Concrete

Question 1

What are Clinkers?

Answer 1

Cement raw materials finely ground and carefully proportioned before heated to temperatures from 2,000 to 3,000 degrees (F) to from hard pellets

Question 2

What is the composition of concrete

Answer 2

Mixture of aggregates and often controlled amounts of entrained air and held together by a hardened paste made from cement and water

Question 3

What is air entrainment

Answer 3

Air entrainment is the intentional creation of tiny air bubbles in concrete.

Question 4

What are the 3 components of concrete

Answer 4

Water
Aggregate: Sand/gravel
(Portland) Cement

Question 5

What is the most commonly used cement in the military

Answer 5

Portland Cement

Question 6

What is the chemical reaction called when water and cement mix?

Answer 6

Hydration

Question 7

What is the optimal temperature for cement hardening

Answer 7

73 degrees

Question 8

What 2 functions does water play in concrete

Answer 8

• Effect hydration

* Improve workability

Question 9

What determines the strength of concrete

Answer 9

ratio of cement to water

Question 10

Does more water or less water strengthen concrete

Answer 10

less water

Question 11

Aggregates make up what total volume of finished cement

Answer 11

60-80%

Question 12

What is the primary purpose of aggregate in cement

Answer 12

To gain economy

Question 13

What are the most common contaminating materials in concrete

Answer 13

dirt, clay, salt

Question 14

What are the rules of thumb for the maximum size aggregates should be in concrete

Answer 14

• The maximum size should not exceed 1/5 the minimum diameter of a wall or similar structure
  – Not to exceed 1/3 the slab thickness
  – Not to exceed 3⁄4 of the clear space between reinforcing bars

Question 15

What are the 5 types of Portland cement

Answer 15

– Type I (Normal Portland)
– Type II (Modified)
– Type III (High early)
– Type IV (Low heat)
– Type V (Sulfate resistant)

Question 16

What are 3 other cements

Answer 16

• White Portland
• Air Entrained (Type I, II, III)
• Oil Well Cements
• Waterproofed Portland cements
• Plastic cement

Question 17

What does a bag of Portland Cement weigh

Answer 17

– Bags-94 lbs (contains one cu ft of loose

measurement)

Question 18

How many and what are the types of CONCRETE

Answer 18

• Reinforced
• Prestressed
• Precast
• Lightweight

Question 19

What are the benefits of precast concrete

Answer 19

- In dead-loads making savings in
foundations and reinforcement
- Improved thermal properties
- Improved fire resistance
- Savings in transporting and handling pre- cast units on site
- Reduction in formwork and propping

Question 20

What are the disadvantages of concrete

Answer 20

• Low tensile strength
• Expands and contracts
• Shrinks when dry
• Heavy

Question 21

What do construction joints do?

Answer 21

join concrete that is paved at different times

Question 22

Do construction joints allow for movement of concrete members

Answer 22

No

Question 23

What do contraction joints do

Answer 23

control natural cracking from stresses caused by concrete shrinkage, thermal contraction, and moisture.

Question 24

At what angel are transverse contraction joints cut

Answer 24

At a right angle to the pavement centerline and edges.

Question 25

What do isolation joints do

Answer 25

separate the pavement from objects or structures, and allow independent movement of the pavement, object or structure without any connection that could cause damage.

Question 26

Where are isolation joints used

Answer 26

where a pavement joins sidewalks and buildings, and intersects other pavements or bridges.

Question 27

What do expansion joints do

Answer 27

Permit volume change movement of a concrete structure or member.

Question 28

What is the minimum width of an expansion joint

Answer 28

1/4′′ wide

Question 29

1 person can manually mix approximately how much concrete per hour

Answer 29

1 cubic yard

Question 30

Describe the hand mixing sequence of concrete

Answer 30

Three part gravel, then Two part sand (mix dry 3x), then One part Portland cement, and add water

Question 31

Project Volume (PV) = ?

Answer 31

length x width x height x number of pours

Question 32

Loss Factor = ?

Answer 32

if PV 5400 cubic ft (or 200 cubic yards), add 5% to project

Question 33

Loose Volume (LV) = ?

Answer 33

LF x 1.5 (and round up)

Question 34

Equation for calculating cement from Loose Volume (LV)

Answer 34

1/6 x LV = number of bags of cement (rounded up)

Question 35

Equation for calculating sand from Loose Volume (LV)

Answer 35

2/6 x LV = cubic feet (yards) of cement OR LV/3 = cubic feet (yards) of cement** **This may be "funny" math

Question 36

Equation for calculating gravel from Loose Volume (LV)

Answer 36

3/6 x LV = cubic feet (yards) of gravel OR LV/2 = cubic feet (yards) of gravel

Question 37

Equation for calculating gallons of water from number of bags of cement

Answer 37

Water (in gals) = number of bags of cement x 8

Question 38

Forms must be what in order to hold concrete properly until it sets

Answer 38

Tight, rigid, and strong

Question 39

What materials are forms usually made of

Answer 39

Wood, metal, earth, fiber

Question 40

What are the elements of wooden forms

Answer 40

Sheathing, batten, yoke, and bracing

Question 41

What does the yoke do in a wooden form

Answer 41

ties the top of sheathing together in column form

Question 42

What is the difference between a vertical keyway and a horizontal keyway

Answer 42

one is vertical and the other is horizontal

Question 43

What is the maximum rate of filling concrete to avoid excessive pressure on form

Answer 43

4 ft per hour

Question 44

How deep does the land under a slab need to be moistened (if plastic isn't being used as a barrier between the slab and the ground)

Answer 44

6 inches

Question 45

Slabs which will support load bearing walls must be what?

Answer 45

Reinforced with rebar

Question 46

True or False: Rebar in slabs must sit above the frost line

Answer 46

False. Must be below frost line