ACI Concrete Field Testing Technician - Grade I 2025 – 400 Free Practice Questions to Pass the Exam

In the air meter test method, isopropyl alcohol at a concentration of 70% by volume is utilized primarily for its effectiveness in reducing the surface tension of the water. This characteristic aids in ensuring that entrained air bubbles can be accurately measured, which is critical for assessing the air content in concrete.

Using isopropyl alcohol at this specific concentration allows the test to achieve results that are reliable and reproducible, which is crucial in quality control and adherence to mix design specifications in concrete production. The choice of isopropyl alcohol over other types ensures a lower risk of volatile organic compound (VOC) emissions compared to methyl alcohol, while still being effective in performing the air meter test.

The other options involve different types of alcohol or concentrations that do not meet the testing standards. For example, variations in concentration either too low or too high can affect the accuracy of the results, leading to misinterpretation of the air content in the concrete mix. Thus, the specified use of 70% isopropyl alcohol by volume is significant for maintaining consistency and precision in air content measurement.