bluuebunny/crossref_metadata_2025_split huggingface dataset:
Some Recent Problems with Air-Entrained Concrete
Authors: Hover KC 
Published: January 2010

Abstract
Several problems are identified in regard to air-entrained concrete, which include the accuracy of the pressure air meter (ASTM C 231), the accumulation of air voids at the coarse aggregate surface, excessive loss of air volume in transit or in pumping, and the need for greater precision and detail in specification requirements for air-entrained concrete. Data are presented from four recent construction projects from a wide geographical range in the United States.
Effect of Curing Conditions on the Compressive Strength and Elastic Modulus of Very High-Strength Concrete
Authors: Asselanis JG , Aitcin P-C , Mehta PK 
Published: January 2010

Abstract
With ordinary concrete, although a water content corresponding to about 0.3 water/cement ratio by weight is adequate for complete hydration of portland cement, in practice water/cement ratios in the range of 0.5 to 0.7 are used to achieve proper workability. Thus, ordinary concrete shows rather low strength and high permeability at early ages. With the progress of cement hydration reactions, both strength and impermeability show dramatic improvement as the products of hydration fill up the empty or water-filled spaces present in the cement paste.
Basic Creep Formula for Aging Concrete: Sinh-Double Power Law
Authors: Bažant ZP , Chern J-C , Wu Y-G 
Published: January 2010

Abstract
An alternative simple formula for the compliance function for basic creep of concrete is proposed and evaluated. It consists of a hyperbolic sine combined with the double power law. For short creep durations it asymptotically approaches the double power law, and for very long durations it asymptotically approaches the logarithmic law, which is the same behavior as for the previously formulated log-double power law. The formula allows a good fit of basic creep data from the literature. It represents them as well as the log-double power law and better than the double power law, although the difference is not large. Compared to the double power law, a significant improvement is obtained in the final slope of the creep curves. Compared to the log-double power law, the proposed formula is somewhat better for extension into the short-time dynamic range.
A Damage Model for Sulfate Attack of Cement Mortars
Authors: Ouyang C 
Published: January 2010

Abstract
A model for cement mortars under sulfate attack is proposed based on a progressive fracturing concept. An initial damage of mortar is defined as a function of the Powers' gel space ratio. The sulfate attack evidenced by the expansion of the matrix is incorporated as additional nucleated voids which increase the initial damage existing before the loading. The compressive properties of cement mortars under sulfate attack are predicted well by this model. Expansion limits for sulfate attack computed by this model agree well with those proposed by Mather and Patzias.
Statistical Characteristics of New Pin Penetration Test
Authors: Carino NJ , Tank RC 
Published: January 2010

Abstract
Researchers at the University of Saskatchewan have developed a new test for estimating the in-place strength of concrete. The method, known as the pin penetration test, involves driving a small pin into the concrete surface using a spring-loaded driver. The penetration of the pin creates a small indentation whose depth is measured. The pin penetration is inversely related to the strength of concrete. This paper provides information about the within-test variability of the method and about the correlation relationship between compressive strength and pin penetration. Test results show that a standard deviation with a value of about 0.015 in. (0.038 mm) describes the within-test variability. The correlation relationship is nonlinear for compressive strengths between 1000 and 5800 psi (6.9 to 40.0 MPa) and depends on the water-cement ratio of the concrete. For compressive strength less than about 4000 psi (27.6 MPa), the correlation relationship is not strongly dependent on water-cement ratio, and a straight line adequately represents the relationship. However, the correlation relationship obtained in this study differs from that reported by others.
The Morphology of Air-Entrained Voids, at Early Age
Authors: Rashed AI , Monteiro PJM , Williamson RB , Bastacky J 
Published: January 2010

Abstract
The morphology of air-entrained voids has been observed using the low-temperature scanning electron microscope (LTSEM). The entrained voids have been examined in cement paste specimens at an age of 5 min.
Properties of Concrete at Early Ages
Authors: Carino NJ , Jennings HJM , Snell LM 
Published: January 2010

