ANALYTICAL STUDY ON PREDICTION OF PORE VOLUME CHANGES DUE TO CARBONATION OF CONCRETE BASED ON DETAILED CARBONATION MODEL INTRODUCED CHEMICAL EQUILIBRIUM THEORY

The detailed modeling dependent on alkali ion density of pH transition in pore solution, carbonation mechanism and changing of pore volume due to carbonation reaction in concrete are developed based on a law of electric charge balance in analytical chemistry. While calcium hydroxide on solid phase, it is noted that pore solution pH will be constant value. On the other hand, after disappearance of calcium hydroxide existing on solid phase, it is noted that the gradual drop of pore solution pH will be occur and the drop rate becomes higher according to high alkali ion density in concrete. Moreover, it seems that the changing of pore volume due to carbonation will be determined by CaO/SiO2 ratio mainly and in the region of high CaO/SiO2 ratio the pore volume increases, on the other hand in the low CaO/SiO2 ratio the pore decreases.