BEFIB2012 – Fibre reinforced concrete Joaquim Barros et al. (Eds) © UM, Guimarães, 2012 UFRG – UNIDIRECTIONAL FIBRE REINFORCED GROUT AS STRENGTHENING MATERIAL FOR REINFORCED CONCRETE STRUCTURES Rita Gião 1* , Válter Lúcio 2 , Carlos Chastre 3 and Ana Brás 4 1 Civil Engineering Department, Lisbon Superior Engineering Institute, Polytechnic Institute of Lisbon, ISEL/IPL, 1959-007 Lisbon, Portugal, anareis@dec.isel.ipl.pt 2 Civil Engineering Department, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, FCT/UNL, 2829-516 Caparica Portugal, vlucio@fct.unl.pt 3 Civil Engineering Department, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, FCT/UNL, 2829-516 Caparica Portugal, chastre@fct.unl.pt 4 Civil Engineering Department, ESTBarreiro/IPS, Polytechnic Institute of Barreiro, 2839-001 Barreiro, Portugal, ana.bras@estbarreiro.ips.pt Keywords: Unidirectional Steel Fibres, Fibre Reinforced Concrete, Strengthening, Experimental Summary: The present study is part of an extensive research project, where the main objective is to evaluate a strengthening solution for reinforced concrete structures using a small thickness jacketing in the compression side of the RC element with unidirectional fibre reinforced grout - UFRG. For this purpose a high performance cementitious grout reinforced with continuous and unidirectional non-woven fibremat has been developed. It was expected that the use of these type of fibres allowed an optimization of its percentage and orientation. Besides, for continuous fibres (with an aspect ratio, defined as the length-to-diameter ratio, l/d=∞), the composite should attain higher tensile strength since the fibre embedment length is enough to prevent fibre pullout. The experimental campaign included a set of preliminary tests that allowed the design of the fibre reinforced grout, sustained with rheological parameters [7] and mechanical characterization tests of the materials. Finally, an experimental campaign was carried out in order to proceed to the mechanical characterization of the unidirectional fibre reinforced grout. Compressive tests were conducted in small thickness tubular specimens that enable the determination of the compressive strength and the static modulus of elasticity of the material. The tensile strength of the material was obtained using splitting tests of cubic specimens (according the standard DIN 1048-5). The experimental results are presented and analysed. 1 INTRODUCTION In the last decades, research efforts have been made in order to improve the performance of conventional concrete that have promote a technological development and an improvement of its mechanical behaviour. For instance, the use of superplasticizers, among other additives, that allow the production of a