The 29ft-high cage, which would have been used to construct a large structural wall, toppled over at the Goval Bridge section of the road, near the suburb of Dyce.
Workers at the site claimed it was lucky no-one was killed as construction continues on the £745 million road project.
Transport Scotland revealed yesterday that an investigation has been launched into the incident.
A spokesman for the roads agency said: “No-one was injured as a result of this incident. An investigation is currently under way and any lessons will be applied to future work. Transport Scotland takes health and safety very seriously and is working with the contractor to ensure the highest health and safety standards are maintained across the site.”
The long-awaited Granite City bypass will connect one of Scotland busiest roads, the A90 at Stonehaven on the south side of Aberdeen, with the Blackdog area to the north.
The Scottish Government has claimed the link road – which means motorists can avoid the city centre going north and south – will shorten journey times and cut traffic going through Aberdeen.
The proposal for a bypass first emerged in 1948 when council officials carried out surveys of the area.
But the then-£1m cost was deemed too high for the area, which was still recovering economically from the Second World War.
Proposals for the link road were given serious consideration again in the 1980s, but it was not until 1999 that then-first minister Jack McConnell finally approved the plans.
A failed legal challenge over the proposed roads network then caused a delay in the start of the scheme, with preparatory work finally starting in 2014.
However, some workers have now raised safety concerns about the project.
North East MSP Ross Thomson said: “It is imperative that an immediate and robust investigation is carried out to identify how this happened, to support putting in place new procedures to give local people and those working on site the absolute reassurance that such a serious incident won’t happen again.”