What does ASTM C138/C138M refer to?

ASTM C138/C138M is a standard test method established by ASTM International that specifically deals with the measurement of density (unit weight), yield, and air content of concrete using the gravimetric method. This test plays a crucial role in ensuring that concrete mixtures meet the desired specifications for weight and air entrainment, which can significantly impact the durability and strength of concrete structures.

Understanding the density of concrete allows engineers and construction professionals to assess the mix design and make any necessary adjustments to achieve the required strength and performance characteristics. Accurate measurement of unit weight also assists in the quality control of concrete production, ensuring that the concrete being used in construction projects is consistent and reliable.

The reference to "yield" in this context refers to the volume of concrete produced from a specific mix, while the air content measurement is integral in determining how much air is entrained in the mix, which contributes to the concrete's resistance to freezing and thawing cycles. These factors are essential for concrete that will be used in various environments and ensure its long-term performance.