Use of waste glass-based SCMs and slurry water to increase excess concrete revalorization into more sustainable gravity blocks

Cement production is a major contributor to global CO₂ emissions, while large volumes of excess concrete and other waste streams remain underutilised. This study investigates a revalorisation pathway where excess concrete is reused in the manufacture of gravity retaining wall blocks, incorporating waste glass-based supplementary cementitious materials (SCMs) and concrete slurry water. The reactivity of the glass-based SCMs was evaluated under room-temperature and 40 °C curing, showing limited reactivity at room temperature but clear reactivity when cured at 40 °C. This highlights a limitation of the widely used R³ heat-release test for this class of materials. Thermogravimetric analysis (TGA–DTG) was conducted using a novel slope-based method, where decomposition ranges are defined by zero-slope points rather than fixed literature values, improving the accuracy of hydration product quantification. Mechanical testing and cradle-to-gate life cycle assessment (LCA) were also performed, linking material performance with environmental outcomes. The findings advance methodological assessment of SCM hydration and support the sustainable design of structural blocks made from revalorised excess concrete. • Novel valorisation of excess concrete using glass-based SCMs and slurry water. • First assessment of glass wool as a supplementary cementitious material. • Reactivity testing revealed limits of R³ method under room conditions. • Heat curing at 40 °C improved SCM reactivity without extra environmental cost. • Cradle-to-gate LCA showed transport distance dominates GWP.