Alkali-silica Reactivity in Virginia

About the report:

This project examined occurrences in Virginia of alkali-silica reactivity, which is a major cause of the deterioration of concrete. Concretes were studied to determine the mineral aggregates being affected, and test methods for identifying such aggregates were evaluated. Technical literature on alkali-silica reactivity was reviewed to develop a way of dealing with this problem. The results of this study reveal that the mineral primarily affected by alkali-silica reactivity in Virginia is quartz, particularly when microcrystalline or metamorphically strained. Quartz in these forms is present in most aggregate resources in Virginia. The results obtained in evaluating a proposed aggregate test method did not permit the establishment of acceptable criteria for differentiating between those aggregates that were susceptible to this reaction and those that were not. Specific issues regarding alkali-silica reactivity in need of further research are delineated. However, because of the numerous aggregate resources in the state that are potentially susceptible to alkali-silica reactivity, the way to prevent this problem in new construction is to use cementitious materials that minimize the potential for the reaction to occur. The Virginia Department of Transportation implemented specifications that require the use of pozzolans or ground slag in concretes made with cements with an alkali content greater than 0.40.

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