EFFECTS OF CARBONATION TO MICRO STRUCTURE AND PORE SOLUTION

摘要

The microstructure of concrete plays a significance role in modelling the lifetime prediction of constructions, and in the investigation of damage mechanisms, like freeze-thaw attack, sulphate penetration or alkali-silica reaction. Alterations of the microstructure and pore solution through carbonation must always be considered. Carbonation is an ongoing process that can induce major changes to the outer layer, for example through the formation of amorphous silicate, even after years. A drastic change of the permeability is the consequence. The formation of metastable calcium carbonate, which can be observed in some cases, leads also to changes in the pore size distribution. Carbonation leads to transformations of the pore solution, like salt concentration or pH, and subsequent alteration of the solid matrix. Changes at the interface between cement stone surface and pore solution have a strong impact on the concentration of some harmful ions like sulphate and chlorine in the pore solution. Modelling the alteration of system microstructure and pore solution must consider the type of cement, the exposure to the environment of the construction, the pore structure of the outer layer after curing and the buffer of basic compounds.