Grouting and pull-out tests of hollow-type prestressing-strands for an internal strengthening system

Abstract

The present study focused on creation of an internal strengthening system, which involved embedding a post-tensioned PC tendon in a wedge-shaped anchorage of an existing concrete member. Under conditions with narrow work spaces, it was difficult to employ the previous system using a post-tensioned prestressing bar, as adequate backspace was required to install the bar. A flexible hollow corrugated pipe covered with steel wire cables seemed applicable even in such narrow spaces. Interestingly, the hollow stranded tendon could also be used as a grouting-pipe to fill the internal anchorage. The foci of this study were to develop a grouting material suitable for passage through a hollow corrugated pipe, and to determine the applicability of the hollow-type prestressing tendon for the internal strengthening system. In the study, a horizontal grouting test was first conducted using 5 m-long corrugated pipes of 10 mm internal diameter. It was confirmed from the grout and strength tests that some grouting materials were applicable for filling the hollow-type PC strands. In addition, pull-out tests of the prestressing tendon embedded in the anchorage of mock-up RC blocks were conducted to examine their load-bearing capacity. Furthermore, visible tests of the horizontal and upward grouting were conducted to confirm the filling condition in the wedge-shaped anchorage. The test results confirmed adequate load-bearing capacity of the hollow prestressing tendon embedded in the anchorage when the filler applicable to horizontal grouting was used.