Free ACI Strength Testing Technician Questions and Answers

Question 1

Following the thermometer's insertion into the concrete:

Accepted Answer

All of the above

Answer

After inserting the thermometer into the concrete, it is important to gently press the concrete around it to ensure good thermal contact for an accurate reading. Tapping the side of the container 10-15 times helps settle the concrete and remove any air pockets around the probe, further improving contact. While cooling the surface with water is not explicitly stated in all standards for temperature measurement, it can be a practice in some field conditions to minimize rapid surface temperature fluctuations or evaporation, contributing to a more stable and representative reading of the bulk concrete temperature.

Question 2

What is one reason, under ASTM C1064, to take a concrete's temperature?

Accepted Answer

Verify ambient air temperature

Answer

Under ASTM C1064, one reason to take a concrete's temperature is to verify the ambient air temperature. While the primary purpose is to measure concrete temperature, recording ambient conditions is crucial for understanding the curing environment and potential influences on concrete properties. This data helps in assessing compliance with project specifications related to placement temperatures and environmental factors.

Question 3

Begin testing for slump and air content within after sampling is finished.

Accepted Answer

2 ½ minutes

Answer

To ensure that slump and air content tests are performed on concrete that is still representative of its fresh state, testing must begin within 2 ½ minutes after the sampling is finished. This strict time limit minimizes the effects of hydration and stiffening, which can rapidly alter the concrete's workability and air content. Adhering to this timeframe is critical for obtaining accurate and reliable test results.

Question 4

In any event, wait to get samples until:

Accepted Answer

All the water and admixtures have been added to the concrete

Answer

To obtain a truly representative sample of concrete, it is crucial to wait until all the water and admixtures have been fully added and thoroughly mixed into the concrete. Sampling before all ingredients are incorporated would result in a non-uniform mixture. This ensures that the sample accurately reflects the final properties of the concrete being delivered or placed.

Question 5

Samples cannot be taken before the batch has been released (_________) or after (_________).

Accepted Answer

20% or after 80%

Answer

According to ASTM C172, samples of concrete should be taken from the middle portion of the batch discharge. This means samples cannot be taken before 20% of the batch has been released or after 80% of the batch has been discharged. This practice ensures that the collected sample is representative of the overall concrete mixture, avoiding potential variations found at the very beginning or end of the discharge.

ACI (American Concrete Institute Certification) Practice Test

ACI (American Concrete Institute Certification) Practice Test

Free ACI Strength Testing Technician Questions and Answers