Download or read book Clustering of Air Voids Around Aggregates in Air Entrained Concrete written by Andy Naranjo and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Factors Affecting the Origin of Air void Clustering written by Ronald L. Kozikowski and published by . This book was released on 2005 with total page 20 pages. Available in PDF, EPUB and Kindle. Book excerpt: Air-void clustering is a phenomenon in which entrained air-voids abnormally cluster around coarse aggregate particles. Numerous cases of low strength concrete have been attributed to this phenomenon and this study investigated the possible causes of the problem. There are many opinions as to why air void clustering occurs, but to our knowledge, no study has ever been conducted and published to determine the specific cause(s) of the phenomenon. Therefore, various parameters were obtained through a literature search and interviews with industry experts to evaluate their potential influence on air-void clustering. A visual petrographic rating system was developed to establish a standardized method for determining the severity of clustering. A correlation was found between this rating system and compressive strength loss and was used to evaluate which parameters had the most influence on air-void clustering. Problematic air-void clustering was found to coincide with late additions of water to the concrete mixture. The type of air-entraining admixture used in the concrete was found to have a major influence on clustering. It was noted that longer mixing times exacerbated the condition and that air-void clustering tended to occur in relatively finer air-void systems.
Download or read book Air Void Clustering in Concrete written by Jan Vosahlik and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Air void clustering around coarse aggregate in concrete has been identified as a potential source of low strengths in concrete mixes by several Departments of Transportation around the country. Research was carried out to (1) develop a quantitative measure of air void clustering around aggregates, (2) investigate whether air void clustering can be reproduced in a laboratory environment, (3) determine if air void clustering can blamed for lower compressive strengths in concrete mixes, (4) and identify potential factors that may cause clustering. Five types of coarse aggregate and five different air entraining agents were included in the laboratory study to see if aggregate type or chemical composition of air entraining agent directly relates to air void clustering. A total of 65 mixes were made, implementing the frequently used technique of retempering that has been previously associated with air void clustering around aggregates. Compressive strength specimens as well as samples for hardened void analysis were made. Compressive strength at 7 and 28 days was determined and the automated hardened void analysis (including a new method of clustering evaluation) was performed on all samples. It was found that it is possible to reproduce air void clustering in laboratory conditions. However, the results have shown that retempering does not always cause air void clustering. It was also observed that air void clustering is not responsible for a decrease in compressive strength of retempered concrete as neither aggregate type nor chemical composition of air entraining agent had a significant impact on severity of void clustering around coarse aggregate particles. It was also found that the total air content and an inhomogeneous microstructure and not air void clustering were responsible for lower strengths.
Download or read book Air Void Clustering written by Kyle Riding and published by . This book was released on 2015 with total page 205 pages. Available in PDF, EPUB and Kindle. Book excerpt: Air void clustering around coarse aggregate in concrete has been identified as a potential source of low strengths in concrete mixes by several Departments of Transportation around the country. Research was carried out to (1) develop a quantitative measure of air void clustering around aggregates; (2) investigate whether air void clustering can be reproduced in a laboratory environment; (3) determine if air void clustering contributes to lower compressive strengths in concrete mixes; and (4) identify potential factors that may cause clustering. Five types of coarse aggregate and five different air entraining agents were included in the laboratory study to determine if aggregate type or chemical composition of the air entraining agent directly relates to air void clustering. A total of 65 mixes were made, implementing the frequently used technique of retempering that has been previously associated with air void clustering around aggregates. Cylinders for compressive strength testing as well as samples for total air void analysis in the hardened concrete were made. Compressive strength at 7 and 28 days was determined, and automated testing for total air void analysis (including a new method of clustering evaluation) was performed on all mixes. This study found that it is possible to reproduce air void clustering in laboratory conditions. However, the results have shown that retempering does not always cause air void clustering. It was also observed that air void clustering is not responsible for a decrease in compressive strength of retempered concrete, as neither aggregate type nor chemical composition of the air entraining agent had a significant impact on severity of void clustering around coarse aggregate particles. It was found that the total air content and an inhomogeneous microstructure of the cement paste, not air void clustering, were responsible for lower strengths.
