ACI Certification Concrete Mix Design

Question 1

According to ACI 211.1, which factor most directly influences the required water content for a given slump?

Accepted Answer

Maximum size of aggregate

Answer

Cement type

Answer

Admixture brand

Answer

Color of aggregate

Question 2

In the absolute volume method of mix design, the sum of volumes of all ingredients for one cubic yard of concrete must equal:

Accepted Answer

27 cubic feet

Answer

25 cubic feet

Answer

26 cubic feet

Answer

28 cubic feet

Question 3

What is the approximate specific gravity of Type I portland cement used in absolute volume calculations?

Accepted Answer

3.15

Answer

2.45

Answer

2.65

Answer

3.50

Question 4

A lower water-to-cement (w/c) ratio generally produces concrete with:

Accepted Answer

Higher strength and improved durability

Answer

Greater slump and lower strength

Answer

Higher water content and greater bleeding

Answer

Reduced cement paste volume

Question 5

According to ACI 318, the maximum w/cm ratio for concrete exposed to freezing and thawing in a moist condition is:

Accepted Answer

0.45

Answer

0.40

Answer

0.55

Answer

0.60

Question 6

The target mean compressive strength (f'cr) is set higher than the specified strength (f'c) to account for:

Accepted Answer

Normal variability in concrete production and testing

Answer

Aggregate variability only

Answer

Seasonal temperature changes

Answer

Equipment calibration errors

Question 7

Supplementary cementitious materials (SCMs) such as fly ash are used in concrete mix design primarily to:

Accepted Answer

Replace a portion of portland cement while maintaining or improving properties

Answer

Increase the water demand of the mix

Answer

Eliminate the need for coarse aggregate

Answer

Increase the unit weight of concrete