# How do you know when concrete was too hot to pour



## Inner10 (Mar 12, 2009)

Leo G said:


> When they do it at the plant how is it done?
> 
> Do they put liquid concrete into the truck premixed and the truck just delivers it?
> 
> ...


...Your idea is brilliant but someone already did that and it's called mobile mix...and it's awesome...


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## Tinstaafl (Jan 6, 2008)

Just talking out of my hat with no real knowledge, maybe it takes a bit more water than is feasible for a truck to carry with a full load. Ready-mix does cost more, probably because of smaller capacity among other factors.


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## Inner10 (Mar 12, 2009)

Tinstaafl said:


> Just talking out of my hat with no real knowledge, maybe it takes a bit more water than is feasible for a truck to carry with a full load. Ready-mix does cost more, probably because of smaller capacity among other factors.


Water doesn't shrink when you add it to concrete...nor does concrete...


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## griz (Nov 26, 2009)

Inner10 said:


> Water doesn't shrink when you add it to concrete...nor does concrete...


The hell it don't.....:whistling

one of the many results of too much water....:no:


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## Inner10 (Mar 12, 2009)

griz said:


> The hell it don't.....:whistling
> 
> one of the many results of too much water....:no:


If your mix is shrinking in the truck I'd say it's well past the point of usefulness...:laughing:


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## Leo G (May 12, 2005)

Tinstaafl said:


> Just talking out of my hat with no real knowledge, maybe it takes a bit more water than is feasible for a truck to carry with a full load. Ready


That's why I'm asking. Someone out there must know.

I do know that it takes very little water to make concrete to the correct load. I also know at the plant they test the moisture content of the mix before they add the water so they can get it right. Maybe for speced concrete it isn't possible to do it my way. 

The pre mixed concrete is a higher cost more convenient way to do it. But it does cost more.

My way you would still order it in the normal fashion, by the yard with a minimum. So you would get the price advantage also.


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## Inner10 (Mar 12, 2009)

Leo G said:


> That's why I'm asking. Someone out there must know.
> 
> I do know that it takes very little water to make concrete to the correct load. I also know at the plant they test the moisture content of the mix before they add the water so they can get it right. Maybe for speced concrete it isn't possible to do it my way.
> 
> ...


Mobile mix....


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## Leo G (May 12, 2005)

Stop it.

I want the cheap price.


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## Inner10 (Mar 12, 2009)

Leo G said:


> Stop it.
> 
> I want the cheap price.


Have you priced it out? I've never build any sky scrapers but the price is very competitive.


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## griz (Nov 26, 2009)

Leo G said:


> Stop it.
> 
> I want the cheap price.


You hear that a lot do you?.....:whistling:laughing: :laughing: :laughing:


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## Leo G (May 12, 2005)

Way too much.......:sad:


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## donerightwyo (Oct 10, 2011)

Leo G said:


> Just a dumb question here.
> 
> Why can't they put the dry mix in the truck and when they get to the sight add the water? That way it is fresh every time.


I wonder if the truck would be able to spin it if it were dry? Or if it would just stick to the drum.


Our trucks sometimes have a two hr drive. Very few times will we get a batch that hasn't been on the truck for an hour. On those hot days, it sure doesn't give you time to ponder.


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## Calidecks (Nov 19, 2011)

donerightwyo said:


> I wonder if the truck would be able to spin it if it were dry? Or if it would just stick to the drum.
> 
> 
> Our trucks sometimes have a two hr drive. Very few times will we get a batch that hasn't been on the truck for an hour. On those hot days, it sure doesn't give you time to ponder.


Actually I did the guy a very big favor, he was in a bind and I didn't want to cause more grief For him. 

The guy had a flat tire, you can't just jack up a fully loaded 65000 lb. cement truck and change the tire. He limped to my job, emptied his load. Then a heavy equipment company came out and took his booster wheels off the back and replaced the flat with them. He gave his word he would take full responsibility for any mishaps. Had I refused the load he would of been hard pressed to find someone with big enough equipment to Handle it. The heavy equipment guy said the biggest jack he had was 22 tons or 44000 lbs. in the end I think everything will be ok.


