Utilization of recycled crumb rubber as fine aggregates in concrete mix design

There is no doubt that the increasing piles of used tires create environmental concerns. As waste continues to accumulate and availability and capacity of landfill spaces diminish, agencies are increasing application and use of recycled materials such as crumb rubber from tires in construction. The basic building materials in concrete construction are primarily aggregate and cement. The educated use of recycled materials can result in reduced cost potentials and may enhance performance; however, not all recycled materials are well suited for concrete construction applications. The two main reasons for not utilizing a reclaimed material are (1) addition of material is a detriment to performance, and (2) excessive cost. In this study, the performance of recycled materials crumb rubber as valuable substitute for fine aggregates ranging from 0% to 100% in replacement of crushed sand in concrete mixes is investigated. An acceptable compressive strength was obtained with up to 25% by volume replacement of fine aggregates with crumb rubber.

► Good compressive strength results were recorded at rubber contents lower than 25% in replacement of crushed sand.
► Lower density → lower weight. Up to 8% reduction in density was recorded at 25% rubber in substitution of crushed sand.
► Enhanced ductility of concrete advantageous for usage in highway barriers or other similar shock-resisting elements.
► Replacing more than 25% of fine aggregates with rubber crumb causes the compressive strength of concrete to drop extremely.
► Material is unpredictable, failure stress strain relationship does not follow a fixed pattern in experiments at same point.