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Concrete Flatwork Tech and Flatwork
Finisher.
finishing foreman - ✅(Ch. 1, #1) It is important that the _______ _______ read and understand project specifications
100 - ✅(Ch. 1, #2) If the crew can place and finish 100yd^3 (m^3) of concrete per hour, the producer's rate should be about ____ yd^3(m^3) per hour.
False (sold by volume) - ✅(Ch 1, #3) True or False: Concrete is sold by the ton.
pump, place, and finish - ✅(Ch. 1, #4) Delays in discharging concrete trucks can result in the concrete being hard to:
A) 407.41; B) 297 - ✅(Ch. 1, #5)
A) Inch/Pound: For a concrete floor slab that is 6 in. thick, 200ft long, and 100 ft wide you should order ____ yd^3 of concrete, assuming a 10% waste factor.
B) Metric: For a concrete floor slab that is 150 mm thick, 60 m long, and 30 m wide you should order ____ m^3 of concrete, assuming a 10% waste factor.
as one truck is finishing, the other is ready to unload concrete - ✅(Ch. 1, #6) When there is room for two concrete trucks ready to discharge into a pump hopper, placement is faster because:
1.5 - ✅(Ch. 1, #7) Concrete from a ready mix truck must be completely discharged within ____ hours after water has been added at the plant.
batch ticket - ✅(Ch. 1, #8) You can tell when water was added to the concrete truck by looking at the:
15 minutes - ✅(Ch. 1, #9) When concrete for a slab placement will be discharged from the truck chute, truck arrivals should usually be spaced about:
True - ✅(Ch. 1, #10) True or False: When finishers get behind because the concrete is setting faster than expected and the placing crew is also shorthanded, one solution is slowing the concrete delivery rate to match worker output.
False (Standard is to order 10% to 15% more than measured volume for small orders and 5 to 10% more than measured volume for large orders to account for subgrade settlement, uneven subgrade, spillage, and waste.) - ✅(Ch. 1, #11) True or False: In deciding how much concrete to order for a floor placement, you should calculate the number of cubic yards (cubic meters) needed to fill the forms, then order two or three cubic yards (cubic meters) less so you don't waste concrete that is not needed.
preconstruction conference - ✅(Ch. 1, #12) The question "What finisher or finishers can request the addition of water to the concrete truck on site?" Should be answered at the _________ __________.
True - ✅(Ch. 2, #1) True or False: Concrete made with portland cement will set and harden while underwater.
Type I - ✅(Ch. 2, #2) If a concrete slab on ground won't be exposed to sulfates, the cement used is most likely to be:
portland - ✅(Ch. 2, #3) Fly ash may be added to concrete from a fly ash silo at the batch plant or from a silo containing a _______ cement.
0.75 to 1.5 in. (19 to 38 mm.) - ✅(Ch. 2, #4) Most concrete used in slabs on ground has course aggregate with a maximum size of:
True - ✅(Ch. 2, #5) True or False: Sand for concrete used in slabs on ground is easier to finish when it has close to the largest allowable amount of material passing the No. 50 and No. 100 sieves.
False (Too many small particles will increase the amount of water needed to make the concrete workable.) - ✅(Ch. 2, #6) True or False: Increasing the amount of sand in a concrete usually decreases the amount of water needed to make the concrete workable.
an air-entraining agent - ✅(Ch. 2, #7) All concrete that will be subject to freezing when moist or be exposed to deicing salts should contain:
measuring down from a straightedge spanning between the side forms - ✅(Ch. 3, #4) Before concreting, workers should check the elevation of the subbase by:
False (If the surface is too low, it will be thicker and require more concrete than anticipated) - ✅(Ch. 3, #5) If the surface for a subbase for a concrete slab on ground is too low, the slab is likely to be too thin.
Checkerboard (recommended methods include adjacent and alternate lanes) - ✅(Ch. 3, #6) Which one of the placing sequences for casting slabs-on-ground is not recommended?
form setting and screeding - ✅(Ch. 3, #7) Which has the greatest effect on floor levelness?