Abstract
What should be done to improve our understanding and appreciation of the properties of concrete at early ages? This question was the basis for an Engineering Foundation Conference on the topic of “The Properties of Concrete at Early Ages.” To answer the above question, the conference participants developed the recommendations summarized in this technical note. The recommendations addressed the need to: gain a better understanding of cement paste microstructure; improve codes and standards; control temperature rise during construction; and educate the users of concrete.
Microstructural Development in a High-Strength Concrete Containing a Ternary Cementitious System
Authors: Sarkar SL , Baalbaki M , Aitcin P-C 
Published: January 2010

Abstract
The sudden upsurge of mechanical strength at 12 h in a silica-fume/fly-ash high-strength concrete led the authors to investigate the cause and to determine the microstructural characteristics of this concrete with progressive hydration from 1 to 91 days to correlate its microstructural development with its strength enhancement pattern.
Improvement of Concrete Strength Statistical Control
Authors: Leshchinsky AM 
Published: January 2010

Abstract
Extensive research is being carried out in the area of concrete strength statistical control. Acceptance control plans are improved to reduce consumer's and producer's risks: the producer's risk consists in rejecting good-quality concrete, while that of the consumer, in accepting a substandard concrete. ACI 318 provides a low-level risk for a producer and a high-level risk for a consumer. It is demonstrated that the consumer's risk substantially decreases with the introduction of the quality assurance system.
The need to provide several acceptance criteria with various required probabilities of specified strength f′c and consumer's allowable risk in national codes is analyzed.
In addition, two procedures are given: the first consists in taking into account the actual concrete strength distribution, and the second, in rejecting gross errors.
Introduction to Symposium on Characterization of Hydraulic Cements
Authors: Hooton RD 
Published: January 2010

Abstract
[The Symposium on Characterization of Hydraulic Cements, held in San Antonio, TX, on 5 Dec. 1990, was sponsored by ASTM Committee C-1 on Cement. Five papers from the symposium are presented in this issue of Cement, Concrete, and Aggregates. R. Doug Hooton, associate professor at the University of Toronto, presided as symposium chairman and Leslie J. Struble served as symposium cochairman. R. Doug Hooton provided this Introduction—Editor.]
Quantitative Clinker Microscopy with the Light Microscope
Authors: Campbell DH , Galehouse JS 
Published: January 2010

Abstract
Microscopical methods for quantitative determination of phase percentage in rocks, bricks, portland cement clinkers, and other composite materials, although time consuming, are among the most reliable techniques available. For particle mounts on glass microscope slides, the line, ribbon, or Fleet methods are used. For thin sections or polished sections, the linear traverse or point-counting methods are recommended. Microscopically determined percentages can obviously include crystalline and amorphous phases, which is more than X-ray diffraction can clearly reveal. Microscopical data can be converted into oxides, giving a chemical analysis. The gathering of microscopical data is facilitated by electronic tallying devices and semiautomatic mechanical stages. Finally, microscopical data, properly gathered, can be treated statistically with high levels of confidence. One should be aware, however, of the limits that each microscopical method entails.
Quantitative Phase Analysis of Clinker Using X-Ray Diffraction
Authors: Struble LJ 
Published: January 2010

Abstract
Many difficulties are encountered in quantitative X-ray diffraction analysis of portland cement and clinker. Despite these difficulties, it appears that, with adequate experimental procedures, the major clinker phases can be determined with an absolute accuracy of 2 to 5% (by weight of the total clinker) for alite and belite and 1 to 2% (by weight of the total clinker) for aluminate and ferrite. A task group in ASTM is exploring X-ray diffraction methods for quantitative phase analysis of cement and clinker. The group has made considerable progress towards proposing a standard test method for aluminate, ferrite, and magnesium oxide. Using specified experimental procedures, preliminary results indicate that these three phases may be determined in clinker with an absolute accuracy of 1.7%. After the task group completes work with these phases, it plans to continue with the calcium silicates.
Cement Clinker Characterization by Scanning Electron Microscopy
Authors: Stutzman PE 
Published: January 2010

