The
amount of free water increases with increasing w/c. In addition,
at early age, the amount of free water is high compared with that
in lower porosity fully hydrated concrete. Such capillary pores are
typically interconnected with the surface. Thus, when high porosity
concrete is coated at early-age, water molecules may entrap
between the bitumen coating layer and the substrate, leading to
emulsification of the bitumen and its separation.