Assessment of Bond Strength Using Recycled Brick Aggregate Concrete for Sustainable Construction

Abstract

This study investigates the bond strength of recycled brick aggregate concrete (RBAC) in un-strengthened lap spliced reinforced beams, contributing to sustainable construction practices. The research examines the effects of partial replacement of coarse aggregate with recycled brick aggregate (20% and 40%), concrete cover to bottom bar diameter ratio (1 and 2), and lap splice lengths (20Db and 30Db) on bond strength. Hardened properties of RBAC were assessed using 150mm diameter by 300mm height cylindrical specimens after 28 days of curing. Experimental modulus of elasticity values of RBAC were compared with existing predictive models. The Akhtaruzzaman et. al. model demonstrated superior accuracy, predicting results within a 6% range, while other models proved inadequate for RBAC applications. Compressive strength tests revealed decreases of 6% and 24% for RBAC 20 & 40, respectively, compared to control specimens. Seven beam specimens (1800mm length, 200x250mm cross-section) were casted with varying lap splice lengths, bottom concrete covers, and RBAC compositions. Steel strain gauges installed at the loaded end of spliced reinforcing bars measured strain during loading, from which stress was calculated. Four-point bending tests were conducted under monotonic loading, with data collected via a data logger throughout testing. Experimental results were compared with numerical simulations using OpenSeesPy, achieving ±5% accuracy in load-deflection responses. The experimentally calculated stress in lap spliced steel was compared with existing models to assess their applicability to RBAC reinforced beams. While Cho and Pincheira’s (2006) model showed better results compared to other models, but still lacked sufficient accuracy for RBAC beams. Consequently, a new model was developed using regression analysis with the Gauss – Newton algorithm. The proposed model demonstrates high accuracy with an R² value of 0.9497, making it suitable for predicting stress in spliced steel in RBAC beams. This research provides valuable insights into the behaviour of RBAC in structural applications and offers a reliable model for predicting bond strength, contributing to the advancement of sustainable construction techniques