Experimental validation of the short- and long-term structural performance of macro-synthetic fibre reinforced concrete beams with minimum longitudinal reinforcement

Fibre reinforced concrete has become a recognized and accepted material for structural applications. This has been recognized by its acceptance into international design codes, such as the fib Model Code 2010 and 2020. Nonetheless, certain national standards, such as the Eurocode 2, adopted by CEN member states, so far only consider the use of steel fibres. However, macro-synthetic fibre reinforced concrete (MSFRC) is being increasingly used, warranting its inclusion in such standards. This works aims at supporting the initiative of CEN/TC 250/SC 2/WG 3 for producing a CEN Technical Specification for MSFRC. For this purpose, a three-year experimental campaign was carried out to characterize the mechanical properties of MSFRC with different fibre types and amounts, to test short- and long-term structural behaviour of steel rebar macro-synthetic fibre reinforced concrete (SRMSFRC) cracked elements and to conduct constitutive modelling and analysis of the results. The results reveal a significant contribution of fibres to the flexural strength of full-scale beams at both 3 and 9 kg/m 3 polypropylene fibre contents. In terms of sustained load tests, the overall deflection behaviour, analysed on a normalised level (total deflection/initial deflection) evolves similarly between SRMSFRC and reinforced concrete (RC) beams. Finally, the analytical predictions of SRMSFRC deflections demonstrate good agreement with experimental results, without the need to include any time-dependent properties of MSFRC. The experimental evidences reported in this study confirm that macro-synthetic fibres effectively enhance the flexural tensile capacity of SRMSFRC elements with minimum conventional steel reinforcement, both at short- and long-term, under sustained loading conditions. • Three-year experimental programme conducted on SRMSFRC elements under sustained load. • Short- and long-term testing performed at material and structural level. • Experiments point to a significant and sustained contribution of macro-synthetic fibres. • Analytical predictions of ultimate strength and deflections in good agreement with experiments.