Geotechnical characteristics of lateritic clay admixed with biomass silica stabiliser

This paper examines the effectiveness of using varying proportion (2%, 4% and 6% by dry weight of soil) of a newly formulated biomass silica soil stabiliser (BSS) on tropical lateritic clay which has deleterious effects on construction materials due to its high amounts of SiO2 and Fe2O3. A series of laboratory experiment testing methods: i.e. particle size distribution, Atterberg Limits, linear shrinkage, pH value, compaction, California Bearing Ratio, unconfined compression test, and cyclic load triaxial test were conducted in accordance to BS1377:1990 and AASHTO T307-99:2003 to examine the geotechnical properties of the BSS structured lateritic clay subjected to 0, 7, 14 and 28 curing days. Physicochemical tests such as X-ray fluorescence (XRF), X-ray diffraction (XRD) and field-emission scanning electron microscope (FESEM) were conducted to further support the mineralogical composition and microstructure evidence of the structured soil and substantiate the interpretation of the mechanical strength data. The test results reveal that the notable changes in the properties and behavior of structured lateritic clay was governed by the BSS proportion and curing period. There is an immediate enhancement in the geotechnical properties of the 2% BSS structured lateritic clay, altering soil type from CH to MH before curing begin. The unconfined compressive test results indicate a distinct effectiveness in stabilizing lateritic clay, from 400 kPa to 3675 kPa for 6% BSS structured lateritic clay cured to 28 days. Both soaked and unsoaked California Bearing Ratio (CBR) values were 12.4 and 5.8 folds higher than that of the virgin lateritic clay. The cyclic load triaxial test reveals that the resilient modulus, M-R of the structured soil was significantly increased. For full-scale applications, the association between the mechanical properties and linear shrinkage test results deduce that the optimum proportion of BSS required for an effective stabilisation performance is 6%. Finally, the mechanisms of the microstructural changes in the stabilisation process were mainly attributed to the agglomeration and aggregation of the cemented particle through composition of calcium silicate hydrate cementitious products evidenced in the physicochemical tests.