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

ASTM C90 specifies a minimum average net area compressive strength of 1,900 psi for load-bearing CMU used in structural masonry walls.

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

Carbonation lowers the concrete's pH from ~12.5 to below 9, destroying the alkaline passive film that protects embedded rebar from corrosion.

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

FRP composites combine high tensile strength with very low weight and do not corrode, making them valuable in corrosive environments and for strengthening existing structures.

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

ASR is a chemical reaction between alkali hydroxides (from cement) and amorphous or cryptocrystalline silica in reactive aggregates, producing an expansive gel.

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

Closed-cell SPF achieves approximately R-6 to R-7 per inch because its closed cells trap a low-conductivity blowing agent and the rigid foam resists convective heat transfer.

Building Engineering Practice Test

Building Engineering Practice Test

Building Engineering Construction Materials and Properties 3