Quantifying built-in construction gradients and early-age slab deformation caused by environmental loads in a jointed plain concrete pavement

Abstract

Construction curling and warping produces a built-in gradient, which takes place as the result of changes in temperature and moisture that occur prior to the hardening of Portland cement concrete (PCC) pavements. The slab remains flat in the presence of this gradient because the plastic concrete has not developed sufficient stiffness to generate stress or strain. The new Guide for the Design of New and Rehabilitated Pavement Structures has shown the importance of quantifying the built-in gradient. In this study, the magnitude of the built-in gradient was quantified along with the early-age response of the slab to environmental loads. It was found that the equivalent linear temperature gradient at the time of set was < 0.09°C/cm (0.55°F/in.). The largest built-in curvature measured along the diagonal for the restrained and unrestrained slabs was 0.0000124 1/m (0.0000408 1/ft) and 0.0000138 1/m (0.0000454 1/ft), respectively. The increase in curvature with an increase in equivalent linear temperature gradient for the unrestrained slabs was 7% higher than the restrained slabs. The profiles also indicated that the slab edges are, at times, completely unsupported.