Slabs for the programmable warm water pools will be poured as part of the $4.5 million redevelopment of the Ballarat Aquatic Centre.

Preparatory works for the pools has included excavation, water proofing, steel reinforcement and the installation of framework to the edges of the slab.

The second-stage redevelopment also includes two new group change-rooms, an extended and re-furbished cafe and renovated entry area.

Work on the centre, which is being done by local construction company H Troon Pty Ltd, began last month.

The project has been jointly funded by the Ballarat City Council and the State and Federal Governments.

The redevelopment is expected to be completed by the end of this year, three years after funding for the project was announced.

Ballarat City councillor Des Hudson said the work was a significant project for the city.

The two new pools would free up lanes in the centre's busy main pool, he said.

"The numbers going through the aquatic centre are nearing 600,000 annually and this investment will further the capacity of the centre making it a venue that's accessible for all," Cr Hudson said.