ASTM C31/C31M is the ASTM practice used to make and cure concrete test specimens in the field. It applies to cylinder and beam specimens made from representative samples of fresh concrete for construction projects, and it sets the framework for field molding, initial curing, protection, transport, and later laboratory curing when required.
Because ASTM C31/C31M controls specimen quality before strength testing begins, it directly affects acceptance testing, quality control, and field decisions such as curing evaluation or form removal timing. If you need help matching specimen molds, curing storage, transport protection, or downstream test equipment to this workflow, Contact Us.
ASTM C31/C31M: Standard Practice for Making and Curing Concrete Test Specimens in the Field
ASTM C31/C31M is a practice, not a direct strength test method. Its role is to standardize how field concrete specimens are made, cured, protected, and transported so later test results are more consistent and more useful.
On many projects, this standard sits between fresh-concrete sampling and the later compression or flexural test. That makes it important for contractors, laboratories, inspectors, ready-mix operations, and QA/QC teams that rely on dependable cylinder or beam results.
Quick Definition
ASTM C31/C31M is the field-specimen practice for concrete. It governs how test specimens are made and handled before later testing under the applicable strength method.
What This Standard Covers
ASTM C31/C31M covers procedures for making and curing cylinder and beam specimens from representative samples of fresh concrete for construction projects. It also addresses specimen transport to the laboratory and laboratory curing after transport when that part of the workflow applies.
Document type: Practice.
Specimen types addressed: Concrete cylinders and beams made from fresh concrete.
Curing paths recognized: Standard-cured specimens and field-cured specimens.
Important scope limits: The practice is not intended for concrete without measurable slump or for other specimen sizes or shapes outside its stated scope.
Important exclusions: The practice is not applicable to lightweight insulating concrete or controlled low strength material, and ultra-high-performance concrete work may require modifications and a different companion practice.
Why This Standard Matters in Testing
Concrete strength data depends heavily on how specimens are made and cured before they ever reach a testing machine. ASTM C31/C31M is commonly part of the front end of acceptance testing for specified concrete strength, mixture proportion checks, and routine quality control.
It also separates two different decision paths. Standard-cured specimens are commonly used for acceptance and control work, while field-cured specimens are commonly used for estimating in-place concrete strength, comparing results with other in-place methods, evaluating curing and protection in the structure, and supporting decisions such as form or shoring removal time or post-tensioning timing.
In ready-mixed concrete work, this practice is especially important because project specifications often depend on strength results from specimens prepared and cured in this workflow.
Common Materials, Product Types, or Applications Covered
ASTM C31/C31M is most commonly associated with normal project concrete placed in the field and sampled while fresh.
- Ready-mixed concrete delivered to a job site
- Cast-in-place structural concrete such as slabs, walls, columns, foundations, and other project elements
- Projects requiring molded cylinders for later compressive strength testing
- Projects requiring molded beams where flexural testing is specified
- Quality programs that compare standard-cured and field-cured specimens
Because the standard is about specimen preparation and curing rather than a single load-frame test, it usually appears as part of a larger concrete testing and compliance workflow.
Common Test or Verification Workflow
ASTM C31/C31M is commonly used in a sequence like this:
- Obtain a representative sample of fresh concrete, commonly through the applicable sampling practice.
- Mold cylinder or beam specimens in the field from that sample.
- Protect and initial-cure the specimens under controlled field conditions.
- Transport specimens to the laboratory when the workflow requires laboratory curing or later strength testing there.
- Continue curing as the project calls for, either as standard-cured or field-cured specimens.
- Test the finished specimens under the relevant downstream method, commonly compressive testing for cylinders or flexural testing for beams.
This means ASTM C31/C31M does not stand alone. It supports the quality of the specimen before the actual measured strength value is produced.
Equipment Commonly Used for This Standard
Equipment selection for ASTM C31/C31M centers first on specimen preparation and curing, then on the later test method used to measure strength.
Common specimen-making equipment: Cylinder molds, beam molds, and general specimen preparation and finishing tools used for field molding.
Common curing and handling equipment: Protected field curing storage, temperature monitoring devices, specimen transport protection, racks, and accessories used to maintain condition during handling and movement to the laboratory.
Common downstream testing equipment: Compression testing machines for cylindrical specimens and flexural testing frames for beam specimens when the workflow continues into strength testing.
Practical equipment caution: ASTM C31/C31M influences molds, curing control, and specimen handling more directly than it dictates the final testing machine. Compression or flexural system selection depends on the later test method, specimen geometry, capacity, and reporting requirements named elsewhere in the project documents.
How to Read This Designation or Revision
ASTM C31/C31M is commonly cited with a slash format because the document includes SI and inch-pound units. The standard states that the two unit systems are to be used separately rather than combined.
The year that follows the designation identifies the adoption or latest revision year for that edition. If a letter suffix such as a or b appears after the year, it indicates an additional revision in the same calendar year.
Revision sensitivity: If a contract, DOT specification, or project manual cites a specific edition of ASTM C31/C31M, specimen preparation, curing practice, and documentation should match that cited edition.
Related Standards, Methods, or Frameworks
ASTM C31/C31M is commonly used alongside other concrete standards that cover sampling, later strength testing, ready-mixed concrete requirements, or laboratory-made specimens.
| Related standard | How it connects to ASTM C31/C31M |
|---|---|
| ASTM C172/C172M | Used for sampling freshly mixed concrete before field specimens are made. |
| ASTM C39/C39M | Common downstream test method for compressive strength of cylindrical concrete specimens prepared and cured under this practice. |
| ASTM C78/C78M | Common downstream test method for flexural strength of concrete beams prepared and cured under this practice. |
| ASTM C94/C94M | Ready-mixed concrete specification that commonly ties project acceptance strength work to standard-cured specimens. |
| ASTM C192/C192M | Laboratory counterpart used when specimens are made and cured under laboratory conditions instead of field conditions. |
| ASTM C1856/C1856M | Referenced when ultra-high-performance concrete requires a more specific specimen fabrication and testing practice. |
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If you are building an ASTM C31/C31M workflow around specimen molds, curing control, transport protection, or the downstream compression and flexural test path, Request a Quote.
