Alkali silica reactivity of various andesites in saturated NaCl solution

Reactivities of various andesites and some other volcanic rocks were investigated by an accelerated mortar bar test in saturated NaCl solution (saturated NaCl method). In Japan, because of its low alkali content of Portland cement, total alkali amount in concrete can be controlled under 3.0 kg/m ³ for most cases. However, environmental alkalis such as deicing salt may add extra alkalis to concrete and ASR risks may increase. This risk is thought to be able to be checked by saturated NaCl method. The experiment shows that the most reactive andesites contain tridymite. Cristobalite is the second reactive phase. Glass seems non-reactive in the saturated NaCl method. Glassy andesite without silica minerals is judged as reactive by chemical method but innocuous by saturated NaCl method. Glass phase has been believed reactive in high alkali condition but there is a possibility that it is less reactive in specific environments such as deicing salt.