AirCrete compression test

  • Do you have a real compression test - something in kg/cm2 or psi? I wouldn't call this a compression test - and you cracked the block driving onto it - in a test, this is a first failure. What is really needed if we are going to be sure we have adequate strength so that our homes don't crack, is some numbers so we can be sure we design to prevent failures.

    This "test" shows a BMW - what is it's weight? A big BMW weighs 2000 kg, or 4300 lbs. Each tire, if the weight is evenly distributed (it's close) then has 500 kg (1,100 lbs.) of force. if we assume the tire contacts the block in a 10cm x 10 cm area (4" x 4"), then we have a compressive force of 500/100 kg/cm2 or 5 kg/cm2 or 71 psi.

    5 kg/cm2 or 71 psi is extremely weak concrete! This can also be expressed in Mpa (mega-pascals), and is commonly used to express compressive strength. 5kg/cm2 is 0.5 Mpa. Good foamed concrete should be on the order of 3 to 10 Mpa or 30 to 100 kg/cm2 or 400 to 1400 psi.

    You should test your recipe, and be sure you do not use too much water! The water to cement ratio is critical for strength and low shrinkage. You don't want your new home to crack, so do some homework before you set off to build something. Recipes in the world of concrete are called "mix designs". Here's a link to some mix designs from a reputable source:

    There is a lot to think about before you start building. Doing engineering research before you jump in and start building will save you a lot of tears, heartache and money. You don't want to work your butt off building something just to see it start crumbling the first time you get a strong wind or thunder shakes your house.

  • Major Contributor

    @K2 You are completely right in your assesment. You also have to take into consideration that this is something that was built in Philippines. I guess they did not require engineering specs there and that it have been built like an accessory building. This is akin to the mini house movement, that is not allowed in many states because of regulations. I guess a real solution lies somewhere between this foamed celular concrete and a better reinforced version. This mix should have some sand, and be made with magnesium oxide concrete, which is stronger. I would also look for a better foamer that is more stable and last longer and reinforce with basalt rebar to avoid rust in the future. As I have said before, a sandwiched structure with the celular concrete in the middle, then an external layer of regular full strengh shotcrete and an internal layer of magnesium oxide cement would make for the ultimate structure. When I finish my test subjects I will send them to an engineering firm to do a proper compression and tensile strengh test and post some results. I have too many projects now but will definitely share when I finish mine. The ones they do use a fiber to reinforce the celular concrete,but still it would need a proper test to get to final numbers. I think this type of material is stronger than wood, but not stronger than regular concrete. Eventually I will have my answer and will share here.

Log in to reply