Abstract
Lime stabilisation is one of the traditional methods of improving the engineering properties of lateritic soils for use as subgrade and foundation materials for the construction of road pavements and highway embankments. Understanding the mechanical performance of lime-stabilised lateritic subgrades in terms of their durability under continuous water ingress will improve environmental sustainability by conserving scarce natural resources and reducing the environmental impacts of repair and replacement of pavements. However, there are several conflicting reports on the durability of lime-stabilised soils subjected to continuous water ingress and harsh environmental conditions. Therefore, this paper evaluates the influence of leaching on the physicochemical behaviour and durability of lime-stabilised lateritic soil under continuous water ingress, simulating the typical experience in a tropical environment. Variations in the strength and durability of the lateritic soil at various lime contents (0, 2.5, 5, 7.5, 10, 15, and 20 wt.%) and soaking periods (3, 7, 14 and 28 days) were evaluated by performing the California bearing ratio tests before and after subjecting the lime-lateritic soil (LLS) samples to continuous leaching using two modified leaching cells. Furthermore, physicochemical analysis was performed to assess the variation of cation concentrations and changes in the physical properties of the pore fluid as the leaching time progressed from 3 to 28 days. The results show that the minimum strength reduction index of the soil corresponds to its lime stabilisation optimum (LSO). Electrical conductivity decreased monotonically and almost uniformly with an increase in leaching time, irrespective of lime content. So, too, was calcium concentration and to a lesser degree for pH and potassium concentration. Adverse changes in the physicochemical behaviour of the LLS samples occurred at lime contents below and slightly above the optimum lime content of the soil. Whereas permanent pozzolanic reactions occurred at lime contents above the LSO and thus resulted in a 45-fold increase in strength and durability. The results are significant for reducing the detrimental effect of the leaching-induced deterioration of flexible pavements founded on tropical floodplains.
Highlights
The availability of sustainable civil infrastructure systems, such as transportation, water and wastewater, electric power, and communications, is essential for the growth and development of urban areas
There was an initial reduction in the liquid limit (LL) and plasticity index (PI) of the soil as lime content increased from 0% to 5% (Figure 4a)
For silica-rich residual soils, further increase in liquid limit is usually triggered by the enhancement of the cation exchange capacity, due to the highly alkaline environment produced by the dissolution of Ca(OH)2, which increases the pH of the pore fluid [74]
Summary
The availability of sustainable civil infrastructure systems, such as transportation, water and wastewater, electric power, and communications, is essential for the growth and development of urban areas. Numerous regional and municipal infrastructure projects founded on floodplains and reclaimed lands have failed as a result of the poor engineering properties of the materials within these environments, in addition to the effects of intense precipitation and other harsh environmental conditions [1]. These engineering failures have been attributed to the high cost of excavating and replacing problematic soils with suitable materials and the strict legislative rules that govern the utilisation of these scarce natural resources for earthworks construction purposes. The main distinctive feature of lateritic soils is the high amount of sesquioxides of iron and aluminium, with kaolinite being the dominant clay mineral [14,15]
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