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## KennMacMoragh (Sep 16, 2008)

Leo G said:


> When they do it at the plant how is it done?
> 
> Do they put liquid concrete into the truck premixed and the truck just delivers it?
> 
> ...


At the concrete plant there is a giant mixing drum mounted up high that mixes the water and everything else in that mix design. The concrete trucks drive under it and the wet concrete is dispensed inside the truck, then it's delivered.


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## CJex (Oct 5, 2012)

Leo G said:


> Just a dumb question here.
> 
> Why can't they put the dry mix in the truck and when they get to the sight add the water? That way it is fresh every time.


Not a concrete guy but some possible problems.
You would have to dry all the aggregate the water content might start reacting with the cement especially after or on a rainy day the aggregate comes from outside exsposed to the weather.

They can test easily at the plant for proper water content. Add more cement if need to save a batch that would be otherwise be ruined in a truck if a touch to much water was used.

There should be someone that knows what he’s doing at the batch plant to get things right. You could pay him more because he takes care of all the trucks at the facility and train someone new. He would be able spot a problem better quality control batch get the right water content etc. 

We all know how easy it is to get good employes. Try limiting that to just the trucker pool and expect them to get cement right every time. During training you would have to pay two guys to drive around in the trucks.

Quality control arguments who botch it’s always going to be the other guys fault.


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## chew (Apr 5, 2012)

Californiadecks said:


> Today my concrete driver got a flat tire on the way to my job with 10 yards of mud it was on the road for about 1 to 2 hours before we poured it out. What's the rule on that any concrete guys out there care to help. Thanks here's some pics. The driver felt it and it wasn't warm, if it matters



You need a thermometer that has at least 3" of concrete cover in all directions left in the concrete for 2 - 5 minutes. Most specs. around here only concrete temp. up to 90 deg. If there are no specs. which is usually the case with residential concrete then like Greg 24K said & use ASTM C-94. I would be more concerned with how long it was mixing & what the driver did ,so it did not set up on him.


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## chew (Apr 5, 2012)

KennMacMoragh said:


> You would need a thermometer, when it hits 80 degrees is when it brings up some concern. But on a residential job, there's no definitive way to tell the integrity of your concrete since you have no special inspectors around. There's several other factors which will affect your concrete other than temperature; slump, w/c ratio, mix design, consolidation, time on tickets, proper placement, properly adding water, control joints, reinforcement, air entrainment, proper curing.
> 
> If you're ever concerned about a pour, you can always hire special inspectors to monitor your pour for you. I used to work as one, and we would get a residential job every now and then where they hired us to check the pour even though they weren't required to.
> 
> When the concrete gets old before it even comes out of the chute. Usually the three hour mark is where we draw the line. As an inspector, if I saw that someone was about to pour three hour old concrete I would tell them "It's your concrete, use it if you want but if you do I have to make cylinders and test this, if they don't meet the minimum compressive strength then you will be liable". I test the concrete, I do it very well, is the message I try and get across, then I leave it on them.


It depends on what you do to the concrete. The NRMCA did tests where they mixed concrete for months adding super to the mix to keep it plastic & taking samples once a day. The last samples taken broke higher than the 1st ones.


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## chew (Apr 5, 2012)

Chris Johnson said:


> With your warmer climate I would have send the load back.
> 
> 
> After 90 minutes that stuff is kicking off, pretty quick too, not sure how you got a finish on it


Judging by the footprints in the concrete it looks like a 8" slump & no longer a 0.45 w/c


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## chew (Apr 5, 2012)

Californiadecks said:


> Wasnt even warm, it finshed great, easy to work. air temp about 75. Im glad I didnt send it back. Slab came out great


You think. Most problems with concrete take time to show up.


