## 7 Days Compressive Strength of Concrete

## 7 Days Compressive Strength of Concrete

(OP)

Concrete usually attains about 90% of its compressive strength after 28 days. What is the approximate 7 days and 14 days compressive strenght of concrete as a percentage of its ultimate compressive strength?

## RE: 7 Days Compressive Strength of Concrete

## RE: 7 Days Compressive Strength of Concrete

In general, using Type I Portland cement, you can expect about 65 to 70 percent of the 28-day strength in 7 days. Not to many consistently reliable estimates for 14-day strengths, since it isn't usually a measured parameter.

Many reactions affect the strength gain of concrete, so you really need historical data on the mix you intend to use.

## RE: 7 Days Compressive Strength of Concrete

## RE: 7 Days Compressive Strength of Concrete

You may check the links below :-

www.uwtc.washington.edu/courses/ 231/documents/StudentexampleRR.pdf

www.tkproduct.com/Curing%20Concrete.PDF

## RE: 7 Days Compressive Strength of Concrete

f'c(t) = f'c(28) * { t / (4 + 0.85t) }

where f'c(t) represents the compressive strength at age t and f'c(28) represents the specified 28 day strength.

For type III cement, use (2.3 + 0.92t) in the denominator.

Reference document is the textbook "REINFORCED CONCRETE Mechanics and Design" Second Edition by James G. MacGregor.

## RE: 7 Days Compressive Strength of Concrete

Also, keep in mind that early strength is dependent on heat of hydration of the cementitious materials in the mix design. If you have a large quantity of fly ash or slag in the mix, calories per btu will be lower resulting in deferred strength to later ages, i.e. 28 or 56 days.

Hope this helps. It is huge in times of cement shortages.

Fred J. Croen, RSM

Engius, LLC

Boston, MA

www: engius.com