Evaluating the fitness for reuse of earth blocks reclaimed from load-bearing masonry: The case for compressive strength

Abstract

Retrieving masonry units for reuse is a promising circular strategy to reduce environmental impacts, yet their technical suitability for reuse remains insufficiently understood. Earth blocks are relatively easy to reclaim, and this study is the first to assess whether they retain adequate performance after reclamation from load-bearing structures. Fitness for reuse was evaluated by comparing the compressive strength of blocks before and after sustained loading. The effect of sustained loading was isolated in the laboratory through a controlled testing sequence that comprised sustained loading of masonry columns, deconstruction and cleaning of blocks, and testing of both new and reclaimed blocks. Columns were built using commercially available nonstabilised moulded earth blocks (MEBs) and cement-stabilised compressed earth blocks (CEBs), combined with thick-bed earth mortar (EM) and thin-layer earth-adhesive mortar (EAM). Blocks were reclaimed using a hammer drill and cleaned with a joint knife. Large sample sizes of both new and reclaimed blocks were tested, and inferential statistics, including independent t-tests and General Linear Models (GLMs), were applied to detect changes in compressive strength. Results show that sustained loading affects compressive strength differently across blockmortar combinations. MEBs consistently exhibited increases of 6% and 11%, depending on mortar type, whereas CEBs showed either a reduction of 6% or no change, depending on block orientation. The findings demonstrate the fitness for reuse in both block types based on compressive strength, but highlight the need to assess whether CEB strength reductions stabilise or worsen under prolonged loading and to investigate the underlying mechanisms driving these changes.