IMPROVEMENT OF CONCRETE OVERLAY DESIGN PROCEDURES

Date

2019-08-07

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Abstract

The primary objective of this research was to improve the current concrete overlay design procedures. As of 2016, TxDOT manages a total of 16,327 lane miles of Portland cement concrete (PCC) pavement, which represents an important asset to TxDOT. As PCC pavements in Texas built in the 1960s through 1980s have already exceeded or are approaching the end of their design lives, many of these projects will require rehabilitations of some form. Considering the expected steady increase in truck traffic in the future, PCC overlays represent one of the best options for the rehabilitation. Currently, guidelines on PCC pavement overlays on PCC pavement focus on overlay slab thickness determination, but do not provide clear directions on whether existing PCC pavement is a good candidate for concrete overlay, or if the pavement is a good candidate, which overlay type – bonded concrete overlay (BCO) or unbonded concrete overlay (UBCO) – is appropriate. Sound guidelines are needed for the selection of an optimum overlay type, especially for continuously reinforced concrete pavement (CRCP) overlays, which could extend the pavement lives of structurally deficient PCC pavements in Texas at a reasonable cost. Four primary tasks conducted in this study were (1) the evaluations of PCC overlay performance of various BCO and UBCO projects built in Texas, (2) the development of BCO design procedures based on mechanistic-empirical principles, (3) the development of design guidelines for the selection of an optimum overlay type, and (4) improvement of current UBCO design procedures based on the theoretical analysis and findings from the field testing. The structural behavior and performance of PCC overlays were investigated by deflection testing, bond strength testing as well as material property evaluations. Three-dimensional finite element analyses were conducted to investigate structural responses of various PCC overlay systems under wheel and environmental loadings. Based on the analysis results and field performance of PCC overlays, a BCO design program was developed. For the UBCO system, detailed analyses were conducted to evaluate the soundness of the AASHTO 93 design procedures. Ultimately, the information obtained in this study could be useful in improving concrete overlay design procedure and construction practices.


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Keywords

Concrete overlay, design

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