The extraction of cylindrical specimens, whether from a horizontal, vertical, or inclined plane, must be carried out perpendicular to the surface by mechanical means of drilling, once the specified or guaranteed age has been met.
At Q-VER, we prioritize the total quality of the work, that’s why we work hand in hand with the Mexican Standard NMX-C-169-ONNCCE-2009 «Extraction of cylindrical or prismatic specimens of hardened hydraulic concrete», these are the most relevant points to consider:
- For the evaluation and knowledge of the concrete strength, a sample composed of at least 3 specimens must be extracted.
- The diameter of the drill used for extracting the specimens should be 3 times the maximum nominal size of the coarse aggregate.
- The length of the specimens should comply with a length/diameter ratio between 1 and 2.1.
- Specimens extracted from a structure that is dry under service conditions should be cured «dry» for 7 days prior to testing.
- Specimens extracted from a structure that is in complete saturation during service conditions should be submerged in water with lime, at least 40 hours before testing.
- The bases of the specimens should be polished or capped to meet the flatness and perpendicularity requirements established in the NMXC-109-ONNCCE standard.
- The strengths obtained from the concrete cores are considered satisfactory if they meet the following criterion: the average strength of all extracted cores reaches at least 85% of f´c and no individual core presents a strength lower than 75% of f´c.
- Specimens extracted from hardened concrete that exhibit excessive voids or severe segregation are not considered representative samples and should be discarded.
- Personnel performing core extraction work should wear personal protective equipment: goggles, gloves, helmet, boots, harness (for work at heights), and long-sleeved shirt.
Core extraction is an accreditable test method before the Mexican Accreditation Entity (EMA); and at Q-VER, thanks to our technical advisory team, we are committed to ensuring that your project is developed according to established quality standards and tests.
