Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here


Coring Sample

Coring Sample

Coring Sample

Coring of hardened concrete at 12 days ( at 67% maturity ) for cylinder compression test. Is the result reliable as a depiction of concrete strength. Please let me have your suggestions.

RE: Coring Sample

RIZ..that maturity is probably on the edge for potential impact for the cores.  With plenty of cooling water, slowed progress and a relatively new coring bit, it will probably be OK.  Make sure the drill doesn't wobble much if any.  These things usually impact the coring more than the abrasion vibration of the bit.

Be sure to keep the cores wet.  Some specifications allow dry testing of cores if the service environment will be dry.  In my opinion, if you are coring at early times or for low strength confirmation, you don't need the potential drying shrinkage effects, so test them wet.


RE: Coring Sample

Hey Riz.

If you use ACI...check out ACI 318, Section 5.6.5 for their take on field cores.

RE: Coring Sample

Thanks Ron & Jae.
Compressive strenght result of the core is 10 N/mm2. Cube strength thus would be  1.25 x 10 = 12.5 N/mm2.
This is lower than anticipated value of 0.67 x 25N/mm2 = 16.7 N/mm2 at 7 days.

RE: Coring Sample

Riz...under most core evaluation criteria (ACI included), if the core strength achieves 85 percent of the expected strength, it is considered acceptable.  This generally applies to 28 day and later strengths, but could be extrapolated, at least in part, to include earlier strength parameters.

As an example, you cored at 12 days with, I am assuming, a measured maturity of 67 percent.  If your cores achieved 85 percent of that value (0.67 x 25 N/m^2 X (0.85)=14.2 N/m^2)then you would consider that acceptable.  However, early strength gain is affected by lots of "stuff".  The fineness of the cement, the type and quantity of admixtures, whether the cement was modified ( using fly ash, ground blast furnace slag cement, or materials), curing conditions, aggregate influence, w/c ratio, air content, temperature, and probably a few I have left out.  This is a danger of coring/evaluating too early.  The time between placement and about 15 to 18 days is the steepest part of the strength gain curve, so minor mix issue can significantly affect strength gain.  These tend to moderate with time (20 to 60 days.

Your next step might be to get a petrographic examination of a core to evaluate a few of the hardened concrete characteristics that might lead you to a conclusion.

Good luck.


RE: Coring Sample

I am not sure about your codes but the sample size will affect the confidence you can have in your result. So if one core has been taken from a batch of concrete your 95% confidence limit on actual strength of the batch based on that core will be a lot lower than the result you have. This is why using cores is not often a great way to determine the strength of concrete because you need several to make the results statistically significant

Carl Bauer CEng MICE
Bauer Consult
PO BOX 2224

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


White Paper – Data Security and Know-How Protection
Our data is constantly exposed to the danger of being intercepted or stolen as it wends its way over global data networks. Data security measures and measures for protecting intellectual property should not, however, first be implemented when data is exchanged – companies must lay the foundation for these measures within their own organization. Download Now
White Paper – Collaboration in the PLM Context
The influence exerted by the Internet of Things (IoT) means that there is a steadily growing need for collaboration in industry. Partners from new industries and areas of application need to be integrated in cross-company business processes to ensure that the lifecycle of smart, connected products can be managed from end to end. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close