Evaluating Alkali-Silica Reactivity of Aggregates Using the New Miniature Concrete Prism Test and Other Standard Test Methods

Abstract

The alkali-silica reaction (ASR) has been recognized as a major distress in concrete for nearly a century. In the US, ASR is a major cause of the deterioration of highway concrete structures (i.e., bridges and pavements). A research study was recently undertaken in the state of Idaho to evaluate the advantages associated with implementing the miniature concrete prism test (MCPT) from current standards for various reactive aggregates. A total of 11 different aggregate materials (both coarse and fine fractions), including a nonreactive reference aggregate, were collected from various sources and tested using the 56-days MCPT as well as the commonly used accelerated mortar bar test (AMBT). In addition, selected aggregate samples were tested using the 1-year long concrete prism test (CPT) and the 6-month accelerated concrete prism test (ACPT). The results demonstrated that the 56-day MCPT method resulted in higher percent expansion compared with the 14-day AMBT and 1-year CPT methods for the fine fractions of the test aggregates. The coarse fractions of the test aggregates, on the other hand, exhibited a lower percent expansion during the 56-day MCPT compared with the 14-day AMBT. Overall, the MCPT test results were found to correlate well with the 14-day AMBT and 1-year CPT test results. In addition, the 6-month ACPT method showed similar results to the ones of the 1-year CPT method, with high correlation between both methods. Recommendations were made based on the findings from this study to facilitate the implementation of the MCPT into practice by state and local highway agencies for better assessment of the ASR potential of aggregates.