Migrating Inhibitors for Preventing Carbonation Induced Corrosion of Reinforced Concrete

Abstract

Since its inception in the mid 19th century, Reinforced Concrete (RC) has become the most widely used construction material in the world. However, deterioration of RC structures, due to exposure of rebar to aggressive environment, has become a major concern all around the world. De-icing salts and carbonation are the two major factors responsible for the deterioration of RC structures. During the 20th century, extension in industrial emissions have raised the CO2 levels in air drastically, which has further led to increase in the carbonation rate of concrete and carbonation related distress of RC structures. Rebar corrosion ultimately affects the service life of the RC structures and rehabilitation of such structures has become a great challenge both technically as well as financially. The prevention of rebar corrosion can be handled using several techniques such as denser concrete, latex or polymer modified concrete overlays, waterproofing membrane with asphalt overlays and cathodic protection to the rebar etc. One amongst these methods involves the use of corrosion inhibitors, which provide a simple and cost effective solution for prevention of corrosion of RC structures. Corrosion inhibitors are chemicals that are able to reduce corrosion rate and are generally used in relatively small quantities. Based upon the mode of application, corrosion inhibitors are generally classified into two categories: (a) admixed corrosion inhibitors which are mixed during casting of concrete and (b) migrating corrosion inhibitors, which are applied on the surface of concrete during rehabilitation procedures and they subsequently diffuse into the hardened concrete to reach the rebar level thereby developing their inhibiting action at the rebar surface. Migrating inhibitors have an advantage over admixed corrosion inhibitors in terms of their negligible effect on cement hydration and properties of the resultant concrete.