Evaluating the Strength Development of Ceramic Waste Powder–Silica Fume Geopolymer Mortars: Compressive and Tensile Behavior

Abstract: The sustainable advancement of construction materials has enabled the integration of industrial by-products to reduce carbon emissions and foster circular economy efforts. This study examines the synergistic impacts of ceramic waste powder (CWP) and silica fume (SF) as partial replacements for conventional aluminosilicate precursors in hybrid geopolymer mortars (HGM). The hybrid system incorporates CWP and SF at varying replacement levels to assess their impact on the fresh and hardened properties of geopolymer mortars. The integration of CWP elevates the packing density of the matrix, whereas SF, noted for its fine particles and considerable pozzolanic activity, promotes the geopolymeric reaction and improves microstructural densification. Microstructural investigation by scanning electron microscopy (SEM) confirms the formation of thick, well-adhered geopolymer gels with negligible microcracking. The results suggest the feasibility of utilizing ceramic waste and silica fume in the manufacture of high-performance, sustainable hybrid geopolymer mortars for environmentally efficient construction purposes. The experimental results demonstrate that a hybrid geopolymer mortar containing 40% ceramic waste powder (CWP), 40% silica fume (SF), and 20% cement (CW3 mix) exhibited enhanced mechanical performance under all curing conditions. This mixture attained a compressive strength of 27 MPa and a splitting tensile strength of 2.6 MPa at 28 days, exhibiting an ideal tensile-to-compressive strength ratio of 0.10. Water curing produced the most favorable overall strength development, although oven curing at 70°C and 100°C expedited early strength attainment. Mixtures with uneven CWP or SF concentration exhibited diminished performance, underscoring the significance of synergistic hybridization. Microstructural investigation verified the development of dense, well-organized geopolymer matrices with no microcracking, substantiating the viability of CWP and SF as sustainable additional cementitious materials.