The first of what will be many concrete trucks delivered concrete for the foundation footers today. The first half of the foundation, the part that is 12 feet underground used 17 yards of concrete. The concrete was poured into the CertainTeed Form-A-Drain molds. This concrete recipe as all concrete used in this house is mixed with fly ash in place of portland cement.
Because the concrete is used in the foundation, a heavier grade or density of concrete is used. This is measured by “slump” value. In this case we used a 4” slump. While not a technical term, slump values are commonly used to measure the thickness or consistency of the mix.
Slump values are calculated by a simple, ancient method. A 12 inch cone is filled with the concrete and then lifted. Like a wet sand castle the concrete will slump somewhat when the cone is lifted off the sample. The distance of drop or “slump” from the original 12 inch height is measured. A runny mix will slump more than a dense mix.
For foundation use, you want a denser mix with a smaller slump. For the concrete used inside the ICF walls, we’ll use a thinner or higher slump value mix.