Portland Pozzolana Cement use cases; Pros and Cons

Articles > Portland Pozzolana Cement use cases; Pros and Cons

Introduction to PPC (Cement):

There are more than a dozen types of cement. Each type has its own advantages and disadvantages. PPC is one of them with its own distinctive qualities, that make it popular all around the world. PPC stands for Portland Pozzolana Cement. The word Portland is used because the inventor of this cement “Joseph Aspdin” of England in 1824, used the very first cement for the first time to set the stone namely “Portland”. Pozzolana is the name of ash released as a result of a volcanic eruption. Thus, this cement is the product of ordinary Portland Cement and Volcanic Ash.

Uses of PPC:

PPC is more durable than Ordinary Cement, because of its resistance against Sulfate, water, and other chemical attacks. Portland Pozzolana Cement is used in the construction of buildings near seashores, dams, marine structures, dams, and other constructions in damp places. Underwater bridge piers and abutments are also constructed by means of this type of cement.

  1. For the construction of hydraulic structures.
  2. Used in the construction of massive structures like bridge piers, dams, and other thick foundations.
  3. It is used in drainage and sewage and sewerage systems.
  4. Bridge decks are constructed with RCC made of PPC.
  5. Building near seashores is prone to sulfate attack, therefore the use of OPC is not suitable in seashore constructions. PPC is the best option in such circumstances.
  6. As at a later stage of hydration, the hardness of PPC is greater than that of OPC, therefore a huge foundation, high walls, dams, and other gigantic structures are made with PPC.
  7. Canals and canal falls are constructed by means of PPC, as they are invincible before the attack of water and water-soluble salts.
  8. Barrages, which remain merged in the water for a longer period of the year are also constructed with PPC cement.
  9. Underground basements are constructed with PPC, as it is resistant to moist surrounding

Chemical Composition of PPC:

Portland Pozzolana Cement is made from 45% to 60% OPC and 40% to 55% Pozzolanic Material. Thus the Chemical composition of Portland Pozzolana Cement is:

Compound

Formula

Shorthand form

% by weight

Tricalcium Aluminate

Ca3Al2O6

C3A

7 %

Tetracalcium Aluminoferrite

Ca4Al2Fe2O10

C4AF

5 %

Belite or Dicalcium Silicate

Ca2SiO5

C2S

11 %

Alite or Tricalcium Silicate

Ca3SiO4

C3S

25 %

Sodium Oxide

Na2O

N

 

2%

Potassium Oxide

K2O

K

Gypsum

CaSO4.2H2O

CSH2

5 %

Pozzolanic Ash

 

 

45%

Advantages of PPC:

  1. The soluble calcium hydroxide is converted into insoluble cemented ingredients, thus making the structure impervious/impermeable to water.
  2. The production of Calcium Hydroxide is not as much as it is in OPC. The low level of calcium hydroxide significantly provides all-round strength and durability to the concrete structure.
  3. The silicate formation in concrete made of PPC continues even after the slowing down of hydration. The process of hardening of Ordinary Cement lasts by the end time of hydration, while the process of hardening of PPC continues even after the completion of the hydration process. The compaction and hardness continue up to 90 days.
  4. The modulus of elasticity of PPC is lesser at the earlier stage of cementing, and greater at the later stage than OPC. On the other hand, the modulus of elasticity of OPC at initial age is higher than PPC, and at a later age, it is lesser than PPC.
  5. Concrete becomes porous and permeable if it has void spaces. PPC made structures are generally less porous because most of the lime is dissolved during early hydration. Once the structure is set, the soluble silica forms an insoluble cementitious compound, which fills the voids, vacuoles, and hollow capillaries.
  6. The generation of heat of hydration is lower than OPC.
  7. The setting time of concrete is prolonged, which helps the mason for good finishing of concrete or cement mortar. The cohesiveness of the concrete mix helps for better finishing of concrete.
  8. It also prohibits micro-cracks in the structure, which further increases the strength of the concrete structure.
  9. If there is enough moisture, the durability and strength further increase after passing a period of 90 days. The long term durability of the PPC is greater than the OPC.
  10. The particles of Pozzolanic Cement are spherical, which provides fineness to the surface of the constructed structure.
  11. This type of cement bleeds less. Bleeding means some of the water of fresh concrete tends to rise up on the surface of the concrete structure. The high ratio of water at the surface will make the surface too wet, resulting in porous, weak, and nondurable. PPC prevents bleeding.
  12. This is economical because about 30 to 45 percent of OPC is replaced by natural products; pozzolana/ volcanic ash.

Disadvantages of PPC:

  1. Dismantling of shuttering early is very harmful to the constructed structure because the early hardening of the PPC is lesser than that of OPC.
  2. It does not prevent the reinforced steel from corrosion due to the alkalinity reduction.
  3. Setting time is longer than that of OPC. The ordinary setting time for OPC structures is 600 minutes or 10 hours.

 

 


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