Lightweight aggregate and concrete production from waste of mining operation

Reza Hedayat

hedayat@mines.edu

Lightweight aggregates (LWAs) have a low density while maintaining adequate mechanical properties, making them exceptionally suitable for a range of civil and construction applications. The usage of LWAs in concrete is increasing, as many of their properties, including unit weight, internal curing, insulating coefficient, and sound dampening qualities, are better than those of natural normal-weight aggregates. Also, natural normal- and light-weight aggregates are limited in supply and their consumption adversely affects the environment. There is an increasing interest in producing LWAs through conversion of other waste products such as mine tailings, which are the finely ground residue from the mining operation after the economically recoverable commodity is extracted from the ore materials. The storage and handling of mine tailings pose significant economic and environmental problems and the reuse of mine tailings in high-volume applications such as construction materials provides golden opportunities for tailings reduction. Therefore, further development of technologies to produce LWAs from mine tailings will significantly benefit several advanced industries such as “infrastructure engineering” by production of sustainable and valuable construction materials and “energy and natural resources” by utilization of mining waste and reduction of waste deposition. Our research team at Colorado School of Mines has successfully developed a laboratory-based technique for utilization of mine tailings for production of LWAs for use in construction industry and has achieved the “proof of principle” milestone. The technique involves the creation of LWAs through alkaline activation of mine tailings, using a pan pelletizer where an activator is sprayed on the mine tailings to dissolve the aluminosilicates, form a gel, and bind the tailings to form spherical granules of LWAs. This technique is more energy efficient than other commonly used granulation techniques that require high-temperature sintering and/or cement-based palletization. We have successfully examined the suitability of our alkali-activation technique for seven different sources of mine tailings, mainly collected from mining operations in Peru in production of LWAs with satisfactory physical properties per ASTM standards. We have the expertise and state-of-the-art facilities for this research work and with the help of this UG scholar, we plan to develop the technology further, focusing on the tailings collected from Colorado’s storage facilities. Although LWA production using mine tailings with reactive aluminosilicates is a proven technology as shown through our proof of principle research work, the use of the produced LWAs in lightweight concrete and mortar and its influences on the properties of concrete such as strength, durability, and performance have not yet been explored, highlighting an important gap that needs to be filled prior to commercialization of this technology.

Grand Challenge: Restore and improve urban infrastructure.

Asadizadeh, M., Clements, C., Hedayat, A., Tunstall, L., et al. (2023). The effect of class F fly ash on the geopolymerization and compressive strength of lightweight aggregates made from alkali-activated mine tailings. Construction and Building Materials, 395, 132275. Zhang, N., Hedayat, A., Perera-Mercado, Y., et al. (2022). Including Class F Fly Ash to Improve the Geopolymerization Effects and the Compressive Strength of Mine Tailings–Based Geopolymer. Journal of Materials in Civil Engineering, 34(11), 04022313.

Dr. Reza Hedayat, hedayat@mines.edu Dr. Mostafa Asadizadeh, masadizadeh@mines.edu