Why is surface protection treatment necessary over the repaired surface

Why is surface protection treatment necessary over the repaired surface? What should be the quality requirements of such treatment?

The protection to the repaired concrete surface is best given by penetrating sealing compounds. This helps in sealing any voids and cracks that would otherwise allow moisture and other chemicals to penetrate concrete. The sealer should be applied on the entire surface including the areas, which have not been repaired. This gives protection to entire surface and not only on the patches of repaired surface. There are various types of coatings like polyurethane, alkyds, acrylic emulsions and epoxies used for this purpose.

The quality requirements of coating should be as follows:

	It can be pigmented to give suitable colour and is easy to apply.
	It should be compatible with alkalinity of concrete.
	It should resist aggressive attacks and fungal growth.
	It should adhere well to both old as well as repaired concrete surfaces
	It should be able to take care of irregularities on the surface, presence of slight dampness or inadequate cleaning.
	It should be able to last long and colour should not fade due to ultra violet radiation.