ACI Concrete Field Testing Technician - Grade I Practice Exam

What is the standard size of concrete cylinders used for strength testing?

1. 4 inches by 8 inches

2. 6 inches by 12 inches

3. 3 inches by 6 inches

4. 5 inches by 10 inches

The correct answer is: 6 inches by 12 inches

The standard size used for concrete strength testing is 6 inches by 12 inches. This dimension is widely accepted and referred to in ASTM (American Society for Testing and Materials) standards as the typical mold size for casting concrete cylinders that are intended for compressive strength testing. The larger diameter and height of this cylinder provide a practical balance between achieving manageable handling and producing a representative sample that accurately reflects the properties of the concrete mixture used. This sizing is designed to ensure consistency in testing and to accommodate the various types of concrete mixes, allowing for reliable comparisons of strength results across different tests. The choice to use 6 inches by 12 inches molds helps mitigate variability that might arise from using smaller or non-standard samples.