We recently had a story that made a reference to spalled concrete. I'd never heard of this, so I asked around the desk, and while some people were familiar with the term -- in this sense it meant crumbling -- it certainly seemed too obscure for the newspaper. So I changed it to crumbling. Spall is an older word, according to the OED, with the first sense appearing around 1440 as a noun and meaning "a chip or splinter, especially of stone or ore." Of its etymology, the OED says, " Of doubtful origin: perhaps related to German spellen, meaning to split, but compare to the noun spale." A spale is "a splinter or chip, a thin piece or strip, of wood," and its etymology is "There is resemblance in form to Old Norse spal-, spǫlr, meaning a bar, rod, short piece, the Middle High German (and German dialect) spale, meaning rung of a ladder, and the German dialect spale, spal, meaning wooden spit, wedge; but real connection with these is doubtful."
Spall's noun sense eventually got verbed, with the OED showing a usage in 1758 defined as: "Mining. To break (ore) into smaller pieces," and later, a sense first cited in 1858: "To split or chip; also, to detach as small fragments or particles." The adjective form, meaning "Dressed or broken with the hammer. More widely, broken off or chipped by spalling," is first cited in 1793.
None of these OED entries mention crumbling as a sense, though the American Heritage Dictionary does in its definition of spall as an intransitive verb: "To chip or crumble."