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Construction Materials Exam #2
Terms in this set (43)
What are the four components of concrete?
3) Fine Aggregate
4) Coarse Aggregate
cement in between bricks in walls
stuff in between tiles
Supplementary cementitious materials
when added to PCC, they have cementitious characteristics. can reduce PCC by 20% and maintain the same strength.
when you can see the air pockets in concrete, bad
Advantages of Reducing Water Content
1) Increased strength
2) Lower permeability
3) Increased weathering resistance
4) Better concrete bond
5) Reduced drying shrinkage and cracking
6) Less volume change from wetting to drying
the property of freshly mixed concrete that determines its working characteristics (i.e. the ease it can be mixed, placed, compacted and finished.)
Factors Affecting Workability
1) Method and duration of transportation
2) Quantity and characteristics of cementing materials
3) Concrete consistency (slump)
4) Aggregate grading, shape and surface texture
5) % entrained air
6) Water content
7) Concrete and ambient air temperature
the chemical reaction between cement and water in which new compounds with strength producing properties are formed
Heat of Hydration
the heat given off during the chemical reaction as the cement hydrates
maintenance of a satisfactory moisture content and temperature in concrete for a suitable period of time immediately following placing and finishing so that the desired properties may develop. (time, temperature, moisture)
the measured maximum resistance of a concrete or mortar specimen to an axial load, usually expressed in psi at 28 days.
first patented in 1824, named after the natural limestone quarried on the Isle of Portland in the English Channel
Portland Cement Materials
Traditional Manufacture of Portland Cement Steps
1) Stone is first reduced to 125 mm then to 20 mm and stored.
2) Raw materials are ground to powder and blended
3) Burning changes raw mix chemically into cement clinker
4) Clinker with gypsum is ground into portland cement and shipped
How does the w/c ratio affect the mix?
It affects the strength and workability of the concrete. High w/c ratio means less strength. Low w/c ratio means less workability.
3 properties of a good concrete mix
Four functions of admixtures in concrete
1) Create specific features
2) Economical reasons
3) Overcome emergencies
4) Ensure quality
6 Types of Admixtures
1) Air Entrainers
2) Water Reducers
Advantages of Air-entraining admixtures
1) lowers surface tension of water, enhances bubbles
2) impedes bubble coalescence
3) anchors bubbles to cement and aggregate particles
4) stabilizes bubbles
5) can lower water content and still be workable
Water Reducing admixtures
allow a reduction in the amount of mixing water (5%), while retaining same workability, which results in a higher-strength concrete.
produces flowing concrete with high slump, reduces bleeding, reduces slump loss
Speeds up the setting process, used in cold places
Slows down the setting process, used in warm places
most common, by-product of burning coal. makes concrete more workable
made from iron blast furnace slag. has rough and angular shape.
byproduct of silicon metal production. produces high strength concrete.
has no cementitious value by itself, but does when in fine form with water.
used to slow down the rate of hydration.
Type I Portland Cement
Normal. general concrete work (floors, pavements, reinforced concrete structures)
Type II Portland Cement
Moderate Sulfate Resistance. (large piers, retaining walls)
Type III Portland Cement
High Early Strength. (used for fast track construction, in cold weather)
Type IV Portland Cement
Low Heat of Hydration. (large dams)
Type V Portland Cement
High Sulfate Resistance. (protection from severe sulfate exposure)
ability of cement to retain its volume after setting
Specific Gravity of Portland Cement
Fineness of Portland Cement
finer material=faster strength development, greater initial heat of hydration
Steps in Concrete Mix Design
1) Strength Requirements
2) Water-Cement Ratio Requirements
3) Coarse Aggregate Requirements*
4) Air Entrainment Requirements*
5) Workability Requirements
6) Water Content Requirements*
7) Cementing Materials Content Requirements*
8) Admixture Requirements
9) Fine Aggregate Requirements*
10) Moisture Correction*
Load Control Test
put weights on concrete cylinder, once peak stress is reached, concrete will be crushed. Can't take data after that
Modulus of Elasticity
needs to be known to see if it deforms. measure of the stiffness of a material. applies to very low strain loads, when behavior is almost linear.
deformation resulting from constant loading.
too much water in concrete, flows rapidly, big chunks end up together.
lumps of limestone and clay grounded to produce admixtures
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