Guided by a previous study [28], samples with 16% and 24% aggregates replacement with ambient crumb rubber were chosen in this study as well. In all mixtures, crumb rubber was partially replaced (volumetrically) the fine aggregates. Crumb rubber was added to the dry aggregate and initially mixed for 2 min. Table 2 shows the mixture proportion used in this study. In addition, in order to evaluate the dilution effect of reducing 16% and 24% mineral reactive aggregate on the ASR expansion of the mortar bars, two more mortar mixtures wherein the 16% and the 24% of reactive aggregate were replaced by inert non-reactive aggregate, were prepared.