Moisture warping in slabs on grade

Curling and warping are slab deformations that cause deviations from its original surface as a result of differences in temperature and moisture, respectively, between slab top and bottom. The upward curled/warped slab condition can change the failure mode from bottom-up to top-down mid-slab cracking. This study is a first step in investigating shrinkage-related slab warping with the presence of drying shrinkage at the top surface combined with wetting at the bottom surface. A laboratory study is currently carried out on concrete beams. The results show that substantial warping develops if slab bottom is in continuous contact with water. Finite Element (FE) analysis suggests that warping is the dominant factor in slab uplift. Internal curing using lightweight fine aggregate (LWFA) is found to be effective in reducing moisture warping.