Field Evaluation of Concrete using Hawaiian Aggregates for Alkali Silica Reaction

Alkali Silica Reaction (ASR) occurs in concrete when the alkali hydroxides (Na+, K+ and OH-) from the cement react with unstable silica, SiO2, in some types of aggregate. The resulting gel will expand when it absorbs water, potentially leading to cracking and overall expansion of the concrete. Concrete aggregates available in Hawaii have not demonstrated a history of ASR, however, results of accelerated laboratory tests using ASTM C1260 indicated a potential for ASR with some aggregates. In order to assess the accuracy of the laboratory test results, a long-term field study of the potential for ASR in concretes made with Hawaiian aggregates was initiated in 2011. Forty concrete specimens were constructed of various concrete mixtures using aggregates from all Hawaiian aggregate sources, and some US mainland aggregates known to exhibit ASR expansion. The specimens are located in an open field site in Manoa valley on the Hawaiian Island of Oahu, exposed to relatively high humidity and frequent rainfall. A weather station at the site records the ambient conditions on a continual basis. This paper describes the field evaluation program and presents the results after six years of monitoring. Comparisons are made between the field observations and accelerated laboratory tests.