Q.: What kind of concrete mix would be most resistant to acid rain, which has become a problem in the New England area?

A.: Portland cement concretes are likely to suffer to some extent, no matter what mix you use. Mixes made from calcium aluminate cement are more resistant. The best solution is to apply a clear acid-resistant coating such as a methyl methacrylate--but one that the supplier can give evidence will do the job. It should be a breathing coating (one that is permeable to water vapor) so that moisture cannot become entrapped for long beneath it.