Drying shrinkage of mortar manufactured with recycled fine aggregate at vary initial saturation degree

In this study, the influence of saturation degree of recycled fine aggregates (RFA) on the drying shrinkage of mortar was investigated. The initial saturation degrees of RFA were controlled at 0%, 25%, 50%, 75% and 100% prior to use. The influence of total amount of water was investigated by two mix proportions. In the first series (T), the total water including the mixing water and additional water was kept constant for all of the mixtures. In the other series (F), only the mixing water was added at an equal amount. Meanwhile, the effective W/C((W/C)(e)(ff)) of the mixes was determined to estimate the continue absorption of RFA. In addition, the change of some parameters in capillary tension theory was detected to explain the influence of RFA on the shrinkage. Based on the analysis of results, RFA could continue absorb water rapidly in the first 1 h, and the total absorbed water content increases with the increasing of the initial saturation degree, as well as the increasing of (W/C)(eff) for fresh paste. The phenomenon is significant in the F series, which leading to the obvious decrease of the drying shrinkage. It is also affected by the more water loss of RFA with higher saturation degree. In the T series, there was a little discrepancy for the properties among the mixtures. The drying shrinkage of mortar with RFA varied with the (W/C)(eff), as well as the elastic modulus, hydration degree and mass loss of mortar. (C) 2020 Elsevier Ltd. All rights reserved.