The effect of controlled permeable formwork liner on the mechanical properties of concrete

Controlled permeable formwork (CPF) liner was developed primarily to improve the surface quality of concrete and thereby its durability. CPF liner allows air and water to escape from the surface adjacent to the formwork. This paper reports an experimental study carried out to investigate the influence of CPF liner on the strength and certain mechanical properties of concrete with three different water–cement (w–c) ratios. The specimens were prepared against CPF liner and impermeable steel formwork (IMF) and tested at various ages starting from 7 to 365 days. Various tests were conducted to assess surface quality; compressive, split tensile and flexural strengths, rebound hammer and abrasion resistance of concrete. The results indicate that CPF concrete performed better than IMF concrete in all aspects. The present investigation reveals that the use of CPF liner has significantly improved the tensile strength (say, 20 %) of concrete and the abrasion resistance has been enhanced to a remarkable level (50–80 %). Further, the surface quality is very essential to assess the cube strength of concrete and the existing testing method slightly underestimates the cube strength.