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Author : Duane E. Amsler
Publisher :
ISBN 13 :
Total Pages : 48 pages
Book Rating : 4.:/5 (359 download)
Download or read book Techniques for Measuring Air Void Characteristics of Concrete written by Duane E. Amsler and published by . This book was released on 1973 with total page 48 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Joseph F. Lamond
Publisher : ASTM International
ISBN 13 : 0803133677
Total Pages : 661 pages
Book Rating : 4.8/5 (31 download)
Download or read book Significance of Tests and Properties of Concrete and Concrete-making Materials written by Joseph F. Lamond and published by ASTM International. This book was released on 2006 with total page 661 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Steven Michael Trost
Publisher :
ISBN 13 :
Total Pages : 56 pages
Book Rating : 4.:/5 (426 download)
Download or read book Measuring Air Void Characteristics of Oklahoma Air-entrained Concrete Using the Air Void Analyzer (AVA) written by Steven Michael Trost and published by . This book was released on 2009 with total page 56 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author :
Publisher :
ISBN 13 :
Total Pages : 11 pages
Book Rating : 4.:/5 (614 download)
Download or read book Precision of the Air Void Characteristics Measurement by ASTM C 457 written by and published by . This book was released on 1996 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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 : Hamdi Celik Ozyildirim
Publisher :
ISBN 13 :
Total Pages : 36 pages
Book Rating : 4.:/5 (359 download)
Download or read book Distribution of Voids in Field Concrete written by Hamdi Celik Ozyildirim and published by . This book was released on 1978 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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 : R. Pleau
Publisher :
ISBN 13 :
Total Pages : 9 pages
Book Rating : 4.:/5 (125 download)
Download or read book Practical Considerations Pertaining to the Microscopical Determination of Air Void Characteristics of Hardened Concrete (ASTM C 457 Standard) written by R. Pleau and published by . This book was released on 1990 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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 : H. Sommer
Publisher :
ISBN 13 :
Total Pages : 7 pages
Book Rating : 4.:/5 (125 download)
Download or read book The Precision of the Microscopical Determination of the Air-Void System in Hardened Concrete written by H. Sommer and published by . This book was released on 1979 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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 : Lokman Ng
Publisher :
ISBN 13 :
Total Pages : 88 pages
Book Rating : 4.:/5 (656 download)
Download or read book Studying Air Properties in Hardened Portland Cement Concrete with Linear Traverse Method written by Lokman Ng and published by . This book was released on 2010 with total page 88 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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 : A. M. Ramezanianpour
Publisher :
ISBN 13 :
Total Pages : 14 pages
Book Rating : 4.:/5 (125 download)
Download or read book Evaluation of Two Automated Methods for Air-Void Analysis of Hardened Concrete written by A. M. Ramezanianpour and published by . This book was released on 2010 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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 : American Concrete Institute
Publisher : American Concrete Institute
ISBN 13 : 0870311948
Total Pages : 660 pages
Book Rating : 4.8/5 (73 download)
Download or read book Specifications for Structural Concrete, ACI 301-05, with Selected ACI References written by American Concrete Institute and published by American Concrete Institute. This book was released on 2005 with total page 660 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author :
Publisher : ASTM International
ISBN 13 :
Total Pages : 875 pages
Book Rating : 4./5 ( download)
Download or read book Significance of Tests and Properties of Concrete and Concrete-Making Materials written by and published by ASTM International. This book was released on 1978 with total page 875 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : C. H. Best
Publisher : ASTM International
ISBN 13 : 9780803106123
Total Pages : 886 pages
Book Rating : 4.1/5 (61 download)
Download or read book Significance of Tests and Properties of Concrete and Concrete-Making Materials written by C. H. Best and published by ASTM International. This book was released on 1985-02 with total page 886 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Pengyu Xie
Publisher :
ISBN 13 :
Total Pages : 61 pages
Book Rating : 4.:/5 (13 download)
Download or read book Evaluation of Thermal Properties and Air Void Characteristics of Porous Concrete written by Pengyu Xie and published by . This book was released on 2017 with total page 61 pages. Available in PDF, EPUB and Kindle. Book excerpt: Porous concrete is becoming an attractive pavement solution due to its great performances in mitigating urban heat island (UHI) effect and managing storm water. As a heterogeneous material, the properties of cement-based porous concrete are complicated to quantify and hard to predict. This thesis focused on the evaluation of thermal properties and air void characteristics of porous concrete. The thermal properties of aggregates, cement pastes, and porous concretes were measured by transient plate method (TPS) and steady-state heat flow meter method, respectively. X-ray computed tomography (CT) technique was utilized and three-dimensional (3-D) pictures were treated to analyze the microscopic structure of air voids in porous concrete. The existing analytical models were employed to estimate thermal conductivity of pervious concretes and compared to experimental measurements. The tests results show that thermal conductivity and heat capacity of cement paste increases as water cement ratio increases. Meanwhile, for the same mix design, the thermal properties of different cement paste samples had few variations. However, the porous concrete is very heterogeneous and the same mix design cannot ensure the similar porosity; instead, significant variations of porosity were observed. The existing analytical results did not show satisfactory prediction results of thermal conductivity as compared to testing results. This indicates the existing models are not suitable to estimate the thermal conductivity of porous concrete. This is because the models ignore the complex microscopic structures of porous concrete. Based on the CT-scanned images, within the horizontal plane of cylindrical sample, slight differences of normalized projected lengths of air voids were observed in the orthogonal horizontal directions; while the normalized projected length of connected voids in vertical direction was found smaller than those in horizontal directions. The smaller aggregates tend to form the longer air void length in porous concrete. The curvatures of air voids for smaller aggregates are greater than that of larger aggregates. Meanwhile, within the same mix design, the curvature of air voids increases with the increasing of porosity. The porosity and aggregate size do not have significant influences on the ellipticity and tortuosity of air voids within porous concrete. However, with the increase of porosity, the air voids tend to have the greater equivalent diameter.
