One-Part Geopolymer for Stabilising Crushed Rock Road Base Material

Geopolymers have attracted wide attention as effective soil stabilisers, presenting significant potential for several geotechnical engineering applications. These binders offer environmental benefits by utilising abandoned aluminosilicate industrial by-products, such as fly ash and slag, through mixing with an alkaline solution. In addition, they also decrease dependency on conventional Ordinary Portland Cement (OPC), which is identified with substantial artificial greenhouse gas emissions and high energy consumption during manufacture. However, the practical utilisation of geopolymers for the stabilisation of road materials is hindered by the intricate preparation process, which necessitates precise control over the proportions of the ingredients to achieve the required mechanical properties. This complexity becomes more pronounced when compared to the relatively simple method of using conventional cement, which requires fewer safety precautions while mixing with soil. This study investigates the development of a One-Part Geopolymer (OPG) powder, specifically formulated for the stabilisation of a Crushed Rock Base (CRB) material used for road construction. The optimal blend of OPG powder, comprising fly ash, slag and sodium metasilicate, is identified by assessing the monotonic and dynamic mechanical performances of the treated CRB compacted at the optimum moisture content using Unconfined Compressive Strength (UCS) and Repeated Load Triaxial (RLT) tests. The results of the study indicate that enhancing the strength performance of the OPG-treated CRB requires the calibration of the sodium oxide (Na2O) content in the alkaline activator with the total binder. It was also found that increasing the OPG content from 1% to 3% significantly enhances both the uniaxial strength and resilient modulus of the treated CRB, while simultaneously reducing the permanent deformation. Notably, the CRB specimens stabilised with 2% OPG exhibit mechanical properties comparable to those of bound Portland cemented materials.