This paper investigated the effect of combining rubber crumbs with recycled aggregates and fly ash on the mechanical properties and environmental impact of concrete. Increasing the amount of rubber crumbs linearly reduced strength and Young's modulus regardless of aggregate or binder type, but the effect of recycled aggregate on strength decreased as the amount of rubber crumbs increased. Air permeability also increased with the amount of rubber crumbs but the effect of recycled aggregates varied, as it was constant in the case of non-fly ash but completely reduced with fly ash. The mechanical-environmental efficiency was calculated by weighting the strength by the volume of raw materials, and recycled aggregates were found to have the highest efficiency whereas rubber crumbs were inefficient. When setting a specific strength level, the weighted strength could be used to select the most efficient combination of waste materials.
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