bluuebunny/crossref_metadata_2025_split huggingface dataset:
Practical Considerations Pertaining to the Microscopical Determination of Air Void Characteristics of Hardened Concrete (ASTM C 457 Standard)
Authors: Pleau R , Plante P , Gagné R , Pigeon M 
Published: January 2010

Abstract
Many parameters affecting the quality of the air void characteristics measurement are reviewed and discussed. The difficulties more frequently encountered during the measurement process are described, and some simple rules are proposed in order to increase, as much as possible, the accuracy and reproducibility of the test. The influence of the sampling size is studied, and the variability of air content, specific surface, and spacing factor is estimated from a statistical analysis of about 600 different concrete mixtures. The influence of the operator's subjectivity is also investigated, and the effect produced by large air voids on the computation of the spacing factor is discussed.
Results of an Interlaboratory Concrete Testing Program: Part I
Authors: Gray RJ 
Published: January 2010

Abstract
Measures of the within- and between-laboratory variability associated with the standard test method for determining the compressive strength of cylindrical portland cement concrete specimens have been derived from data obtained in three interlaboratory testing programs operating in western Canada. These data have been analyzed using appropriate ASTM standard practices to provide estimates of repeatability (within-laboratory) and reproducibility (between-laboratory) standard deviation values and corresponding precision indices (difference “two”-standard-deviation limits). Both measures of variability have been found to vary linearly with the compressive strength of the test concrete, and hence the standard deviation and precision values are best expressed as linear functions of this strength. The resulting reproducibility (between-laboratory) precision index values are particularly important in that they provide guidance as to the level of the component of variability to be expected when two or more laboratories are testing the same batch of portland cement concrete for its compressive strength.
Characterization of Ground Granulated Blast-Furnace Slags and Fly Ashes and Their Hydration in Portland Cement Blends
Authors: Douglas E , Elola A , Malhotra VM 
Published: January 2010

Abstract
Chemical analysis, glass content, particle size distribution, heat evolution rate and total heat evolved, scanning electron micrographs and strength development have been studied for three granulated blast furnace slags of different origin and two fly ashes of low and high CaO content.
At all ages heat evolution rates and total heat evolved by the fly ashes are lower than the corresponding values for the granulated blast furnace slags, regardless of their origin.
In the blends studied, high-lime-content fly ash develops higher compressive strengths than low-lime fly ash above the 25% portland cement replacement level.
The results of the study indicate that 50% portland cement replacement by the high-lime-content fly ash used may provide an acceptable compromise to obtain concrete with high compressive strength and low heat of hydration.
A Method for Proportioning High-Strength Concrete Mixtures
Authors: de Larrard F 
Published: January 2010

Abstract
This paper deals with the problem of proportioning high-strength concrete mixtures. An empirical formula is presented that allows the prediction of strength. Also presented is a theoretical model for predicting workability. A practical method is derived to determine the proportion of materials for high-strength concrete mixtures having certain specifications. In this method, it is assumed that the optimal concrete will have a low binder paste and a high admixture content. It is also supposed that the coarse aggregate is stronger than the paste. As most tests are performed on pastes, the number of trial batches and the quantity of materials used during the study are minimal. The concretes obtained by this method exhibit good secondary qualities.
Mechanical Properties and Workability of Superplasticized Concrete
Authors: Jerath S , Yamane LC 
Published: January 2010

Abstract
In the design of concrete structures, the modulus of elasticity, the modulus of rupture, and the split cylinder tensile strength of concrete are predicted from its compressive strength. In this paper, the relationship between compressive strength and other mechanical properties is studied for superplasticized concrete with W-C ratios of 0.28, 0.35, 0.45, and 0.55. Also in this study, the effect of different dosages of a high-molecular-weight sulfonated naphthalene condensate superplasticizer known as Lomar-D on the compressive strength, stress-strain relationship, modulus of elasticity, Poisson's ratio, modulus of rupture, and split cylinder tensile strength of normal, medium, and high-strength concrete mixes is investigated. Overall, 72 cylinders and 36 beams were tested in accordance with ASTM specifications. In addition, the effect of different dosages of the superplasticizer on the workability of different mixes and the slump loss with time was also measured.
Finite-Element Analysis of the Pullout Test Using a Nonlinear Discrete Cracking Approach
Authors: Hellier AK , Sansalone M , Carino NJ , Stone WC , Ingraffea AR 
Published: January 2010

