concrete technology 1

[cvlenv]

hi guys...

just wanna ask : is the hammer test results, say an average of 3500psi corresponds to 3500psi compressive strength of the concrete structure?

we conducted the rebound hammer test for an RC wall with a specified compressive strength of 3500psi @ 28days...the age of concrete is about 120days. base on the results,we are getting about 4130psi...

was the average test result in compliance to the parameter or specified strength?

thank you for any advise and insights...

 

[Ron]

Do NOT use the rebound hammer to determine compressive strength of in-place concrete. Even though there is a scale on the side of the device, the correlations are very general and not accurate.

The purpose of the rebound hammer is to assess uniformity or consistency of the hardened concrete. That means that you do a grid survey with the hammer and determine the relative differences in the results so that you can group like results together and delineate different placements or characteristics of the concrete.

To determine the compressive strength, you then need to core the concrete and test the cores.

I don't know which standards you are using for your testing, but in the US, the standard is ASTM C805, which specifically warns against using the rebound hammer to assess compressive strength.

 

[dik]

As Ron noted, there is little confidence in the Schmidt hammer testing... Why are you concerned about strength?

Dik

 

[BigH]

Please do a search of Eng-Tips - this has been discussed more than a few times with detailed comments. You'll learn more from the older threads . . .