Using Steel Fibred High Strength Concrete for repairing Normal Strength Concrete beams and slabs

Steel Fibred High Strength Concrete (SFHSC) is an effective material that can be used for repairing concrete elements. The design of Normal Strength Concrete (NSC) elements that should be repaired using SFHSC can be based on general concepts for design of two-layer beams, consisting of SFHSC in compressed zone and NSC without fibres in the tensile one. It was previously reported that such elements are effective when their section carries rather big bending moments. Steel fibres added to high strength concrete increase its ultimate deformations due to the additional energy dissipation potential contributed by the fibres. By changing the fibres' content, a required ductility level of the repaired element can be achieved. Providing proper ductility is important for design of structures to dynamic loadings. The current study discusses experimental results that form a basis for finding optimal fibre content yielding the highest Poisson coefficient and ductility of the repaired elements' sections. Some technological issues as well as distribution of fibres in the cross section of two-layer bending elements are investigated. The experimental results, obtained in the frame of this study, form a basis for general technological provisions, related to repairing of NSC beams and slabs using SFHSC.