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Types Cement and Characteristic of Cement

Types of Portland Cement

· Different types of Portland cement are manufactured to meet the requirements for specific purposes

· The American Society for Testing and Materials (ASTM) Designation C150 specifies the following eight types of Portland cement

Type	Name
Type I	Normal
Type IA	Normal, air entraining
Type II	Moderate sulfate resistance
Type IIA	Moderate sulfate resistance, air entraining
Type III	High early strength
Type IIIA	High early strength, air entraining
Type IV	Low heat of hydration
Type V	High sulfate resistanc

Type I cement

· It is a general-purpose cement used in concrete for making pavements, floors, reinforced concrete buildings, bridges, tanks, pipes, etc.

· It is used in concrete not subjected to aggressive exposures, such as sulfate attack from soil and water, or to an objectionable temperature rise

Type II cement

· It is used where precaution against moderate sulfate attack is important, as in drainage structures, which may be subjected to a moderate sulfate concentration from ground waters

·It usually generates less heat of hydration at a slower rate than Type I cement and therefore can be used in mass structures such as large piers, heavy abutments, and retaining walls

· Due to less heat generation it can be preferred in hot weather

Type III cement

· It is chemically and physically similar to Type I cement, except that its particles have been ground finer

· It provides high early strengths at an early period, usually a week or less

· It is used when forms need to be removed as soon as possible or when the structure must be put into service quickly

· It is preferred in cold weather for reduction in the curing period

Type IV cement

· It is used where the rate and amount of heat generated from hydration must be minimized

· It develops strength at a slower rate than other cement types

· It is most suitably used in massive concrete structures, such as large gravity dams, where the temperature rise resulting from heat generated during hardening must be minimized to control the concrete cracking

Type V cement

· It is used only in concrete exposed to severe sulfate action – principally where soils or ground waters have a high sulfate content

· Its high sulfate resistance is due to its low C₃A content of about 4%

· It is not resistant to acids and other highly corrosive substances

Air-Entraining Portland Cements

(Types IA, IIA, and IIIA)

· These cements have same composition as Types I, II, and III, respectively, except that small quantities of air-entraining material are inter-ground with the clinker during manufacture

· These cements produce concrete with improved resistance to freeze-thaw action and to scaling caused by chemicals applied for snow and ice removal

White Portland Cement

· It has composition same as Type I or Type III cement, except that it has a white color instead of gray color

· It is made of selected raw materials containing negligible amounts of iron and magnesium oxides-the substances that give cement its gray colors

· It is used primarily for architectural purposes

Blended Hydraulic Cements

· These cements are produced by intimately and uniformly blending the Portland cement and the by-product materials, such as blast-furnace slag, fly ash, silica fume and other pozzolanas

· ASTM C 596 recognizes five classes of blended cements:

o Portland blast-furnace slag cement-Type IS

o Portland pozzolan cement-

Type IP and Type P

o Pozzolan-modified Portland cement-Type I(PM)

o Slag cement-Type S

o Slag-modified Portland cement-

Type I(SM)

Masonry Cements

· These cements are used in mortar for masonry construction

· ASTM C 91 classifies masonry cements as: Type N, Type S, and Type M

Expansive Cements

· These cements are primarily used in concrete for shrinkage control

· ASTM C 845 classifies masonry cements as:Type E-1(K), Type E-1(M), Type E-1(S)

Special Cements (Not covered by ASTM)

Type	Uses
1. Oil-well cements	For sealing oil wells
2.Waterproof  Portland cements	For reducing capillary water transmission
3. Plastic cements	For making plaster and stucco

Chemical Compounds in Portland Cement

As indicated earlier the burning operation of the raw materials results into the reaction between the oxides and four compound compositions are formed in the final cement product, as follows:

C₃S       =    3CaO.SiO₂ (Tricalcium silicate)

C₂S              =    2CaO.SiO₂ (Dicalcium silicate)

C₃A      =    3CaO.Al₂O₃ (Tricalcium aluminate)

C₄AF = 4CaO. Al₂O₃.Fe₂O₃ (Tetracalcium aluminoferrite)

Chemical and Compound Composition and Fineness of Some Typical Cements are given in Table 2-4.

Role of Compound Composition

1.    C₃S

· Hydrates and hardens rapidly and is largely responsible for initial set and early strength

· Early strength of cement is higher with increased percentages of C₃S

2.    C₂S

· Hydrates and hardens slowly

· Contributes largely to strength increase at ages beyond one week

3.    C₃A

· Liberates a large amount of heat during the first few days of hydration and hardening

· Also contributes slightly to early strength development

· Gypsum added to the cement slows down the hydration rate of C₃A

· Cements with low percentages of C₃A are especially resistant to soils and waters containing sulfates

4. C₄AF

· Does not play any significant role on hydration

Concrete Mix Design Secrets

In order to make a concrete mix design that works, you should master all the concrete theories in combination with experiences of concreting at work. Here is some important things you need to know when design concrete mixes.

A. What do you need to know before designing concrete?

1. What are the strength requirements?

- Compressive (on cube or cylinder specimen) strength

- Flexural strength

- Tensile strength
2. What is the placing method? By pump or direct pouring?

3. How far is the job site from the batching plant?

4. What is the structure for casting? Pavement, foundation, elevated slab, etc.

5. What are the projects specification?

- Maximum or minimum cement contents

- Maximum water/cement ratio

- Slump or consistency limit

- Minimum Strength requirement @28 days

- Material specifications (what is the maximum size of aggregate?)

6. Latest testing results of materials is needed in the preliminary selection of materials and design calculation

B. What are Design Precautions and Things to Remember when design concrete mixes?

1. Increasing the sand/total aggregate ratio, increases the water requirement at the same consistency.

2. Increasing the water/cement ratio decreases the strength of concrete at the same cement content.

3. Remember that adding 5 liters of water per cubic meter increases the slump by 2.5cm.

4. Remember that adding 5 liters of water per cubic meter decreases strength by approximately 4%.

5. Always follow recommended admixture dosage.

6. Always have “control” when performing trial mixes, always perform trial mixes with another mix using the same materials. This data can be useful in diagnostics if a problem occurs.

7. Always adjust batching quantities to the actual moisture condition of the aggregates.

8. Volume tolerance for 1m3 concrete is 1 ± 0.2m3.

9. Range of normal weight concrete is from 2,200 kg/m3 to 2,400 kg/m3

About the author: Do Nguyen Hung (hungsika) is a Senior Civil Engineer. He is now expert author on Civil Engineering and Construction Management.  He is the founder of Civil Engineer Website and Dream Home Building Process