Abstract
The scanning electron microscope (SEM) is becoming increasingly recognized as an important instrument for the study of portland cement clinker, cement, and concrete. Images of clinker surface topography are used to study particle size and shape, as well as fracture surface features. Microstructural features such as phase distribution and abundance are obtained by imaging polished surfaces. X-ray microanalysis provides qualitative and quantitative elemental composition and images of element distribution. Computer-based image analysis systems are used to process microscope images to enhance details (such as the separation of individual phases) and image analysis for the measurement of features (such as phase abundance). The linking of the SEM with X-ray microanalysis and image analysis under computer control will provide automated, quantitative, and consistent analysis of portland cement clinker.
An Analysis of Factors Affecting Particle-Size Distribution of Hydraulic Cements
Authors: Malghan SG , Lum L-SH 
Published: January 2010

Abstract
Particle-size distribution of hydraulic cements plays an indispensable role in controlling the product quality and maintaining reliable performance in end applications. Selection of particle-size measurement methods is becoming increasingly complex due to the availability of a variety of instruments based on different measurement principles. This paper discusses the primary criteria to be met by a particle-size distribution analzer for applications in hydraulic cement characterization. Among the several methods available for measuring the particle-size distribution, a light diffraction technique was utilized to examine the effect of dispersion solvents on the resulting size distribution. Distilled water, distilled water containing a polyacrylate surfactant, isopropyl alcohol, and a commercially available organic surfactant were used as dispersion solvents. The resulting data are analyzed with respect to variations due to the dispersion solvents and factors responsible for the observed variations.
Effect of Extended Use of Set-Retarded Concrete in Hot Weather
Authors: Mittelacher M 
Published: January 2010

Abstract
Test results from four major Florida projects were reviewed for effects of set-retarder use on maintaining slump and strength of concrete held in the mixer for extended time periods in hot weather conditions. Admixtures included ASTM Specification for Chemical Admixtures for Concrete (C 494) Type D water-reducing and retarding and Type G high-range water-reducing and retarding admixtures. Four different cement-admixture combinations were used. Design strengths ranged from 27.6 to 69.0 MPa (4000 to 10 000 psi). The test samples representing the longest delivery times were found to have maintained the specified slump. Their strength levels generally remained at, or exceeded, the average strength of the respective concrete class.
Some Applications of AC Impedance Spectroscopy in Cement Research
Authors: Gu P , Xie P , Beaudoin JJ 
Published: January 2010

Abstract
AC impedance techniques have been recently applied to investigate the electrical properties of hydrating cement pastes. A review of recent applications of AC impedance spectroscopy (ACIS) in cementitious materials studies including some relevant applications to microstructural characterization, silica fume content estimation, W-C ratio determination and microcracking of cement paste are presented.
High-Strength Concrete Properties Derived from Compressive Strength Values
Authors: Khayat KH , Bickley JA , Hooton RD 
Published: January 2010

Abstract
The determinations of modulus of elasticity and flexural and splitting tensile strengths often involve complicated testing procedures compared to compressive strength testing. These properties can be estimated using existing relationships between them and compressive strength values. However, most of the existing correlations have been derived for mixtures with compressive strengths less than 80 MPa and may not be applicable to mixtures of greater strengths. This paper compares compressive strength, splitting tensile strength, flexural strength, and modulus of elasticity values to similar results predicted by national codes and alternatives suggested by various researchers. Commercially available and laboratory-prepared concrete mixtures with 28-d compressive strengths of 45 to 110 MPa were tested.
The Passivation of Reinforcing Steel Exposed to Synthetic Pore Solution and the Effect of Calcium-Nitrite Inhibitor
Authors: Tullmin M , Mammoliti L , Sohdi R , Hansson CM , Hope BB 
Published: January 2010

