Concrete Compressive Strength, Cores & Fresh Concrete Testing
Concrete quality is verified in two phases: fresh-concrete tests at placement (slump, air content, temperature, density) and hardened-concrete strength tests on cast cylinders or drilled cores. Results feed acceptance decisions against the project specification, not against the test method itself.
What does it measure?
- Compressive strength of cast cylinders (ASTM C39)
- Strength of drilled cores, with length-to-diameter and moisture corrections (ASTM C42)
- Slump / consistency of fresh concrete (ASTM C143)
- Air content by pressure or volumetric method (ASTM C231 / C173)
- Density, temperature and unit weight of fresh concrete
When is it used?
- Project QA/QC and acceptance of structural concrete placements
- Assessing in-place strength where cylinder results are questioned
- Investigating low breaks, cracking or construction defects
- Verifying air entrainment for freeze-thaw exposure classes
Sample considerations
- Cylinders must be cast, cured and transported as the method specifies; field-curing versus standard-curing changes what the result means.
- Core locations should be chosen with the engineer of record; reinforcement, depth and member type matter.
- State the specification, required test ages and reporting deadlines when requesting testing.
Laboratories with relevant capabilities
- Sandberg LLP (London, England) — Construction Materials Testing, Concrete Testing, Metallurgical Testing
- Struct Geotech Research Laboratories (Bengaluru, Karnataka) — Construction Materials Testing, Non-Destructive Testing, Concrete Testing
Frequently asked questions
- Cylinder results came back low — what next?
- Common next steps are reviewing curing and handling records, testing companion cylinders, and coring the structure for ASTM C42 evaluation. A petrographic or forensic review may follow if distress is visible.
- Is slump a measure of concrete quality?
- No. Slump indicates consistency of a given mixture; it does not verify strength, durability or that the correct mixture was delivered.
Confirm standard edition, jurisdiction and actual laboratory scope. Service references are not partnerships or endorsements.