Rebound Coffee

Grade:

8

Teacher:

Laura Robinson

The purpose of this experiment was to figure out what percentage of sand replaced with spent coffee grounds in concrete would result in a stronger mixture. I was trying to redo my experiment from the previous year to have a more reliable way of testing the concrete strength while keeping it as an at home project. My hypothesis was that if I replace the sand used in concrete with SCG the mixture with 15% replaced will have the highest increase in strength. My experimental procedure consisted of collecting spent coffee grounds, creating each of the mixtures in separate molds, waiting for them all to cure, and using a rebound hammer to test the strength of the concrete. The sample included 4 different mixtures: the normal concrete mixture consisting of no coffee grounds, and mixtures replacing 10%,15%, and 20% of the sand with SCG. The manipulated variable was the amount of sand replaced with SCG in each mixture. The responding variable was how strong each mixture was. To measure the responding variable, I recorded 10 impacts from the rebound hammer of each mixture and put the results in a table. The results of the experiment was that the control mixture was the strongest. Some of the errors were how I was unable to properly pyrolyze the spent coffee grounds using my normal oven which would've likely changed the results drastically. My hypothesis was not supported. My findings could be useful for future constructions and people who want to reuse their spent coffee grounds in projects that involve concrete in a way that better helps the environment. In the future, I would like to reach out to companies to organize a way I could properly pyrolyze the SCG or do a different way of testing that could get slightly more accurate results than from a rebound hammer.

Project presentation