Microstructural Characterization of Leaching Effects in Cement Pastes Due to Neutralisation of their Alkaline Nature. Part I: Portland Cement Pastes

Abstract When concrete is exposed to the elements, its underlying microstructure can be attacked by a variety of aggressive agents; for example, rainwater and groundwater. The knowledge of concrete resistance to long term water aggression is necessary for predictions of their performance in different environments. This study aims to analyse the effects of leaching on the microstructure of Portland cement binders. Leaching of cement pastes was performed by an accelerated extraction leaching test that produces significant degradation and helps to achieve equilibrium or near-equilibrium conditions between the leachant medium and cement paste. FTIR spectroscopy, TG-DTA thermal analysis, low temperature nitrogen gas sorption, and geochemical modelling were used to characterize the microstructural changes produced in cement pastes at different equilibrium pHs reached during the leaching process.

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