Portland pozzolana cement (PPC): manufacturing, properties and uses, hi guys in this article we know about PPC cement, PPC cement full form, PPC cement grade, properties & uses of PPC cement and advantage and disadvantage of Portland pozzolana cement.
As we know PPC cement full form is Portland pozzolana cement, the name Portland & pozzolana are both historical term used before naming cement. The Portland name is historical place islet of portland in Dorset of England which have large amount of natural cement as Portland stone which are used to formed Portland cement,its beginning in the middle of the 18th century in Britain.
Pozzolana was first found at Puteoli near Naples where huge amount of bed of pozzolana found in Italy, natural pozzolana is composed mainly of a fine chocolate-red volcanic earth. artificial pozzolana has been developed that combine fly ash and water quenched boiler slag.
Portland Pozzolana Cement is becoming a most popular type of cement used in construction line like building construction, formation of multistorey building, Super structure, Bridge, Dams, Industrial & commercial building.
PPC is made from natural pozzolanic material. Natural Pozzolanic material history extended up to roman time. Portland Pozzolana Cement or ppc cement is manufactured by grinding the OPC clinker with 10 to 25 percent of the pozzolanic material mix with water. As per the recent time in standards of manufacturing, it is about 35% of pozzolanic material
Manufacturing process of Portland Pozzolana Cement (ppc)
A artificial Pozzolanic ingredient in PPC cement is fly ash essential material includes the siliceous or aluminous material which itself does not possess any cementitious and binding properties, it is finely divided form and in the presence of water react with calcium hydroxide liberated in the hydration process which is performed at normal temperature to form compounds Possessing cement properties.
In the manufacturing process of PPC cement, the main ingredients are calcined clay, or fly ash is a wastes material, generated in the thermal power station when powdered coal is used as a fuel. This material is then collected in electrostatic precipitators. In the United Kingdom, it is known as pulverized fuel ash so fly ash and pulverized ash both are same.
The material produced may also called as calcium silicates produce considerable quantities of calcium hydroxide, which is by and large a useless material from the point of view of strength or durability. It is just a waste material which could be converted into cementitious product; it considerably improves quality of concrete.
The pozzolanic action is shown below:
Calcium hydroxide + Pozzolana + water — > C – S – H (gel)
Why is better to use PPC Cement in concrete? Generally when PCC cement is used in formation of concrete produce lesser heat of hydration and offer greater resistance to the attack of aggressive waters than ordinary Portland cement. Moreover, it reduces the leaching of calcium hydroxide when used in hydraulic structures.
Such types of low heat-producing properties of ppc cement are mainly useful in marine and hydraulic construction and other mass concrete constructions like Dams bridge, pile strong foundation etc.
However, it is fact that addition of Pozzolana does not contribute to the much strength at biggining time. The strength property of PPC are little higher to that ordinary Portland cement. Concrete setting time is more in PPC cement than ordinary Portland cement.
In case, if portland pozzolana cement is manufactured by using the right type of reactive pozzolanic material, the Portland pozzolanic cement will similar to ordinary Portland cement except for the rate of gaining strength early up to 7 days.
It will affect to OPC only when bad quality of pozzolanic materials are used, which are not of the reactive type and which do not satisfy the specifications limit for pozzolanic materials, are used the cement would be of doubtful quality.
Properties of Portland Pozzolana Cement(PPC)
1) setting time of PPC cement is more than ordinary Portland cement,it again little strength in beginning of construction but final strength is much high, its Initial setting time is 1/2 an hour and final setting time is about 10 an hour.
2) strength :- as we know PPC cement require more time to gain its strength, in 3 days of intial construction its compressive strength is 13MPa, in 7 days 22 MPa , in 28 days 33 MPa.
3) Drying shrinkage should not be more than 0.15% for ppc cement
4) Fineness should not be less than 300 m2/kg for ppc cement
5) The early strength of PPC is less but the final strength is equal to the 28 days strength of OPC cement
5) important properties of PPC cement is that it make a resistance against aggressive attack of harmful chemical like carbonate,acid alkalies which are dissolved in water and also prevent from adverse climatic condition to external wall.
Investigation Result on PPC cement
All the way we have advantages of PPC are mainly due to the slow conversion of calcium hydroxide in hydrated cement paste into the cementitious products.
Hydroxide in one-year-old OPC paste was found to be only 8.4 percent calcium hydroxide in a and leaching also a certain reduction in calcium hydroxide may have taken place. After considering the effect the calcium hydroxide should have been 14%.
But, actually only 8.4% has remained in it which goes to prove that 5.6% of calcium hydroxide was converted by the pozzolanic activity.
Advantages of Portland Pozzolana Cement (PPC)
The advantages of Portland Pozzolana Cement can be summarized as follows:-
Using PPC with OPC has greater advantages if proper types of reactive materials are used in manufacturing of PPC.
1) PPC is made by replacing costly clinker with cheap waster pozzolanic material.
2) In PPC manufacturing a soluble calcium hydroxide is converted into insoluble cementitious products which result in improvement of permeability. Hence it offers, abounds durability characteristics, particularly in hydraulic structures and marine construction.
3) Generally, a Portland pozzolana cement consumes the calcium hydroxide and does not produce calcium hydroxide as much as that of OPC.
4) It produce heat of hydration and that too at a low rate.
5) PPC being finer than OPC and also due to pozzolanic action, it improves the pore size distribution and also reduces the micro cracks at the transition zone.
6) Reduction in permeability of Portland pozzolana cement offers many other & bound advantages.
7) Fly ash used in PPC is lightweight and has less density, the bulk volume of 50 kg bag is slightly more than OPC. That’s why Portland pozzolana cement offers a larger volume of mortar than OPC.
8) PPC strength development over a long period is comparatively more than OPC if enough moisture is available for continued pozzolanic action.
Disadvantages of Portland pozzolana cement
There are following disadvantage of Portland pozzolana cement
1) PCC has a low rate of development of strength initially compared to OPC.
2) PPC has lower the alkalinity contain which reduces the resistance to corrosion of steel reinforcement. But on the other hand, PPC significantly improves the permeability of concrete, increases the resistance to corrosion of reinforcement.
3) The setting time is nominally longer.
PPC cement grade
In many area of world the PPC is graded similarly to OPC depending upon their compressive strength, at 28 days. As per India Standard the PPC cement strength is considered equivalent to 53 grade OPC cement.
Many cement brands recommended using BIS for grading of PPC just like grading of OPC. They also suggested using a higher amount of fly ash content from 25% to 35%. Recently, the Unites Kingdom has increased the fly ash content in PPC in BIS from 10-25% to 15-35%.
Application & uses of Portland Pozzolana Cement (PPC)
Portland Pozzolana cement can be utilized where OPC is used except where high early strength is of special requirement. As PPC use demands the moisture for sustained pozzolanic activity, a little longer curing is desirable. Use of PPC would be particularly suitable for following situations:
i) For hydraulic structures;
ii) For mass concrete structures like dam, bridge pier and thick foundation;
c) For Marine structures;
d) For sewers and sewage disposal works etc.
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