Strength reduction factor of crumb rubber as fine aggregate replacement in concrete

Crumb rubber concrete, in which a portion of the mineral aggregates in concrete is replaced by the waste tire rubber, has attracted great research attention as a sustainable building material. It is a promising solution to the over-exploitation of river sand and the recycling of waste tire rubber. However, the concrete strength decreases significantly when crumb rubbers were used to replace the fine mineral aggregates. A reliable strength reduction model for the crumb rubber concrete with ordinary strength is essential for its practical use in engineering structures. This paper investigates the relationship between the equivalent degree of compaction (EDC) and the strength reduction factor (SRF) of the crumb rubber concrete. A close correlation between the SRF and the EDC was observed, and it can explain that the rubber aggregates in concrete can be regarded as the regular voids. Based on the macro-porosity theory, a new SRF model of crumb rubber concrete was developed. Compressive tests of crumb rubber concrete conducted by the authors and other researchers were employed to fit the relative parameters of the proposed model. Finally, the proposed SRF model was compared with existing models to validate its accuracy against test results.