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A- General Engineering License > Concrete & Piles > Flashcards

Concrete & Piles Flashcards

1
Q

Single or double 2 x 4 lumber, which reinforces studs that are over 4’ tall is called?

A

Wales

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2
Q

What is the simplest type of form commonly used to contain shallow pours such as slab-on-grade or walks.

A

Edge Form

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3
Q

If concrete is kept moist for the full curing period of 28 days, it will reach greater than ___ % of its design strength.

A

125%

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4
Q

The minimum thickness of a concrete non-bearing tilt-up is?

A

4”

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5
Q

What type of foundation is used where there is too much ground water?

A

Crawl-space foundation

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6
Q

Shallow foundations and footings are usually embedded about how far into the soil?

A

One meter

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7
Q

For Column forms, what stabilizes and holds the form vertically? What also helps hold the sheating in place and resist the pressure from the concrete?

A

Bracing and yokes

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8
Q

What type of concrete is used when using quick - curing concrete?

A

Type III high early concrete

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9
Q

What is one of the horizantal supporting members that run between foundations, walls or beams to support a ceiling or floor?

A

Joist

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10
Q

Wall or column forms are commonly designed for a pour rate between?

A

4 - 8 ft/hr

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11
Q

Ties should be usually be placed within ____ from all form edges.

A

4 - 6”

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12
Q

What does the compressive strength of dry-mix shotcrete depend on?

A

Cement Aggregate Ratio

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13
Q

General range of shrinkage for shotcrete?

A

0.06 - 1.10% at 3 months

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14
Q

What is the name of a load bearing beam in a timber framed building?

A

Bressumer, breastsummmer, summer beam

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15
Q

After hardening, concrete should be kept wet for up to __days for proper curing.

A

8 days

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16
Q

Bacteria such as bacillus pasteurii, bacillus pseudofimus, bacillus cohnii, sporosarcina pasteuri and arthrobacter crystallopoietes do what to the compressive strength of concrete through their biomass?

A

Increases the strength

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17
Q

What is the point at which the ground rests against the foundation wall?

A

Grade line

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18
Q

Due to the way a reinforcement beam is bent under a load, bars at the bottom of a beam or slab are called ____ steel, and bars at the top are called ___ steel.

A

bottom -> positive

top -> negative

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19
Q

What is the definition of yield

A

it is the total weight of ingredients divided by the unit weight (or mass) of the freshly mixed concrete

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20
Q

What are the types of fly ash and what is it?

A

It reacts with calcium hydroxide producing the same binder as cement. There is Class C and F where F has lower early strengths. Enhances workability, can reduce air and cheaper.

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21
Q

Mixing Water: Hydration and Heat of Hydration

A

Water serves two purposes: to combine chemically with the cement, and to provide needed workability. Water needed for hydration is about half that needed for workability. Heat is generated as cement binds with the aggregate. .

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22
Q

Water Cementitious material ratio (w/c)

A

Basis for concrete mixture porportioning. Pounds of water per pounds of cement. A higher w/c lowers the strength and affects other qualities.

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23
Q

What sieve size determines fine or coarse aggregates?

A

The 1/4 inch sieve is the dividing point (what passes is fine).

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24
Q

General Rule for maximum size aggregate?

A 
Aggregate size is limited to the lessor of:
> 1/4 the space between side forms
> 3/4 the space between reinforcing bars
> 1/3 depth of a slab on the ground
Usually: 3/8", 3/4", 1" or 1-1/2"
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25
Q

Retarders vs. accelerator

A

A retarder is used in hot weather to extend setting time where an accelerator shortens the setting time and is used in cold weather.

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26
Q

Air-Entraining Agents

A

Essential for duraility when concrete is exposed to feezing and thawing and the application of deicing salts. Other benefits: workability, less water content, uniformity of the mix and mix holds better. (Do not use with hand troweled interior flatwork normal weight concrete).

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27
Q

Water addition rule of thumb

A

Adding 1 gallon of water per cubic yard of conrete will increase the slump by approximately 1 inch and will reduce compressive strength by approximately 150 psi.

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28
Q

What are the two cardinal requirements for cylinder strength tests?

A
  1. The average of any three successive tests must equal or exceed specified strength
  2. No test may fall below the specified strength by more than 500 psi.
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29
Q

If the concrete is exposed to freezing and thawing, air content should never be less than?

A

4%

30
Q

Gang Forms

A

Built by assembling a number of samller prefabricated panel forms into one large form. (Sections stay intact)

31
Q

Flying Table Forms

A

Large prefabricated forms for multistory building slabs.They contain their own support system and leveling jacks.

32
Q

ICF

A

Insulating concrete forms - stay-in place forms that are assembled as interlocking blocksor sheets. Provide an insulation value to the finished wall

33
Q

Slipforms

A

Place concrete by extrusion. Use jacks, rail systems and self-propelled machines to make it happen.

