Strengthening and toughening mechanisms in microfiber reinforced cementitious composites

Materials with quasi-brittle stress strain curves exhibit desirable properties such as enhanced durability, flaw tolerance and toughness. This study reveals that steel microfiber reinforced cement based composites exhibit such quasi-brittle behavior. Mechanical properties of steel microfiber reinforced cement based composites are obtained through flexure and splitting tension tests. The cracking process and crack fiber interactions that lead to the quasi-brittle behavior in these composites were investigated. The strength and toughness enhancement is associated with crack wake mechanisms. Aggregate bridging and pullout and secondary crack formations associated with microfiber bridging sites are predominant during the strain hardening regime. Multiple secondary microcracks perpendicular to the fiber/matrix interface is the dominant failure mode beyond peak load in the strain softening regime.