fatting up
n.— «Whitby-based highways engineer David Creek told the Whitby Gazette the summer heat had caused a process known as “fatting up” where the bitumen holding chippings in place gets softened and the chippings sink down into it.» —“Road chief warns of ‘fatting up’” Whitby Gazette (United Kingdom) Nov. 8, 2006. (source: Double-Tongued Dictionary)