Concrete Flashcards

1
Q

What is concrete made of?

A

Water, cement and aggregates (coarse and fine)

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2
Q

What is air entrainement?

A

The act of putting tiny air bubbles in concrete

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3
Q

Will freshly placed concrete submerged underwater harden?

A

Yes

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4
Q

What is the desire temperature for concrete?

A

73 degrees Fahrenheit

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5
Q

What are the two functions of water in the mix?

A

Workability and Hydration

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6
Q

What is the purpose of aggregates in the mix?

A

Gain economy

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7
Q

What percentage of the mix do the aggregates represent?

A

60-80%

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8
Q

What are the important factors in selecting the aggregates?

A

Free from chemicals or coating of material

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9
Q

What is the maximum size for aggregates in a vertical structure?

A

1/5 of the width

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10
Q

What is the maximum size not to exceed for aggregates in a slab?

A

1/3 of the thickness of the slab

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11
Q

What is the maximum size not to exceed for aggregates in reinforced concrete?

A

3/4 of the clear space between re-bars?

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12
Q

What are the five main types of cement and what are the curing time?

A
I. Normal 28 days
II. Modified 45 days
III. High early 7 days
IV Low heat 90 days
V. Sulfate resistant 60 days
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13
Q

What can be added to concrete to speed up the curing process?

A

Calcium Chloride

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14
Q

When would you use type V (Sulfate resistant) Portland cement?

A

When the soil or water on site have a high sulfate content

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15
Q

What are the three different shipping options?

A

Bags-94 LBS
Barrels- 376 LBS (= four bags)
Rail cars

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16
Q

What are the different type of concrete?

A

Reinforced
Prestressed
Precast
Lightweight

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17
Q

What are the characteristics of the plastic state?

A

Readily moldable
Change shape slowly if forms are removed
Workable non-segregated
Uniform

18
Q

What is the purpose of contraction joints?

A

They serve to eliminate unsightly random surface cracks

19
Q

What are the two different categories of contraction joints?

A

Controlled (induced cracks) vs. Construction

20
Q

What is the purpose of expansion joints?

A

They are placed when pouring next to an existing structure to minimize or eliminate damages to the structure

21
Q

What are the characteristics of forms?

A

Tight, rigid ans strong

22
Q

What are the materials used for form?

A

Wood
Metal
Earth
Fiber

23
Q

What are the constituents of a wooden form(Wall)?

A
Sheathing
Studs
Wales
Strong Back
Braces
Shoe Plates
Spreaders
Tie Wires
24
Q

What are the constituents of a wooden form(Column)?

A

Sheathing
Batten
Yokes (Top and Bottom)
Bracing

25
Q

What is the rate of filling not to exceed on large project?

A

4 Feet per hour vertically

26
Q

What is the maximum distance concrete can be dropped?

A

3-5 Feet

27
Q

What are the different finishing operations?

A
Screeding
Floating
Troweling
Brooming
Edging
28
Q

What is screeding and how many times should you screed the surface?

A

Screeding is the process of striking off the excess concrete in order to bring the surface to the right elevation. It should be done twice to remove surge of excess concrete

29
Q

When should floating be used?

A

If smooth surface is required?

30
Q

When should troweling method be used?

A

If smoother surface is required?

31
Q

When should the brooming method be used?

A

If a non-skid surface is required

32
Q

What is the minimum size of an expansion joint?

A

1/4 inch

33
Q

What defines cold weather conditions when pouring concrete?

A

Temperature lower than 40 degrees

34
Q

What actions should you take while working with concrete in cold weather conditions?

A
Keep concrete above 70 degrees
Add accelerators
After the first 3 days of warm curing keep concrete above freezing for 3 more days
Protect new concrete from exposure
Leave form on longer
35
Q

What is curing?

A

The steps necessary to keep concrete moist and as near as 73 F as practicable until it has reached its desired strength

Protect new concrete from exposure to the elements

36
Q

What are the steps to take while curing in hot weather conditions?

A
Keep temperature below 90 F
Start spraying as soon as final finishing
Loosen form as soon as possible
Add accelerators
Remove forms (7 days)
37
Q

What are the steps before pouring a concrete slab?

A
Compacting
Trimming
Moistening subgrade
Erecting forms
Setting reinforced rods
38
Q

When should you pour concrete under water?

A

When it is absolutely unavoidable

39
Q

What is the current maximum velocity when pouring concrete underwater?

A

10 ft/min

40
Q

What is the name of the column form?

A

Sonotube