How do I know if concrete ordered is proper strength

I am planning a deck that will require 1.26 cubic yards of concrete for round forms as support and I was currious how do I determine the strength of the concrete they will bring me. I would'nt care but a portion of the deck will be 10 feet off the ground and want my family to be safe.

Tell the concrete co. the above paragraph so they know what mix to give you then ask them what if any contingencies you need foresee.

I'm assuming you're just building round footings to support wood post. You don't tell us the height of the concrete footings/columns . If you're building the footings a foot or so above grade, you would not have an issue. If you're planning on building concrete columns then you'd need to insert re-bar or a wire mesh cage to re-inforced the concrete if not the concrete can fracture and crack. Vertical concrete needs re-inforcement. In any case order 3000 lbs. test concrete.

Are you using round pre-manufactured forms such as Sono Tube and if so what diameter. The footings should be at least 42 inches below finished grade especially if the ground can freeze where you're located to prevent frost heaving

Yes it will be round forms and I was planning on the 2 forms that will hold the section of deck at approx. 10 feet above ground will be 12" forms. Being that I live in Brooklyn and the last few years have not been cold does it still have to be 4' in the ground?

For ~2 yards of concrete I wouldn't even waste my time or a company's. Just mix it your self or grab a couple bags of ready mix. Most concrete companies won't waste their time unless you need 6 or more yards. You could always ask for a "hot" load of 2 yards it will be dirt cheap sometimes even free if you know someone. I would be more worries about the quality of the material in the actual decking then anything else.

You need to make sure you tell them how much weight is going to be on the concrete from that second (upper) deck. If you have the time & background, check out http://en.wikipedia.org/wiki/Compressive_strength , and do your own calculations. Most likely, the concrete company will be familiar enough with the situation that it isn't a worry. But if you are going to have any extra weight on that upper deck, then you should make sure.

Design of reinfrced concrete elements, by Patricl Morrell. Available from Amazon $48. hope it helps.

Regards JD.

You only "Have our word . We are professional,trustworthy--with proven Track record".

As bwire said, instead of telling orally, it would be always better to specify your requirements clearly in writing and ask the company to supply concrete of suitable quality. If you are not fully conversant with the technical terms to specify your requirement, it would be advisable to call the company's representative to discuss your requirement and supply suitable concrete mix. It is possible that the company may charge you higher and / or supply better than required grade of concrete to play it safe. You can compare prices from different suppliers. After this, you can only hope that the company sticks to it's reputation. If not, preserve the bill to take the company to court. Testing the concrete will be a bit too expensive and may not be worth it.

Other alternative is like mukulmahant suggested and most of us do, accept that the company knows better and hope the product works fine.

"You say I started out with practically nothing, but that isn't correct. We all start with all there is. It's how we use it that makes things possible." -- Henry Ford

Most concrete company in Pennsylvania, that have state approved material will carrier a maturity meter. It is used to determine the strength of the concrete with out have to take cylinder samples.

You should contact your local concrete producer to see if they have one.

For the amount of concrete your pouring ask for 2000 psi - 3000 psi mix, place it in some pre-formed tubes, and keeping it constantly moist for 7 days. You should have no problem putting a deck on it. It's not like your building piers for a bridge for major highway traffic. Your combined weight with people and lumber might equal a car. It should be no problem for a couple of well supported posts and a deck anchored to the house to keep you and your family safe.

Don't add additional water to the mix and it will be stronger.

If you are looking for 2500 psi concrete, it will probably end up much stronger than that.

Another important thing to consider is cure time. Concrete may harden after a specific period of time. Additives are often used to shorten or lengthen this time.

Generally concrete takes a 30 days to cure to 100% of its designed hardness.

I'm a Sensor Engineer myself, but here is a comment from my son who is finishing up his 2nd year in Construction Engineering at Purdue:

I do not know about registering, but really you can just tell him that it's not really something he needs to be worried about.

