Performance of scrap tire steel fibers in OPC and alkali-activated mortars

In this study, the mechanical strength, total porosity and corrosion performance of ordinary Portland cement (OPC), class F fly ash (PFA) and metakaolin (MK) alkali-activated mortars (AAM) reinforced with 1 and 2% mass fraction of scrap tire steel fibers (SSF) were investigated. The accelerated corrosion test comprised of immersion of specimens in a 5% NaCl solution and specimen electrical resistivity measurements over a three-month period. Thereafter, surface and internal corrosion of SSF in these matrices were also characterized using image analyses. Compressive and the four-point flexural strength were assessed before (28-day cured specimens) and after accelerated corrosion testing. The results indicate that SSF may be employed as discrete fiber reinforcement for OPC and AAM mixtures, as the former improves deformation and toughness of the mortars even after the accelerated corrosion testing. Nonetheless AAM presented higher porosity and reduced electrical resistivity than OPC mortars, probably due to alkali leaching. While the surface and internal corrosion performance of the SSF-reinforced MK-based AAM was poor, PFA-based AAM presented internal corrosion comparable to that of the OPC mortar, as well as the lowest surface corrosion among the mortars studied.