Concrete and Steel are one of the most common construction materials even in today, Steel Structures Vs Concrete Structures is an attempt to compare advantages and disadvantages of both materials from constriction and maintenance point of view.
Concrete is the second most used material for construction after water in the world. Concrete structure can take compressive stresses very effectively but it cannot take tensile stresses. So the reinforcement is given to concrete where the structure is under the tension load. Concrete is widely used in today construction industry today because of its durability and compatibility. Moreover concrete can be mould in any shape which make it a very useful.
Concrete structure can be made with many different ways. Some are given below:
Plain Cement Concrete
Plain cement concrete is a hardened mass obtained from a mixture of cement, sand, gravel, and water in definite proportion. The concrete structure made by using the plain cement concrete has good compressive strength but very little tensile strength, thus limiting its use in construction. Plain concrete is used where good compressive strength and weight are the main requirement and the tensile stresses are very low. For eg: In roads, concrete blocks for walls, etc
Reinforced cement concrete
Plain cement concrete has very low tensile strength. To improve the tensile strength of concrete some sort of requirement is needed which can take up the tensile stresses developed in the structure. The most common type of reinforcement is in the form of steel bars which are quite strong in tension. The reinforced concrete has innumerable uses in construction. For eg: in building, flyovers, water tanks, etc.
In ordinary reinforced cement concrete, compressive stresses are taken up by concrete and tensile stresses by steel alone. The concrete below the neutral axis is ignored since it is weak in tension. Although steel takes up the tensile stresses, the concrete in the tensile zone develops minute cracks. The load carrying capacity of such concrete sections can be increased if steel and concrete both are stressed before the application of external loads. This is the concept of prestress concrete.
The prestressed concrete is uses in the structures where tension develops or the structure is subjected to vibrations, impact and shock like girders, bridges, railway sleepers, electric poles, gravity dam, etc.
Advantages of concrete structure
- Ingredients used in concrete such as, cement, aggregates and water are readily available and cheap.
- Concrete assumes the shape of its mould and it can be poured and cast into any shape.
- Concrete when used along with reinforcement, is capable of taking bending and tension forces.
- The compressive strength of concrete is very high making it reliable to be used for structures and components under compressive loads.
- The break through in prestressed concrete applications enables reduced section sizes and reduction in self-weight.
- Due to massive nature, high unit weight and water tightness, concrete can be used for water retaining structures like Dams.
Disadvantages of concrete structure
- Due to drying shrinkage and moisture expansion concrete may crack. Therefore construction joints are provided to avoid these types of cracks.
- Concrete is weak in tension.
- High Self weight of concrete is not always favorable for seismic prone structures.
- Sustained loads develop creep in structures.
- If salts are present in the concrete then it will results in the efflorescence in concrete structure
The material steel, is an alloy of iron and carbon percentage (small percentage) and other elements e.g. silicon, phosphorous and sulphur in varying percentage. Depending upon the chemicals composition, the different types of steel are classified as mild steel, medium carbon steel, high carbon steel, low alloy steel and high alloy steel. The mild steel, medium carbon steel and low alloy steel are generally used for steel structures.
The steel which is used for the manufacture of rolled steel structural, fastenings and other elements for use in structural steel works is called structural steel. Structural steel to be used for building purposes, has been standardized by Indian Standard Institution (I.S.I)I and specification of various qualities are contained in the following standards(as per I.S 800-1984)
- IS : 226-1975 Structural steel (standard quality)
- IS : 1977-1975 Structural steel (ordinary quality)
- IS : 2062-1984 Weldable structural steel (Fusion welding)
- IS : 961-1975 Structural steel (High tensile)
- IS : 960-1977 weldable structural steel (medium and high strength quality)
Standard quality steel (mild steel)steel is the most commonly used steel for general construction purposes of buildings, railway bridges, transmission line towers, industrial structures etc.
Advantage of steel structure
- Lightness: The steel structures are very light in comparison to other structures such as concrete structures
- High strength and stiffness per weight: The steel are very stiff and they possess a high strength to weight ratio.
- Ease of fabrication and mass production: It is eay to fabricate a steel structure so it is generally used for mass construction. The steel members can be easily replaced, assembled and disassembled.
- Fast and easy erection and installation: The steel structures can be erected very easily and faster than many other structures. The steel structures can be used soon after their erection
- No sudden failure: Steel being a ductile material does not have sudden failure, rather it gives clear indication by deflection before failure.
- Formwork unneeded: Unlike concrete structures, the steel structure does not need any kind of formwork
- Termite proof and rot proof: Unlike timber the steel doesn’t get corroded by the action of termite and it is pretty much resistance to rusting, if good quality steel is used.
- Economy in transportation and handling: Because of being lightweight the steel structures are easy to transport and handling.
Disadvantages of steel structure
- Susceptibility to corrosion: The steel members are prone to corrosion, therefore they require some frequent treatment like painting and other methods for their protection.
- High initial cost: The initial cost of steel structure is high.
- Skilled labor : The steel structure require skilled labor for their construction.
Steel Structures Vs Concrete Structures
|Point of difference||Concrete structure||Steel structure|
|Durability||The concrete structure are more durable|
|The durability of steel structure is adversely affected by weather condition and rusting|
|Earthquake resistance||The concrete structure are brittle so they are less earthquake resistance.||Steel Structure can withstand earthquake more effectively than concrete structure|
|Load carrying capacity||In the comparison to the steel the load carrying capacity of the concrete is low.|
|The load carrying capacity of steel structure is good|
|The scrap value of concrete is nil|
|The scrap value of steel is good|
|Self-weight||The self-weight of concrete is more|
|The steel is 60% lighter than the concrete|
|Foundation||The foundation for the concrete structure should be strong because of the larger weight of concrete||The steel structure can be made without foundation|
|Construction time||The concrete structure generally needed 28 days before they are ready to use||The steel structure are fast in their erection and can be used soon after their erection|
|Labour||It requires less skilled labor||It requires more skilled labor|
|Cost||The cost of construction is less||The cost of construction is more|
|Joining||The joints such as construction joint, expansion joint, contraction joint, etc are needed in concrete structure||The steel component are joined by using rivets, welding, nuts & bolts, etc. in steel structure|