Mva Miruna Florea

Chloride binding related to hydration products Part I: Ordinary Portland Cement

A new hydration model of OPC [1, 2] was used in this study. The quantities of hydration products were calculated for saturated state hydration and for samples that have been dried to 11% rh after hydration. The chloride binding of several hydrated phases (C-S-H, monosulfate, hydroxy-AFm, AFt, CH, and Friedel’s salt) has been studied and estimated in relation to the chloride content of the pore solution. Combining two new isotherms, for C-S-H and AFm chloride binding in hardened cement paste, and the computed quantities of all hydration products, a new formula for the chloride binding capacity of OPC pastes has been deduced. The new model is based on the chloride binding abilities of each hydrated phase, and therefore can distinguish between their contributions at different free chloride concentrations. When compared to experimental data, the results obtained using this new chloride binding isotherm have proven to accurately describe the chloride binding capacity of OPC pastes, results being within 12% of the experimental values for the whole range of free chloride concentrations considered, of up to 3 M.

A two-stage treatment for Municipal Solid Waste Incineration (MSWI) bottom ash to remove agglomerated fine particles and leachable contaminants

In this lab study, a two-stage treatment was investigated to achieve the valorization of a municipal solid waste incineration (MSWI) bottom ash fraction below 4mm. This fraction of MSWI bottom ash (BA) is the most contaminated one, containing potentially toxic elements (Cu, Cr, Mo and Sb), chlorides and sulfates. The BA was treated for recycling by separating agglomerated fine particles (≤125µm) and soluble contaminants by using a sequence of sieving and washing. Initially, dry sieving was performed to obtain BA-S (≤125µm), BA-M (0.125-1mm) and BA-L (1-4mm) fractions from the original sample. The complete separation of fine particles cannot be achieved by conventional sieving, because they are bound in a cementitious matrix around larger BA grains. Subsequently, a washing treatment was performed to enhance the liberation of the agglomerated fine particles from the BA-M and BA-L fractions. These fine particles were found to be similar to the particles of BA-S fraction in term of chemical composition. Furthermore, the leaching behavior of Cr, Mo Sb, chlorides and sulfates was investigated using various washing parameters. The proposed treatment for the separation of agglomerated fine particles with dry sieving and washing (L/S 3, 60min) was successful in bringing the leaching of contaminants under the legal limit established by the Dutch environmental norms.