Preparation and properties of sisal fiber reinforced magnesium phosphate cement

Magnesium phosphate cement (MPC) with rapid setting or hardening, excellent binding ability, and low pH is considered as a potential matrix for a composite reinforced with natural fibers. Sisal fiber with high strength and elastic modulus is suitable for preparing a high-performance composite along with MPC. Plates made of MPC containing 10 % fly ash and sisal fiber were prepared by casting for short fiber and pressing for long fiber. The effects of fiber content on the mechanical properties of the plate at different ages were investigated. Flexural strength and volume deformation of plates after undergoing a wetting-drying cycle and high temperature were measured, and the sisal fiber-MPC interface was examined with optical microscopy and scanning electron microscopy. The results show that the interfacial bonding strength of sisal fiber and the MPC matrix reached 6 MPa at 1 day, resulting in flexural strength of more than 30 MPa and about 80 MPa for the plate with 30 % long sisal fiber at 1 h and 3 days, respectively. The reinforcement effect of short sisal fiber was much less than that of long sisal fiber at the same content. The composites also had excellent durability in water resistance and heat resistance. The flexural strength remained stable at ambient conditions for 510 days and retained around 52 MPa and 30 MPa after 50 wet-dry cycles and 200 °C for 1 h, respectively.