Concrete Design Strength

I'm not a civil engineer, but, if I order 4,000# concrete and you deliver 3,500# concrete, I'll probably send it back. What does your specification say. It should at least cite a test. By looking at the test, you should then understand what the numbers mean.

If you are trying to see if you can "get by" with 3,500# to save money, don't.

My guess is, since you can't test liquid concrete for compressive strength, the 3,500# figure is for properly cured concrete.

Good Luck

The tricky word here is "can". It "may" achieve 4000psi. However, the design should be for 4000psi mix and you should pour the necessary test cylinders and test them to verify the compressive strength after curing. If the job specs call for 4000psi concrete, that's what you should be pouring. Well, that's my two cents.

If you are trying to make already poured 3500 psi concrete achieve 4,000 psi in situ then the answer is yes it can be done.

a capillary crystalline reactive product such as xypex Concentrate or Kryton Krystal will increase the compressive strength of existing,already poured concrete.

Can you explain how waterproofing concrete can increase the compressive strength?

yes.

Even though one of the results is to waterproof the concrete and to make it more resistant to chemical attack, the fact is that it also increases the compressive strength after the fact.

When concrete hydration occurs there are cement gels which are left over from the hydration process. This is in any concrete whether it is one day old or 100 years old. The chemistry of the product is drawn into the capillary tracts when applied correctly by the van laars priciple and reacts with these unhydrated cement gels forming dendritic fibrous crystals within said capillary tracts.

The increase hydration leads to stronger concrete.

#2, Dry concrete is stronger than wet concrete.

#3. the pores and capillary tracts are filled with essentially an 11,000 psi crystalline structure instead of air.

There are three ways. I could explain more but that should be enough for a free forum.

That's plenty for me. Thanks.

In my experience, if the design calls for 3500psi, the redi-mix plant is required to send a mix that meets that requirement, they know it will be tested, so they have a mix that is SURE to reach that strength in 28 days. If the concrete is poured at or less than the max design slump, our concrete supplier's product will reach 4000psi. To be sure though, just order 4000psi in the first place, a little added cement cost is WAY less than replacement cost!

Hi,

the design strenth of concrete is always have target mean strength,it will give higher than for what it is designed but it is not sure that the same result can be expected.

Once we designed a mix for 3500psi we can expect the same only after proper curing.

kgb

WELL YOU HAVE ABOUT 20 PERCENT OF THE INFORMATION HERE! IT CANT BE ANSWERED WITH WHAT YOU HAVE HERE! NUMBER ONE YOU MUST USE THE SPECED PSI ON THE CONCRETE! NUMBER TWO WHAT IS ON THE ISOLATED FOOTINGS A FEATHER OR THE WHOLE PLANT? AND WHEN YOU ARE DOING POWER PLANTS THEY MUST BE BUILT TO SPEC!!! THE GROUND IN FLORIDA CAN ALSO BE A PROBLEM I SPENT 8 YEARS IN FORT MYERS FOR A FIRM AND YOU MUST LOOK AT YOUR SOILS REPORT ALONG WITH YOUR SPEC'S FOR YOUR PROJECT!!!!

Thanks guys,

All of your comments were truly appreciated. My final decision was to just order the 4,000. Better safe than sorry.

Islander - the simple answer is yes it can, but it can also only obtain 3,000.

are you willing to risk going the wrong way in crossing your fingers? No.

if a mix is specified, why would you consider ordering less? I am interested not in the question you asked, but why you would have asked it. has the pour ALREADY been made and you are concerned over the quality of material or are you trying to save penneys? If you were supporting the roof beams of the building after the concrete was place and there were interior columns spec.d to be square tube steel of 5/16" steel, would you be writing to ask if 3/16" would hold up the load? Probably not. You would expect to see 5/16 steel when the columns are delivered, thus I must ask: why your question was posed in the first place?

For sure it will be more than 3500 psii after 28 days and it may be over 4000 psi provided that the quality of concrete is according to proper specification and appropriate curing was done. Using ready mix concrete and on-site mix concrete will also spell the difference.