Sulfate and thermal resistance of low-clinker high-strength concrete incorporating hybrid blended waste powders

Hybrid blended waste powders can produce high-strength concrete with improved durability while reducing embodied carbon and, in some blend configurations, material cost. Across nine mixtures prepared at constant water-to-binder ratio (0.30) and cement replacement up to 35%, silica fume and dealuminated kaolin produced the most pronounced performance gains through coupled packing and pozzolanic refinement. The best strength development was achieved by the silica fume-dealuminated kaolin ternary blend, which increased 28-day compressive strength by about 37% relative to the control, alongside substantial improvements in tensile- and flexural-related response. Transport indicators consistently decreased in the blended systems, with water absorption reduced by roughly 50% and penetration depth reduced by up to about 37%, indicating disrupted capillary connectivity and improved interfacial integrity. Under 10% sodium sulfate immersion for eight months, silica fume bearing binders showed the highest strength retention, confirming that sulfate resistance was governed by the combined effects of restricted ingress and reduced susceptibility to expansive reactions. After heating to 500 ^o C, SEM/EDX evidenced a shift toward more silica-rich binding gels and lower Ca/Si ratios in the optimum blends, consistent with reduced crack continuity and higher residual performance. The quaternary blend delivered the largest sustainability benefit, reducing embodied carbon by ~ 33% and unit cost by ~ 4.5% while maintaining high-strength performance.