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                                The Great Concrete Curing Controversy

We are having a new concrete driveway and I need to know how long to wait until we can drive on it

The books say 28 days to reach full strength

Others say 3 to 5 days to reach 50%        But Tikay says its 95% in 24 hours

How long does it take,,, heres a few Yahoo answers

Have you buried Tikay under your driveway? That why we don't see him anymore?

i remember reading a boring fact that was a bit wow.

some of the concrete in the hoover dam won't be fully set for a 1000 years (not 100% thats correct but it was a big number)

my advice would not to drive on it for 7 days for cars and 14 days for bigger vans

Tikay is closest!

If you want to be safe don't drive on it for 3 days or walk for 1 day

surely you just ask the person that did the job

how long until you can't write your name in it with your finger?

I did have a long chat with Tikay about this and he says concrete is strong enough after 24 hours.

 My builder says the longer you leave it the better

Don't want to drive on it too soon and crack it,lol

Curing is one of the most important steps in concrete construction, because proper curing greatly increases concrete strength and durability. Concrete hardens as a result of hydration: the chemical reaction between cement and water. However, hydration occurs only if water is available and if the concrete's temperature stays within a suitable range. During the curing period-from five to seven days after placement for conventional concrete-the concrete surface needs to be kept moist to permit the hydration process. new concrete can be wet with soaking hoses, sprinklers or covered with wet burlap, or can be coated with commercially available curing compounds, which seal in moisture.

from http://www.cement.org/basics/concretebasics_faqs.asp

cracking in concrete is caused by shrinkage and not compresion (unless you are talking about significant overlaoding and poor sub ground conditions). Hairline cracking would be common place unless you cast in failry small sections. Drying too quickly can also cause crazing of the surface, but this is aesthetic and not detrimental to the loading capacity of the slab.


The "as long as possible route" really is only if you are going to be applying unusually high loads to be honest.

To discover the truth about concrete.

I have joined the Concrete Society and have read many back issues of Concrete Magazine online

I joined their forum , and asked the members how long does concrete take to set

Heres their answer, first you take concrete cubes then

A two-step method for converting a concrete core compression test result to the in-place strength of the corresponding volume of concrete is presented. The strength of a non-standard core is first converted to the equivalent strength of a standard core, and then the standard core strength is converted to the equivalent in-place strength. Strength correction factors required for these conversions, obtained from weighted linear and nonlinear regression analyses presented elsewhere, are summarized. The accuracy of the predicted in-place strength is affected by the inherent error of the core strength measurement itself, and by the uncertainty of the various strength correction factors. It is shown that confidence intervals on the estimates of the strength correction factors obtained by regression analysis underestimate the true model error because the underlying models are imperfect. Instead, the accuracy of the strength correction factors is determined by a weighted regression analysis of ratios of observed-to-predicted values which accounts for the non-uniform variances of the dependent and independent variables. The coefficient of variation of the in-place strength predicted from a test of a 100 or 150 mm diameter core is between 4 and 5.5.%. If the in-place strength is predicted from a test of a 50 mm diameter core, the coefficient of variation of the predicted in-place strength is approximately 12.5%. These error estimates do not account for possible variation of in-place strength throughout the volume of the element being cored.

So now I know

Is that a yes or no


The Concrete Society's Head Office is,   Concrete House     Crowthorpe  lol

Cia has a better link ( See above ), they say 2 years is best , but 28 days will do

copied from the link   http://www.cement.org/basics/concretebasics_faqs.asp


 What does 28 -day strength mean?

Concrete hardens and gains strength as it hydrates. The hydration process continues over a long period of time. It happens rapidly at first and slows down as time goes by. To measure the ultimate strength of concrete would require a wait of several years. This would be impractical, so a time period of 28 days was selected by specification writing authorities as the age that all concrete should be tested. At this age, a substantial percentage of the hydration has taken place.

I will park the car in the street for a few weeks then. lol

Crow  - trust me here - im a chartered surveyor

The stuff you are reading from the CS is to do with formal testing of concrete.

Under commercial contracts concrete is specified to achieve certain compresive strengths. When you pour the concrete you take "cube" samples - and test them a 7 and 28 days (and 45 days if abs necessary due to a poor result). This is a requirement of the contract.

Now trust me here - only once in my career has a 7 day sample failed, but then we got a satisfactory result after 28 days.

your drive is going to be "dig a hole mass pour concrete probably with a little bit of steel re-bar". the concrete will "feel hard" after a few hours. You will be able to walk on it the next day. You will notice no difference between day 3 and day 203!

Crow  - Trust me here - I'm a know it all.

Leave it 2 years or you'll be waking up one morning and your car will have sank.

only trying to save him hours of boredom dealing with the CS folk!

made me rotflmfao

Thanks for all your help on this one

Heres a few pictures of Concrete thats not hard enough to drive on

When your concrete is hard enough to land a plane on

Dont put a plane on your roof rack

And finally,

As Cameron announces the new cut backs

The police are shown their new patrol cars