Systematic Evaluation of Crushed Waste Glass in Shotcrete: From Laboratory Batching to Field Spraying Trial

• Multi-scale evaluation of shotcrete with up to 50% crushed waste glass (CWG). • CWG does not compromise mechanical performance or durability. • ASR expansion acceptable up to 25% CWG replacement. • Field trial confirms feasibility of CWG in sustainable shotcrete production. Crushed waste glass (CWG) offers a sustainable alternative to natural sand, addressing critical issues of sand depletion and promoting circular economy principles in underground construction materials. This study systematically evaluates the effects of CWG replacement (up to 50% by mass) on shotcrete performance through multi-scale laboratory tests and a full-scale field spraying trial. Despite prior studies on recycled glass in concrete, knowledge gaps remain regarding its influence on early-age shotcrete behaviour, long-term durability and field-scale applicability, which this study aims to address. Laboratory results show that CWG improves fresh mix flowability and reduces water demand. Similar mechanical performance and long-term creep were observed with CWG inclusion. Durability tests, including alkali-silica reaction (ASR), sulphate resistance and chloride ingress, demonstrates enhanced performance with reduced sulphate expansion limited to 0.2% and chloride penetration with approximately 65% reduction at 50% CWG mix compared to the reference at 91-day age. While ASR results showed divergent trends by test method, suggesting its test-method sensitivity, CWG up to 25% remains within comparable expansion with the reference, ranging between 0.01% to 0.013% at shotcrete scale. The field trial confirms that 25% CWG mix maintains pumpability, minimises rebound and achieves greater early-age strength than control mix, with no notable difference in cracking observed within the long-term monitoring. The results validate CWG as an effective and sustainable fine aggregate replacement in shotcrete, supporting its adoption for underground infrastructure application.