The biggest advantage of strengthening concrete structures with FRP is quick installation without the need to destroy this material on the concrete surface. Also, the low processing time does not cause any disruption to the operation of the structure. It is important to note that the installation method varies depending on the fiber. In fact, failure to pay attention to operational points and failure to use the expert team for infrastructure and installation of FRP materials leads to capital loss and in some cases damage to the structure.
FRP installation can be summarized in three steps
• Infrastructure and surface preparation
• Mixing epoxy adhesive and cutting fibers
• FRP installation based on designer drawings
Here is a brief overview of common mistakes that occur when it comes to using FRP materials:
• The minimum working temperature is 5 degrees Celsius and the maximum is 45 degrees Celsius. Our problems are usually due to working at low temperatures, which, contrary to popular belief, this problem is not solved by adding quick-setting materials, and these same materials reduce the adhesion resistance of the adhesive.
• The humidity of concrete surfaces during work should be less than 3%.
• FRP systems like all adhesive systems must be free of any dust and interface layer during installation. The concrete surface should be washed and cleaned with an air pump or water jet. FRP fibers should also be kept in the workshop away from environmental pollution.
• The use of adhesive on the FRP surface not only helps with adhesion, but in many cases it has been observed that the workforce has used epoxy adhesive on the FRP fibers to hide the shortcomings in the FRP installation process.
• Different mixing methods, mixing times and adhesive setting times in different epoxy resins and in some cases the use of polyester resins instead of epoxy resins can significantly reduce the adhesion of FRP fibers to the concrete surface.
In thick fibers, the fiber and the concrete surface must be impregnated separately, and at temperatures above 400 g/m2, the use of epoxy gel reduces the quality of FRP installation.
Initial repair and creation of suitable conditions for installation
Before doing any work with FRP panels, the damaged concrete must be removed and if it reaches the reinforcement, it must be repaired or replaced if it needs to be replaced. Smooth the material with one hand. The surface must be clean before installation and free of moisture, grime and grease. These materials cause a lot of disruption to the structure of FPR fibers.
Another necessary step before installation is to prepare the surface required for installation. For example, if salts and chlorides have damaged the concrete surface, all damaged parts must be removed and replaced with new ones.
Flattening the surface of the FRP member
The surface required for installation is prepared by the following steps:
Destruction of damaged parts from attack by chemicals such as sulphates and chlorides
Create a new layer to replace the damaged layers
Filling the surface defects of the organ with restoration paste
Impregnation of the member’s surface with primer resin
FRP member leveling
FRP fiber implementation
Manual implementation method
Round screw method with machine tool
Fiber impregnation machine
Resin injection transfer method without the need for drilling
How to install FRP manually
Manual installation of FRP is an easy method compared to other methods and its use is more common in concrete structure strengthening system and FRP polymer fiber building reinforcement system.
In this method, attention should be paid to the parameters of direction, width and number of fiber layers. Carbon fabrics should be cut with fine-tooth scissors. For commissioning and installation, FRP must be impregnated with FRP epoxy resin and then apply epoxy gel to the concrete surface, thus starting the layering process.
FRP fibers have coating layers after being attached to surfaces, we separate them and then the fibers attached to the surface are impregnated with epoxy resin by rollers.
The installation process should be in the direction of the FRP material threads and start from the middle of the piece and continue to both ends of the piece to prevent bubble formation. After smoothing the fiber surface, we have to pull out the hand roller by pressing the FRP surface by hand.
Use FRP resin adhesive
The use of resin to bond FRP has a fixed value and follows a set of specific principles and rules. The resin or primer should not be diluted. After mixing the hardener with the resin, this adhesive must be used for a certain period of time so that it does not spoil. The time it takes to use the glue is called Pot Life.
You should not use residual glue after Pot Life. This is because the viscosity of the material increases and prevents FRP and saturation.
Install the fibers on the surface
After impregnating the desired surface with resin, it is time to glue the FRP sheet, which must be boiled and impregnated on the desired surface. Boards must be sized and glued to surfaces free of any contamination.
conclusion
The FRP installation method has many steps, and we have explained them somewhat above. FRP installation is best done by experienced people so that they can carry out all the steps well for you. FRP should be glued in such a way that no bubbles form underneath and it should be glued directly and smoothly.