Enhancing reactivity of granite waste powder toward geopolymer preparation by mechanical activation

Granite waste powder (GWP) is a solid waste produced during stone processing, and its accumulation has brought serious environmental and ecological problems. Due to its rich Si and Al components, GWP is a potential raw material for the preparation of geopolymers, but its low reactivity limits its utilization. This study aimed to enhance the reactivity of GWP toward geopolymer preparation by mechanical activation. During mechanical activation, the particle size of GWP decreased rapidly, and its internal pore volume gradually increased, which made its specific surface area continuously increase. The relative crystallinity of the main mineral phases in GWP decreases continuously with mechanical activation, and the aluminosilicate minerals (including albite, microcline, and biotite) are more easily amorphized than quartz. Leaching tests show that activated GWP can dissolve higher percentages of silicon and aluminum components in alkaline solutions. After 120 min of activation, the dissolution percentage of Si increased from 1.55% to 6.25%, and that of Al increased from 4.83% to 20.86%. The reaction heat result shows that the early geopolymerization involving activated GWP releases higher cumulative heat, which reflects a higher degree of reaction. Also, geopolymer incorporated with activated GWP, its compressive strength increased from 50.83 MPa to 78.94 MPa, and its flexural strength increased from 7.2 MPa to 10.0 MPa. These results confirmed that the reactivity of GWP can be significantly enhanced by mechanical activation. This technology may provide an efficient and promising method to improve the reactivity of GWP and promote its utilization in the preparation of geopolymers.