鉄筋コンクリート造建築物の中性化進行に及ぼすモルタル仕上げおよび方位の影響

抄録

 The purpose of this study is to investigate the actual condition of concrete carbonation according to each direction for existing RC buildings covered with finishing mortar as a finishing material for the exterior to evaluate its effectiveness suppressing carbonation for each direction.
 There are some previous studies that report on the difference in progression of carbonation according to each direction for exposed concrete sections of existing buildings. However, there are few studies that report on cases or conduct a detailed analysis on the factors regarding the progression of carbonation by each direction for concrete covered with exterior finishing material.

 In general, the surfaces of buildings are covered with external finishing materials, so it is rational and crucial to consider the effect of the finishing materials suppressing carbonation when evaluating the progression of carbonation in concrete. Also, when conducting a durability study on an existing RC building, there is a limited scope of the building where investigation is possible in many cases. Therefore, having a grasp on the degree of impact that a difference in direction tends to have on the progression of carbonation as numerical data is beneficial in that one can appropriately estimate the entire condition of the building from the survey results of one portion.

 Research was conducted for this study following the process below. First, for 100 collective residential buildings, 200 core samples were collected from the north and south sides of structural concrete wall. The depth of carbonation, the thickness of the finishing mortar and other factors was measured, to investigate the difference in carbonation of the concrete according to each direction. Next, the above data were applied to a formula that replaces the carbonation suppression effect from the exterior finishing material with the depth at which carbonation is delayed, thus deriving the carbonation resistance of finishing mortar and the carbonation rate by each direction. Furthermore, we considered the trend of carbonation from the perspective of difference in environmental factors due to direction or, in other words, the difference in temperature and relative humidity.

 The results are as follows. The average carbonation resistance of the finishing mortar was 3.83 √years for south-facing walls, 5.13 √years for the external side of north-facing walls and 5.00 √years for the internal side of north-facing walls. The average carbonation rate of the finishing mortar was 7.69 mm / √year on south-facing walls, 4.95 mm / √year on the external side of north-facing-walls and 4.98 mm / √year for the internal side of north-facing walls. The average ratio of carbonation rate of the finishing mortar between the north-facing and south-facing wall of the same building was about 1.62.