ACI Certification Practice Exam

What is the maximum allowable time before beginning tests for slump, temperature, and air content after obtaining the final portion of the composite sample?

1. 10 minutes

2. 15 minutes

3. 5 minutes

4. 30 minutes

The correct answer is: 5 minutes

The maximum allowable time before beginning tests for slump, temperature, and air content after obtaining the final portion of the composite sample is 5 minutes. This time limit is crucial because the properties of freshly mixed concrete, such as workability indicated by slump, temperature, and air content, can change rapidly. Delays beyond this period can lead to inaccuracies in test results, as the concrete may begin to set or change due to initial hydration processes, temperature effects, or evaporation. By adhering to the 5-minute time frame, technicians ensure that the tests accurately reflect the condition of the concrete at the time the sample was taken. This is vital for quality control in concrete construction, as understanding the material's properties at the time of testing helps in assessing its performance and suitability for the intended application.