• How Much Highway? student handout
• Access to the Internet, and to the Minerals Education Coalition website (MineralsEducationCoalition.org/esw) 
• Access to color printer
• Straight edge/ruler
• Protractor
• Paper and pencil

Aggregates (stone, sand, and gravel) are among the most mined materials in the world. Mining engineers plan and manage aggregate quarries. A coarse aggregate—such as natural gravel or crushed stone—is used along with a fine aggregate (such as sand), Portland cement, and water to produce Portland cement concrete, a common cement used worldwide.

Determining the size of conical-shaped stockpiles of coarse aggregate is important in ensuring that an adequate amount of coarse aggregate is available to be mixed for the amount of concrete needed for a specific purpose, such as road paving. A basic mix recipe of one part Portland cement to two parts sand to three parts gravel (i.e., 1: 2: 3) has been used historically for many applications in construction. Aggregate for concrete is often mined locally due to the expense of transporting heavy aggregates.

Student Challenge

Students apply aspects of ratio and proportion and geometry to calculate how much highway pavement can be made from Portland Cement concrete.

Success Criteria

• Explain the meaning of natural angle of repose of earth materials.
• Show how to use stockpile measurements to calculate the volume of a conical shaped stockpile.
• Describe the importance of aggregates and their uses in daily life.
• Calculate how much Portland Cement concrete highway pavement may be constructed from a stockpile volume of coarse aggregate, in this case natural gravel.
• Explain how Portland Cement concrete is made and placed.
• Demonstrate an understanding of the meaning of and use of technical terms such as natural angle of repose, coarse aggregate, fine aggregate, fines, Portland Cement, Portland Cement concrete and mix design.

1. Provide students with some basic information about aggregates (aggregates used in construction are typically mixtures of stone, sand and gravel). A particularly popular concrete, known as Portland Cement concrete, is a mixture of coarse aggregates—natural gravel or crushed stone with particle diameters that are between 3/8 and 1.5 inches—fine aggregates, Portland cement, and water.
2. Organize the class into teams of 2 or 3 students and distribute the How Much Highway? handout to each team. Provide teams time to work together to complete the three sets of calculations.
3. Once the allotted time has passed, walk through the calculations as a class, further exploring any place that students may have struggled with. Did all the teams come up with the same answer? If not, discover where teams might have gotten off track, and work through the calculations again until all teams derive the same answer.
4. Use the Guiding Questions to help students further understand and explore the concepts underlying their work.

1. How could knowledge of angle of repose help you plan for storage of materials in open or covered piles?
2. What would you build or do to limit the size of the base of a pile of one of these materials?
3. Are there rock quarries near you? If so, what kind of materials are mined there?
4. What types of mines and quarries are found in your state?