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## chew (Apr 5, 2012)

Californiadecks said:


> I think if their was going to be problems I would no about it by now. We snapped out walls, straightened bolts, and demoed stucco on existing, and didn't see any problems. I checked with concrete company and they said 90 minutes is usually the max, however 2 hours is not going to create a problem for a bedroom addition. The mix is 4500 psi for sulfates in the soil. The engineers reasoning was the denseness of the 4500 keeps the acidic reaction of the sulfates from breaking down the concrete, whereas 2500 psi is not dense enough.


Since, you did not get a batch ticket that meets ASTM C94/C94M-09.14 & you did not preform any tests you have no idea what you got. All you have is a delivery ticket that says 4500 psi & 0.45 w/c.


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## chew (Apr 5, 2012)

Inner10 said:


> I was referring to the mobile mix trucks that mix and dispense everything on site.
> 
> Mix the concrete on site to your spec and you only pay for what you get. No concrete statues on your lawn and no shortages, perfect fresh concrete...greatest thing since sliced bread for small jobs.


The problem with those type of trucks is they mix by the volumetric method & if they are not maintained properly ,which most aren't , the concrete they produce is junk. THey are generally used around here for non-structural jobs that require less then min. truck load charge.


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## chew (Apr 5, 2012)

Californiadecks said:


> Actually I did the guy a very big favor, he was in a bind and I didn't want to cause more grief For him.
> 
> The guy had a flat tire, you can't just jack up a fully loaded 65000 lb. cement truck and change the tire. He limped to my job, emptied his load. Then a heavy equipment company came out and took his booster wheels off the back and replaced the flat with them. He gave his word he would take full responsibility for any mishaps. Had I refused the load he would of been hard pressed to find someone with big enough equipment to Handle it. The heavy equipment guy said the biggest jack he had was 22 tons or 44000 lbs. in the end I think everything will be ok.


If he going to take full responsibility tell him to send someone out with a Swiss Hammer & test the psi on the concrete. This was not his 1st flat with a loaded truck he should have a system in place to deal with them when they happen. The Redi-Mix companies we use carry an addmixture to add the concrete to save the drum if they have a problem & can't get the concrete off in time or you can use the old timers method & add sugar. A 22-ton jack would have jack the truck enough to change the tires, because you are not lifting the hole truck. Our service truck carries 20 & 50-ton jacks for flats on our dump trucks & tractor trailers. If all they did was put new tires & rims on the truck they are going to have problems later, because it look like they damage the studs.


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## Calidecks (Nov 19, 2011)

chew said:


> If he going to take full responsibility tell him to send someone out with a Swiss Hammer & test the psi on the concrete. This was not his 1st flat with a loaded truck he should have a system in place to deal with them when they happen. The Redi-Mix companies we use carry an addmixture to add the concrete to save the drum if they have a problem & can't get the concrete off in time or you can use the old timers method & add sugar. A 22-ton jack would have jack the truck enough to change the tires, because you are not lifting the hole truck. Our service truck carries 20 & 50-ton jacks for flats on our dump trucks & tractor trailers. If all they did was put new tires & rims on the truck they are going to have problems later, because it look like they damage the studs.


Actually, the weight of the truck wasn't completely on the one rim, because he still had two tires fully inflated on the same side as the flat. So I think it prevented severe damage. However, the concrete is for a master bedroom addition and nothing too structural, so it should be fine.

Like I said before in the other posts, the engineer called out for 4500 because its dense and is less susceptible to the sulfates in the soil. And the only concrete in contact with the bare soil was in the footings. The first truck load that had no issues, poured the footings complete. As for the interior slab it was on 2 inches of sand 10 mil plastic and 2 more inches of sand.


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## Elyrain (Dec 17, 2007)

If it doesn't crack/delaminate/spall/ or fall apart within the first 7 days then you'll be fine. Almost all structural issues pop up within 7 days. Any cracks after that are from shrinkage, which doesn't effect strength. Assuming the soil below is stable and rebar/WWR placement is correct of course.

The biggest concern with a hot load is not getting it consolidated. If it's still fluid enough to come out the shoot and responds to a vibrator, it's probably ok. Unless they add a sh!t ton of water then it'll delaminate and basically fall apart slowly because the compressive strength got compromised. By the looks of the footprints in your pics, it looks like it was still a good.


