A Scandinavian consortium has developed a technique for blending contaminated sediment with a mix of binders to produce a safe construction material.
Hazardous sediment is a particular problem for the shipping and port industry, where dredging routinely turns up sediment contaminated with the likes of carcinogenic PCBs, TBT, cadmium, lead and mercury. Port owners are caught between constraints on dumping sediment at sea, the cheap but polluting option, and the expense of removing it to be treated for landfill.
A recent €3.55m EUREKA project, called STABCON, therefore saw a Swedish-Norwegian consortium first compare the available disposal methods from a sustainability perspective. Stabilisation and solidification proved to be a sustainable and cost-effective alternative. Contaminated sediment is mixed on site with products that bind it to create a solid material that contains the hazardous substances.
“As well as being more environmentally friendly than dumping and cheaper than landfilling, this method offers a number of additional benefits,” explained Göran Holm, R&D director of the Swedish Geotechnical Institute, one of the project partners. “It reduces the demand for natural resources, such as blasted rock; and by treating the sediments in situ and using them in port areas, the need for transport is reduced, along with the associated health risks.”
Researchers observed the behaviour of the treated sediment for leakage, permeability, strength and durability. The binder they used was a mixture of cement and Merit 5000, a derivative from the steel-making process produced by project leader Merox, which is a subsidiary of Swedish steelmaker Svenskt Stål AB. The slag is able to bind heavy metals chemically at the same time as it cures.
Following the success of initial testing at the Swedish port of Oxelösund, itself a partner in the project, other ports are now testing the technology, and a more extensive R&D project has been launched for the whole Baltic Sea region.
The Recycled Port