ACI Concrete Materials & Mix Proportioning

Question 1

What is the primary binder in concrete?

Accepted Answer

Portland cement

Answer

Sand

Answer

Gravel

Answer

Fly ash

Question 2

Which component affects concrete workability the most?

Accepted Answer

Water content

Answer

Aggregate size

Answer

Cement type

Answer

Air content

Question 3

What does the water-cement ratio determine?

Accepted Answer

Compressive strength

Answer

Color

Answer

Setting speed

Answer

Surface finish

Question 4

Which material is commonly used as a supplementary cementitious material?

Accepted Answer

Fly ash

Answer

Silica sand

Answer

Limestone

Answer

Iron oxide

Question 5

Why is aggregate gradation important in concrete mix design?

Accepted Answer

To minimize voids and improve strength

Answer

To reduce color variation

Answer

To enhance texture

Answer

To change hydration

Question 6

What is the effect of excessive water in a concrete mix?

Accepted Answer

Reduces strength

Answer

Improves curing

Answer

Increases durability

Answer

Eliminates air bubbles

Question 7

What is air entrainment in concrete?

Accepted Answer

Deliberate addition of air bubbles

Answer

Removal of water

Answer

Air leakage from forms

Answer

Gas emission from aggregates

Question 8

Which test measures concrete consistency?

Accepted Answer

Slump test

Answer

Core test

Answer

Compression test

Answer

Rebound hammer test

Question 9

Why are admixtures used in concrete?

Accepted Answer

To enhance concrete performance

Answer

To add color

Answer

To reinforce with steel

Answer

To increase porosity