Chpt 10

Question 1

Because concrete is noncombustible, it is widely used in

Answer 1

Fire resistive construction

Question 2

In almost all structural applications concrete is reinforced with

Answer 2

Steel

Question 3

Is produced from Portland cement coarse and fine aggregates, and water

Answer 3

Concrete

Question 4

Concrete must be ____ in order to reach its proper strength

Answer 4

Cured

Question 5

Hardening or concrete involves a chemical process known as

Answer 5

Hydration

Question 6

In hydration , water combines with particles of cement to form a microscopic gel. As the concrete hardens, this gel gives off heat, which is known as the

Answer 6

Heat of hydration

Question 7

In addition to maintaining proper moisture, concrete that is curing must be maintained at the correct temperature, ideally between

Answer 7

50-70f

Question 8

Theoretically, properly cured concrete continues to harden indefinitely at a gradual rate, however, normal design strength is reached after

Answer 8

28 days

Question 9

Different types of concrete can be produced for specific purposes. This is accomplished by varying the ingredients or adding chemicals to the concrete mixture, these are generally known as

Answer 9

Admixtures

Question 10

Like masonry, concrete is strong in compression but weaker in

Answer 10

Tension

Question 11

Because concrete is weak in tension, it cannot be used where tensile forces occur in a structure. To resist tensile forces, concrete is reinforced with ______ placed within the concrete before it hardens

Answer 11

Steel reinforcing bars

Question 12

With_____, steel bars are placed in the formwork and the wet concrete is placed in the formwork around the bars

Answer 12

Ordinary reinforcing

Question 13

The vertical reinforcing of bars are known as _____ and are provided to resist the diagonal tension

Answer 13

Stir ups

Question 14

Although the primary function of placing reinforcing steel concrete is to resist tensile forces, the steel can also be used to support some of the

Answer 14

Compressive forces

Question 15

In ____ a compressive load is induced in the concrete before the load is applied

Answer 15

Prestressing

Question 16

In_____ concrete, steel strands are stretched between anchors producing a tensile force in the steel

Answer 16

Pretensioned concrete

Question 17

When concrete is ______, the reinforcing steel is not tensioned until after the concrete has hardened

Answer 17

Posttensioned

Question 18

As a general rule, reinforcing steel should not be cut in the course of fire fighting operations unless it is necessary to

Answer 18

Rescue trapped victims

Question 19

Concrete can be either

Answer 19

Cast in place or precast

Question 20

Is placed into forms at the building site as a wet mass and hardens in forms

Answer 20

Cast in place concrete

Question 21

Is placed in forms and cured at a precasting plant away from the job site.

Answer 21

Precast concrete

Question 22

Permits the designer to cast the concrete in a wide variety of shapes

Answer 22

Cast in place concrete

Question 23

This type of concrete does not develop its designed strength until after it has been placed in the location where it will be used

Answer 23

Cast in place concrete

Question 24

Most ____ is proportioned at central bulk plants and then mixed in a mixing truck enroute to the job site

Answer 24

Cast in place concrete

Question 25

The quality of concrete is of significance to firefighters. Concrete that is of poor structural quality will behave poorly under fire conditions by

Answer 25

Spalling and even breaking apart

Question 26

The single most important factor in determining the ultimate strength of concrete is the

Answer 26

Water to cement ratio

Question 27

If too much water has been used in the mix, the final product will not achieve its desired strength. The presence of excess moisture in the concrete also produces _____ in the concrete due to freezing conditions or the heat of fire

Answer 27

Spalling

Question 28

When the concrete arrives at the job site, it’s quality is checked by administering a test known as a

Answer 28

Slump test

Question 29

Another method of testing concrete is to make small test cylinders of a concrete batch and subject them to

Answer 29

Compression testing

Question 30

The following are common cast in place structural systems

Answer 30

Flat slab Slab and beam Waffle construction

Question 31

The _____ is a simple system that consists of a concrete slab supported by concrete columns.

Answer 31

Flat slab concrete frame

Question 32

The slab of concrete varies in thickness from 6 to 12 inches

Answer 32

Flat slab concrete frame

Question 33

In a building that will have heavy live loads, the area around the columns is reinforced with additional concrete in the form of

Answer 33

Drop panels or mushroom capitals

Question 34

If the building will support light loads, this additional reinforcing is not necessary. The system then is known as a

Answer 34

Flat plate

Question 35

A _____ consists of a concrete slab supported by concrete beams

Answer 35

Slab and beam frame

Question 36

This framing system is extremely light weight and is best suited for buildings with light floor loads

Answer 36

Slab and beam frame

Question 37

Slabs in this type of construction can sometimes be as thin as 2 inches

Answer 37

Slab and beam

Question 38

Due to the thin slab, the concrete beams must be closely spaced in order to provide adequate support. This spacing often gives an appearance similar to wood joists and is sometimes referred to as

Answer 38

Concrete joist construction

Question 39

When the concrete beams run mainly in one direction, the framing is known as a

Answer 39

One way reinforced slab

Question 40

Slab and beam concrete framing can also feature concrete beams running in two directions. Such a system is known as a

Answer 40

Two way slab construction

Question 41

The pattern results from the placement of square forms over which the wet concrete is placed.

Answer 41

Waffle construction

Question 42

derives it’s name from the waffle like pattern of the bottom of the concrete slab

Answer 42

Waffle construction

Question 43

May be produced at a precasting plant some distance from the work site

Answer 43

Precast concrete

Question 44

A major disadvantage to using _____ is the need to transport the finished components to the job site

Answer 44

Precast concrete

Question 45

Can be built using whole precast modular units but it is more common to assemble precast parts into a framework for a building

Answer 45

Precast concrete buildings

Question 46

Precast concrete structures have more in common with steel framed buildings than with

Answer 46

Cast in place concrete buildings

Question 47

A common form of construction used with precast concrete is known as

Answer 47

Tilt up construction

Question 48

When precast beams are to be supported by columns, the beams may be supported by ____ cast into the column.

Answer 48

Corbels

Question 49

A____, also known as a bracket, is a ledge that projects from the column and supports the beam.

Answer 49

Corbel

Question 50

Concrete is a fundamentally _____ that performs well under fire conditions

Answer 50

Fire resistive material

Question 51

Prestressed concrete systems may be somewhat more vulnerable to ____ than ordinary reinforced construction

Answer 51

Failure

Question 52

The fire resistance of concrete assembly is affected by such variables as the following

Answer 52

``` Concrete density Concrete thickness Concrete quality Load supported by the concrete Depth of concrete cover over the reinforcing bars ```

Question 53

Cast in place concrete buildings have an advantage over precast buildings because the continuity of the assembly provides an inherent restraint to movement of the intersecting members such as columns and beams

Answer 53

This results in a fundamentally greater structural rigidity of cast in place buildings

Question 54

When openings exist in concrete slabs or walls, the ability of the concrete to act as a barrier is lost unless the opening is protected by an appropriately rated assembly such as a

Answer 54

Fire door or shutter

Question 55

Of concrete is caused primarily by the expansion of the excess moisture within the concrete when it is either heated or when it freezes

Answer 55

Spalling

Question 56

Newer concrete that is not completely cured is subject to more severe ____ when exposed to fire

Answer 56

Spalling

Question 57

Because concrete has a relatively good insulating properties, it tends to retain the heat of an expose the fire and release it slowly, similar to the manner in which a masonry oven releases heat. This general effect is referred to as the

Answer 57

Heat sink effect

Question 58

Concrete is a noncombustible building material that is strong in compression but weak in

Answer 58

Tension

Question 59

Have greater inherent rigidity than precast structures

Answer 59

Cast in place