## 4 Conclusions  
Autoclaved aerated concrete (AAC) block is used in the construction of load-bearing and masonry walls due to its low thermal expansion coefficient, high fire resistance, and low weight. However, the low strength of materials and the heterogeneity of the material lead to the vulnerability of AAC masonry walls under external loads. To reduce the potential hazards in the structure and enhance the safety level, it is necessary to investigate the dynamic responses and failure of AAC masonry walls under explosive loads. This study aimed to investigate the behavior of AAC walls under blast loading. Therefore, the specifications of the materials required for modeling were first determined through experimental tests. Then, by modeling and analysis of the AAC walls in ABAQUS/Explicit, the behavior of these walls was investigated under blast loads. The main outcomes are as follows:  
* Considering the weight of TNT used in a short distance (R = 2 m), it was observed that very large local stresses were created in the wall, which caused the wall to collapse in a very short time. It should be noted that at distances of less than 2 m, the wall models diverged at the very first moments. Therefore, the analysis and presentation of their results were avoided here. * With the increasing charge weight, wall performance degraded. The stress level in the case of an explosive charge weight of 7 kg TNT increased by about 10% compared to that for 5 kg TNT. It is important to note that the walls modeled in this study under a charge larger than 7 kg TNT had a rapid failure in the initial moments. Therefore, considering the typical values of charge weight in the explosion events of hand grenades and suitcase bombs (about 20 kg-TNT) [72], it can be stated that masonry walls made with AAC do not have a good explosion resistance and would need retrofitting. * Some retrofitting methods in masonry walls could involve using CFRP coating, steel wire mesh, and laminating. In addition, polyurea and polyurethane coatings, using  
Figure 12: Base shear of the wall with thicknesses of 15, 20, and 25 cm. steel sheets, aluminum foam, and engineered cementitious composites, are suggested for masonry units that can be applied to walls made with AAC. * With the increasing charge weight and decreasing stand-off distance, the wall displacement increased significantly, so that at a distance of 2 m, the displacement was several times that for the 5- and 10-m distances. In the walls with thicknesses of 15, 20, and 25 cm, the performance was also observed to be the same. As the amount of TNT increased, the stress values increased, and more damage was observed in the walls. * The thickness of the walls was very effective in reducing the explosive demand force. For example, for a wall with a thickness of 15 cm, compared to that with a thickness of 25 cm, the base shear values induced by the same explosion were about 10 times higher. To complete this study and achieve practical findings, complementary studies will be executed on construction units made of AAC blocks, including AAC walls reinforced by various methods such as using horizontal and vertical rebar meshes. The effect of various characteristics of mortar and adhesive on the behavior of AAC walls under blast loads will also be investigated. It should be noted that the modeling of the walls built with AAC blocks in ABAQUS finite element software requires more extensive data and more detailed experiments. In particular, dynamic properties under high strain rates require further experimental and laboratory studies. Conceptualization, S.M. and E.N.F. ; methodology, S.M. and D.J. ; software, R.B.G. ; validation, R.B.G. ; formal analysis, S.M. and R.B.G. ; writing--original draft preparation, S.M. ; writing--review and editing, E.N.F. ; project administration, D.J. All authors have read and agreed to the published version of the manuscript. This research received no external funding. Not applicable. All the data used to support the findings of the study are included within the article.