Effect of water to cement (W/C) ratio and age on mechanical behavior of tire-recycled steel fiber reinforced concrete

The annual entrance of billions of used tires into landfills has caused tremendous environmental concerns, while the recycled steel fibers from these tires can improve the mechanical characteristics of construction materials, including cement concrete. In this paper effect of the addition of recycled steel fibers on mechanical characteristics of ordinary cement concrete with different water to cement ratios are studied; to achieve that, compressive and flexural specimens are exanimated using standard test methods with four general mix designs. The range of recycled steel fibers is chosen as 0%, 1%, 2%, 3%, and 4% (per unit weight), and optimal fiber percentages based on water to cement ratios are also calculated. Results show that using recycled steel fibers positively affects all the mix designs, especially ductility, and postfracture energy absorption increases with the increase of fiber content. Fiber addition increases the compressive and flexural strength by about 25% and 58%, respectively. Depending on the water to cement ratio, the optimum percentage of recycled steel fiber for concretes with 0.6, 0.5, and 0.4 water to cement ratios are 3.0%, 2.3%, and 1.8% of unit weight, respectively.