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ASTM C192
Standard Practice for Making and Curing Concrete Test Specimens in the Laboratory
Overview
ASTM C192 is a critical procedural standard that dictates the standardized methodology for preparing concrete test specimens—such as cylinders and beams—under highly controlled laboratory conditions. The core purpose is to minimize variability in specimen preparation, ensuring that test results accurately reflect the intrinsic properties of the concrete mix design itself, rather than inconsistencies in how samples were made or cured.
Lab vs. Field Testing
A crucial distinction exists between ASTM C192 and ASTM C31. C192 is used in the laboratory for mix design validation before construction begins, answering: "Does this recipe have the potential to produce concrete of the required strength?" In contrast, C31 is used on the job site during construction for quality control, answering: "Is the concrete being delivered today the same quality as the approved recipe?"
This distinction has significant contractual implications. If field cylinders fail but the original mix design validation showed passing results, the issue likely points to on-site practices rather than the mix design itself.
Specimens and Testing
- Compressive Strength testing per ASTM C39
- Flexural Strength testing per ASTM C78
- Modulus of Elasticity testing per ASTM C469
- Standardized curing conditions: 73.5°F ± 3.5°F, 95% minimum humidity
Performance-Based Specification
ASTM C192 enables modern performance-based concrete specification. Rather than prescriptive requirements dictating exact quantities of cement, sand, and stone, engineers can specify desired performance (e.g., "minimum compressive strength of 5,000 psi at 28 days") and allow producers to design the most efficient mix. This approach shifts focus from means and methods to ensuring desired outcomes, empowering innovation with advanced admixtures and sustainable materials.