Abstract
An axisymmetric finite-element model, in which fracture was simulated by means of a nonlinear discrete cracking approach, was used to study the pullout test. The pullout test involves measuring the force required to extract a conical frustum of concrete by pulling on an embedded steel disk in opposition to a concentric steel reaction ring at the concrete surface. The precise mechanism of failure and therefore the strength property of concrete, which is actually being measured by the pullout test, has been the subject of several recent studies. The present analysis indicates that failure initiates with the formation of a stable, primary crack system extending from the outer edge of the insert to a point beneath the reaction ring where it is arrested. A stress redistribution resulting from this cracking leads to the development of a secondary crack system which initiates below the concrete surface at the inner edge of the reaction ring and propagates towards the outer edge of the insert. This secondary crack system becomes the eventual failure surface defining the conical frustum. The failure surface appears to be completed by shear fracture of the remaining uncracked ligament. The ultimate load-carrying mechanism is aggregate interlock across the completed failure surface.
Application of the Rapid Chloride Permeability Test to Evaluation of Penetrating Sealers for Concrete
Authors: Whiting D 
Published: January 2010

Abstract
Specimens for rapid and long-term (90-day) chloride permeability measurements were prepared from a conventional concrete mixture. Three penetrating sealers were evaluated, using different methods of specimen conditioning. Results indicate that the rapid chloride permeability test may indicate differences between sealers which are not apparent when subjected to long-term chloride ponding. The method chosen to condition the specimens prior to testing has a significant influence upon the results.
Correlation Between Materials Finer Than No. 200 Sieve and Sand Equivalent Tests for Natural and Crushed Stone Sands
Authors: Alhozaimy AM 
Published: January 2010

Abstract
Fine aggregates used in ready-mixed concrete industry in Riyadh (the capital city of Saudi Arabia) are mainly blended of natural silica sand and manufactured sand obtained from crushed limestone. Fine materials (clay, silt, or dust content) are one of the most important defects of aggregate in Riyadh, particularly in crushed sand. In ready-mixed concrete plants (RMC) and independent laboratories in Riyadh, the practice of determining the amounts of fine materials in fine aggregates is either by ASTM C 117 (materials finer than No. 200 sieve by washing) or ASTM D 2419 (sand equivalent test) and sometimes both.
In this paper, the relationship between the sand equivalent and materials finer than No. 200 sieve tests was investigated. A total of 100 samples of natural silica sand and 100 samples of crushed sand were collected from the stock-piles of different ready mixed-concrete plants in Riyadh. Also, the effects of silica and crushed sands (using different values of sand equivalent and passing No. 200 sieve) on water demands of mortar were investigated.
A strong correlation was found between the sand equivalent and fine materials passing No. 200 for silica sand, whereas there was no correlation for the crushed sand. This indicates that the amount of fine materials in silica sand can be determined by either passing No. 200 sieve or sand equivalent test. However, the sand equivalent test can be misleading in crushed sand. For the same workability, the results indicated that there was a direct relation between water demand and the amount of materials passing No. 200 sieve for both silica and crushed sands. However, there was a good correlation between water demand and sand equivalent for only silica sand.
Effect of Elastic Modulus of Capping Material on Measured Strength of High-Strength Concrete Cylinders
Authors: Vichit-Vadakan W , Carino NJ , Mullings GM 
Published: January 2010

