Portland cement (OPC) have many applications in the radioactive waste disposal field. Cement hydration process is an exothermic reaction and can cause a considerable temperature rise in the cemented waste form. Specially when large blocks of waste forms are produced it is necessary to have some information about the temperature build up which occurs inside the mass, because this effect may have some influences on the ultimate properties of the hardened cement paste. This temperature rise cause expansion while the cement paste is hardening. When the cooling process takes place, to the surrounding temperature, crackings and contractions may then occur. Whether cracking arise it depends both on the magnitude of the temperature induced stress and on the capacity of the mixture to accommodate the strain. This paper compares the temperature growth in pastes into two different geometries: one uses a waste container with 3.8 dm 3 (one US gallon) capacity placed inside a 0.21 m 3 (55 gallons) concrete lined drum, which acts as a radiation shielding, and the other the same container placed in ambient at room temperature. Correlations between the time of temperature occurrence, maximum temperature, the water to cement ratio and salt content were observed

Tritium sorption by cement and subsequent release

International Nuclear Information System (INIS)

Ono, F.; Tanaka, S.; Yamawaki, M.

1994-01-01

In a fusion reactor or tritium handling facilities, contamination of concrete by tritium and subsequent release from it to the reactor or experimental rooms is a matter of problem for safety control of tritium and management of operational environment. In order to evaluate these tritium behavior, interaction of tritiated water with concrete or cement should be clarified. In the present study, HTO sorption and subsequent release from cement were studied by combining various experimental methods. From the basic studies on tritium-cement interactions, it has become possible to evaluate tritium uptake by cement or concrete and subsequent tritium release behavior as well as tritium removing methods from them

Study of Influence of Composite Materials Components on Properties of Concrete Mixtures and Concrete in Time Dynamics

Science.gov (United States)

Butakova, M. D.; Gorbunov, S. P.

2017-11-01

It is accepted to call concrete a special construction mix which consists of several main components - most often, these are cement, water and various fillers. As a result of grout hardening, the artificial stone, used in many areas where durability, stability and durability are required, is formed. To improve the main characteristics of concrete, various additives are added to the mix. These substances are also capable of accelerating the speed of construction and reducing the funds expenditure. It is especially important to apply additives at the installation of coverings to airfields, at the construction of moorings, roads, at the laying of pools or during other hydraulic engineering constructions, and also at the construction of monolithic industrial facilities and houses. The article deals with the composition and quantity of complex organomineral additives, the duration and conditions for the formation of composites’ structure.

The Evaluation of Damage Effects on MgO Added Concrete with Slag Cement Exposed to Calcium Chloride Deicing Salt

Science.gov (United States)

Jang, Jae-Kyeong; Kim, Hong-Gi; Kim, Jun-Hyeong

2018-01-01

Concrete systems exposed to deicers are damaged in physical and chemical ways. In mitigating the damage from CaCl2 deicers, the usage of ground slag cement and MgO are investigated. Ordinary Portland cement (OPC) and slag cement are used in different proportions as the binding material, and MgO in doses of 0%, 5%, 7%, and 10% are added to the systems. After 28 days of water-curing, the specimens are immersed in 30% CaCl2 solution by mass for 180 days. Compressive strength test, carbonation test, chloride penetration test, chloride content test, XRD analysis, and SEM-EDAX analysis are conducted to evaluate the damage effects of the deicing solution. Up to 28 days, plain specimens with increasing MgO show a decrease in compressive strength, an increase in carbonation resistance, and a decrease in chloride penetration resistance, whereas the S30- and S50- specimens show a slight increase in compressive strength, an increase in carbonation resistance, and a slight increase in chloride penetration resistance. After 180 days of immersion in deicing solution, specimens with MgO retain their compressive strength longer and show improved durability. Furthermore, the addition of MgO to concrete systems with slag cement induces the formation of magnesium silicate hydrate (M-S-H) phases. PMID:29758008

The Evaluation of Damage Effects on MgO Added Concrete with Slag Cement Exposed to Calcium Chloride Deicing Salt.

Science.gov (United States)

Jang, Jae-Kyeong; Kim, Hong-Gi; Kim, Jun-Hyeong; Ryou, Jae-Suk

2018-05-14

Concrete systems exposed to deicers are damaged in physical and chemical ways. In mitigating the damage from CaCl₂ deicers, the usage of ground slag cement and MgO are investigated. Ordinary Portland cement (OPC) and slag cement are used in different proportions as the binding material, and MgO in doses of 0%, 5%, 7%, and 10% are added to the systems. After 28 days of water-curing, the specimens are immersed in 30% CaCl₂ solution by mass for 180 days. Compressive strength test, carbonation test, chloride penetration test, chloride content test, XRD analysis, and SEM-EDAX analysis are conducted to evaluate the damage effects of the deicing solution. Up to 28 days, plain specimens with increasing MgO show a decrease in compressive strength, an increase in carbonation resistance, and a decrease in chloride penetration resistance, whereas the S30- and S50- specimens show a slight increase in compressive strength, an increase in carbonation resistance, and a slight increase in chloride penetration resistance. After 180 days of immersion in deicing solution, specimens with MgO retain their compressive strength longer and show improved durability. Furthermore, the addition of MgO to concrete systems with slag cement induces the formation of magnesium silicate hydrate (M-S-H) phases.

Progress of admixtures and quality of concrete. 2. ; Approaches to ultra-high-strength concrete. Konwa zairyo no shinpo to concrete no hinshitsu. 2. ; Chokokyodo concrete eno approach

Energy Technology Data Exchange (ETDEWEB)

Kawai, T. (Shimizu Construction Co. Ltd., Tokyo (Japan)); Abe, M. (Building Research Institute, Tsukuba (Japan))

1994-02-15

Ultra-high-strength concrete of 600 kgf/cm[sup 2] or more is reviewed. MDF (macro defect free) cement, spheroidal cement and mechanically stabilized cement have been developed for ultra-high-strength concrete, however, in general, DSP (densified system containing homogeneously arranged ultra-fine particles) technique is now usual in which a water-cement ratio is reduced by use of advanced air entraining and water reducing agents and cured concrete is densified by use of ultra-fine particles as admixture. Four kinds of substances such as naphthalene system and polycarboxylic acid system are used as air entraining and water reducing agents, and silica fume is used as ultra-fine particle admixture which can be effectively replaced with blast furnace slag or fly ash. Various use examples of ultra-high-strength concrete such as an ocean platform are found in the world, however, only some examples such as a PC truss bridge and the main tower of a PC cable stayed bridge in Japan. 22 refs., 10 figs., 2 tabs.

Prompt gamma-ray analysis of steel slag in concrete

International Nuclear Information System (INIS)

Naqvi, Akhtar Abbas; Garwan, Muhammad Ahmad; Nagadi, Mahmoud Mohammad; Rehman, Khateeb-ur; Raashid, Mohammad; Masalehuddin Mohiuddin, Mohammad; Al-Amoudi, Omar Saeed Baghabra

2009-01-01

Blast furnace slag (BFS) is added to Portland cement concrete to increase its durability, particularly its corrosion resistance. Monitoring the concentration of BFS in concrete for quality control purposes is desired. In this study, the concentration of BFS in concrete was measured by utilizing an accelerator-based prompt gamma-ray neutron activation analysis (PGNAA) setup. The optimum size of the BFS cement concrete specimen that produces the maximum intensity of gamma rays at the detector location was calculated through Monte Carlo simulations. The simulation results were experimentally validated through the gamma-ray yield measurement from BFS cement concrete specimens having different radii. The concentration of BFS in the cement concrete specimens was assessed through calcium and silicon gamma-ray yield measurement from cement concrete specimens containing 5 to 80 wt% BFS. The yield of calcium gamma rays decreases with increasing BFS concentration in concrete while the yield of silicon gamma rays increases with increasing BFS concentration in concrete. The calcium-to-silicon gamma-ray yield ratio has an inverse relation with BFS concentration in concrete. (author)

Effectiveness of shrinkage-reducing admixtures on Portland pozzolan cement concrete

Directory of Open Access Journals (Sweden)

Videla, C.

2005-06-01

Full Text Available Drying shrinkage causes tensile stress in restrained concrete members. Since all structural elements are subject to some degree of restraint, drying shrinkage is regarded to be one of the main causes of concrete cracking. The purpose of the present study was to evaluate the effectiveness of SRA in reducing drying shrinkage strain in Portland pozzolan cement concrete. The major variables examined included slump, admixture type and dose, and specimen size. The measured results indicate that any of the admixtures used in the study significantly reduced shrinkage. Concrete manufactured with shrinkage reducing admixtures shrank an average of 43% less than concrete without admixtures. As a rule, the higher the dose of admixture, the higher was its shrinkage reduction performance. The experimental results were compared to the shrinkage strain estimated with the ACI 209, CEB MC 90, B3, GL 2000, Sakata 1993 and Sakata 2001 models. Although none of these models was observed to accurately describe the behaviour of Portland pozzolan cement concrete with shrinkage reducing admixtures, the Sakata 2001 model, with a weighted coefficient of variation of under 30%, may be regarded to be roughly adequate.

La retracción por secado es un fenómeno intrínseco del hormigón que produce tensiones de tracción en elementos restringidos de hormigón. Puesto que todos los elementos presentan algún grado de retracción, se considera a la retracción por secado como una de las principales causas de agrietamiento en proyectos de construcción en hormigón. Por lo tanto, el objetivo de esta investigación fue evaluar la efectividad de los aditivos reductores de retracción (SRA en hormigones fabricados con cemento Portland puzolánico. Las variables principales estudiadas incluyen el asentamiento de cono de Abrams, marca y dosis de aditivo reductor de retracción, y tamaño de espécimen de hormigón. Los resultados obtenidos permiten concluir que el uso de

High-volume natural volcanic pozzolan and limestone powder as partial replacements for portland cement in self-compacting and sustainable concrete

KAUST Repository

Celik, Kemal; Jackson, Marie D.; Mancio, Mauricio; Meral, Cagla; Emwas, Abdul-Hamid M.; Mehta, P. Kumar; Monteiro, Paulo José Meleragno

2014-01-01

A laboratory study demonstrates that high volume, 45% by mass replacement of portland cement (OPC) with 30% finely-ground basaltic ash from Saudi Arabia (NP) and 15% limestone powder (LS) produces concrete with good workability, high 28-day compressive strength (39 MPa), excellent one year strength (57 MPa), and very high resistance to chloride penetration. Conventional OPC is produced by intergrinding 95% portland clinker and 5% gypsum, and its clinker factor (CF) thus equals 0.95. With 30% NP and 15% LS portland clinker replacement, the CF of the blended ternary PC equals 0.52 so that 48% CO2 emissions could be avoided, while enhancing strength development and durability in the resulting self-compacting concrete (SCC). Petrographic and scanning electron microscopy (SEM) investigations of the crushed NP and finely-ground NP in the concretes provide new insights into the heterogeneous fine-scale cementitious hydration products associated with basaltic ash-portland cement reactions. © 2013 Published by Elsevier Ltd.

Performance of Kaolin Clay on the Concrete Pavement

Science.gov (United States)

Abdullah, M. E.; Jaya, R. P.; Shahafuddin, M. N. A.; Yaacob, H.; Ibrahim, M. H. Wan; Nazri, F. M.; Ramli, N. I.; Mohammed, A. A.

2018-05-01

This paper investigates the performance of concrete pavement containing kaolin clay with their engineering properties and to determine the optimum kaolin clay content. The concrete used throughout the study was designed as grade 30 MPa strength with constant water to cement ratio of 0.49. The compressive strength, flexural strength and water absorption test was conducted in this research. The concrete mix designed with kaolin clay as cement replacement comprises at 0%, 5%, 10% and 15% by the total weight of cement. The results indicate that the strength of pavement concrete decreases as the percentage of kaolin clay increases. It also shows that the water absorption increases with the percentage of cement replacement. However, 5% kaolin clay is found to be the optimum level to replace cement in a pavement concrete.

