Q. Can you spread rock salt on Shabbath on an (icy) entrance and steps?

A. Poiskim permit spreading salt during Shabbos (in any form or presentation), on an icy path, steps or a sidewalk to save people from harm. (Machaze Eliohu 67, Sh’miras Shabbos K. 23:21). This is seen only as an indirect action or gromo of nolad (39 Melochos 2:p. 368). There is no boneh or building either, since the salt dissolves and disappears.
In a place where there is no eiruv, Horav Shlomo Miller’s Shlit”a opinion is that, if it is only a rabbinical domain or karmelis (which is most common), and the salt was place before Shabbos on that same domain, you could carry the salt less than four amos (two meters) at the time.

Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit”a