Curing

[PlanoPhil]

Wow my head is hurting from reading all the opinions on curing. Keep it wet? What's that all about? I thought the whole idea was to get the moisture out. Confusing.
Anyway I'm about to install my Casa 90 and need to know:

1. Can I cure before applying the insulation blanket?
2. Should I cover it if it rains?
3. How will I know it is cured sufficiently?

Thanks

[brickie in oz]

Originally Posted by PlanoPhil

Wow my head is hurting from reading all the opinions on curing. Keep it wet? What's that all about? I thought the whole idea was to get the moisture out. Confusing.
Anyway I'm about to install my Casa 90 and need to know:

Keeping it wet is a urban myth about letting the mortar dry slowly so it hardens properly without cracking.
Ive laid bricks on 40c days and honestly havent seen any cracking or weak joints.

They pour large concrete slabs for houses in the heat here and they dont even crack, well, not more that you would expect.

Originally Posted by PlanoPhil

1. Can I cure before applying the insulation blanket?
2. Should I cover it if it rains?
3. How will I know it is cured sufficiently?

1.
Yes and it would dry quicker doing it that way.

2.
Yes, otherwise you are right back to where you started from.

3.
Youll know, because the fires will actually start to get hot and burn with a passion.

[david s]

There is confusion about the term "curing".
Firstly, when applied to freshly laid concrete containing Portland cement: it should be kept moist for a week. Concrete not treated this way will not achieve its max strength. This applies to anything made containing Portland cement. It is impractical in many instances to keep a slab moist for a week, so it is often not done, however the resulting strength may be down as much as 60%. Castable refractory containing calcium aluminate cement does not need this treatment. It should be covered for 24 Hrs only.
The other type of "curing" referred to with oven construction is the elimination of water. This is a problem because steam pressure build up can cause cracking and moist insulation doesn't work too well. We should really invent another name for this process to avoid the resulting confusion.

[brickie in oz]

Originally Posted by david s

There is confusion about the term "curing".
Firstly, when applied to freshly laid concrete containing Portland cement: it should be kept moist for a week. Concrete not treated this way will not achieve its max strength. This applies to anything made containing Portland cement. It is impractical in many instances to keep a slab moist for a week, so it is often not done, however the resulting strength may be down as much as 60%.

Please tell me the AS standards this is referring to so I can reference it.

I havent seen this anywhere in the brickwork AS or the concrete AS and I have both at hand.

Did I miss something in the AS's ?

[david s]

you need to read the info from Cement Aust. I was actually wrong about strength being down to 60% concrete air dried is actually only 40% of full compressive strength.

http://www.concrete.net.au/publicati...f/Curing06.pdf

[david s]

Boats made from ferro cement are carefully cured for 28 days for the same reason. I'd hate to be in the ocean in a crumbly concrete boat. aaahh!

[brickie in oz]

Sorry David but I have to laugh, theory is one thing but practice is entirely a different beast.

Never in 30 odd years in the trade have I seen any concreter covering their slab with plastic to cure it, Ive seen slabs laid one day and the timber frame erected the next.

Im sure the same concrete slab is still there doing what its supposed to do 20 years on.

[brickie in oz]

Originally Posted by david s

I'd hate to be in the ocean in a crumbly concrete boat. aaahh!

Wouldn't it be Yarhhhhhhhh?

[david s]

[QUOTE=david s;111244]There is confusion about the term "curing".
Firstly, when applied to freshly laid concrete containing Portland cement: it should be kept moist for a week. Concrete not treated this way will not achieve its max strength. This applies to anything made containing Portland cement. It is impractical in many instances to keep a slab moist for a week, so it is often not done, however the resulting strength may be down as much as 60%.
As I said, it is impractical in many instances to keep it moist. However all prestressed concrete beams, pipes etc. are manufactured in this way to gain max strength from the cement used. If possible why wouldn't you make it as strong as you can. The other alternative is to over build it and hope for the best.

[brickie in oz]

The problem with having the mortar too hard is if there is ever any movement the bricks crack instead of the joint.