Copolymer natural latex in concrete: Dynamic evaluation through energy dissipation of polymer modified concrete

Science.gov (United States)

Andayani, Sih Wuri; Suratman, Rochim; Imran, Iswandi; Mardiyati

2018-05-01

Portland cement concrete have been used in construction due to its strength and ecomical value. But it has some limitations, such low flexural strength, low tensile strength, low chemical resistant and etc. Due to its limitations in flexural and tensile strength, Portland cement concrete more susceptible by seismic force. There are some methods for improving its limitations. Polymer addition into concrete mixture could be one of solution for improving the flexural and tensile strength, in aiming to get erthquake resistant properties. Also, the eartquake resistant could be achieved by improving energy dissipation capacity. In this research, the earthquake resistant evalution was approached from dynamic evaluation through energy dissipation capacity, after polymer addition as concrete additives. The polymers were natural latex (Indonesian naural resource) grafted with styrene and methacrylate, forming copolymer - natural latex methacrylate (KOLAM) and copolymer - natural latex styrene (KOLAS). They were added into concrete mixture resulting polymer modified concrete. The composition of polymer are 1%, 5% and 10% weight/weight of cement. The higher capacity of energy dissipation will give more capability in either absorbing or dissipating energy, and it was predicted would give better earthquake resistant.. The use of KOLAM gave better performance than KOLAS in energy dissipation capacity. It gave about 46% for addition of 1% w/w compared to Portland cement concrete. But for addition 5% w/w and 10% w/w, they gave about 7% and 5% higher energy dissipation capacity. The KOLAM addition into concrete mixture would reduce the maximum impact load with maximumabout 35% impact load reducing after 1% w/w addition. The higher concentration of KOLAM in concrete mixture, lower reducing of impact load, they were about 4% and 3% for KOLAM 5% and 10%. For KOLAS addition in any compositions, there were no positive trend either in energy dissipation capacity or impact load properties

Engineering properties of cement mortar with pond ash in South Korea as construction materials: from waste to concrete

Science.gov (United States)

Jung, Sang Hwa; Kwon, Seung-Jun

2013-09-01

Among the wastes from coal combustion product, only fly ash is widely used for mineral mixture in concrete for its various advantages. However the other wastes including bottom ash, so called PA (pond ash) are limitedly reused for reclamation. In this paper, the engineering properties of domestic pond ash which has been used for reclamation are experimentally studied. For this, two reclamation sites (DH and TA) in South Korea are selected, and two domestic PAs are obtained. Cement mortar with two different w/c (water to cement) ratios and 3 different replacement ratios (0%, 30%, and 60%) of sand are prepared for the tests. For workability and physical properties of PA cement mortar, several tests like flow, setting time, and compressive strength are evaluated. Several durability tests including porosity measuring, freezing and thawing, chloride migration, and accelerated carbonation are also performed. Through the tests, PA (especially from DH area) in surface saturated condition is evaluated to have internal curing action which leads to reasonable strength development and durability performances. The results show a potential applicability of PA to concrete aggregate, which can reduce consuming natural resources and lead to active reutilization of coal product waste.

Sulfur polymer cement, a new stabilization agent for mixed and low- level radioactive waste

International Nuclear Information System (INIS)

Darnell, G.R.

1991-01-01

Solidification and stabilization agents for radioactive, hazardous, and mixed wastes are failing to pass governmental tests at alarming rates. The Department of Energy's National Low-Level Waste Management Program funded testing of Sulfur Polymer Cement (SPC) by Brookhaven National Laboratory during the 1980s. Those tests and tests by the US Bureau of Mines (the original developer of SPC), universities, states, and the concrete industry have shown SPC to be superior to hydraulic cements in most cases. Superior in what wastes can be successfully combined and in the quantity of waste that can be combined and still pass the tests established by the US Environmental Protection Agency and the US Nuclear Regulatory Commission

Concrete, hardened: Self desiccation

DEFF Research Database (Denmark)

Hansen, Ernst Jan De Place; Hansen, Kurt Kielsgaard; Persson, Bertil

1999-01-01

The test method covers the determination of internal relative humidity (RH) in hardened concrete and cement mortar using RH instruments. The determination of RH is done on crushed samples of concrete or cement motar. This test method is only for measuring equipment which gives off or takes up...

An Investigation of the Uniaxial Compressive Strength of a Cemented Hydraulic Backfill Made of Alluvial Sand

Directory of Open Access Journals (Sweden)

Guangsheng Liu

2017-01-01

Full Text Available Backfill is commonly used in underground mines. The quality control of the backfill is a key step to ensure it meets the designed strength requirement. This is done through sample collection from the underground environment, followed by uniaxial compression tests to obtain the Uniaxial Compressive Strength (UCS in the laboratory. When the cylindrical cemented backfill samples are axially loaded to failure, several failure modes can be observed and mainly classified into diagonal shear failure and axial split failure. To date, the UCS obtained by these two failure modes are considered to be the same with no distinction between them. In this paper, an analysis of the UCS results obtained on a cemented hydraulic backfill made of alluvial sand at a Canadian underground mine over the course of more than three years is presented. The results show that the UCS values obtained by diagonal shear failure are generally higher than those obtained by axial split failure for samples with the same recipe and curing time. This highlights the importance of making a distinction between the UCS values obtained by the two different modes of failure. Their difference in failure mechanism is explained. Further investigations on the sources of the data dispersion tend to indicate that the UCS obtained by laboratory tests following the current practice may not be representative of the in-situ strength distribution in the underground stopes due to segregation in cemented hydraulic backfill.

Static and Dynamic Strain Monitoring of Reinforced Concrete Components through Embedded Carbon Nanotube Cement-Based Sensors

Directory of Open Access Journals (Sweden)

Antonella D’Alessandro

2017-01-01

Full Text Available The paper presents a study on the use of cement-based sensors doped with carbon nanotubes as embedded smart sensors for static and dynamic strain monitoring of reinforced concrete (RC elements. Such novel sensors can be used for the monitoring of civil infrastructures. Because they are fabricated from a structural material and are easy to utilize, these sensors can be integrated into structural elements for monitoring of different types of constructions during their service life. Despite the scientific attention that such sensors have received in recent years, further research is needed to understand (i the repeatability and accuracy of sensors’ behavior over a meaningful number of sensors, (ii testing configurations and calibration methods, and (iii the sensors’ ability to provide static and dynamic strain measurements when actually embedded in RC elements. To address these research needs, this paper presents a preliminary characterization of the self-sensing capabilities and the dynamic properties of a meaningful number of cement-based sensors and studies their application as embedded sensors in a full-scale RC beam. Results from electrical and electromechanical tests conducted on small and full-scale specimens using different electrical measurement methods confirm that smart cement-based sensors show promise for both static and vibration-based structural health monitoring applications of concrete elements but that calibration of each sensor seems to be necessary.

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

Science.gov (United States)

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

2016-09-01

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.

Effect of the microstructure of mortars with low hydraulicity slag on their behavior in aggressive environments

Directory of Open Access Journals (Sweden)

Ahmed Hadj sadok

2018-01-01

Full Text Available Slag is one of the most used cement additives. Due to its latent hydraulic nature, attached to its hydraulicity, it can contribute to a microstructural modification and an improvement of the durability of the concrete face of aggressive environments. In this study, a low active slag is used in the manufacture of mortars as a substitute for cement, at a maximum rate of 50%. Firstly, a study of the microstructure with mercury porosimetry was used for determination of microstructural parameters (porosity, diameters and volume distribution. The behavior of mortars in aggressive environments (sodium and magnesium sulphate and seawater was studied later. Despite the low reactivity of studied slag, its presence especially at 50% rate, in the long term, has led to a refinement of the microstructure. This effect, among others, led to better resistivity of the mortars in the sulphate environnements.

Porous Concrete and Its Application

Directory of Open Access Journals (Sweden)

V. V. Opekunov

2005-01-01

Full Text Available Some aspects of resource saving problem in the process of mass construction and operation of heated construction installations are considered in the paper. A special attention is paid to necessary application of porous concrete products in the process of the housing construction. The preference is given to the products made of autoclave cellular concrete and cement hydrophobisized cement perlite concrete.

Evaluation of cement thixotropy for the cement of oil wells in areas ...

African Journals Online (AJOL)

... economical for cementing job operations in wells with loss zones. The results also show that the effect of LHF is positive, since in addition to his contribution to long term performances, especially the durability of hardened concrete, it improves the thixotropy of cement made of plaster. Keywords: cementing; lost circulation; ...

Experimental and numerical modeling of chloride diffusivity in hardened cement concrete considering the aggregate shapes and exposure-duration effects

Directory of Open Access Journals (Sweden)

Wu Jie

Full Text Available This paper presents an experimental and numerical model describing the effects of the aggregate shapes and exposure duration of chloride diffusion into cement-based materials. A simple chloride diffusion test was performed on a concrete specimen composed of a mixture of cement mortar with crushed granites and round gravels. A simulation was done and the numerical model developed was applied to the matrix at the meso-scale level and the chloride diffusivity was investigated at 30, 60, and 90 days. The experimental and simulation results showed that the aggregate shape and the exposure duration of chloride diffusing into concrete are of high significance. It was indicated that the model with crushed granite presents a good resistance against chloride ingress, while the model with rounded gravels shows some sensitivity to the chloride penetration. It was also found out that when the time dependence of the diffusion coefficient is not taken into account, the diffusion rate will be overestimated. The meso-scale model developed in this study also provides a new method applied in the analysis of the chloride and water transport that causes damage to concrete considering the particle inclusion and the diffusion duration. Keywords: Meso-scale modeling, Chloride diffusivity, Concrete, Effects of aggregates shape and exposure duration, FEM

Deicer scaling resistance of concrete mixtures containing slag cement. Phase 2 : evaluation of different laboratory scaling test methods.

Science.gov (United States)

2012-07-01

With the use of supplementary cementing materials (SCMs) in concrete mixtures, salt scaling tests such as ASTM C672 have been found to be overly aggressive and do correlate well with field scaling performance. The reasons for this are thought to be b...

Mechanical properties of self-curing concrete (SCUC

Directory of Open Access Journals (Sweden)

Magda I. Mousa

2015-12-01

Full Text Available The mechanical properties of concrete containing self-curing agents are investigated in this paper. In this study, two materials were selected as self-curing agents with different amounts, and the addition of silica fume was studied. The self-curing agents were, pre-soaked lightweight aggregate (Leca; 0.0%, 10%, 15%, and 20% of volume of sand; or polyethylene-glycol (Ch.; 1%, 2%, and 3% by weight of cement. To carry out this study the cement content of 300, 400, 500 kg/m3, water/cement ratio of 0.5, 0.4, 0.3 and 0.0%, 15% silica fume of weight of cement as an additive were used in concrete mixes. The mechanical properties were evaluated while the concrete specimens were subjected to air curing regime (in the laboratory environment with 25 °C, 65% R.H. during the experiment. The results show that, the use of self-curing agents in concrete effectively improved the mechanical properties. The concrete used polyethylene-glycol as self-curing agent, attained higher values of mechanical properties than concrete with saturated Leca. In all cases, either 2% Ch. or 15% Leca was the optimum ratio compared with the other ratios. Higher cement content and/or lower water/cement ratio lead(s to more efficient performance of self-curing agents in concrete. Incorporation of silica fume into self-curing concrete mixture enhanced all mechanical properties, not only due to its pozzolanic reaction, but also due to its ability to retain water inside concrete.

Strength Characteristics of Groundnut Leaf/Stem Ash (GLSA Concrete

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Oseni O. W.

2016-09-01

Full Text Available 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.

Concrete and cement composites used for radioactive waste deposition.