Download or read book Field Study of Air Content Stability in the Slipform Paving Process written by and published by . This book was released on 2012 with total page 230 pages. Available in PDF, EPUB and Kindle. Book excerpt: This study evaluated the impacts of construction on the air content and air-void system structure of Portland cement concrete pavements. The primary intent was to quantify the air content of fresh concrete before and after it has gone through the slipform paver. The air-void system parameters of hardened concrete were then assessed using cast and extracted core specimens. The results of the air content testing on fresh concrete and the concrete cylinder specimens cast in the field suggested that there is some loss of air as the concrete passes through the paver. Laboratory testing performed on cores extracted from the pavement did not provide any conclusive evidence that entrained air is lost during the slipform paving process. In fact, many of the extracted cores had measured air content values that were much higher than the specification requirement. If excessive, this could result in increased permeability and low-strength related issues. Although a rigorous statistical analysis was not performed, the results suggest that the air content testing on fresh concrete is not capturing the true air content of the concrete placed with a slipform paver. The fresh concrete air content is generally lower than the air content measured in the cores.
Download or read book Evaluating Air entraining Admixtures for Highway Concrete written by Mohamad Nagi and published by Transportation Research Board. This book was released on 2007 with total page 60 pages. Available in PDF, EPUB and Kindle. Book excerpt: "This report presents a recommended procedure for evaluating air-entraining admixtures used in highway concrete. The procedure involves the testing of non-air-entrained concrete and concrete containing the air-entraining admixture under simulated field conditions. Criteria are proposed for acceptance of admixtures for use in either highway pavements or structures. The recommended procedure and acceptance criteria will guide materials engineers in evaluating and selecting air-entraining admixtures that should contribute to appropriate freeze-thaw durability and thus to good performance and long service life. The content of the report will be of immediate interest to materials engineers, researchers, and others concerned with the design of concrete mixtures for use in highway pavements and structures."--taken from Foreword, page [v].
Download or read book Theory of Air Entrainment written by Abdul Hameed Khan and published by . This book was released on 1949 with total page 156 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Air Voids in Concrete and Characteristics of Aggregates written by National Research Council (U.S.). Highway Research Board and published by . This book was released on 1958 with total page 56 pages. Available in PDF, EPUB and Kindle. Book excerpt: Paper 1: A study of carbonate rocks used for concrete aggregate was conducted for the Iowa State Highway Commission to determine the factors in the aggregate causing distress in concrete and to establish criteria for recognizing potentially poor aggregates. Paper 2: The theory of the action of entrained air in producing frost-resistant concrete demonstrates the importance of the size and distribution of the air voids in the Portland cement paste. Paper 3: A summary of the results of the chemical study of carbonate rocks from several quarries in Northeast Iowa which produced carbonate aggregate for highway pavement concrete is presented.
Download or read book Identifying Incompatible Combinations of Concrete Materials written by Peter C. Taylor and published by . This book was released on 2006 with total page 168 pages. Available in PDF, EPUB and Kindle. Book excerpt: Unexpected interactions between otherwise acceptable ingredients in portland cement concrete are becoming increasingly common as cementitious systems become more and more complex and demands on the systems are more rigorous. Such incompatibilities are exhibited as early stiffening or excessive retardation, potential for uncontrolled early-age cracking, and unstable or unacceptable air-void systems. A number of test methods have been reviewed to assess their usefulness in detecting incompatibility early to help prevent problems with pavements in the field. A protocol has been developed to allow product manufacturers, concrete producers, contractors, and owners to monitor their materials and concrete systems. The protocol is phased to allow relatively simple field ttests to provide early warnings of potential problems and tthen central laboratory tests to support and confirm the field work. This is the first of two volumes. The other volume in the series is: FHWA HRT-06-080, Identifying incompatible combinations of concrete materials, volume II--Test protocol.
