What are the dimensions of an acrylic strike-off plate according to standard C138?

The correct answer indicates that the acrylic strike-off plate must be rectangular, measuring at least 1/2 inch thick, with the length or width being 2 inches or greater. This specification is outlined in ASTM C138, which provides guidelines for the measurement of the specific gravity and density of concrete. The dimensions of the plate are crucial because they influence how effectively it can level the surface of the concrete being tested. A thickness of 1/2 inch ensures durability while maintaining a manageable weight for handling. Additionally, the minimum dimensions of 2 inches or greater impact the effectiveness of obtaining a proper sample of the concrete mix, ensuring that the resulting strike-off is accurate and representative of the concrete’s consistency.

The other options do not align with the standard C138 specifications. A square plate of 1/4 inch thickness, for example, does not provide the required sturdiness and size to fulfill the test requirements effectively. Similarly, the parameters for thickness and dimensions in the remaining options either exceed the necessary specifications or do not meet them, rendering them unsuitable according to the guidelines set forth in the standard.