Concrete psi

[Pataskala Neander]

Had two garage apron concrete pours performed yesterday. We were not home so couldn't check the ticket the driver usually has for correct psi. Our estimate and the contract we signed from the contractor stated 4500 psi. We have, however caught this contractor in several lies to us, so we called the concrete company to find out if what we received was actually 4500 psi. The person who answered stated they do not give this info out to the homeowner, only the contractor. Is there a way to test for psi? The contractor removed the forms only 4-5 hours after the pour.

 

[The Cobbler]

sounds like they don't want to get in the middle of disagreements but I think they would be legally obligated to tell you if their batch met your contract terms with the contractor .
as far as removing forms, nothing wrong with that if it's set hard enough and they were careful

 

[mike93lx]

You could have a core drilled and tested, but all that for an apron?

 

[Pataskala Neander]

sounds like they don't want to get in the middle of disagreements but I think they would be legally obligated to tell you if their batch met your contract terms with the contractor .
as far as removing forms, nothing wrong with that if it's set hard enough and they were careful

Thank you! I will try and call them again with this info. Now however, we are dealing with the contractor not showing up to cut the control joints and it's been over 24 hours since the pour. He claims he will send someone out tomorrow, which from all I have read is too late for these cuts to be effective, and the cuts may not cause cracking. I am so very sick of this.

 

[Pataskala Neander]

You could have a core drilled and tested, but all that for an apron?

We don't want to go this far. We do however have a pile of the cement next to our apron pour that they left behind.

 

[dcg9381]

sounds like they don't want to get in the middle of disagreements but I think they would be legally obligated to tell you if their batch met your contract terms with the contractor .

The consumer was not their customer. Concrete was sold to a 3rd party contractor. You don't have to tell the non-customer squat.
Protects the margins of all the people that are marking up concrete! Ask any 3 concrete contractors here what concrete costs them, you'll get wildly different answers.


If you distrust your contractor this much, I'd stay home.
Lets say it's 3000 psi, OP, what are you going to do? All you can do is hold back final payment to the contractor. If you haven't paid the contractor yet, ask the contractor to release information from the supplier before you cut that check.

 

[ConCretin]

There are several options for testing concrete in situ. There are mostly non destructive tests such as a Windsor probe and Swiss hammer that can provide an indication of compressive strength or you can have cores taken and tested for a more accurate result. In all cases, you'll need to wait 28 days for the concrete to reach design strength. There should be a testing lab in your area you can call.

With that said, have you paid the contractor yet? If not, you have some leverage to get your contractor to provide documentation from the supplier. If not, you probably don't have many good options. You could pay for the tests and sue if the concrete doesn't comply with the contract but that may not be all that productive either.

For what it's worth, your concrete doesn't need to be 4500 psi to do it's job. While it's true that higher strength mixes provide a more durable surface due to having additional cement, the loads on your aprons will never be high enough to result in structural failure.

With regard r stripping forms, it's fine to do so as early as you can without causing damage to the concrete. Control joints should be cut as soon as possible, preferably with an early entry saw immediately after placement. The longer you wait. the more likely you are to get random surface cracks.

 

[Rusted Nut]

Demand the contractor give you mix tickets before payment. Hold back $$$’s for crack repair considering cuts weren’t made sooner.

 

[The Cobbler]

The consumer was not their customer. Concrete was sold to a 3rd party contractor. You don't have to tell the non-customer squat.
Protects the margins of all the people that are marking up concrete! Ask any 3 concrete contractors here what concrete costs them, you'll get wildly different answers.


If you distrust your contractor this much, I'd stay home.
Lets say it's 3000 psi, OP, what are you going to do? All you can do is hold back final payment to the contractor. If you haven't paid the contractor yet, ask the contractor to release information from the supplier before you cut that check.

nothing to do with cost . everything to do with what slump & psi was ordered. bet your **** a large job would demand to see tickets..

 

[Pataskala Neander]

What is the process for crack repair? Do they show up during the postponed cuts or down the road?

 

[The Cobbler]

the cuts are to create a weak spot so hopefully the concrete cracks there , but there's no guarantees.
the expansion & contraction with temperature swings is why they're primarily there , to crack along the given line & not randomly throughout the pad.
about the only guarantee with concrete regarding cracks, is, it will crack .

 

[Old tool guy]

Swiss hammer that can provide an indication of compressive strength

For what it's worth, your concrete doesn't need to be 4500 psi to do it's job.

Swiss hammer test is worthless. A good tech can make the test show whatever results they want.

Correct, 3000 psi will perform just fine, but the contract called for 4500 and they paid for that.

 

[ConCretin]

Swiss hammer test is worthless. A good tech can make the test show whatever results they want.

Now why would a "good" tech from an independent testing lab report falsified results?

