A short-lived early fall snowstorm dusted the site but higher then average temperatures have expanded our window for concrete work. Intermountain Builders and Precision Dirtworks, both local Lander contractors, have been coordinating grading for roads and parking and excavation for foundations. Conventional reinforced spread footings are poured between temporary wood forms, then removable steel forms create a cavity for cast in place stem walls.
In the old days, workers would move wet concrete or "mud" around in barrows, then shovel it into forms in a series of short lifts. With a pumper truck and a small fleet of cement trucks bringing a continuous supply of mud, a crew can pour more then 20 cubic yards (more then 77,000 pounds) of mud in a few hours. Green (a.k.a. uncured) concrete needs forms while it cures for the first two or three days, depending on what recipe is used. Amendments are added to increase content of post consumer waste, such as fly-ash, or to alter the range of tolerable temperatures or other environmental conditions required while the concrete cures. Our mix is green in a separate sense- our mix includes 50% recycled fly-ash, a by-product of gas combustion, which dramatically decreases the use of other inredients. It makes a slightly stickier product but is superior in strength. Concrete gains strength as it cures- after seven days, our mix of concrete can hold almost 2000psi and at 56 days, compressive strength increases to 4650psi.
When the forms come off, the fresh foundation walls will be clad with rigid insulation. We're using 100% recycled styrofoam for the majority of our exterior insulation below ground, enough to fill two semi trailers. Dirt will be backfilled against the foam and the finish grade is pitched to ensure rain is drained away from the walls. This foundation will support a two bedroom residence for a facilities staffperson who will live on site as soon as ten months from now.