A Fundamental Study on the Assessment of Fly Ash Addition and Repair Material Effect on the Mitigation of Alkali Silica Reaction in Concrete

The investigation reports from repaired concrete bridge structures in Japan showed some remarks. The use of acrylic-based surface coating and the silicon-based compounds are effective for repairing concrete structure damaged due to alkali silica reaction (ASR). Moreover, CFRP sheet bonding, concrete jacketing and PC confined method have been applied for strengthening ASR-affected bridge structures. Regarding to the silicate-based penetrating sealer, the results from accelerated mortar bar test experiments show that ASR expansion occurred on mortar bars immersed in sodium silicate solution (Na 2 SiO 3 ) and no expansion could be observed on mortar bars immersed in lithium silicate (Li 2 SiO 3 ) solution. Thus, Li 2 SiO 3 is recommended to be used for repairing ASR-affected structures. In addition, experimental works on the mitigation effect of supplementary cementitious materials (SCMs) were also conducted. The results show that 10% to 20% replacement ratio of high quality fine fly ash used in this study (I-type fly ash classified by JIS A6201 from Nanao-ohta coal-fired power plant product) could almost completely inhibit the ASR in both, JIS and Danish accelerated expansion test method. In addition, 15% replacement ratio of this fly ash in concrete prism specimens could also suppress severe ASR expansion due to pessimum effect.