Fibre Pullout Behaviour of Fibre-Reinforced UHPC with TPE-coated Fibres

The use of micro fibres as reinforcement in Ultra-High Performance Concrete (UHPC) enhances its mechanical properties, especially the flexural and tensile strengths and a ductile post-failure behaviour is achieved. To guarantee this positive influence, an optimal bonding between fibre and cementitious matrix is necessary. To achieve this, a coating of fibres with a thermoplastic elastomer is proposed in this study. Pullout tests with brass coated steel and stainless steel fibres with and without a TPE-coating (thermoplastic elastomer) were carried out as well as flexural strength tests of UHPC reinforced with the same fibres. For better comparability between pullout and flexural strength tests, a modified pullout setup, allowing inclined fibre pullout, was developed and used in this study. The coating increases the adhesive bond between fibre and UHPC matrix indicated by straight fibre pullout. However, pullout tests with inclined fibres reveal contrary results, displayed in the flexural bending tests.