Assessment of the fracture properties of mortars reinforced with synthetic fibers

This paper investigates the post-cracking behavior of mortars reinforced with synthetic polypropylene fibers. To three series of mortars, normal strength (NSM), high strength (HSM), and high strength with fly ash (HSMFA), short and long, was introduced at 0.6% and 1% by volume, respectively. Pre-notched 4 x 4 x 16 cm were used for 3-point flexural tests, and the digital image correlation (DIC) method was employed to assess the load-CMOD curves. Based on the experimental curves, a tri-linear stress-crack opening (sigma-w) relationship was used to develop an analytical model for the Mode I crack propagation, and the inverse analysis method was applied to optimize the model's parameters. The obtained parameters were compared to the fib MC2010 characteristic values related to serviceability and ultimate limit states. The results show that short fiber-reinforced mortars exhibit a softening behavior regardless of the fiber dosage after a rapid drop once the tensile strength has been achieved. The three mortars incorporating long fiber reinforcement exhibit a very high deformation capacity and hardening behavior. For NSM, fibers appear to be more effective than HSM and HSMFA. All materials achieve the ultimate fracture opening of 2.5 mm, as defined by the fib MC2010, except 0.6% long fiber-reinforced HSMFA. Compared to the reference mixture (mixture without fibers), adding synthetic fibers to the mortar did not exhibit a significant environmental and health impact.