CONCRETE II Flashcards
Who is Joseph Aspdin?
He applied for a patent to make cement with English Portland limestone… In 1824
Who was Duff A. Abrams?
He developed the weaker and less durable poured in-place concrete that had steel reinforcing… He develops the water – cement ratio law in 1918
How did Joseph Monier influence Francois Hennebique?
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
Eugene Freyssinet patented what?
A long span bridge design in 1928
What is different about high-volume fly ash?
It only needs two thirds of the water used in conventional concrete
Concrete cure is just as well in air as in…
Water
What are the ingredients of Portland cement?
Lime, silica, iron oxide, and alumina
What is fine aggregate size and what is course aggregate size?
Fine aggregate:
Talk to me about the efficiencies of large aggregate versus small aggregate.
Large aggregate is economical. Small aggregate is left economical. Large and small together are the most economical.
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?
1/3 the thickness of concrete slab, 3/4 the minimum space between reinforcing bars
What does a 1:3:5 mix mean?
One part cement, three parts fine aggregate, and five parts coarse aggregate
How many days after being poured does concrete reach its full compressive strength?
28 days
How long does it take high early strength concrete to reach its full compressive strength?
7-14 days
What is the usual range for structural concrete strength?
3,000 - 6,000 psi. (4,000 being the most common)
What is the difference between ready mixed concrete and transit mix concrete?
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.
What is the diameter of a #3 rebar?
3/8”
What is the most common reinforcing bar strength called and what is the strength?
A615 Grade 60, which is 60,000 psi
A615 refers to billet steel
What can you put over rebar and concrete structures are exposed to chlorides like salts or seawater?
Epoxy coated or galvanized
How much does normal concrete weigh? How much does lightweight structural concrete weigh?
150 lbs versus 90-115 lbs per cubic foot
What is insulating lightweight concrete? What are three ways to make it?
15 - 90 lbs per cubic foot, generally used for thermal insulation in the roof construction, it has relatively low compressive strength
To make it:
- Use aggregates of expanded materials like perlite or vermiculite
- Use only coarse aggregate, creating voids
- Incorporate a uniform cellular structure of air voids
What is Gunite? Where is it especially useful?
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
A vertical drop in placing concrete cannot be higher than how many feet?
4 feet
What does vibration do for concrete?
Gets rid of the air bubbles which could compromise strength, greater density, homogeneity, durability, more complete contact with the reinforcing bars
What is the slump?
The amount the slump lowers after the cone is removed
Expansion joints are required in these four places
- Where a low building abuts a high building
- In a concrete building over 200 feet long
- At the intersection of building wings
- When a new building adjoins an existing building
What is the difference between isolation joints and expansion joints?
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
What is the purpose of prestressed concrete?
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
What is the difference between pretensioning and posttensioning?
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
How strong does concrete need to be in order to be prestressed?
5000 PSI or more
What is tilt up construction?
When you cast a wall panel on top of the floor slab, and then tilt it into position
What is tube slab construction?
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
