Equilibrium of capillary and pore water pressure in lightweight aggregates concrete

Incorporating lightweight aggregate (LWA) in concrete decreases its density. The high porosity of LWA contributes to low density but also high absorption characteristics. LWA absorbs water even in a freshly mixed concrete mixture when their pore is not fully filled with water. On the contrary, an excessive saturation of LWA causes release of bleed water. Both situations make the concrete mixture unstable. Equilibrium in Laplace pressures between LWA and the surrounding cement binder determines the water absorption or desorption inside a fresh mix of lightweight aggregate concrete. A physical model derived from the pressure balance is proposed, and well predicts the water transport of LWA.