Ceramics-Silikáty

This study investigates the influence of fluidized bed combustion (FBC) ash on alkali–silica reaction (ASR). In particular, the effects of CaO content and ash fineness on the mitigation efficiency of ASR expansion in mortar specimens were evaluated. Four types of FBC ash with different CaO contents were used as partial ordinary Portland cement (OPC) replacement (30 wt.%). Furthermore, one selected ash was ground for different time durations in order to assess the effect of fineness. The accelerated mortar specimen test was performed according to ASTM C1260. After the expansion measurements had been completed, mechanical properties were determined and microstructural analysis was carried out using scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDX). The results showed that all tested FBC ashes reduced ASR expansion compared to the reference mixture containing 100% OPC. Increasing CaO content in FBC ash led to a decrease in ASR mitigation efficiency. Grinding of the ash improved its mitigating effect due to increased fineness and enhanced pozzolanic reactivity. The presence of ASR gel was confirmed by SEM/EDX analysis. No significant negative influence of ASR on mechanical properties was observed.