Components of Concrete Flashcards
What is aggregate? 
Granular material, such as sand, gravel, crushed stone, and iron, blast furnace slag, used with a cementing medium to form concrete or mortar 
What is admixture? 
An ingredient of concrete added before, or during its mixing to modify its properties 
What is concrete?
Mixture of portland cement, or any other cementitious material, fine aggregate, coarse aggregate, and water, with or without admixtures.
What are the components of concrete proportions?
Gravel 41%
Sand 26%
Water 15%
Cement 12%
Air 6%
What are Pozzolans?
Cementitious materials, often mixed with concrete. An example is fly ash and silica fume. Added to improve workability and act as a cement filler.
Normal weight aggregate shall conform to:
ASTM C33
Light weight aggregate shall conform to:
ASTM C330
Mixing water shall conform to:
ASTM C1602
Admixtures shall conform to:
- Water reduction and setting time modification: ASTM C494
- Producing flowing concrete: ASTM C1017
- Air entrainment: ASTM C260
- Inhibiting chloride-induced corrosion: ASTM C1582
Why are sulfates a problem?
Sulfurs are mineral salts, found in soil and in ground water. They attack concrete by reacting with the portland cement, causing unnatural expansion which can lead to the early failure of a structure.
Portland cement must conform to____
Normal-weight aggregate must conform to _____ in all concrete.
ASTM C150
ASTM C33
The maximum allowable nominal aggregate size for concrete used in a 6” thick slab is:
2”
(1/3 rule applies from 26.4.2.1(a)(4))
A concrete mix design specifies a water/cement ratio of .045 max. When batches to particular load has a water/cement ratio of .038. What happens to the compressive strength?
The compressive strength will likely be higher than normal
1) Too high of a slump means:
2) Too low of a slump means:
1) The concrete aggregate will segregate.
2) The concrete won’t properly flow to encase rebar and fill formwork.
Portland Cement
Most common cement used.
What is grout?
A mixture of cement and water, either with or without fine aggregate.
What is mortar?
When the aggregate consists of sand-size material only, all less than 1/4” in diameter.
Segregation:
Separation, usually by the coarse aggregate and mortar, caused by improper handling of the concrete or harsh mixes. A well-proportionated mix, in the plastic range of 1-4” slump, resists segregation.
