Investigating the deterioration of concrete exposed to potassium acetate deicer solution

Abstract

This dissertation examines the effect of potassium acetate (KAc) on concretes, mortars and pastes. The Colorado Springs Gazette (Colwell, 2006) first reported damage to the Colorado Springs Airport that alleged the use of K.Ac as a runway deicer accelerated alkali-silica reaction (ASR). Studies conducted by Rangaraju et al. (2007a), and Giebson et al. (2010) have focused mostly on K.Ac exacerbating ASR. This experimental study examined the effect of the concentration and type of solution, effect of exposure temperature, effect of sample size, effect of aggregate type, and effect of concrete compositions on the nature of the deterioration. Experiments were also conducted to examine the effect of K.Ac deicer on concrete containing alkali-silica reactive aggregates. The main testing however was completed on concretes and mortars with nonreactive aggregate, and pastes with the aim of elucidating the mechanism(s) or chemical reaction(s) responsible for the (non-ASR-related) deterioration previously observed in laboratory studies. With the use of techniques such as X-ray diffraction (XRD) and scanning electron microscopy (SEM) a chemical reaction between the K.Ac deicer solution and ettringite was observed to have occurred in paste and mortar samples. K.Ac reacted with ettringite (C3A •3CSH2 •H32) to form arcanite (K2S04) and a calciumaluminate phase (possibly C4AH19). Testing was also conducted to find why there was excessive damage observed in pastes, mortars, and concretes in laboratory studies, yet very little damage has been seen in field studies. This testing concluded that the lack of penetration of KAc into concrete exposed to low temperatures is the main reason little damage has been seen in the field. Concrete that has not been cracked due to ASR is very resistant to the penetration of KAc when KAc solution is only applied during cold temperatures. The results show that if a pavement has been constructed with a non-reactive aggregate and the anti-icing/deicer solution is only applied when the temperature is near freezing or below then little significant damage attributed to KAc occurs.