You can order different mixes with different strengths from the concrete company you are using. As to what mix is right for you, it will depend on the amount of weight that you deck will be placing on these supports. In regards to making sure they bring you the correct strength, it would be a costly precaution to hire a third party company to test the concrete. This is usually done in large scale building construction where the concrete will be experiencing forces much closer to its actual designed capacity. In cases where a truck does not meet specifications, it is turned away and usually sent by the company to a smaller residential job where testing will not be performed. Just tell the company what you are using the concrete for and I am sure they will set you up with some crete that will work just fine. It is not the type of concrete that you need to be so concerned about. You are only dealing with compression forces from a

(wood?) deck. These supports will probably have the largest safety factor out of any aspect of your deck and will hold up 50 of your decks and be just fine. Just make sure when you pour the concrete that you are mixing it well and that these supports are deep enough to resist any moments.

Hello friend, you're obviously not a civil engineer, so get one in. There's more to know about flying concrete than you can imagine. If you don't know, you're probably going to get it wrong. Save your family!

Why go all through that trouble for < 2 yards of concrete that a mix plant more then likely won't ship you. It's going to cost the guy an arm and a leg for all they extras you want him to do. I've been in the heavy construction materials business for over 14 years, and for this kind of work all you need is water, stone and a couple of bags of ready mix and your set. Too much over engineering going on here. Stay away from a civil engineer and go with a home contractor that has the expertise or just do it yourself it's not rock science here.

I offered this advice because he asked and these are good suggestions for the readership who are interested in concrete. Personally, I mix my own concrete for small projects around the house. Remember this is a discussion forum and by definition things get discussed in discussion forums. A Contractor certainly could be hired for this small job. No argument. Since you introduced "rocket science" into the discussion, I'm going to have to give you an off-topic grade. I'm not sure how this remark came about in the context of concrete. I got nothing against Contractors but I do not like wise asses.

Why confuse someone who doesn't know about with QC practices of concrete. For large projects yes please do so, but with such a small project it doesn't need to be done. It's not being a wise asses its called common sense why engineer the 1.26 yds concrete in his project for supporting a high-rise building. Like I said before, a concrete plant will not batch 1.26 yds for one individual, they will fill up a truck with 8 yards and make multiple deliveries. They will not guarantee the strength for the material, because of the time limit. So more the likely he will end up with a hot mix anyway. I've managed four concrete plants already I know how the game is played and this guy will end up on the short end, he's better off and cheaper just doing it himself.

Again, and for the last time, the OP mentioned that although the project was a small one, he wanted to know how to do it right and I offered some suggestions. I HATE 8- inch slump concrete even on small jobs! The post did say rocket science originally but was edited within the 1/4 hour editing limit.

If you read the post he really asks how to determine the strength which can only truly be determined by break cylinders or a maturity meter. A slump is really use for determining workability of the material and is not a reliable determination for strength. It is still a vital part in the QC of concrete along with air entrainment, cleanliness of the aggregates, type of cement, admixtures, etc. I just shot this link off to couple friends of mine in the ACI (American Concrete Institute) they feel as I do that that for such a small amount of concrete it is unrealistic and over kill to hold anyone to a strength requirement. With the concrete being placed in a tube; adding some re bar; aggregate at the bottom; and some ready mix plus a 4 feet cylindrical hole it should have no problems with strength and holding up a deck.

Keep in mind that the OP is in Brooklyn, a borough of New York City - not the ideal place for guaranteeing that concrete will be of proper quality, if history is any guide. Agreed, actual strength needs to be determined from testing cured samples, but I think odds for getting a decent mix delivered improve with stating requirements to supplier up-front, and saying that you want a slump test suggests that you are serious in a way that throwing yourself on their mercy never will! Calling for air-entrained 3000 psi may do the same.

