Steel is a very strong and durable construction material. However, its solid properties and strength cannot save it from corrosion. The fact that steel corrodes with time, means there is a considerable breach in its strength and durability. If steel corrodes over time, the building or the structure it was used in gets potentially put at risk and loses its overall structure strength with time. It is, therefore, necessary to make sure that steel structures are checked for signs of corrosion and should be taken care of accordingly.
What is steel corrosion?
Civil engineers often define corrosion as the chemical or electrochemical reaction between a material, usually metal and its environment, which causes deterioration of the material and its properties over time.
For steel embedded in concrete, corrosion results in the formation of oxide that has 2 to 4 times the volume of the original steel and the loss of its optimal mechanical properties. Corrosion also produces peeling and voids in the surface of the reinforcing steel, reducing the resistant capacity as a result of the reduction of the cross-section.
Why is the corrosion of steel a concern?
Reinforced concrete uses steel to provide tensile strength properties that are necessary for structural concrete. This avoids the failure of concrete structures that are subject to pressure and bending stress due to traffic, winds, dead loads and thermal cycles.
However, when the reinforcement corrodes, rust formation leads to loss of adhesion between steel and concrete and subsequent delamination and exfoliation. If this has been left unchecked, the integrity of the structure may be affected. The reduction of the cross-sectional area of the steel reduces its resistant capacity. This is especially harmful in the performance of high elastic limit cables in prestressed concrete.
Why does steel corrode in concrete?
Steel, when combined with concrete, is usually in a passive condition, not corroded. However, steel-reinforced concrete is frequently used in harsh environments where seawater or deicing salts are present. When the chlorides make their way inside the concrete, they cause the passive layer of protection of steel to rupture, causing it to rust and be flattened.
The carbonation of concrete is another cause of corrosion of steel. Under these conditions, the steel does not remain passive and rapid corrosion begins. The rate of corrosion due to the coating of carbonated concrete is slower than the corrosion induced by chlorides.
Occasionally, the lack of oxygen surrounding the steel bar will cause the metal to dissolve, leading to a low pH liquid property.
How to prevent corrosion?
Civil engineers around the world have created strict quality assurance standards to make sure the materials being used are of good quality. The mixture of materials is another way to keep them strong and retain their strength for a maximum period of time. It is part of the municipality department’s responsibility to make sure building are made within the set standards to keep the buildings safe for the citizens.
It is necessary to protect the concrete from damage by freezing and thawing cycles. Air also reduces exudation and is increased permeability due to exudation water channels. Peeling the concrete surface can accelerate the corrosion damage of embedded reinforcement bars.
A great solution to completely remove the chance of corrosion in building structures is the use of Glass Fiber Reinforced Polymer (GFRP), otherwise known as fiberglass rebar. This is an alternate material used for steel in the construction industry. The qualities of GFRP range from being corrosion free, being lightweight, having a long product life and being stronger than steel itself. Tuf-Bar manufacturers GFRP Fiberglass rebar in Canada. If you’re interested in learning more about fiberglass rebar, please visit our website or contact us.