United States Department of Transportation
i
Optimizing Reinforcing Steel in 12-In and 13-In Continuously Reinforced Concrete Pavement (CRCP)
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2023-08-01
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[PDF-29.44 MB]
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Edition:September 2019–August 2022
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Abstract:The performance of continuously reinforced concrete pavement (CRCP) in Texas has been excellent. However, truck traffic in Texas has been increasing, which required thicker slabs. Since TxDOT placed steel at the mid-depth of the slab, the use of thicker slabs increased the distance between top of the slab and longitudinal steel. This increase resulted in larger crack spacing and occasional horizontal cracking. Continued wheel loading applications degrade the top half of the concrete and partial depth distress. Traditionally, punchout has been reported as a major and only structural distress in CRCP. However, it has been observed that different types of cracking and resulting distresses have taken place in CRCP that has had improved design features such as thicker slabs, stabilized bases, and tied concrete shoulders. These cracks, which cannot be explained by traditional theories related to punchout and spalling, are normally associated with horizontal cracking at approximately mid-depth of the slab. This horizontal cracking has been observed in CRCP with thicker slabs, thickness of 12 inches or larger. It was also observed that horizontal cracks occurred at early ages before the pavement was open to traffic. These findings strongly indicate that horizontal cracks are not due to structural deficiencies of CRCP. Rather, concrete material properties, environmental conditions during and right after concrete placement, and most importantly longitudinal steel placement layouts must play a significant role in the development of horizontal cracking. The primary objective of this study is to identify the mechanisms and associated variables of horizontal cracking in CRCP and to develop mitigation methodologies. To this end, theoretical analyses of early-age CRCP behavior were conducted using 3-dimensional CRCP modeling, and field testing was conducted at 4 different CRCP construction projects. The behavior of CRCP at early ages under environmental loading (temperature and moisture variations) obtained from the field testing was compared with numerical analysis results and the model was calibrated. The effect of each variable related to design, material, and construction on the horizontal cracking potential was evaluated through comprehensive numerical analysis with a calibrated model. One of the major findings is that steel depth has significant effects on CRCP behavior and a modest decrease in the distance between slab surface and steel depth reduces horizontal cracking potential substantially. It is expected that the implementation of the findings from this study is expected to improve CRCP performance substantially for thicker CRCP.
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