Portland cement concrete pavements over rubblized PCC

Abstract

This report has presented findings of research conducted to determine the viability of constructing Portland cement concrete pavements over rubblized PCC. Rubblization of aged PCC pavements is a common technique for in-place recycling of these pavements. For the vast majority of applications, the rubblized PCC layer is surfaced with hot mix asphalt (HMA). The use of Portland cement concrete as a surfacing material offers designers another option which may provide good performance and be cost-effective under certain conditions. The current concrete pavement design procedures utilized by the Wisconsin Department of Transportation (WisDOT) allow for the incorporation of a rubblized PCC base layer and an increase in the design value for the subgrade support k-value based on AASHTO guidelines. Over the practical range of rubblized concrete layer thicknesses investigated during this research, composite k-values were shown to increase by a factor of approximately 2 to 4 times, depending on the thickness of the rubblized layer and the quality of the natural subgrade support. This increase in composite k-value was shown to reduce the concrete layer thickness requirement between 0.25 to 1.45 inches, depending on subgrade quality and design ESAL loadings. The greatest reduction in required PCC thickness was seen for the combination of high subgrade support and low design ESAL loadings. As design ESAL levels increase, the allowable PCC thickness reduction decreases for all subgrade qualities. Based on the research results collected to date, there are no restrictions to the continued design and construction of Portland cement concrete pavements over rubblized PCC.