Author : Hamdi Celik Ozyildirim
Publisher :
ISBN 13 :
Total Pages : 36 pages
Book Rating : 4.:/5 (1 download)
Download or read book Comparison of Air Void Content Measurements in Fresh Versus Hardened Concretes written by Hamdi Celik Ozyildirim and published by . This book was released on 1990 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt: This study compares the air content of freshly mixed and hardened concretes. At the fresh stage, pressure meters (Types A and B) and a volumetric meter were used to determine the air content. At the hardened stage, the air content was calculated using the linear traverse method described in ASTM C 457, which is a microscopical procedure. The unit weight and compressive strength of the concretes were also determined. The results show that, at the ranges commonly used in the construction of pavements and bridges, the air content of fresh concrete measured by pressure meters and that determined by the microscopical method for essentially the same concrete after hardening are, for practical purposes, the same. The air content obtained by a volumetric meter as normally run in the field is generally lower than that obtained for the same hardened concretes by the microscopical method. The unit weight and compressive strength correlate well with the air content. It was also shown that adding water to concrete can significantly increase the air content, as well as the slump. Thus, a higher air content in hardened concretes than that indicated by initial measurements with a pressure meter is likely to be present if water is added during placement.
Author : Basil Mark Harris
Publisher :
ISBN 13 :
Total Pages : 864 pages
Book Rating : 4.E/5 ( download)
Download or read book Microscopic Air Void Analysis of Hardened Portland Cement Concrete by the Isolated Shadow Technique written by Basil Mark Harris and published by . This book was released on 1998 with total page 864 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : J. Cahill
Publisher :
ISBN 13 :
Total Pages : 14 pages
Book Rating : 4.:/5 (125 download)
Download or read book The Identification and Measurement of Entrained Air in Concrete Using Image Analysis written by J. Cahill and published by . This book was released on 1994 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt: The use of ASTM C457 ("linear traverse" or "modified point-count methods") for microscopical determination of air-void content and parameters of the air-void system, in hardened concrete has become widespread in the prediction of the durability of concrete in freeze-thaw conditions, and in assessing concrete that has failed in service. More recently a new European Standard, based on linear traverse measurements has been adopted as an efficacy test for air entraining agents. The linear traverse method described in both standards involves identification, counting and, in the Euro Standard, measurement of air-voids. It is laborious, tedious and subjective and the error of the method has not been rigorously assessed. We have explored the possibility of using Image Analysis in conjunction with the linear traverse method to develop less laborious and subjective measurement methods. A number of methods of visualisation of air-voids have been applied to polished samples of hardened concrete which had previously been assessed by the standard linear traverse method. The quality of the surface preparation required for Image Analysis was found to be even more critical than for the standard manual method.
Author : Ravindra K. Dhir
Publisher : Thomas Telford
ISBN 13 : 9780727728258
Total Pages : 512 pages
Book Rating : 4.7/5 (282 download)
Download or read book Specialist Techniques and Materials for Concrete Construction written by Ravindra K. Dhir and published by Thomas Telford. This book was released on 1999 with total page 512 pages. Available in PDF, EPUB and Kindle. Book excerpt: Concrete will be the key material for Mankind to create the built environment of the next millennium. The requirements of this infrastructure will be both demanding, in terms of technical performance and economy, and yet be greatly varied, from architectural masterpieces to the simplest of utilities.Specialist techniques and materials for concrete construction forms the Proceedings of the three day international conference held during the Congress, creating with concrete, 6-10 September 1999, organised by the Concrete technology unit, University of Dundee.
