Development of durable concrete from C&D waste by adopting identical mortar volume method in conjunction with two-stage mixing procedure

Abstract

This article discusses on identical mortar volume method for preparing RAC, where the sum of the adhered mortar and the additional mortar volume required for the concrete mix is exactly equal to the mortar volume required for preparing the conventional natural aggregate concrete. This method of mix design, along with the proposed two-stage mixing procedure not only reduces the ingredient of concrete but also enhances the properties as compared to RAC produced with conventional mix design method. The suitable percentage of RCA component for the above mix design method depends on the residual mortar content of the source RCA. The identical mix design method, along with one proposed two-stage mixing procedure, results reduction in property of compressive strength, splitting tensile strength and static modulus by only 5.04%, 4.55% and 2.64%, respectively as compared to the conventional natural aggregate concrete after 28 days of curing. Similarly, creep strain deformation, carbonation depth, water penetration depth, drying shrinkage and charge passed are enhanced by only 11.02%, 5.0%, 5.49%, 8.25% and 5.3%, respectively than that of natural aggregate concrete. The reason for the above complete improvement in properties of RAC and the ITZs is investigated through microstructural investigation. The presence of strength imparting elements is found out through quantitative analysis.