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## KennMacMoragh (Sep 16, 2008)

chew said:


> The problem with those type of trucks is they mix by the volumetric method & if they are not maintained properly ,which most aren't , the concrete they produce is junk. THey are generally used around here for non-structural jobs that require less then min. truck load charge.


Not arguing but how do you know this? True I'd be a little suspicious as to how well they do their quality control from the back of a truck as opposed to the batch plant. But what have you seen or tested to tell you the concrete is junk?


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## Calidecks (Nov 19, 2011)

Elyrain said:


> If it doesn't crack/delaminate/spall/ or fall apart within the first 7 days then you'll be fine. Almost all structural issues pop up within 7 days. Any cracks after that are from shrinkage, which doesn't effect strength. Assuming the soil below is stable and rebar/WWR placement is correct of course.
> 
> The biggest concern with a hot load is not getting it consolidated. If it's still fluid enough to come out the shoot and responds to a vibrator, it's probably ok. Unless they add a sh!t ton of water then it'll delaminate and basically fall apart slowly because the compressive strength got compromised. By the looks of the footprints in your pics, it looks like it was still a good.


It was poured Monday and alls well so far, I think we got through it ok.


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## KennMacMoragh (Sep 16, 2008)

Californiadecks said:


> It was poured Monday and alls well so far, I think we got through it ok.


Probably, but I've seen concrete fail months or years after a pour. All due to bad concrete from the beginning.


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## Calidecks (Nov 19, 2011)

KennMacMoragh said:


> Probably, but I've seen concrete fail months or years after a pour. All due to bad concrete from the beginning.


I don't think two hours was long enough for that to be a problem


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## KennMacMoragh (Sep 16, 2008)

Californiadecks said:


> I don't think two hours was long enough for that to be a problem


You're right. Personally, if it was any longer than that, if it was 2 hours 15 minutes, I would send it back. I would say send me a new load, not buying old concrete.


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## Inner10 (Mar 12, 2009)

chew said:


> The problem with those type of trucks is they mix by the volumetric method & if they are not maintained properly ,which most aren't , the concrete they produce is junk. THey are generally used around here for non-structural jobs that require less then min. truck load charge.


You can test the concrete just like when you order a transit mixer.:whistling


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## KennMacMoragh (Sep 16, 2008)

Inner10 said:


> You can test the concrete just like when you order a transit mixer.:whistling


Yeah I know, I was wondering if anyone has ever done this. Being that it seems they are used strictly of residential work where special inspection is rarely required.


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## Needles (May 18, 2012)

I was on a job once were a concrete truck that was lost didn't show up till two hours after it was batched. This was a like a twenty truck'r pump. Anyway those idiots spent all night around the clock chipping that wall out. But that was for some Redmond giant that was going to be paying for a hacked building. 

You have a slab on grade I assume and not a suspended deck. You should be fine.


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## chew (Apr 5, 2012)

Californiadecks said:


> Actually, the weight of the truck wasn't completely on the one rim, because he still had two tires fully inflated on the same side as the flat. So I think it prevented severe damage. However, the concrete is for a master bedroom addition and nothing too structural, so it should be fine.
> 
> Like I said before in the other posts, the engineer called out for 4500 because its dense and is less susceptible to the sulfates in the soil. And the only concrete in contact with the bare soil was in the footings. The first truck load that had no issues, poured the footings complete. As for the interior slab it was on 2 inches of sand 10 mil plastic and 2 more inches of sand.


If the engineer was concerned about sulfates he should have specified type I-II or type II cement also. You did not mention what cement was specified.


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## chew (Apr 5, 2012)

KennMacMoragh said:


> Not arguing but how do you know this? True I'd be a little suspicious as to how well they do their quality control from the back of a truck as opposed to the batch plant. But what have you seen or tested to tell you the concrete is junk?


We test everything we pour. From the times we have used volumetric trucks they are not giving you what you ordered. The biggest problem is their unit weight is usually off. Which means their mix proporations are wrong. If the mixer is maintained they mix well, but most aren't, because nobody is testing their concrete.


