Unveiling the performance evolution and reaction mechanisms of alkali-activated incineration bottom ash-cement composite systems

To address the low resource utilization efficiency of incineration bottom ash (IBA) caused by its insufficient reactivity, this study systematically investigates the influence mechanisms of alkali activation modification on ash (IBA)–cement composite systems. IBA was activated using NaOH and Na₂SiO₃ as alkali activators, with particular emphasis on the enhancement of mechanical properties and the evolution of microstructure under different activator ratios. Results indicate that when the Na₂O content concentration in the alkali activator is 0.8 %, the latent reactivity of IBA can be effectively activated, promoting the formation of high-strength gel in the hydration products, resulting in a 25 % increase in 28-day compressive strength compared to the control group. Notably, when the Na₂O content increases to 1.6 %, excessive alkali not only disrupts the normal hydration process but also significantly intensifies the alkali-silica reaction (ASR), leading to severe degradation of specimen performance. In addition, it was observed that Na₂SiO₃ accelerates specimen hardening, necessitating strict control of its dosage within the range of 0.7–1.3 %. Excessive dosage may lead to overly rapid hardening, severely hindering the complete progression of hydration, while dosages below 0.7 % result in suboptimal performance improvement.