ACI Concrete Strength Testing Technician Practice Test

What is the purpose of ASTM C39 testing method?

1. To measure flexural strength of concrete

2. To assess the freeze-thaw resistance of concrete

3. To determine compressive strength of concrete

4. To evaluate workability

The correct answer is: To determine compressive strength of concrete

The ASTM C39 testing method is specifically designed to determine the compressive strength of concrete. This method involves preparing concrete cylinder specimens, which are then subjected to axial loading until failure. The load at which the concrete crushes is measured, and this value is used to calculate the compressive strength in pounds per square inch (psi) or megapascals (MPa). The compressive strength of concrete is a critical property that reflects how well the material can withstand axial loads, which are common in structural applications. This testing is essential for ensuring that the concrete mix meets the specified strength requirements for design and structural performance. While the other options address different properties or characteristics of concrete, they are not evaluated through the ASTM C39 method. Instead, methods like ASTM C78 are used for flexural strength testing, ASTM C666 assesses freeze-thaw resistance, and testing for workability is usually determined through methods like the slump test. The focus of ASTM C39 remains squarely on compressive strength, which makes the choice entirely appropriate.