Please use this identifier to cite or link to this item: http://hdl.handle.net/1946/12546
Experimental research on strengthening of concrete beams by the use of epoxy adhesive and cement-based bonding material
Fibre reinforced polymer (FRP), as externally bonded reinforcement, is a very beneficial technique to repair and strengthen reinforced concrete (RC) members. This technique is used in a number of applications to increase the shear capacity of structural beams. This feature is achieved by applying e.g. basalt fibre reinforced polymer (BFRP) that is glued to the RC concrete member with an adhesive. The most common adhesive used for strengthening is epoxy. There are some limitations with the use of epoxy adhesives, including poor fire resistance. Therefore, other adhesive was used to strengthen concrete beams in flexure. Cement-based bonding material would be beneficial to produce strengthening system that is fire resistant, also it significantly lower the cost of retrofitting on existing structures.
An experimental investigation was conducted on shear behaviour of RC beams that are strengthened using BFRP external reinforcement with epoxy resin as bonding agent. This experimental test program is set up to test the shear capacity of beam specimens. For the analytical verifications, ACI 440 guideline and TR55 guideline was used to verify the influence of externally bonded FRP reinforcement. The experimental investigation was conducted in two phases and consisted of 14 full-scale ordinary RC concrete beams, 5 of them were used as reference beams and the remaining 9 were strengthened with BFRP sheets. Phase three is an experimental investigation conducted on 8 full-scale ordinary RC concrete beams strengthened in flexure with a cement-based bonding material.
The shear testing conducted has shown that by shear strengthening RC beam with external FRP reinforcement using epoxy adhesive, the load carrying capacity can be increased. The experimental results did compare well to the calculations based on standards, but overall the use of BFRP resulted in increased shear capacity.
The flexural testing conducted showed that excellent bonding properties can be achieved by using several types of cement-based bonding material. The mixtures generally included Portland cement with silica fume (SF) to increase strength and super plasticizer (SP) to reduce the water content and to achieve the workability. Three different mixtures were used, including silica fume (SF), super plasticizer (SP), synthetic micro fibres and acryl.
Two design models available in current design guidelines were used to compute the BFRP effective strain and the shear contribution to the shear load carrying capacity of the BFRP shear strengthened beams. The experimental results were compared to analytical results for both shear and flexural strengthening.