Recycled materials paper
Haikmoller, T, Olofinjana, A & Gerber, C 2014, 'Comparing the variability in mechanical properties of concrete made from recycled concrete aggregates', in ST Smith (ed.), 23rd Australasian Conference on the Mechanics of Structures and Materials (ACMSM23), vol. I, Byron Bay, NSW, 9-12 December, Southern Cross University, Lismore, NSW, pp. 237-242. ISBN: 9780994152008.
Concrete is the most widely used construction material and we expect its dominance in the mix of construction materials to continue. In view of the environmental impact associated with concrete production, recycling provides a credible path for gaining some green credentials. Recent reports have proven that recycled concrete aggregates (RCA) in proportion of less than 30% of overall aggregate has produced concrete with compressive strengths greater than 25MPa and comparable to those made from fresh quarried aggregate materials. The use of recycled concrete however, is still restricted to non-structural applications mainly because of the reliability issues in service and there is little information on the variability expected in reported values and how these compared with conventional concrete. In this study, we investigated the variability experienced with measurements in laboratory properties of concrete made with various proportions of recycled aggregates using standard split tests. Data obtained were subjected to Weibull statistics and variability is expressed in terms of Weibull modulus. It is shown that characteristic strengths determined through Weibull statistics followed similar trend with previously published data on compression strengths. The Weibull moduli of 10 – 24 determined for RCA concrete are comparable to those of quality controlled normal concrete thus suggesting reliability was not compromised with replacements of natural aggregate with RCA.