Integrating technical-environmental-economical perspectives for optimizing rubber content in concrete by multi-criteria analysis

Abstract

Removal of waste tyre rubber (WTR) has turned into a critical ecological hazard all around the world and one of the viable solutions for the recycling is to use as a filler or substitute aggregate in concrete mixture. Although there are many of material performance study, the useful framework for decision making policy integrating its technical-environmental-economic performance is still missing. This study empolyed four types of multi-criteria-decision-making (MCDM) techniques to suggest the the priority of opitmum rubberized concrete mixture. In experimentation, three types of rubberized concrete were formulated by replacing, cement, fine (sand) and coarse (gravel) aggregate up to 20 % in vol. with WTR of powder, crumb and chip, respectively. For technical perspective, there are 10 criteria. Thus, fresh properties, designated mechanical properties (compressive, splitting tensile and flexural strengths) along with durability (chloride ion penetration resistance) tests were conducted. Besides, for environmental and economic perspectives, volume utilization of raw material, CO₂ footprints, and cost were quantified. Experimental observation reveals that in technical perspective the performance of rubber crumb incorporated concrete has better properties among all mixtures. However, the CO₂ emissions and cost were less for powder rubber incorporated concrete and raw material conservation is better for rubber chip incorporated concrete. Finally, all perspectives were integrated, and a framework was developed, having 13 criteria and the weightage of each criterion was evaluated by Entropy method. As a result, 5% rubber chip concrete showed the top ranking. Obtained result has a wide application for selection of concrete according to its application; structural, non-structural, geotechnical etc., and may help the policy makers to use WTR in construction industry.