Stupid Question Of The Day!

[nightfighter]

Not stupid.
Depends on the aggregate mixed with the portland cement, ie. gravel vs limestone, clay, etc. We figure around 150 lb/ft3. The wet mix includes the water weight the aggregate absorbs when mixing. It also includes extra water that will be lost through drying. The concrete will hold approximately 70% relative humidity several months later, and thus the weight of the remaining water. If it is exposed to rain, etc. it will gain weight from that water it absorbs. Remember that it cures for years. The Hoover Dam is still generating heat from curing, and it was built in the 1930s!