Adam Richard Paine, 32, yesterday pleaded guilty in the County Court in Ballarat to making an explosion without lawful excuse and possession of explosive materials.

The court heard Paine was a mature age student in applied science when he made the bomb at the University of Ballarat on May 17 last year.

Crown Prosecutor Justin Lewis said a couple of days later Paine strapped the bomb to a five litre container of petrol before detonating it on a vacant block.

Mr Lewis said the explosion shook nearby houses and metal debris was scattered in the area.

Mr Lewis said police had searched Paine's home and found items used to make the explosion.

Defence lawyer Richard A Lawson said Paine had made full admissions to police and was immediately taken into custody.

Paine was not granted bail until May this year and has spent the past three-and-a-half weeks in a drug and alcohol treatment residential facility in Keysborough.

The court heard Paine had a history of mental illness including recurring bouts of depression and had been admitted to a psychiatric ward at Ballarat Health Services Base Hospital on four occasions in the past 13 years.

Mr Lewis urged the court to impose a sentence that would allow Paine to continue with the residential drug and alcohol program.

Judge Les Ross described the explosion as a "stupid exercise" and said the potential for harm was significant.

"They are offences that this court must robustly discourage," he said.

But Judge Ross took into account Paine's psychiatric condition and plea of guilty and sentenced him to 18 months' jail with a non-parole period of 350 days. Paine has already served 350 days in custody and will therefore be

immediately eligible for parole.