dcsimg

Concrete Curing. Best methods discussion.

Viewing 20 posts - 1 through 20 (of 40 total)
  • Author
    Posts
  • #732872
    Doobie
    Moderator

    Hey gang. I was using up over 40 or so bags of concrete I had that was over a year old the other day, and while Sakrete tech support said I should be OK in that their stuff is at least good for a year if kept protected, I wanted to really do what I can just in case it was nearing its useable life and do everything I can to maximize what I could do for its curing after I poured a smallish 6′ X 4′ exterior exposed pad for a NG generator I’m gonna plunk on it for my house for when we get any kind of power outage.

    I’m not a pro, just a DIYer, and it’s hard at times to find the right advice on the internet to anything reno-construction and discern what is in fact good solid advice and what is just pure crap.

    Today in fact, I was searching for advice on this subject beyond what info I read on the side of one of the Sakrete bags and on their website I used, and the advice on curing in general on the internet was really all over the map when it came to curing concrete, even on sites I can’t join like CT. But I did come accross this excellent industry association article on the subject I wanted to share.

    http://www.nrmca.org/aboutconcrete/cips/11p.pdf

    I was amazed at some of the aspects on proper curing, longevity benefits of proper curing, and just the whole gamut of info on this issue. Very informative.

    As a result, I also set up a self curing set up for my two day old pour that is almost hands free more or less for the curimg process for me.

    I set up a programmable water timer with a garden soaker hose to wet four times a day for an hour each time on top of an old bed spread I laid over my pour. This should work dandy, and while I’ll still need to make sure this sytem I set up proves adequately implemented to keep my concrete wet for maybe at least a week if not more, it was that article that really set this process in play for me having used such old stock of bagged concrete two days ago. Just glad per the article that I had been keeping the pad wet ‘manually’ til I went and did this set up today as it says once ypu let the surface dry, it’s almost a game over thing when it comes to proper concrete curing.

    Honest, even for the real pros on this site, read that article. One area of interest it mentions is ‘daming’ the pour that I thought was novel/ideal but for me, I couldn’t easily think how I could do especially once the form was off. Any of you guys ever do that sort of thing? It doesn’t go into detail how to do daming or what applications it is really conducive for, but that seemed really interesting nonetheless.

    I couldn’t find a previous discussion thread on this issue here on BTP, so I thought I’d start this new one.

    Here’s some pics of what I poured and subsequently what I set up today to keep it all nice and wet.

    #732880
    smallerstick
    Pro
    North Bay, ON

    Is there a reason you are using year old bags of concrete? Most folks I know buy it when they need it.

    BE the change you want to see.
    Even if you can’t Be The Pro… Be The Poster you’d want to read.

    #732881
    DirtyWhiteBoy
    Pro
    Honolulu,, Hi.

    Is there a reason you are using year old bags of concrete? Most folks I know buy it when they need it.

    It’s like fine wine and gets better with age.

    Dirty

    A Working Pro since 1988!

    Member since January 26, 2013.

    #732884
    GTokley
    Pro
    Madoc, ON

    Hey gang. I was using up over 40 or so bags of concrete I had that was over a year old the other day, and while Sakrete tech support said I should be OK in that their stuff is at least good for a year if kept protected, I wanted to really do what I can just in case it was nearing its useable life and do everything I can to maximize what I could do for its curing after I poured a smallish 6′ X 4′ exterior exposed pad for a NG generator I’m gonna plunk on it for my house for when we get any kind of power outage.

    I’m not a pro, just a DIYer, and it’s hard at times to find the right advice on the internet to anything reno-construction and discern what is in fact good solid advice and what is just pure crap.

    Today in fact, I was searching for advice on this subject beyond what info I read on the side of one of the Sakrete bags and on their website I used, and the advice on curing in general on the internet was really all over the map when it came to curing concrete, even on sites I can’t join like CT. But I did come accross this excellent industry association article on the subject I wanted to share.

    http://www.nrmca.org/aboutconcrete/cips/11p.pdf

    I was amazed at some of the aspects on proper curing, longevity benefits of proper curing, and just the whole gamut of info on this issue. Very informative.

    As a result, I also set up a self curing set up for my two day old pour that is almost hands free more or less for the curimg process for me.

