Tuesday, July 24, 2007

Pouring and curing

July 23, 2007
The weather was ideal for pouring today. Not too hot, not too cold, overcast skies. Perfect for allowing the cement in the mix to hydrate without the water evaporating too quickly. The reinforcing looked great, anchor bolts were set, all bond outs (sleeves for routing utilities from outside the foundation to inside) were in place. The forms will be stripped in another day or two and following that the concrete slab in the basement will be poured. The concrete will be green for a couple of weeks and the initial cure time is 5-7 days. The mix we're using is a 3000 PSI mix which means if we were to test it at 28 days we would expect it to be able to bear 3000 pounds per square inch. Our concrete supplier typically mixes on the high side achieving an average of 3300PSI at 28 days for a 3000PSI mix. The concrete will continue to cure over a period of a year or more. It's critical, esp. with long walls like we have, to be sure to place control joints in the wall assembly. Control joints are joints tooled into the surface of the concrete (in our case they're small wedges placed on the inside face of the forms every 25' or so). These joints 'control' where the cracking occurs as all concrete will shrink during curing and thus cause cracking.

Only a few items remain for the foundation work to be complete. We'll be waterproofing the outside of the foundation and insulating with 2" polyiso to keep the cold out. The rim joists will receive a 2" coating of closed cell foam we're looking for R-14 and a way to seal off air movement which is the largest factor contributing to heat loss in any space. The radiant tubing beneath the subfloor won't perform very well if it's constantly battling air movement.

Temporary power service is on the way, waiting for Bangor Hydro to hold up their end of deal.

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