An experimental study on sag-resistance ability and applicability of sprayed FRP system on vertical and overhead concrete surfaces

This paper reports an experimental study on the sag resistance of a sprayed FRP system for use in retrofit applications. First, sag flow tests were carried out to evaluate the effect of sag control agents (SCA) and influence of reinforcing fibers on the sag-resistant ability of the materials. From the sag flow tests, the mechanisms of sag resistance for an uncured modified epoxy resin and the sprayed FRP system were verified. Then, in situ sag resistance tests of the sprayed FRP system on vertical or overhead concrete surfaces were carried out. In addition, the upper limit of the lay-upped thickness of the sprayed FRP coating was measured when the sag flow or sagging of the coating from the concrete surface started after continuous spraying work. It was concluded from the in situ sag resistance tests of the sprayed FRP system with SCA as well as reinforcing fibers that the system showed good sag resistance on vertical and overhead concrete surfaces. Finally, a series of pull-off bond tests were conducted to evaluate the applicability of the sprayed FRP system to vertical and overhead concrete surfaces. It was concluded that applicability of the sprayed FRP layer to vertical and overhead concrete surfaces was feasible.