A protest outside a Greyhound recycling depot in Clondalkin is entering its second day.
Around 70 collection workers downed tools yesterday in a row with management over cuts to pay.
There will be pickets at two locations, and Siptu's Henry O'Shea said they are starting official action today, saying it was a "lockout" situation.
He also said the details of an agreement from management are different to the Labour Relation Commission's recommendations.
"What they had included in the body of their submission was actually worse than the last document that we came out of the LRC with, because it had further cuts in it to the wages … of the lads," he said.
Yesterday, a worker was injured by a reversing bin truck at the demonstration.