Introduction to reinforced concrete and design methods

Introduction to reinforced concrete and design methods.

Introduction :

Concrete is one of the most common building materials used for construction of engineering structures like buildings, bridges, pavements, dams, hydraulic structures, water tanks, auditoriums, swimming pools and list goes on.

Why concrete is required in construction?

• It has high compressive strength.
• It can be easily mould into any shape & size.
• It can resist fire & corrosion.
• It is relatively cheaper & widely available.

• Draw backs are it can't resist the significant tension.
• The tensile strength of concrete is about 10% of its compressive strength.
• It is used where tensile stresses/ strains never develop.
• Ex: Pedestals, Mass, Concreting in dams.

What are the types of concrete ?

Types of concrete used in structure are three namely.

• Plain concrete.
• Reinforced concrete.
• Pre-stressed concrete.

Plain concrete :

Plain concrete consists of cement, sand , stone aggregates,water and super plasticizer.

What is reinforced concrete :

Reinforce means strengthening of material. Concrete has high compressive strength, but its tensile strength is very low.

In any situation where tensile stresses are developed it is strengthened by steel bars forming a composite material which is known as Reinforced cement concrete.

What is prestressed concrete ?

prestressed concrete where the tendons are tensioned prior to the concrete being cast.The concrete bonds to the tendons as it cures, following which the end-anchoring of the tendons is released, and the tendon tension forces are transferred to the concrete as compression by static friction.

What are the type of concrete based on strength ?

• Ordinary concrete: M10 to M20.
• Standard concrete: M25 to M55.
• High strength concrete: M60 to M80.

What are the properties of hardened concrete ?

• Compressive strength of concrete: The characteristic compressive strength of 150 mm size cube at the age of 28 days expressed in N/mm².
• Characteristic strength of cube: The strength below which not more than 5% of test results are expected to fall.
• As per IS 456:2000, the minimum grade of concrete to be used in RCC M20 ( General construction works not sea constructions ).
• M30 strength concrete should be employed for sea construction works.

What do you meant by M-20 ?

M-stands for Mix and 20 stands for cube compressive strength of 150 mm size cube at the age of 28 days expressed in N/mm².