Q. Could you spread salt mixed with sand, sand by itself, or sawdust (on an icy entrance or steps, during Shabbath)?

A. When spreading sand you have to be concerned with the boneh or building prohibition. If the surface is paved, cemented or tiled, Poiskim mostly permit, in order to avoid injury, spreading the sand or salt-sand mix, as it will not stay and is expected to be washed away on warm weather, It is better to use sawdust for that same reason (see Mishna Berura 313: 55, Shmiras Shabbos K. 25: 9).

In regards to the muktzeh prohibition, if the sand or sawdust was prepared or set apart before Shabbos for a permitted use, it is not muktze. However, even if it was not, Poiskim would remove the muktzeh prohibition when protecting the public from harm (Sh’miras Shabbos K’ ibid., 39 Melochos 2: p. 369).

See previous question, on dealing with the carrying prohibition where there is no eruv.
If available, one should ask a Gentile to do the above.

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