Date of Award

8-2007

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Legacy Department

Civil Engineering

Advisor

Rangaraju, Prasada Rao

Committee Member

Amirkhanian , Serji

Committee Member

Putman , Bradley

Committee Member

Fortney , Patrick

Abstract

Deicing and anti-icing chemicals such as alkali-acetate and alkali-formate based formulations are increasingly being used on airfield pavements. Among these new deicers, potassium acetate-based formulations are widely used due to their environmentally friendly nature and effectiveness in melting and undercutting ice at low temperatures. Recent research on premature deterioration of airfield pavements due to alkali-silica reaction (ASR) has indicated that alkali-acetate and alkali-formate deicers such as potassium acetate and sodium formate may have been responsible for the observed distress. In an effort to develop a deicing chemical that is benign to concrete from an ASR standpoint, a new deicing formulation based on lithium compounds is being explored. This research study presents the findings from a laboratory-based investigation on developing a lithium-acetate based deicing chemical to specifically address ASR concern in concrete. In these studies, mortar bars and concrete prism specimens were prepared with aggregates of known reactivity and exposed to solutions of pure lithium acetate and pure potassium acetate at different concentrations. In addition, parallel tests were conducted on mortar bars and concrete prisms in which test specimens were exposed to solution blends of lithium acetate and potassium acetate at different Li/K molar ratios (Li/K molar ratios=0.2, 0.4, 0.6, 0.8). Also, in order to evaluate the effect of these deicing chemicals on scaling resistance of concrete, modified ASTM C 672 tests were conducted. In order to understand the extent of externally applied damage in concrete, the K+ ion and Li+ ion profiles were established using Inductively Coupled Plasma (ICP) and X-Ray Fluorescence spectrometer (XRF) techniques. Also, tests were conducted to determine the effectiveness of lithium nitrate, when applied as a pre-treatment before exposing to potassium acetate to find its effect in mitigating ASR.
Results from this study showed that specimens containing reactive aggregates and soaked in blends of lithium acetate and potassium acetate showed little or no expansion due to alkali-silica reactivity. It is also observed that potassium acetate deicer at concentration levels of 3 and 6.4 plays a significant role in the expansion of mortar bars and concrete prisms. No scaling was observed in concrete slabs made with both reactive and non-reactive aggregate exposed to 3 and 6.4 molar KAc solutions. From the penetration test, the gradient from top to bottom showed the influence of K in concrete samples. Mortar bars which were pre-treated with LiNO3 showed significantly lesser expansion compared to bars which were not treated, upon exposure to potassium acetate deicers. In general, specimens made with high-alkali cement expanded more, compared to specimen made with low-alkali cement. It is recommended that lithium blended deicers with at least Li/K ratio of 0.2 be used for mitigating ASR. Also, low-alkali cements should be preferred when exposure to deicers is anticipated.

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