G-1 Concrete types, materials, additives and treatments

Question 1

Plain concrete

Answer 1

contained no reinforcing or steel mesh

Question 2

Reinforced concrete.

Answer 2

concrete is ten times stronger at compression then tension. when concrete needs to resist high levels of torsion steel mesh or cares are imbedded within concrete.

Question 3

Three fundamental properties that permit concrete to steel

Answer 3

• thermal expansion is equal
• cement paste in concrete bonds strongly to steel
• concrete protects the steel from rust

Question 4

Thermal expansion

Answer 4

concrete and steel expand at the same rate when they are heated and shrink at the same rate when they are cooled.

Question 5

Bonding

Answer 5

the bonding between cement paste and reinforcing steel transfers loads from one steel reenforcing bar to the next. the steel bars are overlapped usually 24x the width of the bar

Question 6

Corrosion

Answer 6

during hydration the cement paste bonds with the steel that protects it from corroding. in underwater concrete steel gets covered with epoxy

Question 7

Pre stressed concrete

Answer 7

this is when the reinforcing members in the concrete are placed in a state of permanent tension before service loads are applied.

Question 8

two types of pre stressed concrete

Answer 8

Pre-tension

post tension

Question 9

Pre tension Concrete reinforcement

Answer 9

high strength steel cables are placed into the formwork for the member and tensioned before the concrete is placed

Question 10

Post tensioning concrete reinforcement

Answer 10

high strength steel cables are placed in formwork but not tensioned until after the concrete is placed.

Question 11

Pre-cast Concrete

Answer 11

pre made concrete parts used for construction
beams
walls
stairs
floor slabs
girders

Question 12

Concrete shells

Answer 12

a shell is a long continuous beam of curved cross section which combines advantages os trusses, purlins and wind bracing through the interaction of its parts.
common shapes include barrels, domes, hyperbolic paraboloids and folded plates

Question 13

Concrete masonry

Answer 13

concrete masonry is applied to pre cast block and brick building units moulded of concrete and used in masonry construction.
products are made of materials that comply with local building codes.

Question 14

Concrete pipes

Answer 14

used for irrigation, drainage , sewer , culverts water supply

Question 15

Concrete paving

Answer 15

concrete is leading paving material. designed for specific loads of traffic and cost less than other materials that can carry same load.

Question 16

Air Entrainment

Answer 16

the use of air entrainment helps concrete to resist the damage caused by numerous freeze thaw cycles.
- air bubbles provide tiny chambers where water can expand into as it freezes.

Question 17

Soil-Cement

Answer 17

Soil cement is a simply highly compacted mixture of soil, Portland cement, and water. as the cement hydrates the mixture becomes more durable.

• used for paving roads, streets, airports. to complete the pavement a thin layer of sealing is placed over it.

Question 18

Shot- Crete (Gunnite)

Answer 18

this is portland cement that is applied by a pneumatically operated gun.

Question 19

Grout

Answer 19

Portland cement grout is placed under pressure and is used for

• stabilizing foundations
• making rock foundations under dams water tight
• filling cracks in concrete work

Question 20

Mortar

Answer 20

mixture of cement water and sand, bonds masonry materials together in a strong water tight bond

Question 21

fibre Reinforced concrete

Answer 21

concrete that is reinforced with class or metal fibres. these are mixed with the concrete at the time of batching.

Question 22

Self leveling gypsum

Answer 22

normally used on woodframe apartment buildings and condos. reduces noise and acts as a fire block.

Question 23

Previous Concrete

Answer 23

concrete mix that is used for specific purposes. most of its uses at present are slab on ground.
similar to regular concrete made with cement, aggregats and water. different because finished product is porous

Question 24

Portland cement is hydraulic cement meaning

Answer 24

it sets and hardens by reacting with water. this reaction is called hydration

Question 25

portland cement is a mixture of

Answer 25

Limestone, iron, silica alumina (LISA)

Question 26

General Use hydraulic cement (GU)

Answer 26

for general use, normally referred to as portland cement. this is used in general construction

Question 27

Moderate sulphate resistant hydraulic cement (MS)

Answer 27

this cement is used where precaution against moderate sulphate attack is important. if sulphates are a problem it can cause sailing cracking an expansion.

