Concrete PSI

You need to designate how these values are determined.

Are they tensile strength values?

This is not my area of expertise, but, noting the lack of response, you have not given enough information to engender a cogent response.

-m-

The compressive strength of concrete depends on the following:

1. type of fine and coarse aggregates use

2 type of Portland Cement use for the application.

3. proportioning

4. amount of water, admixture (if needed)

Do a trial batch, proportion by volume of fine and coarse aggregate to a bag of cement. Add a measured volume of water (moisture content will influence the amount of water needed for the mix), for required slump depending on application. Record slump with corresponding mix proportion. Make several concrete samples on a 6" x 12" cylinder mold. Cure 3 samples for each batch for testing compressive strengths @ 7th, 14th and 28th days. Note compressive strengths at each testing of different samples will establish a trend on the strength of each class, but the result @ 28th day will be the allowable compressive strength. Redo and/or adjust concrete mix and repeat testing when desired results are not meet.

Hope this helps.

Search concrete mix designs on google, I didn't have time to check it out. I am currently batching conrete on a remote site myself in large volumes, and performing break tests on 150mm Cubes, 7day breaks were just under 4000psi and 28 days were around 5500psi. The

The mix design is below this was for a 4000psi mix. My Slumps were 4 to 5 inches.

- Sand = 753 kg/m³

- Aggregate #8 / 25mm = 690 kg/m³

- Aggregate #3 / 10mm = 483 kg/m³

- Water = 260 l/m³

- Cement CP2 350kg/m³

Plasticizer 1.5 - 2Ltr per m3³

You would probably be very interested in the post I came across recently regarding a new super concrete out of Iran. During a contest hosted here in the states, the Iranians were able to build several samples of UNREINFORCED CONCRETE that had a 28 day cure strength of 50,000-60,000 psi. That's 2x that of most granite!

The article can be seen here:

http://blog.wired.com/defense/2007/04/irans_superconc.html

According to wikipedia, the mystery on how to form Roman style concrete was lost for over a 1,000 years!?!?!? The twin tours in Kuala Lampur are made with a custom high PSI concrete they worked for months to perfect using only local materials.

Unfortunately, I don't know of a guide or handbook that will give you what you are asking for since it is more complicated than that. How you cure your concrete can be as important as the recipe. Keep searching though and you may find someone who knows of a rule of thumb that might be helpful.

Regarding concrete that is in the neighborhood of 50,000 psi, it would take more than an article to convince me. Given the fact that Quartz has several faces when chrushed and it has a very high resistance value this would certainly increase strength of concrete, regarding steel fibers it is my opinion that these fibers may be subject to corrosion if they are place through out the concrete mix, all concrete has some sort of surface cracking, any oxidation of the surface that effects the steel fibers would cause oxidation. The reason we epoxy coat important reinforcing in structural concrete on overpasses, bridges, piers etc is to prevent this oxidation.

Having set up several batch plants and having poured concrete for tilt ups, pre cast pre stress piles and pier structures the highest breaking strength that comes to mind is the 8000 psi range for piling when we used steam curing, imported aggregrates from Canada, 800# concrete per Cubic Yard, plasticizer, and calcium nitrite were used along with other water reduction chemicals in the mix.

Any other facts about the ultra high strength concrete, or where one may see a demonstation of this concrete would be highly appreciated.

The Iranians typically have a tendency to be overly generous with thier accomplishments. This is not to say they are not accomplished in several fields, they are, but they are not nearly as good as they typically brag about being.

I did spend about 3.5 years in southern Iraq about 20 kilometers from the Iranian border. I do know this for a fact, they brag, they play very dirty, they lie about many things, one of which the fact that they do not import munitions to the various Shia Malitia's in Iraq that blow up our Armed Forces.

Rick

There are a lot of varibles that affect the strength of concrete. Weather, moisture in the mix, the strength of the rock, the smoothness of the rock all play a vital part. However, the biggest thing is the moisture of the mix. The mix I specify is 4000PSI mix with a mid range water reducing agent and air entraintment (for cold weather preformance).

Pure and simple the more water you add (workable) the weaker the concrete. Most people who lay concrete for a living will add water to make the mix more workable. WRONG!! This makes the concrete very weak. Adding only one gallon of water can change a 3500 PSI mix to a 2000 PSI mix and make it very suseptable to freeze thaw. This usually also separates the aggregates. You can see this when the concrete gets "soupy". Concractors like this because it's easy to work when they don't have the larger stone to work around and it is not as thick.

Fortunately they make a variety of addatives just for that purpose. One easy to come by addative is latex. I can add workability without reducing strength much.

The follwoing is a link for mix design. transportation.ky.gov/Materials/download/Concrete%20Mix%20Design/CONCMIX.xls

Try this web site:

http://www.concrete.org/general/home.asp

It is to the American Concrete Institute, they should be able to answer your questions.

Hello,

It is not possible to use an equation regarding concrete compressed strength. There are too many variables, such as the R value of the rock, (resistance), how clean the aggregrate is when it goes into the mix, quality of sand etc. Each area you make concrete with different materials have thier own personality. As a general rule of thumb, the more cement you use and the less water the higher the compressed strength of the concete.

As on of the earlier posts mentioned, a trial batch using various combinations of aggregrate, sand, cement and add mixtures will give you the value of the concrete.

Rick

GENERALYYYYYY speaking 4" slump ordered out @ 5 sacks per cubic yd is 2500 PSI ....................................................................5.5 " " 3000 psi ....................................................................6 " " 3500 psi and so on

Unfortunately, the quality of the rock used in concrete, how clean the rock and sand are introduced to the mix have quite a bit to do with ultimate compressed strength of the concrete.

In good conditions 5 sack 3/4, with 4 inch slump may produce 4000 pound concrete.

What part of the world are you in? I am not an engineer, I am a construction manager/supt. who has traveled through a lot of the U.S. working in many areas, and have also done some international work. There are some things you can do that will improve the quality and strength of the concrete with chemicals such as plasticizers and water reducers.

Sorry there is not a specific answer to your question that fits perfect.