Effect of controlled permeable formwork on the improvement of concrete performances

In order to investigate the influence of controlled permeable formworks (CPF) on concrete, samples were made in steel modulus with and without CPF. Visible surface morphology, adsorption of water and chloride, permeability of Cl-, together with pore structure of the surface layers were studied and analyzed. It's indicated that, by the application of CPF, concrete could be enhanced and the surface is homogeneous without any visible blow-holes. Also, adsorption and permeability of water and chloride ion into concrete were inhibited. According to mercury intrusion porosimeter, the porosity in the thickness of 0-3 mm under surface was reduced from 10.48% of the control sample to 7.04%. The largest decrease existed in pores with diameter of larger than 0.2 μm. The study indicates that CPF could markedly improve the appearance as well as the durability of concrete structures.