False (There should be no holes in the sheet, as these will expose the underside of the slab to moisture that can seep through any cracks or joints.) - ✅(Ch. 3, #8) True or False: When concrete will be placed directly on a vapor retarder, finishers should use a margin trowel to punch holes in the vapor retarder and thus decrease waiting time before the concrete can be finished.
placing a 3-in. (75mm) thick layer of compactible manufactured sand (containing rock dust) on the vapor retarder before concrete placement - ✅(Ch. 3, #9) When specifications don't require the concrete slab to be in direct contact with the vapor retarder, the preferred method for reducing potential problems caused by slab curling is:
keeping any slab cracks tightly closed - ✅(Ch. 3, #10) The primary function of welded wire reinforcement in slabs-on-ground that are considered unreinforced is:
Reinforcing steel be discontinued (cut) so it doesn't pass through the joint, or that every other bar or wire be discontinued (cut) so only half the steel passes through the joint. - ✅(Ch. 3, #11) Instructions for drawings for slabs-on-ground may require that:
True - ✅(Ch. 3, #12) True or False: Reinforcing steel should be located at or above mid-depth of slabs on ground so cracks will remain tightly closed at the surface.
steel dowels - ✅(Ch. 3, #13) Load transfer at construction joints can be provided by smooth _____ ______ or other types of load transfer devices.
6 - ✅(Ch. 3, #14) Keyed construction joints are not recommended for slabs subject to heavy wheel traffic or for slabs less than ____ in. thick.
floor flatness - ✅(Ch. 4, #1) Measuring the gap under a 10-ft straightedge is one way of determining:
the location under the 10-ft straightedge that is between the two high spots where the straightedge is resting. - ✅(Ch. 4, #2) The gap under a straightedge should be measured at:
floor flatness and levelness - ✅(Ch. 4, #3) The F-number system is one way of determining:
True - ✅(Ch. 4, #4) True or False: F(f) numbers are indicators of floor surface smoothness or flatness.
True - ✅(Ch. 4, #5) True or False: F(l) numbers are indicators of levelness or tilt of the floor surface.
Floating, restraightening, troweling - ✅(Ch. 4, #6) Which finishing operations affect floor flatness?
flat but not level - ✅(Ch. 4, #7) A floor with an F(f) value of 48 and an F(l) value of 16 is:
a lot of finishing effort needed to get a high F(f) number floor - ✅(Ch. 4, #8) A 3-in. (75mm)-slump concrete that sets very fast is most likely to result in:
24; 72 - ✅(Ch. 4, #9) F-number testing should preferably be done within ____ hours after concrete placement, but never later than ____ hours after concrete placement.
True - ✅(Ch. 4, #10) True or False: A floor with an F(f) number of 40 is twice as flat as a floor with an F(f) number of 20.
False (Measurements after 72 hours may reflect other influences, such as slab curling, that affect flatness or levelness but are beyond the finisher's control.) - ✅(Ch. 4, #11) True or False: Floor flatness measurements taken more than 72 hours after concrete placement are the best measure of the finishers' skills.
allowing enough space near the boom pump so as one truck is finishing the other is ready to unload concrete - ✅(Ch. 5, #10) When using a boom pump to place concrete for a slab on ground you can minimize delays by:
short handled, square-ended shovels - ✅(Ch. 6, #1) Tools commonly used for hand spreading concrete in slabs include:
20 - ✅(Ch. 6, #2) Bull floats are used after screeding when the specified F-number floor flatness is ____ or less.
False (bull floating is done before bleed water comes to the surface) - ✅(Ch. 6, #3) True or False: Bull floating must be done after all of the bleed water has evaporated from the surface.
Wood - ✅(Ch. 6, #4) _____ bull floats are less likely to seal the surface.
air-entrained; lightweight - ✅(Ch. 6, #5) Magnesium bull floats are recommended for use on ___________ concrete and ___________ concrete.
control the tilt of the head to keep the blade as flat as possible - ✅(Ch. 6, #6) When using a magnesium bull float, sealing the concrete surface is less likely if you:
True - ✅(Ch. 6, #7) True or False: Highway straightedges are used instead of bull floats when high F(f) numbers for floors are specified.
