High quality recycled sand from mixed CDW – is that possible?

Abstract

Sand scarcity is occurring in different countries all over the world as highlighted by the United Nations Environmental Program, therefore, the development of sustainable alternative materials is vital. This paper presents the potential of mineral processing to produce high quality recycled sand by comminuting mixed CDW (Construction and Demolition Waste) into fine fraction at an industrial plant. This methodology represents a change in recycling strategies that proved to be effective for attaining high-quality products that will contribute to enlarge recycled sand market, thus moving toward a circular economy. Samples of mixed CDW were collected from different sources, with different compositions and locations. Primary and secondary crushing were conducted by a jaw crusher, tertiary crushing in a cone crusher and then the material was milled in a rotor impact mill in closed circuit, with 2.0 mm size screening followed by an air classifier to remove the fines (below 0.074 mm). The crushed sand obtained, composed mainly by quartz and feldspar and particles shaped like natural sand, high density (2.71 g/cm3), low water absorption (4.6%) and represents 80% in mass of the recovered fraction. The filler fraction produced, 20% in mass, has a notably higher content of calcium oxide due to the content of cement paste. The sand obtained is particularly distinct from the usually recycled sand generated as a by-product (or mostly tailing), characterized by irregular shape, rough surface and high-water absorption. Appropriate processing is crucial for increasing the waste recycling rates and mitigate the sand scarcity in many world regions.

Keywords

• Recycled sand
• Mixed CDW
• Waste processing
• Construction and demolition waste