Plain Cement Concrete (PCC) is a basic construction material in the building industry. It is usually used as a solid base for structural elements, such as foundations, slabs, and pavements, and provides baseline strength and stability to building systems.
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This blog will further discuss what PCC means, its role in construction, what materials go into PCC, mixing ratios, advantages and disadvantages of PCC, as well as best practices in using PCC to ensure the structure performs and lasts during its life cycle.
What is PCC in Construction?
PCC means Plain Cement Concrete, which is the mixture of cement, fine aggregate (sand), coarse aggregate (gravel or crushed stone), and water, similar to Reinforced Cement Concrete (RCC), except it does not include steel reinforcement. PCC is typically used as a base under foundations, floors, and pavements where PCC provides a flat and stable surface.
PCC is typically installed prior to RCC or brickwork to keep soil and moisture or chemicals that may be present below the structure and affecting its strength during its life cycle. The simplicity in its design and execution makes PCC a necessary part of almost all construction projects.
What is the Importance of PCC in Construction?
Foundation Stability: PCC provides a flat, stable base for foundation structures. When PCC is placed on a prepared sub-base, it distributes the load over a large area, reducing the risk of differential settlement, which could cause structural issues at a later time.
Moisture Barrier: Soils can be wet and can allow moisture to migrate up into the foundation and cause mollification or corrosion. PCC will provide a layer of protection and mitigate moisture transmission to the superstructure.
Cost-Effective: PCC is much less expensive than other types of concrete. PCC will not provide the same tensile strength and design applications as RCC, but it will provide excellent compromise strength (in other design applications) for a modest cost.
Durability: PCC is a very dense mass of concrete that can perform in a variety of environmental conditions like rain, temperature and minor loading. The dense character of PCC provides a long service life with minimal maintenance.
Materials Used in Plain Cement Concrete
To achieve good quality PCC, the materials to be used must conform to certain specifications
1. Coarse Aggregate: These consist, generally, of 20mm down-size crushed stones or gravel. It also provides bulk and improves the compressive strength of the concrete. The aggregates should be free of dust or organic impurities and clean, and hard.
2. Fine Aggregate: Sand is used as a fine aggregate. It fills the voids between coarse aggregates and provides a smoother finish when poured. Well-graded river sand or manufactured sand (M-sand) should be used.
3. Cement: It is usually used Ordinary Portland Cement (OPC), which binds the aggregates and gives them strength. The quality of the cement concrete will be is directly affected by the quality of the cement used.
4. Water: The water must be clean and potable. Water that is contaminated can weaken the bond between the cement and aggregates.
5. Concrete Admixtures: Admixtures are not always required in PCC, but if they are used can improve other properties of concrete such as workability, setting time, and durability. Some common concrete admixtures types are: plasticizers, retarders, and waterproofing.
PCC Concrete Ratio
Plain Cement Concrete (PCC) is commonly mixed using various mix proportions depending on the specific application. Here are some of the common mix proportions for PCC:
1:3:6 (Cement:Sand: Aggregate) – Commonly used in flooring, pathways, and light foundations.
1:2:4 – Used in structural elements requiring slightly greater strength.
1:4:8 or 1:5:10 – Used for base leveling and in the mass concreting where great strength is not required. The volumes noted are mixed by volume.
However, weigh batching is considered preferable on larger projects, when required for improved quality control.
The Mixing of Plain Cement Concrete
Mixing the concrete effectively to achieve uniform strength and durability is essential. The steps involved in mixing the concrete are:
1. Batching:
Batching is the measurement of the correct portions of cement, sand, and aggregate. Volume batching uses gauge boxes, and weigh batching weighs the materials to measure the proportions.
2. Dry Mixing:
The dry materials (Cement-Sand-Aggregate) are mixed thoroughly first to properly achieve a uniform color of the dry materials, to ensure a uniform and even distribution of cement.
3. Wet Mixing:
Add water gradually to the dry materials, while turning the mixture continuously until a homogeneous consistency with the dry materials is achieved. Mechanical mixers produce better consistency than hand mixing alone.
4. Consistency Check:
The slump test or flow test measures a defined state of workability of a mixture. For PCC (Plain Cement Concrete), a slump of 25-75mm is typically accepted.
Benefits of Utilizing PCC in Construction
Improved Surface Levelness: PCC is a great choice in order to keep a perfectly flat and clean surface to work with when a trade is ready to install reinforced cement concrete or a floor covering.
Increased Durability: PCC is a strong barrier that protects the supporting soil from dangerous chemicals and water.
Cost Savings: Using PCC can save money in the long run because you will not need as many repairs or replacement from structural failure.
Low Maintenance: PCC surfaces do not require a lot of maintenance. Once installed, PCC is solid and will resist the normal wear and tear of a project without needing a lot of inspections or repairs. This makes PCC a great product for commercial and residential projects.
Fast Project Delivery: Mixing and placing PCC is simple, which allows for quick project delivery times.
Disadvantages of Using PCC in Construction
No Tensile Strength: Lacks resistance to tension and bending.
Limited Heavy-Load Applications: Without reinforcement, PCC is appropriate only for compressing applications.
Shrinkage Cracking: Improper curing/open mixing can lead to cracking.
Limited Applications: Not appropriate for structural members experiencing high-stress loads.
How PCC Works?: Dos and Don’ts
Dos:
- Use fresh and uncontaminated materials.
- Use materials that are mixed thoroughly and uniformly.
- Use the appropriate water-cement ratio.
- Cure the concrete in place for at least 7 days.
- Use admixtures, if you decide to use them, wisely.
Don’ts:
- Do not use saline or dirty water.
- Do not leave cementitious materials in the air for any length of time.
- Do not over-water the mix.
- Do not neglect curing, as it weakens the concrete.
- Do not place PCC on an uneven or dirty surface.
PCC vs. RCC
| Feature | PCC | RCC |
| Composition | Cement, sand, aggregate | Cement, sand, aggregate, steel |
| Strength | Compressive only | Compressive and tensile |
| Cost | Less expensive | More expensive |
| Usage | Base layers, flooring | Beams, columns, slabs |
| Reinforcement | Not included | Includes steel bars |
| Load Handling | Light loads | Heavy and structural loads |
Conclusion
PCC in construction may appear effusive. However, it is critical to the sustainability and stability of whichever structure may be.
Whether it is creating a stable foundation, hydration resistance, working characteristics, or cost savings, without the use of PCC, there is no today’s modern construction.
Specifying good material selection, correct mix ratios, and following good practices in mixing and curing can positively change the quality of your construction project. It may still seem lightweight compared to RCC. However, regardless of its role, it supports everything afterwards.
