High performance fibre-reinforced cementitious composite (CARDIFRC) – Performance and application to retrofitting F.A. Farhat, D. Nicolaides, A. Kanellopoulos, B.L. Karihaloo * School of Engineering, Cardiff University, Cardiff CF24 3AA, UK Available online 3 March 2006 Abstract This paper describes first some of the recent performance checks on the high performance fibre-reinforced cementitious composite CARDIFRC and then its application to the retrofitting of damaged concrete beams. It is shown that an even dis- tribution of fibres throughout the bulk of the material is crucial to its excellent fatigue performance and to the reduction in the autogenous shrinkage strains. The distribution of fibres in beams, cylinders and strips is examined using computerised tomography imaging and traditional image analysis. Thin strips of CARDIFRC are used to retrofit damaged concrete beams which are subjected to thermal cycling. It is shown that neither the load carrying capacity of the retrofitted beams nor the bond between retrofit strips and concrete deteriorates with thermal cycling. The load carrying capacity of retrofitted beams is predicted with a model based on fracture mechanics, and the predictions are shown to be in good agreement with test data. Ó 2006 Elsevier Ltd. All rights reserved. 1. Introduction New types of concrete are being constantly developed in order to meet the increasing demand for improved mechanical properties and durability. These new types of concrete are widely known as high strength (HSC), high performance (HPC) and ultrahigh performance concretes (UHPC). The properties of such concretes show a substantial improvement over conventional concrete. However, the improved and densified micro- structure of these new types of concrete leads to a significant increase in their brittleness as well as in the vol- ume changes which occur during the hardening of the material, i.e. in autogenous shrinkage. Both these drawbacks can however be overcome to a large extent by the inclusion of large amounts of short steel fibre. Such fibre-reinforced concretes are called high performance fibre-reinforced cementitious composites (HPFRCCs). One such HPFRCC, known under the trade name CARDIFRC Ò is the subject of this paper. The mechanical performance of any HPFRCC depends to a high degree on the even distribution of fibres in the bulk of the material. Any regions with a low density of fibres or with no fibres are potential sites of weak- ness. The distribution of fibres in the mix depends not only on how the fibres are introduced into the mix but also on the shape of the object cast from CARDIFRC. 0013-7944/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.engfracmech.2006.01.023 * Corresponding author. Tel.: +44 2 20874934; fax: +44 29 20874597. E-mail address: Karihaloob@cardiff.ac.uk (B.L. Karihaloo). Engineering Fracture Mechanics 74 (2007) 151–167 www.elsevier.com/locate/engfracmech