Concrete

Question 1

What is concrete made of?

Answer 1

Water, cement and aggregates (coarse and fine)

Question 2

What is air entrainement?

Answer 2

The act of putting tiny air bubbles in concrete

Question 3

Will freshly placed concrete submerged underwater harden?

Answer 3

Yes

Question 4

What is the desire temperature for concrete?

Answer 4

73 degrees Fahrenheit

Question 5

What are the two functions of water in the mix?

Answer 5

Workability and Hydration

Question 6

What is the purpose of aggregates in the mix?

Answer 6

Gain economy

Question 7

What percentage of the mix do the aggregates represent?

Answer 7

60-80%

Question 8

What are the important factors in selecting the aggregates?

Answer 8

Free from chemicals or coating of material

Question 9

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

Answer 9

1/5 of the width

Question 10

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

Answer 10

1/3 of the thickness of the slab

Question 11

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

Answer 11

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

Question 12

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

Answer 12

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

Question 13

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

Answer 13

Calcium Chloride

Question 14

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

Answer 14

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

Question 15

What are the three different shipping options?

Answer 15

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

Question 16

What are the different type of concrete?

Answer 16

Reinforced
Prestressed
Precast
Lightweight

Question 17

What are the characteristics of the plastic state?

Answer 17

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

Question 18

What is the purpose of contraction joints?

Answer 18

They serve to eliminate unsightly random surface cracks

Question 19

What are the two different categories of contraction joints?

Answer 19

Controlled (induced cracks) vs. Construction

Question 20

What is the purpose of expansion joints?

Answer 20

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

Question 21

What are the characteristics of forms?

Answer 21

Tight, rigid ans strong

Question 22

What are the materials used for form?

Answer 22

Wood
Metal
Earth
Fiber

Question 23

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

Answer 23

Sheathing
Studs
Wales
Strong Back
Braces
Shoe Plates
Spreaders
Tie Wires

Question 24

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

Answer 24

Sheathing
Batten
Yokes (Top and Bottom)
Bracing

Question 25

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

Answer 25

4 Feet per hour vertically

Question 26

What is the maximum distance concrete can be dropped?

Answer 26

3-5 Feet

Question 27

What are the different finishing operations?

Answer 27

``` Screeding Floating Troweling Brooming Edging ```

Question 28

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

Answer 28

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

Question 29

When should floating be used?

Answer 29

If smooth surface is required?

Question 30

When should troweling method be used?

Answer 30

If smoother surface is required?

Question 31

When should the brooming method be used?

Answer 31

If a non-skid surface is required

Question 32

What is the minimum size of an expansion joint?

Answer 32

1/4 inch

Question 33

What defines cold weather conditions when pouring concrete?

Answer 33

Temperature lower than 40 degrees

Question 34

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

Answer 34

``` 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 ```

Question 35

What is curing?

Answer 35

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

Question 36

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

Answer 36

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

Question 37

What are the steps before pouring a concrete slab?

Answer 37

``` Compacting Trimming Moistening subgrade Erecting forms Setting reinforced rods ```

Question 38

When should you pour concrete under water?

Answer 38

When it is absolutely unavoidable

Question 39

What is the current maximum velocity when pouring concrete underwater?

Answer 39

10 ft/min

Question 40

What is the name of the column form?

Answer 40

Sonotube