Early-age concrete temperature and moisture relative to curing effectiveness and projected effects on selected aspects of slab behavior

Concrete curing has long been realized to be important to produce durable concrete. Curing compound is widely used to cure concrete in the field. The current curing membrane evaluation method ASTM C 156, however, is incapable of distinguishing the curing compound quality and guiding the curing practice in the field. A new laboratory curing membrane evaluation protocol is developed in this study. It has the ability to rank the quality of curing compound and guide curing practice in the field according to the field ambient weather conditions and the type of curing compound. A series of field tests were conducted to investigate the key factors that affect the curing effectiveness in the field conditions. A finite element program, temperature and moisture analysis for curing concrete (TMAC2), is updated to solve the coupled and nonlinear heat transfer and moisture transport problems in early-age concrete. Moisture capacity is induced into the TMAC2, which makes it unique to characterize the self-desiccation. A full scale concrete pavement test study was conducted at the FAA National Airport Pavement Test Facility (NAPTF) near Atlantic City, New Jersey. In this study, the material properties, i.e. thermal conductivity and moisture diffusivity, were backcalculated from field data. Thereafter, backcalculated material properties were used to forward-calculate the temperature and moisture histories of all other sections. High order shear deformable theory is used to model the concrete slab curling and warping behavior because of highly nonlinear temperature and moisture gradients. The maximum shear strain is obtained a couple of inches below the concrete slab. This might account for the occurrence of delamination.