SOC Concrete Flashcards
(62 cards)
1
Q
- What are the raw materials in Portland cement?
A
Limestone Cement rock Oyster shells Marl (lime rich mud-lake sediment) Clay Silica Sand Iron Ore
2
Q
- What is the “clinkers”?
A
The raw material finely ground and carefully proportioned before heated to temperatures from 2000 to 3000 degrees (F) to form hard pellets called “Clinkers”
3
Q
- What is air entrainment?
A
The international creation of tiny air bubbles in concrete
4
Q
- What is the composition of concrete?
A
Mix of aggregates and entrained air held together by hardened paste made of cement and water
5
Q
- What is the most commonly used cement by the military?
A
Portland cement
6
Q
- What is hydration?
A
Hydration is the chemical reaction. It occurs when Portland cement is mixed with water.
7
Q
- What causes concrete to harden and what is the desired temperature?
A
Hydration and 73 degrees
8
Q
- What are the three major components?
A
Water
Aggregates
Portland Cement
9
Q
- What are two types of aggregate
A
1) Coarse aggregate (Rock)
2) Fine aggregate (sand)
10
Q
- What is aggregate?
A
It used as an inner filling material, made of sand and gravel. 60 to 80 percent of total concrete volume.
11
Q
- What is primary purpose of aggregates?
A
To gain economy
12
Q
- What are the most common contaminating materials of aggregate?
A
Dirt, clay and salt
13
Q
- What are the five types of Portland cement?
A
Type I (Normal Portland) Type ll (Modified) Type III (High early) Type IV (Low heat) Type V (Sulfate Resistant)
14
Q
- What is the normal cure time and some uses of type 1 portland cement?
A
28 days
It used for Pavement, Sidewalks, Bridges, Reservoirs, Building and etc
15
Q
- What is the normal cure time and some uses of type 2 portland cement?
A
45 days
Large super structures, large piers, heavy retaining walls
16
Q
- What is the normal cure time and some uses of type 3 portland cement?
A
High early -7 days
Used in cold weather and high heat
17
Q
- What is the normal cure time and some uses of type 4 portland cement?
A
Low heat -90 days
Large massive structures
18
Q
- What is the normal cure time and some uses of type 5 portland cement?
A
Sulfate Resistant – 60 days
Used where the soil, or water, in contact with the concrete has a high sulfate content
19
Q
- What types of Portland cement are air entrained?
A
Types1, 2 and 3
20
Q
- What does calcium chloride do to Portland cement?
A
It accelerates both hardening and strength gain by 2% the weight of cement
• 2 hours vs 6 hours
21
Q
- How does Portland cement ship?
A
Bags
94lb, contain one cu ft of loose measurement
Barrels
376lb = 4 bags
Rail cars
22
Q
- What is warehouse pack?
A
Sacked cement in storage packed too tightly
23
Q
- What are the types of concrete?
A
Reinforced
Prestressed
Precast
Lightweight
24
Q
- What is reinforced concrete?
A
Steel rods imbedded into the concrete is defined as reinforced concrete (strong in compression, but weak in tensile strength)
25
25. What is prestressed concrete?
Reinforced steel or welded wire mesh that is stretched out with tension before the concrete is poured.
26
26. What is precast concrete?
Concrete cast into something other than its final position
27
27. What is benefits of lightweight concrete?
a) In dead-loads making savings in foundations and reinforcement
b) Improved thermal properties
c) Improved fire resistance
28
28. What is benefits of plastic state?
a) Readily moldable
b) Changes shape slowly if forms are removed
c) Uniform
d) Workable nonsegregated
• It can be cast or molded into nearly any size or shape
29
29. What are some advantage of concrete?
a) High compressive strength
b) Can be cast, molded or shaped
c) Little maintenance and economical
d) Durable
e) Strength can be pre-determined
30
30. What are some disadvantage of concrete?
a) Low tensile strength
b) Expands and contracts
c) Shrinks when dry
d) Heavy
31
31. What is expands and contracts?
it is chemical reaction that occurs by moisture and temperature changes
32
32. What is width of expansion joint should never be?
Expansion joints should never be less than ¼ inch wide.