Science.gov (United States)

Koťátková, Jaroslava; Zatloukal, Jan; Reiterman, Pavel; Kolář, Karel

2017-11-01

This review article presents the current state-of-knowledge of the use of cementitious materials for radioactive waste disposal. An overview of radwaste management processes with respect to the classification of the waste type is given. The application of cementitious materials for waste disposal is divided into two main lines: i) as a matrix for direct immobilization of treated waste form; and ii) as an engineered barrier of secondary protection in the form of concrete or grout. In the first part the immobilization mechanisms of the waste by cement hydration products is briefly described and an up-to date knowledge about the performance of different cementitious materials is given, including both traditional cements and alternative binder systems. The advantages, disadvantages as well as gaps in the base of information in relation to individual materials are stated. The following part of the article is aimed at description of multi-barrier systems for intermediate level waste repositories. It provides examples of proposed concepts by countries with advanced waste management programmes. In the paper summary, the good knowledge of the material durability due to its vast experience from civil engineering is highlighted however with the urge for specific approach during design and construction of a repository in terms of stringent safety requirements. Copyright © 2017 Elsevier Ltd. All rights reserved.

Magnesium oxychloride cement concrete

Indian Academy of Sciences (India)

The durability of MOC concrete compositions against extreme environmental conditions viz. heating–cooling, freezing–thawing, wetting–drying and penetration and deposition of salts etc were investigated. The results reveal that MOC concrete has high compressive strength associated with high flexural strength and the ...

Radon exhalation of hardening concrete: monitoring cement hydration and prediction of radon concentration in construction site.

Science.gov (United States)

Kovler, Konstantin

2006-01-01

The unique properties of radon as a noble gas are used for monitoring cement hydration and microstructural transformations in cementitious system. It is found that the radon concentration curve for hydrating cement paste enclosed in the chamber increases from zero (more accurately - background) concentrations, similar to unhydrated cement. However, radon concentrations developed within 3 days in the test chamber containing cement paste were approximately 20 times higher than those of unhydrated cement. This fact proves the importance of microstructural transformations taking place in the process of cement hydration, in comparison with cement grain, which is a time-stable material. It is concluded that monitoring cement hydration by means of radon exhalation method makes it possible to distinguish between three main stages, which are readily seen in the time dependence of radon concentration: stage I (dormant period), stage II (setting and intensive microstructural transformations) and stage III (densification of the structure and drying). The information presented improves our understanding of the main physical mechanisms resulting in the characteristic behavior of radon exhalation in the course of cement hydration. The maximum value of radon exhalation rate observed, when cement sets, can reach 0.6 mBq kg(-1) s(-1) and sometimes exceeds 1.0 mBq kg(-1) s(-1). These values exceed significantly to those known before for cementitious materials. At the same time, the minimum ventilation rate accepted in the design practice (0.5 h(-1)), guarantees that the concentrations in most of the cases will not exceed the action level and that they are not of any radiological concern for construction workers employed in concreting in closed spaces.

Natural radioactivity levels and danger ratio in cements, concretes and mortars used in construction; Determinacion de niveles radiactivos naturales e indices de peligrosidad en cementos, hormigones y morteros utilizados en construccion

Energy Technology Data Exchange (ETDEWEB)

Meneses, J.; Pacheco, C.; Avila, J. M.; Miro, C.

2010-07-01

We have determined the natural radiation level in three types of adhesive cements, five types of concrete and two types of mortars of different strength normally used in the construction field. Of these materials, both concrete and mortars were prepared in our laboratories, cements the contrary were of a commercial nature.

Influence of Crumb-Rubber in the Mechanical Response of Modified Portland Cement Concrete

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J. Retama

2017-01-01

Full Text Available The influence of crumb-rubber on the mechanical properties of Portland cement concrete (PCC is studied by experimental tests and numerical simulations. The main hypothesis of the study is that replacing part of the stone aggregate with crumb-rubber in the mix modifies the energy dissipation during the cracking process and affects the concrete behaviour under monotonically increasing loads. The experimental research program characterizes the mechanical properties of PCC for three different types of concrete with a variable content of crumb-rubber. The experimental results showed that fracture energy and other properties are directly related to the rubber fineness used in the mixture. The material properties derived for these laboratory tests are used to study, by numerical models, its response through its damage evolution. The numerical model used to simulate the damage evolution of the concrete is the Embedded Discontinuity Method (EDM. One characteristic of the EDM is that it does not need to modify the mesh topology to propagate the damage through the continuum solid. For this study, the Disk-Shaped Compact Tension specimen geometry, normed by the D7313-13 of the ASTM, is used. Results showed that the numerical methods provide good approximation of the experimental curve in the elastic and softening branches.

Experimental study on the performance of pervious concrete

Science.gov (United States)

Liu, Haojie; Liu, Rentai; Yang, Honglu; Ma, Chenyang; Zhou, Heng

2018-02-01

With the construction of sponge city, the pervious concrete material has been developed rapidly. A high-performance pervious concrete is developed by using cement, silica fume (SF) and superplasticizer (SP). The effects of SF, SP, aggregate size, water-cement ration and aggregate-cement ratio on the permeability coefficient, compressive strength and flexural strength are studied by controlling variables, and exploring the corrosion resistance and abrasion resistance of pervious concrete. The results show that using 0.5% SP, 5% SF and small aggregate can greatly improve the strength. There is an optimum value for water-cement ratio to make the strength and permeability coefficient maximum. Compared to ordinary pervious concrete, the corrosion resistance and abrasion resistance of this pervious concrete are very good.

Durability of ultra-high performance concretes: role of the cement matrix

International Nuclear Information System (INIS)

Matte, Veronique

1999-01-01

The Reactive Powder Concretes (RPC), composed of Portland cement, silica fume, crushed quartz, fine sand and steel fibers, exhibit a very dense microstructure which limits the penetration of aggressive agents. They appear suitable for the storage of nuclear waste. This study aimed to determine experimentally the evolution of the RPC microstructure during a leaching attack by pure water, and to supply data required for the RPC long-term prediction of durability under these severe conditions. The steel fibers and mineral inclusions (sand and quartz) were considered as inert materials in the degradation process. Thus RPC matrices, and also a pure cement paste, and a cement and silica fume paste, were studied. The materials were characterised before and after a leaching test: microstructure by means of scanning electron microscopy, porosity, chemical and mineralogical composition, and diffusivity. A superficial degradation proceeds along a straight leaching front related to the dissolution of the remaining anhydrous cement silicates (C 3 S and C 2 S). The leaching of mineral species is controlled by the ionic diffusions from the material towards the aggressive solution. The degradation kinetics is proportional to the square root of time. As long as a sound core remains, the global behaviour of the partly degraded material is determined by the properties of the sound core. Two models related to the matrix transformation were used: DIFFU-Ca which characterised the leaching of calcium, and the 3D computer simulation of Portland cement hydration and microstructure development, from BENTZ and GARBOCZI. The digital results show a good agreement with the experimental values. This validates the hydration rates predicted with BENTZ and GARBOCZI and the phenomenology implemented in DIFFU-Ca. At the end of the study, it could be said that RPC appears as a suitable candidate for nuclear waste storage. The foreseen degradation depth after a 300 years leaching is about 1.4 cm in our

Durable fiber reinforced self-compacting concrete

International Nuclear Information System (INIS)

Corinaldesi, V.; Moriconi, G.

2004-01-01

In order to produce thin precast elements, a self-compacting concrete was prepared. When manufacturing these elements, homogenously dispersed steel fibers instead of ordinary steel-reinforcing mesh were added to the concrete mixture at a dosage of 10% by mass of cement. An adequate concrete strength class was achieved with a water to cement ratio of 0.40. Compression and flexure tests were carried out to assess the safety of these thin concrete elements. Moreover, serviceability aspects were taken into consideration. Firstly, drying shrinkage tests were carried out in order to evaluate the contribution of steel fibers in counteracting the high concrete strains due to a low aggregate-cement ratio. Secondly, the resistance to freezing and thawing cycles was investigated on concrete specimens in some cases superficially treated with a hydrophobic agent. Lastly, both carbonation and chloride penetration tests were carried out to assess durability behavior of this concrete mixture

Mechanical properties of polymer-modified porous concrete

Science.gov (United States)

Ariffin, N. F.; Jaafar, M. F. Md.; Shukor Lim, N. H. Abdul; Bhutta, M. A. R.; Hussin, M. W.

2018-04-01

In this research work, polymer-modified porous concretes (permeable concretes) using polymer latex and redispersible polymer powder with water-cement ratio of 30 %, polymer-cement ratios of 0 to 10 % and cement content of 300 kg/m3 are prepared. The porous concrete was tested for compressive strength, flexural strength, water permeability and void ratio. The cubes size of specimen is 100 mm ×100 mm × 100 mm and 150 mm × 150 mm × 150 mm while the beam size is 100 mm × 100 mm × 500 mm was prepared for particular tests. The tests results show that the addition of polymer as a binder to porous concrete gives an improvement on the strength properties and coefficient of water permeability of polymer-modified porous concrete. It is concluded from the test results that increase in compressive and flexural strengths and decrease in the coefficient of water permeability of the polymer-modified porous concrete are clearly observed with increasing of polymer-cement ratio.

Procedures and results from determining the rheological parameters of clay-cement mixtures

Energy Technology Data Exchange (ETDEWEB)

Dobrianskii, V G

1979-01-01

It is noted that there have to date existed no devices for determining the structural viscosity, and the dynamic shear stress, t/SUB o/, of grouting mortars in industrial conditions. The authors used the VSN 3 rotary viscometer in order to determine the rheological characteristics of the grouting mortars in use in the fields in the Srednii Priove; the LNR-1 mixer with a closed housing for temperature control was used to mix the test mortar. Mortars made from Volskii and Chernorechensk cements and Konstantinov concrete were examined. The rheological characteristics of the clay-cement mortars were tested both with a constant temperature and with one that varied over time. The acceptable accuracy of determining n and t/SUB o/ was 20%. A 20% deviation in the value n and t/SUB o/ from their acceptable mean values when determining the hydraulic fracturing pressure resulted in an error of 1.0%, which is insignificant. These results may be recommended for use in designing a cementation process.

"MTA"-an Hydraulic Silicate Cement: review update and setting reaction.

Science.gov (United States)

Darvell, B W; Wu, R C T

2011-05-01

To review the current status and understanding of Portland cement-like endodontic materials commonly referred to by the trade designation "MTA" (alias "Mineral Trioxide Aggregate"), and to present an outline setting reaction scheme, hitherto unattempted. The literature was searched using on-line tools, overlapping an earlier substantial review to pick up any omissions, including that in respect of ordinary Portland cement (OPC), with which MTA shares much. The search was conducted for the period January 2005 to December 2009 using 'MTA', 'GMTA', 'WMTA', and 'mineral AND trioxide AND aggregate' as keywords, with various on-line search engines including ScienceDirect (http://www.sciencedirect.com), SAGE Journals Online (http://online.sagepub.com), Wiley Online Library (http://onlinelibrary.wiley.com), SciELO Scientific electronic library online (http://www.scielo.br/scielo.php), JSTOR (http://www.jstor.org), and Scopus (http://www.scopus.com). References of articles found were cross-checked where appropriate for missed publications. Manufacturers' and related websites were searched with Google Search (http://www.google.com.hk). A generic name for this class of materials, Hydraulic Silicate Cement (HSC), is proposed, and an outline reaction scheme has been deduced. HSC has distinct advantages apparent, including sealing, sterilizing, mineralizing, dentinogenic and osteogenic capacities, which research continues to demonstrate. However, ad hoc modifications have little supporting justification. While HSC has a definite place in dentistry, with few of the drawbacks associated with other materials, some improvements in handling and other properties are highly desirable, as are studies of the mechanisms of the several beneficial physiological effects. Reference to the extensive, but complex, literature on OPC may provide the necessary insight. Copyright © 2011 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Recyclability of Concrete Pavement Incorporating High Volume of Fly Ash

Science.gov (United States)

Yoshitake, Isamu; Ishida, Takeo; Fukumoto, Sunao

2015-01-01

Recyclable concrete pavement was made from fly ash and crushed limestone sand and gravel as aggregates so that the concrete pavement could be recycled to raw materials for cement production. With the aim to use as much fly ash as possible for the sustainable development of society, while achieving adequate strength development, pavement concrete having a cement-replacement ratio of 40% by mass was experimentally investigated, focusing on the strength development at an early age. Limestone powder was added to improve the early strength; flexural strength at two days reached 3.5 MPa, the minimum strength for traffic service in Japan. The matured fly ash concrete made with a cement content of 200 kg/m3 achieved a flexural strength almost equal to that of the control concrete without fly ash. Additionally, Portland cement made from the tested fly ash concrete was tested to confirm recyclability, with the cement quality meeting the Japanese classification of ordinary Portland cement. Limestone-based recyclable fly ash concrete pavement is, thus, a preferred material in terms of sustainability. PMID:28793518

Recyclability of Concrete Pavement Incorporating High Volume of Fly Ash.

