G-7 place and finish concrete

Question 1

at what stages of finishing is an edger used and why

Answer 1

after bull floating , push large aggr away from surface and form and rounds over

Question 2

why is a divider tool not used to make control joints

Answer 2

not deep enough

Question 2

what is the purpose of hand floating or bull floating

Answer 2

push aggregate down

Question 3

when is the placing of concrete completed

Answer 3

after floating

Question 4

why should the bleed water be allowed to evaporate

Answer 4

ruin water cement ratio if not causes dusting or crazing

Question 5

explain how a broom finish is created

Answer 5

floated ,broomed horizontally edged , edged and troweled

Question 6

when are screeds removed from the concrete

Answer 6

after striking off

Question 7

what is the purpose of a screed

Answer 7

guide for striking off

Question 8

how is the top of concrete wall finished

Answer 8

cleats removed and floated

Question 9

what is the purpose of kneeboards

Answer 9

disperse weight

Question 10

what tool is used to transfer flexible patterns

Answer 10

tamper

Question 11

what are 5 precautions when finishing concrete with a power trowel

Answer 11

concrete is flat/level
can bear foot pressure
cover area uniformly
bleed water evaporated
allow concrete to harden between passes

Question 12

how is the movement of a power trowel controlled

Answer 12

push down = right
push up= left

Question 13

what is a burnished surface

Answer 13

mirror like finish
created by steep angled trowels

Question 14

what are 2 different types of blades for a power trowels

Answer 14

float and trowel

Question 15

what are the environmental concerns associated with concrete treatments

Answer 15

streams and ground water

Question 16

describe how sealers and hardens also act as curing compounds

Answer 16

prevents moisture loss

Question 17

how is a exposed aggregate wall surface created

Answer 17

chemicals on forms
then washed off

Question 18

what is the difference between damp proofing and water proofing

Answer 18

moisture resistant
resist hydrostatic pressure

Question 19

how is a suspended slab water proofed

Answer 19

roofing membrane

Question 20

what are pigments used for

Answer 20

color

Question 21

what are the 2 required conditions for proper curing

Answer 21

moisture /temp

Question 22

what is a favorable temp for placing concrete

Answer 22

15-20

Question 23

explain the hydration proccess

Answer 23

chemical reaction of water and cement

Question 24

list 4 methods of curing concrete

Answer 24

water coat wet covering curing compound mechanical barriers

Question 25

how are chemical hardeners used

Answer 25

sprayed or sprinkled

Question 26

why are some curing compounds colored

Answer 26

show coverage

Question 27

If 2 coats of curing compound are used , how is the second one applied

Answer 27

Perpendicular /90 degrees

Question 28

What is the minimum curing time required to allow the concrete to gain 70% of its 28 day strength

Answer 28

3 days

Question 29

What are 2 purposes of chemical sealants

Answer 29

Waterproof and improve looks

Question 30

How are powdered hardeners applied to concrete

Answer 30

after floating and troweling

Question 31

How is the concrete mixture cooled in hot weather

Answer 31

Superplasticizer or cool water

Question 32

What causes “plastic shrinking cracking “

Answer 32

Waterloss

Question 33

What is the effect on concrete of using fossil fuel burning heaters and unvented enclosures?

Answer 33

Dusting /weak layer of concrete

Question 34

List four problems that can cause a form to fail

Answer 34

Poor bracing, poor placement, poor vibrating bad stripping

Question 35

How could vibration cause a form failure?

Answer 35

Over vibe equals stress on ties

Question 36

What causes spalling?

Answer 36

Stripping before 3 1/2 MPA and bad stripping

Question 37

What is a white crystalline growth on surface of concrete called?

Answer 37

EFFlorences

Question 38

How can scaling be prevented

Answer 38

Low water, cement ratio, proper placement, quality of concrete

Question 39

Describe the procedure used to place concrete around bucks in a wall form

Answer 39

Have we poles, if large have access hole for vibe and place on just one side

Question 40

What is the maximum aggregate size that should be used when repairing con

Answer 40

Half the patch size

Question 41

What are the advantages of using premixed grout?

Answer 41

Contains chemical bonding agents just add water

Question 42

Why are the edges of the area to be patched sloped inward

Answer 42

Tequila patch

Question 43

Why must you wet the area to be patched?

Answer 43

Some moisture won’t be sucked out of the patching mix before hydration is complete

Question 44

What service repair situations required using forms

Answer 44

Walls and overhead

Question 45

What is the minimum slump of repair concrete?

Answer 45

50 mm

Question 46

How long should a patched area be allowed to cure?

Answer 46

Three days

Question 47

Explain the sack rubbing process

Answer 47

Wet area, rub on stacking dry and let stand rub on dry sacking