Evaluation of Surface Treatments to Mitigate ASR

Project Details









W. Micah Hale




Alkali silica reactions, Arkansas, Concrete structures, Cracking, Deterioration, Expansion, Freeze thaw durability, Sealing Compounds, Silane, Surface treating

Project description

Alkali-silica reaction (ASR) is an expansive reaction between the alkalis in cement and reactive silica in aggregates. Transportation agencies are currently experiencing the detrimental effects of ASR. Current research shows that concrete expansion due to ASR may be exacerbated by extreme weather changes (e.g. freeze/thaw cycles), which can cause further deterioration of pavements and structures. This proposed project will examine the effectiveness of silane and other potential sealers in mitigating ASR in concrete structures. The expansion that occurs within the alkali-silica gel can exceed concrete‰'s tensile strength, which leads to cracking and concrete deterioration. For this expansion to occur, sufficient moisture must be available. When the internal relative humidity of concrete falls below 80 percent, ASR will cease and expansion will stop. One of the major objectives of this project is to examine the effectiveness of silane (and other sealers) in reducing the internal relative humidity of ASR-infected concrete. This will be achieved through two research phases. The first phase will monitor the expansion of an ASR-infected concrete barrier wall in Northwest Arkansas. The barrier was instrumented on a previous research project. This project will continue research with regard to the monitoring of expansion and relative humidity. Application rates for silane and other sealers will also be evaluated to determine the most effective mitigation regimen. The second phase will consist of casting and testing field exposure blocks containing reactive silica. The blocks will be treated with a variety of vapor barriers to reduce internal relative humidity, including silane, to determine the most effective treatment with regard to ASR expansion