Types of cement concrete

TYPES OF CEMENT CONCRETE

1. ACCORDING TO THE BINDING MATERIAL

1. Cement Concrete: Cement Concrete is explained in Sections 1, 2, 3, and 4 of 3(F).

2. Lime Concrete

Ingredients: Lime Concrete consists of lime, a fine aggregate and coarse aggregate, mixed in suitable proportions in addition to water. Here, lime is the binding material. Sand or surkhi is used as fine aggregate. Broken stone / Broken brick is used as the coarse aggregate.

Advantages: It resists weathering effects. It is durable. It is cheaper than cement concrete.

Disadvantages: Lime concrete has less strength than cement concrete. Lime causes rashes on human skin. Hence, persons working with lime concrete must be provided with protecting rubber gloves and rubber gum boots.

Uses: It is used for foundation bases of load bearing walls, columns and under layers of floors.

2. ACCORDING TO THE DESIGN

1. Plain Cement Concrete (P.C.C.) / Cement Concrete / Concrete

Cement concrete with no reinforcement is called Plain Cement Concrete or Cement Concrete or simply Concrete.

Constituents, Properties,  Advantages & Disadvantages and Uses: Refer Sections 1, 2, 3 & 4.

2. Reinforced Cement Concrete (R.C.C.)

Concrete is good in resisting compressive stress, but very weak in tensile stress. However, in tensile zone, hair cracks in concrete are unavoidable. Hence, reinforcement is provided in the concrete. The reinforcement used is steel, since tensile strength of steel is very high and the bond between steel and concrete is good.

Reinforcements are in the form of Mild Steel or Ribbed Steel Bars of diameter 6 to 32 mm. A cage of reinforcements is prepared as per design requirements, kept in a form work and then concrete is poured. After the concrete hardens, the form work is removed. The composite material of steel and concrete, now called R.C.C. acts as a structural member. It can resist tensile as well as compressive stresses efficiently.

Proportions of Ingredients: 1 Part cement : 1 to 2 Parts fine sand : 2 to 4 Parts crushed stone, in addition to reinforcement.

Properties

1. High Compressive and Tensile Strengths: Plain concrete has a high compressive strength, but weak in tension. Steel bar has a high tensile strength. Its compressive strength is low due to buckling effect. Hence, by reinforcing concrete with steel, the shortcoming of both the components is made up.

2. Hair Cracks: The hair cracks developed should be very negligible.

3. No Cracks: R.C.C. does not develop cracks.

4. Water-tightness: R.C.C. is a water-tight material. Moisture does not penetrate well compacted reinforced concrete.

5. Rigid Joints: R.C.C. structural members provide rigid joints.

6. Withstanding Load: R.C.C. structure can be designed to take any load.

7. Moulding: R.C.C. is moulded to desired shape and size.

8. Durability: Durability of R.C.C. is very good.

9. Corrosion of Steel: There should be proper cover to reinforcement so that corrosion of steel is prevented.

10. Anti-termite: R.C.C. is not affected by termites, vermins, etc.

11. Fire Resistant: R.C.C. is a good fire resistant.

Uses

1. Structural Elements in Building: Structural elements in a building where R.C.C. is used are: Footings, Columns, Beams, Lintels, Sun Shades, Roof Slabs, Curved Roofs, Stairs, etc.

2. Monolithic Construction: R.C.C. is used in monolithic construction. This increases the rigidity and stability of the structure.

3. Storage Structures: R.C.C. is used for the construction of storage structures like Water Tanks, Bins, Silos, Bunkers, Dams, etc.

4. Big Structures: R.C.C. is used for the constructions of big structures like Bridges, Retaining Walls, Underwater Structures, Docks and Harbours, etc.

5. Pre-casting: R.C.C. is used for pre-casting Railway Sleepers, Electric Poles, etc.

6. Tall Structures: R.C.C. is used for tall structures like Multi-storey Buildings, Towers, Chimneys, etc.

7. Paving: R.C.C. is used for paving Highways, City Roads, Airports, etc.

8. Atomic Plants: R.C.C. is used in the construction of nuclear reactor, because of its highshielding capacity from radio activity.

3. Pre-Stressed Cement Concrete

The cement concrete, in which high compressive stresses are artificially induced before placing, is known as Pre-Stressed Concrete. In this concrete, High Tensile Steel Wires are used as reinforcement, instead of MS (Mild Steel) Bars.

There are two types of pre-stressing: (i) Pre-tensioning and (ii) Post-tensioning. In pre-tensioning method, the wires are stressed initially. The concrete is cast in the mould built around the wires. The reinforcement wires are then released after the concrete attains its strength. The tendency of the wires to return to their original length, sets up compressive stress in the concrete. This helps the concrete to resist more tensile stresses. In post-tensioning, the reinforcement wires are placed inside the concrete and then stressed.

Advantages

(i) The use of pre-stressed concrete results in saving of concrete and steel by about 50% and 75% respectively, compared to R.C.C.

(ii) It can take up high tensile and compressive stresses without crack formation.

Uses: It is used for long-span bridge construction, constructions of pavements, poles, piles, rail-road sleepers, television towers, etc.