Feasibility of Developing Sustainable Concrete Using Environmentally Friendly Coarse Aggregate

Abstract

Quarry aggregate reserves are depleting rapidly within Australia and the rest of the world due to an increasing demand for aggregates driven by expansion in construction. The annual production of premix concrete in Australia is approximately 30 million cubic meters, while 3–5% of concrete delivered to site remains unused and is disposed of in landfill or crushing plants. The production of coarse aggregates using this waste concrete is potentially a sustainable approach to reduce environmental and economic impact. A testing program has been conducted to investigate mechanical performance and permeation characteristics of concrete produced using a novel manufactured coarse aggregate recycled directly from fresh premix concrete. The recycled coarse aggregate (RCA) concrete satisfied the specified 28-day design strength of 25 MPa and 40 MPa at 28 days and a mean compressive strength of 60 MPa at 90 days. Aggregate grading was observed to determine strength development, while low water absorption, low drying shrinkage, and higher packing density indicate that the RCA concrete is a high-quality material with a dense pore structure. The rough fracture surface of the aggregate increased the bond between C-S-H gel matrix and RCA at the interfacial transition zone. Furthermore, a good correlation was observed between compressive strength and all other mechanical properties displayed by the quarried aggregate concrete. The application of design equations as stated in Australian standards were observed to provide a conservative design for RCA concrete structures based on the mechanical properties.

A sustainable approach in using construction and demolition waste materials in concrete

“…The sieve analysis was conducted to determine the size distribution of all used aggregates using sieve sizes, which were normally applied for grading purposes in accordance to BS 882:1992. The grading of aggregates is basically required to produce concrete with adequate workability, minimum segregation and shrinkage cracking and bleeding (Gunasekara et al, 2020). Figure 2 illustrates the cumulative percentage passing versus the logarithmic sieve size for the NFA and sieved C&DWM together with the grading limits specified in BS 882:1992.…”