Abstract
Studies have shown that end conditions of concrete cylinders tested in compression can have a significant effect on the measured strength of the cylinders, especially when high-strength concrete is used. The ASTM standard for bonded caps has requirements for minimum cube strength of the capping material and maximum cap thickness. However, a study by researchers at the National Ready Mixed Concrete Association (NRMCA) showed that the 50 mm cube strength may not be very useful in determining whether the capping material will perform adequately when testing high-strength concrete. In the study reported in this paper, the dynamic modulus of elasticity and modified cube strength (ASTM C 116) of various capping materials were evaluated as a function of age. The results showed that each capping material has a unique relationship between dynamic elastic modulus and cube strength. The elastic modulus of different capping materials can vary greatly at a given cube strength. For example, at a modified cube strength of 80 MPa, the elastic modulus of neat cement paste, at 30 GPa, was twice the elastic modulus of one sulfur mortar, at only 15 GPa. The elastic modulus of the capping materials was correlated with previously reported cylinder strengths. In cases where the cylinder strength was affected by the capping material, there is evidence that the cylinder strength was related to the modulus of elasticity and not to the cube strength of the capping material.
Two-Hour Zero Slump Loss, High-Strength Pumpable Concrete—An Application Case in Dam Structure
Authors: Feng N , Zhuang Q 
Published: January 2010

Abstract
About 700 000 m3 of pumpable concrete, which was produced by a high-range water-reducing admixture (HRWRA) and relatively low-strength cement, was used in the Xiao Lang Di water conservancy project. The concrete achieved a 28-day compressive strength as high as 90 MPa, a slump of 20 cm, and almost no slump loss in 2.5 h after mixing, as well as good freeze-thaw durability. The paper describes in detail the mix proportions, the method to control slump loss, and the related mechanical properties.
Modified Slump Test to Measure Rheological Parameters of Fresh Concrete
Authors: Ferraris CF , de Larrard F 
Published: January 2010

Abstract
The ease of placement of concrete depends upon at least two physical properties, the yield stress and plastic viscosity. Currently the most common field test is the slump test, and it is related only to the yield stress. Therefore, a simple field test method intended to provide an evaluation of the two Bingham rheological parameters, yield stress and plastic viscosity, was developed. To determine the plastic viscosity the time necessary for the upper surface of the concrete in the standard slump cone to slump 100 mm was measured. The apparatus and test procedure are described. Semi-empirical models are proposed for the yield stress and for the plastic viscosity as function of the final slump and slumping time. The application of the modified slump test for the evaluation of the viscosity is limited to concretes with a slump of 120 to 260 mm. If the validity of this test is confirmed in the future, it could be used as a field quality control test.
Effects of Superplasticizer, Retarding Agent, and Silica Fume on the Air Permeability of High-Performance Concrete
Authors: Gagné R , Ollivier J-P , Latreille Y 
Published: January 2010

Abstract
The aim of this research is to evaluate how transport properties at the surface and in the core of high-performance concrete (HPC) slabs are affected by silica fume and by superplasticizer and retarding agent dosages. The transport properties were evaluated by measuring the air permeability at two depths under the surface finished with a wooden trowel. The experimental program is based on eight different high-performance concrete mixtures (77 to 93 MPa) made with a water-to-binder ratio of 0.30. An ordinary portland cement (OPC) and a blended silica-fume cement (SF) were used to compare the effect of silica fume on the air permeability of surface and core concrete. Four mixtures were produced with a retarding agent to assess the effect of set retardation on the surface properties of high-performance concrete. For each combination of cement type and retarding agent dosages, the superplasticizer dosage was selected to produce two slump levels of 100 ± 10 mm and 200 ± 20 mm.
It was found that the air permeability of the concrete located just beneath the surface of HPC slabs can be 2 to 20 times higher than the core permeability. The ratio between the surface and core permeabilities depends on mix-design parameters such as silica fume, superplasticizer (slump), and retarding agent dosages. Increasing the slump of HPC (from 100 to 200 mm) systematically increased the surface permeability. The effect of slump (or superplasticizer dosage) on the surface permeability of the HPC decreased as compressive strength increased. The use of a retarding agent in HPC without silica fume increased the air permeability of the surface concrete. This effect is particularly important for the concrete containing a high dosage of superplasticizer. Silica fume proved very effective in inhibiting increased surface permeability due to the dosages of superplasticizers and retarding agents.
A Statistical Analysis of Hot and Warm Accelerated Concrete Curing Methods
Authors: Meyer D 
Published: January 2010

