things I need to know about concrete?

[Ryf]

I am having a slab poured for my 20x22 shop next week. going with rebar grid and fiber mesh. I have searched and what I can tell, I need to keep the top moist/damp after the initial pour, but how long do you wait to start wetting it? it looks like it might be 95 degrees the day of the pour as of now. I am not doing the work, but I know from reading I have to do some "early maintenance" to keep it from cracking alot during the drying process.

any other tips are welcome, thanks in advance.


added--
it appears this ended up where I didn't intend, feel free to move to general discussion if needed.

 

[shurik06_83]

once its stiff and can be walked on is the time to soak it but make sure its not too green if its still not set the water will wash the milk away from the top and u might loose some smooth finish

best thing is to get a big roll of filter cloth at HD or lowes cover the slab with the filter cloth and soak the cloth

filter cloth is the stuff u put down before u pour screening material for inter lock so any landscape place will have it u want the thickest they have as the thicker cloth will hold more watter

when i did parking garage decks we would pour and as soone as wee can walk on it without marking it up wee would cover it with the cloth and flood it come back the next day flood it and do other things flood it at lunch and once more before we went home

some decks we soaked for 2 days some for a week

even if u soak it for a week in a few yrs u will get small surface cracks from shrinkage so line it out and relief cut it u don't need to go too deep 1" is more then enough

 

[Ryf]

once its stiff and can be walked on is the time to soak it but make sure its not too green if its still not set the water will wash the milk away from the top and u might loose some smooth finish

best thing is to get a big roll of filter cloth at HD or lowes cover the slab with the filter cloth and soak the cloth

filter cloth is the stuff u put down before u pour screening material for inter lock so any landscape place will have it u want the thickest they have as the thicker cloth will hold more watter

when i did parking garage decks we would pour and as soone as wee can walk on it without marking it up wee would cover it with the cloth and flood it come back the next day flood it and do other things flood it at lunch and once more before we went home

some decks we soaked for 2 days some for a week

even if u soak it for a week in a few yrs u will get small surface cracks from shrinkage so line it out and relief cut it u don't need to go too deep 1" is more then enough

good info, cant flood it per say, can definitely hose it down 3-4 times a day. the yard sheeting is a good idea, what about hosing it down and then covering it with plastic (have plastic, so free is why I ask)

thanks again. not worried about the cracks just want to avoid the real bad stuff. it will definitely be cut. mostly just looking to.. ummm.... give it the best chances to look as good as possible lol.

 

[Wastedwagesracing]

Just remember anything you put on it while it's curing is going to leave a stain or mark.

 

[pcmeiners]

not moist/damp ...WET

plastic is OK, maintain water, do not let it dry out for even a short time, for a min of 8 days, the longer you keep it wet up to 28 days the better, most of the cure happens within 8 days. If you have plastic just under the crete, keeping the surface wet is more imperitive.

 

[Ryf]

ok.... wet... so like get a garden sprinkler hose (the green one with the holes in it) and leave it on? 24/7???? I can't see that being a good water bill!

 

[pcmeiners]

"the green one with the holes in it" sounds good, but you only need the slightest amount of continuous water from the hose, not full on. What could that cost?, 2 bills a day, $16.00 vs surface cracks/weaker strength in your crete.

 

[Mr Ratchet]

I wait until the cement is hard enough so that you can touch it without leaving marks. Then I flood the slab and continue as it drys until later in the night. The next day, I snap my lines and make my control joint cuts, followed by more floodings for the next couple of days.

A good base is a must for cement not to crack. If you are pouring over sand, a layer of gravel is always a good start. There are also differnt PSI ratings and hardners that can be applied to help reduce cracks. The depth of the pour will make a difference. Usually the fiber replaces the rebar, but the extra percaution never hurts.

I also like to pin my cement whenever I can and lay rebar in the middle where I will be cutting control joints.

 

[Ryf]

"the green one with the holes in it" sounds good, but you only need the slightest amount of continuous water from the hose, not full on. What could that cost?, 2 bills a day, $16.00 vs surface cracks/weaker strength in your crete.

then might be better to use one of those weeper hoses? if it doesnt take much that puts out a gallon per foot per hour, alot less than "the green one with holes" lol

I wait until the cement is hard enough so that you can touch it without leaving marks. Then I flood the slab and continue as it drys until later in the night. The next day, I snap my lines and make my control joint cuts, followed by more floodings for the next couple of days.

A good base is a must for cement not to crack. If you are pouring over sand, a layer of gravel is always a good start. There are also differnt PSI ratings and hardners that can be applied to help reduce cracks. The depth of the pour will make a difference. Usually the fiber replaces the rebar, but the extra percaution never hurts.

I also like to pin my cement whenever I can and lay rebar in the middle where I will be cutting control joints.

dug out with sand and gravel, 4000 psi concrete with fiber and rebar. I heard you go with out mesh with fiber, didn't know you could drop the rebar too.

 

[bcradio]

Plastic is an excellent way to cure concrete as its not breathable like fabric and lets virtually no water out.

Also, do not use rebar unless it will be at least 6 inches thick. Use wire mesh if it will be less.

 

[shurik06_83]

the reason i used filter cloth is it holds lots of water in it so u soak the cloth and i forgot to mention u can cover the cloth with plastic

cloth will hold water so all u have to do is step out for 5 min soak the cloth and go back to doing whatever once the cloth is just damp not soaken wet soak it again

summer is a pita when it comes to this the water will dry up like crazy even with poly covering it the tarp will start lifting up and steam will shoot out the sides