Enhancement of mechanical properties of concrete with treated demolition waste aggregate

Abstract

The utilization of recycled aggregate (RA) from the construction and demolition waste (C&DW) in civil engineering applications, has proven to be an eco-efficient environmentally friendly approach to overcome the current environmental concerns. Nevertheless, the poor quality of RA has limited its utilization in high-grade civil engineering applications. To maximize and promote the use of RA, it is essential that an appropriate process of treatment methods is included in the production of RA to improve its properties. This research aimed to examine the effects of various enhancement methods on the mechanical properties (consistency, compressive strength, flexural strength, tensile splitting strength, and elastic modulus) of recycled aggregate concrete (RAC). This research also included microstructure investigation using Scan Electron Microscopy (SEM) images. The enhancement methods used were treating RA by Soaking in Cement-Pulverized Fuel Ash-Silica Fume solution (SCP), Sand Envelope Mixing Approach (SE), and their combination (SCP + SE). The enhanced RACs showed an increased 28-day compressive strength of up to 46 MPa suitable for structural applications. The tensile splitting strength, flexural strength, and modulus elasticity values of the enhanced RACs were 10%, 16%, and 6% higher than that of the untreated RAC. The improved mechanical performance of the enhanced RAC was attributed to the strengthened interfacial transition zone, better overall interlocking of the treated RA with the new cement paste, filled-up pores and micro-cracks, reduced water absorption, and improved aggregate impact value. The SEM images for the enhanced RACs showed better-compacted microstructure, lesser pores and microcracks. The application of the proposed innovative regime of enhancement methods is anticipated to promote the use of RA in the construction industry and provide a better scientific understanding of the performance of concrete produced with 100% treated RA from the C&DW for structural applications.