Science.gov (United States)

Yoshitake, Isamu; Ishida, Takeo; Fukumoto, Sunao

2015-08-21

Recyclable concrete pavement was made from fly ash and crushed limestone sand and gravel as aggregates so that the concrete pavement could be recycled to raw materials for cement production. With the aim to use as much fly ash as possible for the sustainable development of society, while achieving adequate strength development, pavement concrete having a cement-replacement ratio of 40% by mass was experimentally investigated, focusing on the strength development at an early age. Limestone powder was added to improve the early strength; flexural strength at two days reached 3.5 MPa, the minimum strength for traffic service in Japan. The matured fly ash concrete made with a cement content of 200 kg/m3 achieved a flexural strength almost equal to that of the control concrete without fly ash. Additionally, Portland cement made from the tested fly ash concrete was tested to confirm recyclability, with the cement quality meeting the Japanese classification of ordinary Portland cement. Limestone-based recyclable fly ash concrete pavement is, thus, a preferred material in terms of sustainability.

Comparative study of the properties of ordinary portland cement ...

African Journals Online (AJOL)

The study explored metakaolin as alternative material to cement. It compares the properties of Ordinary Portland Cement (OPC) concrete and binary concrete containing metakaolin as partial replacement of OPC. Two set of concrete samples; one with 10% Metakaolin (MK) replacing OPC by weight, and the other without ...

Early-age monitoring of cement structures using FBG sensors

Science.gov (United States)

Wang, Chuan; Zhou, Zhi; Zhang, Zhichun; Ou, Jinping

2006-03-01

With more and more broad applications of the cement-based structures such as neat cement paste, cement mortar and concrete in civil engineering, people hope to find out what their performances should like. The in-service performances of cement-based structures are highly affected by their hardening process during the early-age. But it is still a big problem for traditional sensors to be used to monitor the early curing of cement-based structures due to such disadvantages as difficulties to install sensors inside the concrete, limited measuring points, poor durability and interference of electromagnetic wave and so on. In this paper, according to the sensing properties of the Fiber Bragg Grating sensors and self-characters of the cement-based structures, we have successfully finished measuring and monitoring the early-age inner-strain and temperature changes of the neat cement paste, concrete with and without restrictions, mass concrete structures and negative concrete, respectively. Three types of FBG-based sensors have been developed to monitor the cement-based structures. Besides, the installation techniques and the embedding requirements of FBG sensors in cement-based structures are also discussed. Moreover, such kind of technique has been used in practical structure, 3rd Nanjing Yangtze Bridge, and the results show that FBG sensors are well proper for measuring and monitoring the temperature and strain changes including self-shrinkage, dry shrinkage, plastic shrinkage, temperature expansion, frost heaving and so on inside different cement-based structures. This technique provides us a new useful measuring method on early curing monitoring of cement-based structures and greater understanding of details of their hardening process.

Porous Structure of Road Concrete

OpenAIRE

Пшембаев, М. К.; Гиринский, В. В.; Ковалев, Я. Н.; Яглов, В. Н.; Будниченко, С. С.

2016-01-01

Having a great number of concrete structure classifications it is recommended to specify the following three principal types: microstructure – cement stone structure; mesostructure – structure of cement-sand mortar in concrete; macrostucture – two-component system that consists of mortar and coarse aggregate. Every mentioned-above structure has its own specific features which are related to the conditions of their formation. Thus, microstructure of cement stone can be characterized by such st...

Concrete Durability Properties and Microstructural Analysis of Cement Pastes with Nopal Cactus Mucilage as a Natural Additive

Directory of Open Access Journals (Sweden)

Ramírez-Arellanes, S.

2012-09-01

Full Text Available The present study evaluated the addition of a 3% nopal cactus mucilage solution to cement pastes, in its effects on setting times, flow, hydration, and microstructure, as well as on capillary water absorption and chloride diffusion in concrete. Hydration was characterized through XRD and microstructure was characterized with SEM. The mucilage solution/cement and water/cement ratios tested were 0.30, 0.45, and 0.60. The results in cement pastes indicate that the addition of mucilage increases setting times, reduces flow, slows cement hydration, and inhibits the formation of calcium hydroxide crystals in comparison with the control. Capillary absorption was significantly reduced in concrete containing mucilage, and chloride diffusion coefficients dropped up to 20% in the mixture with a mucilage/cement ratio = 0.30. The mixture with a mucilage/cement ratio = 0.45 displayed marginal reduction, and the mixture with mucilage/cement ratio = 0.60 exhibited a diffusion coefficient that was greater than the control for the specimens without moist curing.En esta investigación se evaluó el efecto de una solución de mucílago de nopal al 3% en los tiempos de fraguado, fluidez, hidratación y microestructura de pastas de cemento, y absorción capilar de agua y difusión de cloruros en concreto. La hidratación fue caracterizada por XRD y la microestructura por medio de SEM. Las relaciones solución de mucílago/cemento y agua/cemento fueron 0,30; 0,45 y 0,60. Los resultados en las pastas de cemento indican que el mucílago retarda los tiempos de fraguado, reduce la fluidez, retarda la hidratación del cemento, e inhibe la formación de cristales de hidróxido de calcio, comparados con los controles. La absorción capilar en concreto conteniendo mucílago se redujo significativamente y los coeficientes de difusión de cloruros disminuyeron hasta 20% en la mezcla mucílago/cemento = 0.30. En la relación mucílago/cemento = 0.45 la reducción fue marginal y

DETERMINATION OF ADHESIVE STRENGTH LAYER’S ROLLER COMPACTED CONCRETE THE METHOD AXIAL EXTENSION

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Tang Van Lam

2017-07-01

Full Text Available Roller compacted concrete for the construction of hydraulic and hydroelectric buildings is a composite material, which consists of a binder, fine aggregate (sand, coarse aggregate (gravel or crushed stone, water and special additives that provide the desired concrete workability and impart the required concrete performance properties. Concrete mixture is prepared at from concrete mixing plants strictly metered quantities of cement, water, additives and graded aggregates, whereupon they are delivered to the site laying Mixer Truck and sealing layers with each stack layer. The advantages of roller compaction technology should include the reduction of construction time, which allows fast commissioning construction projects, as well as reduce the amount of investment required. One of the main problems encountered in the process of roller compaction of the concrete mix is the need to provide the required adhesion strength between layers of concrete. This paper presents a method for determining the strength of adhesion between the concrete layers of different ages roller compacted concrete using axial tension. This method makes it possible to obtain objective and accurate results with a total thickness of layers of compacted concrete of up to 300…400 mm. Results from this method, studies have shown that the value of strength between the concrete layers in addition to the composition of the concrete and adhesion depends on the quality and the parallel end surfaces of the cylinder-models, which are mounted steel plates for axial tension, as well as the state of the contact surfaces of the concrete layer. The method can be used to determine the strength of interlayer adhesion in roller compacted concrete, which are used in the construction of dams and other hydraulic structures.

Compressive strength of different brands of cement (OPC) in province of Sindh

International Nuclear Information System (INIS)

Khaskheli, G.B.; Kumar, A.; Sheikh, A.

2009-01-01

OPC (Ordinary Portland Cement) is the most common type of cement used in construction industry. Three major brands of OPC are normal OPC, SRC (Sulphate Resisting Cement) and SC (Slag Cement). It is seen that the variation in constituents of cement may cause serious effects on the quality of cement. Thus the motivation of this research is to study the basic properties (consistency, setting time, and fineness), compressive strength (cement mortar and concrete cubes) and modulus of elasticity of all the OPC brands (OPC, SRC and SC) manufactured in Sindh. In total 10 cement factories, altogether 21 different brands of cement, were studied in the light of BS and ASTM Code specifications. In total 126 mortar cubes (1:3), 252 concrete cubes (126 for 3000 psi mix design and remaining for 5000 psi) and 126 concrete cylinders (6 for the each brand of cement pertaining to 3000 psi and 5000 psi mix design) were manufactured and tested. Experimental results demonstrated that all the cement brands fulfilled the BS and ASTM Code requirements for (i) basic properties (ii) compressive strength of mortar cubes at 3 and 28 days curing age (iii) compressive strength of concrete cubes at 28 days curing age, and (iv) modulus of elasticity. Some of the cements did not fulfill the BS and ASTM Code requirements for compressive strength of concrete cubes at 7 days curing age. (author)

Manufacturing of mortars and concretes non-traditionals, by Portland cement, metakaoline and gypsum (15.05%

Directory of Open Access Journals (Sweden)

Talero, R.

1999-12-01

Full Text Available In a thorough previous research (1, it appeared that creation, evolution and development of the values of compressive mechanical strength (CS and flexural strength (FS, measured in specimens 1x1x6cm of mortar type ASTM C 452-68 (2, manufactured by ordinary Portland cement P-1 (14.11% C₃A or PY-6 (0.00% C₃A, metakaolin and gypsum (CaSO₄∙2H₂O -or ternary cements, CT-, were similar to the ones commonly developed in mortars and concretes of OPC. This paper sets up the experimental results obtained from non-traditional mortars and concretes prepared with such ternary cements -TC-, being the portland cement/metakaolin mass ratio, as follows: 80/20, 70/30 and 60/40. Finally, the behaviour of these cements against gypsum attack, has been also determined, using the following parameters: increase in length (ΔL%, compressive, CS, and flexural, FS, strengths, and ultrasound energy, UE. Experimental results obtained from these non-traditional mortars and concretes, show an increase in length (ΔL, in CS and FS, and in UE values, when there is addition of metakaolin.

En una exhaustiva investigación anterior (1, se pudo comprobar que la creación, evolución y desarrollo de los valores de resistencias mecánicas a compresión, RMC, y flexotracción, RMF, proporcionados por probetas de 1x1x6 cm, de mortero 1:2,75, selenitoso tipo ASTM C 452-68 (2 -que habían sido preparadas con arena de Ottawa, cemento portland, P-1 (14,11% C₃A o PY- 6 (0,00% C₃A, metacaolín y yeso (CaSO₄∙2H₂O-, fue semejante a la que, comúnmente, desarrollan los morteros y hormigones tradicionales de cemento portland. En el presente trabajo se exponen los resultados experimentales obtenidos de morteros y hormigones no tradicionales, preparados con dichos cementos ternarios, CT, siendo las proporciones porcentuales en masa ensayadas, cemento portland/metacaolín, las siguientes: 80/20, 70

Self-flowing underwater concrete mixtures for high rise structures

International Nuclear Information System (INIS)

Yousri, K.M.

