Autogenous deformations and viscoelasticity of UHPFRC in structures.: Part I:: experimental results

Autogenous shrinkage is the main driving force for internal deformations in ultra-high performance fibre-reinforced concretes (UHPFRC). Autogenous deformations and viscoelasticity are determined with free and restrained shrinkage tests for one kind of UHPFRC at an early age. The magnitude of free autogenous shrinkage is very strong during the first hours after hardening with 150 mu m/m at 48 h and 325 mu m/m at seven days. Long-term tests show that autogenous shrinkage becomes virtually constant at 90 days. The creep deformations of the fully restrained test amount to 60% of the free shrinkage deformations. Another experimental programme conducted on composite 'UHPFRC-concrete' beams shows that their time-dependent deformations are strongly influenced by the autogenous shrinkage of UHPFRC; however no visible cracking is induced in the structural elements.