Drying Concrete: Experimental and Numerical Modeling

Drying of concrete is a major reason for concrete shrinkage, which significantly influences cracking and durability of concrete structures. Therefore a pilot test was executed in which progressive drying of concrete was measured at different depths under the concrete surface exposed to environmental conditions. Pore relative humidity distribution throughout a cross section (in depths from 3 to 10 cm) of concrete specimens was measured experimentally over the time range of 10 months. Then a moisture diffusion process is formulated mathematically and solved using recent models for moisture diffusivity and moisture capacity, and taking its nonlinearity into account. Numerical modeling is carried out using finite elements implemented into advanced numerical algorithm. Simplified analysis is also provided. Measured and calculated values are compared and moisture diffusivity is calibrated to the experimental results. Comparisons between measured and calculated values have pointed to the complexity of the drying process as well as the incapability of the used models to predict drying of concrete with the desired precision. This experiment is a pilot test of an experimental program and verifies the feasibility of humidity measurements.