if the container is completely full of concrete, or possibly has a small air space?
I believe concrete bonds molecularly by the chemical reaction of its ingredients and water. I don't think it depends on needing air and there are types of concrete like building piers, that they can just dump into the water mixed and it will cure underwater. You can research it further.
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but doesn't the water inside the mix have to evaporate..?
Water is not a catalyst. The molecules of water react with the cement(lime, other chemicals, etc) and remains with the final product. If you ever seen them pour a concrete sidewalk or structure on a hot day, sometimes they will put a sheet of plastic over or spray with oil to keep the water from evaporating because it is needed to cure. And hose it down a few times to make sure it is wet to cure right. It all gets sucked into the bonding until you have a runny mess.
that article says excess water leaves the mix when hardening. and they spray water on the sidewalks to make them cure slower. The longer it takes for concrete to cure, thee stronger it is in the long run.
It's okay though, i found a way to do it with a little hole, and then just seal everything later.
although i'm still curious.
and if you try, the worst that may happen is you get a damp or sopping wet block of crumbly concrete if there is too much water in the sealed container.
Well cement heats up and absorbs oxygen as it cures. I think the bottle might implode. Haven't tried it yet though. Concrete DOES need oxygen to cure properly, we just cover concrete with tarps in order that it cures more slowly. The slower it cures, the stronger it becomes.
ONCE THE HYDRATION PROCESS STARTS BINDING THE AGGREGATE MATERIAL, MATER MOLECULES WILL BE PUSHED OUT OF IT. SO, IF THIS PROCESS HAS BEGUN, THERE IS NO STOPPING IT UNLESS ANOTHER CHEMICAL IS INTRODUCED THAT CAN NEUTRALIZE THE REACTION BETWEEN THE WATER AND PORTLAND CEMENT(FLY-ASH/LIME), SUCH AS VINEGAR OR SOMETHING VERY ACIDIC. THAT PROBABLY WON'T HAPPEN UNLESS A LOT OF EFFORT IS USED TO RE-MIX EVERYTHING. HOWEVER, BY THIS TIME IT MAY BE TO STIFF TO ACCOMPLISH. I PERSONALLY HAVE MIXED DIRT WITH CEMENT TO MAKE WHAT IS KNOWN AS C.T.B., OR CEMENT-TREATED BASE. AFTER TAMPING IT HARD(30 MIN. AFTER INITIAL MIX) IT BEGAN TO GET VERY FIRM UNDER THE MOISTURE RISING TO THE SURFACE. IT RISES TO THE SURFACE, SINCE IT HAS NOWHERE ELSE TO GO. THEN, IT STARTED TO RAIN, AND DID SO ENOUGH TO COVER THE CTB AREA WITH AN INCH OF WATER. TO MY SURPRISE, IT HARDENED UP JUST LIKE CONCRETE, TOTALLY SUBMERGED. WHY? BECAUSE THE RAIN WATER COULD NOT GET INTO IT-EVERYTHING WAS COMING OUT! IN MY OPINION, IT WILL CURE INA SEALED CONTAINER, ONCE HYDRATIONHAS BEGUN.
Normal concrete will cure just fine in a sealed container.
caitlinsdad is right about the bond--it is a chemical reaction involving the 'cement' in the concrete (typically a Portland Cement) and water.
The heat generated is a result of the exothermic reaction between the cement (lime in the cement) and water. It shouldn't be a problem for a small project, but when casting monolithic structures such as concrete dams, a 'low heat of hydration' concrete is typically specified. For the Hoover dam, they used chiller pipes in the concrete.
As for the mix, this is like a cake recipe; the amount of water used is important. Too much water, and you will get weak crumbly concrete. Too little water, and there won't be enough to properly hydrate the cement. Read the directions on the mix--it will all work out.
When casting concrete in a form, it is important to vibrate the mix so that any air bubble can escape, and so that the aggregate (sand & gravel) can disperse somewhat evenly throughout the mix. Easiest way might be to use a metal rod, and move it up and down thought the mix.
Sealing the container will not have adverse effect. Shorty after the concrete begins to cure, you will notice the appearance of surface water. This water will typically evaporate off of an outside slab before is can be utilized in the hydration process. Spraying slabs or sidewalk replaces this water, preventing the slab (hopefully) from shrinkage cracks due to excessive drying. Another way to achieve this is by covering the slab with wet burlap, and then a plastic sheet to retard the evaporation of surface water. Sealing your container should result in a better, harder concrete, since all of the water needed for complete hydration will be available throughout the curing process.
Long-winded, but hopefully helpful.
wow, thank you.
Curing concrete does generate heat; the greater the volume of mix, the greater the heat.
This could cause problems in a sealed container, depending on the size. The seal could fail due to internal pressure from water vaper, for instance. In large volumes, it could cause a more dramatic failure.