Chapter 1 : Introduction

Question 1

A mixture of cement and water.

Answer 1

Cement paste

Question 2

A mixture of sand, gravel, crushed rock, or other aggregates held together in a rocklike mass with a paste of cement and water.

Answer 2

Concrete

Question 3

Sometimes one or more admixtures are added to change certain characteristics of the concrete sch as?

Answer 3

Workability,
Durability
Time of Hardening

Question 4

This is a strutural concrete without reinforcement or with les than the minimum amount required by ACI 318 for reinforced concrete.

Answer 4

Plain Concrete

Question 5

This is used in slabs-ongrade, pavement,basement,walls, small foundations, and curb-and-gutter.

Answer 5

Plain Concrete

Question 6

TRUE OR FALSE.

Plain concrete has compressive strength—the ability to resist crushing loads; however, its tensile strength is only about 5% of its compressive strength.

Answer 6

FALSE= 10%

Question 7

It is a combination of adequate reinforcement (usually steel bars with raised lugs called deformations) and concrete designed to work together to resist applied loads. Properly placed reinforcement in concrete improves its compressive and tensile strength.

Answer 7

Reinforced Concrete

Question 8

Is a structural concrete in which internal stresses have been introduced to reduce potential tensile stresses in the concrete resulting from loads.

Answer 8

Prestressed Concrete

Question 9

What do you call the introduction of internal stresses which is usually acomplished through the use of tendons that are tensioned or pulled tight prior to being anchored to the concrete.

Answer 9

Prestressing

Question 10

This consist of strands,wires,cables,bars,rods, or bundles of such elements.

Answer 10

Tendons

Question 11

TRUE OR FALSE.

Tendons are usually made from low-strength steel, but can also be made from other materials such a FRP

Answer 11

FALSE=High-strength steel

Question 12

What is FRP?

Answer 12

Fiberglass-reinforced polymer

Question 13

TRUE or FALSE. (ADVANTAGES of Reinforced Concrete)

Reinforced concrete has considerable compressive strength per unit cost compared with most other materials.

Answer 13

TRUE

Question 14

TRUE or FALSE. (ADVANTAGES of Reinforced Concrete)

Reinforced concrete doesn’t have great resistance to the actions of fire and water, and in fact is not the best structural material available for situations where water is present.

Answer 14

FALSE.

(It has great resistance & is the BEST structural material)

Question 15

TRUE or FALSE. (ADVANTAGES of Reinforced Concrete)

Renforced concrete structures are not very rigid.

Answer 15

FALSE

(They are rigid.)

Question 16

TRUE or FALSE. (ADVANTAGES of Reinforced Concrete)

Reinforced concrete, as compared with other materials, ha a very long srvice life.

Answer 16

TRUE

Question 17

TRUE or FALSE. (ADVANTAGES of Reinforced Concrete)

Reinforced is usually the only economical material which is not available for footing, floor slabs, basement walls, piers, and similar applications.

Answer 17

FALSE

(AVAILABLE)

Question 18

TRUE or FALSE. (ADVANTAGES of Reinforced Concrete)

A special feature of concrete is its ability to be cast into an extraordinary variety of shapes from simple slabs, beams, and columns to great arches and shells.

Answer 18

TRUE

Question 19

TRUE or FALSE. (ADVANTAGES of Reinforced Concrete)

In most areas, concrete takes advantage of inexpensive local materials (sand, gravel, and water) and requires relatively small amounts of cement and reinforcing steel, which may have to be shipped from other parts of the country.

Answer 19

TRUE

Question 20

TRUE or FALSE. (ADVANTAGES of Reinforced Concrete)

A higher grade of skilled labor is required for the erection compared with other materials such as structural steel.

Answer 20

FALSE

(A lower grade)

Question 21

TRUE or FALSE. (DISADVANTAGES of Reinforced Concrete)

Conrete has a very high tensile strength, requiring the use of tensile reinforcing.

Answer 21

FALSE

(Very low tensile strength)

Question 22

TRUE or FALSE. (DISADVANTAGES of Reinforced Concrete)

Forms are required to hold the concrete in place until it hardens sufficiently.

Answer 22

TRUE

Question 23

TRUE or FALSE. (DISADVANTAGES of Reinforced Concrete)

The high strength per unit of weight of concrete leads to light members.

Answer 23

FALSE

(Low strength= heavy members)

Question 24

TRUE or FALSE. (DISADVANTAGES of Reinforced Concrete)

Low strength per unit volume of concrete means members will be relatively large, an important consideration for tall buildings and long-span structures.

Answer 24

TRUE

Question 25

TRUE or FALSE. (DISADVANTAGES of Reinforced Concrete)

The properties of concrete doesn’t vary widely because of variations in its proportioning and mixing.

Answer 25

FALSE

(Properties of concrete vary widely)

Question 26

Stress- strain curves of concrete cylinders are almost identical to those for the compression sides of _________.

Answer 26

Beams

Question 27

It should be further noticed that the ________ grades of concrete are _________ than the stronger ones – that is, they will take larger strains before breaking.

Answer 27

Weaker, less brittle

Question 28

Mechanical Properties of Concrete

Compressive Strength

3000psi – 4000psi (20.68MPa – 27.58MPa)

Answer 28

For ordinary applications

Question 29

Mechanical Properties of Concrete

Compressive Strength

5000psi – 6000psi (34.47MPa – 41.37MPa)

Answer 29

For prestressed construction

Question 30

Mechanical Properties of Concrete

Compressive Strength

<9000psi – 10000psi (62.05MPa – 68.95MPa)

Answer 30

For some applications such as the columns of the lower stories of high-rise buildings

Question 31

Value varies with different concrete strengths, concrete age, type of loading, and the characteristics and proportions of the cement and aggregate

Answer 31

Modulus of Elasticity

Question 32

This is the slope of the stress-strain diagram at the origin of the curve.