Abstract
Strength test results for accelerated-cured specimens, obtained after only 24 h, are used to predict the 28 day strength of concrete. Various accelerated curing methods are available. Two of these methods are compared in relation to the uncertainty of their predictions and the stability of the relationship between their 24 h and 28 day concrete strength. The results suggest that warm water accelerated curing is preferable to hot water accelerated curing of concrete. Various methods for reducing the uncertainty associated with the estimates of 28 day strengths are suggested. In particular it is suggested that the effect of variations in cement chemistry over time be addressed by using dynamic linear models with coefficients that vary over time.
Ultrasonic Testing to Determine Water-Cement Ratio for Freshly Mixed Concrete
Authors: Popovics S , Popovics JS 
Published: January 2010

Abstract
The objective of the research presented here was to find promising directions for the development of ultrasonic test method(s) for the direct, instantaneous determination of the water-cement ratio (W/C) in fresh mortar or concrete. The importance of W/C is related to potential strength development and, to a certain extent, the durability potential of the hardened concrete. Since previous efforts during the past 50 years have been unsuccessful in testing fresh concrete due to the complexity of the problem, innovative, high-risk/high-gain methods were selected in the present work. The methods are considered innovative since a literature search detected no sign that they have been used for testing fresh concrete before.
The following test methods were tried out for testing fresh concrete: • ultrasonic methods used regularly for testing hardened concrete; • solidification of the fresh mixtures by freezing or heat treatment or accelerating admixture + heat treatment before testing; • use of high-intensity stress waves by lithotripter; • the direct contact method.
None of these methods produced a satisfactory solution for the instantaneous determination of the water-cement ratio, although interesting side results were obtained. It is hoped that both the positive and negative results presented will help researchers in their work on ultrasonic testing of concrete.
Rheology of Cement Paste and Concrete
Authors: Struble L , Szecsy R , Lei W-G , Sun G-K 
Published: January 2010

Abstract
Much has been learned in recent years about the rheology of cement paste and how it relates to microstructure. Such progress has been made possible in part by the use of specialized instruments for measuring dynamic rheological properties, developed to characterize viscoelastic materials. This paper reviews recent studies of cement paste in our laboratory in which dynamic rheological properties are used to follow the effects of cement hydration. Not as much has been learned about the rheology of concrete. Measuring flow behavior of concrete presents interesting challenges; concrete rheometers have been developed, but they are not widely used. It appears likely that concrete rheology is controlled by rheology of its paste, although such links have not yet been directly established. This paper also presents preliminary results from our laboratory on concrete flow behavior. Concrete rheology provides important information about its workability, and rheological parameters have important advantages over slump when characterizing workability.
A New Test Method for Fiber-Reinforced Concrete
Authors: Zollo RF , Hays CD , Zellers R 
Published: January 2010

Abstract
It has long been recognized that the principal benefit gained by using fiber reinforcement in portland cement concrete is a conversion of the material from brittle to relatively ductile behavior. The apparent ductility, or toughness, is primarily related to the improved tensile strength of fiber-reinforced concrete (FRC) especially and even after significant matrix cracking has occurred. However, the methods used to measure tensile strength and toughness of FRC have been, at best, elaborate and controversial.
A practical and much needed testing methodology for fiber-reinforced concrete has been developed and adopted as an ASTM standard. It was conceived from the need to have a test that is relatively simple and inexpensive to conduct and is yet capable of assessing the tensile strength of cracked FRC. The test method, ASTM C 1399, and an interlaboratory testing program conducted to help formulate a precision statement for the new methodology is discussed.
Mechanical Properties and Freezing and Thawing Durability of Polypropylene Fiber-Reinforced Shotcrete Incorporating Silica Fume and High Volumes of Fly Ash
Authors: Zhang MH , Mirza J , Malhotra VM 
Published: January 2010

