Corrosion of Reinforced Concrete
Corrosion of reinforced concrete
Contents
1. Introduction 3
2. Corrosion 3 2.1 Chloride attack 4 2.2 Carbonation 5
3. Minimising corrosion 6 3.1 Metallic coatings 6 3.2 Cathodic protection 7 3.3 Other solutions 8 4. Conclusion 8
References 10
List of Figures
2.1 Chloride attack on reinforced concrete…………………………………………....4
2.2 Carbonation attack of RC due to poor concrete cover…………………………….5
3.1 How impressed current cathodic protection stops corrosion ……………………...8
1. Introduction
Reinforced concrete (RC) is an essential construction material that is beneficial for strengthening structures. The steel reinforcement provides tensile stress ‘which plain concrete lacks’ (Chudley and Greeno, 2006). However when combined with the compressive strength of concrete, the overall strength of the composite material is increased. A particular concern for the RC is the corrosion of embedded steel, this can have a detrimental effect to the material and influence its structural integrity and durability therefore it is vital that the steel is protected to prevent the occurrence of corrosion. There are various procedures considered when minimising the risk of corrosion and their effectiveness in doing so has been reviewed.
2. Corrosion
The rate of corrosion in reinforcing steel or rebar is increased significantly when structures are exposed to a ‘highly alkaline environment’ (Tretheway and Chamberlain, 1995) which forms a ‘passive layer’, a ‘thin layer of oxide’ that contributes to a slow rate of corrosion on the steel surface. (Broomfield, 2003)
This subsequently leads to the formation of rust due to the ‘carbonation of the concrete cover and penetration of chlorides’ (Martinez and Andrade, 2009). If ‘water, oxygen and carbon dioxide’ are able to attack the concrete this results in a loss of bond between the concrete and the steel (Tretheway and Chamberlain, 1995). Causing ‘high tensile forces’ from the expanded steel bar and
Contents
1. Introduction 3
2. Corrosion 3 2.1 Chloride attack 4 2.2 Carbonation 5
3. Minimising corrosion 6 3.1 Metallic coatings 6 3.2 Cathodic protection 7 3.3 Other solutions 8 4. Conclusion 8
References 10
List of Figures
2.1 Chloride attack on reinforced concrete…………………………………………....4
2.2 Carbonation attack of RC due to poor concrete cover…………………………….5
3.1 How impressed current cathodic protection stops corrosion ……………………...8
1. Introduction
Reinforced concrete (RC) is an essential construction material that is beneficial for strengthening structures. The steel reinforcement provides tensile stress ‘which plain concrete lacks’ (Chudley and Greeno, 2006). However when combined with the compressive strength of concrete, the overall strength of the composite material is increased. A particular concern for the RC is the corrosion of embedded steel, this can have a detrimental effect to the material and influence its structural integrity and durability therefore it is vital that the steel is protected to prevent the occurrence of corrosion. There are various procedures considered when minimising the risk of corrosion and their effectiveness in doing so has been reviewed.
2. Corrosion
The rate of corrosion in reinforcing steel or rebar is increased significantly when structures are exposed to a ‘highly alkaline environment’ (Tretheway and Chamberlain, 1995) which forms a ‘passive layer’, a ‘thin layer of oxide’ that contributes to a slow rate of corrosion on the steel surface. (Broomfield, 2003)
This subsequently leads to the formation of rust due to the ‘carbonation of the concrete cover and penetration of chlorides’ (Martinez and Andrade, 2009). If ‘water, oxygen and carbon dioxide’ are able to attack the concrete this results in a loss of bond between the concrete and the steel (Tretheway and Chamberlain, 1995). Causing ‘high tensile forces’ from the expanded steel bar and