Transporting And Placement Of Concrete Flashcards

1
Q

What happens if concrete is over-vibrated

A

Segregation of course aggregates

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2
Q

What is max size of Aggs when pumping concrete

A

1/3 size of hoes

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3
Q

When should forms be marked with pour height

A

After one side has been erected

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4
Q

What material is used for expansion joints

A

Asphalt impregnated fibreboard

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5
Q

What is used in the wet screed method

A

Concrete

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6
Q

Who establishes legal location of buildings

A

Legal surveyor

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7
Q

What truck is loaded with individual ingredients and mixes them together while on the way to site?

A

A ready mix truck

Pg. 13

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8
Q

What is a cold joint?

A

A cold joint occurs when fresh concrete is placed against previously placed concrete that has already begun to set.

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9
Q

Concrete should not be allowed to fall more then 1.5m? (True or false)

A

True, if concrete is allowed to free fall more then 1.5m it can cause the aggregate to separate from the paste.

Pg. 19

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10
Q

Once the hydration process has begun, how much time do you have to place the concrete?

A

2 hours.

Pg. 14

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11
Q

What factors influence hydro static pressure in fluid concrete?

A

•slump
•height of pour
•rate of pour
•ambient temperature

Pg. 22

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12
Q

How much shrinkage is expected is expected within the first three months?

A

75% of total expected shrinkage

Pg. 24

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13
Q

A truck that carries all ingredients to site and mixes them together on site is called a?

A

Mobile batch truck.

Pg. 14

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14
Q

When is a Mobile batch truck needed over a regular truck?

A

When the location of pour is outside of the 2 hour placement window.

Pg. 14

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15
Q

What’s the purpose of form watching?

A

To inspect and watch concrete forms for potential failure.

Pg. 25

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16
Q

When should the wall form be marked with the pour height?

A

Once one side of the form has been placed.

Pg. 2

17
Q

How should an emersion be used?

A

It should be quickly lowered down through the fresh concrete at least 150mm into the previous lift and withdrawn slowly in and up and down motion.

Pg. 20

18
Q

If you’re mom’s vibrator is not available, consolidation is done by what?

A

Rodding or spading

19
Q

What two factors affect slump?

A

Water/cement ratio, and the addition of admixtures such as plasticizes and retards

20
Q

What increases as the height of concrete increases in forms?

A

Lateral pressure

21
Q

Standard mix of cured concrete may expand about ___mm per ___m of concrete length when subjected to a differential of 50°C.

A

5mm per 10m

22
Q

Pre-stressed concrete has the reinforce members ______ prior to the load of concrete being applied

A

Tensioned