2005-01-01

Placement of conventional concrete mixtures in underwater construction results in a high percentage of material loss due to washout of cement paste. This paper presents the influence of anti washout admixture (AWA) on various properties of concrete. Eleven self-flowing concrete (SFC) mixtures using type II cement were proportioned. A combination of low water cement (w/c), high cement contents, anti washout admixtures, fly ash, and silica fume were used to enhance the resistance of fresh concrete to washout. The concrete mixtures proportioned to be highly flow able, self-leveling and cohesive. The water-cementitious materials ratios ranged between 0.356 and 0.392 which correspond a typical underwater concrete mixture. The concrete mixtures were tested for slump, slump flow, washout resistance and compressive strength. The compressive strength of each concrete mixture cast underwater was determined at 3, 7, 28 days and compared with the compressive strength of the same concrete mixture cast in normal condition (in air). Test results indicated that the use of an AWA facilitates the production of flow able concrete mixtures with the added benefit of lower washout loss. Concrete mixture proportioned using Type II cement and fly ash at level of replacement of 15% was found to develop self flowing concrete with better fresh and hardened properties and more resistant to washout. The self-flowing underwater concretes developed a 28-day compressive strengths ranging from 20 to 28 MPa

The influence of loading on the corrosion of steel in cracked ordinary Portland cement and high performance concretes

Science.gov (United States)

Jaffer, Shahzma Jafferali

Most studies that have examined chloride-induced corrosion of steel in concrete have focused on sound concrete. However, reinforced concrete is seldom uncracked and very few studies have investigated the influence of cracked concrete on rebar corrosion. Furthermore, the studies that have examined the relationship between cracks and corrosion have focused on unloaded or statically loaded cracks. However, in practice, reinforced concrete structures (e.g. bridges) are often dynamically loaded. Hence, the cracks in such structures open and close which could influence the corrosion of the reinforcing steel. Consequently, the objectives of this project were (i) to examine the effect of different types of loading on the corrosion of reinforcing steel, (ii) the influence of concrete mixture design on the corrosion behaviour and (iii) to provide data that can be used in service-life modelling of cracked reinforced concretes. In this project, cracked reinforced concrete beams made with ordinary Portland cement concrete (OPCC) and high performance concrete (HPC) were subjected to no load, static loading and dynamic loading. They were immersed in salt solution to just above the crack level at their mid-point for two weeks out of every four (wet cycle) and, for the remaining two weeks, were left in ambient laboratory conditions to dry (dry cycle). The wet cycle led to three conditions of exposure for each beam: (i) the non-submerged region, (ii) the sound, submerged region and (iii) the cracked mid-section, which was also immersed in the solution. Linear polarization resistance and galvanostatic pulse techniques were used to monitor the corrosion in the three regions. Potentiodynamic polarization, electrochemical current noise and concrete electrical resistance measurements were also performed. These measurements illustrated that (i) rebar corroded faster at cracks than in sound concrete, (ii) HPC was more protective towards the rebar than OPCC even at cracks and (iii) there

Chemistry of cements for nuclear applications

International Nuclear Information System (INIS)

Barrett, P.; Glasser, F.P.

1992-01-01

In recent times the nuclear industry has thrown up challenges which cannot be met by the application of conventional civil and materials engineering knowledge. The contributions in this volume investigate all aspects of cement performance. The scope of the papers demonstrates the current balance of activities which have as their objective the elucidation of kinetics and immobilization, determining material interactions and of assessing future performance. The papers reflect the varied goals of the sponsors who include national governments, the Commission of the European Communities and the nuclear industries. In six parts attention is paid to the durability of cement and concrete in repository environment; interactions between cement, waste components and ground water; properties and performance of cement materials; leach behavior and mechanisms, diffusional properties of cement and concrete, including porosity-permeability relationships; and thermodynamics of cementitious systems and modelling of cement performance

Influence of additives for concrete on the containment of radio-elements and strength under radiation of 'cement' matrices

International Nuclear Information System (INIS)

Pholvichith epouse Lezane, Ammala

1994-01-01

In order to improve the durability of cement-based materials used for the storage of radioactive wastes, fluidizers are generally introduced into these materials during their preparation. Thus, Naphtalene Sulfonate Formaldehyde (NSF) and Melamine Sulfonate Formaldehyde (MSF) are used as fluidizers in concrete which therefore presents good rheological properties when fresh, and a high compactness when hardened. This research study aims at investigating what happens to the fluidizer in a hardened cement paste, how this fluidizer affects the durability (mechanical strength, porosity, apparent diffusion coefficient) of a cement paste in absence of irradiation, what is the behaviour of these organic compounds under irradiation (reticulation or degradation, nature of radiolysis gases), how these organic compounds affects the durability (dimension, porosity, mechanical strength) of a cement paste under cobalt 60 gamma radiation, and how apparent solubilities of the different isotopes vary in cement water in presence of these organic compounds [fr

Waste-Based Pervious Concrete for Climate-Resilient Pavements.

Science.gov (United States)

Ho, Hsin-Lung; Huang, Ran; Hwang, Lih-Chuan; Lin, Wei-Ting; Hsu, Hui-Mi

2018-05-27

For the sake of environmental protection and circular economy, cement reduction and cement substitutes have become popular research topics, and the application of green materials has become an important issue in the development of building materials. This study developed green pervious concrete using water-quenched blast-furnace slag (BFS) and co-fired fly ash (CFFA) to replace cement. The objectives of this study were to gauge the feasibility of using a non-cement binder in pervious concrete and identify the optimal binder mix design in terms of compressive strength, permeability, and durability. For filled percentage of voids by cement paste (FPVs) of 70%, 80%, and 90%, which mixed with CFFA and BFS as the binder (40 + 60%, 50 + 50%, and 60 + 40%) to create pervious concrete with no cement. The results indicate that the complete (100%) replacement of cement with CFFA and BFS with no alkaline activator could induce hydration, setting, and hardening. After a curing period of 28 days, the compressive strength with different FPVs could reach approximately 90% that of the control cement specimens. The cementless pervious concrete specimens with BFS:CFFA = 7:3 and FPV = 90% presented better engineering properties and permeability.

Characterization of cement-based ancient building materials in support of repository seal materials studies

International Nuclear Information System (INIS)

Roy, D.M.; Langton, C.A.

1983-12-01

Ancient mortars and plasters collected from Greek and Cypriot structures dating to about 5500 BC have been investigated because of their remarkable durability. The characteristics and performance of these and other ancient cementitious materials have been considered in the light of providing information on longevity of concrete materials for sealing nuclear waste geological repositories. The matrices of these composite materials have been characterized and classified into four categories: (1) gypsum cements; (2) hydraulic hydrated lime and hydrated-lime cements; (3) hydraulic aluminous and ferruginous hydrated-lime cements (+- siliceous components); and (4) pozzolana/hydrated-lime cements. Most of the materials investigated, including linings of ore-washing basins and cisterns used to hold water, are in categories (2) and (3). The aggregates used included carbonates, sandstones, shales, schists, volcanic and pyroclastic rocks, and ore minerals, many of which represent host rock types of stratigraphic components of a salt repository. Numerous methods were used to characterize the materials chemically, mineralogically, and microstructurally and to elucidate aspects of both the technology that produced them and their response to the environmental exposure throughout their centuries of existence. Their remarkable properties are the result of a combination of chemical (mineralogical) and microstructural factors. Durability was found to be affected by matrix mineralogy, particle size and porosity, and aggregate type, grading, and proportioning, as well as method of placement and exposure conditions. Similar factors govern the potential for durability of modern portland cement-containing materials, which are candidates for repository sealing. 29 references, 29 figures, 6 tables

Optimum permeability for a cement based backfill material

International Nuclear Information System (INIS)

Jacobs, F.; Wittmann, F.H.; Iriya, K.

1989-01-01

In Switzerland it is planned to dispose low- and intermediate radioactive waste (LLW/ILW) in an underground repository. Between the materials present in a repository different chemical reactions may occur. Due to radiolytic decomposition, microbiological degradation and corrosion gas (mainly hydrogen) may be produced. The release of gas can cause the build-up of pressure in the cavern and finally lead to the formation of cracks and/or serious damage in the concrete structure or host rock. Through cracks a contamination of the groundwater and the biosphere could be possible. This investigation develops a suitable cement based material which can be used as backfill for the repository. Besides other aspects mentioned later a suitable backfill material has to be characterized by a certain minimum gas permeability and a as low as possible hydraulic conductivity. On the one hand gas permeability is necessary to release gas overpressure and on the other hand a low hydraulic conductivity should prevent leaching of backfill materials and contamination of the environment

physico-chemical studies on polymer impregnated blending cement mortar composite

International Nuclear Information System (INIS)

Abdel-Rahman, H.A.

2001-01-01

as the increasing of the demand on a specific performance characteristics in concrete such as improved strength, low heat, sulfate resistance, improved impermeability and certain other applications. some of the industrial waste materials such as the blast-furnace slag, silica fume and fly ash were mixed with the cement clinker to produce blended cement . the use of these materials modifies the strength, pore structure and permeability of hardened cement mortar or concrete. the incorporation of blast furnace slag and silica fume in the hardened blended cement mortar or concrete is a common practice recently due to technological, economical and environmental benefits

Experimental Analysis of Concrete Strength at High Temperatures and after Cooling

Directory of Open Access Journals (Sweden)

E. Klingsch

2009-01-01

Full Text Available In recent years, the cement industry has been criticized for emitting large amounts of carbon dioxide; hence it is developing environment-friendly cement, e.g., blended, supersulfated slag cement (SSC. This paper presents an experimental analysis of the compressive strength development of concrete made from blended cement in comparison to ordinary cement at high temperature. Three different types of cement were used during these tests, an ordinary portland cement (CEM I, a portland limestone cement (CEM II-A-LL and a new, supersulfated slag cement (SSC. The compressive strength development for a full thermal cycle, including cooling down phase, was investigated on concrete cylinders. It is shown that the SSC concrete specimens perform similar to ordinary cement specimens. 

Differences between silica and limestone concretes that may affect their interaction with corium

International Nuclear Information System (INIS)

Journeau, C.; Haquet, J. F.; Piluso, P.; Bonnet, J. M.

2008-01-01

Recent Molten Core Concrete Interaction tests performed at Argonne National Laboratory and at CEA Cadarache have shown that, whereas the ablation of limestone-rich concretes is almost isotropic, the ablation of silica-rich concretes is much faster towards the sides than towards the bottom of the cavity. The following differences exists between limestone-rich and silica-rich concretes: limestone concretes liberate about twice as much gas, at a given ablation rate than siliceous concretes (more than 50% more at constant heat flux) and this can affect pool hydraulics and crust stability: limestone concrete has a higher liquidus temperature than siliceous concrete and molten limestone concrete has a larger diffusion coefficient and can more easily dissolve a corium crust than siliceous melt; limestone aggregates are destroyed by de-carbonation at around 1000 K while silica aggregates melt only above 2000 K, so that floating silica aggregates can form cold spots increasing corium solidification near the interface; de-carbonation of limestone leads to a significant shrinkage of concrete melt volume compared to the cold solid that hampers the mechanical stability of overlying crusts; the chemical composition of molten mortar (sand + cement) and concrete (sand + gravel + cement) is close for limestone-rich concretes while it is different for siliceous concretes, so that the melt composition may vary significantly in case of non-simultaneous melting of the siliceous concrete constituents; molten silicates have a large viscosity, so that transport properties are different for the two types of concretes. The small range of plant concrete compositions that have been considered for MCCI experiments has not yet been found sufficient to determine which of the above-mentioned differences is paramount to explain the observed difference in ablation patterns. Separate Effect Tests using specially-designed 'artificial concretes' and prototypic corium would provide the necessary

Lignin-based cement fluid loss control additive

Energy Technology Data Exchange (ETDEWEB)

Schilling, P.

1990-05-22

This patent describes a hydraulic cement slurry composition. It comprises: a hydraulic cement, and the following expressed as parts by weight per 100 parts of the hydraulic cement, water from about 25 to 105 parts, and from abut 0.5 to 2.5 parts of a compound selected from the group consisting of a sulfonated lignin and a sulfomethylated lignin, wherein the lignin has been sequentially crosslinked by reacting the lignin with a member of the group consisting of formaldehyde and epichlorohydrin and alkoxylated with between about 2 to about 6 moles of a compound selected from the group consisting of ethylene oxide, propylene oxide, butylene oxide and a combination thereof per 1000 g of the lignin.

