CTQP Concrete Field Inspector 5 — Questions and Answers
Question 1: When measuring the slump of a concrete sample, where is the measurement taken?
- From the base of the cone to the highest point of the slumped concrete
- From the top of the inverted cone to the displaced original center
- From the original center of the top of the concrete to the displaced center (Correct answer)
- From the base of the slumped concrete to its highest remaining point
Correct answer: From the original center of the top of the concrete to the displaced center
The slump is measured as the vertical distance between the original center of the top of the concrete and the displaced center after the cone is removed.
Question 2: Which supplementary cementitious material (SCM) is a byproduct of burning coal in electric power plants?
- Silica fume
- Ground granulated blast-furnace slag (GGBFS)
- Fly ash (Correct answer)
- Natural pozzolan
Correct answer: Fly ash
Fly ash is a byproduct collected from the flue gases of coal-burning power plants and is commonly used as an SCM in concrete.
Question 3: What is the maximum time allowed between obtaining the composite sample and completing the slump test per ASTM C172?
- 3 minutes
- 5 minutes (Correct answer)
- 7 minutes
- 10 minutes
Correct answer: 5 minutes
ASTM C172 requires that testing begin within 5 minutes of obtaining the composite sample to ensure representative results.
Question 4: Which type of curing method is generally considered most effective for concrete flatwork?
- Curing compounds applied after finishing
- Burlap kept continuously wet with water (Correct answer)
- Plastic sheeting laid over the surface
- Fogging systems applied from above
Correct answer: Burlap kept continuously wet with water
Wet burlap (or similar wet coverings) maintained continuously moist is widely regarded as the most effective method because it provides constant moisture without allowing drying cycles.
Question 5: A concrete inspector notices the truck drum is revolving at agitating speed rather than mixing speed on arrival. What is the implication?
- The concrete will be over-mixed and weaker
- The concrete has not been fully mixed and may be non-uniform
- There is no issue since agitating maintains mix quality indefinitely (Correct answer)
- Air content will increase from the slower drum rotation
Correct answer: There is no issue since agitating maintains mix quality indefinitely
Agitating speed is for maintaining a mixed load in transit, not for initial mixing — if mixing was incomplete, the load may be non-uniform.
Question 6: When fabricating concrete test cylinders, how soon must they be transported to the lab after initial curing per ASTM C31?
- Within 6 hours of casting
- Within 12 hours of casting
- Between 16 and 32 hours after casting (Correct answer)
- Between 24 and 48 hours after casting
Correct answer: Between 16 and 32 hours after casting
ASTM C31 requires cylinders to be transported to the laboratory between 16 and 32 hours after casting for standard curing.
Question 7: What is the minimum number of test cylinders that should be cast per ASTM C31 for a standard compressive strength test set at 28 days?
- 1
- 2 (Correct answer)
- 3
- 4
Correct answer: 2
A strength test result is the average of at least two cylinders made from the same composite sample and tested at the same age.
CTQP Concrete Field Inspector 5
When measuring the slump of a concrete sample, where is the measurement taken?