The product obtained after mixing together the calcareous and argillaceous material in the right proportion and burning at high temperature is called cement. The choice of a particular type of cement depends on the properties of that cement.
By varying the quantities of constituents of the cement, we can produce various types of cement. Cement was first discovered by Joseph Aspedin in 1824. Today cement finds extensive use in construction work and is the most used construction material.
Ordinary Portland Cement
Ordinary Portland cement is the type of cement that is manufactured from finely grinding the clinkers, produced by a correct mixture of argillaceous and calcareous materials at high temperatures. It is called ordinary Portland cement because it resembles the stone quarried from Portland in the United Kingdom.
Composition of Ordinary Portland Cement (OPC)
|Iron Oxide, Fe₂ Oვ||0.5-6|
|Sulphur Trioxide, SOვ||1-2|
|Soda+ Potash, NA₂O +K₂O₅||0.5-1.3|
|Phosphorus oxide, P₂O5||0.1-0.2|
|Titanium di-oxide, TiO₂||0.1-0.4|
Lime imparts strength and soundness, its deficiency reduces the strength and setting time and causes unsoundness.
Silica imparts strength to the cement if in excess can cause the slow setting of the cement. This means a setting time of the cement will increase.
Alumina in cement is responsible for quick setting and if present in excess reduces the strength of cement.
Iron Oxide (Fe₂ Oვ)
Iron oxide is responsible for color and lowering the fusion temperature. White cement is made without adding Iron oxides.
Magnesia imparts hardness and color to the cement, if in excess cause unsoundness and cracking.
Sulphur Tri-oxide (SOვ)
Sulfur tri-oxide makes cement sound.
Soda+ Potash and other constituents (NA₂O +K₂O₅, P₂O5, TiO₂)
These are residues and if in excess cause efflorescence and cracking.
After these constituents are mixed in the required ration and burnt in the kiln we get a compound called clinkers. These clinkers are then ground to the fine powder and the resulting product is what we called cement.
Constituents of Cement Clinker ( Bogue Compounds)
|Tricalcium Silicate||Alite||CзS||25 to 50|
|Dicalcium Silicate||Belite||C₂S||25 to 40|
|Tricalcium Aluminate||Celite||CзA||5 to 11|
|Tetracalcium Alumino Ferrite||Felite||C₄AF||8 to 14|
Tricalcium Silicate (CзS)
C3S is about 25 to 50 % (normally 40%) of the cement and is responsible for the early strength of cement (7 days strength) and helps in easier grinding of the clinkers. It generates high heat of hydration therefore cement containing a high amount of Tricalcium silicate will be resistant to freezing and thawing.
Dicalcium Silicate C₂S
It is about 25 to 40 % (normally 32%) of the cement. It is responsible for the ultimate strength of cement as it hydrates slowly. At the initial stage, it imparts very little strength and becomes prominent at a later stage. It generates very little heat of hydration and if its quantity is more, cement will be subjected to freezing and thawing. It imparts resistance to chemical attack and renders the clinker hard for grinding.
Tricalcium Aluminate CзA
C3A is about 5 to 11 % (normally 10.5%) of the cement. It rapidly reacts with the water and is responsible for the flash setting of cement. Which is controlled by adding gypsum to it. Tricalcium Aluminate is chiefly responsible for initial setting of cement and it is responsible for the very high heat of hydration.
Tetracalcium Alumino Ferrite C₄AF
It is about 8 to 14 5 (normally 9% ) of the cement. It imparts very little strength to the cement and generates the highest amount of heat of hydration
Properties of Ordinary Portland Cement
There are two methods of testing the fineness of the cement. The first is, by sieve analysis and the second is Blaine’s air permeability method. When tested by Sieve analysis, its residue should not be more than 10 % on a 90-micron sieve and when tested by Blaine’s air permeability method, fineness (Specific surface in m²/Kg) should not be more than 225.
When tested with the Le-Chatelier apparatus, soundness should not be more than 10mm and 0.8% by Autoclave.
