How do you determine the characteristic strength of concrete?

Answer 1

Strength of concrete is tested by destructive testing of concrete test core samples that are taken at the time the concrete is poured. The test cores are about 7" diameter x 16" tall plastic containers. A number of samples are taken. One will be tested at 7 days, another at 28 days. A test report is provided to the firm responsible for paying the bill. The testing method is: place the core sample (removed from the plastic container), in the test machine; the machine will compress the sample until it breaks. A gauge measures the force applied and at what point it breaks.

Concrete usually breaks at 30-40% higher than the minimum specified, because the concrete company has to guarantee the concrete strength. Concrete strength is specified as: 2500 pound, 3000 pound, 4,000 pound, 6000 pound concrete. Sidewalks and non load bearing loads use the lighter weight concrete, bridges and buildings carrying loads will use a higher strength concrete. The strength is adjusted by adding or subtracting the percentages of the raw materials in the mix; limestone, water, sand, and mortar mix.

Answer 2

the strength of the concrete is cause mainly by the amount of cement we put in the mixture, but there are also some factor that we can consider:

1. batching

2. Mixing

3. making

4. and curing of the concrete.

Answer 3

Depends on the use. If it is used an an insulator a PSI of only 10 will do.

If it is used for a floor slab then 2500 should be a minimum depending on traffic.

If used in a high rise it can be spec'd as high as 25,000 PSI.

Most 5 sack concrete will come in at 3000-3500 PSI depending on water content and other variables.

Answer 4

grading, surface area and shape of aggregates

Answer 5

THE CLIMATE IN THE WINTER.................. THEREFORE U ALWAYS HAVE 2 MAKE CONCRETE IN 10 to 20 degree c. BELOW 0 degree c,THE CONCRTE WILL SHRINK........... MALIK OMAIR{CIVIL ENGR.}