## 3 Results and Discussion
### Mechanical Fracture Parameters  
The mechanical fracture parameters determined during the specimen's hardening based on direct evaluation of records of fracture test in the form of the \(F-d\) and \(F-CMOD\) diagrams are presented in this section (Figure 8). These results are supplemented by parameters determined based on identification using an ensemble of ANNs. The number of specimens taken into the account for parameters evaluation is evident from Figure 5 where only the correctly recorded diagrams are presented. The results obtained by direct evaluation and identification are marked as 3 PB and ID, respectively. The value of modulus of elasticity determined by direct evaluation is about 33.5 GPa and is the same during the whole period of hardening (see Figure 8a) when the variability of the results is taken into account. The modulus of elasticity determined by identification is about 3 GPa higher for all investigated ages of specimens. The variability of results is higher for values determined by the method of identification. The modulus of elasticity of the investigated AAS composite at the age of 90 days is slightly higher in comparison with the OPC material with a similar w/b ratio and the same sand s/b ratio [39]. The modulus of elasticity at the age of 530 days is more than two times higher in comparison with the AAS composite activated by waterglass [42]. Nevertheless, the AAS composite activated by waterglass was stored at a lower RH of about 60%, i.e., in more severe conditions with the risk of microcracking and limited hydration process. The fracture energy value gradually increases during the whole period of hardening (see Figure 8b). The highest value of about 70 J/m\({}^{2}\) is observed at the specimen's age of 530 days, which reaches more than 200% and 60% higher values in comparison with value at the age of 40 and 160 days, respectively. The same trend of development of this parameter during the hardening is observed for both the direct evaluation and identification. In the case of the AAS composite, the stability loss during the loading did not occur; therefore, the post-peak parts of \(F-d\) diagrams are taken into consideration when the fracture energy is calculated, unlike the OPC material with a similar w/b ratio and the same s/b ratio [39]. The fracture toughness value gradually increases during the whole period of hardening (see Figure 8c). The same values were obtained for both used fracture models. The highest value of about 0.73 MPa\(\cdot\)m\({}^{1/2}\) is observed at the specimen's age of 530 days, which reaches about 56% and 28% higher values in comparison with value at the age of 40 and 160 days, respectively. A similar value of fracture toughness is observed for the AAS composite activated by a combination of sodium carbonate and hydroxide [42]; however, only the value at the age of 28 days is presented in this literature. The fracture toughness of the investigated AAS composite at the age of 90 days is about 30% lower in comparison with the OPC material with a similar w/b ratio and the same s/b ratio [39]. Nevertheless, both composites were stored at a lower RH of about 55\(-\)60%. The resistance to stable crack propagation is represented by fracture toughness ratio: the initial cracking toughness \(K_{\text{lc}}\)\({}^{\text{ini}}\) to unstable fracture toughness \(K_{\text{lc}}\)\({}^{\text{un}}\) ratio. The fracture toughness ratio gradually decreases during the period of composite hardening (see Figure 8d). A similar trend is also observed for load ratio, which represents the ratio of load \(F_{\text{ini}}\) at the outset of stable crack propagation to the maximum load \(F_{\text{max}}\). A little bit lower fracture toughness ratio value is observed for the AAS composite activated by a combination of sodium carbonate and hydroxide stored at a lower RH of about 60% [43]. The compressive strength value gradually increases during the whole period of hardening (see Figure 8e).