Rheological and mechanical properties of cement–fly ash self-consolidating concrete incorporating high volumes of alumina-based material as fine aggregate

• Properties of SCC that both incorporates fly ash and AW were studied.
• Fly ash is used as a cement replacement at a fixed 20% wt.
• AW is used as a fine aggregate replacement at 0%, 25%, 50%, 75%, and 100% wt.
• SCC mixtures containing AW of up to 75% had higher compressive strength concrete.

Portland cement and natural aggregate are the materials consumed in the greatest quantities in the production of concrete and are thus associated with environmental problems. The 3R keys principles for the production of concrete materials that are relatively environmentally friendly are reduce, reuse, and recycle. This paper presents a laboratory study on the properties of self-consolidating concrete (SCC) incorporating fly ash and recycled alumina waste. Fly ash is used as a cement replacement at a fixed 20%, and recycled alumina waste is used as a fine aggregate replacement at 0%, 25%, 50%, 75%, and 100%. The mixtures were designed to produce a controlled slump flow diameter. The properties examined in the study are workability and mechanical properties by using slump flow, J-ring flow, blocking flow assessment, V-funnel, compressive strength, and ultrasonic pulse velocity measurements. The results show that the use of fly ash and recycled alumina waste significantly improved the workability and increased the compressive strength of SCC mixtures. Further, all the mixtures showed an acceptable performance in regard to slump flow diameter and time tests. Mixes with high cement content and fly ash content into which recycled alumina waste content of up to 75% was incorporated had substantially lower V-funnel flow times and minimal blocking, flow times in the range of 4–6 s, V funnel times in the range of 8–12 s, and a difference in the slump flow and J-ring flow in the range of 2–3 cm. These mixes also exhibited minimal or no apparent blocking compared with conventional SCC. The results further indicate that economical SCC with 28-day compressive strength up to 56 MPa can be made using a high volume of recycled alumina waste, which is accompanied by a decrease of only one unit of strength.