Influence of martian soil simulant on microstructural heterogeneity and mechanical response of martian concretes

Martian concretes have gained traction in recent years as a sustainable way to provide for life on Mars and possibly other planets. Despite several studies focused on unraveling the structure-property relationships in martian concretes, the influence of microstructural heterogeneity is not fully understood. We investigate the influence of the martian soil simulant on the microstructure and fracture response of martian concretes. To this end, martian concretes were synthesized using three selections of martian soil simulants. Advanced nanoscale mechanical testing modules were utilized, such as statistical nanoindentation and scratch testing, to investigate the elasto-plastic and fracture response at the nanoscale. A granular microstructure is observed for martian concrete with a distinct matrix-inclusion morphology, and with the fraction of the matrix being dependent on the martian soil selection. The basic matrix exhibits a Young's modulus of 18.83-25.24 GPa. The basic matrix also exhibits a microporous architecture, with a pitch size of 1-2 mu m. The fracture response of root martian concretes is nonlinear, with fracture toughness values in the range 0.48-0.7 Mpa m and the fracture toughness is highest when the matrix volume fraction is maximized. The matrix is very ductile with the dominant fracture micromechanisms being void formation and crazing. In turn, the grains are very brittle with microcracking being the dominant fracture micromechanism. Thus, our study links the microstructure and mechanical performance of martian concretes to the composition of the martian soil simulant. This study is important to issue recommendations for the design of high-performance Mars-friendly construction materials.