Dissolution phenomena of CaO-SiO2-H2O gel at Ca/Si > 1 coexisting with ettringite system

We have studied the influence of interaction between CaO-SiO2-H(2)Q JC-S-H) gel and ettringite (AFt) on their dissolution regarding the initial chemic al feature of degraded cement pore water. In this work, firstly dissolution experiments were performed in C-S-H gel at Ca/Si=1.0, 1.2 and 1.47 coexist ing with AFt of which amount was 5% of mol corresponding to each C-S-H gel. Secondly, assuming the congruent dissolution of AFt, dissolution of the sa me system was calculated by combining with the dissolution model of C-S-H g el at 1<Ca/Si<less than or equal to>1.5, considering without interaction be tween C-S-H gel and AFt. Measured and calculated results of Ca, Si, Al and S total concentrations and pH values of C-S-H gel coexisting with AFt syste m were investigated. Discrepancies between experimental and calculated Ca, Si, Al and S total concentrations and pH values suggested the importance of interaction phenomena in C-S-H gel coexisting with AFt system. By consider ing the substitutions of Al(OH)(4)(-) and SO42- with Si tetrahedra in the s tructure of C-S-H gel, these discrepancies are discussed in this study.