Since 2006, research funded by the Texas Department of Transportation (TxDOT) has evaluated the use of coatings and sealers for mitigating expansion due to alkali-silica reaction (ASR) and/or delayed ettringite formation (DEF) in hardened concrete. The report herein includes a project summary of previous work in Phase I, led by Racheal Lute (2008) and Charles Rust (2009). The Phase II research, described in this thesis, established concrete exposure blocks and NCHRP 244 Series II testing as the cornerstones of characterizing coating effectiveness. The studies assessed coating system performance by examining the contribution of steel reinforcement, the effects of aggregate reactivity, the size limitations of treatments, and the impact of painted concrete substrates. Lastly, this thesis describes the preliminary results of a field study site of columns supporting a flyover, and a concrete exposure block site in Houston, Texas. Overall, the results are encouraging as several coatings have reduced expansion by lowering internal relative humidity.