bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Capping Materials and Procedures on the Measured Compressive Strength of High-Strength Concrete
Authors: Lobo CL , Mullings GM , Gaynor RD 
Published: January 2010

Abstract
The effect of end conditions and testing procedures on the measured strength of 100- by 200-mm (4- by 8-in.) concrete cylinders were evaluated. Concretes representing three strength levels: 50, 75, and 120 MPa (7000, 11 000, and 17 000 psi) were prepared. Cylinder end conditions included grinding and capping with two types of sulfur mortar and cement paste. Effect of thickness of capping material was also evaluated.
Cement paste caps produced, on average, 1% higher strengths than ground ends, regardless of concrete strength level and cap thickness. Cylinders capped with sulfur mortar 2 h prior to testing produced 2 to 7% lower strengths than the ground condition. Capping cylinders with sulfur mortar seven days prior to testing produced strengths equivalent to the ground condition, except with thick caps of sulfur mortar on the 120 MPa (17 000 psi) concrete, in which case lower strengths were observed. No significant difference between sulfur mortars was evident, even though one was advertised for use with high-strength concrete.
Strength Evaluation of In-Situ Concrete by Rebound Hammer and Core Testing
Authors: Ward MA , Langan BW 
Published: January 2010

Abstract
This paper describes the results of an extensive field investigation where the quality of in-place concrete flatwork was evaluated. Nondestructive testing (NDT) was carried out using ultrasonic pulse velocity and rebound hammer techniques to establish a correlation with compressive strengths of core tests. The rebound hammer/core correlation formed the basis of a recommendation on the acceptance or rejection of the in-situ concrete. The ultrasonic pulse velocity UPV testing was primarily used to establish concrete uniformity. Limited freeze-thaw testing was carried out to determine the potential long-term durability performance. In order to minimize the effects of surface preparation on the test results, considerable time was spent to determine the optimum grinding procedure.
Break-Off Test for High-Strength Concrete
Authors: Di Maio A , Giaccio G , Zerbino R 
Published: January 2010

Abstract
High-strength concrete is one of the new developments in concrete technology. In addition to compressive strength levels above 60 MPa, high workability, improvements in early age performance and durability appear to be its main advantages. This paper studies the suitability of the break-off test to evaluate strength development of high-strength concrete. Regression equations between break-off pressure and compressive strength were calculated. The effects of different variables such as age, type of coarse aggregate, and strength level are discussed. The obtained results indicate that the break-off test can be used satisfactorily to evaluate the quality of concretes with compressive strength levels up to 100 MPa.
Comparison of Five Standards on Ultrasonic Pulse Velocity Testing of Concrete
Authors: Komlos K , Popovics S , Nurnbergerova T , Babal B , Popovics JS 
Published: January 2010

Abstract
The essence of the pulse velocity method is that the transition time of an ultrasonic longitudinal pulse (wave) is measured in concrete. From this, the pulse velocity can be calculated, and inferences are drawn concerning the strength or overall quality, or both, of the concrete. Many countries have standardized this procedure, five of which are compared in this paper. These are American (ASTM), British (BS), German (DIN), Russian (GOST), and Slovak (STN) standards.
The best, and perhaps the only reliable applications of the ultrasonic pulse velocity are for checking the uniformity of concrete and monitoring the changes in a concrete with time. Strength estimation is possible with only ±20% accuracy and even this can be achieved only under strict laboratory conditions. The other applications (defect detection, crack depth measurements, and so forth) are even less reliable. Thus, they are inadequate for practical purposes, especially under field conditions. No warning is given in any of the examined standards about the unreliability of most of these applications.
It is hoped that an evaluation of these standards will help in the better use of the ultrasonic pulse velocity method and contribute to the improvement of future standards.
Improving Initial Strength of a Concrete made with Type 20M Cement
Authors: Kessal M , Nkinamubanzi P-C , Tagnit-Hamou A , Aïtcin P-C 
Published: January 2010

