CONCRETE II

Question 1

Who is Joseph Aspdin?

Answer 1

He applied for a patent to make cement with English Portland limestone… In 1824

Question 2

Who was Duff A. Abrams?

Answer 2

He developed the weaker and less durable poured in-place concrete that had steel reinforcing… He develops the water – cement ratio law in 1918

Question 3

How did Joseph Monier influence Francois Hennebique?

Answer 3

Joseph Monier exhibited iron mash reinforce flowerpots and basins at the Paris exposition of 1867…Hennebique was inspired to develop his own building system using reinforced concrete, patented in 1892

Question 4

Eugene Freyssinet patented what?

Answer 4

A long span bridge design in 1928

Question 5

What is different about high-volume fly ash?

Answer 5

It only needs two thirds of the water used in conventional concrete

Question 6

Concrete cure is just as well in air as in…

Answer 6

Water

Question 7

What are the ingredients of Portland cement?

Answer 7

Lime, silica, iron oxide, and alumina

Question 8

What is fine aggregate size and what is course aggregate size?

Answer 8

Fine aggregate:

Question 9

Talk to me about the efficiencies of large aggregate versus small aggregate.

Answer 9

Large aggregate is economical. Small aggregate is left economical. Large and small together are the most economical.

Question 10

The largest pieces of aggregate should be no more then what percentage of the thickness of concrete slabs, or what percentage of the minimum space between reinforcing bars?

Answer 10

1/3 the thickness of concrete slab, 3/4 the minimum space between reinforcing bars

Question 11

What does a 1:3:5 mix mean?

Answer 11

One part cement, three parts fine aggregate, and five parts coarse aggregate

Question 12

How many days after being poured does concrete reach its full compressive strength?

Answer 12

28 days

Question 13

How long does it take high early strength concrete to reach its full compressive strength?

Answer 13

7-14 days

Question 14

What is the usual range for structural concrete strength?

Answer 14

3,000 - 6,000 psi. (4,000 being the most common)

Question 15

What is the difference between ready mixed concrete and transit mix concrete?

Answer 15

Ready-mixed is mixed at a plant and transported in an agitator trunk with a revolving chamber. Transit mix concrete is when a truck picks up dry and wet materials and mixes them en route.

Question 16

What is the diameter of a #3 rebar?

Answer 16

3/8”

Question 17

What is the most common reinforcing bar strength called and what is the strength?

Answer 17

A615 Grade 60, which is 60,000 psi

A615 refers to billet steel

Question 18

What can you put over rebar and concrete structures are exposed to chlorides like salts or seawater?

Answer 18

Epoxy coated or galvanized

Question 19

How much does normal concrete weigh? How much does lightweight structural concrete weigh?

Answer 19

150 lbs versus 90-115 lbs per cubic foot

Question 20

What is insulating lightweight concrete? What are three ways to make it?

Answer 20

15 - 90 lbs per cubic foot, generally used for thermal insulation in the roof construction, it has relatively low compressive strength

To make it:

1. Use aggregates of expanded materials like perlite or vermiculite
2. Use only coarse aggregate, creating voids
3. Incorporate a uniform cellular structure of air voids

Question 21

What is Gunite? Where is it especially useful?

Answer 21

Pneumatically placed concrete…

Because it’s shot with compressed air it works well for placing concrete over large surface areas with thin sections, like the sides and bottoms of swimming pools or for repair work

Question 22

A vertical drop in placing concrete cannot be higher than how many feet?

Answer 22

4 feet

Question 23

What does vibration do for concrete?

Answer 23

Gets rid of the air bubbles which could compromise strength, greater density, homogeneity, durability, more complete contact with the reinforcing bars

Question 24

What is the slump?

Answer 24

The amount the slump lowers after the cone is removed

Question 25

Expansion joints are required in these four places

Answer 25

1. Where a low building abuts a high building 2. In a concrete building over 200 feet long 3. At the intersection of building wings 4. When a new building adjoins an existing building

Question 26

What is the difference between isolation joints and expansion joints?

Answer 26

Expansion joints allow free movement of adjacent parts due to expansion or contraction… Isolation joint provide a separation between a slab on grade and columns are wall so that each can move independently

Question 27

What is the purpose of prestressed concrete?

Answer 27

To cause stress is in the concrete that are opposite indirection from those caused by future external loads.... The goal being to produce compression through the entire cross-section of the beam through the combination of prestress an external data and live loads… Therefore more efficient and economical use of material, especially in long span applications

Question 28

What is the difference between pretensioning and posttensioning?

Answer 28

Pretensioning lens itself to mass production, cast away from the building site, tensioned by jacks before placing concrete Posttensioning is usually prestressed on site, and prestressed after the concrete is cured, therefore less losses after tensioning

Question 29

How strong does concrete need to be in order to be prestressed?

Answer 29

5000 PSI or more

Question 30

What is tilt up construction?

Answer 30

When you cast a wall panel on top of the floor slab, and then tilt it into position

Question 31

What is tube slab construction?

Answer 31

This is when you put paper tube fillers embedded into the section of a concrete slab to allow for mechanical and duct spaces to be integrated into the thickness of the system for flat ceilings with no exposed beams