Despite ongoing efforts to prevent the damaging effects of alkali-silica reaction (ASR) in concrete structures, this phenomenon still exists and causes significant degradation. This study aims to investigate the role of various deicing agents in provoking ASR by examining volume expansion, cracks, and microstructure of mortar and concrete containing aggregates identified as non-reactive by standard ASR test methods. To achieve this, the concrete specimens undergo simulated operating conditions testing to induce ASR expansion, with an external supply of alkali from chloride- and formate-based deicers. The findings suggest that the configuration and concentration of the deicing agent used, as well as the mineral composition of the aggregate that was previously identified as non-reactive, can significantly impact the expansion and damage caused by ASR. The results indicate that existing methods for testing aggregates for ASR may have limitations when formate-based agents are used.

Results of experimental investigation on the mitigation of alkali–silica reaction (ASR) by low-grade calcined clay are presented. Domestic clay with an Al₂O₃ content equal to 26% and SiO₂—58% was used. The calcination temperatures were as follows: 650 °C, 750 °C, 850 °C and 950 °C, which were chosen much more widely than presented in previous studies. Pozzolanity of the raw and calcined clay was determined with the Fratini test. The performance of calcined clay to mitigate ASR was evaluated according to ASTM C1567 using reactive aggregates. A control mortar mixture was prepared with 100% Portland cement (Na₂O_eq = 1.12%) as a binder with reactive aggregate, and test mixtures were made with 10% and 20% of calcined clay as a cement replacement. The microstructure of the specimens was observed on the polished sections using scanning electron microscope (SEM) operated in backscattered mode (BSE). The results of expansion of mortar bars with reactive aggregate showed that replacing cement with calcined clay reduced the expansion of the mortar bars. The greater the cement replacement, the better results in terms of ASR mitigation. However, the influence of the calcination temperature was not as clear. The opposite trend was found with the use of 10% or 20% calcined clay.