Question 28

Moderate Heat of Hydration Hydraulic Cement (MH)

Answer 28

manufactured to generate less heat when curing. used in large pilers and this retaining walls a bulk foundations. MH reduces temperature rise and possible temperature related cracking.

Question 29

High Early Strength Hydraulic Cement (HE)

Answer 29

HE cement provides high strength very quickly.

Question 30

Low Heat of Hydration Hydraulic Cement (LH)

Answer 30

used when expansion caused by heat of hydration must be minimized. this develops strength at a much slower rate. (used in massive concrete structures)

Question 31

High sulphate resistant hydraulic cement (HS)

Answer 31

HS cement is used in concrete exposed to severe sulphate action. it is used where soil or ground water has high sulphate content.

Question 32

White cement

Answer 32

white portland cement cures to a white colour. used primarily for architectural purposes.

Question 33

Masonry cement

Answer 33

mixture of portland and air entraining additional and supplement materials.

Question 34

Air-entrained Portland cement

Answer 34

added to type 10 , 20 and 30 cements improve resistance to freeze thaw conditions and to scaling caused by chemicals

Question 35

Oil-well cements

Answer 35

used to sealing oil and gas wells during drilling are made from portland cement or blended hydraulic . must be slow setting and able to resist high pressure and temperatures.

Question 36

Water proofed cement

Answer 36

adding small amounts of stearate (calcium , aluminum, or other) to portland cement during final grinding will produce waterproof portland cement.

Question 37

Plastic Cement

Answer 37

made by adding plasticizing agents up to 12%. often used for making mortar plaster and stucco

Question 38

expansive cement

Answer 38

cement that expands during the early hardening period after setting. used for patching cracks and holes in existing concrete work.

Question 39

Aggregates

Answer 39

occupy 60%-80% of concretes volume. the type size and quality of aggregates greatly influence the quality of concrete.

Question 40

coarse aggregates

Answer 40

5mm and larger

Question 41

fine aggregates

Answer 41

smaller then 5mm

Question 42

Quality of aggregates

Answer 42

must be clean, hard and strong and durable and free of absorbed chemicals and clay coats.

Question 43

Slump test

Answer 43

used to test the consistency of concrete mixture. *remember cone video* 3-4" slump is common for good quality cement.

Question 44

water /cement ratio and strength

Answer 44

compressive strength is universal measure of concretes strength. the more water the less strength

Question 45

water to cement ratio

Answer 45

is the weight of cement to the weight of water used in the mix.

Question 46

Admixtures

Answer 46

for concrerte to modify properties

Question 47

Air entrained admixtures

Answer 47

put microscopic bubbles into concrete. enhance ability to withstand freeze thaw cycles.

Question 48

Water-reducing admixtures

Answer 48

added to concrete ti reduce amount of water required yet still maintaining required slump. by reducing amount of water needed the strength of concrete is increased.

Question 49

Retarding admixtures

Answer 49

added to concrete to slow its setting rate. used in temperatures over 30degrees

Question 50

Accelerating admixtures

Answer 50

added to increase rate of strength gain. needed to allow early stripping, protect concrete from freezing and to generally speed up construction process. calcium chloride is used to accelerate setting * do not use in concrete with steel reinforcements

Question 51

Superplasticizers

Answer 51

added to concrete to increase the slump of mixture. active for short time no more then 60 min.

Question 52

Damp-proofing and permeability-reducing agents

Answer 52

included when low cement content or a high water cement ratio is used.

Question 53

Bonding agents

Answer 53

used when fresh concrete is to be applied to the face of an old existing concrete.

Question 54

Gas fourming agents

Answer 54

expands grout a it cures. would be used in a grout designed to prevent water through wall cavities and cracks

Question 55

Pozzolans

Answer 55

used in the mixture to reduce the cost o the finished concrete. possesses little or no cementing properties but when mixed with cement, it will hep to bond concrete together.

Question 56

Metallic aggregates used in grout formulas because?

Answer 56

to allow grout to expand and offset the shrinkage.

Question 57

Dry pack grouts

Answer 57

used where spaces are wide enough to pack grout into them.

Question 58

Liquid grout

Answer 58

to fill small gaps