Q. I read that Horav Shlomo Miller shlit’a permitted to spread salt or sand on paved, cemented or concrete surfaces covered with snow or ice in Shabbos, (see question 2073) if there is a need. Later on I heard that he retracted on the spreading of sand. Is that correct?
A. The Rov added that if the paved, concrete or tile covered surfaces, have gaps, cracks or joints that would benefit from being filled in with sand, one should not spread it over them. Since even if he does not have an intention to fix them now (eino miskaven), it is likely that the sand will remain and become an accepted fixture of the floor. He will be then be transgressing on the prohibition of boneh or building.
Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit’a