TYPES OF CEMENT - Properties, Advantages and Disadvantages

TYPES OF CEMENT

RAPID HARDENING CEMENT:

• Rapid hardening cement is very similar to ordinary portland cement (OPC).
• It contains higher C3S content and finer grinding. Therefore it gives greater strength development at an early stage than OPC.
• The one-day strength of this cement is equal to the three-day strength of OPC with the same water-cement ratio.
• The strength of this cement at the age of 3 days is almost same as the 7 days strength of OPC with the same water-cement ratio.
• The main advantage of using rapid hardening cement is that the formwork can be removed earlier and reused in other areas which save the cost of formwork.
• This cement can be used in prefabricated concrete construction, road works,etc.
• But, the initial and final setting time of Rapid Hardening Cement is same as that of ordinary PPC cement.

These cements have about 56% of tricalcium silicate which is higher content. These are due to the following facts,

• These cements are burned at higher temperatures, 
• The cement is grinded to fine,
• high percentage of lime content.

Disadvantages of Rapid Hardening Cement:

It is costly.

LOW HEAT CEMENT

• Low Heat Cement as the name indicates these type of cement is used in order to reduce the amount of heat evolved during setting.
• But how the heat evolved during setting can be reduced ?
• Yes, the heat during setting can be reduced by lowering the percentage of tri-calcium aluminate C3A of about 5% an higher percentage of di-calcium silicate  C2S of about 46%.
• This cement is less reactive and its initial setting time is greater than OPC. 
• This cement is mostly used in mass concrete construction.

Disadvantages of Low Heat Cement:

• Cannot be used in cold weather conditions because it will retard the setting time than in ordinary weather.
• The compressive strength is lower than that of ordinary cement.

WHITE CEMENT

• White cement is a type of ordinary Portland Cement which is pure white in color and has practically the same composition and same strength as OPC.
• To obtain the white color the iron oxide content is considerably reduced.
• The raw materials used in this cement are limestone and china clay.
• This cement, due to its white color, is mainly used for interior and exterior decorative work like external renderings of buildings, facing slabs, floorings, ornamental concrete products, paths of gardens, swimming pools etc.

SULFATE RESISTING CEMENT

• Sulfate resisting cement is made by reducing C3A and C4AF content.
• Cement with such composition has excellent resistance to sulfate attack.
• This type of cement is used in the construction of foundation in soil where subsoil contains very high proportions of sulfate.
• Sulphate Resisting Portland Cement is a type of Portland cement in which the amount of
• Tricalcium aluminate (C3A) is restricted to lower than 5 % and (2 C3A + C4AF) is lower than 25%.
• SRC can be used for structural concrete wherever OPC or PPC or Slag Cement is usable under normal conditions.
• The use of SRC is particularly beneficial in such conditions where the concrete is exposed to the risk of deterioration due to sulphate attack.

The SRC is recommended for following applications

• Foundations, piles.
• Basements and underground structures.
• Sewage and Water treatment plants.
• Chemical, Fertilizers and Sugar factories.
• Food processing industries and Petrochemical projects.
• Coastal works.
• Also for normal construction works where OPC is used. 
• Construction of building along the coastal area within 50 km from sea.

PORTLAND POZZOLANA CEMENT

• Portland Pozzolana Cement is a kind of Blended Cement which is produced by either inter grinding of OPC clinker along with gypsum and pozzolanic materials in certain proportions or grinding the OPC clinker, gypsum and Pozzolanic materials separately and thoroughly blending them in certain proportions.
• Pozzolana is a natural or artificial material containing silica in a reactive form.
• It may be further discussed as siliceous or siliceous and aluminous material which in itself possesses little, or no cementitious properties but will in finely divided form and in the presence of moisture, chemically react with calcium hydroxide at ordinary temperature to form compounds possessing cement properties.
• It is essential that Pozzolana be in a finely divided state as it is only then that silica can combine with calcium hydroxide (liberated by the hydrating Portland Cement) in the presence of water to form stable calcium silicates which have cement properties.

The pozzolanic materials commonly used are:

• Volcanic ash
• Calcined clay
•  Fly ash
• Silica fumes

Portland Pozzolana Cement is ideally suited for the following construction:

• Hydraulic structures.
• Mass concreting works.
• Marine structures.
• Masonry mortars and plastering.
• Under aggressive conditions.
• All other applications where OPC is used.
• The compressive strength of PPC as per BIS code at present is equivalent to that of 33 grade OPC

HYDROPHOBIC CEMENT

• Hydrophobic cement is manufactured by adding water repellant chemicals to ordinary portland cement in the process of grinding.
• Hence the cement stored does not spoiled even during monsoon.
• This cement is claimed to remain unaffected when transported during rains also.
• Hydrophobic cement is mainly used for the construction of water structures such dams, water tanks, spillways, water retaining structures etc.
• These type of cement contains some of the admixtures like acidol, napthalene soap, petrolatum (oxidised) along with others.
• These admixtures form a thin film layer over the cement grains. If water is added to hydrophobic cement, the absorption films are torn of the surface and they do not in any way, prevent the normal setting of cement.
• But, in initial stage the setting of hydrophobic cement is slow because the admixtures surrounding as a thin film over the cement grains prevents the interaction with water. 
• But the strength after 28 days when compared to that of ordinary cement is same.