Consistency of the Cement is checked by the Vicat’s Apparatus. When tested with Vicat’s Apparatus consistency shall be 5 to 7 from the bottom of the mold.
It is tested by the Vicat Apparatus, Initial Setting time of Ordinary Portland Cement should not be less than 30 minutes and the final setting time should not be more than 10 hours.
Compressive Strength of Ordinary Portland Cement
Ordinary Portland Cement is classified into three grades, 33 Grade, 43 Grade, 53 Grade. However, Portland Pozzolana Cement consists of only one grade.
What does grade 33 cement indicate?
Ordinary Portland cement is classified into three grades namely 33 Grade, 43 Grade, and 53 Grade. Classification is done on the basis of the Compressive Strength of Cement. What does this grade signify? 33 Grade means Compressive strength of OPC at 28 days shall be 33 MPa, likewise, 43 Grade means Compressive strength of OPC at 28 days shall be 43 MPa and similarly 53 MPa.
33 Grade Cement
OPC 33 grade cement is recommended for concrete mix having a strength of up to 20N /mm2 (M 20). OPC 33 grade cement is divided into two categories. Category A has strength in the range of 32.5-37.5 MPa and Category B have strength in between 37.5- 42.5 MPa.
|No of Days||Compressive Strength in MPa|
For 43 Grade Cement
It is divided into two categories C (OPC 43) having strength 42.5-47.5 MPa and C (OPC 43) having strength in the range of 47.5-52.5 MPa.
|No of Days||Compressive Strength in MPa|
For 53 Grade Cement
It is divided into two categories E (OPC 53) having strength 52.5-57.5 MPa and F (OPC 53) having strength in the range of 57.5-62.5 MPa.
|No of Days||Compressive Strength in MPa|
Uses of Ordinary Portland Cement
It is used in all types of normal construction works.
Used in the construction of Buildings, Concrete Roads, Massive concrete dams, Culverts, Retaining walls, etc.
Low Heat Cement
Low heat cement is the type of cement that is a variation of Ordinary Portland Cement which has a lower percentage of Tri-calcium silicate C3s and Tricalcium aluminate C3a and a relatively high percentage of Di-Calcium silicate C2s.
It is manufactured by mixing together calcareous, argillaceous, and other materials like silica, iron oxide, etc. burning them at a high temperature in a kiln and grinding the clinkers produced. Gypsum is added during the grinding to increase the setting time of the cement which will set immediately after the addition of water in absence of gypsum.
- Percentage of lime shall not be more than 2.4 Sio2 +1.2 al2o3+0.65 fe2o3 and not less than 1.9 Sio2 +1.2 al2o3+0.65 fe2o3.
- The ratio of alumina to iron oxide shall not be less than 0.66.
- Insoluble residue percentage by mass shall not be more than 4%.
- Magnesia content shall not be more than 6%.
- Total sulfur content shall not be more than 2.5 % when C3A is 5% or less and shall not be more than 3.0 when C3A is above 5%.
- Total loss on ignition shall not be more than 5%.
Properties of Low Heat Cement
Fineness of cement shall not be less than 320 m2 /kg when tested by Blaine’s air permeability test.
When tested by the Le-chatelier method shall not be more than 10 mm and when tested by autoclave test, expansion shall not be more than 0.8%.
Initial setting time not less than 60 minutes.
Final setting time, not more than 600 minutes.
Compressive strength of Low Heat Cement
|No. of days||Compressive Strength|
|3 days||10 MPa|
|7 days||16 MPa|
|28 days||35 MPa|
Heat of hydration
- 7 day not more than 272kJ/kg
- 28 days not more than 314 kJ/kg
Uses of Low Heat Cement
Since the heat of hydration is very low thus low heat cement is used in the construction of abutments, concrete gravity dams, retaining walls, etc. If cement with high heat generation e.g. quick-setting cement, is used in these types of constructions, large cracks will appear.
|Compressive Strength of Low heat cement||Compressive Strength of 33 grade OPC|
As you can see from the above table, the rate of gain of strength of low heat cement is low but 28 days’ strength is approximately equal to Ordinary Portland cement. Thus care should be taken to with the removal of formwork.
