A comparative experimental investigation into the chemical stabilisation of sandstone aggregates using cement and styrene-butadiene copolymer latex for road sub-base construction

For granular road sub-base constructed using local aggregates of marginal quality such as sandstone, chemical stabilisation using cement or polymer has been found to improve the key mechanical properties of pavement. There is a knowledge gap on the strength development of sandstone stabilised using only non-ionic styrene-butadiene (SB) polymer for use as a road sub-base. Previous comparative experimental investigations of the relative strength development of sandstone of marginal quality stabilised with non-ionic SB polymer and cement, individually, have also been limited. Therefore, this paper aims to provide an experimental investigation of the relative strength development of sandstone aggregate sub-base of marginal quality stabilised with Portland composite cement (PCC), ordinary Portland cement (OPC) and SB latex copolymer (or polymer), individually. The samples were prepared with different gravel-to-sand (G:S) ratios of 2.1, 1.2 and 0.4, and subsequently, some samples were treated with 3% and 5% cement contents and some others with 0.5–2% polymer contents. Samples were compacted and cured for 3 and 7 days under dry and wet conditions before measuring their unconfined compressive strength (UCS) and indirect tensile strength (ITS). Samples were compacted and cured for 4 days under unsoaked and soaked curing conditions before measuring their California bearing ratio (CBR). It was found for both cement-stabilised and polymer-stabilised samples that the higher the G:S ratio, the higher the UCS, but this trend was steeper for polymer-stabilised samples. For cement stabilisation, 5% was the optimum cement content that provided the sub-base with the highest UCS and CBR values. For polymer stabilisation, 1% was the optimum polymer content that provided the sub-base with the highest UCS and CBR values. The UCS of OPC-stabilised samples was almost 1.15 times that of PCC-stabilised samples for the same G:S ratio, cement content and curing condition. Despite the potential environmental benefit of polymer stabilisation for pavement aggregates, when used individually, cement stabilisation of the sandstone aggregates was able to achieve significantly faster strength development and resulted in generally higher strength properties than polymer stabilisation.