Hundreds of construction workers struck, protested and blocked roads around the Staythorpe power station site in Nottinghamshire on Tuesday.
The protest came after a health and safety breach.
Unite union officials called for Alstom, the main contractor on the site, to take immediate action to tackle the alleged breach. Workers asked for an immediate inspection after saying scaffolding had been interfered with.
Last week an official strike was cancelled after Alstom backed down over the method of selecting workers for redundancy.
The company agreed to abide by the national agreement where PAYE workers are laid off after subcontracted workers.
Last month an audit revealed that Italian construction workers building the gas-fired power station were paid £1,100 a month less than their British colleagues.