Abstract
The improvement of initial strength of concrete constitutes a special interest for contractors that often seek to enhance their productivity by reducing the delay before deforming. The study presented in this paper shows that it is possible to use a low heat of hydration Type 20M cement that is typically employed in Quebec in mass concrete construction to develop high initial strength that can be of special interest in enhancing the production of massive structural elements. Type 20M cement is similar to Type II ASTM cement but has a slightly lower heat of hydration.
The improvement of initial strength of concrete made with Type 20M cement was made possible by reducing the W-C ratio by using a melamine-based superplasticizer that has less influence on retarding the setting time than that of a naphthalene-based superplasticizer and by substituting part of the cement by an adequate amount of silica fume and limestone filler.
Evaluation of Laboratory Drying Procedures Relevant to Field Conditions for Concrete Sorptivity Measurements
Authors: DeSouza SJ , Hooton RD , Bickley JA 
Published: January 2010

Abstract
The surface humidities of a limited set of field concretes during summer conditions in Ontario were measured prior to water absorption (sorptivity) testing. A series of alternative laboratory curing conditions was carried out on cores prior to laboratory sorptivity tests, to determine which would best mimic average field conditions (surface humidities greater than 40% and moisture contents greater than 1%). It was found that three days' oven drying at 50°C followed by sealed drying for four days at 50°C as suggested by Parrott worked well. In addition, the moisture content at test was calibrated to measured sorptivity results.
Hydrogen Evolution in Concrete Due to Free Silicon Metal in Microsilica
Authors: Fidjestøl P , Jørgensen O 
Published: January 2010

Abstract
Many millions of cubic meters of microsilica concrete have been placed over the years. Still, concern has been raised over possible risks related to the formation of hydrogen due to free silicon metal (silicon) contained in microsilica (silica fume, condensed silica fume).
The paper addresses this question from four different viewpoints: • Chemical reaction mechanism and theoretical amounts of hydrogen that can be generated. • Definition of explosion limits on hydrogen content in the air. • Test method for silicon-metal content in microsilica in one laboratory and comparison between laboratories. • Hydrogen development in practical situations, that is, in tests with mortar in an isolated chamber and in simulation tests of hollow-core elements.
From the present study it is concluded that only in extreme cases, with very high silicon-metal contents and with heat curing, can sufficient hydrogen be developed to cause an explosive mixture of gases. Further, the limit of 0.4% metallic silicon, as determined by the recommended method, will remove even these concerns.
An Overview of the Fracture Mechanics of Concrete
Authors: Shah SP 
Published: January 2010

Abstract
For the design of concrete structures where adequate ductility is a concern, it is becoming increasingly necessary to use concepts based on crack growth and propagation to account for ductility and avoid catastrophic failure. While fracture based methods exist for steel design, no standard method currently exists to quantify the fracture properties of concrete. In light of a multitude of recent investigations to describe the complex nature of concrete fracture, it is currently accepted that two parameters are required to characterize crack propagation in concrete. This paper provides a brief background for the use of fracture mechanics in concrete and appeals for the establishment of standardized testing procedures for use in concrete. If appropriately determined, fracture parameters can provide a valuable tool for the design of new higher performance concretes and concrete structures.
Fracture Mechanics Testing for Structural Steels
Authors: Rolfe S 
Published: January 2010

Abstract
Fracture mechanics is widely used to evaluate the fracture behavior of structural steels. However, the fracture toughness of structural steels is affected significantly by temperature, loading rate, and constraint. Because of the effect of these factors, the fracture behavior of structural steels varies considerably from linear elastic to general yielding. Accordingly, there are numerous fracture mechanics tests of structural steels—each of which is applicable to the general regime of linear-elastic, elastic-plastic, or general yielding behavior.
This paper describes the fracture testing and behavior of structural steels in each of these three general domains and briefly describes the ASTM test methods used in each domain.
Standards for Fracture Toughness Testing of Rock and Manufactured Ceramics: What Can We Learn for Concrete?
Authors: Hanson JH , Ingraffea AR 
Published: January 2010