Advantage or Low Heat Cement
- Due to low heat of hydration, cracks will not appear in the case of mass concrete works.
- Greater C2S content leads to better durability or resistance to environmental and chemical agents.
- Although the rate of gain of strength is slower but final setting time is similar to the OPC.
- It is resistant to sulfates due to the lower percentage of C3A.
Disadvantages of Low Heat Cement
- Initial strength of this type of cement is low. Hence, formwork will have to kept for longer time
- Due to low heat of hydration Low heat cement cannot be used in cold weather condition.
- Cost of this cement may be higher than normal cement.
Indian Standard Code for Low heat Cement
Indian Standard Portland Cement, Low heat Cement specification.
High Alumina Cement
High alumina cement is the type of cement that is produced by either fusion or sintering 40 % lime, 40 % Bauxite, and 15 % Iron oxide with Silica and Magnesia at high temperatures. Bauxite is a special clay having a high amount of alumina. As per IS 6452-1989, alumina content shall not be less than 32% for making high alumina cement, and more importantly, the ratio of the weight of alumina to lime should be between 0.85 and 1.30.
As compared to ordinary portland cement high alumina cement has very low Tricalcium Aluminate (C3A) content. Therefore, it is resistant to sulfur and other chemical attacks. Since, after setting and hardening of the cement there is no free hydrated lime left in HAC. So, there is no problem of unsoundness in this type of cement.
Typical Composition of High Alumina Cement.
|Insoluble material and loss on ignition||1.4%|
What are the properties of high alumina cement?
One of the important properties of cement is fineness. For instance, fineness in terms of specific surface (surface area per unit weight) shall not be less than 225 ㎡/kg. When tested by Blaine’s air permeability method.
Expansion of the cement should not be more than 5 mm when tested with the Le-chatelier method.
The setting time of cement, when tested by the Vicat apparatus method shall be
- The initial setting time of high alumina cement should not less than 30 min, and
- The final setting time should not be more than 10 h.
Compressive strength of at least 3 cubes tested shall be as follows
- 1-day compressive strength not less than 30 MPa, and
- 3-days compressive strength shall be not less than 35 MPa.
Uses of high alumina cement:-
- It is resistant to sulfates and acids due to the lower amount of C3A. So, It has industrial application due to being a refractory concrete.
- HAC, is best choice where high early strength is necessary.
- Used in case of precast constructions.
What are the advantages and disadvantages of High Alumina Cement?
- Due to the low content of Tricalcium Aluminate, it offers more resistance to sulphate attacks.
- It attains higher ultimate strength in short times hence can be used at a place where high strength at an early stage is required for early removal of formwork.
- Its strength after 1 day is about 40 N/mm2 and that after 3 days is about 50 N/mm2.
- Due to the generation of high heat of hydration, thus resistant to freezing and thawing.
- It can bear high temperatures hence it has application as refractory concrete.
- It is very costly to manufacture.
- we cannot use it in mass construction as it generates greater heat of hydration.
- Used in colder regions due to high heat generation.
- Can be used where high strength at an early stage is required.
- It can be used in places subjected to sulphate and chemical attacks.
IS code for high alumina cement.
IS code for high alumina cement is IS- 6452:1989 ” HIGH ALUMINA CEMENT FOR STRUCTURAL USE- SPECIFICATION.”
Portland Pozzolona Cement
Portland Pozzolana Cement is a type of cement, produced by mixing Portland cement clinkers with Pozzolana material like fly ash. After that, the clinkers and pozzolanic material are mixed and then ground together. As per the Indian Standard (IS-1489) Pozzolana material is usually mixed in the proportion of 15 to 35 % by mass of the cement. The lower limit being 15% and the upper limit is 35%.
What is Pozzolona?