Advantages of Hydrophobic Cement:

1. These cements are used in construction of dams, spillways, under water constructions.

2. It can also be used in cold weather conditions.

3. Strength is same as that of ordinary cement.

Disadvantages of Hydrophobic Cement:

1. It is very Expensive.

COLORED CEMENT

• This Cement is produced by adding 5- 10% mineral pigments with portland cement during the time of grinding.
• Due to the various color combinations, this cement is mainly used for interior and exterior decorative works.
• The amount of colouring material may vary from 5 to 10 per cent.
• If this percentage exceeds 10 per cent, the strength of cement is affected.
• The chromium oxide gives green colour.
• The cobalt imparts blue colour.
• The ton oxide in different proportions gives brown, red or yellow colour 
• The manganese oxide is used to produce black brown coloured cement

The coloured cements are widely used for finishing of floors, external surfaces, artificial 

marble, window sill slabs, textured panel faces, stair treads, etc.

WATERPROOF PORTLAND CEMENT

• Waterproof cement is prepared by mixing with ordinary or rapid hardening cement, a small percentage of some metal stearates (Ca, Al, etc) at the time of grinding.
• This cement is used for the construction of water-retaining structure like tanks, reservoirs, retaining walls, swimming pools, dams, bridges, piers etc.

PORTLAND BLAST FURNACE CEMENT

• In this case, the normal cement clinkers are mixed with up to 65% of the blast furnace slag for the final grinding.
• This type of cement can be used with advantage in mass concrete work such as dams, foundations, and abutments of bridges, retaining walls , construction in sea water.
• UltraTech Premium's composition comprising high quality clinker blended with  judicious amounts of superior blast furnace slag having high glass content,  gypsum devoid of deleterious materials and optimum PSD (Particle Size Distribution) ensures its unsurpassable performance year on year.
• UltraTech Premium Cement can be used for varied building construction processes which include all types of PCC, masonry and plaster works.
• UltraTech Premium is also extensively used for mass concrete applications like large foundations, dams, concrete roads among others.
• It is ideal for RCC in marine and aggressive environments due to its superior resistance to attack of sulphates and chlorides.
• It can be used for structures below the ground and for those that are in contact with water.
• UltraTech Premium, with superior 28-day compressive strength, forms an ideal solution for critical applications such as slabs, columns, beams and roofs.

AIR ENTRAINING CEMENT:

• It is produced by air entraining agents such as resins, glues, sodium salts of sulfate with ordinary portland cement.
• Air-entrained concrete is produced using air-entraining portland cement, or by the introduction of air-entraining agents, under careful engineering supervision, as the concrete is mixed on the job.
• The amount of entrained air is usually between four and seven percent of the volume of the concrete, but may be varied as required by special conditions.
• Air-entrained portland cement is a special cement that can be used with good results for a variety of conditions.
• It has been developed to produce concrete that is resistant to freeze-thaw action, and to scaling caused by chemicals applied for severe frost and ice removal.
• In this cement, very small quantities of air-entraining materials are added as the clinker is being ground during manufacturing. 
• Concrete made with this cement contains tiny, well-distributed and completely separated air bubbles. 
• The bubbles are so small that there may be millions of them in a cubic foot of concrete.  
• The air bubbles provide space for freezing water to expand without damaging the concrete.  
• Air-entrained concrete has been used in pavements in the northern states for about 25 years with  excellent  results.  
• Air-entrained concrete also reduces both the amount of water loss and the capillary/water-channel  structure.

HIGH ALUMINA CEMENT

• High alumina cement (HAC) is a special cement, manufactured by mixing of bauxite ( aluminum ore) and lime at a certain temperature.
• This cement is also known as calcium aluminum cement (CAC).
• The compressive strength of this cement is very high and more workable than ordinary portland cement.

Characteristics of High Alumina Cement

The characteristics of this cement can be surfacely summarized in following points:

• High alumina cement has low pH
• It has high durability in sulfuric acid
• It hardens rapidly
• It is less reactant than alumina or hydraulic lime
• It has high resistance to chemical corrosion. 
• So, it is widely used also in construction of water pipes, sewage pipes, factory drains, coastal constructions and in factory chimneys.

Advantages of High Alumina Cement

Following are the advantages of High Alumina Cement:

• The initial setting time of this cement is more than 3.5 hours. 
• The final setting setting time is about 5 hours. 
• It therefore allows more time for mixing and placing operations.
• It can stand high temperature.
• It evolves great heat during setting. It is therefore not affected by frost. 
• It resists the action of acids in a better way.
• It sets quickly and attains higher ultimate strength in a short period. 
• Its strength after 1 day is about 40 N/mm2 and that after 3 days is about 50 N/mm2.
• Its setting action mainly depends on the chemical reactions and hence it is not necessary to grind it to fine powder.

Disadvantages of High Alumina Cement 

Following are the disadvantages of High Alumina cement:

• The extreme care is to be taken to see that it doesn’t come in contact with even traces of lime or ordinary cement.
• It cannot be used in mass construction as it evolves great heat as it sets soon.
• It is costly.

EXPANSIVE CEMENT

• The cement which does not shrink during and after the time of hardening but expands slightly with time is called expansive cement. 
• This type of cement is mainly used for grouting anchor bolts and prestressed concrete ducts.
• Expansive concretes are divided into two categories, shrinkage-compensating and self-stressing.
• Shrinkage-compensating concrete is an expansive cement concrete in which expansion if restrained induces compressive stresses which approximately offset tensile stresses in the concrete induced by drying.
• Self-stressing concrete is an expansive cement concrete in which expansion, if  restrained, induces compressive stresses of a high enough magnitude to result in  significant compression in the concrete after drying shrinkage and creep has  occurred.