Investigation of various curing methods on the properties of red mud-calcium carbide slag-based artificial lightweight aggregate ceramsite fabricated through alkali-activated cold-bonded pelletization technology

Abstract

Industrial solid wastes red mud and calcium carbide slag are used to prepare lightweight aggregate ceramsite by cold-bonded pelletizing technology in this study. The effects of mixing water and curing method on the physical properties of ceramsite were investigated, including natural curing (in air at 20 °C), sealed curing, water curing, hot air oven curing, steam curing, and CO2 curing. The results showed that the lightweight aggregate had the lowest cylinder crush strength, the lowest apparent density, and the highest water absorption after natural curing. The highest cylinder crush strength of 8.7 MPa was obtained by steam curing at 60 °C for 12 h, which was 180.65% higher than that of natural curing because the high temperature promoted the hydration reaction thus the formation of C-(A)-S-H gel and hydrotalcite. CO2 curing at 60 °C significantly reduced the water absorption of the lightweight aggregate by 50% and by 38.03% as compared to that obtained by natural curing and steam curing at 60 °C for 12 h, respectively. During CO2 curing, the reaction between CO2 and Ca(OH)2 from the calcium carbide slag can form a dense layer of CaCO3, increasing the structural compactness and reducing the water absorption.