What Does Pozzolanic Mean? Why Is Pozzolana Added To Cement?
What Does Pozzolanic Mean?
Pozzolanic refers to a type of material which, when combined with water and lime, forms a cement-like material known as ‘pozzolana’.
This can be an artificial material derived from volcanic ash or industrial by-products, or a natural material like diatomaceous earth.
The pozzolana cement can be used for various construction purposes such as making concrete blocks and mortar that is often more durable than regular Portland cement.
Pozzolana cements have many other advantages too; they are less expensive, require less energy to produce, and have lower CO2 emissions when compared to ordinary Portland cements.
Additionally, they also possess superior properties such as improved resistance to temperature fluctuations and increased durability in freezing conditions.
Where Is Pozzolanic Cement Used?
Pozzolanic cement is primarily used in construction projects that require high-strength and long-lasting concrete.
This type of cement is made with a combination of pozzolanic materials, such as fly ash, and Portland cement. Pozzolanic cement can be used for structural foundations, bridge decks, and pavements that need to withstand heavy loads.
It also offers excellent thermal performance and low shrinkage in comparison to traditional Portland cements.
Furthermore, it offers superior abrasion resistance abilities which make it ideal for environments where wear and tear are commonplace.
Pozzolanic cement can be advantageous for applications in marine areas due to its very low permeability capabilities.
Why Is Pozzolana Added To Cement?
Pozzolana is added to cement to improve its strength and durability. It is a silica-rich material that produces calcium hydroxide with the hydration of water which itself combines with other compounds in the cement, thus increasing its resistance to attack by aggressive chemicals.
Additionally, it helps prevent excess shrinkage during the hardening of cement due to its expansion property and can reduce the heat of hydration.
Pozzolana also increases workability of concrete mixes due to its fineness and reduces bleeding of water from freshly poured concrete.
Lastly, it can reduce costs for large scale projects due to its low cost compared to ordinary Portland Cement.
How Is Pozzolanic Cement Made?
Portland-pozzolana cement shall be produced either by blending Portland cement clinker and fly ash together carefully, or by carefully and uniformly combining Portland cement with finely milled fly ash.
The amount of fly ash must not be lower than 10% and not higher than 25% of the total mass of Portland-pozzolana cement.
What Are The Advantages Of Pozzolanic Materials?
Pozzolanic materials offer a variety of advantages, including high resistance to corrosion, low cost, and improved mechanical properties.
These materials are designed to improve the strength and durability of cement-based systems by providing supplementary sources of silica, alumina, and other oxides in Portland cement structures.
Pozzolanic material can be used as an admixture to reduce concrete shrinkage and increase its compressive strength. It is also able to absorb water and swell about 10 times its dry volume for greater density.
Additionally, pozzolanic material has been proven to reduce total pores in the material structure significantly, resulting in better waterproofing performance.
What Is Pozzolanic Effect?
Pozzolanic effect is a reaction between siliceous and aluminous components which, when combined, form a compound that has increased strength and durability.
This reaction is caused by the presence of natural pozzolans such as volcanic ash, silica fume, burnt clay or shale, and other materials that are rich in reactive silica.
When these pozzolans are added to a cementitious material like portland cement, they can react with calcium hydroxide to form calcium silicate hydrates (CSH) which provides additional strength and durability to the concrete.
The addition of pozzolans to a cement-based material increases its workability as well as overall performance.
Does Pozzolana Increase Shrinkage?
Pozzolana, a natural or artificial material, can be used as an additive to cement to make it more water-resistant and strong. However, the use of pozzolana can increase the shrinkage of cement.
The decrease in size can be attributed to the presence of calcium hydroxide and carbon dioxide in the pozzolana which causes a loss of water from the mix when heated.
This leads to a decrease in volume, hence causing shrinkage. Also, because pozzolana has a lower heat of hydration than Portland cement does, it adds additional energy from heat which creates further shrinkage.
Ultimately, using pozzolana as a supplement for Portland cement will lead to an increase in shrinkage but with its added strength benefits and water resistance properties this might not necessarily be negative for certain applications.
