Analysis of the Compressive Strength of Concrete with Recycled Coarse Aggregate and FCC as a Substitute for Fine Aggregate

Abstract

This study evaluates the compressive strength of plain concrete produced with total replacement of conventional aggregates, using recycled coarse aggregate (RCA) and spent fluid catalytic cracking (FCC) catalyst as a substitute for fine aggregate, in comparison with plain concrete manufactured with natural aggregates. The research is developed within the context of the need to promote sustainable practices in construction, reduce the consumption of natural resources, and minimize the environmental impact associated with the management of industrial and demolition waste. The methodology was structured in three phases: (i) physical and mechanical characterization of the RCA and FCC, (ii) design and production of concrete mixtures with 100% recycled aggregates and reference mixtures with 100% natural aggregates, and (iii) evaluation of compressive strength and the economic impact of using recycled materials. The tests were conducted in accordance with NTE INEN and ASTM standards, and compressive strength was evaluated at curing ages of 7, 14, and 28 days. The results showed an approximate 70% reduction in the compressive strength of concrete with total replacement compared to conventional concrete, reaching values of 74.17 kg/cm² and 239.74 kg/cm² at 28 days, respectively. From an economic perspective, the use of RCA and FCC increased the cost per cubic meter of concrete from $100.90 to $291.77. It is concluded that the total replacement of natural aggregates with RCA and FCC is neither technically nor economically viable for structural applications; however, it shows potential for non-structural uses, contributing to waste valorization and the promotion of the circular economy in the construction sector.