The first project in Japan to introduce liquid accelerator solution for tunnelling
Contractor
Shimizu
Processes
Sprayed ConcreteLocation
Japan
The Project
A two-lane road tunnel using the drill and blast method of construction. The tunnel length is 2,583 metres. The project started in 2017 and was completed in 2020.
The Challenge
In Japan, powder accelerator is traditionally used for wet sprayed concrete. Shimizu is the first company to employ liquid accelerator solution for a tunnelling project in Japan.
With the powder accelerator method, rebound rates are around 20 to 30%, dust level is high and sprayed concrete output cannot exceed more than 12-14 m3/hr.
The challenge was to reach the performance specifications of powder accelerator with the liquid accelerator instead. Normet and Sandvik, our marketing partner in Japan, proposed a solution by Normet, and were consequently chosen as the solution provider.
Quick Facts
- A safer work environment for the operators with dust emissions reduced by 55%
- Up to 49% reduction in rebound with Normet's liquid accelerator compared to traditional powder accelerator
- 25% reduction in cycle times thanks to a higher sprayed concrete output
- Tunneling works completed ahead of schedule
The Solution
Spraymec 8100 VC as the spraying equipment
TamShot 110AF, a liquid alkali-free accelerator at 6.5% dosage (%bcw)
TamCem 60 as plasticiser for concrete
TamCem 77TG as VMA for concrete
TamCem HCA+ as hydration control for concrete
Normet’s team developed the mix design and conducted successful test sprays on site that aligned with the specification requirements.
Project Outcome
Spraymec 8100 VC operators were able to spray up to 24m3/h with an average of 8.2% rebound and Shimizu completed the tunnelling works ahead of schedule.
The information table from Shimizu's report shows the rebound levels of different spray concrete outputs. Data was collected by Shimizu engineers on site. In a concluding report and published paper, Shimizu stated that their first project with a liquid accelerator was successful in reducing cycle time, rebound and dust.
