An Evaluation of Several Methods for Detecting Alkali-Carbonate Reaction

About the report:

Based on the review of previous Council reports, a strategy for the use and control of potentially reactive carbonate rocks is discussed in this report, which lists the previous reports in a bibliography. Specifically, this report discusses an evaluation of four test methods using a suite of 22 rocks exhibiting a wide range of potential expansion and mineralogical compositions. The purposes of the evaluation were (1) to evaluate the ability of the methods to predict detrimental expansions of concrete caused by alkali-carbonate reactions, and (2) to evaluate the capability of the methods for characterizing the reactive potential of commercial aggregate sources. The aggregates were evaluated in concretes made with three cements having different alkali contents. Testing methods included measurements of the expansion of concrete moist cured for 5 years, resistance of concrete to freezing and thawing, expansion of mortar bars, and length changes of rock prisms stored in an NaOH solution. The following conclusions were drawn. (1) Expansions of the apparently nonreactive aggregates were generally higher than values reported in the literature, and (2) ASTM Method C 586, while proving to be essentially a screening method, when used in conjunction with other procedures, such as petrographic examination, can be used for providing a rapid quantitative evaluation of the potential for expansion of the aggregate in concrete.

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