Surface modification and dispersity of chopped carbon fiber and its effects on mechanical properties of gypsum-based composite materials

Gypsum-based composites are recognized as environmentally friendly and efficient materials suitable for modern construction. The mechanical properties of gypsum-based composites are crucial for determining their suitability for various applications. In this study, chopped carbon fibers (CCFs) were used to improve the compressive strength of gypsum materials. Hydrogen peroxide (H2O2) and sodium hypochlorite (NaClO) were used to oxidize the surface of CCFs to improve their dispersity in gypsum-based composites. The oxidized CCFs were dispersed using polycarboxylate ether superplasticizer (PCE), hydroxypropyl methyl cellulose ether (HPMC) dispersant and ultrasonic treatment, and the compressive strength of CCF-reinforced gypsum-based composites (CGC) was studied systematically. The surface roughness of oxidized CCFs increased with the content of hydrophilic oxygen-containing functional groups, such as hydroxyl (C-OH) and carbonyl (C=O) groups. The compressive strength of CGC was significantly improved by adding dispersed CCFs. The addition of 2.0 wt% of 3 mm CCFs and 1.0 wt% of 6 mm CCFs, dispersed using PCE, resulted in compressive strength enhancements of 50.9% and 72.4% of hardened gypsum, respectively. This improvement was attributed to the synergistic effect of PCE adsorption on the CCF surface and the steric hindrance between PCE and gypsum particles, promoting efficient dispersion of CCFs within the gypsum paste.