33
33. What is the difference between construction joints and expansion joints?
Construction joints are not intended to allow for movement of concrete. Expansion joints and contraction joints could be move around.
34
34. When can you place concrete underwater?
Placed underwater only when unavoidable.
35
35. If concrete must be placed underwater, what should the max velocity of the current be?
10 ft per min
36
36. When hand mixing cement, how much cement can be mixed by one man
One man can mix 1 cu yd per hour
37
37. When hand mixing concrete the sand, gravel and cement should be dry mixed how many times before adding water?
Three times
38
38. What is the formula for project volume (PV)?
PV = Length x Width x depth x number of structures.
| • Make sure keep in feet
39
39. What is the formula for Loss Factor (LF)?
• for cu ft
LF = PV x LF(<5400 cu ft =1.1 or > 5400 cu ft = 1.05)
• for cu yrds
LF = PV x LF(< 200 cu yds =1.1 or > 200 cu yds = 1.05)
40
40. What is the formula for loose volume (LV)?
LV = LF X 1.5
41
41. What rule do you use when calculating for materials when laying concrete?
1-2-3 rule
| 1/6 cement, 2/6 sand, and 3/6 gravel
42
42. What is the formula for convert cu ft to cu yrds?
Cu ft / 27 = cu yrds
43
43. When estimating for concrete work what is the rule called?
3/2 rule
44
44. What is forms?
it hold concrete until sets, produces the desired shapes and sometimes surface finishes. Can represent up to 1/3 of concrete structure’s total cost.
45
45. What is essential when set up forms?
Must be tight, rigid, and strong
46
46. What materials can be used make forms?
Wood (most common and economical)
Metal
Earth
Fiber
47
47. What are the elements of wooden forms (Concrete wall)?
```
Sheathing
Stud
Wales
Strong backs
Braces
Shoe plates
Spreaders
Tie wires
```
48
48. What are the elements of wooden forms (Concrete column)?
Sheathing
Batten
Yokes
Bracing
49
49. The rate of filling should not be exceed?
4 feet per hour vertically, to avoid excessive pressure on the forms
50
50. What is screeding?
Process of stiking off the excess concrete in order to bring the surface to the right elevation
51
51. What are techniques of finishing operation?
```
a) Floating
If smooth surface is required
b) Troweling
If smoother surface is required
c) Brooming
d) If non-skid surface is required
```
52
52. What determines the strength of concrete?
Ratio of cement to water
53
53. What are the rules of thumb for the maximum size aggregates should be in concrete?
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
54
54. Where are isolation joints used?
where a pavement joins sidewalks and building, and intersects other pavements or bridge.
55
55. What do expansion joints do?
Permit volume change movement of a concrete structure or member.
56
56. How much concrete can one person mix per hour?
1 cubic yard
57
57. how deep does the land under a slab need to be moistened?
6 inches
58
58. Slabs which will support load bearing walls must be what?
Reinforced with rebar
59
59. What is different between construction joint and Control joint?
1) Construction joints y allows builder to continue construction process.
2) Control joint is used at finishing state of construction.
60
60. What is sequence of concrete hand mixing?
a) Mix dry materials three times (sand, cement, and grave)
| b) Add water to achieve desire concrete strength
61
61. Ingredient Equation
```
PV = L x W x H x ( number of structure)
• Keep measurement in feet
Loss factor
LF= PV ( <5400 cu ft, add 10% (1.1)
LF= PV ( >5400 cu ft, add 5% (1.05)
Loose Volume
LV= LF X 1.5
• LV round up to whole number
CEMENT 1/6 X LV = bag of cement
SAND 2/6 X LV = CU ft
Gravel 3/6 x LV = CUft
Water 8 gal per bag of cement 8 x # of bag cement
```
If you ordering from truck,
LF = PV x (loss factor)(1.05)
Always going to be CU yard
62
62. Special curing techniques
```
1) Hot weather
keep temperature below 90 F degree
Loosen forms ASAP
Add accelerators
Remove forms (7 days)
```
2) Cold weather
40 degrees F or lower
Keep concrete above 70 degrees F
Add accelerators
