Recycling of geosourced materials through geopolymerization: Towards sustainable and high-performance earth bricks for resilient construction

The construction sector consumes about 40 % of global energy and produces 36 % of CO₂ emissions, highlighting the urgent need for low-carbon alternatives. In Morocco, vernacular earthen buildings are valued for thermal efficiency but remain structurally vulnerable to seismic and climatic stresses, as shown by the 2023 Al Haouz earthquake. This study explores the recycling of soils from traditional ruins and their upgrading by geopolymerization, a low-carbon alternative to Portland cement. Four locally available materials (pozzolan, kaolin, sandstone, and limestone) were combined and activated with a solution of sodium hydroxide (14 M) and sodium silicate (Na₂SiO₃), dosed at 1 % of the mixing water, to produce compressed earth bricks. Results show remarkable mechanical and durability improvements. Pozzolan-based bricks with 10 % content achieved compressive strength of 26 MPa and tensile strength of 2.6 MPa, representing more than 1200 % gain compared with untreated samples. Kaolin-based bricks reached 19 MPa, while sandstone and limestone acted mainly as fillers, improving compactness despite lower reactivity. Water absorption decreased from 13 % in untreated samples to below 6 % in optimized formulations, corresponding to a 55 % reduction in permeability. These results confirm the high reactivity of pozzolan and kaolin and highlight the complementary role of sandstone and limestone in densification. Compared with Portland cement stabilization, geopolymerization could reduce carbon emissions by up to 70 %, offering a viable pathway for climate-resilient construction. These findings confirm the feasibility of transforming local soils into durable, eco-friendly materials suited to Morocco’s seismic and semi-arid contexts, supporting energy efficiency, seismic safety, and the valorization of local resources in line with national energy transition goals. • Geopolymerization boosts earth brick strength up to 26 MPa. • Kaolin and pozzolan ensure superior mechanical performance. • Water absorption reduced below 6 % in optimized samples. • Local soils recycled for sustainable, eco-friendly construction. • Compact, durable bricks adapted to arid Moroccan climates.