Evaluation of Consolidation Problems in Thicker Portland Cement Concrete Pavements
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2003-08-01
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TRIS Online Accession Number:00964862
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Edition:Final Report
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Abstract:The purpose of this study is to investigate methods of reducing the size and total volume of the entrapped air voids in concrete slabs that are over nine inches thick. Laboratory and field tests were designed to investigate the effect of variations m vibration frequency and aggregate gradation on entrapped air content, strength and performance factors such as smoothness, faulting, adhesion failures, and spalling. In 1993, a test section was constructed to compare the effects of increasing the proportion of coarse aggregate to fine aggregate and increasing vibration frequency. Annual surveys of joint sealant failures, spalling and joint faulting were performed from 1994 to 2001 on this test section. Samples from this project were cut, polished and analyzed to determine entrained and entrapped air content. In 1994, another test section was constructed to assess the effect of controlling the total gradation of concrete aggregate and increasing vibration frequency. A profilograph test was performed in 1996 to measure pavement smoothness on this project. Core samples were taken from both the wheel path and the wheel gap and nuclear density meters were used on both projects to measure the in-situ density of the pavements. The following conclusions are supported by this investigation: 1 . Increasing the proportion of coarse aggregate in the mix consistently reduced the amount of entrapped air in these pavements without significantly affecting other performance parameters. 2. Increasing the vibration frequency increased adhesion failures, spalling, faulting and entrapped air content of the standard 35% coarse-aggregate mix. Although increasing vibration frequency did improve the initial smoothness of the uniform-gradation mix, the markedly detrimental effects on the standard mix and the lack of significant performance improvements on the other mixes argues against further use of this technique on thicker portland cement concrete pavements without further study. 3. Relative density is not an accurate measure of percentage of entrapped air. 4. Using a more-uniformly-graded aggregate and a larger-sized coarse aggregate should result in better consolidation of thicker Portland Cement Concrete (PCC) pavements
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