Zero-stress temperature and Its implications for long-term performance of continuously reinforced concrete pavements
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Continuously reinforced concrete pavement (CRCP) is a portland cement concrete (PCC) pavement structure with a continuous longitudinal steel layout. CRCP is forming a major portion of PCC roadway systems in the state of Texas due to its low life cycle cost, ease of maintenance, and durable nature. While the overall performance of CRCP is proven to be excellent, some performance problems are still found as a form of distresses such as punchout and spalling. The current pavement design guide states that these distresses are closely related with the early-age behavior characteristics of CRCP, and various measures are underway to develop to improve the long-term performance of CRCP in terms of initial material design and use, structural design, and quality control. Understanding the current issues that pavement engineers and researchers face, the primary objective of this dissertation research focuses on sound understanding of the early-age structural behavior characteristics of CRCP and its effect on the long-term performance to provide reliable design and analysis criteria for CRCP. To achieve this main objective, characterizing the early-age structural response in CRCP was a core task of this study. For this purpose, a zero-stress temperature (ZST), one of the design and construction variables considered to have most significant effects on CRCP behavior and performance, was evaluated. As a beginning point of the entire framework, a series of field experiments were conducted in four new PCC pavement construction projects in the state of Texas to evaluate the actual structural response in early-age CRCP since a laboratory experiment would have a critical limitation in simulating the restraint conditions that exist in actual CRCP. To expand this core task to various parametric categories, a computer-aided parametric simulation was performed using valid numerical models. Based on data sets obtained from the parametric investigation, a statistical model to quantify the early-age structural response of CRCP was proposed to implement in codes of practice and pavement design guides. A secondary task was to identify a correlation between the early-age structural response and the long-term performance of CRCP structures. Since the experimental and analytical investigations tended to provide quite localized information for the time-dependent behavior of CRCP, the overall performance of CRCP could not be properly identified solely based on those results. To overcome this limitation, extensive field condition surveys were performed in seven different old CRCP sections with known material and early-age temperature history to find the implications of early-age behavior characteristics on the long-term performance of CRCP from a macroscopic point of view. It is expected that this research effort will provide pavement engineers and researchers with useful information to understand the actual time-dependent behavior of CRCP and a solid foundation to improve the sustainability of CRCP structures.