Written by Alyssa Burley.
Project Cornerstone educated nearly 210 sixth-grade students about the importance of construction aggregates (i.e., sand, gravel and crushed stone) at Greenfield Middle School on March 5th and 6th, 2015.
The in-class activities included three sections: a background presentation about the local construction aggregates industry, a sieve analysis, and a concrete making activity.
For the sieve analysis, students develop a hypothesis for which type of sand (i.e., river or beach) is best suited for making concrete based on the knowledge gained during the presentation. Half the class tests a sample that includes river sand while the other half tests a sample with beach sand. Each group pours their sample into the top of the sieve (which has a series of screens that sorts the material by size as it passes through each screen). The students weigh the amount of material captured by each screen and calculate its percentage of the whole. Samples with the least amount of very fine sand are best suited for making concrete.
The concrete making activity is more than just an art project. Students must mix the sand, gravel, cement and water in the correct proportions in order for the concrete mixture to cure properly. As they add water to the sand, gravel and cement mix, the students witness the chemical process, known as hydration, which changes the aggregate and water mixture from a liquid into a solid.
While the concrete was still in a liquid form, the students poured the mixture into various molds like footballs, trucks, flowers, butterflies and more. Once the concrete was hard, it was removed from the molds and given to the students to take home.