既存杭の引抜孔を対象とした炭酸ナトリウム混合セメントベントナイト系充填材

In a series of studies, it is aimed to develop fillings for holes formed by pulling-out piles. Cement-bentonite is used as a filling in general. Although cement-bentonite has an advantage of being able to perform blending according to circumstance of work on site, cement and water cause segregation, so uniform filling is difficult. In addition, there is a disadvantage that cement-bentonite cannot perform a predetermined strength when diluted by penetration of groundwater and so on. Sodium carbonate (Na2CO3) is a substance expected to suppress the segregation of cement-bentonite and to speed up the development of strength. In this study, we conducted an indoor mixing test on fillings mixed with Na2CO3 into cement-bentonite which is a mixture consisting of water, cement and bentonite, and examined various characteristics from the viewpoint of physical and chemical aspects. The following two points were clarified; (i) by mixing Na2CO3, bleeding of cement-bentonite is suppressed and (ii) by mixing Na2CO3, the strength development time of the cement-bentonite becomes faster and the long-term strength also increases. These two points are considered to be due to the improvement of the swelling property of bentonite, the early strength development of cement and the formation of calcium carbonate (CaCO3).