Techniques for Measuring Air Void Characteristics of Concrete PDF Download
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Author: Duane E. Amsler
Publisher:
ISBN:
Category : Concrete
Languages : en
Pages : 48
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Author: Duane E. Amsler
Publisher:
ISBN:
Category : Concrete
Languages : en
Pages : 48
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Book Description
Author: Joseph F. Lamond
Publisher: ASTM International
ISBN: 0803133677
Category : Technology & Engineering
Languages : en
Pages : 661
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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 11
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Since 1993, the Quebec Department of Transportation requires all its concrete suppliers to demonstrate that their concrete satisfies the requirements of the CSA A23.1 standard as regards the maximum spacing factor of the air void system. This new requirement raises questions about the reproducibility of the ASTM C 457 test method. An interlaboratory study was carried out to verify if the variability of the test method is sufficiently low to allow reliable decisions on the acceptance or rejection of in-place hardened concrete. A total of 18 operators from 13 different laboratories microscopically examined the six concrete slabs used for the study. It is concluded that the average reproducibility coefficient of variation is 14.4 % for the total air content measurement and 14.2 % for the spacing factor measurement. Considering these results, the probability that the measured value of the spacing factor exceeds the mandatory limit of 230 um on a concrete production containing an air void system with a spacing factor of 170 um (the target value proposed in the CSA A23.1 M-94 standard is less than 0.7 % (a propability of error of about 1 %, 5 %, or 10 % is typical of most quality control test methods).
Author: Steven Michael Trost
Publisher:
ISBN:
Category : Air-entrained concrete
Languages : en
Pages : 56
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Author: Lokman Ng
Publisher:
ISBN:
Category : Concrete
Languages : en
Pages : 88
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Book Description
Air void structure in hardened concrete is critical to its durability. This project mainly focuses on investigating the air void system in hardened concrete with the microscopic analysis Linear Traverse Method specified by ASTM Specification C457-08 (Standard Test Method for Microscopical Determination of Parameters of the Air-Void System in Hardened Concrete). To understand the stability of the air void system in concrete, the same concrete mixes were examined with two other methods, pressure meter measurement and Air-Void Analyzer, under fresh state. The comparison of the results from the three methods for fresh and hardened concrete shows that properties of concrete vary in samples within the same batch with the same mix design, samples in different batches of the same mix design and samples with different mix designs. The measured air content from Linear Traverse Method and pressure meter are fairly close to each other, while Air-Void Analyzer measured air content is observed to be lower than that from Linear Traverse Method. The measured spacing factor from Air-Void Analyzer is observed to be higher than that from Linear Traverse Method, while the measured specific surface from Air-Void Analyzer is observed to be lower than that from Linear Traverse Method. However, no strong correlation in the measured air content and measured specific surface between Linear Traverse and Air-Void Analyzer is observed.
Author: Hamdi Celik Ozyildirim
Publisher:
ISBN:
Category : Concrete
Languages : en
Pages : 36
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Book Description
This study was intended to evaluate the air void characteristics of concrete in an attempt to identify, quantitatively or semi-quantitatively, different types of voids and to predict their influence on strength and durability. At the outset, it was anticipated that total air contents and water-- cement ratios of concrete mixtures would reflect the presence of excess water or air voids. However, because it is difficult to determine the water-cement ratio of hardened concrete, an attempt was made to relate the water-cement ratio and the air content, taken as independent variables, to the parameters of the void system that are .readily determined from the hardened concrete. The parameters of the void system considered were 1. The specific surface and the spacing factor calculated from linear traverse data. 2. The constants of a continuous chord frequency distribution curve derived from a probability density function. 3. The mean diameters and the number of bubbles per unit volume determined by a graphical method. The concrete samples were prepared in the laboratory, and the variables included the amount of air entrainment, the water cement ratio, the mixing time, and the mixture temperature. The data on the void system were obtained by utilizing the chord lengths of voids determined by the linear traverse analysis of concrete specimens. Within the framework of the study it was not possible to correlate the combined effect of water and air content with the above mentioned void parameters. A good correlation was obtained between the air contents of fresh and hardened concretes that were properly measured. Satisfactory relationships were established between the measures of resistance to freezing and thawing (weight loss, relative dynamic modulus of elasticity, and the surface rating), and certain parameters-of the void system (the spacing factor, the specific surface, and the diameter of the bubbles).
Author: H. Sommer
Publisher:
ISBN:
Category : Air entrainment
Languages : en
Pages : 7
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Book Description
Twenty laboratories from ten countries took part in an international comparative test to determine the air-void system of hardened concrete. The method of measurement did not seem to have a significant influence on results, but good grinding techniques and the magnifications were important. Further tests were performed at the Viennese Cement Research Institute with the aim of improving the precision of the results. It is recommended that the entrapped and the entrained air voids be counted separately and that the spacing factor be calculated from the entrained air voids only.
Author: A. M. Ramezanianpour
Publisher:
ISBN:
Category : Air-Void Characterization
Languages : en
Pages : 14
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Book Description
Air-void analysis of hardened concrete is typically performed according to ASTM C457-09 ["Standard Test Method for Microscopical Determination of Parameters of Air-Void System in Hardened Concrete," Annual Book of ASTM Standards, Vol. 4.2, ASTM International, West Conshohocken, PA], which can be tedious to perform and is operator subjective. Several alternative automated methods have been proposed, two of which are the Rapid Air 457 and the scanner method developed at Michigan Technological University. In each of these methods, images are collected from contrast enhanced surfaces of polished concrete, and image analysis is performed to calculate air-void system parameters. In this research, 22 concrete samples were examined using these two methods, the air-void system parameters were compared to those obtained from the ASTM C457 standard, and the precision of the results was compared to the recommendations of ASTM standard. It was concluded that the total air content and the spacing factor of the air voids measured by Rapid Air 457 and the scanner method were comparable to the air content and the spacing factor measured according to the standard manual method. Considering the fact that the automated image systems could detect air voids smaller in diameter than those typically seen by an operator, it was found that if these small air voids are counted, calculated spacing factors are smaller than those calculated by the manual method. If small diameter air voids are removed from the analysis, then spacing factors agree fairly well with those calculated by ASTM C457 from stereo-optical microscopy.
Author: R. Pleau
Publisher:
ISBN:
Category : Air voids
Languages : en
Pages : 9
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Book Description
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.
Author:
Publisher: ASTM International
ISBN:
Category :
Languages : en
Pages : 875
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