ACI Curing, Protection & Quality Control 3

Question 1

Which chemical admixture is commonly used in hot weather concreting to offset the accelerating effect of high temperatures?

Accepted Answer

Set retarder

Answer

Set retarders slow hydration, compensating for the accelerated set caused by elevated concrete temperatures in hot weather.

Question 2

The water-to-cementitious-materials ratio (w/cm) primarily affects which property of hardened concrete?

Accepted Answer

Compressive strength and durability

Answer

The w/cm ratio is the single most important factor controlling concrete compressive strength and long-term durability.

Question 3

During cold weather concreting, the concrete temperature at the point of placement should be maintained at a minimum of:

Accepted Answer

50°F (10°C)

Answer

ACI 306 requires concrete to be placed and maintained at a minimum of 50°F (10°C) to ensure adequate hydration in cold weather.

Question 4

What is the primary purpose of fogging or misting water over fresh concrete in hot, dry, or windy conditions?

Accepted Answer

To reduce plastic shrinkage cracking by slowing evaporation

Answer

Fogging raises humidity immediately above the slab surface, reducing evaporation rate and thus preventing plastic shrinkage cracking.

Question 5

A cylinder break at 28 days shows strength below the specified f'c. What is the first step in ACI-compliant quality control response?

Accepted Answer

Conduct additional testing such as cores per ACI 318

Answer

ACI 318 requires taking cores from the suspect area as the next investigative step before any remedial action is decided.

(ACI) American Concrete Institute Concrete Finisher Practice Test