Chapter 8 - Cast-in-Place Concrete (REVIEW QUESTIONS)

How long can Ready-mix concrete remain in the mixer and still be used?

Before the drum has revolved 300 times after adding water

What devices are used on site to move concrete to the point of placement?

Conveyors, buggies, belt conveyors, wheel barrows, chutes, and concrete pumps

How is concrete consolidated?

- By pushing a rod into the concrete

- By mechanical vibration

What may happen if the temperature of concrete mix exceeds 100 degrees Fahrenheit (38 degrees celcius)?

It may flash set

Why are freshly poured concrete slabs bullfloated?

- To lower high spots

- To fill low spots

- To embed exposed aggregate into the mix

What is the difference between an isolation joint and a construction joint?

Construction joints separate the end of one pour from the next, Isolation joints separate the slab from a wall

Hydration is a chemical reaction between the cement and water which-

Produces heat and hardens the concrete

What are the curing methods in common use?

- Spray with curing compounds to retard moisture evaporation

- Sprinkle water over the surface of the concrete

- Cover the concrete with plastic or wet burlap

What is the purpose of form liners?

To produce patterned concrete

How is tensile strength of concrete beams increased?

By adding steel reinforcing bars

What two styles of reinforcing bars are used?

- Smooth

- Deformed

The diameter of a No. 8 bar is-

1 inch

What purpose do stirrups serve when installing reinforcing bars in a form?

To resist tension at the ends of the beam and transfer it to the concrete

How can you decide how many inches of concrete are needed to give fire protection to reinforcing bars?

Consult building code

What styles of wires are used to make welded wire reinforcement?

- Plain

- Deformed

What types of coatings are used on welded wire reinforcement?

- Epoxy coating

- Hot-dipped galvanized

Fibers that are used in the production of fiber reinforced concrete?

Glass fiber, polymeric, steel, wood, elephant grass

What is the difference between lightly reinforced and structurally reinforced concrete slabs?

- Lightly reinforced slabs depend on the earth for support

- Structurally reinforced slabs contain reinforcing bars or weld wire fabric

What is the purpose of using drop panels and capitals when casting flat concrete slabs?

To thicken and strengthen areas of the slab around a column

What is meant by tilt-up construction?

Casting a concrete wall on the ground and raising it to a vertical position after it has gained weight

What is unique about the forming technique?

The forms are raised as the concrete is poured