Evaluation of the eco-friendly contribution of cashew leaf ash in sustainable lateritic soil road pavement construction

Identifying suitable lateritic soil (LS) for road pavement construction in high clay content regions is challenging and requires improvement for effective use. This study assessed the eco-friendly use of cashew leaf ash (CLA) to enhance LS for sustainable road construction. CLA was added in concentrations of 0 %, 2 %, 4 %, 6 %, 8 %, and 10 % by weight of the dry soil. Various tests, including Atterberg limits (liquid limit, plastic limit, plasticity index and linear shrinkage), compaction characteristics, California Bearing Ratio (CBR), and unconfined compressive strength (UCS), were conducted on both untreated and CLA-stabilized soil. Results showed that increasing CLA content reduced the Atterberg limits up to 4 % CLA content. The optimal compaction characteristics were observed at 6 % CLA content. At this concentration, the CBR values significantly improved, though they remained below the 80 % and 180 % thresholds required for base materials and cement-stabilized materials, respectively. UCS values also improved with 6 % CLA at various curing periods but did not satisfy the 1710 kN/m² condition for acceptable soil stabilization and modification with OPC. However, the UCS values at 28 days were within the range suitable for sub-base use. Regression analysis indicated robust connections amid experimented and predicted strength indices. It is recommended to use lateritic soil treated with 6 % CLA and compacted at 28 days curing age for sub-base in flexible pavement construction. CLA can also be used as an additive in cement stabilization for low traffic road surfaces.