ABSTRACT
Quarry aggregate reserves are depleting fast, particularly in some desert regions of the world. Worldwide Quarry aggregate production is about 4.5 billion tonnes, and Australia alone consumes about 130 million tonnes of aggregates annually. The process energy usage and greenhouse gas emissions from Quarry aggregate is around 7.4 to 8.0 kg CO2-e per tonne. Aggregate demand is also increasing with the expansion of construction. In contrast, the annual production of premix concrete in Australia is about 30 million cubic meters, and 3‒5 % of concrete delivered to site remains unused and ends up in the landfills or crushing plants. Thus, manufacturing coarse aggregates using waste concrete is a sustainable approach in terms of environmental and economic aspects. This paper presents the mechanical performance results of concrete produce using a novel manufactured coarse aggregate recycled directly from premix concrete. A series of mixes of were produced using this manufactured coarse aggregate with the replacement by weight of quarry aggregate by 25%, 50%, 75% and 100%. The mixes investigated were 100% Ordinary Portland cement and 25% replacement with Fly Ash for a 25 MPa and a 32 MPa concrete. All mixes were tested at 7 and 28 days for the compressive strength, and then compared with the concrete produced with quarry aggregate. Test results demonstrated that concrete produced with the recycled aggregate achieved a mean 28 day compressive strength equivalent to that of natural granite aggregate for the 25 MPa mix and slightly lower (1-3 MPa) for the 32 MPa mix. No effect on compressive strength was observed based on the level of replacement of recycled aggregate added.
