Fiber reinforcement of calcium silicate hydrate-based contact-hardening composites induced by compression

Calcium silicate hydrate in amorphous nature can be used to prepare water-resistant artificial blocks by direct compression at room temperature. These blocks have light weight and high strength, but their relatively high brittleness limited its utilization as construction materials. The purpose of this study is to improve the toughness of calcium silicate hydrate-based blocks by adding polypropylene fiber and emulsion in the powder before compressing. The effect of fiber and emulsion content on the density, strength and toughness of the hardened composite materials was explored. Microstructure of the fracture surface was evaluated through SEM. Result showed that the flexural strength of the hardened composite material increased significantly with the increase of the fiber content, while its compressive strength showed a downward trend. When the fiber content was 3%, the flexural strength and flexural toughness was 250% and 30.6% higher than those of the plain specimen, respectively. C-S-H powder particles adhering to the surface of the fiber increased the adhesion force between the fiber and C-S-H compact matrix, helping to improve the friction resistance when the fiber was pulled out, and thus the strength was increased. Adding 2% emulsion showed negative effect on the strength of the hardened composite, but could improve its toughness and machinability, acting as a wood-like material.