Relaxation curves.

<p>All samples are represented (grey points); the dark line represents the bi-exponential fit for sample <i>n</i>°12. The axial stress <i>σ</i> (in MPa), normalized with the maximum axial stress of the sample <i>σ</i>_<i>max</i> obtained at the end of phase 1 is displayed against time (in s). The following function was used to fit the relaxation curves: <i>R</i>² > 0.983. It has to be noted that one sample relaxation stopped at 200 s for technical problem. We assume that the relaxation was long enough to perform a bi-exponentional fit.