What Is PCC In Construction?
The term PCC is commonly used in civil engineering and construction which refers to Plain Cement Concrete.
PCC is a mixture of cement, fine aggregate or coarse aggregate, and water without steel reinforcement. It is generally used for flooring, roads, and retaining walls but not for columns, slabs, and beams, etc because it can’t carry load or tensile force.
Plain cement concrete is laid on the soil surface to avoid direct contact of reinforcement with soil and water.
Purpose Of Using PCC
1. To prevent direct contact of reinforcement with soil, because when moisture available in the soil is absorbed by R.C.C result in causing corrosion of steel reinforcement.
2. PCC provides a leveled base which helps to set out the structure above in an easier way.
3. PCC prevents loss of water from RCC, as the earth is likely to absorb water from the RCC.
Based on the load-carrying capacity different PCC grades are used such as M5, M7.5, M10, and M15.
Where M stands for Mix while the number represents the compressive strength of particular grade testing after 28 days curing, a Detailed tabular is provided below.
Most commonly M15 grade is used as its compressive strength remains in between ordinary and standard concrete.
As you can see above, the ratios of particular grades but what does 1:2:4 mean?
1:2:4 is the mix ratio of M15 concrete which means, a concrete mixture is done by adding 1 part of cement, 2 parts of fine aggregate (sand), and 4 parts of coarse aggregate.
Generally, IS code provides nominal and standard PCC mix ratio for different constructions but one must consider Mix ratio based on the design and testing of the work.
Along with cement, sand, and coarse aggregate, the water ratio must be considered based on the mix.
Methods of Mixing PCC
PCC can be mixed in two ways either by manual or by using machines.
1. Hand Mixing
Usually, hand mixing is practiced in the village area.
Hand mixing is only suitable for small quantities.
Before mixing one must ensure the base must be clean and free from any unwanted debris.
In hand mixing, Sand and cement is mixed first then the coarse aggregate is added and finally a required amount of water is added to attain the desired concrete mixture.
Refer to the Below image for the hand mixing procedure
2. Machine Mixing
In machine mixing for PCC, a machine is used for mixing the concrete components to attain the desired concrete mixture. Machine mixing is highly effective as the time taken for mixing is less than hand mixing and the mixture is uniformly mixed.
Machine mixing is generally used for medium-scale projects.
There are different types of machines are available in the market as you can see below image.
The Procedure Of Machine Mixing Of Concrete
1. Add 1-2 buckets of water to make the internal surface of the mixer wet.
2. Then coarse aggregate is placed followed by sand and cement.
3. The ingredients must be placed alternatively, instead of placing all at a time.
4. The ingredients must be mixed in a dry state for 2-3 minutes.
5. Now pour the required quantity of water while checking on the consistency of the concrete mixture, if the consistency of concrete is more watery it may reduce the strength.
6. After mixing the ingredients thoroughly for two minutes now pour it on a sheet or surface with no debris.
Uses of PCC (Plain Cement Concrete)
PCC is commonly used in the following situations:
- Rigid impervious bed in the foundation.
- Canal construction.
- Flooring, pavement, CC roads.
- Stone masonry works.
- Retaining walls, storm drains.
Do’s and Don’ts of PCC Works
1. PCC shuttering must be placed correctly without any gaps or leaks and the size of the shuttering must be exact size and thickness to attain uniformity from all corners.
2. Add water according to the required water-cement ratio using a bucket in a measured volume avoid using a pipe.
3. Clean the surface before pouring concrete so no debris gets mixed with concrete.
4. If the quantity of water is more in concrete, then it must be de-watered at the same time during concreting.
5. Make sure you level the concrete as soon as the concrete is poured.
6. In case of flooring, if the area is large then several T points are made to attain a uniform level.
1. Avoid mixing concrete with bare hands
2. Do not pour PCC without proper formwork.
3. Concrete should not be poured from a height above 1.5m as it leads to segregation.
4. Do not use crooked channels, use smooth channels to attain a smooth finish.
5. Don’t pour concrete if any of the material is in excess quantity than the prescribed ratio.
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