OPC (Ordinary Portland Cement) and PPC (Portland Pozzolana Cement) are two widely used types of cement in construction. Both are hydraulic cement, meaning they harden when mixed with water. However, there are some key differences between the two types of cement, including their composition, properties, and applications.
Though they share the same goal, they have significant differences between them. Amongst the differences, one of the differences is, they need different time periods of curing, OPC requires at least 7 days for curing whereas PPC requires a minimum of 10 days. To learn more about them, stay with us till the end and find out the unknowns that you are looking for!
Side-by-Side Difference Between OPC and PPC
To appreciate the distinction between Ordinary Portland Cement and Portland Pozzolana Cement, let’s put them under the microscope, shall we?
OPC is made by grinding limestone, clay, and gypsum together. PPC is made by grinding OPC clinker and pozzolanic materials together. Pozzolanic materials are siliceous or aluminous materials that react with calcium hydroxide to form cementitious compounds. Some common pozzolanic materials used in PPC include fly ash, silica fume, and ground granulated blast furnace slag.
Strength at Different Stages
OPC has a higher initial strength than PPC. However, PPC develops higher long-term strength than OPC. This is because the pozzolanic materials in PPC react with calcium hydroxide to form cementitious compounds over time. The following diagram will help you to understand properly –
Both OPC and PPC produce durable concrete. However, PPC is generally considered to be more durable than OPC, especially in aggressive environments such as marine environments and sulfate-rich soils. This is because the pozzolanic materials in PPC help to reduce the permeability of concrete and improve its resistance to chemical attack.
Both OPC and PPC have good workability. However, PPC is generally considered to be more workable than OPC. This is because the pozzolanic materials in PPC help to lubricate the concrete mix and improve its flowability.
PPC produces more impermeable concrete than OPC. The permeability of cement depends on the fineness of the cement. According to a thumb rule, lower fineness means higher permeability. Here, OPC’s fineness is 225 m2/kg whereas PPC’s is 300 m2/kg.
Heat Generation During Hydration
OPC generates more heat during hydration than PPC. This is because the hydration of OPC is a more exothermic process. The high heat of hydration of OPC can lead to cracking in concrete structures, especially in mass concreting applications.
OPC has a shorter setting time than PPC. This is because the hydration of OPC is a faster process. The initial setting time of OPC and PPC is 30 minutes whereas the final setting time of OPC is 280 minutes and PPC’s 600 minutes.
The faster setting time of OPC makes it suitable for applications where early strength is required.
Resistance Against Chemical Reaction
PPC is more resistant to chemical attack than OPC. This is because the pozzolanic materials in PPC react with calcium hydroxide to form cementitious compounds that are more resistant to chemical attack. The high resistance to chemical attack of PPC makes it suitable for use in aggressive environments such as marine environments and sulfate-rich soils.
The production of OPC has a higher environmental impact than the production of PPC. This is because the production of OPC requires more energy and produces more greenhouse gases. The lower environmental impact of PPC is due to the use of pozzolanic materials, it reduces the carbon emission by 10 to 20%.
Summary of the Difference Between OPC and P
|Materials Used||Limestone, clay, and gypsum||OPC clinker and pozzolanic materials|
|Strength||Higher initial strength||Higher long-term strength|
|Durability||Good in chemical environments||More durable, especially in aggressive conditions|
|Workability||Good workability||More workable due to pozzolanic materials|
|Permeability||More permeable||Less permeable with finer particles|
|Heat Generation||More heat during hydration||Less heat, suitable for heat-sensitive projects|
|Setting Time||Quick setting||Extended setting time for precision work|
|Chemical Resistance||Good resistance||Better resistance due to pozzolanic materials|
|Environmental Impact||Higher impact||Lower impact – reduces carbon emissions by 10-20%|
When You Should Use OPC?
OPC is generally used in applications where high early strength is required because it hydrates more quickly than PPC. This means that OPC concrete will reach its full strength sooner, which is important for applications where the concrete structure needs to be able to bear loads quickly.
Some specific examples of applications where OPC is commonly used include:
- Precast concrete products: Precast concrete products, such as concrete beams, columns, and slabs, are often made with OPC because they need to be able to be transported and erected quickly.
- Concrete pipes: Concrete pipes are used to transport water, sewage, and other fluids. OPC is often used for concrete pipes because it produces durable concrete that is resistant to corrosion.
- Concrete blocks: Concrete blocks are used to build foundations, walls, and other structures. OPC is often used for concrete blocks because it produces strong concrete that is resistant to cracking.
- Aggressive environments: OPC is also used in applications where the concrete will be exposed to aggressive environments, such as marine environments and sulfate-rich soils. This is because OPC concrete is more resistant to chemical attack than PPC concrete.
Here are some additional benefits of using OPC:
- High strength: OPC concrete is one of the strongest types of concrete available.
- Durability: OPC concrete is durable and can withstand heavy loads and harsh weather conditions.
- Versatility: OPC can be used in a wide variety of applications, from small residential projects to large commercial and industrial projects.
When You Should Use PPC?
PPC is generally used in applications where high long-term strength is required because it hydrates more slowly than OPC. This means that PPC concrete will take longer to reach its full strength, but it will ultimately have a higher strength than OPC concrete.
Some specific examples of applications where PPC is commonly used include:
- Dams: Dams are large concrete structures that are subjected to high loads of water. PPC is often used for dams because it produces durable concrete that is resistant to cracking and chemical attack.
- Bridges: Bridges are another type of concrete structure that is subjected to high loads. PPC is often used for bridges because it produces strong concrete that is resistant to fatigue and corrosion.
- Mass concrete structures: Mass concrete structures are large concrete structures that are poured all at once. PPC is often used for mass concrete structures because it generates less heat during hydration than OPC, which reduces the risk of cracking.
- Aggressive environments: PPC is also used in applications where the concrete will be exposed to aggressive environments, such as marine environments and sulfate-rich soils. This is because PPC concrete is more resistant to chemical attack than OPC concrete.
Here are some additional benefits of using PPC:
- Lower cost: PPC is generally cheaper than OPC.
- Lower environmental impact: The production of PPC has a lower environmental impact than the production of OPC.
- Better workability: PPC concrete is more workable than OPC concrete, which means that it is easier to place and finish.
OPC and PPC are both widely used types of cement in construction. Both have their own advantages and disadvantages. OPC is the most common type of cement used worldwide, but PPC is becoming increasingly popular due to its lower environmental impact and better durability.
Which type of cement to use depends on the specific requirements of the project. If high early strength is required, then OPC is the better choice. If high long-term strength and durability are required, then PPC is the better choice.