Improving the Cement Based Reinforced Composites by Use of Partially Oxidized PP Fiber

Abstract

In improving fiber reinforced cement-based composites, it is critically important to enhance the bonding strength between fibers and cement hydrate. Polypropylene (PP) fiber is a property enhancing additive, commonly used in cement-based composites. In this study, we tried to modify the surface properties of PP to enhance its bonding with calcium silicate hydrate (C-S-H). The surface was at least partly converted from lyophilic to hydrophilic by partial oxidation using potassium dichromate. The change in surface properties was examined by FT-IR, AFM, SEM and contact angle. The appearance of peaks at 1635, 1650 and 3200 cm-1 in FTIR spectra for the treated PP, indicated the adsorption of water molecules on the surface, verifying the increase in hydrophilicity of PP. The AFM observation depicted that the roughness of partially oxidized PP surface was significantly increased. The contact angle was reduced due to the increase in hydrophilicity of the PP surface. However, the tensile strength of PP fiber had no significant reduction after being subjected to partial oxidation. Finally, AFM and SEM observations have shown that treated PP film bonded to C-S-H more tightly than that of original PP. It is suggested that partial oxidation of PP is an effective method to improve cement-based composites.