    I set up a programmable water timer with a garden soaker hose to wet four times a day for an hour each time on top of an old bed spread I laid over my pour. This should work dandy, and while I’ll still need to make sure this sytem I set up proves adequately implemented to keep my concrete wet for maybe at least a week if not more, it was that article that really set this process in play for me having used such old stock of bagged concrete two days ago. Just glad per the article that I had been keeping the pad wet ‘manually’ til I went and did this set up today as it says once ypu let the surface dry, it’s almost a game over thing when it comes to proper concrete curing.

    Honest, even for the real pros on this site, read that article. One area of interest it mentions is ‘daming’ the pour that I thought was novel/ideal but for me, I couldn’t easily think how I could do especially once the form was off. Any of you guys ever do that sort of thing? It doesn’t go into detail how to do daming or what applications it is really conducive for, but that seemed really interesting nonetheless.

    I couldn’t find a previous discussion thread on this issue here on BTP, so I thought I’d start this new one.

    Here’s some pics of what I poured and subsequently what I set up today to keep it all nice and wet.

    I never really understood the reason for watering concrete. I worked for a company 30 years ago. We did Concrete footings, walls, pads and floors. The first year I work for them we worked right up to Christmas. We pour alot Basement walls that December. It was pretty cold that year. The concrete was still pretty green when we stripped the wall forms. I often wonder on those basement walls held up.

    Greg

    #732885
    Seven-Delta-FortyOne
    Pro
    The Emerald Triangle, Northern California

    Basically, if concrete dries too much before it sets, it can adversely affect the finished product.

    Concrete “cures”, meaning it a chemical reaction that takes place to set the concrete.

    If you allow the water to evaporate faster than the concrete is curing, you can have anything from spalling, scaling, or cracking, all the way to decreased compressive strength.

    In hot weather, during the day, this is a real concern.

    If you’re pouring in the shade, or where the daytime temp is not going to get above 80, or your have high humidity, you really have no concerns.

    Certainly not going to hurt, though.

    Forms are stripped when concrete is very green. In fact, if you wait longer than the next day, you could be in for some real trouble.

    Old bags should be fine, unless the concrete has started to harden inside. Then you’re best off just tossing it. Once it starts to set, there’s no going back. 😮

    Chance are, depending on where in Canada you are, no special curing is even necessary. Especially for a slab that small.

    Certainly won’t hurt, though.

    One guy up here built himself a concrete bunker :whistling: no idea why, :blink:, but he set up a system for spraying steam into the bunker for weeks after it was poured. Is was so solid that a sledge hammer would bounce off it like a rubber ball. 😆

    The longer it takes for concrete to cure, generally, the stronger it gets.

    Goin' Down In Flames........

    #732890
    DirtyWhiteBoy
    Pro
    Honolulu,, Hi.

    On the commercial and masonry contractors use a curing agent like Sika Antisol E-20 or there are many others that are sprayed on as soon as can to help slow down the curing.

    Dirty

    A Working Pro since 1988!

    Member since January 26, 2013.

    #732892
    GTokley
    Pro
    Madoc, ON

    On the commercial and masonry contractors use a curing agent like Sika Antisol E-20 or there are many others that are sprayed on as soon as can to help slow down the curing.

    I saw contractors spraying something on sidewalks & curbs on my street this summer. I didn’t know it was a curing agent. Thanks!

    Greg

    #732893
    Doobie
    Moderator

    Is there a reason you are using year old bags of concrete? Most folks I know buy it when they need it.

    I had four skids of it dropped in my driveway in Aug of 2018. I expected to use it all before the snow flied, but winter temps below 5C came early for us last year where I couldn’t pour the last job(s) without the overnite lows being too cold to finish what was left of jobs intended for it all.

    Then in June of this year, with just over a skid and a quarter left covered in my driveway over the winter months, I went and slogged the 70 or so of the remaining bags from my driveway into my backyard to get rid of what I knew was an eyesore for my neighbors to keep looking at in my front driveway that they’d been looking at covered all winter.

    In the two hours I spent slogging that, the next day I awoke having re-tore a my rotator cuff muscle which put me out of action for well over two months for anything involving heavy work or extended work involving my arm over shoulder or elbow high.

    Hope that explains it.

    #732899
    Doobie
    Moderator

    Old bags should be fine, unless the concrete has started to harden inside. Then you’re best off just tossing it. Once it starts to set, there’s no going back.

    I had a mixed bag of tricks with the ones I went thru two days ago. Most were stiffish upon grabbing feeling like blocks initially, but once you dropped them they were just supercially setting and crumbled readily for pouring into the mixer and mixed well in the mixer. Once ‘unfrozen’ from sitting them for so long, they just seemed fine once ripped open ready for mixing.

    Some had fist sized or bigger solid clumps even after schlopping the bag on a hard surface before dumping into the mixer or having the bag contents rotate in the mixer. I thought about just extracting them from the barrow afterwards for the half dozen large clumps that didn’t break apart in the mixer on their own, but I found I could just crumple them with shovel jabs and mix with the rest in the barrow.

    The percentage of some bags that had such clumps were less than 25% and the amount of these types of mixer unbreakable clumps I had to do manually per those bags was maybe 3-5% of a bag where it was occuring. I can’t see that as being overall compromising in doing what I did to deal with it, but then again, my concrete knowledge and experience is always evolving.

    Concrete is way more complex than one first perceives. And I love it! It’s a strenuous medium to work, challenging, but very gratifying to do one’s self as well as to myself as a DIYer hopefully properly.

    #732900
    Doobie
    Moderator

    On the commercial and masonry contractors use a curing agent like Sika Antisol E-20 or there are many others that are sprayed on as soon as can to help slow down the curing.

    I saw contractors spraying something on sidewalks & curbs on my street this summer. I didn’t know it was a curing agent. Thanks!

    Basically a sealer that exempts them somewhat from other water related curing treatments. Makes total sense they would do it this way doing sidewalks.

    #732911
    kurt@welkerhomes.com
    Pro
    Owatonna, MN - Minnesota

    basically my understanding is that a wet cure is the best, Keeping the surface continually wet for at least 7 days. this produces the least porous concrete and strongest, but is the most difficult to achieve. In most cases a film curing agent commonly known as a “Cure and Seal” is used. This keeps the top of the concrete sealed and from drying out to rapidly. It also gives some Resistance to salt. By sealing the surface and keeping it from drying to fast you reduce the porosity of the concrete which is why the salts will not affect it so much.

    many other products can be used in sealing concrete. In colder temperatures, Linseed oil can be used, which will seal the surface also.

    Another good practice is to use a good penetrating sealer applied after 30 days to five an additional seal to the concrete. This will provide even better resistance to free7zing and corrosion. If you use a Cure and Seal, you do need to make sure that and the penetrating sealer are compatible.

    #733002
    redwood
    Pro

    I do understand the curing process of concrete, but rarely do I see anyone take any of the steps outlined above, unless it is very hot.

    I’ve poured a fair amount of concrete, but rarely anything larger then 10’x10′. I’ve never done anything to slow down the drying, other then additives to the pour on hot days. As far as I know, it’s never been a issue.

    Regarding old sacks of concrete, I’ve not had much success using them. No matter how or where I stored them, they seem to get hard. If you can pick them up and drop them a foot and they break up, it’s probably fine, but I would remove any actual chunks that remain.

    Mark E.

    Pioneer, CA

    Working Pro 1972 - 2015
    Member since Jan 22, 2013
    www.creative-redwood-designs.com

    #733009
    DirtyWhiteBoy
    Pro
    Honolulu,, Hi.

    Regarding old sacks of concrete, I’ve not had much success using them.

    I think they soak up the moisture in the air and get hard without ever really getting wet.

    Dirty

    A Working Pro since 1988!

    Member since January 26, 2013.

    #733012
    Miamicuse
    Pro
    Fort Lauderdale, Florida

    A lot depends on humidity. Down here in south Florida I don’t think a bag left alone for six months would still be good for structural. Stucco and plaster mix is even more sensitive, you can mix it and it will look good while mixing but would just start falling as it sets.

    Usually spraying and misting with a visqueen cover is adequate.

    This reminds me of the concrete classes I took back in college. We had to create our own mix and make a cylinder sample. 28 days later subject to a compression test, and the stress at which it failed is directly correlated to your course grade. Such a long time ago.

