Recent advances in artificial aggregate production

Artificial aggregates (AAs) are man-made construction material, and the properties greatly depend on its manufacturing process (e.g. granulation and hardening) and the raw materials (usually different source of wastes) used. This paper reviews the granulation process and suitable raw materials for each hardening method. Hardening methods including sintering, cold-bonding, accelerated carbonation and alkaline activation can significantly impact the final properties of the produced AAs. In general, finer material fractions are required for granulation to increase the pelletization efficiency and strength of AAs. Among the hardening methods, sintering usually gives a better physical and mechanical properties of AAs with a condition that SiO2/Pflux ratio of raw materials used should exceed 2, and (SiO2 thorn Al2O3)/ Pflux ratio of between 3.5 and 10. The cold-bonded method requires hydraulic raw materials and is restricted by a longer curing time, but this can be solved by introducing autoclaving or alkaline activation approaches to accelerate the strength gain. Post curing of AAs under a strongly alkaline solution can also effectively reduce the water absorption of aggregate by nearly 90%. The accelerated carbonation technique seems to be a green and more sustainable hardening method, as it can turn less valuable waste into strength bearing calcite and permanently store the waste CO2 through mineral carbonation. In terms of leachability, sintering can stabilize most heavy metals, while other hardening methods such as cold bonding and carbonation are only effective for stabilizing certain heavy metals. (c) 2020 Elsevier Ltd. All rights reserved.

Automated summary

Artificial aggregates are man-made construction material whose properties greatly depend on the manufacturing process and raw materials used. Different hardening methods like sintering, cold bonding, accelerated carbonation, and alkaline activation can significantly impact the final properties of the aggregates. Finer material fractions are required for granulation to increase pelletization efficiency and strength, with sintering generally yielding better physical and mechanical properties.