PE Civil (NCEES Principles and Practice of Engineering) — All Questions

For a massive concrete pour where controlling the heat of hydration is critical, which cement type is appropriate?

• a.Type III
• b.Type I
• c.Type II
• d.Type IV✓

Type IV cement generates a low heat of hydration, reducing the temperature rise and thermal cracking risk in mass concrete such as large dams and heavy foundations.

Adding fly ash (a pozzolan) to a concrete mix generally:

• a.improves workability and long-term strength while lowering heat✓
• b.reduces long-term strength
• c.raises the water-cement ratio
• d.sharply increases the early heat of hydration and the peak concrete temperature

Fly ash reacts with lime from cement hydration to form additional binder, improving workability, reducing permeability, lowering heat of hydration, and enhancing long-term strength and durability.

A higher slump reading for a given concrete mix indicates:

• a.more entrained air
• b.higher compressive strength
• c.a drier, stiffer mix
• d.a wetter, more workable (fluid) mix✓

A larger slump means the concrete is more fluid and workable, usually from a higher water content or plasticizer. A high slump does not mean higher strength; excess water actually reduces strength.

For concrete, the initial set and final set differ in that:

• a.initial set marks loss of workability; final set marks the start of appreciable strength gain✓
• b.final set comes before initial set
• c.neither affects placement
• d.they occur at the same instant

Initial set is when concrete stiffens and can no longer be properly placed or vibrated; final set marks the transition to a rigid solid beginning to develop strength. Both are measured by penetration resistance.

For structural timber below the fiber saturation point, how does increasing moisture content affect strength?

• a.strength decreases as moisture content rises✓
• b.the strength steadily increases as the moisture content of the wood rises
• c.wood carries no load when moist
• d.moisture has no effect on strength

Below the fiber saturation point, wood strength and stiffness decrease as moisture content increases; design values include moisture (wet-service) adjustment factors to account for this.

The California Bearing Ratio (CBR) test is used chiefly to evaluate:

• a.asphalt binder grade
• b.steel toughness
• c.concrete compressive strength
• d.the strength of subgrade and base materials for pavement design✓

The CBR compares a soil's penetration resistance to that of a standard crushed stone, giving an index of subgrade/base strength used in flexible pavement thickness design.

A soil has a liquid limit of 40 and a plastic limit of 20. What is its plasticity index?

• a.20✓
• b.2
• c.0.5
• d.60

Plasticity index = liquid limit - plastic limit = 40 - 20 = 20. The PI is the range of water content over which the soil behaves plastically and is used to classify fine-grained soils.