ASTM C99/C99M is a standard test method used to determine the modulus of rupture (flexural strength in bending) of dimension stone. It is commonly used to compare the bending performance of stone types and to support material qualification for architectural and building stone applications.
This method applies to dimension stone types other than slate and is typically performed as a controlled bend test on prepared stone specimens using a lab load frame and a flexural fixture. If you need help aligning specimen size, fixture geometry, and reporting expectations to the exact edition cited in your project documents, talk with our team.
ASTM C99/C99M-18 Standard Test Method for Modulus of Rupture of Dimension Stone
ASTM C99/C99M is a laboratory flexural-strength test method for dimension stone. It is widely referenced for stone selection, quality control, and documentation when stone is being considered for cladding, flooring, paving, treads, panels, and other applications where bending resistance is a key performance input.
The standard is written in dual units (SI and inch-pound) and is commonly cited by designation plus an edition year.
Quick Definition
| Item | What ASTM C99/C99M Covers |
|---|---|
| Document type | Standard test method |
| Primary property | Modulus of rupture (flexural strength in bending) |
| Material scope | Dimension stone (all types except slate) |
| Typical test style | Bend test using a flexural fixture and load-measuring frame |
What This Standard Covers
ASTM C99/C99M covers determining the modulus of rupture of dimension stone (excluding slate). In practice, this means preparing stone specimens to the required geometry and testing them in bending to obtain a flexural strength value.
The method is intended to be useful for distinguishing performance differences among stone materials and for comparing stones within the same general type.
Why This Standard Matters in Testing
Modulus of rupture is often used as a screening and documentation value for stone used in construction. Buyers and specifiers use it to support material selection, compare sources, and establish baseline mechanical performance for dimension stone intended for service conditions where bending can occur (for example during handling, fabrication, installation, or in-service loading).
Because natural stone can vary by quarry, lot, orientation, and fabrication approach, consistent standards-based testing helps QA/QC teams track variability and communicate performance in a comparable format.
Common Materials, Product Types, or Applications Covered
ASTM C99/C99M is used with natural dimension stone products supplied as blocks, slabs, tiles, or fabricated units (with specimens prepared from the supplied material). It is most often associated with architectural and building stone used in:
- Exterior and interior cladding
- Flooring and paving
- Stair treads and landings
- Stone panels and elements that may see bending during handling or installation
For terminology and material descriptions used across dimension-stone work, ASTM C119 is commonly referenced alongside test methods in this area.
Common Test or Verification Workflow
Most labs run ASTM C99/C99M in a straightforward, repeatable workflow centered on bend testing prepared stone specimens.
Common workflow: Confirm the cited edition and unit system (SI or inch-pound), prepare specimens from the submitted stone, verify specimen geometry and placement marks as required, condition specimens as required by the job (for example, dry or wet), run the bend test on the required fixture, and report modulus of rupture with the required supporting measurements and test condition notes.
Practical caution: Results can be sensitive to specimen preparation quality (flatness/parallelism), stone orientation/veining, and whether testing is performed in a wet versus dry condition. These details can affect both repeatability and how results compare across suppliers.
Equipment Commonly Used for This Standard
ASTM C99/C99M is typically performed on a load frame (or universal testing machine) equipped for flexural/bend testing of stone specimens, with appropriate supports and a loading nose to apply force in bending.
Common equipment: Universal testing machine or compression-capable load frame with calibrated force measurement, a flexural fixture sized for the required specimen and span, support/loading blocks (often hardened), and basic dimensional measurement tools for specimen measurements used in calculations.
If you are selecting a frame capacity, fixture size, and control package for stone flexural testing, you can request a detailed quote based on your specimen geometry, expected strength range, and throughput needs.
How to Read This Designation or Revision
C99 vs. C99/C99M: The “/C99M” form indicates the document is written for use in either SI units or inch-pound units, with each unit system intended to be used independently.
Edition suffix (year): When specified as C99/C99M followed by a hyphen and year (for example, “-18”), the suffix identifies the edition referenced in a contract, specification, or report. Test setup details and reporting expectations can be edition-sensitive, so matching the cited edition is important.
Related Standards, Methods, or Frameworks when useful
Dimension stone testing programs commonly pair modulus of rupture with other physical property tests for a fuller material profile.
Often used alongside: ASTM C97/C97M (absorption and bulk specific gravity of dimension stone) and ASTM C119 (terminology relating to dimension stone).
Get help matching ASTM C99/C99M to your lab setup
If you need assistance choosing a flexural fixture configuration, verifying what your purchase specification requires, or aligning your equipment and calibration approach to the exact C99/C99M edition being cited, contact our team and share your stone type, specimen size, and throughput goals.