Role of sample conditioning in water absorption tests

Minimizing fluid transport properties of concrete is very important for providing prolonged durability of concrete structures. Sorptivity testing is an easy and effective method for evaluation of near-surface transport properties of concrete. In the sorptivity test, the moisture content of the tested sample has a dominating effect on the rate of absorption. Thus, the drying procedure during sample preparation is an important part of sorptivity testing. In the literature, many different procedures for sample preparation can be found, ranging from long room temperature drying to oven drying at 105 °C for 24 h. In this research, the effect of two drying procedures was compared: a milder one (ASTM C1585), and a more rigorous drying (DIN 52617). The comparison was performed on mortars with water to cement ratios of 0.35, 0.40, 0.45, and 0.50, as well as mortars at the water to binder ratio of 0.40 with different levels of cement replacement by fly ash and slag. The initial sorptivity obtained after these drying procedures was compared to chloride migration coefficient and conductivity test results, while the secondary sorptivity was compared with the total porosity. The latter procedure was found to give better correlations with other transport properties of mortars.