Controllable setting time of alkali-activated materials incorporating sewage sludge ash and GGBS: The role of retarders

Utilizing sewage sludge ash (SSA) for alkali-activated materials offers an environmentally friendly approach to solid waste management. However, the rapid setting issue limits the widespread use of sludge ash-based materials (SAAM). This study aims to control the setting time of SAAM by employing retarders. The impact of sucrose and glucose on setting time, fluidity, and compressive strength was examined. XRD, FTIR, SEM, and BSE techniques were used to investigate the mechanisms of retarder action. Additionally, a sustainability assessment was conducted. The results show that both sucrose and glucose significantly extend the setting time of SAAM. Optimal control can be achieved by adjusting the retarder dosage. Microscopic tests reveal that retarders hinder the hydration process, impeding initial hardening. Furthermore, compared to adjusting activator parameters, retarder use leads to lower CO₂ emissions and energy consumption, enhancing environmental sustainability.