Estimation of Evolution of Relative Humidity Distribution for Concrete Slabs

Realistic prediction of concrete shrinkage and creep requires the calculation of the distributions of relative humidity at various times. Although the distributions of the relative humidity can be computed by numerical methods from the differential equation for diffusion, simple prediction formulas can facilitate structural analysis. The purpose of this paper is to present a simple formula for slabs and walls, which agrees with the shrinkage prediction formula and with the measurements of pore relative humidity. The drying process may be considered as one-dimensional in space for walls and slabs. A simple explicit formula with three parameters is formulated. In a more simplified version, a single parameter formula is developed. The parameter can be estimated from the existing empirical relations for shrinkage time parameter.