Chapter 10

Question 1

Aggregates make up

Answer 1

A large percentage of the total volume of concrete

Question 2

3 types of admixtures and their purposes

Answer 2

Shale or clinker- reduce the density of the concrete

Superplasticizer- produce a mixture that flows more freely

Coloring- Added for aesthetic or after reasons

Question 3

4 Primary advantages of concrete

Answer 3

Produced from locally available and low cost raw materials

Fundamentally non combustible

Performs well under mild to moderate fire conditions

Good insulating properties

Question 4

concrete has good compression strength however has poor ______ strength and is reinforced when that stress is applied

Answer 4

Tensile

Question 5

Reinforced concrete unltimate compressive strength can range from

Answer 5

2,500 to 6,000 PSI

Question 6

Ordinary reinforcing uses

Answer 6

Steel bars placed in the formwork then wet concrete placed in the formwork around the bars

Question 7

Most commonly used size rebar

Answer 7

5 -0.625 inches

Question 8

vertical reinforcing bars are know as _______ and are provided to resit the diagonal tension

Question 9

Prestressing technique is

Answer 9

Preloads the reinforcing steel adding compressive stress to the surrounding concrete

Question 10

Two Common methods of prestressing are

Answer 10

Pretensioning

Posttensioning

Question 11

Pretensions reinforcement uses

Answer 11

Steel strands stretched between anchors producing a tensile force the the steel, concrete is then placed around the steel strands and allowed to harden. Once harden the strands are released causing a compression force

Question 12

Postentensioning reinforcement uses

Answer 12

Steel cables that are not tensioned untill after the concrete has hardened.

Question 13

cutting through reinforcing steel with saw or torch is particular dangerous in posttension concrete because

Answer 13

the steel is not bonded to the concrete the stell strands are stretcher like giant rubber bands

Question 14

The systems use reinforcing cables and rods can yield temperatures as low as

Answer 14

752 F

Question 15

Concretes normal design strength is reached

Answer 15

After 28 days

Question 16

the single most important factor in determining the ultimate strength of concretes is

Answer 16

Water to cement ration

Question 17

Hardening of concrete involves a chemical process is know as

Answer 17

Hydration

Question 18

during the hardening of concrete heat is given off by the chemical process

Answer 18

Heat of hydration

Question 19

The Process of curing must be maintained at the correct temperature

Answer 19

Ideally between 50 and 70F

Question 20

Slump test

Answer 20

Uses a standard sized cone shape mold and a sample of wet concrete to check the moisture content of a batch

Question 21

separate test that uses small test cylinders of a concrete batch to determine the compression strength of that batch is know as

Answer 21

Compression testing

Question 22

Concrete structural systems can have fire resistance ratings from

Answer 22

1 to 4 hours

Question 23

the fire resistance of a concrete assembly is affect by 5 Variables which are

Answer 23

concrete density

concrete thickness

concrete quality

supported load

depth of concrete cover over the reinforcing bars

Question 24

Slab concrete ranges in thickness from

Answer 24

6 to 12 inches

Question 25

the area around the columns is reinforced with additional concrete in the form of what two things

Answer 25

Drop Panels or mushroom capitals

Question 26

Two way slab construction AKA waffle construction is

Answer 26

Slab and beam concret framing featuring concrete beams running in tow directions

Question 27

3 Advantages to using precast concrete include

Answer 27

Higher degree of quality control possible than with cast in place concrete

Work can proceed more quickly at the job site

Precast concrete sandwich panels can produced using a polystyrene core to improve the insulating properties of the precast concrete

Question 28

major disadvantage to using precast concrete is

Answer 28

the need to transport the finished components to the job site

Question 29

Precast concrete slabs can be cast in standard shape (4)

Answer 29

Slabs

Hollow Core Slabs

Singe Tee

Double Tee

Question 30

Solid slabs are used for short spans of

Answer 30

30 feet

Question 31

Failure of the roof in a tilt up construction can result in

Answer 31

failure of the wall from outward horizontal forces