Building Engineering Construction Materials and Properties 3

Question 1

Per ASTM C90, what is the minimum net area compressive strength required for load-bearing concrete masonry units (CMU)?

Accepted Answer

1,900 psi

Answer

1,000 psi

Answer

2,500 psi

Answer

3,500 psi

Question 2

Carbonation of concrete is a durability concern primarily because it:

Accepted Answer

Reacts CO₂ with calcium hydroxide, reducing internal pH and depassivating reinforcement

Answer

Deposits carbon on the surface causing discoloration

Answer

Generates carbon monoxide gas that attacks aggregate bonds

Answer

Causes organic carbon compounds to leach from the cement paste

Question 3

Fiber-reinforced polymer (FRP) composites are increasingly used in building construction primarily because they offer:

Accepted Answer

High strength-to-weight ratio and inherent corrosion resistance

Answer

High thermal mass and excellent fire resistance

Answer

High ductility comparable to structural steel

Answer

Low cost and simpler fabrication than conventional materials

Question 4

Alkali-silica reaction (ASR) in concrete is caused by:

Accepted Answer

Alkalis in the cement pore solution reacting with reactive silica in certain aggregates

Answer

Excess mixing water creating a high w/c ratio

Answer

Freeze-thaw cycling expanding trapped moisture in paste pores

Answer

Sulfate ions from soil or groundwater attacking calcium aluminate phases

Question 5

Among common building insulation materials, which product provides the highest R-value per inch of thickness?

Accepted Answer

Closed-cell spray polyurethane foam (~R-6.5/in)

Answer

Fiberglass batt insulation (~R-3.5/in)

Answer

Cellulose insulation (~R-3.7/in)

Answer

Mineral wool (rock wool) insulation (~R-3.7/in)

Question 6

According to ASTM C270, what is the minimum compressive strength at 28 days for Type S mortar used in masonry construction?

Accepted Answer

1,800 psi

Answer

350 psi

Answer

750 psi

Answer

2,500 psi

Question 7

In masonry construction, 'efflorescence' refers to:

Accepted Answer

White crystalline salt deposits left on the surface as water migrates outward and evaporates

Answer

Spalling of brick faces caused by freeze-thaw expansion

Answer

Dark biological staining from algae or mold growth on the wall

Answer

Cracking in mortar joints from differential thermal expansion