34
Q

Jump Forms

A

Rather than extruding the concrete, the form is “cycled”, that is, filled with concrete, stripped, and then “jumped” to the next level after the concrete is set.

35
Q

Safety factor for ties and hangers

A

2:1; the working load of new ties should be one-half the specified tensile strength

36
Q

Form anchors and safety factor

A

Devices used to secure formwork to previously placed concrete. The SF is 3:1.

37
Q

Camber

A

Is the amount of upward deflection anticipated when the concrete fills the form and the shores are removed.

38
Q

Concrete should not be dropped over _ ft without using a drop chute

A

5 feet

39
Q

How much camber is needed per 10 foot span to handle deflection movements?

A

1/4” per 10 feet

40
Q

General times for stripping forms?

A

12 hours for walls and columns. Up to 28 days for cambered elements.

41
Q

What is screeding?

A

The act of striking-off the concrete to form a smooth plane surface.

42
Q

To resist the diagonal tension, what are placed vertically along the beam?

A

Small U-or hoop-dahped reinforcing bars called stirrups

43
Q

What are the two strength grades of steel for bar?

A

Grade 420 => 60,900psi

Grade 520 => 75,400 psi

44
Q

What are the typical minimum covers for cast-in-place concrete?

A

Bundled Bars => 2 inches
Against exposed earth => 3 inches
Corrosive or severe weather => 2 in. for walls and slabs and 2-1/2 in. for other members

45
Q

Unreinforced concrete has a high compressive strength but its tensile strength is only about __ percent of its compressive strength

A

10%

46
Q

The minimum clear spacing between parallel bars should be equal to:

A

The diameter of the large aggregate or the bar, but not less than 1 inch.

47
Q

In slabs or walls, what is a reasonable tolerance in spacing individual bars?

A

3 inches

48
Q

The tolerance for the longitudinal locations of bends and ends of reinforcement is?

A

2 inches except at discontinuous ends of a member it is 1/2in.

49
Q

Top bars should be positioned within ___ of the height called for due to the most serious problems occuring with improper placement of top bars.

A

1/4 in.

50
Q

Lap Splices

A

The bars are lapped next to eachother at a certain length and securely wired together with tie wire. The lap should not be less than 12”

51
Q

Mechanical Splices

A

Couplers - for tensile and compressive forces

End-bearing devices - transfer compressive forces only

52
Q

Most concrete shrinks by how much in 100ft?

A

3/8in. to 3/4in

53
Q

Creep

A

Deformation that begins and continues for as long as the concrete is loaded.

54
Q

What are the four types of joints used in concrete walls and slabs?

A
  1. Contraction or Control Joint - movements
  2. Isolation or Expansion Joint - restraint/separation
  3. Conctruction Joint - convenience
  4. Warping - longitudinal - cracking due to temperature
55
Q

Typical spacing for contraction joints?

A

In general:
20ft apart in exterior walls with frequent openings
24ft apart in walls without openings

56
Q

A temperature change of 100F will cause concrete to expand or contract approximately:

A

3/4 in. in 100 linear feet

57
Q

The initial shrinkage of concrete from drying is:

A

3/4 in. in 100 linear feet

58
Q

Contraction joint are not intended to prevent cracks but to cause them by cutting into the slab to a depth of:

A

One-fourth the slab thickness or a minimum of 1 inch.

59
Q

Contraction joint spacing?

A

Space them in feet approximately 2-1/2 times the slab depth in inches

60
Q

For a floor slab, the joints should be spaced as that the panels are as near to square as possible. The ratio of panel length to width should not exceed:

A

1-1/2 to 1 (long side to short side)

61
Q

Expansion joint material should be approximately what thickness?

A

1/4 to 1/2 inch

62
Q

What is the sole purpose of welded wire reinforcement?

A

To prevent cracks from opening - and is placed in the upper part of the slab - 2 inches or within the upper third below the surface.

63
Q

What is the MINIMUM vertical reinforcement spacing for a reinforced concrete foundation wall that is 7 feet high and 10 inches thick on type SP soil?

A

56 inches on center.

64
Q

The amount of water per sack of cement is what controls all EXCEPT

A

set up speed.

65
Q

What is the MINIMUM compressive strength for concrete used in a foundation wall that will be exposed to weather?

A

2,500 psi.

66
Q

Increasing the slump of concrete does which of the following?

A

increases its wetness

67
Q

What is the maximum slump that concrete should have if it is to be used for floor slabs?

A

4 inches

68
Q

What is Post-tensioning? Prestressing?

A

The steel is stressed (pulled or tensioned) before the concrete has to support the service loads

69
Q

Two fundamental types of pike foundations?

A

Friction

End Bearing

70
Q

Consolidation definition

A

Is a process that removes air pockets and forces the concrete into all parts of the forms

71
Q

Control joints are generally located how many ft. apart on concrete slabs on grade, as a rule, __________ to __________ times the thickness.

A

2 to 3 times the thickness

A- General Engineering License (13 decks)

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