Temperature and RH of normal concrete and mortar subjected to drying in an indoor residential environment

The evolution of internal temperature and relative humidity (RH) distributions in initially saturated normal concrete and mortar cubes with water/cement (w/c) ratios of 0.4, 0.5 and 0.6 stored in an indoor residential environment were recorded for over a year. Measurements at regular intervals were taken at six different depths from the exposed drying surface of each specimen. It was found that the internal temperature at all depths in the mortar and concrete samples followed the variations of ambient temperature closely, irrespective of the w/c ratio. While the effect of the w/c ratio on the mean internal RH in mortar was statistically negligible, it became discernible in concrete at points where the material had relatively lower saturation levels and when the effect of evaporation was low due to a low ambient temperature. A higher dosage of polycarboxylic ether based superplasticiser was found to delay the drop in internal RH. The recorded values of internal RH over the period of study were found to be conducive for the onset and propagation of carbonation-induced corrosion. A two-parameter linear model for the prediction of critical drying time with respect to spatial distance from the drying surface was developed.