Abstract
Potentiodynamic polarization studies were conducted on rebar steel in a simulated cement paste pore solution containing sodium chloride, with and without additions of calcium-nitrite inhibitor. The rebar steel passivated spontaneously and displayed an extensive passive potential range in both cases. Surprisingly, however, passivity breakdown was observed to occur at a lower potential in the inhibited solution. XPS surface analysis indicated a similar composition of the passive films formed in the inhibited and uninhibited pore solutions. Only trace amounts of nitrogen were detected in the passive films. On the basis of the XPS results and the reported nitrite-inhibition mechanism, it would appear that the smaller passive potential range associated with the inhibitor additions is related to a decrease in pH recorded after the inhibitor addition.
Amendment of Appendix X2 in ASTM C 917 Evaluation of Cement Uniformity from a Single Source
Authors: Sykora V 
Published: January 2010

Abstract
Test Method for Evaluation of Cement Strength Uniformity from a Single Source (ASTM C 917) in the ASTM Annual Book of Standards, Volume 4.01, Cement, Lime, and Gypsum provides methods to evaluate the cement strength uniformity from a single source. Test data comparing 1976 through 1977 and 1991 show a general increase in strengths over that period of time. In 1976, 45% of the labs had annual average 7-day strengths less than 27.6 MPa (4000 psi), while in 1991 none of the plants had averages below that level. The data show the cement industry, overall, shipped a more consistent product in 1991 compared to 1976 through 1977. The percentage of plants with a standard deviation below 2.1 MPa (300 psi) at 7 days increased from 63 to 81% during that time period. A higher percentage of plants had the total coefficient of variation and corrected deviations below 6%. The testing error remained the same with the 1976 data and the 1991 data, but the testing error coefficient of variation improved.
Properties of a Non-Film Forming Latex in Ceramic Tile Mortar
Authors: Kuhlmann LA 
Published: January 2010

Abstract
Latexes currently used for modifying portland cement contribute many property improvements to mortar and concrete. Many different polymers are used to make these latexes, but all have one thing in common: they form a film at normal working temperatures. It is the formation of this film that is generally understood to be critical to the performance of these latexes in portland cement and responsible for certain of the property improvements in the hardened mortar and concrete.
Contrary to this accepted understanding, an experimental latex has been developed for use in portland cement that does not form a film at room temperature. Instead, the latex particles maintain their integrity as spheres after the portland cement mixture hardens and still provides property improvement in the hardened mixture. The lack of film-formation also eliminates the stickiness during finishing and the surface crusting from air-drying that are typical of the film-forming latexes used in portland cement.
Tests of this latex were conducted on mortar with ceramic tile and compared to mortars using standard film-forming latexes. Workability, compressive strength, and shear bond of the mortars were evaluated. In addition, flexural bond strength of tile-to-plywood and cement backerboard was measured using a new test procedure.
Acrylic Powder Modified Portland Cement
Authors: Ci X , Falconio RR 
Published: January 2010

AbstractThe key functions of polymer in modifying cement for both indoor and outdoor applications have been identified and demonstrated through years of practice since the early 1960s. The effectiveness of using pure acrylic polymer in cement modification can be credited to the unique acrylic chemistry in combination with special polymer designs and processes. Both acrylic powder and acrylic latex rely on the acrylic backbone to provide excellent performance and durability, especially for exterior applications. Acrylic redispersible powder recently developed preserves acrylic latex performance in mechanical strength, adhesion, and water resistance as demonstrated by various tests under wet- and dry-exposure conditions. In addition, use of acrylic powder as a “one-package” alternative to latex facilitates on-site handling, environmental protection, and reduces packaging and transportation costs.This paper presents the results of performance comparsion between acrylic redispersible powder and acrylic latex in cement modification. The polymer-modified mortar properties were evaluated and compared in both a typical concrete repair mortar and a ceramic tile formulation. The exterior durability of acrylic powder modified repair mortar was demonstrated through exterior exposure studies. The modification efficiency of acrylic powder was also studied at different polymer levels in a patching formulation that compared favorably to other commercial powders at lower polymer level usage.
Tensile and Compressive Strength of Silica Fume-Cement Pastes and Mortars
Authors: Toutanji HA , El-Korchi T 
Published: January 2010

