However, concrete at the center of thick concrete components or structures can never dry because water transport in saturated or unsaturated conditions is always limited by diffusion in the concrete pores (water present under the liquid form, or under the vapor state). The water diffusion time is thus proportional to the square of its transport distance. As a consequence, the water saturation degree inside thick concrete structures often remains higher than 80%, a level sufficient to provide enough water to the system and to maintain the alkali-silica reaction on going.