Flashcards in concrete Deck (22)
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1
who was the first to create concrete
romans
2
who rediscovered the cement we know today and when and where?
Joseph Aspidin, 1824
-Isle of Portland, England --> "Portland Cement"
3
what are 3 main ingredients to concrete and % used
1. water 15-20%
2. aggregates 60-75%
3. cement 10-15%
4. entrained air 5-8%
4
what does water have to be in order to be used to make concrete?
potable
5
what does aggregates have to be in order to be used to make concrete?
1.clean
2.inert
6
3 ingredients in cement
1. lime
2. silica
3. alumina
7
what are minor components added to cement
1. flyash
2. blast furnace slag
8
what is fly ash a biproduct of and what are its benefits
- residue from coal burning plants
-makes stronger, more durable, easier to work with
9
where does blast furnace slag come from and what are its benefits
- iron ore
-lowers heat of hydration, increase workability
10
how is cement bound together?
ingredients mixed, ground and super heated to point where bound together --> Clinker
-pulverized to create cement powder
11
what is heat of hydration
resulting heat generated by chemical reaction between cement and water
12
what are 2 factors most likely to cause excessive 'Heat of Hydration'
1. large pours of concrete
2. concrete with high cement content
13
what is the most common type of cement
Portland
14
what is another type of white cement
Medusa
15
why add entrained air to concrete?
1. increased durability
2. increased workability
16
what is the slump test
-create a frame and pour concrete in
-remove frame, measure how far concrete drops
-high slump= wet concrete
-low slump= dry concrete
17
what are the 4 steps to lay concrete
1. placing--> do so close to where will be finished
2. Consolidation--> removes pockets of air
3. finishing/ strike off --> removes excess concrete (screed) , levels to top of forms
4. curing
18
name 5 types of ways to finish concrete
1. bull floating
2. broom
3. rake
4. darby
5. spin float
19
name 4 ways to aid in curing concrete
1. wet burlap
2. liquid membrane
3. polyethelyne sheets
4. straw/ hay (in xtreme cold)
20
name 2 ways to reinforce concrete
1. rebar
2. steeplates
21
name 3 joints in concrete
1. control joints
2. isolation/ expansion joints
3. construction joints
22
