STUDIES OF CHLORIDE BINDING IN PASTE EXPOSED IN CHLORIDE SALT SOLUTIONS

摘要

In this paper, bound chloride content of paste particle and paste, which are plain pastecontaining Portland cement (PC) alone and pastes with 0-50% of fly ash addition, 0-65% ofground granulated blast furnace (GGBS), was systematically investigated under chloride saltsolutions. The chloride salt solution includes three types: 3%NaCl solution, Qingdao seawater and composite solution of 3% NaCl and 1% MgSO4. The experimental results shownthat the amount of bound chloride is about 4.8～4.9 mgCl/g sample for paste particles storedin NaCl solution, and it reduces about 33～46% and 11～13% as paste particles stored in Seawater and in composite solution, respectively. The chloride binding capacity of plain paste isabout 0.2 as it immersed in NaCl solution, and it reduces about 50% and 25% as paste storedin sea water and in composite solution. The chloride binding capacity of pastes with GGBS isabout 0.32-0.79, and it is the highest and about 6.6 times that of the plain paste as GGBSreplacement level being 35%. The chloride binding capacity of paste with fly ash ranges from0.2 to 0.28. And for a fly ash replacement level of 25%, the chloride binding capacity is thehighest. In order to elucidate the above experimental results in a microscopic scale, themechanism was also investigated by derivative thermogravimetry and differential enthalpiccalorimetry (DTG/DSC) and X-ray diffraction (XRD) techniques.