Made of wood or magnesium; used for the same purpose as bull floats; particularly useful near side forms when a long-handled bull float is hard to manipulate around obstructions or penetrations - ✅(Ch. 6, #8) Darbies are long, hand-held floats that are:
rounded; exterior - ✅(Ch. 6, #9) Edgers are used to make neat, ______ edges primarily on _________ concrete.
cut grooves to a depth of 1/4 the slab thickness for contraction joints in exterior concrete - ✅(Ch. 6, #10) Groovers are used primarily to:
are best for non-air-entrained concrete or high-slump concrete - ✅(Ch. 6, #11) Wood hand floats:
False (larger trowels are used for the first troweling to spread the force out over a larger area. Once the surface becomes harder, subsequent trowelings are done with smaller trowels to increase pressure on the surface.) - ✅(Ch. 6, #12) True or False: Hand trowels used for the first troweling should be short and narrow to increase the pressure on the concrete surface.
for troweling slabs such as sidewalks that do not require a hard-trowel finish - ✅(Ch. 6, #13) Fresnos are long-handled trowels with blades 24 to 48 in. (600 to 1200 mm) long that are used:
True - ✅(Ch. 6, #14) True or False: Float blades for power troweling machines are wider than trowel blades and turned up on the edges to prevent them from digging into the surface.
the reduced pan-to-concrete contact cuts drag and eases handling - ✅(Ch. 6, #15) Some float pans have a bottom profile that varies from flat to slightly curved upward. When curved pans are used on walk-behind finishing machines:
36 - ✅(Ch. 6, #16) A ___ in diameter pan is the largest size commonly used on walk-behind machines because the finisher can guide the machine more easily than with larger pans.
True - ✅(Ch. 6, #17) True or False: Power trowels can be used for floating or troweling.
all - ✅(Ch. 6, #18) When one bent or broken blade on a double- or triple-rotor troweling machine is replaced _____ blades should be replaced.
temporary pipes or rails; edge forms; the top of the edge of adjacent hardened concrete - ✅(Ch. 7, #1) Rigid supports for a straightedge used to strike off concrete can be:
Make sure there is always enough concrete ahead of the straightedge. - ✅(Ch. 7, #2) How can workers avoid low spots when using hand-operated straightedges?
wet screeds - ✅(Ch. 7, #3) Hand-held vibrating screeds are often useful when striking off concrete with __________ _________.
True - ✅(Ch. 7, #15) True or False: Edging and jointing is not required on most floors and should not be done unless specified.
is occasionally required for interior flatwork - ✅(Ch. 7, #16) A fine broom finish:
Embed large aggregate particles beneath the surface mortar layer; remove slight humps to produce a plane, level surface; compact and further consolidate the surface in preparation for other finishing - ✅(Ch. 7, #17) After the waiting period, floating is done to:
bleed water; 1/4 - ✅(Ch. 7, #18) Concrete is ready for floating when the ________ ________ sheen is gone and the finisher can walk on the slab leaving only about a ____ inch deep footprint.
True - ✅(Ch. 7, #19) True or False: While machine floating, if the machine digs in or disrupts the level of the surface, stop floating and wait until the concrete surface is stiffer.
False (If concrete is setting slowly, floating should be done as late as possible(when a finisher's footprint is barely perceptible)). - ✅(Ch. 7, #20) True or False: If concrete is setting slowly, floating should be done when the finisher's footprint is 1/2 in. or more.
floating; floated - ✅(Ch. 7, #21) Troweling follows immediately after _________, and no troweling should ever be done unless the surface has first been _________.
True - ✅(Ch. 7, #22) True or False: When hand finishing, finishers usually float and then steel trowel an area before moving their knee boards.
tilting the trowel blade too much or too soon - ✅(Ch. 7, #23) Chatter or washboard marks on a finished surface are caused by:
perpendicular - ✅(Ch. 7, #24) The direction of the first machine floating pass should be __________ to the direction of the last finishing procedure.
creates waves that grow larger with repeated passes of the machine. - ✅(Ch. 7, #25) Machine floating or troweling of slabs is typically done in two directions-- parallel and perpendicular to the side forms. Floating or troweling in only one direction:
False (a hard, sharp turn actually creates these depressions, which have to be filled in by further float passes) - ✅(Ch. 7, #26) True or False: On soft concrete, a hard, sharp turn with the rider should be used to fill depressions that the finisher can see.
face - ✅(Ch. 7, #27) On stiffer concrete, a forward-turn, forward-pass combination on a rider allows the finisher to always ______ the concrete being floated or troweled.
True - ✅(Ch. 7, #28) True or False: Typically four float passes and four or more trowel passes are used to produce the desired final finish for a floor.
