Retrieving earth blocks from masonry couplets for reuse: The role of bond strength

Abstract

Earth block masonry (EBM) is experiencing a resurgence as an environmentally responsible alternative to conventional brick or concrete block masonry. While strong bonds between masonry units and mortar are typically desired for structural performance, they pose challenges for reclamation and reuse at the end of a building's life cycle. This study reviews the literature on bond strength and investigates how EBM's lower bond strength can facilitate block-mortar separation for reuse. It also explores the effects of prewetting earth blocks before laying to enhance bond strength for structural performance and wetting masonry to reduce bond strength before reclamation. Flexural bond strength is determined using the bond wrench test on masonry couplets for both stabilised and non-stabilised earth blocks and mortars. Reclamation potential is assessed by deconstructing couplets and cleaning recovered blocks using standard tools. The results show that most earth block-mortar combinations have sufficiently low bond strength for easy reclamation. Wetting before reclaiming effectively reduces the bond strength and facilitates the deconstruction of stabilised earth blocks with earth mortar and earth-silicate mortar. The impact of prewetting before laying is less significant. Establishing bond strength benchmarks for specific building applications is recommended to balance structural requirements with reclamation potential in circular construction. Future research should investigate the technical properties of reclaimed blocks, including the bond strength, to assess their suitability for reuse. The decision to prioritise reuse over recycling should consider tradeoffs between economic, organisational, and environmental factors.