Self-curing concrete with different self-curing agents

Science.gov (United States)

Gopala krishna sastry, K. V. S.; manoj kumar, Putturu

2018-03-01

Concrete is recognised as a versatile construction material globally. Properties of concrete depend upon, to a greater extent, the hydration of cement and microstructure of hydrated cement. Congenial atmosphere would aid the hydration of cement and hence curing of concrete becomes essential, till a major portion of the hydration process is completed. But in areas of water inadequacy and concreting works at considerable heights, curing is problematic. Self-Curing or Internal Curing technique overcomes these problems. It supplies redundant moisture, for more than sufficient hydration of cement and diminish self-desiccation. Self-Curing agents substantially help in the conservation of water in concrete, by bringing down the evaporation during the hydration of Concrete. The present study focuses on the impact of self-curing agents such as Poly Ethylene Glycol (PEG), Poly Vinyl Alcohol (PVA) and Super Absorbent Polymer (SAP) on the concrete mix of M25 grade (reference mix). The effect of these agents on strength properties of Concrete such as compressive strength, split tensile strength and flexural strength was observed on a comparative basis which revealed that PEG 4000 was the most effective among all the agents.

Long-Term and Seismic Performance of Concrete-Filled Steel Tube Columns with Conventional and High-Volume SCM Concrete

Science.gov (United States)

2012-06-01

Production of Portland Cement for concrete is a major source of CO2 emission. Concrete can be made more sustainable by replacing a large volume of the cement with Supplementary Cementitous Materials (SCMs) such as fly ash and slag. The amount of ceme...

Utilization of cement treated recycled concrete aggregates as base or subbase layer in Egypt

Directory of Open Access Journals (Sweden)

Ahmed Ebrahim Abu El-Maaty Behiry

2013-12-01

Full Text Available Recently, environmental protection has a great concern in Egypt where recycling of increased demolition debris has become a viable option to be incorporated into roads applications. An extensive laboratory program is conducted to study the feasibility of using recycled concrete aggregate (RCA mixed with traditional limestone aggregate (LSA which is currently being used in base or subbase applications in Egypt. Moreover, the influence of mixture variables on the mechanical properties of cement treated recycled aggregate (CTRA is investigated. Models to predict the compressive and tensile strengths based on mixture parameters are established. The results show that the adding of RCA improves the mechanical properties of the mixture where the unconfined compressive strength (UCS is taken as an important quality indicator. Variables influencing the UCS such as cement content, curing time, dry density play important roles to determine the performance of CTRA.

Comparison of physical and mechanical properties of river sand concrete with quarry dust concrete

Science.gov (United States)

Opara, Hyginus E.; Eziefula, Uchechi G.; Eziefula, Bennett I.

2018-03-01

This study compared the physical and mechanical properties of river sand concrete with quarry dust concrete. The constituent materials were batched by weight. The water-cement ratio and mix ratio selected for the experimental investigation were 0.55 and 1:2:4, respectively. The specimens were cured for 7, 14, 21 and 28 days. Slump, density and compressive strength tests were carried out. The results showed that river sand concrete had greater density and compressive strength than quarry dust concrete for all curing ages. At 28 days of curing, river sand concrete exceeded the target compressive strength by 36%, whereas quarry dust concrete was less than the target compressive strength by 12%. Both river sand concrete and quarry dust concrete for the selected water/cement ratio and mix ratio are suitable for non-structural applications and lightly-loaded members where high strength is not a prerequisite.

The shrinkage of hardening cement paste and mortar

NARCIS (Netherlands)

Haas, de G.D.; Kreijger, P.C.; Niël, E.M.M.G.; Slagter, J.C.; Stein, H.N.; Theissing, E.M.; Wallendael, van M.

1975-01-01

This paper is an abstract from the report of the commission B10: "The influence of the shrinkage of cement on the shrink-age of concrete", of the Netherlands Committee for Concrete Research. Measurements of pulse velocity, volume shrinkage and heat of hydration on hardening portland cement support

Technology for reuse of contaminated concrete constituents

International Nuclear Information System (INIS)

Binkhorst, I.P.; Cornelissen, H.A.W.

1998-01-01

During decommissioning activities of nuclear installations, large amounts of contaminated concrete will have to be processed. All this concrete has to be treated and stored as radioactive waste, which implies major economical and environmental consequences. It was shown that the contamination is mainly concentrated in the porous cement stone. By separating this cement stone from the clean dense aggregate particles, a considerable volume reduction can be reached. KEMA has developed, designed and constructed a pilot plant scale test installation for separation of aggregate from contaminated concrete. The separation is based on a thermal treatment followed by milling and sieving. The clean aggregate can be re-used in concrete, whereas the (slightly) contaminated cement stone could be upgraded to a binder for concrete used in the nuclear industry. (author)

Automated Detection of Alkali-silica Reaction in Concrete using Linear Array Ultrasound Data

Energy Technology Data Exchange (ETDEWEB)

Santos-Villalobos, Hector J [ORNL; Clayton, Dwight A [ORNL; Ezell, N Dianne Bull [ORNL; Clayton, Joseph A [ORNL; Baba, Justin S [ORNL

2017-01-01

Alkali-silica reaction (ASR) is a chemical reaction in either concrete or mortar between hydroxyl ions of the alkalis (sodium and potassium) from hydraulic cement (or other sources), and certain siliceous minerals present in some aggregates. The reaction product, an alkali-silica gel, is hygroscopic having a tendency to absorb water and swell, which under certain circumstances, leads to abnormal expansion and cracking of the concrete. This phenomenon affects the durability and performance of concrete structures severely since it can cause significant loss of mechanical properties. Developing reliable methods and tools that can evaluate the degree of the ASR damage in existing structures, so that informed decisions can be made toward mitigating ASR progression and damage, is important to the long term operation of nuclear power plants especially if licenses are extended beyond 60 years. This paper examines an automated method of determining the extent of ASR damage in fabricated concrete specimens.

Life Cycle Assessment of Concrete

Energy Technology Data Exchange (ETDEWEB)

Sjunnesson, Jeannette

2005-09-15

This is an environmental study on concrete that follows the standard protocol of life cycle assessment (LCA). The study is done for two types of concrete, ordinary and frost-resistant concrete, and has an extra focus on the superplasticizers used as admixtures. The utilization phase is not included in this study since the type of construction for which the concrete is used is not defined and the concrete is assumed to be inert during this phase. The results show that it is the production of the raw material and the transports involved in the life cycle of concrete that are the main contributors to the total environmental load. The one single step in the raw material production that has the highest impact is the production of cement. Within the transportation operations the transportation of concrete is the largest contributor, followed by the transportation of the cement. The environmental impact of frost-resistant concrete is between 24-41 % higher than that of ordinary concrete due to its higher content of cement. Superplasticizers contribute with approximately 0.4-10.4 % of the total environmental impact of concrete, the least to the global warming potential (GWP) and the most to the photochemical ozone creation potential (POCP). Also the toxicity of the superplasticizers is investigated and the conclusion is that the low amount of leakage of superplasticizers from concrete leads to a low risk for the environment and for humans.

The use of steel slag in concrete

Science.gov (United States)

Martauz, P.; Vaclavik, V.; Cvopa, B.

2017-10-01

This paper presents the results of a research dealing with the use of unstable steel slag as a 100% substitute for natural aggregate in the production of concrete. Portland cement CEM I 42.5N and alkali activated hybrid cement H-CEMENT were used as the binder. The test results confirm the possibility to use steel slag as the filler in the production of concrete.

Innovative process routes for a high-quality concrete recycling in the aggregates and cement industries

OpenAIRE

Bru , Kathy; Menard , Yannick; Touzé , Solène; Le Moign , Alain; Poirier , Jean Eric; Ruffié , Gilles; Bonnaudin , Fabrice; Von Der Weid , Frédéric

2011-01-01

International audience; Hardened concrete is a composite material that contains two main phases: the matrix (hardened cement paste, 20 %) and aggregates (gravels and sand, 80 %). The liberation and the recycling of these constituents can provide an answer to i) the exploration of new aggregates supply sources imposed by the depletion of natural deposit and the faced difficulties when trying to open new quarries and ii) the reduction of CO2 emissions in the clinker manufacturing process throug...

Shape Effect of Electrochemical Chloride Extraction in Structural Reinforced Concrete Elements Using a New Cement-Based Anodic System

Directory of Open Access Journals (Sweden)

Jesús Carmona

2015-05-01

Full Text Available This article shows the research carried out by the authors focused on how the shape of structural reinforced concrete elements treated with electrochemical chloride extraction can affect the efficiency of this process. Assuming the current use of different anode systems, the present study considers the comparison of results between conventional anodes based on Ti-RuO2 wire mesh and a cement-based anodic system such as a paste of graphite-cement. Reinforced concrete elements of a meter length were molded to serve as laboratory specimens, to closely represent authentic structural supports, with circular and rectangular sections. Results confirm almost equal performances for both types of anode systems when electrochemical chloride extraction is applied to isotropic structural elements. In the case of anisotropic ones, such as rectangular sections with no uniformly distributed rebar, differences in electrical flow density were detected during the treatment. Those differences were more extreme for Ti-RuO2 mesh anode system. This particular shape effect is evidenced by obtaining the efficiencies of electrochemical chloride extraction in different points of specimens.

Shape Effect of Electrochemical Chloride Extraction in Structural Reinforced Concrete Elements Using a New Cement-Based Anodic System

Science.gov (United States)

Carmona, Jesús; Climent, Miguel-Ángel; Antón, Carlos; de Vera, Guillem; Garcés, Pedro

2015-01-01

This article shows the research carried out by the authors focused on how the shape of structural reinforced concrete elements treated with electrochemical chloride extraction can affect the efficiency of this process. Assuming the current use of different anode systems, the present study considers the comparison of results between conventional anodes based on Ti-RuO2 wire mesh and a cement-based anodic system such as a paste of graphite-cement. Reinforced concrete elements of a meter length were molded to serve as laboratory specimens, to closely represent authentic structural supports, with circular and rectangular sections. Results confirm almost equal performances for both types of anode systems when electrochemical chloride extraction is applied to isotropic structural elements. In the case of anisotropic ones, such as rectangular sections with no uniformly distributed rebar, differences in electrical flow density were detected during the treatment. Those differences were more extreme for Ti-RuO2 mesh anode system. This particular shape effect is evidenced by obtaining the efficiencies of electrochemical chloride extraction in different points of specimens.

Ultra high performance concrete dematerialization study

Energy Technology Data Exchange (ETDEWEB)

NONE

2004-03-01

Concrete is the most widely used building material in the world and its use is expected to grow. It is well recognized that the production of portland cement results in the release of large amounts of carbon dioxide, a greenhouse gas (GHG). The main challenge facing the industry is to produce concrete in an environmentally sustainable manner. Reclaimed industrial by-proudcts such as fly ash, silica fume and slag can reduce the amount of portland cement needed to make concrete, thereby reducing the amount of GHGs released to the atmosphere. The use of these supplementary cementing materials (SCM) can also enhance the long-term strength and durability of concrete. The intention of the EcoSmart{sup TM} Concrete Project is to develop sustainable concrete through innovation in supply, design and construction. In particular, the project focuses on finding a way to minimize the GHG signature of concrete by maximizing the replacement of portland cement in the concrete mix with SCM while improving the cost, performance and constructability. This paper describes the use of Ductal{sup R} Ultra High Performance Concrete (UHPC) for ramps in a condominium. It examined the relationship between the selection of UHPC and the overall environmental performance, cost, constructability maintenance and operational efficiency as it relates to the EcoSmart Program. The advantages and challenges of using UHPC were outlined. In addition to its very high strength, UHPC has been shown to have very good potential for GHG emission reduction due to the reduced material requirements, reduced transport costs and increased SCM content. refs., tabs., figs.

