Experimental study of vacuum grout injection method for post-tensioned prestressed concrete structures

If voids occur because the inside of the sheath of a tensioned Prestressed Concrete structure is not filled with grout, water and chloride ions can penetrate, causing strand breakage and bridge collapse due to corrosion of the strands. The causes of voids in the sheath of PSC structures include material problems such as bleeding of grouting materials and hydrogen gas generation due to the use of metallic expanders, inadequate use of equipment, and insufficient installation of outlets due to insufficient skilled workers. In order to solve these problems, materials such as non-bleeding grout, non-hydrogen gas-expanded expansion material, and pre-mixed grout have been developed. However, in terms of grout equipment and grouting methods, and in consideration of constructability, this field is still insufficiently developed in Korea. In this study, an experiment was conducted to fill water and grout in a vertical tube to evaluate the field applicability of a vacuum grouting method in which grout was injected into a sheath tube using a vacuum grouting apparatus. Based on the experimental results, if the inside of the sheath pipe of the PSC structure is depressurized under vacuum pressure and grout is injected, it is considered that it is possible to fill the grout tightly in the sheath pipe by vacuum injection and the pumping injection using hydraulic pressure.