G7

Question 1

what is a main powdered hardener?

Answer 1

Sodium Silicate, sprinkled over concrete and bull floated in reacting with the lime creating a hard dust-proof surface

Question 2

how fast should you place the concrete after the water has been added?

Answer 2

120 minutes

Question 3

what is and edger?

Answer 3

used too round the outside corners of the surface of the slab, and create a decretive boarder

Question 4

what is spalling around rustication strips? (keyways)

Answer 4

larger bits or chunks of concrete stuck too the strip and pulled off

Question 5

how far apart, and how far down does the pencil vibrator get placed when vibrating concrete walls?

Answer 5

not more than 600mm apart and 150mm into the previous layer

Question 6

What does a bull float do?

Answer 6

used too push larger aggregates under the surface and level and smoothen large slabs

Question 7

what does spalling mean?

Answer 7

Spalling is similar to scaling except large chunks instead of just flakes break loose

Question 8

how long should the area being patched stay wet for?

Answer 8

2 hours prior to patching

Question 9

what does dusting mean?

Answer 9

fine loose powder caused by the deterioration of a weak surface.

Question 10

what happens when dry shrinkage occurs?

Answer 10

shrinkage happens mostly because of the reduction of capillary water by evaporation and the water in the cement paste. Tensile stress increases causing stress cracks

Question 11

what is honeycombing?

Answer 11

trapped air bubbles from improper vibration that is visible after forms are removed

Question 12

what is placed just before the patch goes on?

Answer 12

a bonding agent

Question 13

what are concrete buckets used for?

Answer 13

moving concrete on tall buildings hoisted by a crane

Question 14

what is curing?

Answer 14

to keep concrete moist as long as possible for maximum strength growth

Question 15

what is a groover?

Answer 15

like a hand divider tool but larger with a long handle for making grooves in slabs

Question 16

why should the edges of the area being patch be sloped inward?

Answer 16

to create more surface and bonding area for the patch

Question 17

what is Efflorescence?

Answer 17

As water from the interior of the concrete migrates to the surface and evaporates, salts are deposited on the surface, usually as a white stain

Question 18

what does segregation mean?

Answer 18

excessive vibration causing the course course aggregates to settle to the bottom.

Question 19

what should the slump of a concrete patch be?

Answer 19

no less than 50mm

Question 20

what does it mean too continually pour concrete within multiple forms or slabs?

Answer 20

Monolithic concrete placement

Question 21

how far apart are external vibrators placed?

Answer 21

1200mm apart

Question 22

what is bleed water?

Answer 22

excess water in the concrete mixture that is not needed for the chemical reaction with the cement. the bleed water will rise too the surface and evaporate.

Question 23

what does crazing mean?

Answer 23

minute cracking of the concrete surface caused by bleed water not fully evaporated disrupting the water/cement ratio

Question 24

what is a screed/strike off bar and what does it do?

Answer 24

long 2X4 the extends beyond the edge of a slab for to level out the concrete

Question 25

What happens when concrete flash sets?

Answer 25

concrete hardens too quickly resulting in improper finishing and inadequate strength

Question 26

What is the capacity of a concrete bucket?

Answer 26

Depends on the lifting capacity of the crane, usually able too care between 0.4 - 1.5m cubed

Question 27

what does flaking mean?

Answer 27

very thin flakes of concrete separating from the surface

Question 28

What is the soul purpose of vibration?

Answer 28

To remove pockets of air from the concrete

Question 29

what is the difference between a divider and a control joint tool?

Answer 29

a divider is only for decorative purposes where a control joint tool has a deeper cutter for creating control joints

Question 30

what are 2 ways to keep concrete moist for an extended period of time?

Answer 30

spray-on acrylic curing liquid or plastic sheets

Question 31

what is the minimum temperature for curing?

Answer 31

10 degrees celsius

Question 32

what is the minimum and maximum slope of a walkway

Answer 32

2% to 8%

Question 33

what is sack-rubbing finish mean?

Answer 33

concrete low spots can be filled with the use of a flowable sacking mix mortar and burlap pads. fills voids in the concrete and left flush with surrounding surfaces.

Question 34

Concrete is placed in lifts because why?

Answer 34

so that the overall height of the fresh concrete does not exceed the rate of placement set by the form design

Question 35

concrete that has only been cured for 0 days, 3 days, or 7 days will only have which percent strength?

Answer 35

50%, 70%, 90% of it 28 day strength