Evaluating the reclamation performance of earth block-mortar combinations

Abstract

The relatively low bond strength of earth block masonry compared to conventional masonry offers opportunities for circular construction through block reclamation and reuse. Given the absence of a standardised approach, this study proposes a method for evaluating reclamation performance, tested across five representative earth blockmortar combinations. Additionally, bond strength and bond capacity were evaluated statistically as potential predictors of reclamation performance. Non-stabilised moulded earth blocks (MEBs) and cement-stabilised compressed earth blocks (CEBs) were paired with three mortars: earth mortar (EM), thin-layer earth-adhesive mortar (EAM), and bastard-earth mortar (BME). Ten masonry walls were deconstructed using a hammer drill, after which blocks were cleaned with a joint knife. Reclamation performance was assessed using nine effectiveness and efficiency indicators derived from quantitative damage measurements, identification of new failure modes, time recordings, and qualitative ratings. Spearman correlation tests were used to evaluate four potential predictors: shear and flexural bond strength, and shear and flexural bond capacity. CEBs with EM achieved the highest reclamation rate (94%) and efficiency, and the lowest bond strengths (<0.08 MPa). MEB-EM and MEBEAM also achieved high reclamation rates (85% and 91%), but reduced cleaning efficiency, with moderate-tohigh bond strengths (<0.21 MPa). CEB-EAM achieved a poor reclamation rate (28%) and low reclamation efficiency, yet showed the highest bond strengths (>0.26 MPa). CEB-BME achieved the lowest reclamation rate (13%) and efficiency, with moderate bond strengths (similar to 0.15 MPa). Although reclamation outcomes are also influenced by additional material properties, such as block and mortar strength, the shear bond strength and shear bond capacity correlate significantly with reclamation and deconstruction performance indicators, respectively. Future research should reproduce the experiments with different unit-mortar combinations to further validate the proposed method and assess the influence of other material properties on reclamation performance.