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Book Effect of Vibration on Air Content of Mass Concrete

Download or read book Effect of Vibration on Air Content of Mass Concrete written by Waterways Experiment Station (U.S.) and published by . This book was released on 1952 with total page 32 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Computer Applications in Air Void System Evaluation

Download or read book Computer Applications in Air Void System Evaluation written by Marcia Jill Simon and published by . This book was released on 1989 with total page 404 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Proceedings of the International Symposium

Download or read book Proceedings of the International Symposium written by and published by . This book was released on 1969 with total page 534 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Effect of Vibration Time Upon Loss of Entrained Air from Concrete Mixes

Download or read book Effect of Vibration Time Upon Loss of Entrained Air from Concrete Mixes written by and published by . This book was released on 1949 with total page 34 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Control of Air Content in Concrete

Download or read book Control of Air Content in Concrete written by David Whiting and published by Transportation Research Board National Research. This book was released on 1983 with total page 96 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Admixtures and special cements

Download or read book Admixtures and special cements written by and published by . This book was released on 1969 with total page 534 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book The Effect of Air Entrainment Upon Compressive Strength of Concrete

Download or read book The Effect of Air Entrainment Upon Compressive Strength of Concrete written by Kent Albert Allemeier and published by . This book was released on 1948 with total page 66 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Properties of Air Bubbles in Air Entrained Concrete

Download or read book Properties of Air Bubbles in Air Entrained Concrete written by Le Tuan Pham and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: It is widely accepted that air entrainment, a purposeful introduction of small air bubbles in concrete, is critical to the long-term durability of concrete in freeze-thaw environments. Air entraining admixtures (AEA) are added to the mixture to stabilize air bubbles created during mixing, ensuring a proper air void system in the hardened concrete. Despite the complexity of creating a suitable air void system in concrete, previous study and experience established the reliability and robustness of such systems under a variety of conditions through use of neutralized vinsol resin (NVR) AEA products. In recent years, synthetic AEAs have been used more frequently due to limited supply of NVR to the concrete industry. With the use of synthetic AEAs, there are more reports of new problems including difficulties in accurately measuring the air content. This study was conducted to find the root cause of the increasing difficulties in controlling the air contents in portland cement concrete associated with synthetic AEAs. Main challenges included the lack of existing techniques to evaluate AEAs and air bubbles in concrete, and lack of data to help identify causes. Given these challenges, a multi-scale experimental study that included testing of field and laboratory concrete, and testing of foam and individual air bubbles was undertaken. The results indicate that the disparity between QC test results and the actual air contents in concrete pavements associated with the use of synthetic AEAs could be attributed to less robust air bubbles stabilized with synthetic AEAs compared to those entrained with NVR and the resulting increased loss of these air bubbles during concrete sampling. The cause of this decreased robustness and resulting air loss was traced directly to the properties of the bubble shells. The shells of air bubbles in concrete entrained with synthetic AEAs were thinner and less stiff than those associated with an NVR AEA. Through this research new test protocols were developed to measure stiffness and thickness of the shell of air bubbles extracted from cement paste and to quantify stability of foams of AEAs in a cementitious environment. These tests could be used by researchers and practitioners who are interested in developing new admixtures and/or identifying admixtures with undesirable performance.

Book The Effect of Entrapped Air on Air void System Parameters in Hardened Concrete

Download or read book The Effect of Entrapped Air on Air void System Parameters in Hardened Concrete written by John T. Price and published by . This book was released on with total page 210 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Distribution of Voids in Field Concrete

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).

Book Comparison of Air Void Content Measurements in Fresh Versus Hardened Concretes

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.

Book Journal of the PCA Research and Development Laboratories

Download or read book Journal of the PCA Research and Development Laboratories written by Portland Cement Association. Research and Development Laboratories and published by . This book was released on 1964 with total page 472 pages. Available in PDF, EPUB and Kindle. Book excerpt: