All concrete will crack.

[twinrider1]

A fact of life or a BS excuse for poor site preparation?

 

[Newell Steamer]

75% poor site prep - 25% fact of life (shit happens).

 

[JulesMaximus]

75% poor site prep - 25% fact of life (shit happens).

Numbers pulled straight out of ass. :sneaky:

 

[vi edit]

Lot of factors can go into it. If you get shit weather during the pour and it cures out too fast it'll crack. A lot of freeze/thaw cycles. It will will crack. Frost heave. Cracks. Preparation, sealing and control joints will minimize, but sometimes it just does it's own thing.

 

[Newell Steamer]

Numbers pulled straight out of ass. :sneaky:

Ass connected to feet that walk through the concrete jungle. Just my observation.

When landlords try to play construction worker - they just drop a pile of ready mix concrete onto a gap or hole on the sidewalk,.. and, it shatters with in a week.

Properly prepared sites stay smooth and crackless for quite sometime.

Any concrete that was poured by someone other than Juan the super, that did crack was due to the recently extreme weather conditions - our really cold and snowy winter - where even bricks were shattering.

 

[BoomerD]

A fact of life or a BS excuse for poor site preparation?

Fact of life. You can do the best possible sub-grade prep, put in rebar and add fiber to the mix...concrete will still crack. It's just the nature of the beast.

 

[mikeford]

Concrete has huge strength under compression, not too much under tension, equal poor site preparation.

 

[vi edit]

Any concrete that was poured by someone other than Juan the super, that did crack was due to the recently extreme weather conditions - our really cold and snowy winter - where even bricks were shattering.

Yeah this past winter really f'd my old drive up. It was poured in September and then the winter hit. And it just didn't hit. It freaking slammed down like the fist of an angry god. We had about a week of temps that were pushing -20. That virgin concrete didn't stand a chance.

 

[KB]

Fact of Life. Thats why they are working on this:

http://www.technologyreview.com/new...concrete-uses-sunlight-to-fix-its-own-cracks/

 

[cronos]

Fact of life.

 

[MrDudeMan]

There's way more that goes into it than just site prep. It's partially a fact of life because most concrete will crack to some degree, but it also really depends on what you mean by crack. If you mean a structural crack, then no, not all concrete will crack. If you mean temperature shrinkage cracks, then mostly yes as all but the very highest pressure concrete will crack to some degree. It also depends how the concrete is being used and what forces are acting on it.

 

[Blackjack200]

I'd like everyone to know that I just 86'd my "All plumbers show crack" parody thread because I'm far to mature for that nonsense.

 

[bradley]

I've also voting for not enough site preparation and improper execution increases the odds that concrete will crack, no rebar, mesh, fiber, expansion joints, improper mixture etc.

Additionally slowing down the curing time (by keeping it moist) will decrease the odds that concrete will crack. Moist cure concrete (at a lower curing temperature) actually doubles its compression strength after one week.

 

[ElFenix]

are we talking about the HS stadium in the dallas area?

 

[smackababy]

While, I believe eventually all concrete will crack, it isn't going to be for a good while. Relatively new concrete should not crack unless there are extenuating circumstances that caused it.

 

[Scarpozzi]

Your best bet is to pour it thick and try to slow the cure down when it's poured too. I had additives put in mine (no fibers), but reinforced the slab with steel. It was a garage floor and I didn't drive on it for a week.

The guys I had doing the job were true pros....The additives and time or year (Fall) made a difference, but I still have a few cracks. They're close to the joints they scored, so I have no complaints.


Try to avoid using salt on concrete in winter...it can do some serious damage to the surface.

 

[isekii]

If you seal it do you have to worry about water?

 

[Fritzo]

Poor prep. Concrete will last hundreds years if done right. Shifting ground aside, Roman concrete has lasted 2000 years.

 

[NoTine42]

If you seal it do you have to worry about water?

How do you seal the bottom of a slab of concrete?

 

[bradley]

If you seal it do you have to worry about water?

Water exposure is actually the friend of newly laid concrete, unlike salt. Sealing the concrete with acrylic (not allowing moisture to escape) would increase the curing time and therefore the strength of the concrete. For larger industrial jobs, contractors will continue to hydrate the concrete for 3-7 days while its covered with plastic or other materials.

Curing strength is also related to how long concrete goes without being used or stressed.

 

[Humpy]

As others have noted "crack" has to be defined.

New concrete will often show cracks because the evaporation of water leaves small spaces in the concrete that show up as cracks. This type of cracking can be almost 100% eliminated by using water reducing admixtues and various curing techniques.

I have several exposed concrete floors in my house that show zero signs of any cracking after 12 years. They were poured in the shade and on a cool day with a low water mix.

Cracking due to slab movement (frost heave, settling, etc.) after curing can be almost 100% eliminated through proper engineering, soil preparation, and reinforcing techniques.

Concrete by its nature will, to my knowledge, always have micro-cracking and other flaws that are inherent in its structure. I would not define this as cracking as it is not visible and not considered a flaw.

The statement that all concrete will crack is a complete bullshit statement that bad contractors use out of context to hide the fact that they lack the ability or motivation to do the job correctly. There are industry standards for allowable cracking that should be included in the contract and if they are not met then the work should be rejected.

Edit: I should also add that many customers can't or won't spend the money for a proper job. They get what they pay for and have to live with results.

 

[Imp]

Screw cracking...

Delamination, now THAT is some fancy shit. You can have the top layer of an entire wall come down in front of you. It makes the prettiest sound when hit with a hammer.

 

[Red Squirrel]

Concrete shrinks as it cures so there can be cracks from that, but big cracks from entire slab shifting in some spots = bad site prep.

Really to do things right you need a footing at least 8 feet deep if more. It's hard to do just a slab and have it not crack. That's why you see sidewalks and pavement cracks all the time, those are just slabs put on the surface. They do their best but it's always going to move a bit from the frost.

When they built my house they added a concrete deck on the back, that slab was part of the actual garage slab and poured in one continuous poor. The outside portion sat on two big square pillars that go like 10+ feet in the ground, there's probably a footing in there too, would not be surprised. The two pillars met up at a beam which the slab sat on. There was actual plates of steel + rebar in that thing.

They seriously engineered that to last. Unfortunately it had to all come out when they did the weeping tiles. Took a day with heavy machinery to get that deck out. The pillars are still in the ground. I told the guy if they don't move after he digs around it to get to the weepers to just leave it in, and it did not move. It was deeper than the weepers were. The other pillar was not in that area so it stayed in too. I can build my new deck over them when I get to that, and know it will be solid as hell.

You don't see that kind of construction anymore.

 

[disappoint]

Yeah this past winter really f'd my old drive up. It was poured in September and then the winter hit. And it just didn't hit. It freaking slammed down like the fist of an angry god. We had about a week of temps that were pushing -20. That virgin concrete didn't stand a chance.

Damn man that sucks. What about paving stones? Good alternative to concrete or come with their own set of problems?

 

[Printer Bandit]

Watch the movie Locke.

He knows the importance of a concrete pour.