AbstractThis paper presents a review of the American Society for Testing and Materials (ASTM) and the International Society for Rock Mechanics (ISRM) standards for determining the plane-strain fracture toughness of cemented carbides and rocks, respectively, with an eye toward applicability to concrete. The evolution of the chevron-notched test specimen used in these standards is briefly reviewed. A discussion of a particular chevron-notched configuration, the short rod test specimen, and associated test methods follows. The ASTM and ISRM standards are then described. The paper evaluates the potential for learning from, modifying, or adapting these standards for use on a standard fracture toughness test for concrete. The potential advantages and disadvantages of using the short rod geometry and testing methods on concrete are discussed, taking into account fracture response, shape, volume, preparation, precracking, symmetry, and subsize specimen effects. Preliminary research into the applicability of the short rod geometry and testing procedures on concrete is discussed.
Determination of Slag and Fly Ash Content in Hardened Concrete
Authors: Hooton RD , Rogers CA 
Published: January 2010

Abstract
Some agencies limit the slag (ground-granulated blast-furnace slag) replacement of portland cement in some instances. In other cases, minimum slag replacements are specified. Therefore, there is a need to be able to quantify the slag content to show conformance with specifications. The two methods proposed here are (1) X-ray diffraction (XRD) of ignited mixtures and (2) optical microscopy on thin sections. The XRD method involves ignition of the mortar fraction of concrete at 950 to 1050°C to devitrify the unreacted slag. The resulting crystalline melilite component is then compared to that in an ignited sample of slag from the same source.
The optical method involves preparation of thin sections of the concrete and point counting to obtain the number of unhydrated slag grains. These are compared to a set of calibration standard sections. The optical technique can also be used for estimating fly ash content and similarly, grain mounts have been used to detect the presence of both fly ash and slag substitution in portland cements.
The paper describes both these techniques in detail and discusses limitations. When properly calibrated, either technique can be used to estimate the slag replacement level to approximately ±10%. As well, several case histories are described where these procedures have proved to be extremely useful.
Determination of Slag and Pulverized Fuel Ash in Hardened Concrete—The Method of Last Resort Revisited
Authors: Grantham MG 
Published: January 2010

Abstract
The paper briefly reviews the standard United Kingdom (UK) procedure for the determination of cement content of hardened concrete. It then points out the special problems that occur when attempting to determine the cement content and the amount of mineral admixture in concrete. The method described in this paper, originally devised by the Building Research Establishment, employs a total analysis of the concrete and control samples of the cement, aggregates, and mineral admixture. The method usually used is quantitative X-ray fluorescence (XRF) analysis. The analytical results are examined by the application of a simultaneous equation mathematical approach to resolve the content of the individual components. Application of the method in a case history is used for illustration.
Chloride Permeability Versus Air Content of Latex Modified Concrete
Authors: Kuhlmann LA , Foor NC 
Published: January 2010

Abstract
Results of chloride permeability tests on latex modified concrete (LMC) with a wide range of air contents are presented. Air void data from these experiments are compared to air void results from other sources. Conclusions regarding chloride permeability and the air void system of LMC are given. The 6-h permeability test is described; comments are made regarding an additional measurement to be considered for inclusion in the method. Recommendations are given for future study of the chloride permeability of LMC.
Recycled Concrete—A Source for New Aggregate
Authors: Rasheeduzzafar  , Khan A 
Published: January 2010

