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Concrete: Red PPT notes
Terms in this set (56)
width; the higher it goes, the less it has to support. Loads transferred through steel/concrete on either side
inventors of concrete
200 BC-100 AD
what division is concrete in?
formed when Portland cement creates a pasted with water that binds with sand and rock to harden
the term used when steel is embedded into the concrete
provides tension strength
what does steel do?
heat of hydration
when concrete cures, it gives off heat and forms bonds that hold the aggregate together
most common standard for Portland cement
American Society for Testing and Materials
establish standard specifications
top finished portion of soil; slope important because of drainage-must slope away from structure
ingredients in concrete (other than Portland cement, water and aggregate) that are added to the mix immediately before or during mixing
water reducing admixtures (becomes thicker and stronger)
REDUCE WATER CONTENT
LOWER WATER-CEMENT RATIO
HIGHER STRENGTH CONCRETE
retarding admixtures (slows down heat)
SLOW THE HEAT OF HYDRATION
KEEP CONCRETE WORKABLE
INCREASES THE HEAT OF HYDRATION
REDUCE THE TIME
superplasticizers (slimy, cures very quickly)
FLOWING CONCRETE IS HIGHLY FLUID
CAN BE PLACED WITH LITTLE VIBRATION
ONLY 30 TO 60 MINUTES
ADDED TO CONCRETE AT THE JOBSITE
corrosion inhibiting admixtures (holds up better in corrosive environments)
cast in place (site cast)
means the concrete is formed and poured on the construction site. The concrete mixture must be transported to the site or mixed at the site
the form that supports the concrete
always associated with cast in place
made from wood, metal and/or plastic
-earth forms: ex, concrete grade beams
put on and take off
-ex, wood formwork used as a mold
create a pattern or desired effect on concrete
chosen by architect or designer
ex; highway underpass w/ Texas shape or bluebonnets
slab on grade
a level surface of concrete that lies directly on the ground.
equal to the minimum yield strength of the bar in ksi (1000 psi)
ex: grade 60 rebar has a minimum yield strength of 60 ksi.
engineers specify grade
fabricated in shop or mill OR on site
Decreased water demand
Reduced heat of hydration
joints that create a physical space within the concrete (isolation/separation)
joints that "score" the concrete - controlling where the crack will occur in the concrete
rubber or vinyl
Joint inserts that are used to form joints in concrete are made of ________.
water to cement
To ensure that the concrete mixture sets up properly the ___________to ______________ ratio must be correct.
a concrete that is readily molded
test is used as a rough measure of the consistency of the concrete.
This test does not measure workability.
test determines whether a concrete has the specified compressive strength. In these tests, concrete specimens are tested at 7 days and at 28 days after they are taken.
live loads (can change if point loads are added)
what type of load is highly subjective?
2. settle properly
3. selected properly
why do most foundations fail
simple excavations which permit direct visual inspection of the actual soil conditions.
spread foundations- transfer the building loads directly to the sufficient soil area.
either piles or caissons- penetrate through upper layers on unstable soil to transfer the load to the strong soil or rock deeper within the earth.
Foundations must be designed to resist water penetration.
Foundations require watertight barriers and drainage systems.
Transfer the structural loads from a building safely into the ground
columns, beams, walls, slabs
cast in place structural elements include concrete...
transfer building loads (through building structure down to foundation)
what is the purpose of cast in place structural elements?
the concrete is cast with a hollow duct or sleeve to encase the steel. AFTER the concrete has cured, the steel is tensioned and anchored into place.
applying a force to the steel BEFORE the concrete is poured.
one way system
-Slab supported on TWO sides by beams or load-bearing walls
-Main beams on one axis
-Slab spans distance between main beams
two way system
-Reinforcing running in TWO perpendicular directions
-Drop panel and/or capital
tilt up construction (tilt wall)
-casting a WALL panel in a horizontal position and then tilting it to it final vertical position.
-Usually, these panels are solid, reinforced slabs five to eight inches thick.
-They have to be able to attach to the crane
structural (carries loads to foundation)
Is Tilt up construction considered structural or architectural ?
precast concrete elements
means the concrete is formed and cured in a factory, transported to the construction site and erected as rigid components.
Precast in made with type III Portland cement and the concrete is steam cured. Steam accelerates the ____________________ of the concrete and provides for full hydration.
At a precasting plant, elements can be made in a __________________ length of time.
Are the following structural or architectural ?
structural (accommodating the span supporting both ends)
Are precast planks and/or slabs considered structural or architectural?
Synthetic fiber slab reinforcement
Used primarily in precast to prevent cracking
Not a substitute for wire reinforcement
-added to concrete to make it more flexible/bendable (decorative elements that are typically brittle)
Glass fiber reinforced concrete (GFRC)
-Same concept as fiberglass; however glass fiber is embedded in Portland cement and sand (concrete mixture)
-Used for ornamental structures, wall cladding, and soffits
-allows for movement in concrete; expensive
the term used to describe the strength of the soil.
-strengths are in pounds per square foot or Tons per square foot
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