    #733017
    GTokley
    Pro
    Madoc, ON

    My question is what happens to old bags of concrete at Home Center or Big Box store. When is a bag of concrete class as being to old? I never notice is there expiry date on the bags?

    Greg

    #733022
    smallerstick
    Pro
    North Bay, ON

    My question is what happens to old bags of concrete at Home Center or Big Box store. When is a bag of concrete class as being to old? I never notice is there expiry date on the bags?

    They sell them to people who don’t know any better. Reputable construction suppliers store bags of concrete mix properly and turn the inventory responsibly.

    BE the change you want to see.
    Even if you can’t Be The Pro… Be The Poster you’d want to read.

    #733023
    Sprokitz
    Pro
    Eastern shore of, Pa

    My question is what happens to old bags of concrete at Home Center or Big Box store. When is a bag of concrete class as being to old? I never notice is there expiry date on the bags?

    I’ve seen whole pallets stacked with a variety of hardened/clumped cement products at HD. It’s priced as cull. Not sure who would want or use it or what they do with it if no one is dumb enough to buy it

    #733026
    GTokley
    Pro
    Madoc, ON

    My question is what happens to old bags of concrete at Home Center or Big Box store. When is a bag of concrete class as being to old? I never notice is there expiry date on the bags?

    They sell them to people who don’t know any better. Reputable construction suppliers store bags of concrete mix properly and turn the inventory responsibly.

    That’s what I was thinking. Yes I am sure stored cool dry environment they would last for awhile.

    My question is what happens to old bags of concrete at Home Center or Big Box store. When is a bag of concrete class as being to old? I never notice is there expiry date on the bags?

    I’ve seen whole pallets stacked with a variety of hardened/clumped cement products at HD. It’s priced as cull. Not sure who would want or use it or what they do with it if no one is dumb enough to buy it

    Some people might buy them as they think they are getting a good deal. People are always looking for a deal.

    Greg

    #733031
    Doobie
    Moderator

    Regarding old sacks of concrete, I’ve not had much success using them. No matter how or where I stored them, they seem to get hard.

    What made it worse in my opinion was adding a layer over the white plastic one that the Sakrete heat wraps their skids with using poly. The sun shining thru the semi clear poly added humidity to all the bags that were at the top of the skid where I had stacked about a dozen bags on top of an unwrapped skid over the winter.

    When I wemt and hauled them all to the backyard in June, this time I used a solid non-transparent rubbery tarp to cover them. I can tell this made a huge diff with less humidity building up.

    If you can pick them up and drop them a foot and they break up, it’s probably fine, but I would remove any actual chunks that remain.

    That’s more or less what Sakrete told me. If you drop them and they don’t crumble, they’re trash. The odd fist sized chunks I had were few and far between.

    My question is what happens to old bags of concrete at Home Center or Big Box store. When is a bag of concrete class as being to old? I never notice is there expiry date on the bags?

    I don’t think the BB stores have this issue. Talking to the person at Lowes and at Sakrete, they move massive amounts of product out of BB stores. Seems to me they go thru concrete like a grocery store goes thru orange juice cartons. It was actually a question I had asked as I was concerned that what I had bought in Aug 2018 may have been sittin’ around much longer than a year. I was told it probably was in the store before you bought it a few weeks at best.

    #733048
    kurt@welkerhomes.com
    Pro
    Owatonna, MN - Minnesota

    If the clumps crush easily by smashing them or with your fist, there should not be a detriment to using them. The bond that makes the clumps with minimal hydration like that will use such a small amount of the Portland in the mix that crushing them and using them will have a minimal effect on mix strength. If the clumps are fully hydrated that they will not break up or fracture like fully cured concrete, then it is better not to use them or use them as filler in such things as a thick slab or a post hole.

    We typically use the 5000 psi mixes anyway, we find the finish better for small patches. It is worth the extra buck or two a bag to get the ease of finishing.

    For posts or post pads, we use the fast setting to get better strength sooner which in some cases will allow us to set a post on it the same day. With only the weight of a post and backfill it does not harm the concrete and saves a lot of time waiting for things to set up.

Viewing 20 posts - 1 through 20 (of 40 total)
  • You must be logged in to reply to this topic.
queries. 0.474 seconds