Effect of polymer fibers recycled from waste tires on properties of wet-sprayed concrete

This study explores the possibility of using recycled tire polymer fibers (RTPF) as a micro-reinforcement in wet-sprayed concrete mixes. Two groups of mixes were made: sprayed concrete mixes with and without an air-entraining admixture. Each group comprised mixes with 0.9 and 1.8 kg/m3 of RTPF. To facilitate comparison, the groups contained either a plain mix, without fibers, or a mix with polypropylene (PP) fibers, usually used to control early-age cracking. The mixes were tested for their transport properties, including capillary absorption and gas permeability, freeze-thaw resistance, and autogenous and restrained deformation. Results show the beneficial effect of RTPF during freeze-thaw cycles and the deformation resistance of wet-sprayed mixes. Observed differences in the transport properties between mixes with and without air entrainment are explained by changes in pore structure, tested using mercury intrusion porosimetry (MIP).