bluuebunny/crossref_metadata_2025_split huggingface dataset:
Test Method for the Potential Release of Hydrogen Gas from Silica Fume
Authors: Edwards-Lajnef M , Aïtcin P-C , Wenger F , Viers P , Galland J 
Published: January 2010

Abstract
Most silica fumes contain a small amount of silicon metal. Silicon reacts with alkali or alkaline-earth hydroxides when water is present to yield hydrogen. The reaction mechanism is similar to the one used to produce cellular concrete or expanding grout with aluminum powder.
There is concern that hydrogen release can cause problems when silica fume is used in grouting prestressing tendons because atomic hydrogen embrittles steel, thereby shortening the life of the prestressed concrete structure.
Moreover, if the partial pressure of hydrogen in air attains a certain level, there is a risk of explosion in the presence of a source of heat or spark. Portland cement-based materials with silica fume that contains some silicon do not present an induction period that could delay hydrogen release. Therefore, users of silica fume should be aware of this potential danger.
Because most users of portland cement are unfamiliar with techniques for measuring the silicon content of silica fume, a simple and rapid measurement method is shown here to evaluate the amount of hydrogen that can be released from a given silica fume. This value can be used to calculate the amount of silicon contained in the silica fume.
The Role for Fracture Mechanics in Reinforced Concrete Design
Authors: Hawkins NM 
Published: January 2010

Abstract
The performance under applied and environmental loads and the proportions selected for reinforced concrete members are determined primarily by two factors: the properties of the concrete used in those members and the mathematical models used to design those members. Standard tests such as cylinder compression, modulus of rupture, and splitting tension are now used to characterize the properties of the concrete for design and for quality control purposes. Yet those tests do not provide the information necessary to distinguish between the likely characteristics in practice of different high-performance concretes. Post-cracking behavior, which controls stiffness and durability at service loads especially for unidirectionally and lightly reinforced members, is closely tied to concrete properties (fracture softening) best established through displacement controlled fracture type tests.
Fracture mechanics concepts will not influence building code provisions for reinforced concrete until practitioners start using those concepts to improve their designs. To facilitate that action, efforts need to be concentrated on developing data that correlate the relative contributions of the fracture softening properties of different concretes to building code provisions that control designs in which only unidirectional reinforcement is desired. When that correlation has been established, and when appropriate fracture softening characteristics of different typical concretes have been determined through a comprehensive test program, then designers will need an ASTM Standard that they can use to check that, for the actual concrete placed in their structure, the fracture softening characteristics used in their design are being achieved.
Results of an Interlaboratory Test Program: Compressive Strength of Concrete
Authors: Kennedy S , Detwiler R , Bickley J , Thomas M 
Published: January 2010

Abstract
Although both ASTM and CSA have had standards for testing the compressive strength of concrete cylinders since the 1920s, neither standard contains a statement of the within- and between-laboratory precision of its test method as prescribed by Practice for use of the Terms Precision and Bias in ASTM Test Methods (ASTM E 177). This paper describes an interlaboratory study performed by 16 CSA-certified Ontario testing laboratories in accordance with Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method (ASTM E 691). The analysis shows that the variability of the test results increases with the mean strength of the concrete. A precision statement based on the results reported here is recommended for inclusion in Test Method for Compressive Strength of Cylindrical Concrete Specimens (ASTM C 39) and CSA A23.2-9C (Compressive Strength of Cylindrical Concrete Specimens).
Limitations of the Carbonate Extraction/UV Spectrophotometric Method for Determining Lignosulfonate-Based Admixtures in Hardened Concrete
Authors: Sanders CI , Sadeghi SS , Nelson NL 
Published: January 2010

