Answer :
Final answer:
The ASTM standard required for obtaining a sample of concrete used in molding test specimens is ASTM C31. This standard is essential for quality control and to ensure the accurate representation of the material's properties in construction projects.
Explanation:
The question asks about the ASTM standard that should be followed when obtaining a sample of concrete used in molding test specimens. The correct answer is ASTM C31. ASTM C31 is a standard practice for making and curing concrete test specimens in the field. It outlines detailed procedures for sampling fresh concrete, making molds, curing specimens, and measures to control and verify the standard consistency of the methods used.
This standard ensures that the test samples accurately represent the concrete material's properties used in a construction project, making it vital for quality control and compliance with design specifications.
Other mentioned ASTM standards, such as ASTM C192, ASTM C143, and ASTM C39, cater to different aspects of concrete testing and properties but are not directly related to the sampling process.
It's important for students and professionals in civil engineering and construction to be familiar with these standards for quality control and ensuring that materials meet the necessary specifications.