Influence of fiber type on the tensile behavior of high-strength strain-hardening cement-based composites (SHCC) at elevated temperatures

The influence of fiber type on the mechanical behavior of high-strength strain-hardening cement-based composites (HS-SHCC) during and after exposure to elevated temperatures of up to 200 °C was investigated. The fibers under investigation were made of ultra-high molecular-weight polyethylene (UHMWPE), para-aramid-copolymer (Aramid) and as as-spun and high-modulus poly(p-phenylen-2,6-benzobisoxazol), i.e., PBO-AS and PBO-HM. Based on the considerably higher thermal stability of Aramid and PBO fibers in comparison to UHMWPE, the effect of elevated temperatures on the tensile behavior of SHCC made with Aramid and PBO was expected to be less pronounced. Nevertheless, the SHCC made with UHMWPE fiber yielded a significantly superior multiple cracking and pre-peak ductility up to 150 °C both during and after thermal exposure. At 105 °C, the SHCC reinforced with UHMWPE fiber yielded only a small reduction in tensile strength and a considerable increase in strain capacity. The composites made with Aramid and PBO fibers yielded a pronounced degradation in tensile strength and strain capacity already at 105 °C and a considerably weaker recovery of ductility when cooled down to the room temperature. At 200 °C all composites except those containing Aramid fiber exhibited no multiple cracking and brittle failure with dramatically reduced tensile strength.