Diss. Stockholm : Kungliga tekniska högskolan, 2003

The research described in this thesis deals with the use of cement-based carbon fibre reinforced composites for strengthening of existing structural concrete. There is a large world-wide need for simple and reliablemethods to repair and strengthen aging infrastructure and buildings. The use of cementitious fibre composites offers several advantages over the existing methods. No other work on strengthening of structural concrete with cementitious composites reinforced with continuous high strength fibres wasidentified when the present work started in 1998. At present time, 2003, it still is a new technique and very littleresearch has been internationally reported. This work includes a literature survey describing the state of the art of the strengthening of structural concrete with cement based fibre reinforced composites. Due to the novelty of this technique no specially adapted materials are available and ready for use in cementitious composites. In order to make many small scale tests to optimize the composite, a new test beam has been developed. Several parameter studies have been done in this work to determine how different parameters, for example fineness of grading of the cement, additives, and fibre configuration affect the composite. Large scale tests of ordinary concrete beams strengthened with a cementitious fibre composite are reported. The compositeused was made of a polymer modified mortar and a unidirectionalsheet of continuous carbon fibres, applied by hand. Both flexural strengthening and shear strengthening were tested. A relatively new method for measuring strains with digital cameras was used on the shear strengthenings with a good result. It is concluded that the large scale tests have proventhat this method works and has great potential for future use. Design methods for strengthenings were studied and evaluated. It is concluded that design methods formulated for strengthening of structural concrete with carbon fibre reinforced polymers can be adapted also to cementitious composites by introducing an efficiency factor.