Precast concrete mast showcases dynamic capabilities

A precast concrete mast for the Mount Street Footbridge in Perth has become a towering testament to the dynamic capabilities of precast engineering solutions. Reinforced Earth manufactured and supplied the precast mast as part of a Main Roads WA upgrade project to the footbridge.

The mast and footbridge stand proudly in the heart of Perth’s CBD, connecting St Georges Terrace with Kings Park. The 73.5-meter long footbridge spans the busy Mitchell Freeway below, offering enhanced safety and accessibility for pedestrians and cyclists.

The centrepiece of the bridge upgrade is the 14.3-metre tall precast concrete mast weighing 31.7 tonnes. Installed alongside new LED lighting and upgraded balustrades, the mast and other works align visually with the lighting at nearby Optus Stadium and the iconic Matagarup Bridge. The original mast, installed in 1972, had developed structural cracks after nearly 50 years in-situ, necessitating the replacement by Reinforced Earth as part of the upgrade project.

The project required three concrete elements featuring intricate steel fixings and thermal control probes. A Class 2 finish was achieved using custom steel moulds. To manage a maximum specified concrete curing temperature differential of 20°C, a low heat mix and thermal control measures were implemented, ensuring high-quality results (resulting differential was only 7°C).

In opting for a precast concrete solution from Reinforced Earth, the project saw significantly reduced installation times; highlighting the efficiency and excellence that our custom precast solutions have in delivering high-quality infrastructure solutions.

Contact your local Reinforced Earth Australia office to utilise precast concrete in your next project.

Discover more about Reinforced Earth’s precast solutions (RECO Precast) here. For more detail on this RECO Precast project, read the detailed case study below.

Case study: Precast concrete mast

Towering bridge mast a testament to capabilities of precast concrete

A towering precast mast manufactured for the Mount Street Footbridge in Perth by Reinforced Earth is an unmissable icon. Located in the heart of Perth’s CBD, Mount Street Footbridge connects St Georges Terrace with Kings Park, the 73.5-meter long footbridge runs over the Mitchell Freeway below.

Part of a bridge upgrade, which delivered improved safety and accessibility for pedestrians and cyclists, the project saw the installation of a precast concrete mast weighing 31.7 tonnes and measuring 14.3 metres tall.

Installed in 1972, the original mast held an integral part in the structural capability of the footbridge. After nearly 50 years of the previous mast supporting the footbridge, it had developed cracks, leading to the necessary replacement, and Reinforced Earth was awarded the contract to replace the structure as part of the Main Roads project.

Class 2 curved precast elements specified with intricate steel fixings and thermal probes

The project scope included the manufacture of three concrete elements with intricate steel fixings and thermal control probes. When manufacturing the precast mast for the footbridge, a Class 2 finish was required for the curved radiused sections of the mast and capping sections. Steel moulds were custom manufactured and used to cast the elements and achieve the desired result.

Maximum curing temperatures

A maximum concrete curing temperature differential of 20°C was also required in scope. Reinforced Earth worked closely with our concrete suppliers and a durability consultant to conduct a thermal control analysis on the elements, based on the selection of moulds, the concrete mix design and the specification requirements.

A low heat concrete mix was used to eliminate the risk of exceeding the maximum temperature. Additionally, 20kgs of ice per m3 of concrete was added and poured early in the day to ensure the concrete differential temperature was as low as possible. Due to the poor insulation properties of the steel moulding, a timber plywood housing was built around the mould to keep it insulated throughout the curing phase. Four temperature probes were installed in each mast section to record the maximum temperature and the temperature differential whilst curing. The four probes recorded the ambient temperature, the concrete temperature 50mm from the edge of the mould face, the concrete temperature at the centre of the products and the concrete temperature 50mm from the edge of the product at the trowel face. These probes were monitored regularly so that the timber plywood housing could be removed for periods of time to control the concrete temperatures. As a result, the maximum concrete temperature recorded was 54°C and the maximum temperature differential recorded was 7°C.

Precast delivers in one third of in-situ time

Precast concrete was chosen for this project as it took only a third of the amount of time of in-situ concrete, had it been used. Ease of control and installation on-site were two additional benefits from choosing precast. As demonstrated by this project, the Reinforced Earth team prides itself on its problem-solving skills and determination to work through challenges efficiently and professionally, to supply high-quality precast to clients.

This project was completed in 2019.