Proper testing would require some special equipment including high pressure hydraulic presses with precision gauges for testing strength, drying equipment and precise scales for measuring moisture content, and precision devices for testing impact resistance. Reality being what it is, I neither have nor have access to such equipment. There is also a matter of time and funds for multiple testing of multiple batches over a long period of time. With these factors in mind, do not consider my tests as conclusive.
Removing the form the following morning went very well, still soft but plenty firm enough to hold its shape. As you can see from the first photo, soft means soft enough to cut with a drywall broad knife. Being able to cut the material into blocks, shapes, etc., was the first test and went as expected from the information available. Certainly not what would be expected from regular concrete. The original pour was 6ft by 16in by 3in, with the cut leaving 2ft and 4ft lengths for further testing. I then cut a 1in strip from the end of one of the blocks in order to have smaller pieces to test.
Patience is a virtue, though not necessarily one of mine, thus my first big mistake with this project. Though anyone who has worked with concrete knows it is not really solid after 12 hours, my impatience got the better of me and I lifted up the longer section. I found it to be very light, however, it also flexed as I lifted it. Realizing my mistake, I quickly lowered it back down, but the damage had been done. After a week of cure time, the cracks formed by my mistake were painfully obvious as seen in the photo. Needless to say, after such a blatant error, I didn't touch it again for a full week. Lesson learned (at least for this time).
Testing compression strength requires equipment that I do not have access to. However, while I can't test the actual compression strength, I am equipped to make simple comparisons. Taking a small piece of aircrete and a similar size piece from the side wall of a concrete block for comparison, I placed them in a 20 ton press to see how they compared. First, the piece of concrete block. Ten full strokes of the jack handle were required for it to fail. As you can see from this photo, it broke up nicely (and suddenly, I might add).
Next, the aircrete went through the same process. Seven full strokes of the jack handle ended in failure of the sample. This sample compressed slightly, then began to flake before breaking. It did not shatter like the concrete, but did fail with less pressure. Looks like the aircrete is not as strong, but there is also the consideration of cure time. The aircrete had only cured for 1week, while the concrete block has been around for at least 50 years (yes, I know where it came from and remember when it was purchased).For an impact test, I had nothing for comparison other than personal experience and my own subjective opinion. Simply put, I beat one of the larger pieces with an 8lb. hammer to see how it held up. It broke up more easily than I had hoped, and before breaking, it dented. Yes, dented! I was not expecting that. As for breaking easily, I will also note that looking at the break, I found that the aircrete was still moist inside indicating that it is not fully cured.
I also did a couple of other tests. As previously mentioned, aircrete is light weight. It is in fact very lightweight, so I pitched a chunk in a bucket of water. Yes, it does float.
When I mentioned this type of material to my daughter, one of her questions was about flying debris during a tornado. Having no answer to such a question and not willing to wait for a tornado to test it, I devised another test for high velocity impact. After placing a piece in front of a good back stop. I shot it with a couple of calibers of firearms at a range of 15 yards. The bullets went completely through the 3in. thick sample. Though I consider this a fail, in all fairness, at least it didn't shatter. Also, with the thickness of a house wall and more cure time, it might do better.
After testing, some of my skepticism has been eased. Compression test comparison wasn't bad considering the short curing time. The same is true for the impact test. High velocity impact tests are a concern and I certainly wouldn't consider it suitable for a combat zone. Weight (or lack of it), and ease of free form use are great. As for floating, not sure how that is necessarily good or bad. In the event of a major flood, would the house float away? A thought for laughs at least.
As stated above, these tests are not precise or conclusive, but simply my attempt to gain enough information to make an informed decision on aircrete as a possible building material. These tests were done at 1week of cure time and I will be doing follow up and posting updates when it has cured more.
If you have any questions or suggestions for further testing, please let me know in the comments. I look forward to all response.
Thank You.
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