AbstractIn 1963, a method for determining lignosulfonate addition rates in portland cements was reported (Wexler and Brako 1963). Over the years, this procedure has been adopted as the most common method for determining lignosulfonate-based admixtures in hardened concrete. The procedure involves extraction of lignosulfonate derivatives from pulverized concrete with an alkali-carbonate solution. The concentration of the extracted derivatives is then measured by comparing their ultraviolet (UV) spectra with those obtained from appropriate concrete standards.While widely applicable, we have encountered numerous limitations when using this method to investigate concrete performance problems. Among the factors that may affect the results of the carbonate extraction/UV spectrophotometric procedure are the source of lignosulfonate in the admixture, cement content, concrete maturity, and certain extractable constituents such as other admixtures, cement additives, organics from fly ash, and unknown constituents. In this paper, we will discuss the results of systematic studies that have been performed to determine how each of these variables can influence the accuracy of results obtained.
Determination of a Nitrite-Based Corrosion Inhibitor in Plastic and Hardened Concrete
Authors: Jeknavorian AA , Chin D , Saidha L 
Published: January 2010

Abstract
The use of DCI® (W. R. Grace and Company, Cambridge, MA) corrosion inhibitor, a 30% solution of calcium nitrite, has become an established method for reducing the corrosive action of chloride on reinforcing steel in concrete. Certain regulatory agencies require monitoring the admixed concrete to verify that the specified amount of corrosion inhibitor has been added. This paper discusses a field test for confirming the presence of nitrite in plastic concrete and a laboratory method for measuring the addition rate of a nitrite-based corrosion inhibitor for hardened concrete. Our experience with these methods indicates that the concrete mix design does not generally affect the extraction of the nitrite from the concrete. However, to assure an accurate estimation of the admixed nitrite, where less than 85% recovery is achieved, the amount of nitrite extracted from the test sample should be compared to that of a reference concrete having the same mix design.
Determination of Blast-Furnace Slag Content in Hardened Concrete by Electrical Conductivity Methods
Authors: Xie P , Gu P , Fu Y , Beaudoin JJ 
Published: January 2010

Abstract
Electrical conductivity measurements were made on concrete systems containing blast-furnace slag. It was found that the slag content significantly influenced the concrete conductivity. A linear relationship between the concrete conductivity and the slag content and the volume fraction of aggregate was established by experiment. The relationship can be expressed as follows σc=ka·ϕa+ks·(slgc)+ko where σc is the concrete conductivity; φa is the volumetric fraction of aggregate; (slg/c) is the relative content of slag by weight of cementitious materials; and ka, ks, and ka are empirical coefficients. This relationship provides a basis for the determination of slag content in hardened concrete by electrical conductivity methods.
Factors Affecting the Durability of Concrete and the Benefits of Using Blast-Furnace Slag Cement
Authors: Idorn GM , Roy DM 
Published: January 2010

AbstractClassical experience and research in the United States and Europe on the durability of concrete in marine environments are reviewed. Special precautions were recognized early as necessary for resisting the combined physicochemical effects of exposure to seawater. In the United States, quality work resulting in dense impervious concrete was an appropriate response while the use of blast-furnace slag cements met with favor in several European countries.The durability of contemporary concrete is discussed in view of changed technology and performance requirements. Blast-furnace slag cements are found to provide desirable dense microstructures and chemical immunity to attack by sulfates and alkalies.The implications for performance of concrete of heat development during curing are discussed as a new feature, less recognized in past technology. Application of supplementary testing is suggested, in particular isothermal and adiabatic calorimetry. The effective use of the heat of hydration and of blended cements could thus be assured.
Resistance to Freezing and Thawing of Silica Fume Concrete
Authors: Aïtcin P-C , Vezina D 
Published: January 2010

Abstract
The resistance to freezing and thawing of a concrete containing silica fume that was used during the construction of an experimental section on highway A25 in Montreal was done according to ASTM Test for Resistance of Concrete to Rapid Freezing and Thawing (C 666). The original mix was modified so that silica fume replaced three times its weight of cement.
The use of silica fume did not create any particular problems as far as the air content and slump were concerned except perhaps that slightly higher losses were observed during the transportation in comparison to the regular mix. The 28- and 91-day compressive strength results proved that silica fume has been more active than three times its cement weight.
The tests show that the resistance to freezing and thawing of the silica fume concrete was far superior to the plain concrete used for the completion of the project. The length increase and the absorption of the silica fume concrete were about or less than half of those observed with the regular mix. The durability factor of the silica fume concrete was 83 at the end of the test whereas the regular mix durability factor was only 68.
Effect of Fineness on Properties of Classified Cements
Authors: Kumar A , Roy DM 
Published: January 2010

