In some countries like the United States, asphaltic seal-coat is used in cement mortar lining of ductile iron pipes. Why?

The original intention of adding a thin asphaltic seal-coat on freshly placed cement-mortar lining is to reduce water loss during hydration so as to achieve better curing of the linings. In fact, it also helps hinder the leaching of cement by corrosive water. Otherwise, leachates from cement linings may cause a rise in pH in water.

However, asphaltic seal-coat is considered undesirable from environmental point of view. The seal-coat material is solvent-based which contains volatile organic compounds, which is an air pollutant.

This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.