G-7 Place and Finish Concrete Flashcards
Describe concrete finishing
top surfaces of cast in place concrete must be finished to a smooth, uniform surface for appearance and durability
Wall finish
after concrete has been vibrated into place the surface of top of wall is finished level strip or chamfer strip set elevation of top of wall. then hand float is used to finish
Architectural concrete finish
- that of which is left exposed to view
- this is final finish of building and must be finished with steel trowel
- wait for bleed water to evaporate and trowel with steel trowel
Flatwork finishing
- can be finished with simple hand tools or power equipment
- starts when bleed water in evaporated
Vibration
- slabs must be vibrated like walls or columns
- ## edges must be well vibed to reduce bug holes
screeding or striking off
- levels the survace of concrete to elevation set by screeds
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floating
- after concrete has been placed and screeded level
- the surface is floated
- ## this pushes any large aggregate below the surface of concrete slab
Bull float
used for large areas very large wooden or metal float with long handle attached
Hand floats and kneeboards
tops of walls and small concrete slabs can be done with hand float
- if hand floating larger job kneeboards are used
wooden hand floats must be made of?
- edge grain cedar with pine or furr handle
Broom finish
- provides non-skid finish and should be used when slipping might be a hazard
- broom should have smooth stiff bristles
- steel trowel is done followed immediately by broom lightly dragged across surface
edger
used to round corners of the surface of slab .
- done after concrete is floated to remove large aggregates away from forms.
Steel trowel
12- 16 inches
- longer legnths needed when less pressure is required short is needed hen more pressure is required
Fresno
divider
used to create decretive divisions in walkways an patios
- used to create control joints joints
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Stamped concrete
uses manufactured stamps that are set into the partially set surface of concrete.
- done after bleed water is evaporated
- surface of slab is covered with fine powdered release agent that is designed to allow the stamps to be removed cleanly from the concrete
Power trowel
used for finishing concrete slabs
- have four spinning concrete trowel blades that spin clockwise
walk behind power trowels
- size determined by diameter of circle it makes
- ranges from 24inces to 48 inches in diameter
riding power trowels
for large projects
- two or three separate trowels are assembled into one
- operator rides on top and is able to control movement and rake of blades
Float blade
- used for final levelling of concrete surface
- usually 10” wide
- made from thick gauge steel
blades are kept flat for initial pass
second pass kept at 90° (crossover floating)
Trowel blades
- typically 8” wide
- made from thin steel
- each pass will increase density of the slab surface
Using power trowel
- make sure concrete is levelled properly
- should support foot pressure before power trowel
- make sure bleed water has evaporated
- move over entire surface evenly
- allow concrete to harden between passes with trowel
Curing compounds
- membrane - curing compounds consist of chemicals and waxes that are sprayed, brushed or rolled on. protect surface of the concrete from early drying
Sealers
chemicals that seal the surface of concrete and prevent the formation of dust on a worn concrete surface
chemical hardeners
provides a hard-wearing concrete surface and prevent dusting of the concrete
Metallic or aggregate hardeners
- used in ares where heavy wear is expected
- (steel mills and factories)
- applied dry to the top of the concrete as it is being finished
Bond breakers
- chemicals used to break bond between layers of concrete
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bonding agents
epoxies and adhesives are used to create a good bond between fresh concrete placed over old concrete