Properties of green prepacked composites produced with slag cement: efficient recycling of micronized waste marble powder and waste wood sawdust

This study aims to experimentally investigate the potential of recycling waste marble powder (WMP) and waste wood sawdust in green prepackaged composites. Using low-carbon emission slag cement, the study evaluated the mixtures prepared with different WMP ratios (25%, 50%, and 100%) and sawdust volumes (5%, 7.5%, and 10%). Fresh, physical, mechanical, and durability properties were tested; the effects of sodium silicate (Na₂SO₄) exposure, high temperature, and freeze–thaw cycles were investigated. The results show that WMP increases the flowability of the mixture and provides a homogeneous matrix structure when used with low sawdust ratios. It was determined that 50% WMP and 5% sawdust ratio provided optimum performance due to tight packing density and low void ratio. However, using 100% WMP and high-sawdust ratios negatively affected the durability performance by disrupting the matrix homogeneity. At high temperatures, the thermal resistance of WMP decreased, while sawdust’s porosity and microcrack formation increased. In freeze–thaw cycles, WMP and sawdust ratios caused significant mass loss and compressive strength changes. SEM analysis has shown that WMP and sawdust ratios determine microstructural homogeneity, porosity, and microcrack formation, and adversely affect binder phase thermal stability and mechanical strength, particularly at high temperatures. 25–50% WMP and 5% sawdust ratios provided the most balanced results between environmental sustainability and mechanical performance. These findings emphasize that WMP and sawdust ratios should be carefully optimized for sustainable construction material production.