Electrochemical chloride extraction to halt corrosion of reinforcement

This thesis presents results of experiments designed to study the effect of applying electrochemical chloride extraction (ECE) to a range of different hardened cement pastes. Rectangular prism specimens of hydrated cement paste containing sodium chloride at different concentrations were subjected to electrolysis between the embedded steel cathodes and external anodes of activated titanium mesh. The cathodic current density used was in the range of 1 to 5 A/m2 with treatment periods of 4 to 12 weeks. After treatment, the specimens were cut into sections which were subjected to pore-solution expression and analysis in order to determine changes in the distribution of free and total ionic species. The effect of the ECE treatment on the physical and microstructural properties of the cements was studied by using microhardness and MIP techniques. XRD was employed to look at the possibility of ettringite redistribution as a result of the accumulation of soluble sulphate ions in the cement matrix near the cathode during ECE. Remigration of chloride which remains after the ECE treatment and distribution of other ions were studied by analysing specimens which had been stored for several months, after undergoing ECE treatment. The potentials of the steel cathodes were also monitored over the period to detect any changes in their corrosion state. The main findings of this research were as follows: 1, ECE, as applied in this investigation, was capable of removing both free and bound chloride. The removal process occurred relatively quickly and an equilibrium between free and bound chlorides in the specimens was maintained throughout. At the same time, alkali concentrations in the pore solution near the steel cathode increased. The soluble sulphate ionic concentration near the cathode also increased due to the local increase in the pH of the pore solution. 2, ECE caused some changes in physical and microstructural of the cement matrix. However these changes were minimal and in the case of microhardness, the results were highly scattered. Ettringite in the bulk material well away from the cathode was found not to increase significantly with the increase in charge passed.3, Remigration of chloride and other ionic species occurred slowly after cessation of ECE with a resultant gradual increase in the Cl-/OH- ratio around the steel.4, The removal of chloride from blended cements was slower than that from OPC.

Mesmerized by enlargement:the EU’s Eastern Neighborhood Policy and New Member State transition experience

The accession of the East-Central European (ECE) countries carried a promise of enhancing and enriching the EU’s Eastern policy. The new member states had the strongest interests among EU member states to ensure that countries in the East are prosperous, stable and democratic. Yet, EU’s Eastern policy has been largely criticised for its ineffectiveness. So why have they not been able to address the shortcomings in the EU’s Eastern policies? The article argues that the ECE countries supported the way the EU’s Eastern policies were conceived and implemented because they saw it as a potent vehicle to promote their own transition experience not only in the region but also within the EU. We argue that the ECE states have experienced three types of challenges when promoting their transition experience. First, uploading to the EU level remained largely at a rhetorical level. Second, there are conceptual and practical difficulties in defining what constitutes transition experience and harnessing it, as well as coordinating its transfer between the ECE states. Finally, while using transition experience as the basis for their development assistance strategies, the ECE countries actually insufficiently conceptualised the ‘development’ aspect in these policies. Being so driven by their own experience, they have not drawn the lessons from enlargement to use in a non-accession context, especially by incorporating the broader lessons with regard to development.