Evaluation of Sawdust Ash-Stabilised Lateritic Soils for Low-Cost Urban Road Construction and Sustainable Cities (Published)
The increasing demand for sustainable and affordable urban road infrastructure has heightened interest in alternative soil stabilization materials made from waste products. Lateritic soils are commonly used as subgrade materials in tropical areas; however, their high plasticity, moderate strength, and moisture sensitivity often limit their performance. This study assesses the effectiveness of sawdust ash (SDA) as an environmentally friendly stabilizing agent for lateritic soils used in low-cost urban road construction. To achieve this, lateritic soil samples were collected from selected borrow pits in Ile-Ife, Osun State, southwestern Nigeria. Standard procedures were used to perform preliminary and geotechnical tests on the natural soil samples. SDA was added to the soil samples at 3%, 6%, and 9% by weight of dry soil to identify the optimal stabilization level. The treated soil samples then underwent CBR testing. Results indicated that adding SDA reduced soil plasticity, signifying decreased swelling potential and better workability. The addition of SDA also increased CBR values, with the highest results at the optimal stabilization levels, indicating improved load-bearing capacity. This enhancement is due to pozzolanic reactions between silica-rich SDA and calcium compounds in the soil, resulting in the formation of cement-like products that strengthen the soil. The findings demonstrate that SDA is a practical and environmentally sustainable stabilizer for lateritic soils. Reusing SDA not only improves geotechnical performance but also supports waste management and reduces environmental pollution. This study advocates for the use of SDA stabilization in sustainable urban road development.
Keywords: California Bearing Ratio, road construction, sawdust ash, sustainable cities, urban development
Stabilisation of Lateritic Soil for Road Construction Using Banana Leaf Ash (Published)
In view of the need to stabilise poor lateritic soil for road construction, this study investigated the effects of banana leaf ash (content retained on British Standard sieve No. 40) on the strength characteristics of selected lateritic soils. This is with a view to ascertaining the possibility of using the referenced banana leaf ash (BLA) content to stabilise the soils, for road construction purpose. To achieve the aim of this study, two soil samples were collected from two identified borrow pits (one sample from each borrow pit – referred to as Sample A and Sample B respectively) in Ile-Ife, southwestern Nigeria. Using standard procedure, preliminary and geotechnical tests were conducted on the soil samples in their natural states. BLA was then prepared and introduced to the soils at varying proportions of 2 %, 4 % and 6 % by weight of dry soil. The Atterberg limits and California bearing ratio (CBR) were subsequently determined for the treated soils. For the natural soils, results showed that: the plasticity index values for Sample A and Sample B were 22.91 % and 26.60 % respectively; the specific gravity values were 2.71 and 2.75 respectively; the optimum moisture content (OMC) and maximum dry density (MDD) for Sample A were 26.50 % and 1.325 Mg/m3 respectively, while for Sample B the values were 19.80 % and 1.643 Mg/m3 respectively; and the CBR values were 6.85 % and 11.36 %, respectively. With the addition of BLA: plasticity index generally reduced with the lowest values (4.89 % and 6.24 % for sample A and Sample B respectively) at 6 % BLA content; the CBR steadily increased until optimum values (10.23 % and 22.73 % for Sample A and Sample B respectively) were obtained at 4 % BLA content. The study concluded that: BLA could be used to improve the properties of lateritic soils for road construction purpose; and the particle size of BLA used does not diminish the quality of BLA as a soil-stabilising agent.
Keywords: Banana leaf ash, Soil Properties, road construction, stabilisation of soil, strength characteristic