Question

Reinforced Concrete – concept and conditions to be fulfilled.

Answer 1

Reinforced concrerte: Generally Concrete is of two types PCC and RCC

PCC is called Plain cement concrete which is used for DPC below the footing of coloumns and which is generally of M10 ratio.

RCC Reinforced cement concrete is a type of concrete in which reinforced steel bars are used for giving tensile strength for concrete member. RCC members are durable and resistant from environmental factors of corosion over a period of time.

Generally available Reinforced steel in market are Fe415,Fe500,Fe550. The number represents tensile strength of the steel member. TMT bars are now become popular which are thermally mechanically treated bars. Which are produced by rapid heating and harding technique to increase the ductability and tensile nature of the bars. Usually the full length of the steel is 12mts.

The Reinforced concrete is used in order to increase durability of structure and increasing bearing capcity without failure.

The factors effecrting the strength and durabilitty of RCC are as Follows:

a)The selection of raw materials for the concrete ie the cement, sand, coarse aggregate and reinforcement: The finner the cement and sand harder the concrete mix, also flaky aggregates are prefferred over round and soft.The steel should be treated with zinc coating for anti termite resistance.

b)The water cement ratio: To achieve high strength concrete the water cement ratio to be maintained is minimal, this can be achieved by using admixtures such as plasticizers.

c)To maintain minimal clear cover: The clear cover for the reinforcement plays a important role for durability of structure a min of 10-15mm clear cover to be maintained for slabs, 25mm-min should be maintained for beams and columns, for footings min of 40mm is to be maintained.

d)The consideration of load factors and selection of materials and dia of steel is very important. The loads generally would be dead load + Live load + Earthquake factors + Wind loads + Factor of safety.

The above mentioned conditions to be fullfilled in order to attain high strength and durability of concrete.

Also, Placing of Concrete and compaction plays a vital role in attaining high strength. The concrete should not be placed from not more than 1.5m as that concrete gets segregated. The concrete should be compacted well with the use of concrete vibrators to remove air voids and to settle.

Concrete Tests have to be conducted on fresh concrete before placing such as workability test at site by slump test and also compaction factor test.