What Is PCC Concrete?
Concrete is widely used for architecture or infrastructure work all over the world to meet different needs.
RCC (Reinforced Cement Concrete) and PCC Concrete (Plain Cement Concrete) are widely used as required on any construction site.
RCC work means reinforced cement concrete work. In which reinforcement is inserted into the structure to resist the required tensile strength. And when reinforcement is not used in PCC concrete work.
PCC is important for building a foundation. PCC concrete is poured on the ground surface to avoid direct contact with the reinforcement of the soil and water in the concrete.
Plain Cement concrete is a surface prepared in the right proportions of cement, fine aggregate (sand), and coarse aggregate. In which steel is not provided.
Before starting any RCC or masonry work, concreting is done directly on the excavated ground by PCC concrete to create a flat surface.
Plain cement concrete is also commonly referred to as “cement concrete (CC)”.
PCC Concrete Mix Ratio
The PCC concrete mix ratio is 1: 3: 6. The mixture of concrete consists of 1 part of cement, 3 parts of sand, and 6 parts of aggregate. The purpose of PCC for any construction is to prepare a level surface for footing.
Material Used in Plain Cement Concrete
The following components are used to make plain cement concrete,
1. Cement
Portland Pozzolana Cement (P.P.C) is suitable for plain cement concrete. It should have specifications as required. PCC concrete should have compressive stress and fineness.
2. Coarse Aggregates
The coarse aggregate used in PCC Concrete should be pieces of good quality granite, and hard, durable aggregate. In addition, it should be free from dust, dirt, and other solids. The size of the broken stone should be smaller than 20 mm.
Coarse Aggregates used for PCC Concrete should be retained in a 5 mm square mesh. So that the void of Aggregate in concrete does not exceed 42%.
3. Fine Aggregates
Hard, sharp, and angular grain sand is used in PCC concrete as fine aggregate. This type of sand should pass through a 5 mm square mesh screen.
The sand used for PCC concrete should be in accordance with the standard specifications. The sand used for PCC Concrete should be free from dust, dirt, and organic matter. Also, sea sand should not be used as fine aggregate.
4. Water
The water used for PCC concrete should be pure clean and reasonably free of harmful substances. These harmful substances include oils, alkalis, acids, salts, and vegetable growths.
Uses of PCC Concrete
PCC Concrete is used to create a level surface for foundations. In addition, its other uses are as follows:
- PCC concrete is made of concrete for plinth protection.
- PCC concrete is commonly used to obtain base surfaces in the construction of column foundations, large gravity dams, etc.
- PCC Concrete is used in construction as a layer for rigid pavement (reinforcement-less rigid pavement).
- PCC concrete can be used in the construction of small canals.
- PCC Concrete is also used as a foundation in some stone or brickwork.
- It is used as the flooring of large industries.
Methods for Mixing of PCC Concrete
Concrete is produced by proper mixing of different components together. To get proper strength of concrete, it is necessary to mix concrete components like water, aggregate, cement in proper proportions.
Concrete can be manufactured by the following three methods to achieve good quality and workability.
1. Machine Mixing of PCC Concrete
Machine mixing is the process of PCC mixing concrete components properly. Mixing of concrete components by machine mixing can be done with better quality than hand mixing. Its use is effective for small building work.
Concrete Mixing Process by Machine
First, the concrete mixer machine is turned on. The internal surface of the drum is then wetted by pouring water into it.
In a mixer machine, the components for PCC Concrete are poured into the drum according to their ratio.
About thirty rotations are performed to mix the concrete components into a homogeneous state. The production of 1 batch of concrete requires about 2 minutes to mix properly.
2. Ready Mix Concrete
In India, concrete is traditionally produced on-site, usually through the use of manpower. However, due to the advantages of ready mix concrete in modern times, its use has started increasing rapidly.
This method can speed up the construction process. In addition, it can be easily done in crowded areas, at night in concreting work, in large construction sites, etc.
Ready mix concrete is especially used in dense areas or in road construction. Very useful where proper space for the plant is not available and there is no space for stock of concrete components. High-quality concrete can be achieved by this method. Because Concrete for this type of concrete is produced by a mechanized central batching plant.
In ready-mix concrete, it is able to control the water/cement ratio in concrete compared to other types of mixing methods.
The required amount of fly ash and cement can be mixed properly. The use of ready-mix concrete helps in speeding up the construction and maintaining the proper quality of concrete.
Also Read : Important of Cement Test | Type of Cement Test
3. Hand Mixing Concrete Method
In the hand mixing process is very difficult to mix the concrete components properly. Concrete mixing by hand mixing is used only for small works. In addition, the hand mixing process can be done where the demand for concrete is low and the quality control is low.
No machinery is required for this type of mixing. Achieving the right mix of concrete through the hand mixing process is difficult and requires great strength.
Process of Hand Mixing of Concrete
Various components of concrete are hand mixed in the tray as a rigid, clean, and non-porous base.
A measured amount of sand and aggregate is spread in the tray. And then the cement is emptied on top of it.
The mixing process is continued until the components of the concrete achieve the same color and consistency in the dry state. The last amount of water is then added to the dry mix of concrete.
Dos and Don’ts of PCC Works
Dos
- If the water table at the PCC concrete laying site is high, de-watering should be done during concreting.
- If the PCC concreting space on the site is at a greater depth then a chute or pipe chute should be used for laying the concrete.
- Shuttering should be done for specific sizes and thicknesses for PCC concrete as per the drawing.
- Any loose material on the edge of the pit should be removed. So that no loose material breaks into the pit during concreting.
- Water should be mixed in PCC concrete by bucket according to the quantity measured in W/C (water/cement) ratio.
Don’ts
- If the depth of the pit is more than 1.5 m, do not pour concrete directly into the pit.
- Do not allow PCC Concrete for foundation without formwork. Because without formwork, concrete is wasted.
- Do not mix PCC concrete material on the direct ground.
- Additional cement mortar should not be used for a smooth finish on top of the PCC.
- PCC should not be done without leveling and compaction of the soil on site.
Laying of Plain Cement Concrete
PCC concrete is laid in a thickness of 100mm to 150mm to prepare a surface for the foundation. Complete compaction of PCC concrete is done through mechanical vibrators.
Sometimes hand compaction is done with the help of wood. So that the concrete is fully compacted and properly aligned in the formwork.
The compact surface of PCC Concrete is then smoothly finished using a wooden float.
Curing of PCC Concrete
The surface is sprayed with water 24 hours after laying concrete for PCC concrete. The curing procedure is performed for at least 14 days.
Also Read : What Is the Grade Beam? | The Construction Process of Grade Beam | Advantages & Disadvantagesof Grade Beam
Advantages & Disadvantages of PCC Concrete
Advantages of PCC Concrete
- PCC Concrete is easy to place in a steel cage for the footing of the foundation. So that the productivity of the work is increased.
- PCC Concrete acts as a barrier with the concrete soil of the footing. So that the Concrete of Footing attaches to the reinforcement and achieves good Strength.
- PCC Concrete creates a finishing surface to provide a cover for reinforcement in footing.
- PCC concrete provides a base for formwork. So that the formwork for footing can be easily, uniformly, and firmly fixed.
- Reinforcement placed on PCC Concrete will never come in contact with the ground.
Disadvantages of PCC Concrete
- PCC concrete starts drying in a short time after laying on the surface. So its surface has to be finished immediately.
- PCC Concrete cannot be kept in RMC trucks for a long time.
- Increased PCC Concrete cannot be used for other Concrete elements.
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