Reducing water absorption of fiber-cement composites for exterior applications by crystal modification method

Abstract

The aim of this work was to reduce the water absorption of the fiber-cement composites, which is also known as fiber-cement products, by the crystal modification of cement matrix using the additives including polyurethane-based corn starch–lithium perchlorate (LiClO4), and acrylic resin emulsion-based chitosan-silicate hybrid compound. To prepare the samples, the mixtures consisting Portland cement Type I, sand, cellulose fibers from pine trees, gypsum, and additive were mixed with water. The percentages of additive in the mixtures before mixing with water were 0.03 to 0.17 wt%. The green sheets of samples were formed by filter-pressing method, air cured for 1 day, and then autoclaved at 8 bars and 140°C for 12 h. The experimental results indicated that the water absorption of the samples was reduced when polyurethane-based corn starch–lithium perchlorate (LiClO4) was used as the additive due to the crystallization of the small crystals within cement matrix, while their mechanical properties including modulus of rupture (MOR) and modulus of elasticity (MOE) of the samples using this additive conform industrial standard.