Erosion of geopolymers made from industrial waste

Solid-particle erosion studies were conducted on geopolymers derived from various combinations of granulated blast-furnace slag, flyash, sand, clay, and rock. The erodent particles were 390-μm angular Al₂O₃, which impacted at 30, 60, or 90° at a velocity of 50, 70, or 100 m/s. Steady-state erosion rates were obtained as weight of target lost per weight of impacting particles. Material-loss mechanisms were studied by scanning electron microscopy (SEM). All of the geopolymers responded to normal impact as conventional brittle solids, but impact at 30° led to anomalously rapid erosion, probably because of presence of microcracks and consequent enhanced removal of aggregates within the geopolymers. Erosion rates at 90° impact were proportional to erodent velocity to the 2.3–2.7 power. The geopolymers exhibited crushing strengths of approximately 32–57 MPa. Erosion rate correlated with density and strength for geopolymers of similar composition. All of the geopolymers that contained flyash were more resistant to erosion than was the geopolymer without flyash.