(6gh) Enhancement Routes of Corrosion Resistance in Steel-Reinforced Concrete By Using Nanomaterials

Teaching Interests: Materials Engineering

Corrosion of steel in reinforced concrete has been found to be a significant factor leading to premature failure of concrete constructions. The most important causes of corrosion initiation in reinforcing steel are the ingress of chloride ions and carbon dioxide to the steel surface. After initiation of the corrosion process, the corrosion products (iron oxides and hydroxides) are usually deposited in the restricted space in the concrete around the steel. Their formation within this restricted space sets up expansive or tensile stresses, which crack and spall the concrete cover. In the tension zone, concrete will always exhibit cracks. Aggressive liquids and gasses may enter these cracks and they may cause concrete degradation. Because of such cracking, aggressive substances may reach the steel reinforcement and induce corrosion that may lead to further concrete damage and possibly structural failure.

Concrete, that is not exposed to any external influences, provides physical corrosion resistance to steel reinforcement by acting as a barrier, and chemical corrosion resistance as a result of its high pH (usually exhibits a pH between 12.5 and 13.5), which defines the range of electro-chemical potential and pH for a protective passive layer formation on the surface of steel. It is believed that this layer is an ultrathin (<10 nm) protective oxide or hydroxide film that decreases the dissolution rate of steel to negligible levels. For steel embedded in concrete, the dissolution takes place in the limited volume of water solution present in the pores of the concrete surrounding the steel.

Extensive research has been conducted over the last decades to solve the durability and corrosion problem in reinforced concrete. Several methods have been proposed to provide greater corrosion resistance of reinforced concrete system, including: (1) concrete admixtures; (2) corrosion inhibition; (3) electro-chemical methods; and (4) surface treatments (steel and concrete).

Nowadays, the application of nanomaterials to enhancing the conventional concrete properties, such as mechanical strength and durability, has received significant attention. For the purpose of concrete study, the application of nanomaterials must be at least 500 nm in size. Nano-concrete is a concrete that contains nanomaterials or a concrete with nanomaterials added in the mixture, in which the size of the nano-particles is less than 500 nm. This poster presentation will address the impact of nanomaterials on controlling the corrosion rate of reinforced concrete by considering the following methods: 1) nano-admixtures and 2) surface treatments of concrete and steel by nanomaterials.