Concrete Flashcards

1
Q

Framework

A

oil/glue/plastic on plywood + wood framing, steel/prefab, FRP, plastic, foam

slip forming: not waiting for complete cure, wait 6-12”/hour, usu for v big jobs

flying forms: reused on floor after floor

insulating (ICEs), polystyrene, remain in place, waterproofing on earth side, gyp on inside, v low acoustical and air flow

costs the most for concrete constr, bc of labor

tolerance: usu .25” out of plumb in 10’

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2
Q

Reinforcement

A

for req added tensile strength, bars or wire fabric

bar number increases w bar size in 1/8” increments

is deformed to increase bonding

markings indicate grade, source mill, size, type

grades 40/50/60/75 are yeild strengths in kips/in2

types: axle, rail, billet

min distance to surface, min dist to each other specified by SE, needs to allow aggregate to pass through

can be reg steel, galv steel, SS, epoxy coated

GFRP: glass fiber reinforced polymer, where no metal can be used, can be used for primary structure

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3
Q

Cement

A

all is pretty much Portland now = lime (CaOH, CaOx, CaCOx), silica, FeOx, AlOx

type I: normal, type II: modest sulfate resistance, heat controlled (dams), type III: high early strength, type IV: not used, low heat, type V: sulface resisting for high alkaline exposure

excess water creates pores that decrease compressive strength, should be 0.35-0.40 per 1, can create laitance, low strength, chalky pools, must be removed

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4
Q

Aggregates

A

fines: less than no.4 sieve (4 openings/inch), coarse: 3/4-1”, good to have a variety to air pockets not too large

should be 65-70% of volume

can use clay/shale/slag for lt.wt. concrete, pumice/cinders for insulating concrete

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5
Q

Curing

A

design strength = compression at 28 days

12,000 psi is high strength, 2000-4000 psi is normal

give it ideal temp/hydration for 7 days-2 weeks (longer if in critical/weird places)

slump test: consistency and water ratio

cylinder test: 7 and 28 day compression test

core cylinder test: taken from structure directly

kelly ball test: ball dropped, measure how much it sinks

impact hammer test: nondestructive hardness test

k-slump: floating scale measures liquidity

CaCl moisture dome test, weighed after 60-72 hrs

hygrometer test/relative humidity

polyethylene sheet test, tape it down, does it bubble?

mat test, same but w pc of impermeable flooring

electrical impedence test: conductance tested

litmus or titration to test for pH, alkalinity is bad for conc, because is dissolves cement, emulsifies adhesives, can avoid by using better aggregates/SCMs

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6
Q

Admixtures

A

air entraining agent: more workability, more durability bc resists freeze/thaw better, keeps things mixed

accelerator: speeds up hydration reaction, good for cold weather
retarder: slows hydration, lessens heat, good for big pours
waterproofing: reduces water perm

corrosion or shrinkage resistance

superplasticizer: increases workability wo adding water, makes higher strength conc.

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7
Q

SCMs

A

supplementary cemetitious materials

fly ash: improves workability, from coal furnaces

GGBFs: ground granulated blast furnace slag, is stronger in long run, better to work, durable

silica fume: from silica/metal furnace, reduces permeability

pozzolan: volcanic ash, might be deposited, reduces permeability, increases strength

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8
Q

Special concrete types

A

autoclave aerated concrete/AAC: precast with Al added, steam cooked, v lightweight, v airtight, but needs waterproofing, not strong

self consolidating concrete/SCC: no vibration needed, superplasticizer used, less labor, and earlier high strength

carbon fiber concrete: expoxy coated carbon fiber mesh instead of steel mesh reinf., thinner, lighter precast panels, less buffer to surface, so stronger despite thinness

ultra high performance/UHPC: high strength, low perm, v durable, 17-25000 psi, cement and silica fume and plasticizer plus alkali resistant glass or steel fibers, usually factory made, often cladding, can be very thin

poured gypsum deck

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9
Q

Finishes

A

rough: plywood face shows, smooth: from hardboard, metal, smoother wood

form liner: smooth wood, metal, harboard, thin brick

sandblasted, scrubbed, acid wash, water jet: exposes aggregate

brush hammered: looks like meat tenderized

grinding: looks like terrazo
applied: stucco or plaster

smooth rubbed: carborundum abrasive used

grout cleaned: skim coat of grout to even out

strike off: use straight edge to cut

float: bring cement to top w vibration

light steel trowel: done after floating, compacts, smooths

hard steel trowel: even more smooth

superfloat: where wheels need to be fast

broom finish: swept over top to increase grip

stamped: embossed

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10
Q

Concrete joints

A

control jts: 1/4” depth, saw cut or forms

construction jts: between pours, need waterstops

expansion jts: allows for thermal movement

isolation: prevents vibration conduction

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11
Q

Prestressed concrete

A

pretensioning: mostly only for precast conc., where tendons are stressed, conc is poured, tension released as hardens, cambers, then load on makes it flat again

post tensioning: pour, stress as it hardens, keep under stress, load

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