Abstract
This paper describes the materials used, mixture proportions, mixing and shotcreting operation, and properties of the fresh and hardened polypropylene fiber-reinforced shotcrete incorporating silica fume and high volumes of fly ash. The polypropylene fiber-reinforced high-volume fly ash shotcrete produced had satisfactory workability, mechanical properties, and resistance to freezing and thawing cycling. The shotcrete containing silica fume had negligible rebound compared with that without silica fume. The incorporation of fly ash and silica fume improved the workability of the fresh shotcrete, and this resulted in lower operating pressure for the shotcreting. The use of polypropylene fibers up to 0.5% by the volume of the shotcrete did not affect significantly the compressive strength, and the shotcrete incorporating both fly ash and silica fume bonded well to the base concrete. The fiber-reinforced shotcrete showed satisfactory performance after 300 cycles of freezing and thawing with a durability factor &gt;80 even though the air contents were relatively low, and the spacing factor L¯ was relatively high.
Evaluation of the Effect of Portland Cement Alkali Content, Fly Ash, Ground Slag, and Silica Fume on Alkali-Silica Reactivity
Authors: Lane DS , Ozyildirum HC 
Published: January 2010

Abstract
The effects of portland cement alkali content, and replacement of portland cement with Class F fly ash, slag, or silica fume on alkali-silica reactivity (ASR) were studied by measuring the expansion of mortar bars made with Pyrex glass and stored over water at 38°C. Expansions were negligible with portland cements having alkali contents of 0.40% Na2O equivalent or less. Above 0.40%, expansions of bars made with cement only expanded linearly with cement alkali content after 56 days in storage through 336 days. Regression analysis yielded correlation coefficients of 0.91 for the 56 and 336 day expansions. An expansion of 0.10% was established as the maximum expansion indicative of a mixture providing acceptable mitigation of ASR.
The replacement of cement having alkali content of 0.50% and above with pozzolan or slag was found to reduce expansion. A procedure for normalizing the expansions of pozzolan and slag batches to the regression of cement control batch expansions is presented that allows comparison between batches on an equivalent basis by factoring out inherent testing variability. The level of expansion achieved was related to the alkali content of the cement and the type and amount of mineral admixture or slag used. The materials tested, several Class F fly ashes, a slag, and a silica fume were effective in preventing expansions when used in appropriate amounts with respect to the alkali content of the cement used. The mitigation provided by the materials tested was greater than would have been achieved through simple alkali dilution. Preventive methods based on total cementitious alkali content discount the effectiveness of Class F fly ash, slag, and silica fume in mitigating ASR.
Comparison of Field Observations with Laboratory Test Results on Concretes Undergoing Alkali-Silica Reaction
Authors: Whiting NM 
Published: January 2010

Abstract
Alkali-silica reactivity (ASR) was identified as contributing to premature failure of 12 concrete pavements in Minnesota. The available aggregate sources used in these distressed pavements were tested for potential ASR. Standardized tests result in conflicting information. The sands tested as potentially deleteriously expansive in the ASTM C 1260 Mortar Bar Test (expansion &gt;0.2%), but tested as not deleteriously reactive in the ASTM C 1293 Concrete Prism Test (0.0295 to 0.042% expansions). Although expansions of these C 1293 prisms remained low, sand-sized opaline shales reacted to form gel, spalls, and cracks. Similar cracking and gel deposits are associated with these shales in field samples. The C 1260 mortar bars made with crushed quartzite aggregates exhibited moderate expansion values (average expansions ranging from 0.135 to 0.188%), but the C 1293 prisms made with quartzite coarse aggregates exceeded the 0.04% expansion limit (0.082 to 0.1137% expansion). Quartzite is reacting in several pavements but not as extensively as the high C 1293 test results imply. The sands are reacting in pavements and in test samples, but this reaction is not manifested as expansion in the C 1293 prisms.