False (pan floats improve flatness, increasing floor flatness numbers by 10-15 points when used) - ✅(Ch. 7, #29) True or False: Pan floats used on either walk-behind or riding machines improve levelness but not flatness.
Throttle down the machine to avoid moving too much mortar. - ✅(Ch. 7, #30) If you're making float passes with a riding machine and running at full speed, what should you do when you see that some of the concrete ahead is still wet?
dry; set - ✅(Ch. 7, #31) When only parts of a concrete floor are exposed to the sun or to wind coming through a door opening, those parts will often _____ and _____ faster.
backward; edge form - ✅(Ch. 7, #32) If concrete at the edges is low during machine floating, a __________ pass with the float blades or pan over the ______ will bring more concrete to the edges.
apply a slight upward pressure on the handle - ✅(Ch. 7, #33) To move left with a walk-behind troweling machine:
parallel; 2 to 3 - ✅(Ch. 7, #34) Where a temporary screed is moved, two different placements are sometimes made adjacent to each other. When concrete is softer on one side of the screed's former location, the walk-behind machine should be run _________ to the seam where the two concretes come together, with the blades overlapping the seam by about ____ to ____ inches.
larger; smaller - ✅(Ch. 7, #35) When hand floating, float and trowel blades may be of different sizes, but finishers should always start with the ________ size and then move to the _________ size.
ravel; random cracking - ✅(Ch. 8, #13) If contraction joints are sawed too soon with a wet-cut saw, the edges of the joint may _______ but if the joints are sawed too late _________ ________ may occur.
3rd; 4th; intermediate - ✅(Ch. 8, #14) When temperatures are high during the day and low at night, it's sometimes necessary to saw every _____ or ______ joint before sawing the __________ joints.
True - ✅(Ch. 8, #15) True or False: During hot weather, it may be possible to saw contraction joints with wet-cut saws as early as 4 hours after finishing is complete.
1 hour; 4 hours - ✅(Ch. 8, #16) Early-entry, dry-cut saws cut the waiting period before sawing to as little as ___ ______ in hot weather and about ___ _____ in cold weather.
usually cut to a maximum depth of 1.25 inches; should not ride up over hard or large coarse aggregate; have a skid plate that helps prevent raveling (spalling) at the cut edges - ✅(Ch. 8, #17) Early-entry, dry-cut saws:
True - ✅(Ch. 8, #18) True or False: Construction joints can be made to act as isolation joints or contraction joints.
True - ✅(Ch. 8, #19) True or False: To improve load transfer at construction joints, plate, round, or square dowels have been used.
parallel; perpendicular - ✅(Ch. 8, #20) Plate dowels in plastic sleeves and square dowels cushioned on the vertical sides by a compressible material permit movement ___________ and ___________ to the construction joint.
keeping the concrete moist and at a high enough temperature for cement to hydrate fast enough - ✅(Ch. 9, #1) Concrete curing refers to:
7 days - ✅(Ch. 9, #2) When the temperature is above 40 degrees F (4 degrees C), unless specifications direct otherwise, continuous moist curing should be maintained for:
evaporation retarders; fog sprays - ✅(Ch. 9, #3) In hot weather slab curing may have to start after placing but before finishing. What two methods can be used for this?
True - ✅(Ch. 9, #4) True or False: Craze cracking is likely if concrete dries too soon after finishing.
True - ✅(Ch. 9, #5) True or False: Curing by ponding water on the surface of a slab is practical only for slabs without joints and where dams can be built to prevent flooding of the base course.
may cause discoloration of the concrete surface; should be weighted to stay in contact with the concrete surface; are slippery when wet and may cause slip-and-fall accidents - ✅(Ch. 9, #6) When used to sure concrete, clear plastic sheets:
may cause discoloration of the concrete surface; should be weighted to stay in contact with the concrete surface; are slippery when wet and may cause slip-and-fall accidents - ✅(Ch. 9, #6) When used to cure concrete, clear plastic sheets:
True - ✅(Ch. 9, #8) True or False: A drying period following curing increases resistance to damage caused by freezing and thawing. Curing compounds should not be used on exterior concrete placed during the fall in cold-winter areas because they may not wear off in time to let the concrete dry.
crusting; early cracking - ✅(Ch. 9, #9) In hot weather, finishing as fast as possible and protecting against moisture loss will help prevent _________ and _______ ___________.
occur when the slab surface is drying faster than the bleedwater is rising to the surface - ✅(Ch. 9, #10) Plastic shrinkage cracks:
dampening the subgrade and forms without leaving puddles of water; spraying evaporation retarders (reducers) on the surface immediately after screeding; using fog sprayers to increase the relative humidity above the slab surface - ✅(Ch. 9, #11) Some ways of minimizing plastic shrinkage cracking include
False (Using them may increase the possibility of surface crusting and plastic shrinkage cracking)
- ✅(Ch. 9, #12) True or False: Retarding admixtures used in hot-weather concrete reduce the possibility of surface crusting.
