Mechanical Properties of Modified Metakaolin-Based Geopolymer Concrete Containing Tires Rubber Waste and Reinforced with Recycled Steel Fibers

Abstract

Geopolymer concrete has superior physical properties and a positive environmental impact compared to conventional concrete. Waste management is one of the most essential issues. Regarding sustainable raw material management, recycling the industrial waste as much as possible and developing new technologies that reduce industrial waste landfills and generate materials with new added value is essential. Every year, people throw away about 17 million tons of tires that cannot be used again. This trash is a significant environmental threat, so recovering tires is essential. The results showed that replacing 10% of the crumbed rubber wastes with natural coarse aggregate decreased the workability, compressive strength, splitting tensile strength, flexural strength, and direct tensile strength by 5.5%, 38.6%, 10.6%, 6.25%, and 6.67%, respectively with respect to a reference without wastes. At the same time, adding 0.125% and 0.25% recycled steel fibers increased the workability reduction by 2.9% and 5.9% and improved mechanical properties, including compressive strength, splitting tensile strength, direct tensile strength, and flexural strength by 43.3%, 15.9%, 26.4%, 14.2%, 90.4%, 42.4%, 32.1%, and 17.9%, respectively, compared to a reference mixture containing 10% crumbed rubber wastes. The results also showed an increase in the total energy by 23.2%, 142.4%, and 312.1% when replacing 10% of the natural coarse aggregate with crumbed rubber wastes, including 0.125 and 0.25% recycled steel fibers, respectively. When these wastes were introduced together or individually, Brittleness of geopolymer concrete changed to ductile.