Preparation and characteristics of cold-bonded lightweight aggregates by recycling mine tailings and industrial waste residues based-binder

Artificial lightweight aggregates (LWAs) as a substitute for natural aggregates (river sand and broken stone) have been used in the building materials field. In this study, to promote the reutilization of industrial waste residues (IWRs), the feasibility of manufacturing LWAs from mine tailings (MTs) and IWRs based-binder was investigated by applying cold-bonded pelletization technique. A series of density, water content, water absorption, crushing strength, cylinder compression strength, and microanalysis tests were conducted to evaluate the effects of binder content, particle size, and gradation on physical, mechanical, and microstructure performance. Results indicate that as the binder dosage increases from 10 to 25 wt.%, the water content (14.72∼10.68%) and 1-hour water absorption rate (14.29∼13.24%) decrease, but the bulk density (1066∼1112 kg·m-3) increases for cold-bonded tailings lightweight aggregates (CBTLWAs). As the diameter ranges from 4 to 20 mm, the peak load of individual CBTLWAs pellet increases in accorded with power function, while the crushing strength decreases correspondingly. When Talbot coefficient increases from n=0.2 to 0.5, the cylinder compression strength initially increases and then decreases until n=0.8. The highest values are 6.17, 6.88, 9.27, 10.90 MPa in 28-day CBTLWAs when n is 0.5. Under the liquid bridging force of capillary water and the friction of pelletizer disc, MTs and IWRs-based binder are conglobated into individual pellets. With the elapse of curing time, the pellets of CBTLWAs are further solidified by the hydration products as the bonding medium. Dense microstructure forms inside CBTLWAs with the total porosity of 30.82%∼35.99%. The findings are expected to provide a guidance for LWAs production by recycling mine and industrial solid wastes.