Hypothesis: Clay added with concrete mix will hold more heat than sand mixed with concrete mix.
Purpose: The experiment was meant to help the learner understand which of the three types of concrete could best store heat. Of the possible choices were the sample of standard Quikrete mix, Quikrete mix and clay, or Quikrete mix and sand. The experiment was carried out by drilling holes into each sample, putting them in an oven at 200°F for a set amount of time, then taking out the samples and every five minutes recording the respective temperatures.
Method:
1. Take three cups, fill up to ¾ with Quikrete mix
2. Fill three separate cups of water up to 1/5 of the quantities of Quikrete mix
3. Add the water to the Quikrete mix and stir until there are no chunks and the surface is smooth
4. Allow for the sample to dry (preferably leave for 24 hrs)
5. Drill holes into the center of each sample (1/4” deep)
6. Set an oven for 200°F, then put the samples onto a tray and leave inside for 15 minutes
7. After 15 minutes, take out the tray, record the temperature for each sample, and repeat every 5 minutes.
Results based on leaving the concrete samples in an oven at 200°F for 15 minutes
Hour |
Time (min.)
After Removal |
Degree of material (°F) |
Clay |
Sand |
Standard |
9:30 p.m. |
5 |
High* |
High |
High |
|
10 |
High |
High |
High |
|
15 |
101.7°F |
100.9°F |
101.3°F |
9:45 p.m. |
20 |
94.8°F |
93.9°F |
94°F |
|
25 |
Low** |
Low |
Low |
Results based on leaving the concrete samples in an oven at 200°F for 20 minutes.
Hour |
Time (min.)
After Removal |
Degree of material (°F) |
Clay |
Sand |
Standard |
10:40 p.m. |
5 |
High |
High |
High |
10:45 p.m. |
10 |
High |
High |
High |
|
15 |
105.9°F |
102.9°F |
104.9°F |
|
20 |
98.2°F |
95.3°F |
97.1°F |
11:00 p.m. |
25 |
92.1°F |
90.1°F |
91.6°F |
|
30 |
Low |
Low |
Low |
*Values too high to record with thermometer
**Values too low to record with thermometer
Conclusion: Based on the results of each trial, the concrete mix with clay added held the most heat over time compared to the other two samples. An explanation for this would be because of the specific heat capacities of the clay and sand added to the concrete mix. While sand has a specific heat capacity of 0.8 kJ/kg °K, which is close to the value of concrete, clay has a specific heat capacity of 0.92. Despite the sample with sand and concrete mix being a more dense material, the sample containing clay is a more suitable thermal mass because more heat energy was gained during the experiment. This is related to the formula Q = cmΔT, where Q is the heat add, c the specific heat capacity, m the mass of the material, and ΔT the change in temperature.