Sustainable self-compacting mortars incorporating calcined bentonite and recycled glass powder: time-dependent mechanical and durability performance assessment

In response to the growing demand for sustainable construction practices, this study evaluates the potential use of calcined bentonite (CB) and recycled glass powder (GP) as supplementary cementitious materials in self-compacting mortar (SCM). The environmental objective is to reduce the reliance on Portland cement, which is a major contributor to CO₂ emissions, by incorporating industrial and post-consumer waste materials. In mixtures, CB was introduced at replacement levels of 5, 10, 15, and 20%, while GP was added at levels ranging from 5 to 25% by weight in binary and ternary binders. A comprehensive assessment of the fresh properties, including mini-slump flow, V-funnel flow time, yield stress, and plastic viscosity, was conducted, alongside mechanical and durability tests such as compressive strength, water absorption, acid resistance (5% HCl) and sulfate attack (5% K₂SO₄). Results indicate that, CB decreases the flowability of SCM mixtures, necessitating a higher dosage of superplasticiser. However, when combined with GP, the flowability improves significantly, reducing the demand for superplasticiser. Optimal mechanical performance was observed in mixtures containing 15% CB and 0% GP, as well as 10% CB with 5% GP, which achieved compressive strength improvements of 12% and 13%, respectively, after 90 days. Moreover, the incorporation of higher GP contents (15–25%) enhanced the mortar’s resistance to hydrochloric acid and potassium sulfate solution, highlighting its contribution to long-term durability. These findings support the valorization of calcined clays and glass waste as viable alternatives for developing sustainable and cost-effective SCM, while reducing environmental impact in the construction industry.