| Summary: | The presence of marine clay underlying foundation has been responsible for failure in several geotechnical structures and chemical stabilisation is the usual practice to improve the strength of soils. Recently, non-traditional additives are extensively used to solve this problem and their effects on geotechnical properties of soils have been reported by many researchers. However, publications on the fundamental microstructural behaviour of non-traditional additives in treating marine clay soils and their influence on the engineering behaviour are limited. Therefore, this research aimed at determining the stabilisation mechanism and the performance of marine clay soil mixed with two types of non-traditional additives, namely calcium-based powder stabiliser (SH-85) and sodium silicate-based liquid stabilizer (TX-85). Microstructural study from different spectroscopic and microscopic techniques such as X-ray Diffractometry (XRD), Energy-Dispersive X-ray Spectrometry (EDAX), Scanning Electron Microscopy (SEM), Thermal Gravimetric Analysis (TGA) and pore size distribution had been conducted to elucidate the stabilisation mechanism. Unconfined compressive test, oedometer consolidation test and consolidated undrained triaxial compression test were conducted to assess the engineering properties of the stabilised soil. In addition, strip footing model tests were conducted to determine the performance of stabilised clay soils and the results were compared with simulation using PLAXIS 2D finite element. The laboratory tests showed that the addition of 12% SH-85 at early 7 days curing period had increased the compressive strength of treated marine clay by about 42 times while the addition of 6% TX-85 with similar curing period had increased the compressive strength of treated marine clay by about 3.6 times. The results of the microstructural tests indicated the formation of new gel products in the mixtures, which were identified as calcium silicate hydrate (CSH) and sodium aluminosilicate hydrate (NASH) for soils treated with SH-85 and TX-85, respectively. SEM images illustrated the formation of new cementitious compounds (CSH and NASH) which were shown within the pore spaces, resulting in the reduction of radius of pore spaces. In comparison to the untreated soil, the results of the physical model tests showed that the bearing capacity of strip footing on the treated soil at 7 days curing period increased significantly while the settlement reduced. In short, the selected additive had successfully increased the strength of marine clay at early period, thus the usage of selected non-traditional additives was considered as cost effective for geotechnical project.
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