Abstract
Recycling concrete rubble as aggregate material for the construction programs in the Middle East, where high-quality mineral aggregate is scarce, offers an excellent ecological and economic opportunity. Based on tests carried out on 21 mixes, this investigation attempts to develop data especially on the strength, failure mechanism, and durability characteristics of the recycled aggregate in comparison with the conventional concrete. Results show that for a W/C ratio of 0.35 the recycled aggregate concrete has 30% lower strength than conventional concrete. The strength differential narrowed for increasing values of W/C ratio until the strengths were about equal for a W/C ratio of 0.55. No significant increase in the strength of recycled aggregate concrete was obtained by reducing the W/C ratio below 0.40. It is indicated that the quality of recycled aggregate concrete will improve with the quality of recycled mortar or if the recycled material has a high aggregate-cement ratio. The recycled aggregate concrete showed somewhat better workability characteristics than conventional mixes although its modulus of elasticity and durability characteristics were lower. It is proposed that satisfactory concrete can be made by recycling concrete as aggregate where disposal problems exist or where natural aggregate is either inaccessible or of inferior quality.
The Variability of Condensed Silica Fume from a Canadian Source and Its Influence on the Properties of Portland Cement Concrete
Authors: Pistilli MF , Rau G , Cechner R 
Published: January 2010

Abstract
Condensed silica fume is formed during the manufacture of ferrosilicon in electric submerged-arc furnaces. The use of condensed silica fume has been evaluated in portland cement concrete. Thirty-two samples of condensed silica fume, each collected on consecutive days, were analyzed for chemical and physical routine quality control tests of pozzolan. Eight of these samples, representing the variations of the routine tests, were tested for complete ASTM Specification for Fly Ash and Raw or Calcined Natural Pozzolan for Use as a Mineral Admixture in Portland Cement Concrete (C 618) conformance. All of the samples tested were found to conform to ASTM C 618 with the exception that the water requirement was excessive.
Concrete mixtures were evaluated with a fixed quantity of 24 kg/m3 (40 lb/yd3) of condensed silica fume. The low portland cement content mixtures show slightly higher shrinkage after 64 weeks of drying; the rich mixtures have the same shrinkage. Compressive strengths were more than 30% higher than control mixtures having low cement contents and were more than 10% higher than control mixtures having higher cement contents. This amount of condensed silica fume was found to have no effect on the time of set relative to control mixtures containing the same portland cement content.
On In-Place Strength of Concrete and Pullout Tests
Authors: Yener M , Chen W-F 
Published: January 2010

Abstract
The current status of in-place strength evaluation of concrete is discussed. A literature survey regarding the controversy surrounding the assessment of concrete strength through field-cast laboratory-cured cylinder tests is presented. Inconsistencies associated with the drilling and testing of cores for determining in-place concrete strength are pointed out. On the basis of these arguments, the necessity of developing alternative nondestructive test procedures is emphasized. This is followed by a detailed discussion on the status of the pullout test method as a measure of compressive strength of in-place concrete, which appears to be a potentially feasible nondestructive test procedure. The present paper constitutes a state of the art report on the aforementioned topics and contains appropriate recommendations from the authors.
The Uniformity and Influence of Silica Fume from a U.S. Source on the Properties of Portland Cement Concrete
Authors: Pistilli MF , Wintersteen R , Cechner R 
Published: January 2010

Abstract
Silica fume is formed during the manufacture of ferrosilicon in electric submerged-arc furnaces. The use of silica fume has been evaluated in portland cement concrete. Thirty samples of silica fume, each collected on consecutive days from SKW Alloys, Inc. in Calvert City, KY, were analyzed for routine quality control tests of a pozzolan. Six of these samples, representing the variations of the routine tests, were tested for complete ASTM Specification for Fly Ash and Raw or Calcined Natural Pozzolan for Use as a Mineral Admixture in Portland Cement Concrete (C 618) conformance. Laboratory mixtures of air-entrained and nonair-entrained concrete, containing a representative sample of silica fume, were cast for compressive strength (1 to 120 days), drying shrinkage, and time of set. Although a classification for silica fume is not currently contained in ASTM C 618, all of the samples tested were found to conform when compared to the requirements of this standard, with the exception that the water requirement was excessive.
Concrete mixtures containing only 24 kg/m3 (40 lb/yd3) of silica fume showed slightly high shrinkage at 64 weeks of drying with the lower cement content mixtures relative to control mixtures. The silica fume mixtures showed 120 to 180% higher compressive strength at 120 days in lean mixtures, 110 to 120% higher compressive strength in richer mixtures. This amount of silica fume was found to have no effect on initial set of concrete and had only a slightly longer final set.
A Rockwell Hardness Test for Concrete
Authors: Winslow DN 
Published: January 2010

