Bct102 - Cement - Quicklist

Front 1

ingredients of cement

Back 1

1. silica
2. alumina
3. iron
4. lime

Front 2

ingredients of concrete

Back 2

1. cement
2. aggregates
3. water

Front 3

List the common types of cement

Back 3

- Type I - normal; general purpose
- Type II - Modified: A cement producing less heat during hydration, and having some resistance to sulfate attack. Used in lg structures and in warm weather where sulfates found in soil or water (Firebird L)
Type III - Early Strength - gains strength in from 1 to 3 days. Enables cold weather protection
Type IV - Low Heat - Heat produced by hydration kept to a minimum. Gains strength slower than normal. Used in very large structions (Hoover Dam)
Type V - Sulfate Resisting - used where severe sulfate conditions exist. Gains strength slowly (Firebird/Havasu)

Front 4

Acceptable water (% and kind) for concrete

Back 4

15% to 20% of the concrete.
All drinking water. Limits have been established on the use of water containing concentrations of chlorides, sulfates, alkalines, and solids.
1. Chlorides, sulfates and salts in high concentrations have corrosive effects on metal reinforcing rods, mesh and cables.
2. Alkalines in the mixing water may affect the hardening times of deifferent cements. Sodium carbonate can cause very rapid setting and bicarbonates can cause acceleration or retardation as well as weakness in cured concrete.
3. Solids, oils, and algae in waste water, sewage or run-off may contain such particles in sufficient concentrations to affect the strength of the cured concrete.

Front 5

List acceptable aggregates for concrete

Back 5

Aggregates such as sand, gravel and crushed stone are added to concrete to provide a volume of low-cost filler.
1. Strength of concrete comes from pieces of aggregate as well as binding of cement.
2. Size - Fine aggregates are 1/4" or less in diameter. Coarse aggregates are more than 1/4" in diameter and are usually gravel or crushed stone.
3. Shape is important - aggregate particles that are flat and long are structurally weak and require a great amt of water in the mix.
4. Weight is based upon the use for which the concrete is intended (very light - 20-70 lbs/cu. ft.; lightweight - 85-115 lbs/cu. ft.); Normal weight - 140/160 lbs/cu. ft.; Heavyweight uses iron and steel particles
5. Cleanliness - aggregates should not be coated with foreign materials such as rust, loam silt, clay, oil or vegetable matter becfause it prevents the adherence of the cement binders.

Front 6

slump

Back 6

water to cement ratio

Front 7

how to test concrete

Back 7

put in cone 12" high and place a stick across top; put in 1/3 - tap 26 times with rod; next 1/3 - tap 26 times; last 1/3
Take cone off - if it sinks down 4-5" sump - use if you're a good finisher
5-1/2"-6" sump if you're not a fast finisher
wind, heat, cold are all factors in concrete

Front 8

aggregates make up what portion of volume of concrete?

Back 8

60-80% of volume of concrete

Front 9

water makes up what portion of volume of concrete

Back 9

14-20%

Front 10

What is the catalytic action water has on transforming the chemicals in Portland cement into a hard solid?

Back 10

Hydration

Front 11

Plastic Concrete

Back 11

is concrete in a semi-liquid, pourable and moldable state.

Front 12

Green Concrete

Back 12

is concrete after it hardens, but before it gains structural strength

Front 13

Cured Concrete

Back 13

is concrete which has hardened and gained its structural strength

Front 14

Other types of Portland Cement:

Air-entrained

Back 14

During the manufacturing process, materials are added which produce many small individual air bubbles in the concrete. This improves the concrete's ability to reseist frreezing and thawing; reduces the amount of water needed in the mix, thereby producing stronger concrete and makes the plastic concrete more workable. Air-entraining is available in cement types I, II, and III. It is designated by an "A" after the type number: IA, IIA, and IIIA.

Front 15

Name 4 Admixtures added to concrete

Back 15

1. Air entraining
2. Accelerating (speeds hardening of concrete). Calcium Chloride used to be added but should not be - corrodes steel.
3. Retarding admixtures slow rate of hydration.
4. Water reducing admixtures
5. Coloring admixtures
6. Workability agent admixtures (alginates and cellulose derivites) increase working time.
7. Pozzolan, which is volcanic ash, used to reduce internal heat - benefit in pouring large structures such as dams.

Front 16

List the reinforcing materials used in concrete:

Back 16

1. steel is most used
2. reinforcing bars
3. welded wire mesh
4. Steel cables
5. glass mat

Front 17

x

Back 17

x

Front 18

x

Back 18

x

Front 19

x

Back 19

x

Front 20

x

Back 20

x

Front 21

Two Properties of Plastic Concrete

Back 21

1. Moldability: Plastic concrete may be foremd into almost any shape. It is often used for decorative effects
2. Portability: Plastic concrete may be moved in mixing trucks, motorized buggies and wheelbarrows, by belt conveyors and hydraulic pumps.

Front 22

4 properties of cured concrete:

Back 22

1. High Structural Strength: When concrete is reinforced or pre-stressed, it has high structural strength under compression, tension and lateral pressure.
2. Waterproof: Although water is used to prepare concrete, the concrete can harden under water. It should also be noted that concrete is not always waterproof out of the water.
3. Durability: Properly mixed, well-placed concrete continues to gain strength for several years and becomes almost as durable as the hardest natural stone.
4. Abrasion Resistance: Properly mixed, well-finished concrete will take heavy use with little evidence of wearing.