Water movement in Internally Cured Concrete

Abstract

Currently, ordinary cement concrete uses external curing. For high-strength or high-performance concrete, implementing external curing is difficult and inefficient. In these types of concrete, the rather large cement content and low water-binder ratio form very dense cement paste. Thus, not only the autogenous shrinkage of concrete is increased, but the effectiveness of external curing is also reduced. To ensure the quality of the concrete, Internal Curing (IC) has been proposed. With IC, water is generally supplied via internal reservoirs such as saturated lightweight aggregates and superabsorbent polymers. The volume of internal water, which is not part of the volume of the mixing water, cures the concrete from the inside. This paper presents our results of theoretical research and calculations on water movement in internally cured concrete. The efficacy of internal curing depends on parameters such as the volume of internal curing water, the structure of the porous system in lightweight aggregates and cement matrix, curing temperatures. To demonstrate those factors' dependence on water displacement, we set up a theoretical function through a model that, based on the law of fluid flow and the system's law of capillary attraction, connects the capillary in lightweight aggregates with the capillary in the cement stone. From the empirical relationship of hydrated thermal of cement and porosity ratio in concrete, we make preliminary calculations of the water movement distance in internally cured and differently aged concrete. These analyses show the feasibility and effects of internal curing.