Accelerated mortar bar test precision with recycled concrete aggregate

Producing concrete requires considerable quantities of natural aggregates, and contributes to large amounts of solid waste in both production and when removed from service. With many structures reaching the end of their service life, a means of concrete disposal is needed that is both practical and eco-friendly. Reusing concrete waste as recycled concrete aggregate (RCA) in new concrete is a promising solution. However, the current use of RCA is generally limited to backfill and road base. Additionally, alkali-silica reaction (ASR) can pose a substantial obstacle to highly durable concrete and with limited research on ASR behavior in RCA, effective design recommendations are lacking. Current methods of ASR mitigation depend on experimental testing for aggregate classification. Therefore, a multi-laboratory study was done using ASTM C1260 with nine laboratories and 10 operators to determine within- and between-laboratory variation on ASR expansions. The result of this investigation suggests a small change to the existing precision statements of ASTM C1260 to allow the standard to incorporate RCA into the accelerated mortar bar test (AMBT). In addition, testing revealed that expansions using RCA and natural aggregates produced nonreactive or moderately reactive mortar mixtures far more frequently than highly reactive mixtures.