Reclaiming earth blocks: Reclamation performance, fitness for reuse, and circular design strategies for earth block masonry

Abstract

Within the circularity paradigm, two complementary yet frequently disconnected approaches can be distinguished in the construction sector. The first emphasises the use of low-impact, renewable, or regenerative building materials, primarily targeting the early life cycle by reducing embodied energy, greenhouse gas emissions, and resource depletion during material production. The second focuses on extending the service life of materials through strategies such as design for longevity, disassembly, and reuse, thereby limiting waste generation at the end of life and avoiding the environmental burdens associated with producing new materials in subsequent life cycles. This research bridges these perspectives by investigating the reclamation potential of earth blocks as an alternative end-of-life strategy to recycling or disposal. Earth blocks are widely recognised for their low environmental impact during production and are often presumed to be inherently circular at the end of life. While production-related benefits are well documented, the practical feasibility of reclaiming and reusing earth blocks remains poorly understood. This knowledge gap is particularly relevant in Western Europe, where the contemporary revival of earth construction is relatively recent and professional renewed interest in earth construction is relatively recent and professional experience with end-of-life strategies for earth block masonry is limited. Earth blocks are frequently promoted as fully recyclable or harmlessly disposable materials. In practice, such claims are problematic. The reshaping and recycling of earth materials through their inherent plasticity is only feasible for non-stabilised blocks and mortars, while the disposal of earth construction waste in the natural environment is not legally permitted, even when non-stabilised. To overcome barriers to wider adoption, such as low strength, limited durability, and moisture sensitivity, earth blocks and mortars are often stabilised with cement or lime. Although stabilisation improves mechanical and durability performance, it also increases embodied carbon and compromises recyclability and degradability, thereby weakening the presumed circular advantages and strengthening the rationale for reuse rather than recycling or disposal. Against this background, the research examines the reclamation potential of earth blocks from a technical perspective, structured around three key aspects: reclamation performance, fitness for reuse, and circular design strategies. Together, these aspects address whether earth blocks can be reclaimed, whether reclaimed blocks are technically viable for reuse, and how earth block masonry can be designed to support circular outcomes at the end of life. First, reclamation performance was investigated to evaluate the effectiveness and efficiency of earth block masonry deconstruction and the cleaning of retrieved earth blocks. Initial feasibility was examined through block-mortar separation in masonry couplets using various reclamation techniques across sixteen earth block-mortar combinations, including both non-stabilised and stabilised blocks and mortars. Next, five representative combinations were selected for further investigation. Experimental work was then scaled up to include twenty masonry test walls constructed in different masonry bonds, as well as a prototype partitioning wall. Reclamation performance was assessed using quantitative and qualitative indicators, including block recovery, damage intensity, failure modes, technique compatibility, simultaneous block release, speed, and ease. The shear and flexural bond strength between blocks and mortar were examined as potential governing factors influencing reclamation outcomes. Second, fitness for reuse was assessed to evaluate the technical performance of reclaimed blocks, with particular emphasis on compressive and bond strengths. Using the five selected block-mortar combinations, masonry columns were subjected to sustained loading to reflect in-service load-bearing conditions. Following unloading, the columns were deconstructed, and reclaimed blocks were tested in compression and statistically compared with new blocks. In parallel, bond strength was investigated in two contexts: the effect of sustained loading on bond strength in masonry couplets, and the bond strength of reclaimed blocks containing residual mortar when recombined with newly applied mortar. Third, circular design strategies were explored to evaluate how earth block masonry can be implemented with end-of-life considerations explicitly integrated into design decisions. Using the reclamation performance and fitness-for-reuse outcomes, the five block-mortar combinations were first benchmarked against conventional masonry in terms of structural performance. Their circular performance was then evaluated using a revised qualitative assessment framework combining a literature review with experimental findings. Finally, their implementation potential was assessed by reviewing literature and technical data on their technical performance and application constraints. On this basis, recommendations were formulated for the use of specific block-mortar combinations in building applications designed for adaptability or longevity. The results demonstrate that reclamation performance and fitness for reuse vary substantially across combinations. Cement-stabilised compressed earth blocks combined with earth mortar exhibited the best reclamation performance and moderate, but sufficient, fitness for reuse. Non-stabilised earth blocks paired with non-stabilised earth mortar and thin-layer earth-adhesive mortar achieved comparable results, although mechanised cleaning is required to improve efficiency. These three combinations are therefore recommended for non-load-bearing interior walls designed for adaptability, where shorter service lives increase the frequency with which reclamation potential can be exploited. In contrast, cement-stabilised blocks with earth-adhesive mortar showed low reclamation performance despite being sufficiently fit for reuse, whereas the same blocks combined with bastard-earth mortar yielded too few reclaimed blocks to assess fitness for reuse meaningfully. Nevertheless, these combinations demonstrated superior structural performance and durability. Given their higher environmental impact and limited recyclability and degradability, they are more appropriate for load-bearing walls designed for longevity, where an extended service life allows embodied energy to be retained for longer and delays the need for replacement with new materials. Although reclamation performance is influenced by multiple interacting factors, including block and mortar properties, masonry configuration, and prior use conditions, the experiments reveal a strong correlation between bond strength and key reclamation performance indicators. Fitness for reuse, assessed through compressive strength, is primarily governed by block type, mortar type, and block orientation within the masonry, while bond strength in reused masonry depends on the residual mortar from prior use and newly applied mortar type. By integrating experimental evidence on reclamation with circular design considerations, this research provides practical guidance for architects, engineers, and manufacturers seeking to implement earth block masonry as circular building systems. Its principal scientific contributions lie in the development of experimental methodologies to assess reclamation performance and fitness for reuse in masonry, and in extending circular assessment frameworks through new principles and indicators based on experimental findings. Ultimately, the study positions earth block masonry not only as a viable candidate for reclamation and reuse but also as a demonstrative case for designing building systems with end-of-life strategies embedded in the outset, contributing to broader efforts to close material loops in construction.