Influence of engineered self-healing systems on ASR damage development in concrete

Supplementary cementing materials (SCMs) have proven effective in minimizing alkali-silica reaction (ASR) development. In addition, crystalline admixtures (CAs) have been identified as potential solutions to counteract damage in concrete. However, limited data on this topic is available in the literature. This study investigates the impact of CA on concrete damage and is divided into two phases: 1) the effectiveness of CA in self-healing cracks and restoring the mechanical properties of mechanically damaged concrete; 2) it explores concrete mixtures incorporating a wide range of binder compositions (i.e., general use type cement, silica fume, fly ash, slag and Metakaolin) and chemical admixtures (i.e., commercially available CAs and modified versions) in conditions enabling ASR development. Both phases involve microscopic/mechanical analyses to assess the effects of CA on damage, and comparisons with concrete mixtures without CAs are made. The results reveal that CA enhanced the self-healing of cracks up to 82 % of cracks in cement paste (115 % higher values than concrete mixtures without CA) and restored 69 % of compressive strength. Furthermore, although CAs could change the damage mechanism of ASR, they did not "safely" mitigate it. However, combining SCMs and CAs effectively reduces ASR-induced expansion.