Feasibility and mechanism of high alumina cement-modified chlorine saline soil as subgrade material

Abstract

Soil salinization is a serious problem during ground improvement and foundation construction around the coastal region. This study used high alumina cement (HAC) as a soil stabilisation agent to modify the coastal chlorine saline soil as roadbed backfilling materials. In addition, Ordinary Portland cement (OPC), slaked lime (SL) and fly ash (FA) were used to better the understanding of the chlorine fixation and roadbed performance. The microstructures of different hydration products were investigated through the utilization of the X-ray diffraction and scanning electron microscope equipped with an energy dispersion spectrometer. The HAC-SL-modified soil depicts that the aluminium and calcium phases are beneficial to the formation of Friedel’s salt and hydration products. The optimal chlorine fixation is approximately 20.5% at 6% HAC-SL incorporation (3% of HAC and 3% SL). At the early stage of curing, the strength of the HAC-treated soil is high. However, with a prolonged curing period, there is a slight decrease in the strength because the porosity will increase during the transformation of metastable CAH10 and C2AH8 into stable and dense C3AH6. This evolution can be prevented by incorporating SL to enrich calcium silicate hydrate (C-S-H) and calcium aluminate hydrate (C-A-H). Furthermore, it is of key importance to mention that HAC reaction is quick, therefore, the compaction should be undertaken instantly to ensure the road performance.