Thirty-two concrete slabs were replaced on the Rarotonga International Airport runway at a cost of $6.5 million.

Airport Authority’s outgoing chief executive officer Joseph Ngamata said around 20 additional slabs needed to be replaced this year or next and 13 could be replaced before the end of the financial year in June.

“The slabs over the years have cracked because of the number of heavy planes that we were landing on it, we’ve treated them in the past by injecting and pumping grout, but it gets to a point that you have to replace it,” Ngamata said.

“We had the opportunity with Covid-19 stopping the flights, or there only being one flight once a week to do some work and start replacing the slabs, that’s why we actually started replacing them.”

The replaced slabs will last 30 to 40 years, while slabs fixed with grout last up to 10 years before they need to be replaced.

Ngamata said the Airport Authority found around 73 slabs with cracks that needed to be fixed or replaced.

“In the future, we will continue to replace slabs, as they age the ones that have not cracked yet will crack.”

The slabs are made with rapid set concrete and can be landed on by a plane after four hours of being set.

Ngamata said this meant replacing slabs between flights with the border open “shouldn’t be a problem” assuming the number of flights stay the same.

He said once the slabs are repaired, two or three slabs a year will crack but they would not be in critical condition and need to be replaced.

Each concrete slab is roughly 6x6 metres and 350mm in depth while another 200mm is allowed for packing as diggers clear each square.

Each square is cleared of the original sand base, laid nearly 50 years ago, compacted and refilled with an aggregate base.

It takes about 10 hours to prepare and pour each slab.

The project was estimated to be completed in March this year.

The tender for the project was awarded to a joint venture between local companies, Concrete Systems and Triad Pacific Petroleum. Equipment and supplies for the project were ordered from overseas, including two volumetric trucks equipped with concrete mixers used for rapid set concrete.

The runway is made up of around 2500 slabs.