Kaolin stabilisation by utilising ground granulated blast slag for carbon dioxide reduction

Abstract

The aim of this study is to identify the effect of ground granulated blast furnaces slag (GGBS) in stabilising kaolin using the accelerated carbonation process while sequestering CO2 to reduce its level in the atmosphere. The effects of incorporating GGBS and carbonated GGBS on mechanical properties of soil and the underlying mechanisms of stabilisation are investigated by carrying out physical characterisations, strength test and microstructure analysis (i.e., Field Emission Scanning Electron Microscope, X-Ray Diffraction). In addition, thermogravimetric analysis (TGA) and Acid Digestion method were used to quantify the CO2 that has been sequester in the soil. The results show that GGBS was found to be a good candidate for kaolin stabilisation (under ambient condition) in which the strength keeps increasing with time, and as the content of GGBS increases. 20% and 25% GGBS-kaolin mixtures strength have exceeded the value requires for the subgrade layer at 7 curing days. The highest strength recorded was for 25% GGBS-kaolin mixture at 28 days curing as the strength reached 8.4 MPa. For the mineral carbonation process, the outcome indicates that the strength rises as the carbonation period rises, and a substantial strength gain was noted during the first hour of the carbonation phase. Likewise, unconfined compressive strength (UCS) rises as the CO2 pressure rises from 100 kPa to 200 kPa. Acid digestion method and TGA shows that the GGBS-kaolin mixtures sequester between 4.5 to 5% CO2 from its original dry weight. XRD analysis shows no peaks were observed for the magnesium-carbonated products. On the other hand, a single peak of calcium-carbonated products was seen in the diffractogram of the carbonated GGBS-kaolin mixture. Field emission scanning electron microscopy (FESEM) analysis for carbonated samples shows a needle-like structures seen on the surface of the kaolin particles which is Aragonite (CaCO3). It could be concluded that augmentation of the strength is due to carbonated calcium and magnesium products which stuff the soil voids.