Abstract
The standard superficial Rockwell 15Y hardness test has been adapted for use on concrete. Hardness measurements were made on the mortar regions between the coarse aggregate pieces. A correlation between this hardness and the concrete's compressive strength was developed. For 7.5- by 15-cm (3- by 6-in.) cylinders, it is Rockwell 15Y hardness = 73.5 (log compressive strength in psi) — 187 or 73.5 (log compressive strength in MPa) — 28.0. Various effects of specimen preparation and size are discussed, as are the statistics of the test.
Mechanism of Pozzolanic Reactions and Control of Alkali-Aggregate Expansion
Authors: Bhatty MSY 
Published: January 2010

Abstract
The mechanism of pozzolanic reactions and their control of expansion caused by alkali-aggregate reaction was investigated. Mixtures of tricalcium silicate, opal, sodium hydroxide, and water having calcium oxide to silica mole ratios from 1.07 to 3.0 were prepared and reacted from seven days to four years before filtering. The solids (precipitates) were studied by X-ray diffraction to determine the phases present, and the alkali content of filtrates was obtained by chemical analysis.
Results suggest that pozzolans reduce or eliminate alkali-aggregate expansion by producing additional calcium silicate hydrate and low lime calcium silicate hydrate. These hydrates can retain additional alkali, thus reducing the amount of alkali available for reaction with reactive aggregate. In order to control alkali-aggregate expansion by the addition of pozzolan, such as fly ash, results indicate that about 30% low lime fly ash is required. However, this amount could be reduced considerably, to a level as low as 20% (cement basis), if the concrete contains reactive siliceous aggregate.
Nondestructive Combined Methods Applied to Structural Concrete Members
Authors: Di Maio AA , Traversa LP , Giovambattista A 
Published: January 2010

Abstract
Strength evaluation of structural elements has been done by nondestructive methods, using ultrasonic pulse velocity, hammer rebound, and localized pressure, either individually or in a combined way. The effects of the mineralogical composition of the coarse aggregate, moisture content, and age of concrete on pulse velocity and rebound number is reported. Standard cylindrical specimens cured at 100% relative humidity were tested for compressive strength. Regression equations thus obtained were used to estimate the in-situ compressive strength of reinforced prisms (0.15 by 0.15 by 1.00 m). The prediction error is calculated from the comparison of the estimated strength and the strength determined on drilled cores.
The Effect of Blast Furnace Slag Cement on Alkali Aggregate Reactivity: A Literature Review
Authors: Hogan FJ 
Published: January 2010

Abstract
The growing shortage of quality aggregates and the trend toward higher alkali levels in portland cement has increased the risk of problems associated with alkali-aggregate reactivity (AAR). The use of ground granulated blast furnace slag as a partial replacement for portland cement is a recognized remedial alternative in cases where a potential for AAR exists.
This report reviews available literature dealing with the influence of ground granulated blast furnace slag on AAR. In general, it was concluded that when the binder consists of 50% or more of ground vitreous slag, an alkali content of up to 1.00% as sodium oxide (Na2O) equivalents can be tolerated without a risk of problems. Improved resistance to AAR was provided from slags ground to higher fineness.
Several theories, promulgated to explain the mechanism for enhanced resistance to alkali reaction, are also reviewed.
Laboratory Examination of a High-Alumina Cement Concrete Column After 46-Years Exposure at Treat Island, Maine
Authors: Buck AD , Burkes JP 
Published: January 2010

Abstract
Examination of a high-alumina cement (HAC) concrete specimen made in the laboratory and exposed to several hundred cycles of freezing and thawing at Treat Island, ME, showed that its excellent durability was due to the fact that it was in fact air entrained. This was a surprise since it was supposed to be nonair-entrained concrete. The reason for this discrepancy is not known. In addition, X-ray diffraction examination showed that the phase conversion often associated with HAC had not occurred.