Pozzolana is a volcanic powder, found in Italy called Pozzuoli by the Romans. The modern-day definition of Pozzolana is that material, which has no cementitious properties of its own but when mixed with the lime it produces a lime pozzolana compound that possesses some strength.
This resulting compound has definite cementitious properties. Ordinary Portland Cement consists of lime as the primary compound and even after the setting of the cement, some free limes remain. On the other hand, in the portland pozzolana cement, pozzolana is mixed with the lime as a result of which stable lime-pozzolana compounds are formed.
This has benefits over the ordinary portland cement. Firstly, this compound possesses some cementitious properties thus contributes to the strength. Secondly, the cost of cement is reduced by mixing waste products like pozzolana. Some examples are burnt clay, shale, and fly-ash, etc.
\Like OPC (Ordinary Portland Cement), PPC does not have a Grade. OPC comes in three grades 33, 45, and 53 MPa. The compressive strength of PPC is about 33 MPa after 28 days.
How Pozzolona Works?
Pozzolana material interacts with the calcium hydroxide released during the hardening of the cement.
Ca(OH)2 + SiO2 + (n – 1) H2O = CaO.SiO2.nH2O.
Properties of Ordinary Portland Cement
The fineness of OPC (Specific surface in m²/Kg) should not be less than 300.
When tested by the Le-Chatelier apparatus, soundness should not be more than 10 mm and 0.8% by Autoclave test.
Consistency test is done using Vicat’s apparatus. Penetration of the Vicat’s plunger is measured. It shall be 5 to 7 from the bottom of the mould.
Initial Setting Time- Min 30 Minutes
Final Setting Time – Max 600 Minutes
Compressive Strength of Cement
Average Compressive strength of 3 cubes (50 cm2 area of the face) with Cement, the sand ratio of 1:3 shall be
|No. of Days||Compressive Strength in MPa|
Uses of Portland Pozzolana Cement
- Due to its low heat generating properties, it is used in construction of the dams and mass concreting works.
- Portland Pozzolana Cement possess water resisting properties. Hence, it is used in construction of the hydraulic and marine structures.
- In the absence of free lime, resistance to the sulphate attach increases. Therefore, PPC is used in construction of the sewers and similar works.
Indian Standard for Portland Pozzolana Cement
IS Code for portland pozzolona cement- specification
Acid Resistant Cement
Acid-resistant cement is a type of cement that consists of three components, an aqueous solution of sodium silicate, an acid-resistant aggregate, and a hardening accelerant. Quartz, andesite, quartzites, diabase, and other acid-resistant aggregates are used in making acid-resistant cement. Sodium fluosilicate is used as a hardening accelerant.
The binding material in this cement is soluble glass. Which is a water solution of either sodium silicate or potassium silicate.
Soluble glass is obtained from the quartz sand. Which is then ground and thoroughly mixed with soda ash, sodium sulfate, or potassium carbonate. The solution is burnt at 1300 and 1400°C. Melting takes around 7 to 10 hours. The resultant glass mass is then cooled rapidly. After cooling it breaks up into pieces called silicate lumps.
This glass is soluble in water under normal conditions, but when high-pressure steam @ 5–6 atm at about 150°C is applied, it becomes liquid. Soluble glass hardens in the air because atmospheric carbon dioxide causes amorphous silica to settle out and dry. But this process is very slow in the air.
The hardening of soluble glass is accelerated by adding a catalyzer sodium fluosilicate which interacts rapidly with soluble glass to produce a silicate gel. The addition of sodium fluosilicate not only accelerates hardening but also enhances the water and acid-resistant properties of cement.
This cement should not be used in constructions subjected to the action of water, alkalis and phosphoric, hydrofluoric, or fluosilicic acids for long periods of time.
To enhance the water resisting property of cement, 0.5% of linseed oil or 2% of ceresit are added to it. The cement thus obtained is known as acid and water-resistant cement.
Use of Acid Resistant Cement
Acid-resistant cement is used for lining chemical apparatus and for building towers, tanks, and other installations for the chemical industry.
