Evaluation of Alkali-Silica Reaction by Concrete Microbar Test

This study investigates different aspects of the proposed concrete microbar test that evaluates alkali-silica reaction expansions by using aggregate having particles size between 4.75 and 12.5 mm (No. 4 and 1/2 in.), a water-cement ratio (w/c) of 0.33, and an aggregate-cement ratio of 1:1. The concrete microbar test method was modified by using different aggregate gradations. Considering no-fines mixtures, increasing the coarsest aggregate size fraction in the coarse aggregate decreased the alkali-silica reaction expansions. However, expansions were increased by the addition of fine aggregate to concrete microbar mixtures. The alteration of w/c in the practical range for these mixtures did not strongly affect the expansion values. The effects of some supplementary cementing materials (fly ash, natural pozzolan, and natural zeolite powder) on ASR expansions were studied by using the concrete microbar test and the accelerated mortar bar test method. Both of the accelerated test methods revealed comparable expansions in evaluating the effect of supplementary cementing materials on alkali-silica reaction expansions.