Testing two or three samples from the public hospital’s concrete structure to determine its overall strength might not be enough and further analysis would be required to have a more reliable result, according to an expert.

Alex Torpiano, dean of the Faculty of Built Environment at the University of Malta, was asked to comment in the wake of a report carried by The Sunday Times of Malta on possible structural weaknesses at Mater Dei’s emergency department.

Two core stress tests carried out on the concrete structure indicated that its quality was significantly below standard and extremely weak in certain areas.

In this kind of test, a sample is sent to a laboratory where it is subjected to huge loads until breaking point to establish its ultimate strength.

A third test was made on a separate concrete sample and the results are expected in the coming days.

Without entering into the merits of this particular case, Prof. Torpiano said more samples would need to be taken to have a better picture of the situation and a more reliable statistical result.

In addition, other factors, such as the steel component of reinforced concrete, had also be taken into consideration as this carries the lion’s share of the load.

Even the source of the sample itself had a bearing on the result because it made a difference whether it was taken from a pillar, a beam or the foundations, he added.

“This is not like a pacemaker where each and every device has to be tested because, in the construction industry, tests are carried out according to certain frequency dictated by quality control standards. It would not make sense to test every piece of concrete laid,” Prof. Torpiano said.

For this reason, he said, it would not be unreasonable for a limited batch to go undetected in between tests.

“Hopefully, this can be traced back and those parts of the structure built from it would be identified. I would expect such practice in a large-scale projects,” Prof. Torpiano said.

On his part, the vice president of the Chamber of Architects, Christopher Mintoff, noted that even though two tests might not have been be enough, the results should not be taken lightly.

“Normally, a concrete structure is at its best some 15 years after construction so the results at Mater Dei are quite unusual, to put it mildly.”

Though no cracks were visible to the naked eye, he said further inspection was needed to uncover any parts hidden behind the infrastructure.

“It only takes a single failure at one particular spot for a structure to collapse.”

Referring to the health minister’s remarks that part of the concrete could be crushed by hand, he said this seemed like a case of poor workmanship.

While there might not be imminent risk of collapse, the situation called for urgent action because this was a highly sensitive place, he pointed out.

Architect Ivan Cachia highlighted the fact that even when concrete was being cast, fresh samples were taken for laboratory testing as part of the quality control process.

Asked about the possibility of having huge quality variations across two different samples, he said that it all depended on the source.

“Such a thing would be very unusual, though possible if both samples were taken from the same structural element.

“Normally, such an occurrence is associated with cases where samples are taken from two different elements as they would have been cast from different concrete batches,” he said.

As for possible solutions in case a concrete structure needed to be reinforced, the three architects said this depended mainly on the extent of the structural weaknesses and the nature of the building.

If no additional load would be placed on top of the structure, minimal intervention would probably be enough.

However, if additional storeys were being planned, extensive works would be needed to make the place safe, they said.