Geopolymers Manufactured by the Alkali Activation of Mining and Ceramic Wastes Using a Potential Sustainable Activator from Olive Stone Bottom Ashes

The reuse of by-products as alternative raw materials to traditional construction materials is required in order to ensure sustainable development in the construction sector and is a significant and important focus in the fields of materials science. This study developed geopolymers using by-products from mining, ceramics, and olive industries, including slate stone cutting sludge (SSCS) and chamotte (CH) as aluminosilicate sources, and olive biomass bottom ash (OSBA) as an alkaline activator with sodium silicate. A key novelty of the research lies in the use of SSCS, an underexplored by-product in geopolymerization studies, as a viable aluminosilicate source. The geopolymers were prepared with varying weight ratios of SSCS, CH, and OSBA/Na₂SiO₃ (1.7, 1.9, 2.2, and 2.4). Physical and mechanical tests determined the optimal formulation, while FTIR and SEM analyses revealed the material’s chemical and structural evolution. The FTIR analysis detected the quartz and carbonate phases, indicating incomplete quartz dissolution and carbonate formation during calcination. The SEM analysis revealed a dense microstructure with reduced porosity and enhanced geopolymerization in samples with higher OSBA content. The optimal geopolymer (60% OSBA, 30% CH, OSBA/Na₂SiO₃ ratio of 2.2) achieved a compressive strength of 33.1 MPa after 28 days. These findings demonstrate the feasibility of producing geopolymers using SSCS, CH, and OSBA, promoting the reuse of industrial by-products as sustainable alternatives to conventional binders.