Characterizing Effective Built-In Curling from Concrete Pavement Field Measurements

Instrumented concrete slabs were constructed in Palmdale, Calif., in order to fail the slab sections under accelerated pavement testing. Prior to fatigue failure testing, these slabs were monitored over $24\mathrm{h}$ cycles without load, and under a slow-moving $40\mathrm{kN}$ rolling wheel load. Slab temperature profiles, edge and corner deflections, and interior vertical deflections were collected at $2\mathrm{h}$ intervals. A finite element program was used to analyze the deflection data and calculate an effective built-in temperature difference (EBITD) through the slab, which represented the combined effects of nonlinear “built-in” temperature gradients, irreversible shrinkage, and creep. Differences in restraints (from adjacent slabs, shoulder, and base friction) and variability in material and structural properties resulted in wide variation in the measured EBITD. High EBITD values $(-20\text{to}-35°\mathrm{C})$ were observed for sections with low restraint, and low to moderate EBITD values $(0\text{to}-20°\mathrm{C})$ observed for sections with higher restraint.