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## chew (Apr 5, 2012)

Elyrain said:


> If it doesn't crack/delaminate/spall/ or fall apart within the first 7 days then you'll be fine. Almost all structural issues pop up within 7 days. Any cracks after that are from shrinkage, which doesn't effect strength. Assuming the soil below is stable and rebar/WWR placement is correct of course.
> 
> The biggest concern with a hot load is not getting it consolidated. If it's still fluid enough to come out the shoot and responds to a vibrator, it's probably ok. Unless they add a sh!t ton of water then it'll delaminate and basically fall apart slowly because the compressive strength got compromised. By the looks of the footprints in your pics, it looks like it was still a good.


Actually, most structural failures show up when the designed load is applied.


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## chew (Apr 5, 2012)

Californiadecks said:


> It was poured Monday and alls well so far, I think we got through it ok.


You think it okay, but you are making an uneducated guess. You have not preformed any test on the concrete to determine what was supplied to you.


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## chew (Apr 5, 2012)

Inner10 said:


> You can test the concrete just like when you order a transit mixer.:whistling


I never said you couldn't  , but when you do that is when you find out what they sent you.


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## Diamond D. (Nov 12, 2009)

Inner10 said:


> I was referring to the mobile mix trucks that mix and dispense everything on site.
> 
> Mix the concrete on site to your spec and* you only pay for what you get. * No concrete statues on your lawn and no shortages, perfect fresh concrete...greatest thing since sliced bread for small jobs.





chew said:


> The problem with those type of trucks is they mix by the volumetric method & if they are not maintained properly ,which most aren't , the concrete they produce is junk. THey are generally used around here for non-structural jobs* that require less then min. truck load charge.*


Don't be fooled, these mobile mixers also have minimums.
Sure, you only pay for what you use, but the first 1/2 yard might cost ya tree-fiddy. (that includes, at least, the first wheelbarrow of dirty stone that you have to loose somewhere.)
Generally, ready-mix is usually cheaper in the long run.

Although, I do use both methods, depending on the situation, the ready-mix, in my opinion, is a much better product and easier to work with, especially when it comes time to finish.

D.


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## jomama (Oct 25, 2008)

Leo G said:


> When they do it at the plant how is it done?
> 
> Do they put liquid concrete into the truck premixed and the truck just delivers it?
> 
> ...


They actually use both methods, depending on the plant construction, and some plants have both. 

The first one is called a "wet-mix" plant and typically uses a huge paddle mixer somewhat similar to a mortar mixer. Generally, a little slower doe to redundancy, and the mixers are often only 6-7 yards or less, so they require two mixes to fill a truck completely. 

The second is certainly more common here, and can be loaded much faster. In this set-up, the plants conveyors bring all the material into the top bin before the truck is usually even pulled in. Here, it's weighed for the proper proportions, and slowly dropped into the top of the truck simultaniously with the "correct" amount of water and any admixtures.

With probably 95% of loads here, time is no issue, and when it is, a small dosage of retarder can easily add 30 mins, and much more if needed, with no ultimate effect on the finished concrete.


To the OP you may have bought a 4500 psi mix with a .45 w/c ratio, but after they dumped additional water into the load, you likely didn't get anything close to that at the end. But like you said, it's still likely adequate for what it's doing.


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## CJex (Oct 5, 2012)

A story that may be of interest reading these posts reminds me of what happened to a relative. They put in cement sidewalks around their house poured by two different trucks. Same people prepping site poured same day same people working / finishing cement only thing different was concrete two different batches.

You could not tell there was anything different where one truck stopped and the other started the rest of the summer. Come winter they buy cement sidewalk safe safety salt don’t know what chemicals are involved in that. Where the fist truck poured and precast cement steps where untouched. Well the second truck like you drew a line completely ate away and striped the surface off to just looks like ruff exposed aggregate no finish.

Every other respect as far as you can tell its fine. First part and precast steps fine something was screwed up with the second load what I don’t know I was not there.


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