Hybrid alkali-activated slag composites incorporating porcelain polishing residue and marble waste with basalt fiber: Mechanical, durability, and microstructural performance

This study investigates the mechanical, physical, and durability performance of hybrid alkali-activated slag composites (AACs) incorporating porcelain polishing residue (PPR) as a partial replacement for ground granulated blast-furnace slag (GBFS), waste marble powder (WMP) as fine aggregate, and basalt fiber (BF) as reinforcement. Sixteen mixtures were formulated with 0-20 wt% PPR and 0-1.0 vol% BF and thermally cured at 80 degrees C for 8 h. The reference mixture with 0.25 % BF (0C25F) achieved the highest compressive strength of 30.38 MPa, representing a notable improvement over the unreinforced control (26.26 MPa). Incorporating 10 % PPR with 0.5 % BF (10C50F) yielded 25.85 MPa, about 9 % higher than the fiber-only reference (0C50F). Flexural strength followed a similar pattern, peaking at 3.30 MPa for 1.0 % BF and 2.98 MPa for 10 % PPR + 1.0 % BF, reflecting up to a 47 % enhancement compared with the unreinforced matrix. The lowest sorptivity (0.40-0.66 kg/m & sup2;) occurred in mixtures with 10 % PPR and 0.25-0.5 % BF, indicating excellent compactness and reduced permeability. At elevated temperatures, compressive strength increased by + 38.5 % at 200 degrees C (10C25F), and residual strength losses at 600 degrees C were limited to approximately 14 %, demonstrating superior thermal stability. After 90 days of MgSO4 exposure, the optimized mixture (10C25F) retained over 85 % of its initial compressive strength, whereas excessive PPR or fiber content led to severe degradation (up to -52 %). Freeze-thaw testing for 120 cycles confirmed that mixtures with 10 % PPR + 0.25-0.5 % BF experienced minimal mass loss (<= 2 %) and strength reduction (< 10 %), while high PPR or BF levels caused surface scaling and losses exceeding 25-30 %. These results confirm that moderate levels of ceramic waste and fiber reinforcement act synergistically to improve mechanical performance, impermeability, and long-term durability. The combination of 10 % PPR and 0.25-0.5 % BF produced a dense, durable, and thermo chemically stable alkali-activated matrix, demonstrating that integrating ceramic and marble wastes with basalt fiber enables eco-efficient, and high-performance composites aligned with circular economy and sustainability principles.