Project Reference: Shotcrete Slump Control
Location: Brisbane, Australia
Applicator/Contractor: Jemna/Transcity Joint Venture
Concrete Producer: Holcim
Market sector: Civil Tunneling
Products used:
- MasterRoc HCA 20 a chemical admixture that controls the dynamics of cement hydration
- MasterSure 1008 a new generation super slump retaining aid for extended slump retention
- MasterRoc SA 167 a high-performance alkali-free set accelerator
Download the Project Reference PDF
The Background
Construction of Brisbane City Council’s Legacy Way Tunnel in Brisbane’s inner-city was undertaken by the Transcity Joint Venture (TJV) from 2011 to 2015. The 4.6 kilometre twin-bore tunnel provides an essential link for traffic between the Western Freeway in Brisbane’s west to the Inner City Bypass in Brisbane’s north. The tunnel forms part of Brisbane City Council’s TransApex transport plan designed to reduce traffic congestion and increase connectivity on Brisbane’s road network.
The Challenge
Whilst tunnel boring machines (TBMs) were used for the main road tunnel, a number of smaller cross passages were constructed in between the two road tunnels for evacuation and emergency services. These tunnels were made using robotic shotcrete technology from contractor, Jemna. The shotcrete required for the primary lining of these cross passages had to be delivered to suit TJVs continuous operation program. This involved maintaining minimal impact to the adjacent residents at night.
Hydration-control admixtures in shotcrete mixes are a common solution to provide contractors with confidence that the mix will not hydrate when the spray application is required. However, this does not always guarantee that the controlled mix will maintain its optimal slump. TJV required an innovative solution where shotcrete could be delivered to site and held at optimal operating slump of 180mm for a period of up to 24 hours.
Our Solution
Master Builders Solutions worked with the principal contractor TJV, shotcrete contractor Jemna, and concrete supplier Holcim to provide an innovative solution that allowed shotcrete to be delivered to site and kept at ultimate working slump of 180mm for up to 24 hours.
- MasterSure 1008 retained the slump over an extended period of time.
- MasterRoc HCA 20 provided hydration control, ensuring security that the shotcrete would not hydrate throughout the extended period.
- MasterRoc SA 167 shotcrete accelerator was added to the mix while spraying the tunnel lining. This ensured high shotcrete early strengths were achieved.
Project Facts at a Glance
- Transcity Joint Venture consisted of Acciona, Ghella and BMD.
- Brisbane’s Lord Mayor Graham Quirk opened Legacy Way in July 2015.
- Extended slump retention technology has been utilised in other tunnel projects, including the Tintenbar to Ewingsdale Pacific Highway upgrade in Northern New South Wales.
- A number of underground mine sites have also successfully utilised this technology.
Product Facts at a Glance
- The liquid admixture MasterRoc HCA 20 can be used for wet and dry shotcrete mixes, therefore stabilising setting and hardening
- MasterRoc HCA 20 also controls hydration of all cement minerals
- The alkali-free set accelerator MasterRoc SA 167 is used for rock support, slope stabilisation and wet ground conditions
- MasterRoc SA 167 has quick setting properties allowing rapid work progress and has continual early-age strength development
- MasterSure 1008 is a slump retaining aid with the ability to work over a range of water binder ratios
- It has high workability, low shrinkage and creep, as well as being very durable in hot climates
The Customer's Benefit
- Shotcrete was able to be delivered to site during daylight hours but held for application throughout the evening.
- Less traffic to site during the night minimised the impact of tunneling operations to the neighboring residential community.
- Concrete supplier, Holcim, was able to minimise costly nightshift operations.
- The ability to control a constant working shotcrete slump minimised the need for re-tempering of the shotcrete mix, ensuring design compressive strengths would be maintained.
- Minimal traffic from concrete agitators allowed improved access to tunneling operations.
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