Simple past tense and past participle of jackhammer.(verb)
Wiktionary.org : Text is available under the Creative Commons Attribution-ShareAlike License
Use "jackhammered" in a sentence
"The Yankees, you'll recall jackhammered the concrete and dug up that jersey after they found it was buried there by a Red Sox fan on the construction crew."
"Ms. Ten Eyck jackhammered the stone shelf and transformed the problematic area into a gravel courtyard."
"A few years later, the old man took it down and jackhammered out the concrete."