Creep of Macro Synthetic Fibre Reinforced Concrete: Experimental Results and Numerical Model Calibration

The mechanical performance of fibre reinforced concrete presents aspects still under investigation, mostly those regarding the long-term behaviour. Even if creep and shrinkage are two well-known phenomena that characterize concrete, in case of FRCs, and in particular of macro-synthetic Fiber reinforced concretes (MSFRCs), there are no reliable models for predicting their long term-behaviour, because of the interaction between concrete, fibre creep and bond. In addition, temperature is a further variable to control since it affects the material performance. In this perspective, the present paper shows the experimental results of a large campaign of creep tests performed on macro synthetic fibre reinforced concrete specimens. The material tested had a compressive strength of about 55 MPa and it is reinforced with 8 kg/m3 of polypropylene crimped fibres. The experimental investigation is carried out by performing creep compression tests on cylinders and direct tensile test on notched cylinders. In addition, the tensile behaviour of the single fibre under sustained load is analysed. The tests were conducted in a humidity and temperature controlled chamber. Furthermore, the temperature was increased from 20 °C to 30 °C after a time of 50 days of testing in order to understand how this condition modifies the creep deformations evolution of the material. The paper shows also the initial calibration of a numerical model based on the Lattice Discrete Particle Model (LDPM) theory. The LDPM is one of the most validated theories able to reflect the actual coarse aggregate distribution of a quasi-brittle material, i.e. concrete. Currently this theory has been extended to include the fibres reinforcement. The aim of the big study presented would be to elaborate a predictive model for the MSFRCs accounting also for concrete and polymers long term behaviour.