Aspects of the prevention and repair of chloride-induced corrosion of steel in concrete

Sodium formate, potassium acetate and a mixture of calcium and magnesium acetate (CMA) have all been identified as effective de-icing agents. In this project an attempt has been made to elucidate potentially deleterious effects of these substances on the durability of reinforced concrete. Aspects involving the corrosion behaviour of embedded steel along with the chemical and physical degradation of the cementitious matrix were studied. Ionic diffusion characteristics of deicer/pore solution systems in hardened cement paste were also studied since rates of ingress of deleterious agents into cement paste are commonly diffusion-controlled. It was found that all the compounds tested were generally non-corrosive to embedded steel, however, in a small number of cases potassium acetate did cause corrosion. Potassium acetate was also found to cause cracking in concrete and cement paste samples. CMA appeared to degrade hydrated cement paste although this was apparently less of a problem when commercial grade CMA was used in place of the reagent grade chemical. This was thought to be due to the insoluble material present in the commercial formulation forming a physical barrier between the concrete and the de-icing solution. With the test regimes used sodium formate was not seen to have any deleterious effect on the integrity of reinforced concrete. As a means of restoring the corrosion protective character of chloride-contaminated concrete the process of electrochemical chloride removal has been previously developed. Potential side-effects of this method and the effect of external electrolyte composition on chloride removal efficiency were investigated. It was seen that the composition of the external electrolyte has a significant effect on the amount of chloride removed. It was also found that, due to alterations to the composition of the C3A hydration reaction products, it was possible to remove bound chloride as well as that in the pore solution. The use of an external electrolyte containing lithium ions was also tried as a means of preventing cathodically-induced alkali-silica reaction in concretes containing potentially reactive aggregates. The results obtained were inconclusive and further practical development of this approach is needed.

Metaphors in Hugo Chávez's political discourse:conceptualizing nation, revolution and opposition

This dissertation examines Hugo Chávez's choice of metaphors in his efforts to construct and legitimize his Bolivarian Revolution. It focuses on metaphors drawn from three of the most frequent target domains present in his discourse: the nation, his revolution, and the opposition. The study argues that behind an official discourse of inclusion, Chávez's choice of metaphors contributes to the construction of a polarizing discourse of exclusion in which his political opponents are represented as enemies of the nation.The study shows that Chávez constructs this polarizing discourse of exclusion by combining metaphors that conceptualize: (a) the nation as a person who has been resurrected by his government, as a person ready to fight for his revolution, or as Chávez himself; (b) the revolution as war; and (c) members of the opposition as war combatants or criminals. At the same time, the study shows that by making explicit references in his discourse about the revolution as the continuation of Bolívar's wars of independence, Chávez contributes to represent opponents as enemies of the nation, given that in the Venezuelan collective imaginary Simón Bolívar is the symbol of the nation's emancipation.This research, which covers a period of nine years (from Chávez's first year in office in 1999 through 2007), is part of the discipline of Political Discourse Analysis (PDA). It is anchored both in the theoretical framework provided by the cognitive linguistic metaphor theory developed by George Lakoff and Mark Johnson described in their book Metaphors We Live By, and in Critical Metaphor Analysis (CMA) as defined by Jonathan Charteris-Black in his book Corpus Approaches to Critical Metaphor Analysis.The study provides the first comprehensive analysis of metaphors used by Chávez in his political discourse. It builds upon the findings of previous studies on political discourse analysis in Venezuela by showing that Chávez's discourse not only polarizes the country and represents opponents as detractors of national symbols such as Bolívar or his wars of independence (which have been clearly established in previous studies), but also represents political opponents as enemies of the nation.