Durability of a multiscale fibre reinforced cement composite in aggressive environment under service load

The LCPC has developed and patented a new ultra high performance fibre reinforced cement composite (UHPFRCC); the introduction of three steel fibre sizes leads to a multiscale fibre reinforced cement composite (MSFRCC) with multi-cracking and hardening behaviour in uniaxial tension (f_t more than 20 MPa). An innovative test of durability is presented. Pre-cracked thin slabs are damaged by fatigue under loading corresponding to service load (30 MPa in bending test) then maintained under bending at the same level. A part of these slabs undergoes 30 weekly wetting-drying cycles in a chloride solution (NaCl 5%, 20 °C). A reloading to failure is led. One notes an absence of corrosion in the micro-cracked area even for cover lower than 300 μm and a strength increase for pre-damaged slabs by fatigue. Under service load and in the presence of chloride water, a quasi-total recovery of initial stiffness is possible; it is accompanied by an increase of the pseudo-elastic behaviour. The development of a better matrix/micro-fibres synergy and a diffuse micro-cracking explains this result.