Experimental investigation on the mechanical properties of concrete utilizing pre-coated Brick-Concrete recycled coarse aggregates

Abstract

In this study, low water-cement ratio composite cementitious materials were utilized to pre-coat the brick-concrete recycled coarse aggregate (BCRA), and a two-stage mixing method was proposed to pre-coat BCRA and produce the recycled concrete together. The compressive and tensile strength, fracture behavior, and uniaxial compressive stress–strain properties of five concrete groups, including untreated or pre-coated BCRA and natural aggregate concrete, were experimentally investigated. The results show that the 28 days compressive strength fcu and split tensile strength fst of pre-coated BCRA concrete were 9.9% and 7.7% higher, respectively, than those of untreated BCRA concrete, while using the same amount of total cementitious material. The notched beam three-point bending test revealed that utilizing untreated BCRA tends to deteriorate the brittle fracture behavior of concrete. The two-stage mixing method demonstrated the most significant improvement in enhancing the anti-crack initiation ability of BCRA concrete, while pre-coated BCRA exhibited greater effectiveness in improving BCRA concrete's unstable fracture toughness. Additionally, uniaxial stress–strain curves of five test groups were discussed and the backscattered electron analyses were conducted to gain a better understanding of their mechanical behaviors.