Using Modified Mortar-Bar Test Method to Access the Effects of Deicers on Expansion of Mortars With and Without Reactive Aggregates

Abstract

The influence of deicing chemicals on alkali reactivity of aggregates is still an area of active research. The potential alkali reactivity of aggregates is often tested using the ASTM C1260 method. This research used the modified ASTM C1260 to test the potential alkali reactivity of aggregates. The modification included replacing the standard 1N sodium hydroxide (NaOH) used in ASTM C1260 with eutectic concentrations of the three common chloridebased deicing chemicals: sodium chloride (NaCl), magnesium chloride (MgCl 2 ), and calcium chloride (CaCl 2 ). The results showed that the mortar bars with reactive aggregate (Jobe sand) stored in NaCl solution developed higher expansion than those stored in MgCl 2 and CaCl 2 solutions. It seems NaCl can initiate (or accelerate) the alkali silica reaction (ASR), while MgCl 2 and CaCl 2 do not seem to contribute to ASR. In addition, after about 100-120 days of exposure, irrespective of whether they contained reactive (Jobe sand) or nonreactive (Ottawa sand) aggregates, the mortar bars submerged in the MgCl 2 solution started to crack and disintegrate. This implies that the observed expansions should be attributed solely to the effect of these deicers on the cement paste itself rather than to their effects on aggregates. The proposed modified test method produced conclusive results within a relatively short testing time (~28 days).

Role of chemical admixtures in improving wet-mix shotcrete performance for ground support

“…Accelerated mortar-bar testing (ASTM International 2013) was done to confirm the reactivity of the aggregates and determine which SCM would be a suitable option to mitigate ASR. As it is well published in the literature (Chiu & Olek 2014;Degirmenci et al 2011), mixes that expand more than 0.10 % at 16 days after casting are indicative of potentially deleterious expansion. Based on Figure 1, it is confirmed that aggregates are highly reactive as the mix containing Portland cement only had significantly higher expansion than the limit.…”