Impact of solid sodium activators on recycled glass columns stabilized with one-part geopolymers

Sand columns require substantial quantities of natural sand, which raises environmental concerns. Recycled glass (RG) offers an eco-friendly alternative, yet its application in ground improvement remains largely underexplored. Cement is commonly used as a binder to enhance the strength and stiffness of geomaterials; however, cement production contributes to CO 2 emissions. One-part geopolymers offer a sustainable alternative to cement. This research investigated RG columns stabilized with one-part geopolymers activated by solid sodium hydroxide (NaOH) and anhydrous sodium metasilicate (Na 2 SiO 3 ). Curing was conducted at room temperature and at 40 °C to simulate summer temperatures. Laboratory investigations included particle size distribution, organic content, modified compaction, California bearing ratio, unconfined compression strength (UCS), and repeated load triaxial tests. Two types of precursors were studied: slag (S) and fly ash (FA). All S blends exceeded the UCS thresholds of 1.035 MPa, with UCS values from 2.04 MPa to 27.06 MPa. The FA blend (RG+30FA+10Na 2 SiO 3 ) met the UCS requirements at ambient temperature (1.47 MPa). Increasing curing temperature improved the UCS values for all blends, with Na 2 SiO 3 -activated blends outperforming NaOH activators, regardless of the precursor. Under cyclic loading, RG columns with S blends remained stable with low permanent strain (0.13% for NaOH and 0.11% for Na 2 SiO 3 blend). RG columns with FA geopolymers activated by Na 2 SiO 3 displayed increased strain responses, but permanent strain was minimal (0.493%). This research highlights the potential of one-part geopolymers, particularly Na 2 SiO 3 -activated systems, as a sustainable and cost-effective solution for improving RG columns' performance in soft soils.