Download or read book Investigation of Low Compressive Strengths of Concrete in Paving Precast and Structural Concrete Study written by and published by . This book was released on 2000 with total page 94 pages. Available in PDF, EPUB and Kindle. Book excerpt: This research examines the causes for a high incidence of catastrophically low compressive strengths, primarily on structural concrete, during the 1997 construction season. The source for the low strengths was poor aggregate/paste bond associated with air void clusters and poorly formed cement paste in the interfacial region adjacent to the aggregate. An interaction between the 3synthetic4 air entraining admixtures, used as substitutes for vinsol resin, and low alkali cements was directly tied the problem with high summertime temperatures also contributing to the problem. The 3synthetics4 appear to be more hydrophobic, form thinner-walled air bubbles and develop rapid draining bubble flocculations more readily than vinsol resin, all of which can lead to significant reductions in strength. As an interim measure, the Department specified the sole use of vinsol resin air entraining agents along with water reducers, as needed, in April, 1998 and these measures have minimized the incidence of low strengths. Petrographic analysis of cores taken from low strength concretes failed to reveal the causes of the low strength problem but SEM microscopy clearly showed the failure mechanism. Laboratory testing of concrete mixes with various air entraining admixtures demonstrated an interaction was taking place with one cement and petrographic and chemical analysis of the cements used in the testing implicated alkali sulfates as a potential source of the interaction. Testing of the 3synthetic4 air entraining admixtures showed they have substantially different properties compared to vinsol resins. Mixtures of the 3synthetics4 and vinsol resin with 50 % or more vinsol resin behaved similarly to vinsol alone.
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:
Download or read book Concrete Petrography written by Alan B. Poole and published by CRC Press. This book was released on 2016-12-19 with total page 793 pages. Available in PDF, EPUB and Kindle. Book excerpt: This classic reference has established the value of petrography as a powerful method for the investigation of concrete as a material. It provides an authoritative and well-illustrated review of concrete composition and textures, including the causes of defects, deterioration, and failure that can be identified using a petrological microscope. This new edition is entirely revised and updated and also greatly extended to take account of new scientific developments and significant improvements in instrumentation and to reflect current laboratory working practices, as well as to reflect new understanding of the performance of concrete and related materials. Now in full color throughout, Concrete Petrography, Second Edition provides case study examples, with appropriate explanatory discussions and practical advice on selecting, handling and preparing specimens. It assists and guides the engineer, the trainee and the experienced petrographer in understanding the scientific evidence that is basic to petrographic analysis and so will lead to more accurate and timely diagnosis and treatment of problems in structural concrete. This book includes: Contributions in specialist areas by internationally recognized experts Explanation of computer techniques as an aid to petrography Full coverage of inspection, sampling, and specimen preparation New sections covering recent technological development of equipment Guidance on observation of cement and concrete mineralogy and microfabrics Discussion and illustrative examples of deterioration and failure mechanisms New work and guidance on the determination of water/cement ratio New color illustrations and micrographs throughout Thorough updating of standards, other authoritative publications, and references A fully revised, extended, and updated glossary of optical and other properties
Download or read book Recycling of Portland Cement Concrete Airport Pavements written by M. C. Hironaka and published by . This book was released on 1987 with total page 116 pages. Available in PDF, EPUB and Kindle. Book excerpt: The objective of this study was to develop criteria and guidelines for recycling portland cement concrete (PCC) airport aprons. Included in this study are all aspects of the recycling process including breakup and removal, steel reinforcement removal, crushing, screening, stockpiling, mix design, testing, placing, finishing, and performance. Recycling of PCC requires some specialized equipment such as pavement breakers and electromagnets for steel removal; however, all of the other equipment and procedures are those commonly used in the construction industry. Based on the regression experimental design procedure and laboratory tests conducted on pavement samples from six airports of widely varying age and conditions, it has been conclusively shown that aged PCC pavements can be recycled into new surface courses that meet strength requirements and have the same cyclic load carrying (fatigue) characteristics as those constructed with virgin sand content - 42 percent.
Download or read book Air entraining Admixtures written by Paul Klieger and published by . This book was released on 1966 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Study of the Effect of Blended Coarse Aggregate on Air entrained Concrete written by Kentucky. Department of Highways and published by . This book was released on 1949 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book ACI Materials Journal written by and published by . This book was released on 2008 with total page 242 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Study of the Effect of Blended Coarse Aggregate on Air Entrained Concrete written by Kentucky. Department of Highways. Research Division and published by . This book was released on 1947 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt:
