Obi-Wan Adobe: Engineering for Strength
Making adobe bricks in Africa.Copyright 1999 US Peace Corps http://www.peacecorps.gov/wws/educators/enrichment/africa/countries/niger/NE0219.jpg
Students conduct an experiment to determine how varying the composition of a construction material affects its strength. They make several adobe bricks with differing percentages of sand, soil, fibrous material and water. They test the bricks for strength by dropping them onto a concrete surface from progressively greater heights. Students graph the experiment results and use what they learn to design their own special mix that maximizes the bricks' strength. During the course of the experiment, students learn about variables (independent, dependent, control) and the steps of the engineering design process.
Many construction materials can be classified as mixtures. The concentration of the various components in these mixtures determines how well the materials perform. For instance, the percent composition of water, cement, sand, aggregate, and various admixtures in concrete determines the strength of the concrete as well as other important qualities. Adobe bricks are another construction material that can be classified as a mixture. They are also one of the most widely used construction materials in the world today, particularly in developing countries. Determining the best proportion of the various components in these mixtures to minimize cost and maximize strength under specific conditions is the work of civil and materials engineers.
After this activity, students should be able to:
- Describe the steps in the engineering design process.
- Explain how engineers use experiments to develop strong construction materials.
- Explain the difference between a mixture and a solution.
- Explain the difference between an independent and dependent variable.
- Graph the result of a simple experiment.