Advanced spray-up retrofitting of concrete: improved lay-up process and tensile/bond characteristics of spray-up FRP in concrete

Abstract

In order to overcome some of the problems (e.g., bond ability, anisotropic properties) between the adhesive and unidirectional FRP composites, a well-known method for using a sprayed fiber-reinforced polymer (sprayed FRP) composite was introduced (Banthia and Boyd, 2000; Boyd, 2000; Lee and Hausmann, 2004; Lee, 2004). The main objectives of this study are to advance the well-known sprayed FRP method in civil engineering as a retrofitting and strengthening material for the deteriorated concrete structures. This dissertation presents the advanced spray-up retrofitting of concrete including improved lay-up process and tensile/bond characteristics of spray-up FRP in concrete.

The dissertation consists of 4 chapters as follows: 1) Literature study: The experimental studies for retrofitting and strengthening of concrete structures using CFRP composite (e.g., sheet/strip) and sprayed FRP composite are reviewed, 2) Development of multi lay-up process: The multi lay-up process was suggested to assure the consistent quality of the sprayed FRP composite. By using the suggested multi lay-up process, a number of composite laminates are fabricated. In order to assess the quality of fabricated sprayed FRP composite, the thickness and the volume fraction of fibers of laminate were also measured, 3) Tensile behavior and strength: A series of tensile strength tests are carried out to evaluate the influence of volume fraction of fibers (e.g., 10, 25, 40 and 55%) on the tensile characteristics of the sprayed FRP composite. In addition, a comparative study between present experimental data and predicted tensile strength based on stochastic strength model (Wetherhold, 1987) is carried out and 4) Bond behavior and strength: A series of experimental tests are carried out to evaluate the pull-off bond characteristics between the sprayed FRP layer and the concrete surface. For this, pull-off bond strength and failure modes are observed. In addition, sag flow resistance of sprayed...