ACI Certification Practice Exam

How quickly should strength samples be molded after fabricating the composite sample?

1. 10 minutes

2. 5 minutes

3. 15 minutes

4. 20 minutes

The correct answer is: 15 minutes

Strength samples should be molded as soon as possible after fabricating the composite sample to ensure accuracy and consistency in test results. The correct timeframe of 15 minutes is important because it helps to minimize the effects of environmental conditions on the material, such as temperature and humidity, which can influence the setting time and strength development. Waiting too long to mold the samples can lead to uneven curing and can alter the material's properties, resulting in inaccurate strength test data. Molding within this specified window ensures that the samples remain representative of the conditions intended for testing and that the chemical reactions occurring within the mix are consistent. The other time options are either too short, risking incomplete mixing and workability, or too long, potentially compromising the integrity of the strength samples. Therefore, molding strength samples within 15 minutes provides an optimal balance for achieving reliable and valid test results.