Weight of Concrete pad ?

Brad White_185

concrete, when cured, weighs 140 lbs. per cubic foot and so-called "light-weight" concrete weighs about 25% less. Water weight adds about 12 to 16 lbs. per cubic foot but as you note, evaporates in the endothermic process.

amhplumb_2

Weight of concrete pad?

Fellow Wallies, I recently poured a concrete pad for a new unit and was asked a question by my customer that I never had to give much thought to in the past? Further, it's not critical now either, just a point of interest! She wondered if the total weight of the pad would be that of the five 80lb bags of dry concrete ready-mix or does it include the weight of some or all of the added water to mix it. It has always been my understanding that concrete is a chemical process in which the de-hydrated portland cement bonds with the sand and gravel as it is mixed and re-hydrated and "cured". During the "curing" process, does all or some of the water evaporate into the surrounding air , or does it change state and remain in the "cured" concrete? This would be good to know in the future should I have a job in which total weight would become a critical issue. Although it hasn't in the past 30-years! Today's a catch up on paperwork day!!!Thanks.

Maine Doug_74

I thought

concrete gave off heat when curing which would be exothermic??

Brad White_185

You are right!

I always get those confused, "endo" meaning internal and "exo" meaning external. I always take "endo" as being "internally generated" as opposed to the heat being sent externally ("exo"). But looking it up, the usage is as you describe.

The process itself in mass is pretty neat though. I recall a large pour of magnetite concrete for a Proton Therapy center with walls two meters thick and three stories tall. The concrete took about six months to come to equilibrium.

Thanks, Doug!

amhplumb_2

Thanks!

Thanks!