Soluble glass is also used for preparing acid-resistant and heat-resistant coatings.
The type of cement which expands or shows a slight increase in volume under moist conditions or on hardening is called expanding cement. In other words, the cement which does not shrink after hardening/setting is known as expanding cement. There are two kinds of expanding cement, the first is Water-impermeable and the second one is gypsum aluminous cement.
Water Impermeable Expanding Cement
This cement has the property of quick hardening and quick setting. It is obtained by grinding and mixing together aluminous cement, gypsum, and high basicity calcium aluminate. The mixture of aluminous cement and lime in the ratio 1:1 (mixed with 30% of water) is subjected to hydrothermal curing over a period of 5 to 6 hours at a temperature between 120 to 150°C to get Calcium aluminate of high basicity (4CaO.Al2O3.12H2O).
The resulting product is dried and turned into fine powder. The initial setting time of the cement is 4 and the final setting time is 10 minutes after the addition of water. However, the setting may be retarded by the addition of retarders like acetic acid and borax.
|Time||Min. Compressive Strength|
|6 hours||7.5 N/mm2|
|3 days||30 N/mm2|
|28 days||50 N/mm2|
After one day of setting and hardening, the specimens become fully impermeable to the extent of water applied under the pressure of 6 atm.
Linear expansion in this type of cement after one day of hardening or setting should not be less than 0.2 % and should not be more than 1%.
Use of Water Impermeable Expanding Cement
- It is is used for repairing concrete and reinforced concrete work because of its quick setting properties.
- Water proofing in tunnels and pit shafts.
- Underwater and underground construction work.
- At a place where water impermeable joints are required.
Gypsum Aluminous cement.
It is a quick hardening/setting cement obtained by mixing and grinding together the high alumina slag and natural dihydrate gypsum (30%). The initial setting time of this type of cement is 20 minutes and the final setting time is not later than 4 hours.
Linear expansion in this type of cement after one day of setting/hardening should not be less than 0.15% and not more than 1.0%.
Use of Gypsum Aluminous Cement
- It is is used for the manufacturing of non-shrinking and expanding water-impermeable mortars and concretes.
- For caulking joints and for waterproofing underground mines.
Rapid Hardening Cement
Rapid Hardening Cement is a type of cement that has high lime content and C3S content is higher in this type of cement. Another way to obtain RHC is by the finer grinding of Clinkers of Ordinary Portland Cement(450 m2/kg). It attains the same strength in one day which and ordinary cement may attain in three days.
However, it is susceptible to larger shrinkage and the water requirement for workability is more. The cost of this Cement is 10% more than the OPCConcrete using this type of cement is resistant to frost since it matures more quickly.
The main advantage of it is that we can remove formwork much earlier than the OPC.
Properties of Rapid Hardening Cement
Various properties of Rapid Hardening Cement are discussed below:
- Setting Time
- Compressive Strength
- Strength Gain
- Resistance to Weathering
- Curing Time
- Heat of Hydration
The Fineness of cement when tested for fineness in terms of the specific surface by Blaine’s air permeability method the specific surface of rapid Hardening Portland cement shall be not less than 325 m2/kg. The fineness of OPC (Specific surface in m²/Kg) should not be less than 300.
|Type of Cement||BIS requirement for Specific surface area in m²/Kg|
|Ordinary Portland Cement (OPC)||325|
|Rapid Hardening Cement (RHC)||300|
When tested by the ‘Le-Chatelier’ method and autoclave test unaerated cement shall not have an expansion of more than 10 mm and 0.8 percent respectively.
The setting time of the by the Vicat apparatus following requirements:
a) Initial setting time, not less than 30 minutes and
b) Final setting time, not more than 10 hours
Compressive Strength of Rapid Hardening Cement
1-day Compressive strength of RHC is 16 N/mm2
3 days Compressive strength of RHC is 27 N/mm2
Under the same condition and water-cement ratio Rapid Hardening Cement attains strength in 3 days for which ordinary Portland cement will take 7 days.
