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In October 2001, the Sydney Harbor Bridge obtained funding to re-paint the two approach spans, approximately 1,000,000 ft2 of blasting and painting. Traditionally used GMA SpeedBlast Garnet on the bridge, however all the industry experts convinced the project team that Steel Grit was absolutely the best way to go. The project required the removal of lead paint, very good quality containment system and good access for equipment that is ideal for Steel Grit. After the additional purchase of an $800,000 Steel Grit Recycler the project commenced.
Initially it went well – however there was a few things we found that surprised us – we could only get 15-20 recycles from Steel Grit – much less than the 50-200 which we had been promised. Also we were spending 4x the amount of time cleaning up than what we had allowed for. This narrowed down that we needed 20 lbs per ft2 for Steel Grit, but only 4 lbs per ft2 with Garnet. After around 6 months, our cost were significantly over budget, blasting cost per ft2 was averaging out to $4.00 – $5.00/ft, plus we were experiencing significant downtime due to moisture leaking through the containment which was causing the steel grit to rust and clump. We decided to change back to GMA SpeedBlast Garnet.
Instead of taking 4 hours to clean up after only 8 hours of blasting the time was reduced to under 1 hour. We could also obtain a white metal blast much faster. After a few months, we calculated our total blasting costs had reduced back within budget to around $2.50/ft.
Since 2003 we have strictly used GMA SpeedBlast Garnet on the Sydney Harbor Bridge for all coating removal and surface blasting, with great success.