Application of an innovative methodology to assessing the alkali-silica reaction in concrete

Abstract

A new methodological approach, based on two innovative parameters such as the threshold alkali level (TAL) of aggregates and the tolerable driving force (Δtol) provided by an inhibitor of the deleterious alkali-silica reaction (ASR), was used for the assessment of the ASR expansivity of concrete mixes made with different alkali-reactive aggregates and different cements (one limestone-Portland (or Portland) cement, three pozzolanic cements and one blast furnace cement). Concrete prism expansion tests were performed under two different test conditions: 38 °C and 100 % RH or 60 °C and 100 % RH. The alkali-reactivity of the aggregates was also evaluated by using the petrographic examination and the ultra-accelerated mortar bar expansion test in 1 M NaOH solution at 80 °C. The test results were interpreted according to the innovative methodological approach, as well as according to a traditional approach based on pass-fail criteria. It was found that the two parameters, TAL and Δtol, are appropriate for both assessing the alkali-reactivity of aggregates (TAL) and comparing the efficacy of blended cements as ASR inhibitors (Δtol). These two parameters may be rapidly evaluated (150 days of testing) by using the accelerated concrete prism expansion test at 60 °C and 100 % RH.