(Ch. 10, #3) True or False: For a floor that will be hard-troweled, if the concrete bleeds too much and delays finishing, you should switch to air-entrained concrete. - ✅False (switching to air- entrained for this reason is not a good tactic. Entrained air slows the bleeding rate and increases the likelihood of blistering or delamination.)
(Ch. 10, #3) True or False: For a floor that will be hard-troweled, if the concrete bleeds too much and delays finishing, you should switch to air-entrained concrete. - ✅False (switching to air- entrained for this reason is not a good tactic. Entrained air slows the bleeding rate and increases the likelihood of blistering or delamination.)
True - ✅(Ch. 10, #5) True or False: Slow setting increases the "window of finishability."
open; rain - ✅(Ch. 10, #6) Slow setting increases the risk that an unset ________ surface could be damaged by _______.
prolonged cold weather when protection is not provided to keep the concrete warm - ✅(Ch. 10, #7) Slow setting may be caused by:
crusting - ✅(Ch. 10, #8) When placing concrete in cold weather, heating the subgrade and keeping the as-delivered concrete as close as possible to the specified minimum temperature can help to prevent ___________.
True - ✅(Ch. 10, #9) True or False: An admixture that reduces bleeding while retarding setting will aggravate crusting problems.
bleed water; air bubbles - ✅(Ch. 10, #10) Blisters form when _________ _________ or ________ ___________ are trapped under a troweled surface.
keep float blades flat and delay troweling as long as possible - ✅(Ch. 10, #11) To minimize chances of surface blisters forming during floor finishing:
flatten; wood - ✅(Ch. 10, #12) If blisters do form, __________ the trowel blades or reopen the surface with a ______ float and delay further finishing for as long as possible.
True - ✅(Ch. 10, #13) True or False: Delaminations are caused by a separation between the surface layer and the underlying concrete, but the separated areas are larger than blisters and the depth of the separation may be as much as 2 inches.
air-entrained - ✅(Ch. 10, #14) Delaminations are especially likely to occur when ________________ concrete is finished with multiple machine passes with the trowel blades.
misting; evaporation retarder - ✅(Ch. 10, #15) In deciding when to start the troweling passes to avoid delaminations: If you can close up the surface without ___________ it with __________ __________, it's too soon to start troweling.
False (Delaying final troweling until the surface sets may reduce floor flatness to F-number values lower than those specified) - ✅(Ch. 10, #16) True or False: Delaying troweling until the concrete is too stiff to close up reduces the possibility of delamination and makes it easier to achieve high flatness F-numbers.
Fast setting - ✅(Ch. 10, #17) During hot weather concreting, if a truckload of concrete is near the 90-minute limit when it's discharged and it looks stiff coming down the chute, what is your main concern?
True - ✅(Ch. 10, #18) True or False: When some areas of a floor are setting slower than most of the concrete, you should work around the slower setting areas to avoid sealing the surface too soon. This is likely to result in decreased floor flatness but is preferable to having to repair delaminations or blisters.
False (Proper vibration helps adjust sticky concrete. Only excessive vibration brings excessive fines to the surface) - ✅(Ch. 10, #19) True or False: When sticky mixtures are placed, you should avoid vibrating them because vibration may bring excessive fines to the surface.
Cover slab where rain is indenting the fresh surface. Use plastic sheets weighed down to protect them from blowing in the wind. Consider installing a bulkhead that will form an emergency construction joint. - ✅(Ch. 10, #20) If it starts raining on a newly placed concrete slab, what should be done?
False (They don't prevent cracks, but they hold the cracks that do form tightly closed.) - ✅(Ch. 10, #21) True or False: Adding 24-inch (610-mm)-long No. 3 or No. 4 reinforcing bars at reentrant corners prevents cracking at the corners.
