Removing Forms

[Grunt44]

Anybody tell me how long you should keep the forms on after a hearth slab has been poured.
Mine is Approx 1500mm x 1500mm , corner built , 75mm thick with a counter /shelf at the front . Plenty of 1/2 '' Rebar went into it . The Shelf at the front is canterlevered.

[meco211]

i took my forms off the sides after 24 hours, but plan on leaving the ones underneath for atleast a week if not a bit longer just to make sure!!!

[Glosta]

Toby-concrete needs moisture to cure to full strenght. The underlying bonding is a chemical hydration reaction(hydro/water) It is important to keep it moist for at least a week. That is when most of the reaction takes place. But thirty days is even better. Leaving forms on traps in the moisture. That is good for strenght. But if you leave the forms on for a week, its a bear to pry them free. So masons usually pry forms off after a few days but keep the project moist by spashing some extra water on it each day and covering with plastic. I usually see this done on concrete slabs and walls-(But not on block or brick work--wonder why?) Your can remove the plastic while working and cover each day when you are through. Added bonus it protects your work from the night time rain showers. Good Luck Gloast

[meco211]

I have been giving mine a light coating of water a couple times a day! want it to get as strong as possible--with all the weight that sits on top of them

[Tscarborough]

The forms also get harder to remove the longer they are left on. In normal concrete construction it is rare for vertical form work to be left on for more than a day, for horizontal form work more than a week. Concrete does not cure in a linear fashion. It hits better than 50% in 2 days and 80% in a week, with (nearly) 100% being reached in 28 days under ideal conditions.