Resistance to weathering
It has high resistance to chemical and sulfate attacks.
Due to its early strength gain property, it requires less time for curing.
Heat of Hydration
It emits high heat of hydration due to its finer grinding and higher tricalcium silicate composition. Thus suitable for concreting in cold weather.
Composition of Rapid Hardening Cement
- The ratio of the percentage of lime to percentages of silica, alumina, and iron oxide, when calculated by the formula: CaO – 0.7 SiO2/ 2.8 SiO2 + 1.2 Al2O3+ 0.65 Fe2O3 shall not be greater than 1.02 and not less than 0.66.
- The ratio of the percentage of alumina to that of iron oxide shall not be less than 0.66.
- Insoluble residue, percent by mass shall not be more than 4%
- Magnesia, percent by mass shall not be more than 6%.
- Total sulfur content shall not be more than 2.5 and 3.0 when tricalcium aluminate percent by mass is 5 or less and greater than 5 respectively.
- Total loss on ignition shall not be more than 5%.
- The broad classification of Bogue’s compound in RHC is as under:-
- 60% Tricalcium silicate (C3S)
- 15% Dicalcium silicate (C2S)
- 10% Tricalcium aluminate (C3A)
- 8% Tetracalcium aluminoferrite (C4AF)
IS code for Rapid Hardening Cement
IS code for this type of cement is IS- 8041:1990 ” Rapid Hardening Portland Cement-Specification.”
Rapid Hardening Cement Uses
- This cement gains early strength thus it is possible to remove formwork early.
- It is generally used in the construction of cement concrete pavements or repairs of existing roads because it is possible to open the traffic early.
- It is used in precast construction units of electric poles, posts, slabs, etc. because it takes less time in gaining strength thus molds can be opened quickly.
- Due to its rapid evolution of heat of hydration, this type of cement is suitable for use in cold weather concreting. The heat prevents the concrete from freezing.
- It is used in construction works near seashores because it is more resistant to sulfate attacks.
- Used for repair work of buildings, bridges, and pavements because of early strength gain property.
Advantages of Rapid Hardening Cement
- Due to its property of early strength gain, the formwork can be removed early.
- This type of cement is resistant to sulfate attacks.
- The curing time required is less than the OPC.
- During setting and hardening, the shrinking is less than the OPC.
- Rapid Hardening Cement attains strength in 3 days which is equal to the strength gain by the OPC in 7 days.
Disadvantages of Rapid Hardening Cement
- It is more expensive than the OPC.
- It can’t be used in large construction projects because of its rapid evolution of heat, cracks can appear. In such situations, Low Heat Cement is used.
- This type of cement is not used in underwater construction works because of the evolution of large heat of hydration. This type of cement is finer thus more area is available for hydration which is responsible for the high heat of hydration.
- This cement utilizes all the water in the hydration process. Thus fewer pores are present which makes this cement more durable.
- Rapid Hardening cement has a smaller carbon footprint than other types of cement-like ordinary portland cement.
Extra Rapid Hardening Cement
Extra Rapid Hardening Cement is a type of cement that is prepared by adding calcium chloride with rapid hardening cement. The maximum amount of calcium chloride that can be added is 2% by the weight of the cement.
With the addition of Calcium Chloride setting time of the cement decreases thus it becomes necessary to transport the place and compact the Extra Rapid hardening Cement within 20 minutes of the mixing. OPC can be stored for about 6 months but ERHC can’t be store for more than a month.
This cement accelerates the setting and hardening process due to the addition of accelerators. More rapid is the hardening more amour of the heat of hydration is generated. This high heat of hydration helps in making the concrete which is very suitable for concreting in cold weather.
The compressive strength of this cement is about 25% more than that of the Rapid Hardening Cement in one day. and 10-20% more than at 7 days. Initially, this cement gains more strength but strength at 3 months of the Ordinary Portland Cement and Extra rapid hardening cement is almost the same.
One small disadvantage of this cement is that initially the reinforcement gets corroded but this corrosion is not progressive.