Abstract
The floor concrete of roof parking which passed 18 years from construction had been discolored to light straw yellow. The discolored depth of zone A was about 5mm, zone B was about 25mm. There was a big difference between the discolored depth of zone A and its of zone B. In order to consider the properties of each concrete and the cause of discolor, the examinations of neutralization depth, compressive strength, differential thermal analysis, diffractometry, pore size distribution and chloride ion amount were carried out. As a result, it was confirmed that the cement hydrate (C-S-H hydrate) who should have been stability naturally disintegrated by carbonation. And it was thought that the difference of construction condition and the difference of environmental condition and the concentrated chloride ion had caused the discoloration and had accelereted the carbonation of the concrete.