Abstract
The effect of fineness of cement clinkers upon their early age hydration characteristics is presented. Class C (American Petroleum Institute [API] classification) or ASTM Type III portland cement was separated into three new fractions of varying surface area using an air classifier. Thermogravimetry, X-ray powder diffraction, and scanning electron microscopy were used to follow hydration in pastes up to 28 days. Microhardness measurements were also conducted. Mortars were used to follow compressive strength development up to 180 days.
Results indicate low surface area cements produce significantly lower strengths at early ages. Values of compressive strength for mortars made with cements having surface areas equal to or greater than 190 m2/kg (Blaine) reach comparable values in 90 days.
Correlation of Hardened Concrete Air-Void Parameters Obtained by Linear Traverse with Freeze-Thaw Durability as Found by ASTM C 666
Authors: Walker HN 
Published: January 2010

Abstract
The spacing factor for the proportional number of small air voids ¯Lps as proposed by Walker in 1980 and the air-void parameters normally obtained by ASTM Practice for Microscopical Determination of Air-Void Content and Parameters of the Air-Void System in Hardened Concrete (C 457) were each correlated with the durability factor and weight loss found by ASTM Test for Resistance of Concrete to Rapid Freezing and Thawing (C 666) Procedure A for 151 concretes. The correlation coefficients were examined, and it was found that for the durability factor the classical spacing factor from ASTM C 457 gave a slightly but not significantly better correlation than did ¯Lps. The 151 concretes were divided into three groups according to their source. In no case did the correlation obtained from ¯Lps significantly exceed the spacing factor calculated from ASTM C 457.
Measures of the Workability of Steel Fiber Reinforced Concrete and Their Precision
Authors: Johnston CD 
Published: January 2010

Abstract
Measurements of the workability of freshly mixed steel fiber reinforced concrete have been conducted using the traditional slump test, the British Standard V-B test and the test for time of flow through an inverted slump cone recently issued as ASTM Test Method for Time of Flow of Fiber Reinforced Concrete Through Inverted Slump Cone (C 995). Differences between the tests in terms of the extent to which they assess the stability, mobility, and compactability of fresh concrete are identified, and relationships between the results of each type of test are discussed in this context. The single-operator and between-operator precision of the results for each type of test are examined using four operators repeating each test three times on a total of 18 different mixtures with aggregate maximum size, fiber content, and fiber aspect ratio as the variables. Precision is analysed in terms of both standard deviation and coefficient of variation, and the dependence of each of these measures of precision on the magnitude of the mean is examined in terms of correlation coefficients. Using limits within which 90% of the 72 results for single-operator standard deviations fall, criteria suitable for precision statements are established for each of the three tests.
Studies of the Hydraulic Properties of Belite Middling Slime
Authors: Yanev I , Radenkova-Yaneva M 
Published: January 2010

Abstract
Hydraulic properties of belite middling slime obtained as a byproduct in the production of aluminum oxide from nonbauxite materials have been studied. For the purposes of the investigation belite slime and hydraulic lime were mixed in different proportions. Two types of admixtures were used, and their effect on the processes of hydration of the belite slime and strengths of the pastes with equal workability was studied. Development of the processes of hydration and strengths versus time of hydration was studied. By means of the scanning electron microscope, calcium-hydrosilicate phases were identified and a mechanism for their formation was proposed. The results obtained are discussed, and for the investigated binders suitable ranges of application are suggested.
Optimizing the Amount of Class C Fly Ash in Concrete Mixtures
Authors: Majko RM , Pistilli MF 
Published: January 2010

