ACI Fresh Concrete Field Testing Questions and Answers

Question 1

An ACI Certified Field Testing Technician is performing a slump test (ASTM C143) on a sample of fresh concrete. The concrete slumps and falls away to one side. What is the correct action for the technician to take?

Accepted Answer

Disregard the test and immediately perform a retest on another portion of the same sample.

Answer

According to ASTM C143/C143M, if the concrete shears off or slips sideways, the test is considered invalid. The technician must disregard the result and conduct a new test on a different portion of the composite sample. If a similar result occurs on the retest, the concrete is likely not cohesive enough for the slump test to be applicable, and this should be noted in the report.

Question 2

According to ASTM C172, Standard Practice for Sampling Freshly Mixed Concrete, what is the maximum allowable elapsed time between obtaining the first and final portions of a composite sample?

Accepted Answer

15 minutes

Answer

ASTM C172 specifies that the process of collecting a composite sample, which involves taking portions from the middle part of the batch, must be completed within a 15-minute timeframe from the start of sampling.

Question 3

A technician is measuring the density (unit weight) of freshly mixed concrete following ASTM C138. After filling the measure and striking off the excess concrete, what is the immediate next step?

Accepted Answer

Clean all excess concrete from the exterior of the measure.

Answer

The ASTM C138 procedure requires that after striking off the top surface, the technician must clean any excess concrete from the outside of the measure. This ensures an accurate weight measurement of only the measure and the concrete inside it.

Question 4

When measuring the temperature of freshly mixed hydraulic-cement concrete (ASTM C1064), how much concrete cover should surround the sensing portion of the temperature measuring device?

Accepted Answer

At least 3 inches (75 mm) in all directions.

Answer

ASTM C1064/C1064M requires the temperature sensing portion of the thermometer to be submerged a minimum of 3 inches (75 mm) into the fresh concrete. Additionally, there must be at least 3 inches (75 mm) of concrete cover in all directions around the sensing portion to ensure the reading reflects the internal temperature of the concrete and is not influenced by ambient air temperature.

Question 5

Which of the following is the correct tamping procedure for filling a 0.5 ft³ unit weight measure when performing the test for Density (Unit Weight) of Concrete (ASTM C138)?

Accepted Answer

Fill in 3 equal layers, rodding each layer 50 times.

Answer

For a measure with a volume of 0.5 ft³, ASTM C138 requires the concrete to be placed in three approximately equal layers. Each layer must be rodded 50 times with the tamping rod, distributing the strokes evenly over the cross-section.

ACI (American Concrete Institute Certification) Practice Test

ACI (American Concrete Institute Certification) Practice Test

ACI Fresh Concrete Field Testing Questions and Answers