A Swiss Hammer otherwise known as a rebound hammer has it's limitations but it's far from useless and they have been used countless times on commercial/industrial concrete projects. They are most useful when comparing two concrete samples especially when one's compressive strength is known. You can also use a chart provided by the manufacturer to estimate compressive strength. It would be a quick, inexpensive indication of whether you have 3000 or 4500 psi concrete.

There is no doubt the OP is entitled to 4500 psi concrete, properly installed control joints and many other aspects to a proper concrete job but unfortunately the status of payment is the biggest consideration when trying to achieve them after the fact.

 

[ConCretin]

What is the process for crack repair? Do they show up during the postponed cuts or down the road?

There is no hard and fast requirement that shrinkage cracks be 'repaired'. After all it's basically the same crack whether you can see it or it's hidden in the bottom of a control joint.

It gets a little more complicated if you intend to seal the cracks. With a pre-cut control joint, you can easily just fill the cut with sealant. To seal a random surface crack, you'll have to use something like a crack chaser bit on an angle grinder to open up the crack enough to get caulking in. The results won't be very attractive.

You could also use a low viscosity polyuria to glue the crack together. You will still need to chase the crack and it will require some artistry to hide the repair but you might bet better results.

 

[dcg9381]

nothing to do with cost . everything to do with what slump & psi was ordered. bet your **** a large job would demand to see tickets..

I'm aware it's not a cost issue, I'm just saying that "protecting margin" on their direct customer is common in the construction industry. Most vendors aren't going to give up the actual invoice to the contractor. Pretty normal here across all of the construction space.

 

[BombShelter]

When I was a young salesguy selling flatwork and a ton of aprons, we used 4500 psi concrete and not a single person ever asked for verification in my four years. We also never cut control joints in aprons which averaged 4' x width of the garage. I can still drive around today and I've never seen our 18 year old work go bad and we live in very harsh climate conditions.

Clean up is a different story, you can do a five-star job but if a guy drops a couple butts, you'll hear about it.

 

[Old tool guy]

. Most vendors aren't going to give up the actual invoice to the contractor.

There‘s a miscommunication going on here. The OP is not asking for a copy of the invoice, he wants the delivery ticket which should show the batch information.

 

[lakeroadster]

There‘s a miscommunication going on here. The OP is not asking for a copy of the invoice, he wants the delivery ticket which should show the batch information.

And even if the batch was correct... it can be watered down, on site, before the pour, which will affect the strength. I was there on site when they poured the floor, reviewed the batch ticket and the water, uploaded that data into my computer and gave them the go ahead to pour. One truck load they wanted to add more water, I told them no.​

​

OP: Your only option is to have it tested after 28 days (like right now). You'll either be pissed off... or elated. Or just forget the entire thing and chalk one up to experience and be there next time.​

 

[AC-WC]

Why would you continue to use a lying contractor?
Mistakes are one thing but if you caught them in lies my business ends there.

 

[bb29510]

it really doesnt matter, it started life as a 4500 but by the time they stop adding water, its really a 1800

 

[BillK]

I don't know how you guys do it but there is no way that job would have been done without either my Wife or myself being there.

 

[tarmy]

They had to have either paid the bill or will for the concrete. Demand a copy of the ticket with yardage and specs of mix. No ticket equals no money. Zero chance I would pay a nickel without the job complete and that original ticket in hand. You also need to make sure he actually PAYS the sub bill….otherwise they may have preleaned or will lean you. If you pay without the release then you contractor can take off and you are screwed.

tell him you need proof of payment or the ticket so you can make a check out to the sub for the amount owed. Knock that amount off what you owe him and give him two checks….then follow up to ensure the sub was paid.

 

[jonesg]

pay a lawyer $75 to send a letter, you'll get what you want.

 

[Chaznsc]

Call a geotechnical engineer to take cores and test them at seven and thirty days.

 

[pcmeiners]

"Why would you continue to use a lying contractor?"

Because it is difficult to find one which does not lie.

 

[Sumboodie]

We don't want to go this far. We do however have a pile of the cement next to our apron pour that they left behind.

They mixed the concrete on site?

 

[Cairo94507]

Jesus, I 100% agree with BillK; I would never have a pour done without me being there to check the load ticket for the correct PSI and to make sure they did not add water to the mix.

We just broke ground 3 weeks ago on a house with a 2K sq. ft. garage that will be a 4300 PSI 6" concrete floor. We will definitely be there to make sure it is done correctly; fortunately we have a superstar contractor with 30 years experience and he has been a joy to work with.

 

[BigGarage]

We don't want to go this far. We do however have a pile of the cement next to our apron pour that they left behind.

I worked in a cement testing lab for a few years. One of the test methods for strength was to use a mold like this. There is a standard process in the lab for mixing up a batch for testing. It's mixed in a large Hobart mixer and then placed in molds like this. We always used 3 molds per batch providing 9 2"x2" cubes. They would be placed in a humidity controlled room and they would be submerged underwater.

I think we tested them in the compression machine at 1, 3, 7, 28 and 56 days. The machine presses down until the cube cracks and the PSI is recorded.

