What is the effect of steel and aluminum, if we use it as reinforcement in structure?
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The use of steel in concrete reinforcement and the effects of it are well known. Steel compensates for the concrete’s weakness in tension and also provided torsional resistance. Furthermore, it gives form slender members to be designed and cuts down the cost of concrete. Also, steel reinforcement is prone to corrosion due to many chemical attacks on concrete and water penetration. This renders the concrete weak and causes it to spall.
Aluminum, on the other hand, though relatively cheaper than steel, is not a desirable reinforcement in concrete. First of all, aluminum reacts with the alkalis in the concrete to form hydrogen. Subsequently, it causes the aluminum to corrode, lose the bond with concrete, the concrete to expand and split, making it utterly unfit without reconstruction. Instead, aluminum has some use in fiber reinforced concrete where scrap aluminum fibers are bent to bond well and mixed into the concrete. These being scraps, have already heavily oxidized and are now not very reactive because of the aluminum oxide deposited on them. Hence, they are resistive to the alkali attack. Fiber-reinforced concrete provides the desired strength with higher durability than reinforced concrete.
Both have different properties & a separate cost which describes below.
We are generally use steel as a reinforcement.
We doesn’t use aluminium because of soft metal property
The main reason why we don’t use aluminum in reinforced concrete structure is because of its property of coefficient of thermal expansion.
The co efficient of thermal expansion for various materials are as follows
Higher the Co efficient of thermal expansion, faster will the corresponding material expand to a given temperature. Therefore, for safety reasons, a reinforcing material of concrete should have the co efficient of thermal expansion nearer to that of concrete (14.5 for concrete).
Aluminum has a high coefficient of thermal expansion of nearly 22.5. So if aluminum is used, then the reinforcements would expand first while the concrete is still intact. This causes unnecessary stresses and lead to the failure of the structure.
Therefore we only use steel for reinforcements as its coefficient of thermal expansion is in the vicinity of that of the concrete.
The effect of steel if we use it as a reinforcement are as follows :-
– Steel is used as reinforcement because of one of its main property i.e. coefficient of thermal expansion. As we know that in summer and winter, concrete used to expands and contract which means during summer steel can also expanded with concrete, and during winter, with concrete steel can also be contracted so, that there is no crack formation and the bond is still strong between concrete and steel. This is one of the main reason for using steel as reinforcement.
– Another reason is steel is good in tension and we know concrete is weak in tension which is negligible.
– Steel has high strength and is more durable.
Generally aluminium is not used as a reinforcement because it have soft metal property.