Use of recycled alumina as fine aggregate replacement in self-compacting concrete

Alumina is a common by-product of industrial grit blasting operations. While alumina itself is relatively harmless, the grit blasting waste is regarded as hazardous when contaminated with heavy metals. The concrete industry has initiated the use of solid waste additives in order to address environmental problems. We studied the feasibility of using alumina waste (AW) as a partial replacement for the fine aggregate in self-compacting concrete (SCC). The mixtures were designed to produce a controlled slump flow diameter. The fine aggregate was replaced with up to 100% AW by weight. The rheological and mechanical properties of the SCC mixtures were evaluated based on slump flow, J-ring flow, blocking assessment, V-funnel, air content, compressive strength, and ultrasonic pulse velocity measurements. The filling and passing ability of the fresh concrete decreased in proportion to the alumina content. Mixtures containing up to 75% AW possessed average compressive strengths of 20.9 MPa at 3 days and 45.9 MPa at 28 days.