Chemical stabilisation of sandstone road aggregate layers: A literature review

The increasing demand for aggregates for road construction and development has led to increased exploitation of mineral resources, resulting in their scarcity. This has an adverse effect on the environment as well as the cost of road development, especially when local aggregates are of poor quality and not suitable for road construction, requiring long-distance transportation or importation from another country. An approach that could be more cost-effective is the chemical stabilisation of locally available weak aggregates such as sandstone. This paper reviewed the most commonly used traditional and non-traditional additives for the stabilisation of road aggregate layers. The literature review focused on the type of soil for which each additive is best suited, the binding mechanism involved and the advantages and limitations of using each additive for soil stabilisation. It was found that the majority of the existing literature had focused on the chemical stabilisation of conventional road materials and demolition and waste aggregates for use in pavement base and/or subbase layers, but only a few looked into sandstone chemical stabilisation. Sandstone aggregate investigations have been limited to either cement and/or polymer stabilisation for road aggregate layers or cement concrete mixtures for building construction. As a result, this paper revealed a knowledge gap regarding the strength development of sandstone road aggregate layers after stabilisation with fly ash and lime, either separately or in combination, which is predominantly measured in terms of the unconfined compressive strength, indirect tensile strength, and California Bearing Ratio. Future research to address the gap in knowledge will provide an insight into a potentially cost-effective alternative and sustainable road construction by utilising locally available sandstone aggregate and fly ash waste material.