Extraterrestrial construction presents many interesting and new challenges. Unlike Earth, there are very limited naturally occurring resources readily available in extraterrestrial environments, such as the moon or Mars. Transporting large amounts of materials from Earth is cost prohibitive. Thus, this work focuses on a novel class of composites for use in limited resource environments: Biopolymer-bound Soil Composites, or BSC (Figure 1). For space applications, the term regolith is used to refer to the loose soil-like material on the Moon, asteroids and other planetary bodies. The composites are produced by mixing soil, water, and a biopolymer binder (protein or other biopolymer) to create a strong, versatile composite with compressive strength comparable to that of ordinary portland cement concrete but with a microstructure that greatly differs from it (Figure 2).
Figure 1– BSC 1-inch diameter cylinders made with Lunar Regolith Simulant (Left) and Graded Sand (Right) on top of the unbounded soil.
Figure 2– Comparison of the microstructure of BSC with cement mortar. On the left, a representative 2D slice of a 3D MicroCT image of protein-bound sand taken at a voxel resolution of 1.76 µm. On the right, a representative 2D slice of a 3D MicroCT image of Portland cement mortar taken at a resolution of 1.2 µm (Diamond and Landis 2007). Images have been modified so that they are displayed at the same scale.
This research project focuses on multi-scale framework to model the composites' response to fracture in order to design a durable material that can resist extreme environments (Figure 3). At the nanoscale, nanoindentation is used to obtain the mechanical properties of the dry protein after dissolving in water and desiccating. At the microscale, the creation of Statistically Equivalent Periodic Unit Cells captures the interactions between soil, protein and voids. Virtual tests are then used to obtain basic mechanical parameters. At the mesoscale, a Rigid Body Spring Model (RBSM, Nagai et al, 2005) is used to simulate fracture using the homogenized properties obtained at the microscale. At the macroscale, triaxial testing and digital image correlation tests are used to corroborate and modify the simulations. The final goal of this project is to have a robust computational simulation that can enable the prediction of the mechanical properties of the BSC materials to be used to design future structures on the Moon, Mars or other celestial bodies.
Figure 3 – Proposed framework for multiscale modeling of protein-bound soils.
Other referenced works:
Diamond, S., and Landis, E. (2007). “Microstructural features of a mortar as seen by computed microtomography.” Materials and Structures, 40(9), 989–993.
Nagai, K., Sato, Y., and Ueda, T. (2005). “Mesoscopic simulation of failure of mortar and concrete by 3D RBSM.” Journal of Advanced Concrete Technology, 3(3), 385–402.
Roedel, H., Rosa, I., Allende, M. I., Garboczi, E. J., Lepech, M., & Loftus, D.(2019) Prediction of Ultimate Compressive Strength for Biopolymer-bound Soil Composites (BSC) Using Sliding Wingtip Crack Analysis. Engineering Fracture Mechanics. Accepted Mannuscript.
Rosa, I., Lepech, M., & Loftus, D.(2018) Multiscale Modeling and Testing of Protein-Bound Regolith and Soils. In Proceedings of the 16th ASCE International Conference on Engineering, Science, Construction and Operations in Challenging Environments, Cleveland, OH: ASCE Publications.
Rosa, I., Roedel, H., Lepech, M., Loftus, D., & Garboczi, E. (2016). Three-Phase Statistically Equivalent Periodic Unit Cells for Protein-Bound Soils . In Proceedings of the 15th ASCE International Conference on Engineering, Science, Construction and Operations in Challenging Environments. Orlando, FL: ASCE Publications.
Rosa, I., Roedel, H., Lepech & M. D., Loftus, D. J. (2015) Creation of Statistically Equivalent Periodic Unit Cells for Protein-Bound Soils. Proceedings of the ASME 2015 International Mechanical Engineering Congress and Exposition, Nov 13-19 2015, Houston, Texas.
Roedel, H., Rosa Plata, I., Lepech, M., & Loftus, D. (2015) Sustainable Assessment of Protein-Soil Composite Materials for Limited Resource Environments. Journal of Renewable Materials, 3(3),183-194.