Book excerpt: This handbook is designed to help highway engineers and bridge inspectors spot and fix this very damaging and difficult-to-detect problem, namely, alkali-silica reactivity (ASR). The 49-page handbook provides for the field identification of ASR in portland cement concrete structures, such as highway pavements and bridges. ASR occurs when silica or silicates in aggregates react with alkali in the cement to form a gel-like substance which absorbs water and eventually cracks the concrete. Some areas of the country are more susceptible to this than others. Accurate detection of ASR is the key to choosing the best rehabilitation strategy. The proper diagnosis and assessment of the problem is covered.