The concrete used in some parts of Mater Dei Hospital is estimated to have cost half what Maltese taxpayers were charged for it, The Sunday Times of Malta has learnt.

Concrete is made up of a mixture of cement, sand, gravel and water. Tests on cores taken from the hospital indicates that less cement than required was used in the formula and in some cases limestone (franka) gravel was used instead of the stronger, and costlier, hard stone (qawwi) type.

I would expect to find limestone gravel in the floor of a house garage, certainly not in a supporting column of a hospital

It is the latest development in a probe which found weak concrete across Malta’s only general hospital, inaugurated in 2007. The government has requested an urgent meeting with the Swedish contractor after it was established that repair works will cost some €30 million.

The Health Ministry was not in a position to say how many cubic metres of concrete had been poured at Mater Dei Hospital, while the Arup Group, the UK engineering firm commissioned to study the strength of the hospital’s structure, would not be drawn to say whether the concrete produced would have cost less.

However, industry insiders said the type of concrete that forms the columns beneath the Accident and Emergency Department, for instance, which tested at a strength of 18megapascal (a metric pressure unit) would have cost half the 30mpa concrete specified in the contract. Similar-strength concrete was found across the hospital’s structure.

There is also the possibility that the concrete may have been weakened by too much water during the mix. However, the extent of weak concrete suggests there was something wrong with the formula.

An engineer familiar with the testing of the samples taken from the Tal-Qroqq Hospital said one would only expect to find limestone gravel in domestic applications which would not require great strength. “I would expect to find limestone gravel in the floor of a house garage, for instance, certainly not in a supporting column of a hospital,” he said.

The hospital would not be able to operate in the case of an earthquake

Arup director Andrew Harrison told a press conference last week he had never seen such weak concrete used in a public building, let alone a hospital.

Block D, the largest block where most of the wards are housed, scored below specification. Block A, which host the renal unit and the physiotherapy departments, and Block B, which houses the medical school and the management’s offices, also scored badly. The worst structure is the emergency department. The mortuary and block E, the outpatients department actually exceeded specifications.

The €600m hospital was meant to be earthquake proof but Mr Harrison said the hospital would not be able to operate in the case of an earthquake without remedial action.

That remedial action is expected to cost somewhere in the region of €35 million.

The government is pointing fingers at Swedish firm Skanska, which was responsible for the construction oversight of the project. Health Minister Konrad Mizzi has demanded a meeting with a view to find the “least acrimonious solution” possible.

The strength of the hospital’s structure started being investigated last September after contractors Attard Bros and Mekkanika, which won a tender to build two new wards on top of the A&E department, carried out stress tests on columns and found out they could not withstand the weight of more stories.