G7 - LT #1 Conc. Finishing Flashcards
What stages of finishing is an edger used and why?
1) After bull floating, pushes large aggregates AWAY from the surface
2) Rounds over
What is the purpose of hand floating and bull floating?
Pushes large aggregates down & allows bleed water to escape.
Is a divider tool deep enough for control joints?
No
When is the placing of the concrete completed?
After floating process
Why should bleed water be allowed to evaporate first?
1) Not to dilute the concrete
2) causes dusting and crazing if you do not
How to broom finish?
Float, edge, trowel, broom and edge again
When are screeds removed from the concrete?
After strike-off
What is the purpose of a screed?
Elevated guide for strike off
How is the top of a concrete wall finished?
Remove the cleats from formwork and then float
What is the purpose of kneed boards?
Distributes weight evenly
What tool is used to transfer flexible patterns?
Tamper
5 precautions to consider when finishing a concrete slab with a power trowel?
1) Concrete is flat & level
2) Will bear the pressure
3) bleed water is evaporated
4) cover entire surface uniformly
5) allow concrete to harden between passes
How is the movement of a power trowel controlled?
1) Increase RPM to engage blade rotation
2) Push down on handles to move right & lift up to move left
What is a burnished surface?
Mirror-like finish, made by making many passes with a power trowel at high speeds and a steep angle.
What are two different types of blades used with power trowels?
Float & Trowel
What safety precautions must be taken with concrete treatments?
Read the SDS Safety Data Sheet
What are the environmental concerns associated with concrete treatments?
Streams & groundwater
Describe how sealers and hardeners also act as a curing compound.
Coat the surface to stop moisture.
How is exposed aggregate wall surface created?
Uniform coat of retardant, painted on the forming material, don’t slide concrete surface of coated form & strip carefully
What is the difference between dampproofing & waterproofing materials?
Moisture vs. hydrostatic pressure
How is a suspended concrete slab waterproofed?
Membrane roofing
The top of a concrete wall that is left exposed must be finished with:
A steel trowel
How can chamfer on concrete be made?
Chamfer strip in formwork or an edging tool
Should well-proportioned concrete have excessive bleed water?
No
What is concrete flatwork?
A slab that is suspended or placed on grade. Also surfaces of concrete landing and treads in concrete stairs.
When does the finishing process of concrete start?
After bleeding water evaporates & carpenter can put weight on it with knee boards
Can you add water to a concrete mix to ease placement?
No
Is rebar at the bottom of a form or on ground effective?
No
What is the purpose of screeding?
Levels off the concrete to the elevation set by the screeds?
When is floating done
After concrete has been placed & screeded to level
How are larger areas floated?
Bull float for larger areas
Can a power trowel be used if bleed water is still remaining?
A power trowel should not be used until the bleed water has evaporated
How does crazing occur?
Floating during bleed water period,changing the w:c ratio, surface cures at a different rate, dusting also occurs
A large flat steel trowel is used first, is placed flat or on a steep angle?
Flat
The second finishing, a smaller trowel is used, is it placed flat or on a steep angle?
Steep angle, allowing more pressure
On exterior concrete walks and driveways, what sort of finish is needed?
A broom trowel, to prevent slips
When is a broom trowel done?
After a single steel trowel is done
When is an edger used?
Before each troweling and as the last step of a broom finish
When is a fresno used?
Used to flatten out the ridges left by the bull float
For flexible stamps, what tool is necessary?
A tamping tool
Power trowel can be used in addition to or as an alternative to
The bull float, Fresno & steel trowel
With a power trowel, which 2 blades are common?
Floats and trowel blades
A float blade on a power trowel does what?
Final leveling of the concrete surface. Blade typically 10”, kept flat initially. Run at 1/2 to 3/4 speed.
What is crossover floating?
The second pass on a power trowel, the blades are tilted slightly and the engine is run at 3/4 speed
Allows finisher to reach areas that were hard to access when travelling the first direction and helps level the slab
On a power trowel, what does a trowel blade do?
Similar to the blade of a hand trowel, typically 8” wide
each pass increases the density of the slab surface, with enough passes the op. can burnish the surface to a mirror-like finish
The handles on a power trowel work how?
Lifting handing moves to the left, lowering moves to the right
What is a curing compound?
Membrane curing compound consists of chemicals and waxes that are sprayed, brushed, or rolled on.
Protect from early drying, in hot windy weather.
What is a sealer?
Sealers are chemicals that the seal of the surface of concrete, prevent formation of dust on a worn concrete surface.
What is a chemical hardener?
Provide hard-wearing concrete surface and prevent dusting. Also, act as sealers.
Metallic or aggregate hardeners?
Used in areas where very heavy wear is, dry the top of concrete as it is being finished. made from iron, steel, or hard mineral aggregates
Describe exposing aggregates
Vertical forms can be treated with chemicals that prevent the cement paste from setting on the surface next to the.
Exposing chemicals are sprayed on slabs to retard the setting of the cement paste
What is a bond breaker?
These chemicals are used to break the bond between layers of concrete, such as those used to tilt-up construction where multiple layers of concrete are cast one on top of the other.
What are bonding agents?
Epoxies and adhesives are used to create a good bond between fresh concrete placed over old concrete
What is dampproofing?
Below grade foundations should be coated on the outside with a dampproofing agent
What is waterproofing?
Concrete foundations subject to hydrostatic pressure must be waterproofed.
How are pigments added?
During concrete mixing or may be shaken onto the surface of the concrete when the slab is being finished
