ASTM C457
Full Name
ASTM C457 – Standard Test Method for Microscopical Determination of Parameters of the Air-Void System in Hardened Concrete
Scope
ASTM C457 is a standard test method used to determine the parameters of the air-void system in hardened concrete through microscopic examination. The key parameters measured include:
- Air content: the total volume of air voids in the concrete.
- Specific surface: the surface area of air voids per unit volume of air.
- Void frequency: the number of air voids intercepted by a traverse line
divided by the length of that line. - Spacing factor: the average distance between air voids.
- Paste-air ratio: the ratio of the volume of paste to the volume of air.
Three procedures are described:
- Procedure A – linear-traverse method: involves moving a microscope along a line across a polished concrete surface and counting the air voids intersected.
- Procedure B – modified point-count method: involves counting the number of points that fall on air voids within a grid superimposed on a polished concrete surface.
- Procedure C – contrast enhanced method: the volumetric composition of concrete is determined by summing distances measured in digital images of a prepared concrete surface.
The data obtained from this test method is crucial for assessing the durability and freeze-thaw resistance of concrete. It helps determine if the air-void system is adequate to protect the concrete from damage caused by freezing and thawing cycles.
ASTM C457 Accredited Laboratory
Applied Testing & Geosciences, LLC is accredited for performing tests using the ASTM C457 standard.
Contact us for more information.
Resources
Keywords
air voids; hardened concrete; microscopic examination; air content; specific surface; void frequency; spacing factor; paste-air ratio; linear traverse method; modified point-count method; freeze-thaw resistance; durability; polished concrete surface