AbstractThis paper describes the results of a two part research program on several laboratory air-entrained concrete mixtures designed to contain increasing amounts of moderately cementitious Class C fly ash. In the first part of the paper, a Type A admixture was used in half of the mixtures, treating both the portland cement Type I and fly ash (15% calcium oxide). In the second part of the paper, three other Class C fly ashes (9 to 12% calcium oxide) were extensively tested in concrete that contained a Type A admixture (but this time treating only the cement). Two very high lime fly ashes (25 to 30% calcium oxide) were also tested in concrete mixtures.All the fly ash concrete mixtures, provided they were properly air-entrained, showed excellent freeze-thaw durability (85 to 95% relative durability [RDF]) and good air-void parameters even at high fly ash contents. The setting times for the fly ash mixtures were longer by 4 to 6 h in the presence of a water reducer and very high fly ash contents (119 to 178 kg/m3 [200 to 300 lb/yd3]).Also in Part 1, the optimal fly ash replacement (criteria is 28-day compressive strengths and 1:1 replacement basis) was 25% without a water reducer and &gt;33% with a water reducer at 356-kg/m3 (600-lb/yd3) cementitious material. For 297-kg/m3 (500-lb/yd3) cementitious material, these values changed to 20% and &gt;33%, respectively. Again using 28-day strengths and pound for pound replacement as the criteria, the optimal fly ash replacement at 356-kg/m3 (600-lb/yd3) cementitious material was &gt;50% for Crawford fly ash, 33% for Will Co. fly ash, and 25% for Joliet fly ash. At 297-kg/m3 (500-lb/yd3) cementitious material, these optimum replacements were 25%, &gt;40%, and slightly less than 20%, respectively.
Experimental Examination of Fly Ash Concrete
Authors: Marusin SL 
Published: January 2010

Abstract
Five mixtures were prepared from pure chemicals (tricalcium aluminate, calcium hydroxide, gypsum and 6% sulfurous acid) to examine the reactions of calcium sulfite with calcium aluminate by scanning electron microscope (SEM) procedures. Subsequently, two series of concrete mixes using the pozzolan cements were prepared: one to investigate the relative effects of calcium sulfite and calcium sulfate at constant calcium hydroxide and fly ash levels and the second to investigate the relative effects of sulfite and calcium hydroxide at a constant fly ash level. A comparison of effects of sulfite and sulfate and a comparison of calcium hydroxide and calcium sulfite were made using values of compressive strength and SEM analyses of the samples. Photomicrographs of microstructures and X-ray analyses were used to illustrate the findings.
Investigation of Cement for Concrete to be Used in Structures Near Seawater
Authors: Muravljov M , Jevtić D 
Published: January 2010

Abstract
The paper deals with experimental research concerning the use of cement with the addition of slag when preparing concrete with certain desired properties. Shown are results of experimental research using cement with the addition of 20% slag, crushed aggregate, water, and admixtures, and one high-range water reducer and one “water-proofer” in order to obtain water resistant concrete of high compactness and high strength. The concrete obtained satisfied the desired conditions, using the admixtures, having a low water cement ratio (W/C) but having very good workability. The second part of paper deals with the determination of cement resistance to aggressive water. Since a cement with a sufficiently low percentage of tricalcium aluminate necessary to be resistant to seawater is not always available, we suggest the use of concrete of the highest obtainable density. The coefficient of seawater resistance is obtained by comparing the flexural strength of specimens cured for six months in ordinary water and specimens cured in simulated seawater solution for the same period of time. A higher coefficient of resistance is obtained on specimens with a low W/C, using admixtures compared to those without admixtures, both being of the same consistency in spite of the usage of cement containing a higher percentage of tricalcium aluminate.
Diagnostic Monitoring of the Physio-Chemical Processes in Hydrating Cement Paste
Authors: McCarter WJ , Afshar AB 
Published: January 2010