Production and construction technology of C100 high strength concrete filled steel tube

Science.gov (United States)

Wu, Yanli; Sun, Jinlin; Yin, Suhua; Liu, Yu

2017-10-01

In this paper, the effect of the amount of cement, water cement ratio and sand ratio on compressive strength of C100 concrete was studied. The optimum mix ratio was applied to the concrete filled steel tube for the construction of Shenyang Huangchao Wanxin mansion. The results show that the increase of amount of cement, water cement ratio can improve the compressive strength of C100 concrete but increased first and then decreased with the increase of sand ratio. The compressive strength of C100 concrete can reach 110MPa with the amount of cement 600kg/m3, sand ratio 40% and water cement ratio 0.25.

Influence of Recycled Concrete Dust on the Properties of Self– Compacting Concrete (SCC)

OpenAIRE

Ivanauskas, Ernestas; Lazauskas, Mantas; Grigaliūnas, Paulius

2017-01-01

Concrete – composite material which economical effect mostly depends on the amount of binder material (usually cement), its type and fineness. Cement manufacturing generates great employment of energy resources. The demand for all kind of manufacturing natural resources are aimed to be reduced as much as possible. Alternative raw material resources are being introduced and tested together with increasing self-compacting concrete (SCC) popularity in Lithuania. Considering environmental require...

Influence of interface properties on fracture behaviour of concrete

Indian Academy of Sciences (India)

Hardened concrete is a three-phase composite consisting of cement paste, aggregate and interface between cement paste and aggregate. The interface in concrete plays a key role on the overall performance of concrete. The interface properties such as deformation, strength, fracture energy, stress intensity and its ...

Life Cycle Assessment of Completely Recyclable Concrete.

Science.gov (United States)

De Schepper, Mieke; Van den Heede, Philip; Van Driessche, Isabel; De Belie, Nele

2014-08-21

Since the construction sector uses 50% of the Earth's raw materials and produces 50% of its waste, the development of more durable and sustainable building materials is crucial. Today, Construction and Demolition Waste (CDW) is mainly used in low level applications, namely as unbound material for foundations, e.g., in road construction. Mineral demolition waste can be recycled as crushed aggregates for concrete, but these reduce the compressive strength and affect the workability due to higher values of water absorption. To advance the use of concrete rubble, Completely Recyclable Concrete (CRC) is designed for reincarnation within the cement production, following the Cradle-to-Cradle (C2C) principle. By the design, CRC becomes a resource for cement production because the chemical composition of CRC will be similar to that of cement raw materials. If CRC is used on a regular basis, a closed concrete-cement-concrete material cycle will arise, which is completely different from the current life cycle of traditional concrete. Within the research towards this CRC it is important to quantify the benefit for the environment and Life Cycle Assessment (LCA) needs to be performed, of which the results are presented in a this paper. It was observed that CRC could significantly reduce the global warming potential of concrete.

Life Cycle Assessment of Completely Recyclable Concrete

Directory of Open Access Journals (Sweden)

Mieke De Schepper

2014-08-01

Full Text Available Since the construction sector uses 50% of the Earth’s raw materials and produces 50% of its waste, the development of more durable and sustainable building materials is crucial. Today, Construction and Demolition Waste (CDW is mainly used in low level applications, namely as unbound material for foundations, e.g., in road construction. Mineral demolition waste can be recycled as crushed aggregates for concrete, but these reduce the compressive strength and affect the workability due to higher values of water absorption. To advance the use of concrete rubble, Completely Recyclable Concrete (CRC is designed for reincarnation within the cement production, following the Cradle-to-Cradle (C2C principle. By the design, CRC becomes a resource for cement production because the chemical composition of CRC will be similar to that of cement raw materials. If CRC is used on a regular basis, a closed concrete-cement-concrete material cycle will arise, which is completely different from the current life cycle of traditional concrete. Within the research towards this CRC it is important to quantify the benefit for the environment and Life Cycle Assessment (LCA needs to be performed, of which the results are presented in a this paper. It was observed that CRC could significantly reduce the global warming potential of concrete.

Wide-scale utilization of MSWI fly ashes in cement production and its impact on average heavy metal contents in cements: The case of Austria.

Science.gov (United States)

Lederer, Jakob; Trinkel, Verena; Fellner, Johann

2017-02-01

A number of studies present the utilization of fly ashes from municipal solid waste incineration (MSWI) in cement production as a recycling alternative to landfilling. While there is a lot of research on the impact of MSWI fly ashes utilization in cement production on the quality of concrete or the leaching of heavy metals, only a few studies have determined the resulting heavy metal content in cements caused by this MSWI fly ashes utilization. Making use of the case of Austria, this study (1) determines the total content of selected heavy metals in cements currently produced in the country, (2) designs a scenario and calculates the resulting heavy metal contents in cements assuming that all MSWI fly ashes from Austrian grate incinerators were used as secondary raw materials for Portland cement clinker production and (3) evaluates the legal recyclability of demolished concretes produced from MSWI fly ash amended cements based on their total heavy metal contents. To do so, data from literature and statistics are combined in a material flow analysis model to calculate the average total contents of heavy metals in cements and in the resulting concretes according to the above scenario. The resulting heavy metal contents are then compared (i) to their respective limit values for cements as defined in a new technical guideline in Austria (BMLFUW, 2016), and (ii) to their respective limit values for recycling materials from demolished concrete. Results show that MSWI fly ashes utilization increases the raw material input in cement production by only +0.9%, but the total contents of Cd by +310%, and Hg, Pb, and Zn by +70% to +170%. However these and other heavy metal contents are still below their respective limit values for Austrian cements. The same legal conformity counts for recycling material derived from concretes produced from the MSWI fly ash cements. However, if the MSWI fly ash ratio in all raw materials used for cement production were increased from 0.9% to 22

Relating the Electrical Resistance of Fresh Concrete to Mixture Proportions.

Science.gov (United States)

Obla, K; Hong, R; Sherman, S; Bentz, D P; Jones, S Z

2018-01-01

Characterization of fresh concrete is critical for assuring the quality of our nation's constructed infrastructure. While fresh concrete arriving at a job site in a ready-mixed concrete truck is typically characterized by measuring temperature, slump, unit weight, and air content, here the measurement of the electrical resistance of a freshly cast cylinder of concrete is investigated as a means of assessing mixture proportions, specifically cement and water contents. Both cement and water contents influence the measured electrical resistance of a sample of fresh concrete: the cement by producing ions (chiefly K + , Na + , and OH - ) that are the main source of electrical conduction; and the water by providing the main conductive pathways through which the current travels. Relating the measured electrical resistance to attributes of the mixture proportions, such as water-cement ratio by mass ( w/c ), is explored for a set of eleven different concrete mixtures prepared in the laboratory. In these mixtures, w/c , paste content, air content, fly ash content, high range water reducer dosage, and cement alkali content are all varied. Additionally, concrete electrical resistance data is supplemented by measuring the resistivity of its component pore solution obtained from 5 laboratory-prepared cement pastes with the same proportions as their corresponding concrete mixtures. Only measuring the concrete electrical resistance can provide a prediction of the mixture's paste content or the product w*c ; conversely, when pore solution resistivity is also available, w/c and water content of the concrete mixture can be reasonably assessed.

Analysis of Chemical Composition of Portland Cement in Ghana: A Key to Understand the Behavior of Cement

OpenAIRE

Bediako, Mark; Amankwah, Eric Opoku

2015-01-01

The performance of Portland cement in concrete or mortar formation is very well influenced by chemical compositions among other factors. Many engineers usually have little information on the chemical compositions of cement in making decisions for the choice of commercially available Portland cement in Ghana. This work analyzed five different brands of Portland cement in Ghana, namely, Ghacem ordinary Portland cement (OPC) and Portland limestone cement (PLC), CSIR-BRRI Pozzomix, Dangote OPC, a...

New developments with respect to concrete

OpenAIRE

Brouwers, H.J.H.; Al-Mattarneh, H.; Mustapha, K.N.; Nuruddin, M.F.

2008-01-01

The present paper addresses several topics in regard to the sustainable design and use of concrete based on the binders cement, quicklime and/or gypsum. First, major features concerning the sustainable aspects of the material concrete are summarized. Then the major constituent, from an environmental point of view, cement is discussed in detail, particularly the hydration and application of slag cement. The intelligent combining of mineral oxides, which are found in clinker, slag, fly ashes et...

The cause and influence of self-cementing properties of fine recycled concrete aggregates on the properties of unbound sub-base

International Nuclear Information System (INIS)

Poon, C.-S.; Qiao, X.C.; Chan, Dixon

2006-01-01

The use of coarse recycled concrete aggregates (CRCA) in conjunction with fine recycled concrete aggregates (FRCA) as sub-base materials has been widely studied. Although research results indicate that it is feasible to employ both CRCA and FRCA as granular sub-base, the influence of the unhydrated cement in the adhered mortar of the RCA on the properties of the sub-base materials has not been thoroughly studied. Generally, it is known that the strength of the sub-base materials prepared with RCA increases over time. However, this mechanism, known as the self-cementing properties, is not well understood and is believed to be governed by the properties of the fine portion of the RCA (<5 mm). This paper presents an investigation on the cause of the self-cementing properties by measuring X-ray diffraction patterns, pH values, compressive strength and permeability of various size fractions of the FRCA obtained from a commercially operated construction and demolition waste recycling plant. Their influence on the overall sub-base materials was determined. The results indicate that the size fractions of <0.15 and 0.3-0.6 mm (active fractions) were most likely to be the principal cause of the self-cementing properties of the FRCA. However, the effects on the properties of the overall RCA sub-base materials were minimal if the total quantity of the active fractions was limited to a threshold by weight of the total fine aggregate

Modified water-cement ratio law for compressive strength of rice ...

African Journals Online (AJOL)

This work examines the modification of age long water – cement ratio law of Ordinary Portland Cement (OPC) concrete to cater for concrete with Rice Husk Ash (RHA). Chemical analysis of RHA produced under controlled temperature of 600°C was carried out. A total of one hundred and fifty (150) RHA concrete cubes at ...

Flow and granular analysis of cement paste with Nano-silica (nS): from macro to nano concrete design

NARCIS (Netherlands)

Quercia Bianchi, G.; Brouwers, H.J.H.; Hüsken, G.

2010-01-01

Current micro-silica is only applied in special cases, due to its high price, and nano-silica is not used in practice yet. The new nano-silica can be produced in such quantities and for low prices that mass application in concrete is within reach. It may replace cement in the mix, which is the most

Study of local Agregate for Gamma radiation concrete shield

International Nuclear Information System (INIS)

Tochrul-Binowo; Endro-Kismolo; Darsono

1996-01-01

Investigation on the composition of gamma radiation concrete shield made of local barite, manganese fine and coarse aggregates from Kulon Progo, Yogyakarta has been done. The purpose of the research was to find out the quality of these local material for an aggregate of gamma radiation concrete shield. The research was done where each mineral was used as coarse aggregate and the fine aggregate from Kulon Progo was used as fine basic aggregate. Firstly a normal concrete was made by mixing cement, fine aggregate, coarse aggregate and water at a weight ratio of cement: fine aggregate: coarse: water 1: 2.304: 3.456: 0.58. The gamma radiation absorption capacity of the concrete tested by using Cs-137 as source standard. The same method was done on barite concrete at the weight ratio of cement: fine aggregate: barite aggregate: water 1: 2.303: 3.456: 0.58 and manganese concrete at the weight ratio of cement: fine aggregate: manganese aggregate: and water 1: 1.896: 2.844: 0.58. The result of the study showed that the gamma radiation absorption capacity of barite aggregate was greater than that of normal concrete and manganese concrete. The coefficient linear attenuation (for 6.0 cm thickness) of each concrete were μ barite concrete = 0.23071 cm -1 , μ manganese concrete = 0.08401 cm -1 and μ normal concrete = 0.1669 cm -1

Evaluation of the suitability for concrete using fly ash in N.P.P. structures

International Nuclear Information System (INIS)

Cho, M. S.; Song, Y. C.; Kim, S. W.; Ko, K. T.

