G1 - LT #2 Flashcards
Three basic elements of concrete are:
Cement, water and aggregates
The rocklike substance produced by a kiln is called:
Clinkers
The four basic ingredients used in the manufacture of cement are:
Iron, silica, alumina and limestone
Normal Portland cement is now known as:
GU cement
High Early strength hydraulic cement is:
HE cement
LH cement is used for:
Low heat of hydration concrete
Expansive cements cause concrete to:
Expand during setting
Good aggregates should be shaped:
Round or cubical
Fine aggregates are usually considered to be:
Less than 5 mm
An accelerator is an example of an:
Admixturre
The masonry cement best suited for foundation is:
Type M
Major greenhouse gas produced by cement industry is:
CO2
One way of reducing CO2 during cement production is to:
Decrease the amount of clinker used
What is the proper size for a slump cone?
100 mm TOP Diameter
200 MM BOTTOM Diameter
300 MM HEIGHT
Name three qualities of properly proportioned concrete mix:
Economical, workable, strong, durable finish
How is slump measured?
The distance from the top of the cone to the top of concrete.
To make strong, durable, concrete, the water-cement ratio should be:
LOW
What is the importance of water-cement ratio and minimum cement content?
Strength of the mix and economy
In concrete, aggregates make up:
60 to 80 percent of the mix concrete
Except for slabs-on-grade, the size of aggregates should be ____ of one member
1/5th the thickness of one member
Concrete that is being pumped should have:
A superplasticizer added
When is high sulphate resistant hydraulic cement used?
Where soil or groundwater has a very high sulphate content
Up to 20% of concrete can be replaced with:
Fly ash to reduce the cost of the concrete mixture.
What is blended hydraulic cement?
Contains 25 to 70% granulated blast-furnace slag and up to a maximum of 40% pozzolan
Sets slower, improved properties in hardened concrete
Air entrained Portland cements are useful for?
Improve resistance to freeze-thaw conditions and to scaling caused by chemicals applied for snow & ice removal.
Oil-well cement used for”
Sealing oil and gas wells during drilling
The entire amount of aggregates in concrete needs to be:
Mix of: Evenly graded pieces, not too many small and not too many large
Exposed aggregate work uses what kind of aggregates?
Gap-graded aggregates, large size of 3/8 diam. next largest being sand. Gap produces an even pebbled surface to concrete.
Water impurities in concrete mix can cause:
Efflorescence, staining or corrosion of re-bar
When slabs on grade are not reinforced, what is the max. size of aggregate?
Not more than one-third of slab thickness