I would guess that a local company that has a concrete testing lab might do this for you. The finished product had to meet ASTM standards since it was used in roads and bridges. Even then you cannot prove the pile of cement they left behind was the same as what they used in the pour.

Good luck.

 

[NDJ]

pay a lawyer $7500 to send a letter, you'll get what you want.

 

[Old tool guy]

. We always used 3 molds per batch providing 9 2"x2" cubes.

If you were making & testing 2x2 cubes ... was that brick mortar or concrete for a slab?

 

[WNYflyer]

I worked in a cement testing lab for a few years. One of the test methods for strength was to use a mold like this. There is a standard process in the lab for mixing up a batch for testing. It's mixed in a large Hobart mixer and then placed in molds like this. We always used 3 molds per batch providing 9 2"x2" cubes. They would be placed in a humidity controlled room and they would be submerged underwater.

I think we tested them in the compression machine at 1, 3, 7, 28 and 56 days. The machine presses down until the cube cracks and the PSI is recorded.

I would guess that a local company that has a concrete testing lab might do this for you. The finished product had to meet ASTM standards since it was used in roads and bridges. Even then you cannot prove the pile of cement they left behind was the same as what they used in the pour.

Good luck.

Just to be clear I believe this is ASTM C109 "Standard Test Method for Compressive Strength of Hydraulic Cement Mortars" with of course cement mortar being one component of the concrete mix. I believe the OP misspoke when they said the leftover material is cement rather than concrete.

 

[jonesg]

ignorant, as in "not knowing" , people get drawn into legal battles and paying huge legal fees because they don't know how to use a lawyer, yes they can easily get roped into paying $7500 . Lawyers are good at that when clients don't know much.

 

[NDJ]

ignorant, as in "not knowing" , people get drawn into legal battles and paying huge legal fees because they don't know how to use a lawyer, yes they can easily get roped into paying $7500 . Lawyers are good at that when clients don't know much.

You show me a lawyer that will write a letter for $75. Total price including all consultation. I'll wait.

 

[BigGarage]

If you were making & testing 2x2 cubes ... was that brick mortar or concrete for a slab?

We tested cement that would often be used in road construction so it had to meet standards.

We never tested mortar. Nobody drives on mortar.

Dennis

 

[BigGarage]

I believe the OP misspoke when they said the leftover material is cement rather than concrete.

Very possible but I'm not sure I believe anything in post #1 anyway.

Dennis

 

[NDJ]

ignorant, as in "not knowing" , people get drawn into legal battles and paying huge legal fees because they don't know how to use a lawyer, yes they can easily get roped into paying $7500 . Lawyers are good at that when clients don't know much.

Hello, Im still waiting ??

 

[gsmith22]

keep the concrete wet for the next week so it can cure properly. that will get every bit of "psi" out of it regardless of what was speced/delievered. not proper curing is the best way to end up with a low compressive strength even if a high compressive strength was spec'd and delievered

 

[FL Guy]

Get some cores pulled and tested. I did and paid for 3000 psi concrete. I ended up with less than half of that

 

[i4ni]

I worked on a 5 year project where we had 40, 100 ft deep caissons inside a coffer dam that were filled with "flo fill" that cured under water for over a year and I swear that stuff was some of the hardest material I've ever had to break. They were 6' across with about a dozen or so 100 ft long # 18 rebar (2 1/4"od) in each caisson. We excavated down 72 feet and had to break out all that flow fill to about 68' down. That flow fill cured to an unbelevable hardness that wasn't engineered correctly for that long of an underwater cure. This was a $400 million dollar project that in the end was crowding a $Billion. I made a ton of money on that project 18 miles from the house.

 

[AEAdam]

Hope this helps: concrete strength and durability is complicated. A customer with a little internet info (not an accusation) may request high strength concrete thinking that will make their project better. But it doesn’t necessarily. How the site is prepared, how the sub base was compacted, drainage, cure temperatures, time of year, direct sunlight etc, all play a roll. Contractors find themselves in these positions with customers where they need to explain 20years of experience to someone who read something on a web forum and is now dictating how they want them to perform the work.

”I don’t want it to crack so I need saw cuts”. Well, all concrete cracks. The saw cuts don’t stop that. But customers don’t want to hear that.

The root problem is the internet. We now have access to all these horror stories of people getting ripped off. So we believe we must take steps so WE don’t get ripped off. It’s the back story behind nearly every GJ thread. Where was this made? Where was it really made? Is it good quality?

Wouldn’t it be great if you could hire someone and trust them to do a good job? My advice is to get references. Don’t choose contractors by price. The cheapest could be the best. The most expensive could be the best value. I agree it’s hard. Then trust them and hold them to account for the finished project, but don’t get involved telling them what to do or how to do it. If that’s where you think you need to be, find another contractor.

Unless you are storing an Abrams tank in your garage, you don’t need 4500psi concrete.