Experimental Study on Mechanical Properties of Concrete with Recycled Materials as Fine Aggregates

Abstract

Using recycled materials as eco-friendly construction materials has been a growing trend in recent decades. In particular, obtaining discarded polymeric and asphaltic materials recovered from waste and reprocessing them into new products has decreased the demand for mining raw minerals, thereby minimizing negative environmental impacts. This study focuses on two materials that, when discarded, occupy large amounts of landfill space and contribute to biohazards in landfills: tires and shingles. This study was performed to show the effects on the strength and density properties of Portland cement concrete when these two recycled materials are used to partially replace the sand content as the fine aggregate. The two recycled materials used in this study are processed crumb rubber from discarded tires and crushed fiberglass-based asphalt shingles, commonly referred to as recycled asphalt shingles (RAS) from replaced roofs. The experimentation was performed by incorporating three gradations of crumb rubber and one gradation of RAS at various percentages into concrete mixes and performing compression tests and single-point flexure tests. The descriptive results of this study show that RAS replacement performed substantially better than crumb rubber replacement. Results further show that the addition of high percentages of crumb rubber or RAS to concrete becomes detrimental to the axial compressive strength and to the flexural tensile strength of the specimens, particularly at levels higher than 4% crumb rubber replacement and 25% RAS replacement. A statistical analysis of the axial compressive strength data was performed to compare different replacement mixes with a control mix.