Before the capillary sorption measurements were made, the specimens were cured in limewater for periods of 1, 7 and 28 days at 20ºC. Two methods for drying the samples were used. In the first, the samples were dried in an oven at 50ºC until a constant mass was obtained, which took about 20 days. The second method was to air dry (also referred to as "bench dried") samples in a laboratory environment (at 20ºC and 30% RH) for four days and then in a desiccator containing a desiccant for three days. Figure 3 compares the sorption of water for the air dried and oven-dried mortar (Mix 1). Clearly the degree of saturation of the material plays a strong role in controlling the uptake of water. Over a period of about 100 days the oven-dried sample absorbed nearly three times as much water as the air-dried samples. Also fits of data to Equation 1 showed that the sorptivity of the oven-dried sample was three times greater than that of the air-dried sample. It is also possible that the oven drying process may have formed some cracks due to drying shrinkage resulting in greater sorption.
FIG. 3 The influence of specimen treatment before exposure to water is shown by the rate of absorption versus time.