Mr Rezagui was a formworker who helped prepare the ground for a concrete pour where Mr Catanzariti was struck in the head when the concrete boom broke. Two other workers were injured.

Mr Rezagui ran to the scene after hearing a loud explosion. He said he can never erase the sight of Mr Catanzariti in his last moments as mates scrabbled to cover his gaping head wound and comfort him.

''It was that shocking moment where everything in life changes,'' he said.

Mr Rezagui was called back to work the next day but found himself in such a state that he needed to take a week off and receive counselling.

''What can I say? It is not something I ever thought I would see, not on a Canberra building site.''

A hidden cost of Canberra's high accident and death rate in construction is the number of workers who suffer post-traumatic stress disorder as a result. Some turn to alcohol, drugs or even suicide to block out the experience of being injured, or witnessing a mate injured or killed.

Clinical psychologist Carmel O'Sullivan, who is referred patients by the Construction, Forestry, Mining and Energy Union, said in some cases it took years to recover from the shock of a workplace accident.

Ms O'Sullivan said she had a heavy caseload this year in line with the findings of the ACT government's inquiry into workplace safety that ACT construction sites were the most unsafe in the country.

The inquiry, which handed over 28 recommendations on Monday, found at least one accident occurs each day on Canberra sites.

CFMEU ACT secretary Dean Hall said the union devoted considerable time to checking on workers affected by mishaps, as well as providing counselling services. ''I've seen everything from blokes being physically sick, to crying, to shaking and in shock. Some blokes are so badly affected they never work again. Others look like nothing has happened.''

Mr Hall said the construction industry already battled higher than average rates of alcohol, drug abuse and suicide because of the stressful nature of the work. But accidents and injury exacerbated these problems and the costs were eventually borne by the community when marriages dissolved, children suffered distress and incomes were lost.

''For every dollar spent on safety, it potentially saves the community thousands of dollars to put the pieces back together again after an accident,'' he said.

Ms O'Sullivan said the industry needed to better understand the impact of post-traumatic stress.

''Big burly builders don't ever like to think of themselves as weak,'' she said. ''But they needed to understand that accidents can be a pretty big deal, physiologically and psychologically, and it is not something you can just brush off.''

Shock, nausea, crying, sleeplessness, irritability, flashbacks and panic disorders were all quite normal human responses.

Within six to 12 months following a trauma about half of those affected would resume normal life. But for others, it could take years.

Ms O'Sullivan, who began her counselling career with Vietnam veterans, said she was still in contact with some of the workers who survived the collapse of an aircraft hangar at RAAF Fairbairn in 2003.

''One young apprentice at the time has never recovered. He rings me in tears saying, 'I think I should end it all'. No lives were lost that day but a lot of men lost the potential of where they might have been today.''

Anyone in distress can contact Lifeline on 131 114