Can’t seem to get the right mixture

  • Hi

    To start off I weighted the foam and it was 3oz for 1 quart. I then added 94lb bag of type 1/2 Portland to 7 gallons of water. I mixed thoroughly. I then added the foam up to about 30” high. Again mixing thoroughly all the way up. I then poured the mixture into my molds. It’s been about 18hrs and it is still soft. When does it began to harden? Did I not mix enough? Does it need to cure longer? Thanks


  • Hi Jason,

    I saw your post earlier when I was just starting to make sample blocks of Aircrete.

    So I cheated and asked a friend to make a spreadsheet for concrete amounts 10lbs and under since this part can be a bit tricky.

    The batch recipe used for batch number 1 was 5.22 LBS Portland CPC-30R, 3.22 LBS water and 1.56 LBS foam.

    Will let you know how it works out.


  • It has been 36 hours since making the blocks with the 5.22LBS cement recipe above. Molds used included tin trays, styrofoam bowls, and styrofoam blocks (bought at home depot). Result: The only viable blocks were the ones that we poured in the porous styrofoam blocks because the water was sucked out of the blocks which enabled the blocks to harden.0_1518887153409_aircrete blocks.jpg

  • Hi, i am new to this site but very interested in aac and have been for quite some time.
    Can you inform me as to the dimensions of your molds (LengthxWidthxHeight)? I am sure that maximizing the surface area of the pour will make for better drying times. This can be achieved with smaller pours into the same mold over a few days?
    I do not own a machine but you do! If you would not mind i would love to use you to collect data while you perfect the mixture.
    for example:

    1. if you save a small amount in a tupperware container and close it, how long can it last in a liquid form (incase you wanted to save some)

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