Utilization of waste engine oil for expanded clay aggregate production and assessment of its influence on lightweight concrete properties

Abstract

The generation of waste engine oil (WEO) is characterized by high volumes since 24 × 106 tons of WEO are discarded annually. The chemical composition of WEO presents heavy metals dangerous to both humans and the environment and, thus, valorization alternatives of WEO are a major challenge. Consequently, this study evaluates the feasibility of WEO as an expansive additive to be used in the production of expanded clay aggregates (ECAs) for lightweight concrete (LWC) applications and assesses the effects of these ECAs on physical and mechanical concrete properties. Initially, WEO was chemically characterized and then, an optimization of the ECA production was assessed modifying WEO dosages, thermal cycles, and initial sizes of clay granules. Subsequently, morphological, physical, chemical, and mechanical properties of optimized ECAs were obtained through scanning electron microscopy, energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, abrasion and impact resistance and compressive strength tests to validate the feasibility of these ECAs as coarse aggregates in LWC. Then, the incorporation of ECAs in LWC was assessed using four concrete mixes with increasing volume dosages of ECAs replacing natural coarse aggregates (i.e.; 0%, 25%, 50%, 100%) and its impact on physical and mechanical concrete properties was evaluated. Positively, ECAs significantly reduced concrete bulk density, but with a collateral negative impact on the mechanical performance of concrete mixes as ECA dosages increased. For a 50% ECA replacement, density and compressive strength values were 1980 kg/m3 and 19 MPa, respectively, representing reductions of 13% and 2% with respect to the plain concrete, respectively, and successfully satisfying LWC requirements for structural applications.