2002-01-01

The nuclear power plant structures constructed in Korea has been generally used type V cement(sulfate-resisting Portland cement), but according to the study results reported recently, it shows that type V cement is superior the resistance of sulfate attack, but the resistance of salt damage is weaker than type I cement. It is increased the demands on the use of mineral admixtures such as fly ash, ground granulated blast-furnace slag instead of type V cement in order to improve the durability of concrete structures. But the study on concrete mixed with fly ash in Korea has been mainly performed on rheology and strength properties of the concrete. Therefore, this study is to improve the durability of concrete structures of N.P.P. as using fly ash cement instead of type V cement. As a results, the concrete containing fly ash is improved the resistance to salt attack, sulfate attack and freezing-thawing and is deteriorated the carbonation. But if it is used the concrete with high strength or low water-powder ratio, the concrete have not problem on the durability

Effect of silica fume addition on the PGNAA measurement of chlorine in concrete

International Nuclear Information System (INIS)

Naqvi, A.A.; Maslehuddin, M.; Garwan, M.A.; Nagadi, M.M.; Al-Amoudi, O.S.B.; Raashid, M.; Khateeb-ur-Rehman

2010-01-01

Pozzolanic materials, such as fly ash (FA), silica fume (SF), and blast furnace slag (BFS) are added to Portland cement in concrete to prevent reinforcement steel corrosion in concrete. Further preventive measure against reinforcement steel corrosion require monitoring of chloride salts concentration in concrete using non-destructive techniques, such as the prompt gamma-ray neutron activation analysis (PGNAA) technique. Due to interferences between gamma-rays from chlorine and calcium in PGNAA technique, detection limit of chlorine in concrete strongly depends upon calcium concentration in concrete. SF mainly contains silica and its addition to cement concrete reduces overall concentration of calcium in concrete. This may result in an improvement in detection limit of chlorine in SF-based concrete in PGNAA studies. Particularly for chlorine detection using 6.11 and 6.62 MeV prompt gamma-rays that strongly interfere with 6.42 MeV prompt gamma-rays from calcium. In this study, SF was added to Portland cement to prevent concrete reinforcement steel from corrosion. The chlorine concentration in SF cement concrete specimens containing 0.2-3.0 wt% chlorine was measured through yield of 1.16, 1.95, 6.11, 6.62, 7.41, 7.79, and 8.58 MeV chlorine gamma-rays using PGNAA technique. An excellent agreement was noted between the experimental yield of the prompt gamma-rays and the gamma-ray yield calculated through the Monte Carlo simulations. Further the minimum detectable concentration (MDC) of chlorine in SF cement concrete was calculated and compared with the MDC values of chlorine in plain concrete and concrete mixed with fly ash cement. The MDC of chlorine in SF-based concrete through 6.11 MeV, and 6.62 MeV chlorine gamma-rays was found to be improved as compared to those in plain concrete and concrete mixed with fly ash cement.

Effect of silica fume addition on the PGNAA measurement of chlorine in concrete

Energy Technology Data Exchange (ETDEWEB)

Naqvi, A.A. [Department of Physics, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia)], E-mail: aanaqvi@kfupm.edu.sa; Maslehuddin, M. [Center for Engineering Research, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia); Garwan, M.A. [Department of Physics, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia); Nagadi, M.M. [Center for Engineering Research, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia); Al-Amoudi, O.S.B. [Department of Civil Engineering, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia); Raashid, M.; Khateeb-ur-Rehman [Department of Physics, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia)

2010-03-15

Pozzolanic materials, such as fly ash (FA), silica fume (SF), and blast furnace slag (BFS) are added to Portland cement in concrete to prevent reinforcement steel corrosion in concrete. Further preventive measure against reinforcement steel corrosion require monitoring of chloride salts concentration in concrete using non-destructive techniques, such as the prompt gamma-ray neutron activation analysis (PGNAA) technique. Due to interferences between gamma-rays from chlorine and calcium in PGNAA technique, detection limit of chlorine in concrete strongly depends upon calcium concentration in concrete. SF mainly contains silica and its addition to cement concrete reduces overall concentration of calcium in concrete. This may result in an improvement in detection limit of chlorine in SF-based concrete in PGNAA studies. Particularly for chlorine detection using 6.11 and 6.62 MeV prompt gamma-rays that strongly interfere with 6.42 MeV prompt gamma-rays from calcium. In this study, SF was added to Portland cement to prevent concrete reinforcement steel from corrosion. The chlorine concentration in SF cement concrete specimens containing 0.2-3.0 wt% chlorine was measured through yield of 1.16, 1.95, 6.11, 6.62, 7.41, 7.79, and 8.58 MeV chlorine gamma-rays using PGNAA technique. An excellent agreement was noted between the experimental yield of the prompt gamma-rays and the gamma-ray yield calculated through the Monte Carlo simulations. Further the minimum detectable concentration (MDC) of chlorine in SF cement concrete was calculated and compared with the MDC values of chlorine in plain concrete and concrete mixed with fly ash cement. The MDC of chlorine in SF-based concrete through 6.11 MeV, and 6.62 MeV chlorine gamma-rays was found to be improved as compared to those in plain concrete and concrete mixed with fly ash cement.

Influence of superplasticizers on the long-term properties of cement pastes and possible impact on radionuclide uptake in a cement-based repository for radioactive waste

International Nuclear Information System (INIS)

Wieland, E.; Lothenbach, B.; Glaus, M.A.; Thoenen, T.; Schwyn, B.

2014-01-01

Highlights: • We investigate the hydration of different cement mixes containing concrete admixtures. • The concentration of concrete admixtures decreases with time due to sorption on cement phases. • We observe no influence on the phase composition of cement paste and the ion composition of pore fluids. • Uptake of 63 Ni, 152 Eu and 228 Th by cement paste is not affected by the concrete admixtures. - Abstract: Cementitious materials will be used for the construction of the engineered barrier of the planned repositories for radioactive waste in Switzerland. Superplasticizers (SPs) are commonly used to improve the workability of concretes and, along with a set accelerator (Acc), to produce shotcrete. In this study the influence of a polycarboxylate- (PCE) and a polynaphthalene-sulphonate-based (PNS) SP on the hydration process, mineral composition and the sorption behaviour of metal cations has been investigated using an ordinary Portland cement (OPC), a low-alkali cement mix (LAC) consisting of CEM III-type cement and nanosilica, and a shotcrete-type cement mix (ESDRED) consisting of a CEM I-type cement and silica fume prepared in the presence of an alkali-free set accelerator. Both the PCE and PNS SP do not significantly influence the amount and quantity of hydrates formed during hydration. The concentration of both SPs decreased rapidly in the early stage of the hydration process for all cements due to sorption onto cement phases. After 28 days of hydration and longer, the concentration of the PNS SP in the pore fluids of all cements was generally lower than that of the PCE SP, indicating stronger uptake of the PNS SP. The formate present in the Acc sorbs only weakly onto the cement phases, which led to higher aqueous concentration of organics in the ESDRED cement than in OPC and LAC. Sorption experiments with 63 Ni, 152 Eu and 228 Th on a cation exchange resin indicate that, at concentrations above 0.1 g L −1 , the two SPs could reduce sorption of metal

DECISION MAKING MODELING OF CONCRETE REQUIREMENTS

Directory of Open Access Journals (Sweden)

Suhartono Irawan

2001-01-01

Full Text Available This paper presents the results of an experimental evaluation between predicted and practice concrete strength. The scope of the evaluation is the optimisation of the cement content for different concrete grades as a result of bringing the target mean value of tests cubes closer to the required characteristic strength value by reducing the standard deviation. Abstract in Bahasa Indonesia : concrete+mix+design%2C+acceptance+control%2C+optimisation%2C+cement+content.

Experimental Analysis on Shrinkage and Swelling in Ordinary Concrete

Directory of Open Access Journals (Sweden)

Barbara Kucharczyková

2017-01-01

Full Text Available The paper deals with the experimental determination of shrinkage development during concrete ageing. Three concrete mixtures were made. They differed in the amount of cement in the fresh mixture, 300, 350, and 400 kg/m3. In order to determine the influence of plasticiser on the progress of volume changes, another three concrete mixtures were prepared with plasticiser in the amount of 0.25% by cement mass. Measurements were performed with the goal of observing the influence of cement and plasticiser content on the overall development of volume changes in the concrete. Changes in length and mass losses of the concrete during ageing were measured simultaneously. The continuous measurement of concrete mass losses caused by drying of the specimen’s surface proved useful during the interpretation of results obtained from the concrete shrinkage measurement. During the first 24 hours of ageing, all the concrete mixtures exhibited swelling. Its magnitude and progress were influenced by cement, water, and plasticiser content. However, a loss of mass caused by water evaporation from the surface of the specimens was also recorded in this stage. The measured progress of shrinkage corresponded well to the progress of mass loss.

NEW TECHNOLOGY OF ASH AND SLAG CONCRETES

Directory of Open Access Journals (Sweden)

PAVLENKO T. M.

2017-03-01

Full Text Available Summary. Purpose. Development of scientific-technical bases of manufacture and application of concrete on the basis of ash and slag mixes of thermal power plants. Methods. It is proposed a new technology of preparation of ash and slag concrete mixes. First the ash and slag mix is dispersed through the sieve with meshes 5 mm in a fine-grained fraction and slag. Then, in accordance with the composition of the concrete, obtained fine-grained fraction, slag, cement and tempering water are separately dosed into the mixer. Results. It is proven the high efficiency of the proposed technology of manufacture of ash and slag concretes. It is established that this technological solution allows to increase the strength of concrete by 20...30%, and in the preparation of full-strength concrete to reduce the cement consumption by 15...20%. Scientific novelty. It is developed the new technology of ash and slag mixes application. The concrete mix on the basis of ash and slag mix has an optimal particle size distribution, which ensures the best compaction and, accordingly, the greatest strength of ash and slag concrete with the given cement consumption. Practical significance. The research results promote the mass application of ash and slag mixes of thermal power plants in construction, obtaining of products from the proposed concretes of low cost with high physical-mechanical properties. Conclusion. It is proven the high efficiency of the proposed technology of production of ash and slag concretes. It is established that this technological solution allows increasing concrete strength, and obtaining full-strength concrete to reduce cement consumption. The extensive application of such concrete in construction makes it possible to solve the problem of aggregates for concrete, promotes recycling of TPP waste and consequently the protection of the environment.

Non-autoclaved aerated concrete with mineral additives

Science.gov (United States)

Il'ina, L. V.; Rakov, M. A.

2016-01-01

We investigated the effect of joint grinding of Portland cement clinker, silica and carbonate components and mineral additives to specific surface of 280 - 300 m2/kg on the properties (strength, average density and thermal conductivity) of non-autoclaved aerated concrete, and the porosity of the hardened cement paste produced from Portland cement clinker with mineral additives. The joint grinding of the Portland cement clinker with silica and carbonate components and mineral additives reduces the energy consumption of non-autoclaved aerated concrete production. The efficiency of mineral additives (diopside, wollastonite) is due to the closeness the composition, the type of chemical bonds, physical and chemical characteristics (specific enthalpy of formation, specific entropy) to anhydrous clinker minerals and their hydration products. Considering the influence of these additions on hydration of clinker minerals and formation of hardened cement paste structure, dispersed wollastonite and diopside should be used as mineral additives. The hardness and, consequently, the elastic modulus of diopside are higher than that of hardened cement paste. As a result, there is a redistribution of stresses in the hardened cement paste interporous partitions and hardening, both the partitions and aerated concrete on the whole. The mineral additives introduction allowed to obtain the non-autoclaved aerated concrete with average density 580 kg/m3, compressive strength of 3.3 MPa and thermal conductivity of 0.131 W/(m.°C).