Characterization of slab behavior and related material properties due to temperature and moisture effects

A concrete slab was constructed at the Riverside Campus of Texas A&M University to investigate environmental effects in terms of temperature and humidity on the behavior of jointed plain concrete pavements. The slab had daily periods of tensile and compressive strain corresponding to the daily changes in temperature and relative humidity of ambient air and slab. The trends in slab displacements and dowel behavior were clearly dependent upon the changes in ambient temperature and slab temperature gradients. Drying shrinkage, primarily in the vicinity of the top surface, appeared to cause an overall shift in both strain and vertical displacement of the slab over a two-year period after placement of the concrete.; Desirable curing methods should be used to control the temperature and relative humidity of the slab. The effective curing thickness concept was introduced as a method to evaluate the effectiveness of a curing method. The surface relative humidity had the biggest influence on both the effective curing thickness and the rate of evaporation. Penman's evaporation model was modified based on data collected in a series of laboratory experiments and it could be used as a boundary condition in the modeling of temperature and moisture of the slab.; A mathematical model was developed for the calculation of temperature and humidity distribution to help investigate the effect of different combinations of climatic factors, construction, and materials on the development of early-aged cracking and other distresses. This model is comprised of a nonlinear time-dependent partial differential equation and is solved by the finite element method. Using data collected from the test slab, thermal conductivity and moisture diffusivity were back-calculated to accurately represent temperature and moisture flow in hardening concrete pavement over time. Estimation of strength development of slab concrete using the predicted temperature and moisture is presented to show the feasibility of the applications of temperature and moisture prediction.