Concrete drying time

[Larry Caldwell]

what is your source of this information...?

the compressive strength of concrete is relative to the water/cement (portland) ratio...keeping it wet will enhance the curing but it will not likely "double the strength"...

Curing Concrete | Concrete Technology | Portland Cement Association (PCA)

You are correct. I misread Figure 1. Moist cure for 28 days only increases concrete strenght by about 50%. You have to moist cure for a year to double the strength.

 

[/pine]

Curing Concrete | Concrete Technology | Portland Cement Association (PCA)

You are correct. I misread Figure 1. Moist cure for 28 days only increases concrete strenght by about 50%. You have to moist cure for a year to double the strength.

I wonder how much the tensile strength is increased after a year's wet curing ?

 

[orezok]

Being in the school construction business, I supervise pours totaling 3-4,000 CY per year, about half structural concrete and half flatwork. Being a state agency, we are required to make cylinders for testing from every pour. A minimum of 4 cylinders to be broken one at 7 days, two at 28 days (the design parameter) and a hold for 56 days if the 28's don't make strength. We make cylinders from the first truck and additional sets for every 50 CY.

Since we are in earthquake country, and since the safety of kids is our highest priority, our typical structural concrete is 4,000 PSI and out flatwork is 3,000. We use a .45 water cement ratio for corrosion resistance and usually a 3" to 4" slump. Remember, schools have to remain structurally sound for more than 50 years.

We do a 7 day water cure either by full flooding or mats.

The bottom line is that 90% of all breaks will reach 80% or greater at 7 days and 125% at 28 days. It is not unusual to see breaks up to 6,000 PSi at 28 days.

Now this is not your usual run of the mill concrete and we are required to have a plant inspector at every batching, but it is typical for most concrete.

 

[SPYDERLK]

The bottom line is that 90% of all breaks will reach 80% or greater at 7 days and 125% at 28 days. It is not unusual to see breaks up to 6,000 PSi at 28 days.
Now this is not your usual run of the mill concrete and we are required to have a plant inspector at every batching, but it is typical for most concrete.

Pls elaborate on this statement. Exactly what are you saying.?
larry

 

[Jimmy Joe]

We just had a floor poured at work, It was poured 6:30 am on a Saturday and we were driving forklifts on it at 5:00 am the following Monday with no problems so far. They said it was a seven bag mix, whatever that is. I think a regular mix is called a 5 bag mix. I think in 2 days a four wheeler would not have any effect unless you had studded tires it may score it more easily.

 

[blueriver]

They say the Hoover Dam is still "curing".

Here's good article for all to enjoy.
CONCRETE: HARD FACTS. DURABLE STRUCTURES

Concrete in water continues to cure ... as long as it remains under water it continues to strengthen every minute.

 

[MikeD74T]

Pls elaborate on this statement. Exactly what are you saying.?
larry

The "breaks" he's refering to are test samples that are taken at the jobsite, cured, and crushed at specific cure dates in a lab. MikeD74T

 

[orezok]

Pls elaborate on this statement. Exactly what are you saying.?
larry

Concrete test cylinders are typically 6" diameter by about 15" high. They are prepare by a certified inspector according to ASTM specifications. At 7 days they are placed in a hydraulic press and crushed. The pressure to crush them determined the compressive strength of the concrete.

Ninety percent of the 7 day breaks will reach 80% of the design strength. i.e. 4,000 PSI design mix will result in a 3,200 PSI strength at 7 days.

A typical cylinder will take 40 to 50 tons of force to break it.

 

[SPYDERLK]

The "breaks" he's refering to are test samples that are taken at the jobsite, cured, and crushed at specific cure dates in a lab. MikeD74T

Concrete test cylinders are typically 6" diameter by about 15" high. They are prepare by a certified inspector according to ASTM specifications. At 7 days they are placed in a hydraulic press and crushed. The pressure to crush them determined the compressive strength of the concrete.

Ninety percent of the 7 day breaks will reach 80% of the design strength. i.e. 4,000 PSI design mix will result in a 3,200 PSI strength at 7 days.

A typical cylinder will take 40 to 50 tons of force to break it.

Thanks!
:thumbsup:

 

[Freds]

Yeah, it really depends on what kind of concrete you had poured. I was driving on mine after a couple days, but it was "High Early" due to the fact I couldn't wait 14 days for it to cure. My concrete guy said it's not so much the driving as it is the turning of the tires that puts the most stress on it.

Yours didn't give you any guidelines?