A sorting method to value recycled concrete

Abstract

The purpose of this paper is to propose a sorting platform to increase the quality of recycled aggregates through the supplementary use of mineral processing techniques and additional sorting. The difficulty of liberation is discussed, and the methodology currently used in mineral processing is proposed. Jigs, hydrocyclones and sensor-based sorting are considered to have good performance in the sorting of adequately recycled aggregates.The new perspectives on sorting and liberation for recycling aggregates are discussed. The new process is presented based on the current process in recycling platforms, with supplementary sorting of the recycled concrete. The gain in density and the reduction in water absorption are studied. The relation between the water content and the density of aggregates is analysed for three quality levels of recycled aggregates.The gain in density and the reduction in water absorption were linked to the aggregate replacement rates. The reduction in transport and discharge costs due to the increased aggregate quality was linked to the aggregate replacement rate and distance to quarry. In our study, replacing a lower-quality aggregate with another of medium quality leads to an expected density gain of approximately 4%. Conversely, if replaced by superior quality aggregate, the expected gain will be 8.4%. As a consequence, a 34% reduction in water absorption could also be obtained.The cost reduction is exponential with the substitution rate of recycled materials. There is a decrease in transport costs if the quality of recycled aggregates increases. Conversely, if the reduction in transport costs when the quality of recycled aggregates increases is considered, the distance between the demolition site and quarry is not important.