Unexpected Result During Fire Resistance Test (final Test)

That’s the second part of refractories test. After that test I will choose the best material for my new metal melting furnace project. This particular experiment consists of 2 smaller tests

During the first test, I made such mixtures:

1. Fire clay – 100%;

2. Fire clay – 40%; Grog – 40%; Graphite dust – 20%

3. Fire clay – 40%; Grog – 50%; Graphite dust – 10%

4. Fire clay 40%; Grog – 50%; Graphite dust – 5%; Mineral wool – 5%

5. Fire clay – 40% Grog – 40%; Graphite dust – 10%; Alabaster – 10%

6. Alabaster – 50%; Sand – 50%;

7. Cement – 50%; Sand – 50%

I put samples into the oven to dry them:

- 5 hours +50 C° (122F°);

- 2 hours +100+180 C° (212-356 F°);

- 2 hours +250 C° (482 F°).

All samples survived except one. Sample #6 (Alabaster/Sand – 50/50%) was damaged during the air drying.

First part of the test was with gasoline torch. During it samples didn’t get any damages.

Second part of the test in the smelting furnace was much more destructive. The process took about an hour. In my opinion, the temperature was more than 1200 C° (2192 F°). All samples were damaged. Only the sample #3 got minor damages. Therefore, in this test it’s the best result.

Nevertheless, the sample #7 (cement/sand – 50/50%) was damaged but held the shape. Therefore, I wanted to make one more test where cement could be one of the main ingredients.

During the second test, I made samples:

1. Cement – 50%; Sand – 25%; Grog – 25%;

2. Cement – 50%; Fire clay – 25%; Grog – 25%;

3. Cement – 40%; Sand – 17.5%; Grog – 15; Fire clay – 27.5%;

4. Cement – 22.5%; Sand – 27.5%; Grog – 22.5%; Fire clay – 27.5%;

5. Cement – 22.5%; Sand – 22.5%; Grog – 22.5%; Fire clay – 27.5%; Graphite dust -5%

All steps of the process were the same as in the first experiment.

Finally, in the smelting furnace samples started melting. I think that the problem is the sand and the cement.

I used the river sand and not the silica sand. Silica sand as I now sustain much higher temperatures than river sand.

I’ve made a decision to use fire clay/grog/graphite dust (40/50/10%) in my new furnace.