Concrete is most widely used construction material in the world but is subject to decay mechanisms. Concrete is subject to chemical and physical attack to both its surface and bulk, and the chemical nature can change accordingly and it may also be accompanied by rusting of the reinforcement bars.
For any effective method of repair and rehabilitation, the following points need thorough considerations, besides the consideration of structural parameters:
(i) Ascertaining the extent of corrosion and carbonation.
(i) Near total removal of corroded portion of steel.
(ii) Application of corrosion resistant barrier film on the reinforcement steel.
(v) Application of useful bond coat which assures good bonding.
(v) Rendering a strong, passive carbonation resistant polymer modified concrete covers of proper mix, wherever necessary.
(vi) Applying protective seal coat on the entire surface to avoid an aggressive attack of chemicals.
All the above aspect are so vital in the chain of various steps of any job that neglect or overlooking any one of them can spoil the repair job. Though, the cement concrete and mortars are most natural repair materials for carrying out the repairs to RCC, yet, they are not favored as a repair material due to its inherent undesirable properties like drying shrinkage, slow setting, low workability, prolonged curing requirement, permeability, etc.
Classical methods of repair involving repair by plain cement mortar, cement concrete and plastering etc. often prove to be unsatisfactory because these measures do not adequately take care of the above points. It is found that in traditional repairs, the problem recurs very fast and detailed investigation in many cases have revealed that these repairs failed basically due to two major factors, that is, corrosion of steel not being totally removed and arrested effectively, and boor inadequate.
Nowadays, polymer modified concrete or mortars and other polymer based materials are being very widely used in repair and rehabilitation of concrete structure due to non-suitability of traditional repair materials. These are the composite materials made by partially replacing and strengthening the cement hydrate binders of conventional mortar and concrete with polymerize modifiers or admixtures such as polymer latexes or dispersions Redispersable polymer powders, water soluble polymers, liquid resin and monomers. The polymer modified mortar and concrete have a monolithic co-matrix in which the organic polymer matrix and the cement gel matrix are homogenized.
In addition to Polymer modified Concrete/Mortar, there are many other materials (e.q epoxy based, Polyurethane based, Rubber based, various admixtures, Rust remover/Converter Chemicals) which when used at right locations improve the quality of repairs many times compared to conventional materials. These materials and their usage have been discussed in detail in other topics.
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