Assessing The Mechanical And Durability Performance Of Concrete Made Using Recycled Clay Masonry Rubble Bricks (CMRB) As Coarse Aggregates

School of Civil and Environmental Engineering, University of the Witwatersrand, Johannesburg

^* Corresponding author: janina.kanjee@wits.ac.za

Abstract

The South African construction industry is currently faced with mounting construction waste and overflowing landfills. Consequently, the feasibility of using of clay masonry rubble brick (CMRB) as a partial replacement for natural coarse aggregate in concrete was investigated. Three concrete mixes were made using a water-to-binder (w/b) ratios of 0.60. A control mix as well as a mix containing 50% and 100 % replacement of coarse Andesite aggregate with CMRB as coarse aggregate was tested. The compressive strength, shrinkage and durability properties (with respect to oxygen permeability, water sorptivity and chloride conductivity) were assessed. The results show that the incorporation 100% MCR brick as coarse aggregate produced the lowest compressive strength result, the highest shrinkage rate and the least resistance to gaseous ingress and chloride conductivity. The concrete mix containing 50% MCR brick exhibited the least resistance to water absorption through capillary action. The mechanical and durability properties of both concrete mix containing MCR brick was largely affected by the porous nature of coarse masonry rubble. The results can be attributed to a relatively high void ratio leading to the presence of more interlinked pathways within the CMRB aggregate.