Answer 32

Initial Modulus

Question 33

This is the slope of a tangent to the curve at some point along the curve - for instance, at 50% of the ultimate strength of concrete.

Answer 33

Tangent Modulus

Question 34

The slope of a line drawn from the origin to a point on the curve somewhere between 25% and 50% of its ultimate compressive strength is referred to as?

Answer 34

Secant Modulus

Question 35

This is determined by using the stresses and strains obtained after the load has been applied for a certain length of time.

Answer 35

Apparent modulus or long-term modulus

Question 36

▸ the ratio of lateral expansion to the longitudinal shortening
▸ values vary from 0.11 for the higher-strength concretes to as high as 0.21 for the weaker-grade concretes

Answer 36

Poisson’s Ratio

Question 37

after the concrete has been cured and begins to dry, the extra mixing water that was used begins to work its way out of the concrete to the surface, where it evaporates as a result, the concrete shrinks and cracks

Answer 37

Shrinkage

Question 38

under sustained compressive loads, concrete will continue to deform for long periods of time
▸ after the initial deformation occurs, the additional deformation is called?

Answer 38

Creep/Plastic Flow

Question 39

TRUE OR FALSE. CREEP

The longer the concrete cures before loads are applied, the smaller will be the creep.

Answer 39

TRUE

Question 40

TRUE OR FALSE. CREEP

Lower-strength concretes have less creep that do higher-strength concretes stressed at the same values.

Answer 40

FALSE
(Higher strength concretes=less creep)

Question 41

TRUE OR FALSE. CREEP

Creep increases with higher temperatures.

Answer 41

TRUE

Question 42

TRUE OR FALSE. CREEP

The higher the humidity, the smaller will be the free pore water that can escape from the concrete, thus
lesser creep.

Answer 42

TRUE

Question 43

TRUE OR FALSE. CREEP

Concretes with the highest percentage of cement-water paste have the highest creep because the paste, not the aggregate, does the creeping.

Answer 43

TRUE

Question 44

This will creep proportionately less than smaller thin members where the free water has smaller distances to travel to escape.

Answer 44

Large Concrete Members

Question 45

varies from about 8% to 15% of concrete’s compressive strength
▸ two indirect tests developed to measure concrete’s tensile strength:
▸ modulus of rupture test ▸fr= 0.62 sqrt f’c inMPa
▸ split-cylinder test

Answer 45

Tensile Strength

Question 46

varies from one-third to four-fifths of the ultimate compressive strength

Answer 46

Shear Strength

Question 47

2 types of Reinforcing Bars

Answer 47

A. Plain
B. Deformed

Question 48

A type of reinforcing bar which is not used very often except for wrapping around longitudinal bars, primarily in columns.

Answer 48

Plain

Question 49

A type of reinforcing bars which have ribbed projections rolled onto their surfaces to provide better bonding between the concrete and the steel.

Also, these are used for almost all applications.

Answer 49

Deformed.

Question 50

Frequently used for reinforcing slabs, pavements, and shells, and places where there is normally not sufficient room for providing the necessary concrete cover required for regular reinforcing bars

Answer 50

Welded wire fabric

Question 51

reinforcing bars may be rolled from

Answer 51

Billet steel, axle steel or rail steel

Question 52

4 minimum yield strength levels of bars:

Answer 52

Grade 40 (280 MPa);
Grade 60 (420 MPa);
Grade 75 (520 MPa); and
Grade 80 (550 MPa).

Question 53

ASTM A615(Marked with letter S for the type of steel)

Answer 53

Deformed and plain bilet steel bars

Question 54

ASTM A706 : (Letter W)which are to be used where controlled tensile properties and/or specially controlled chemical composition is required for welding purposes.

Answer 54

Low-alloy deformed and plain bars.

Question 55

ASTM A706 available in 2 grades

Answer 55

Grade 60 (420 MPa)
Grade 80 (550 MPa)

Question 56

Deformed rail steel or axle steel bars. They must be marked with the letter R (for type of steel).

Answer 56

ASTM A996

Question 57

When deformed bars are produced to meet both the A615 and A706 specifications, they must be marked with what letters?

Answer 57

letters S and W

Question 58

*Structural code addressing the design and installation of structural systems in the Philippines
▸ Not legally enforceable document
▸ Set of recommendations or statement of current good practice in reinforced concrete design

Answer 58

NSCP 2015

Question 59

WHAT IS ASEP?

Answer 59

Association of Structural Engineers of the Philippines

Question 60

organization of structural designers/engineers in the Philippines

Answer 60

ASEP (Association of Structural Engineers of the Philippines)

Question 61

What do you call the cement in which the Romans used?

Answer 61

Pozzolana

Question 62

Where do they found large deposits of a sandy volcanic ash?

Answer 62

Mt. Vesuvius and other places in Italy

Question 63

a concrete structure made by Romans which are dedicated to all gods which are located in Rome and was conpleted in ad 126

Answer 63

Pantheon

Question 64

what year was the real breakthrough for concrete?

Answer 64

1824

Question 65

An English bricklayer named ________ obtained a patent for a cement that he called _______ after long and laborious experiments.

Answer 65

Joseph Aspdin; portland cement

Question 66

the ability to resist crushing loads

Answer 66

compressive strength

Question 67

the curves are roughly straight while the load is increased from 0 to about 1/3 to 1/2 the concrete’s ultimate strength.

Answer 67

concrete stress strain curve