Plain cement concrete (PCC)- Materials, Properties, and Mixing

Plain cement concrete (PCC) is a hardened mass obtained from a mixture of cement, sand, gravel, and water in definite proportions. It does not contain a steel rod. If steel is kept in the concrete then it is called Reinforced cement concrete (RCC).

These ingredients are mixed together in a definite proportion to form a plastic mass which is poured into desired shape moulds called as forms.

This plastic mass hardens on setting and we get PCC. The hardening of this mixture is caused by a chemical reaction between the cement and water.

Plain cement concrete(PCC)  has good compressive strength and very little tensile strength, thus limiting its use in construction. Plain concrete is used where good compressive strength and weight are the main requirements and tensile stresses are very low.

Read also, What is PCC DPC and RCC in civil engineering | RCC and PCC

PCC is done to form a leveled surface before starting any R.C.C. or masonry work directly on the excavated soil. PCC is also called cement concrete or binding concrete.

Materials used in plain cement concrete

Cement

 It is the chemically active ingredient of concrete. It shows binding properties after reacting with water. It consists of silicates and aluminates of calcium which form a hardened mass after mixing with water.  Portland pozzolana cement is generally used for plain cement concrete.

Sand

Sand is used for concrete work should be hard, durable, strong, well-graded, clean should meet the requirements specified for its use.

Aggregate

The bulk concrete is made up of aggregates. Aggregates are inert material or chemically inactive material like crushed rock, sand, broken bricks, gravel, etc. Aggregate size less than 4.75 mm is known as fine aggregate and aggregate of size more than 4.75 mm size are called coarse aggregate.

Fine aggregate acts as a filler between the coarse aggregate and coarse aggregate give the strength to concrete and provide workability to the concrete mix. The aggregate should be hard, strong, durable, and well graded.

Water

Water is required for providing workability to concrete and also for the chemical reaction of cement. The water used for mixing and curing of concrete should be clean and free from injurious amounts of acids, alkalis, salts, or other chemical substances, which can harm concrete or steel.

Objective of (PCC)

The objective of PCC is to arrange a firm impermeable bed to RCC in the foundation where the soil is soft and flexible. Plain cement concrete mostly applied over brick flat soling or devoid of brick flat soiling.

The thickness of PCC: The thickness of PCC is generally 5 cm over brick flat soling (BFS). If you don’t use brick flat soling below plain cement concrete (PCC) then the thickness should be 7.5 cm.

When the PCC used in the car parking area then the thickness should be 7.5 cm over brick flat soling (BFS).

The ratio of materials in PCC:  The ratio of cement, sand, and brick chips in the foundation should be 1:3:6. But if it is applied in the car parking area, the ratio will be changed to 1:2:4.

Properties of plain cement concrete

1. Compressive strength: The compressive strength of PCC lies between 200 to 500 Kg/cm².
2. Tensile strength: The tensile strength of plain cement concrete lies between 50 to 100 Kg/cm².
3. Density: The density of concrete ranges from 2200 Kg/m³ to 2400 Kg/m³.
4. Durability: It is more durable.

Uses of PCC

1. As a base below all types of foundations to provide a hard and level surface for laying the foundation.
2. As b base below the floor on the ground floor. At the plinth level, PCC provides a hard and level surface for laying floor tiles.
3. Below load-bearing walls as a foundation.
4. At plinth level to act as a damp proof course (DPC)
5. As coping over top of parapet walls to protect the wall from rain.
6. For pavement and roads
7. For mass concrete structure such as retaining walls.

Proportioning

1. The proportioning is done based on a given specification or requirement. Generally M10 (1:3:6) or M15 (1:2:4) mix is used.
2. The measurement of materials is done by volume batching or weight batching.
3. Coarse aggregate and sand shall be measured by measuring box in volume batching of size 30 cm x 30 cm x 38 cm equivalent to one bag cement of 1/30 m3 or 0.035 m3.
4. On the basis of dry volume, sand is measured.
5. While measuring the aggregate, ramming, sacking, or hammering shall not be done.

Mixing of plain cement concrete (PCC)

Mixing of PCC can be done either manually or by using machine.

Hand mixing

1. Plain cement concrete is allowed to be done by hand mixing only for small works.
2. The base must be clean, watertight slab, or a steel platform on which the concrete is mixed.
3. Sand and cement are mixed with coarse aggregate. Lastly, water is added and the mixture is mixed properly.

Machine mixing

1. The quantity of dry aggregate, fine aggregate, and cement is measured and should be placed in their respective hoppers.
2. The dry materials should be mixed in the mixture and water is added while the drum is motion.
3. The mixing should have a plastic mix of uniform color.

Advantage of laying PCC

1. As cover blocks rest on a firm PCC, required cover to bottom reinforcement is ensured.
2. Reinforcement bars are placed in steel. Reinforcement steel bars are never placed in contact with the ground.
3. Concrete never bond with ground soil (clay); Plain cement concrete (PCC) as a barrier to the soil.

I hope this article remains helpful for you.

Happy Learning – Civil Concept

Contributed by,

Civil Engineer – Pradip Thakur

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