## Appendix B  
As mentioned in point 3.2, to prevent plastic deformation during the test, all loading and unloading cycles were made elastic. For example, Figure 10 shows 3 of the 5 load-unload cycles of the test performed on the MW1 sample at 260 h. In the legend, \"2 ndLD\" means the loading of the 2 nd load cycle and \"2 ndUL\" the corresponding unloading. Table 11 shows the maximum deviations of the strains from the mean \(\Delta\varepsilon_{\text{max}}\), the maximum deviation MDev in the measured strains from cycle to cycle (measured in the relative modulus of elasticity of each strain gauge), the mean value of the modulus of elasticity E\({}_{\text{m}}\) (measured in the stress-strain trendline), the stress value \(\sigma_{0}\) at \(\varepsilon=0\), and the loading rate.  
First of all, it should be noted that the maximum stresses reached, cycle by cycle, are all below 6 MPa. Therefore, even assuming a compressive strength of around 25 MPa, this maximum represents less than 25%. As a methodology, it was decided to follow a cautious approach, having initially limited the stress to about 10% of an expected value of compressive strength (10 MPa), i.e., \(-1.0\) MPa. In this specimen, this limit has been progressively increased; 16 MPa on the 15 th day, i.e., 64% of the expected strength (25 MPa).  
The influence of the load ratio (Table 11) on the modulus of elasticity was also investigated. It is also important to say that in cycles 2 nd, 3 rd and 4 th, the speed imposed on the ServoSis compression machine was the same. The actual loading rate measured on the sample is slightly different due to the elastic-viscoplastic behavior of the neoprene sheets. Note that standard EN 12390-13 [30] indicates a loading rate of 600 \(\pm\) 200 kPa/s.  
With regard to the \(\Delta\varepsilon_{\text{max}}\) values, remember that the aforementioned standard requires that this deviation should be less than 20%. The values obtained in this test indicate the good centrality of the specimen. With regard to MDev, the standard limits it to 10%. All values presented verify this limit. However, the curiosity of these tests is that they showed higher values for the starting tests; in the first hours.  
Now the important issue of potential plasticizing. As can be seen in the stress-strain diagrams, the behavior of the specimen is perfectly elastic in the load-unload cycle, in such a way that cycle after cycle, the behavior always returns to the starting point, that is, residual plasticizing is not visible. It should be noted that the interval between the load lines (lower) and the unload lines (upper), in the central zone, depends on the order of the readings in the \"Data Logger\"; 1 st the load cell; then the 3 strain gauges; readings recorded at a frequency of 1 Hz. Consequently, during loading, a slightly higher strain would be recorded compared to the moment of loading and a slightly lower value during unloading. The slight increase in the modulus of elasticity at unloading results from this effect.  
Also, within this objective, \(\sigma_{0}\) represents a very important parameter to analyze. In fact, the trend lines of the stress-strain records (all lines have R2 determination coefficients greater than 0.999) indicate the intersection point of these lines with the ordinate axis a \(\varepsilon=0\). The reduction of this value, from one cycle to the next, shows some loss of resistance capacity of the specimen, in other words, some plastic deformation. For this test, the loss is approximately 0.1 MPa. In the last tests, this value exceeded 0.4 MPa. This effect was later observed after the specimen was broken.