Abstract
This paper details a novel electrical technique for monitoring the chemical and physical changes occurring within cement paste. The present study has concentrated on the initial 24 h after gaging with water and investigates the influence of retarders, accelerators, and cements of different type on electrical response. A microcomputer-controlled data acquisition system was developed to obtain results that can be used to obtain accurate electrical response/time curves. This is an advancement on earlier techniques. The work has correlated changes in electrical response with known chemical changes and structure building processes in cement paste. The method described also offers a technique for assessing the influence of chemical additives on the setting and hardening processes.
Effect of Rheological Properties of Cement Pastes on Workability of Mortars
Authors: Atzeni C , Massidda L , Sanna U 
Published: January 2010

AbstractWith a view to establishing a relationship between the rheological behavior of cement pastes with varying water/cement (W/C) ratios and the workability of different mortars, rotoviscosimetric (hysteresis cycle and transient) tests were conducted on the pastes, and slump and flow tests were performed on the mortars. Yield value was taken as the parameter representative of paste rheology. Because of the absence of a standardized slump test for mortars, a special truncated cone was designed. The τo values obtained in the rotoviscosimetric tests are represented as a function of the W/C ratio; and the slump and flow tests are represented as a function of the aggregate/cement (A/C) ratio.The possibility of correlating τo of the pastes with the results of slump and flow tests conducted on mortars is then illustrated. A dimensionless parameter is proposed, which contains both the terms of mortar composition and the parameter τo of the pastes, with which workability measurements can be unequivocally correlated. By this means the workability of a mortar can be derived from the knowledge of the rheological properties of the paste of given composition used in its manufacture.Finally, the advantage of introducing, in addition to the other elements characterizing the cement, a rheological factor for deriving the workability, however, expressed, is discussed.
Assessing Fire Damage of Concrete by the Ultrasonic Pulse Technique
Authors: Chung H-W , Law KS 
Published: January 2010

Abstract
When a concrete member is exposed to fire, the exterior of the member is heated up drastically, while the interior remains at a relatively low temperature. Only a thin surface layer of the concrete is subjected to severe damage. Knowledge of the extent of damage is most useful to the engineer in estimating the repair work. Thickness of the damaged layer can be expediently assessed by measuring the velocity of ultrasonic pulses along the surface. Accuracy of this technique has been investigated with a series of tests in which the concrete was heated to various temperatures. Test results indicate that the method of assessment is reasonably accurate. However, extensive cracking of concrete at very high temperatures may make the ultrasonic measurements very difficult and, hence, limits the applicability of the technique.
Mathematical Evaluation of the Quality of Repairs on Concrete Specimens
Authors: Kostrenčić Z , Bjegović D , Balabanić G 
Published: January 2010

Abstract
By comparing ultrasound pulse velocities before and after repairs on concrete and reinforced concrete structures, it is possible to assess the efficiency of repairs. Two statistical ways are shown in the paper: (1) comparing the velocities and using t-test (Student) and (2) using the x2-test. The former is good in application when individual repairs are considered, and the latter is good when a great number of repaired places is under consideration, and the success and the stability of the whole structure is assessed. The methods were applied on bridge prestressed beams and the advantages of each are shown in examples.
Corrosion of Reinforcing Steel in Concrete Containing Slag or Pozzolans
Authors: Maslehuddin M , Al-Mana AI , Saricimen H , Shamim M 
Published: January 2010

Abstract
Use of fly ash, silica fume, natural pozzolans, and blast-furnace slag in concrete is becoming increasingly common. Incorporation of these materials improves the durability of concrete. But as yet there are few quantitative data available on the effect of these materials on long-term corrosion of steel reinforcement. Such data will help the concrete technologists to select the proper type of materials to produce dense and impermeable concrete to withstand aggressive service environments.
In this investigation, the long-term corrosion-resisting characteristics of concretes made with two fly ashes, a natural pozzolan, a blast-furnace slag cement, and a preblended portland-fly ash cement were evaluated. Specimens were immersed in 5% sodium chloride solution for a period of more than five years, and the corrosion activity was evaluated by monitoring the half-cell potentials and measuring the corrosion rate of embedded steel using linear polarization resistance technique. Results indicate that addition of pozzolans or slag increases the corrosion-resisting characteristics of concrete. The corrosion rate of steel in concrete made with blast-furnace slag cement is lower than in other concretes.