The Sydney Metro Central Walk, the latest construction phase of the Sydney Metro City & Southwest project, was opened to the public by the New South Wales government (Australia) in April 2023. The underground pedestrian tunnel used the Penetron System, a comprehensive crystalline waterproofing system, to protect the below-grade concrete tunnel structures from high hydrostatic pressure.
Sydney Metro City & Southwest is Australia’s biggest public transport project, set to transform Australia’s most populous city with an extended network of underground and regional train lines. Once complete, trains leaving Sydney’s Central Station every two minutes will move up to 40,000 travelers per hour. The first phase of the fully automated rapid transit system opened in 2019, with a twin track line running 22.4 miles (36 km), mostly underground, to serve 13 stations. Further construction work currently in progress will extend the Metro system under Sydney Harbor and the Central Business District (CBD) by 2024.
The Sydney Metro Central Walk is an 80 m (265 feet) long and 19 m (63 feet) wide underground pedestrian concourse connecting passengers to trains, light rail, and the new Sydney Metro underground platforms. Running perpendicular to the Central Station tracks and above the new metro platforms 27 m (90 feet) below the station, the concourse will help meet a more than doubling of customer traffic expected over the next two decades.
“The construction of Central Walk is an engineering feat!” enthuses Steve Hodkinson, Penetron Australia General Manager. “During construction, carried out beneath eight railway platforms, the trains remained operational through the building phase while 38,000 tons of rock were removed, the equivalent of six Olympic swimming pools.”
Protecting reinforced concrete structures from deterioration caused by the penetration of water, moisture, and chemicals is an essential aspect of tunnel design and construction. Failed tunnel waterproofing is not only a serious safety hazard, but it can also be extraordinarily expensive to repair. Working together with the Central Walk project’s design and construction teams, Penetron Australia provided a reliable concrete waterproofing solution for key structures of the Central Walk concourse.
PENETRON ADMIX, a crystalline waterproofing admixture, and PENETRON, a topically applied crystalline slurry, were specified to provide extensive waterproofing protection for the precast modules, shotcrete, and cast-in-place concrete elements of the underground concourse. PENECRETE MORTAR, a crystalline waterproofing repair grout, was also used to treat all internal tie bolt holes.
“When faced with high hydrostatic pressure common in tunnels, the use of the Penetron System is a more economical solution when compared to conventional alternatives, such as membrane systems or spray on sealers,” adds Steve Hodkinson. “It also provides permanent protection for the service life of the structure and is self-healing, sealing all future hairline cracks that may form.”
Concrete structures protected by Penetron: The Sydney Metro Central Walk spans the width of the city’s Central Station, crossing below the ground-level rail lines seen in this bird’s-eye view.
Durable concrete structures required: Built 27 m (90 feet) below the Central Station tracks and above the new metro platforms, the Central Walk will help meet a doubling of passenger traffic.
