No abstract

The transportation infrastructure, including low-volume roads in some regions, needs to be constructed on weak ground, implying the necessity of soil stabilization. Untreated and cement-treated lateritic soil for low-volume road suitability were studied based on Malaysian standards. A series of unconfined compressive strength (UCS) tests was performed for four cement doses (3%, 6%, 9%, 12%) for different curing times. According to Malaysian standards, the study suggested 6% cement and 7 days curing time as the optimum cement dosage and curing time, respectively, based on their 0.8 MPa UCS values. The durability test indicated that the specimens treated with 3% cement collapsed directly upon soaking in water. Although the UCS of 6% cement-treated specimens decreased against wetting–drying (WD) cycles, the minimum threshold based on Malaysian standards was still maintained against 15 WD cycles. On the contrary, the durability of specimens treated with 9% and 12% cement represented a UCS increase against WD cycles. FESEM results indicated the formation of calcium aluminate hydrate (CAH), calcium silicate hydrate (CSH), and calcium aluminosilicate hydrate (CASH) as well as shrinking of pore size when untreated soil was mixed with cement. The formation of gels (CAH, CSH, CASH) and decreasing pore size could be clarified by EDX results in which the increase in cement content increased calcium.

Constructing structures on lateritic soil is challenging in geotechnical engineering due to the various physical and geotechnical characteristics. Many studies investigated different stabiliser materials to strengthen the geotechnical parameters of lateritic soil. This study used activated carbon and coir fibre (ACF) to stabilise lateritic soils as an environmentally friendly binder. Experiments including the unconfined compressive strength (UCS) test and the direct shear test (DST) are performed to investigate the mechanical properties of ACF-stabilised soil for different percentages of activated carbon (AC). Before and after ACF stabilisation, microstructural characterisations of soil samples were performed using field emission scanning electron microscopy (FESEM) and surface-area analysis (BET). The experimental results demonstrate that 3% ACF can considerably enhance the compressive strength, while 2% ACF significantly improves the shear strength, of lateritic soil. Accordant to the UCS results, using fibre in AC-stabilised soil improves post-peak behaviour and residual strength. Moreover, 2% ACF can significantly improve shear strength by creating an interlocking matrix among AC, soil particles, and fibre. The microstructural characterisation based on the findings obtained by FESEM and BET analysis confirms that AC particles fill soil voids. AC restrains the soil movement when exposed to external stresses. In addition, the formation of gel in the stabilised soil matrix binds the soil particles, increasing the strength of the ACF-stabilised soil in comparison with untreated soil.