It's Heating Up!
Objective: The purpose of this demonstration is to track the temperature changes that occur during the curing process of concrete.
Materials and Supplies:
- fresh cement-- use at least 100 grams for best results
- insulated container with a cover
- drinking straw
- plastic cup to hold cement
- Use 150 grams of cement and 75 mL of water in a 6 ounce yogurt container or other plastic container.
- Use an insulated 1 quart drinking mug or place the sample in a plastic bottle which is set inside a child's thermos. The thermometer is inserted into a one-holed rubber stopper which fits the thermos. Alternatively, the sample bottle can be placed in a box filled with Styrofoam. Another option would be to use a coffee can. The space inside the can could be packed with insulation, and the outside could be wrapped in pipe insulation. A hole can be cut in the coffee can lid to accommodate the thermometer.
- Fill the container with fresh concrete, using aggregate is not necessary.
- Fold over an inch of the drinking straw and tape closed. Insert thermometer into straw.
- Place the filled container into an insulated container. Insert the drinking straw housing the thermometer into the center of the concrete. Place the lid securely on the container.
- Record the temperature every 5 minutes for 20 minutes. Most of the change will occur in the first 15 minutes but will continue throughout the whole curing period.
- Repeat experiment using an admixture, such as calcium chloride, which speeds up the process (Use 2 % of CaCl2 by weight of cement )
- Attach the apparatus to a computer thermocouple that will record the temperature changes for the class over a day.
You should see an increase for 4 hours, most of which is observed within the first 15-20 minutes. The larger the mass of concrete the higher the temperature rise. 500 grams of concrete should give a rise of about 10[[ring]]C if well insulated. 150 grams of cement gave a 4 [[ring]]C change.