Sample Size Requirements


ASTM C 856 "Standard Practice for Petrographic Examination of Hardened Concrete"

Concrete Cores should be 3 to 4 inches in diameter.  For Horizontal concretes (i.e. slab-on-grade, slab-on-deck, etc.) drill through to the subase; for Vertical structures (i.e. wall, etc.) drill through the thickness when/where possible. 


If you are investigating a problem or signs of distress, the sample should contain said distress (i.e. take sample from over a crack, delaminated area, scaled area, etc.)

Report will include everything about:

(a) the concrete and its components i.e. coarse and fine aggregates, paste, and air-void system, along with if there is any issue with concrete per se;

(b) if there is any evidence of improper placement, consolidation, finishing, and curing techniques;

(c) effect of any potentially deleterious deicing chemicals or ‘salts’ on concrete - only if both concrete and construction practices are found acceptable; and

(d) deleterious or unsound component in the concrete.

  • For Scaling, Spalling, and related Issues - Usually, it is either or a combination of lousy concrete and improper construction practices that cause scaling and other surface distress.  Salt aggravates the problem, unless, a magnesium-based salt is used, in which case salt causes chemical erosion of paste and hence scaling (even in a good concrete).  Salt can also cause scaling if it is used at an early stage, i.e. immediately after the placement in a cold weather construction and/or prior to the attainment of concrete “maturity" (i.e. at least a 4000 psi compressive strength and a period of air drying).

  • For delamination and related issues, it will investigate whether air entrainment and/or finishing practices have contributed to the delamination.

  • For popout, mortar lift-off, staining, discoloration and related issues, it will investigate the material(s) responsible for distress, and their location and abundance in the core. Additional SEM-EDS services may be required for such investigation for additional cost.

Please note, our largest saw can accommodate a maximum of 9 inches.  Therefore, any sample exceeding 9 inches in length will be sectioned for sample preparation.  If sectioning of a sample is necessary the locations of all cuts will be noted in the report.

See the Submitting Samples page for a list of information we request with new projects


ASTM C 457 "Standard Test Method for Microscopical Determination of Parameters of the Air-Void System in Hardened Concrete"

CMC follows Procedure B (Modified Point-Count Method) of ASTM C 457, which requires a 12 square inch area for examination.   Diameter and length of cores can vary, provided the required surface area will be available.

Don't See What You're Looking For?

Send us an email describing your project, add a few pictures if you can, and we would be happy to suggest suitable testing and sampling procedures.  Or just give us a Call.



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Berkshire Center
4727 Route 30, Suite 104
Greensburg, PA 15601

Phone: 724-834-3551

Fax: 724-834-3556

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