Testing the Strength of Martian Bricks
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For a colony of humans to survive and thrive on Mars, they will need to make the most of what is available on Mars. We know from prior space missions what the Martian ground cover looks like. In this project, you will see if this ground cover can be transformed into strong construction material.
The first requirement for construction material is that it is strong so it does not collapse under its own weight. Because the mass of Mars is about 10 times less than the mass of Earth, its gravity is only about 38% of the gravity on Earth. For that reason, a building on Mars would not need to support as much weight as the same building on Earth. Construction materials still need to be strong, however, to withstand the harsh climate of Mars and the bombardment of cosmic radiation.
The loose, rocky material that covers Mars' surface is called Martian regolith. True Martian ground cover is not available on Earth, but a very similar type of regolith can be found here. It is referred to as Mars regolith simulant (Figure 1), and can be purchased online from The Martian Garden. This simulant has a similar chemical composition to Martian ground cover and also has a similar grain size, making it ideal for your tests.
Figure 1. Coarse and fine Mars regolith simulant.
Regolith is a powdery substance. What could you use to hold regolith together to turn it into construction material? Scientists are experimenting with polymers—very long molecules that consist of repetitive units—to hold regolith together. Certain polymers are also effective cosmic radiation shields. Because school glue is a polymer and a binding material that is readily available, it is a great option for you to consider when making "regolith concrete," which can then be molded into bricks.
Once you have decided on the binding material to make your bricks, you need to decide on the recipe for your regolith concrete. Regolith comes in different grain sizes. The Science Buddies How to Build on Mars! science project idea compares bricks made with coarse regolith to bricks made using fine regolith. That recipe combines 7 tbsp. of regolith with 2 tbsp. of glue and utilizes a mini loaf baking pan in which to mold the concrete into bricks. What would you like to try as a recipe for your regolith concrete?
Figure 2. Fine (left) and coarse (right) regolith bricks ready to be tested.
As you consider your Martian building material, you should keep the relative amount of binding material low, as there would be significant cost in transporting this material from Earth. Can you calculate the percent of binding material per volume for your recipe? As an example, if your recipe calls for 2 tbsp. of glue for 7 tbsp. of regolith, your wet concrete will have (2 tbsp./(7+2) tbsp. ) × 100%, or 22.2% glue by volume.
Once you have your materials and recipe figured out, it is time to start testing. The construction industry uses several types of tests to determine the strength of construction materials like concrete. One such a test is the pull-out test, demonstrated in the Mungo MHDA Pull-out Test video. You will need to find the necessary equipment to do the test or build a rig yourself that uses the same principle, and thus tests the resistance against the same type of force.
As mentioned before, the Build for Martian Colonies! project compares the strength of different regolith cement recipes. You can also test how the strength changes when the material is repeatedly exposed to cold. The freezer is one way of exposing your building material to cold. Dry ice can provide a wider range of temperatures, but must be handled with care. Read up on how to safely handle dry ice and ask permission from an adult before using dry ice.
As you complete your project, do not forget to provide clear data tables and graphs, and if you can, add pictures of the construction material you created.
- Science Buddies Staff, (2020, Nov). How to Build on Mars! Retrieved November 1, 2020.
- Science Buddies Staff. (2020, July 8). How Does the Ratio of Sand to Cement Affect the Strength of Concrete? Retrieved November 1, 2020.
- Mishara, G.( n.d.) Pullout Tests on Hardened Concrete. The constructor. Retrieved October 10, 2020.
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