The effect of controlled permeable formwork (CPF) liner on the surface quality of concretes

Surface quality of the concrete is important for the durability of reinforced concrete structures, because the cover stands at the forefront defending both mechanical damages and chemical deterioration. Controlled permeable formwork (CPF) liner is an innovative material used to improve the quality of the concrete in the cover region, by allowing the air bubbles and mix-water to drain out from the surface of concrete whilst retaining cement and other fine particles. The present experimental investigation was proposed to study the effect of CPF liner on the surface hardness and wear of concretes. Suitable size specimens were cast against CPF liner and (impermeable) steel formwork (IMF) and tested at various ages. The results revealed that the surface quality/hardness of CPF concretes enhanced by 14%-58%. Further, it was ascertained that due to CPF liner, 20 mm thick cover concrete was found to be harder than the core concrete. In conventionally cast concrete, 15 mm thick cover concrete was found to be softer than the core concrete. This change in the quality of cover concrete was found to be consistent over the w/c ratio of 0.31-0.48.