Abstract
The effect of silica fume on the compressive and uniaxial direct tensile strength of portland cement paste and mortar is reported. Sixteen and 25% of the cement used in the paste and in the mortar, measured by mass, was replaced by silica fume. Four different W/C ratio mixtures were tested: 0.22, 0.25, 0.28, and 0.31. The super-plasticizer content was adjusted for each mixture to provide a sufficient amount for efficient dispersion of the cement and silica fume particles, but also to make sure that there would be no excess of this additive that might lead to effects such as bleeding.
Results show that the partial replacement of cement by silica fume increases the compressive strength of mortar but has no effect on the compressive strength of paste. Results also show that the partial replacement of portland cement by silica fume decreases the tensile strength of both paste and mortar. The reduction in the strength of paste was greater than the reduction in the strength of mortar. Results were verified by statistical analysis using hypothesis testing at a 95% confidence level. The uniaxial tensile strength results were obtained using the cementitious composites axial tensile technique (CCATT).
The relation between the tensile strength and compressive strength of materials with and without silica fume was obtained. The ratios of tensile to compressive strength of paste and of mortar were decreased with increasing silica fume content.
Mechanical Properties of Normal to High-Strength Steel Fiber-Reinforced Concrete
Authors: Khaloo AR , Kim N 
Published: January 2010

Abstract
A total of 84 specimens were tested to study the effect of concrete strength on the mechanical properties of concrete reinforced with randomly distributed steel fibers. The concrete strengths investigated include 25 MPa for normal-strength (NSC), 50 MPa for medium-strength (MSC), and 69 MPa representing high-strength concrete (HSC). Fiber content ranges from 0 to 1.5% by volume of the concrete matrix. The influence of concrete strength on the compressive strength, splitting tensile strength, and modulus of rupture of steel fiber-reinforced concrete (FRC) is presented. Based on the limited number of specimens tested, it was concluded that HSC provides considerable improvement in compressive strength for fiber content of up to 1% compared to that of NSC and MSC. Also, modulus of rupture of NSFRC considerably improves due to fiber compared to those of MSFRC and HSFRC. Splitting tensile strength results do not indicate a clear dependency to concrete compressive strength.
Factors Influencing Flow and Strength of Standard Mortars and Reappraisal of ASTM Test Methods for Fly Ash
Authors: Helmuth R 
Published: January 2010

Abstract
Modified Test Methods for Sampling and Testing Fly Ash or Natural Pozzolans for Use as a Mineral Admixture in Portland-Cement Concrete (ASTM C 311) Pozzolanic (Strength) Activity Index tests with five fly ashes and two portland cements were done to compare results with those of standard tests. When sand contents (at constant water and cement contents) were varied, strengths of 38°C cured mortars decreased (−30 to −50 kPa/g of sand added in mixes containing 1370 to 1570 grams of sand) for different cement/fly ash blends. When water contents (at constant sand contents) were varied, strengths varied (−125 to +190 kPa/mL), strengths tending to increase because of paste volume increases with water content. Flow of mortars in both kinds of tests increase nearly linearly with paste volume fractions; the slopes are related by a factor of 0.60 ± 0.04. Accelerated curing at 38°C for tests at 28 days usually yields higher relative strengths than after curing at 23°C for 91 days. Multiple linear regression equations using both kinds of test data are solved at specified flow and strength values to determine proportions and mortar volume yields. This more general performance test ranks fly ashes (or cementitious mixtures) by mortar volume yield at equal flow and strength, and is suggested as a candidate to replace the present Strength Activity Index test.