Effect of initial moisture of wet fly ash on the workability and compressive strength of mortar and concrete

This study aims to investigate the influence of initial moisture of wet fly ashes on properties of fresh and hardened mortar and concrete. In this study, wet fly ashes are used as a pozzolanic material in concrete with three levels of initial moisture content. The pre-existence of water in the wet fly ashes, equal to the initial moisture content, is considered as the first water in a double mixing method. Correspondingly, the effect of the initial moisture of wet fly ashes is evaluated by using the double mixing method. The studied properties in a fresh state include water requirement, flow of mortar, and slump of concrete. The strength activity index of mortar and compressive strength of hardened concrete are also studied in details. In order to clarify the effect of the initial moisture of wet fly ashes on the above-mentioned properties, microhardness is also examined to consolidate with the experimental results. Test results show that the properties of mortar and concrete are enhanced by using wet fly ashes, as compared to those using dry fly ash. Through microhardness observation, it is also revealed that the Vickers hardness values in the ITZ of the mixtures with wet fly ashes are higher than the values outside the ITZ. This effect is more obvious in the ITZ near the fine aggregate particles than in the ITZ near the coarse aggregate particles.