Value-added reuse of scrap tire polymeric fibers in cement-based structural applications

Abstract

Presently, scrap tire polymeric fibers (STF) have limited reuse value in most countries of the world, hence it is largely land filled or used as an eco-unfriendly tire derived fuel (TDF). Unfortunately, toxic gases and acids could be released from these aforementioned STF management strategies. Therefore, in this study, an alternative reuse approach for the STF was explored; the possibility that it could enhance the flexural post-crack residual strength and wear resistance of cement composites were examined. Furthermore, the likelihood of improving the aforementioned properties through the hybridization of the STF with commercial macro fibers such as steel hook-end (HE) and polypropylene (PP) fibers was also evaluated. The cement composites investigated consist of a set of 0.50 water-to-cement (w/c) ratio mortar and two sets of concrete batches corresponding to 0.50 and 0.40 w/c ratios. Results indicate that the post-crack residual strengths of mortar and concrete mixtures singly reinforced with the STF was about 0.10 MPa and 0.10 – 0.20 MPa, respectively. Hence, these STF reinforced cement composites have no useful structural application value. However, with the hybridization of 0.35% STF with 0.2 – 0.5% macro fibers, mortar mixtures with post-crack residual strengths ranging from 1.4 to 3.1 MPa were attained as a result of the positive synergy between the STF and the HE fibers. Hybrid 0.35% STF and 0.35% HE fiber reinforcement of concrete also led to a positive synergy and improvement in post-crack residual strength capacity, especially for the 0.50 w/c ratio mixture. Relative to the plain concrete, 0.35% STF or hybrid combination of 0.35% STF and 0.35% PP had no impact on concrete abrasion resistance. Conversely, cumulative volume loss of concrete reinforced with hybrid 0.35% STF and 0.35% HE fibers decreased by approximately 8.9% and 16.1% for 0.50 and 0.40 w/c ratio concrete mixtures, respectively. All-in-all, these results suggest that in lieu of its present use as a TDF, the STF hybridized with HE fibers could actually be used as a sustainable, discrete fiber reinforcement for cement-based repair applications where slightly enhanced flexural post-crack performance and resistance to abrasive wear are desired.