TRC or CFRP strengthening for reinforced concrete beams: An experimental study of the cracking behaviour

• External reinforcement retains the high stiffness, even though cracks initiate.
• CFRP and TRC external reinforcement increases the number of cracks.
• CFRP and TRC external reinforcement reduces the crack widths.
• The only influence of precracking is the instant opening of existing cracks.

Cement-based composites are emerging as strengthening and repair materials for concrete structures, because of their advantages related to fire safety and their relatively low cost. To be able to compete with the existing Carbon Fibre Reinforced Polymer (CFRP) solutions, the cement matrix must be reinforced with textiles in high fibre volume fractions. Extensive experimental verification of the contribution of these Textile Reinforced Cements (TRC) as external reinforcement with regard to the load bearing and cracking behaviour of reinforced concrete beams is still necessary. This paper compares the existing CFRP and TRC solutions with a strong focus on the cracking behaviour by performing seventeen bending experiments monitored with Digital Image Correlation (DIC). It shows that the TRC-reinforced beams exhibit a similar cracking behaviour to the CFRP-reinforced beams. Moreover, precracking of the concrete beams before the application of the external reinforcement reduces only the initial high stiffness, but does not influence the cracking behaviour, failure mode or ultimate load. These test results indicate the relevance of non-precracked tests that have been performed in the past.