The use of concrete aggregate in the production of new concrete

Abstract

As climate change proceeds, a frugal lifestyle becomes increasingly important for the wellbeing of the Earth’s ecosystems. The reasonable use of nature’s raw materials supports the circular economy, which lessens the environmental burden. Construction and demolition waste is a major waste source within cities, and therefore more valuable reuse of this waste is needed. Since the concrete industry is one of the most polluting industries globally, the reuse of raw materials in concrete production would not only diminish urban waste but also the emissions of the concrete industry itself. The aim of the thesis was to find out how the compressive strength of concrete changes if quarried stone aggregate used in concrete production is replaced by concrete aggregate. For the study, leftover concrete aggregate from concrete production was prepared by sieving, and particle size distribution was calculated. Concrete test pieces were then made in a laboratory. Finally, compressive strength tests were conducted on concrete test pieces to gain quantitative data about the potential change in compressive strength when using recycled concrete aggregate. The results of the compressive strength tests show that the compressive strength of concrete decreases by 6–7.3 MPa when using concrete aggregate instead of natural aggregate in the production of new concrete. It has been estimated that this difference in strength can be compensated by using a plasticizer. Therefore, the use of concrete aggregate in the production of new concrete is possible. To improve the reuse of concrete aggregate, the standard SFS-EN 206 (2014) should be updated to allow the use of concrete aggregate with a 100 % replacement ratio. Mikkeli Development Miksei Ltd. can utilise the results of this study to advance the use of concrete aggregate in the production of new concrete. Further research is needed to find ways to improve the technical properties of recycled concrete aggregate and to examine the effect of fine recycled concrete aggregate on the quality of new concrete.