Mitigating Alkali-Silica Reaction in Concrete Containing Recycled Concrete Aggregate

Abstract

This work involves research on the use of fly ash to mitigate alkali-silica reaction (ASR) in concrete made with recycled concrete aggregate (RCA) that comes from concrete with a known ASR history. Modified ASTM C 1260 and C 1567 with different aggregate grading showed that a 25% cement substitution with a Class F fly ash controlled the expansion under 0.10% at 28 days. RCA from I-95 near Gardiner, Maine, was selected for this study. The RCA, coarse aggregate recovered from the RCA, and currently produced aggregate from the same source as the RCA were evaluated in the laboratory. The conventional ASTM C 1260/1567 14-day expansion results correlated well with ASTM C 1293 1-year criteria. The ASR-modified ASTM C 1260/1567 28-day expansion results also correlated well with ASTM C 1293 2-year failure criteria. Pore solution and thermal gravimetric analysis revealed both calcium hydroxide and alkalis are reduced by fly ash substitution. Calcium depletion alone is a sufficient condition for ASR arrest, but the ...