Problems with Testing:

1st problem: Who's going to do the testing? The owner no he can't he is not ACI certified there fore his findings will not hold-up in court and the company will laugh at him if he wants his money back. The companies technician who might be certified can you trust him probably not, I mean you don't trust the company right. That leaves a third party ACI certified concrete grade 1 tester, it going to cost you big money there.

2nd problem: Which company to use? 100% of the companies will not guarantee there concrete for strength for only 1.26 yards. You inform them of the technician, the company says one of three things pound sand, your price is now doubled, or since you are certifying this load you will have to take 8 yards a full truck load. Plus their tech will be there taking samples.

Solutions:

Follow what I stated before make your own concrete with ready mix.

Talk to a company about getting a state certified mix, its going to cost more but cheaper them above but does have a limited type of guarantee for strength, you will also be on their time schedule, because of breaking up the load.

Lots of suggestions; many are interesting and worth trying, if you have enough time to spare. Your application appears to be not very critical with only compression load, not very high. Any contractor should be able to do the job using standard concrete mix. But, I think it is important to know what is being done and why is it done? You are doing that, so relax my friend...

Are those Magic Mushrooms?

Among other things I will probably never again touch concrete or any of the other things discussed here, at least not unless asked by a friend not yet retired.

Nonetheless, although I am sure Rhodesrunner never dreamed of all the complexities of concrete discussed here, and even if he takes the simpler roads suggested here by some, I'll bet he is gratified to now have all this information no matter what course he takes.

I must say for myself, that although no longer engaged in industry as the maintenance tech I was, I sure as hell am gratified to have acquired, from this discussion, all the information set out here, if only cause it pleases me.

On the other hand, although I touched not a thing, I was happy to use my knowledge to help out a friend who was confronted by, again a relatively little thing, a collapsed tile sewer in a residence he owns.

That is the value of this site. Questions, no matter how ignorant or unknowing the questioner, often produce expert answers thoroughly covering the subject, naysayers aside.

I now know more about concrete than I ever dreamed there was to know.

Thanks.

j.

Ok I think I have the answer to my problem.First $ concrete co will deliever 1.5 yrds and not 1.26 it will cost any where from $240 to $450 every body says only 3000lbs psi. but it will cost less to rent a 4 bag mixer and buy 80 lbs bags rated at 3500 psi from sakrete co. So thank you all for your wonderful advice it was truly a learning experience that will not be forgoten. Plus with a concrete co I will have to either pump it in though my tennants apt. or wheel barrel from my back yard neighbors driveway which is 150 ft long and I dont want that , its just a deck. Again thank you all Mark R.

Good choice, good logic! No, you don't want to pump it through your (soon to be former if you do) tenant's apartment, that would be rude. And you sure don't want to wheelbarrow it down a 150' driveway next door, that would be silly. Since you don't seem to be either, it's now a question of cost.

Here, we buy ready-mix to spec by the hundreds, sometimes thousands of yards, so we get a much better price than that, but if you can rent a mixer, buy some bags, and d-i-y for less, it starts to look obvious. We have a d-i-y forum here, so pictures and a story would be welcome when you're done.

Two bits of advice - if you have an acquaintance, even a friend of a friend, who has ever "slung mud", offer all the beer he can drink to act as technical advisor on the work site. It will go easier with some guidance! And don't try to mix all of the concrete at once. You are doing two piers, correct? Do them one at a time. You'll know why by the time you have half the concrete for the first one shoveled into the form...trust me on this.

no I am doing 20 8" dia. round footings and 2 12" dia round footings only 3" above soil and approx. 36" deepor deeper when I found out my frost line.

Gotcha - my point is, don't get carried away with it. Concrete starts to set up as soon as it gets wet, and if you end up without enough shovel power to unload it all you got one bad mess! (It starts out heavy, and gets heavier as the day goes on - I think it attracts gravity or something...)

Did you check with your zoning office 8" seems a bit on the small side? We're required no smaller then 12" pillars for decks in my part of PA, I'm just saying to check because it would really such going through all that work and a zoning officer tells you to ripe it out because its two small.