GORINCHEM – A section of the bridge over the Upper Merwede near Gorinchem was treated several years ago with a new blasting technique, which is much less damaging to the environment. Van der Ende Straal- en Schilderwerken deployed its new, mobile grit recycling installation there at the time, creating much less waste than using the regular blasting method.
It was the first time this technique had been applied to a Dutch bridge. Rijkswaterstaat had the Merwede Bridge “conserved” so that it could withstand the next fifteen to twenty years. The construction was cleaned and given a new coat of paint so that dirt and weather would not get a hold on the steel frame.
In the regular blasting method, the paint layer is removed with slag grit. This finely ground waste product (slag) from the steel industry is blown against the bridge in a closed room under high pressure. The grit is then sucked up and transported in a closed truck to a special processing plant.
Van der Ende’s recycling plant uses a different type of grit for blasting. “The so-called steel grit – a stronger, more solid and angular piece of steel – lasts longer, unlike the slag grit,” explains commercial director Peter van der Ende.
He continues: “It can be reused as many as two to three hundred times, depending on the object being blasted. This is the first time we have used the installation, which originated in the United States, on a bridge. Companies in America were forced into developing the installation, which also reprocesses the used grit, by very high waste disposal costs.’
The installation costs more than one million guilders, but the investment certainly pays for itself, according to Van der Ende. “With this new technique, we are left with only about 2,500 kilos of waste after blasting the bridge, compared to about 50,000 kilos of waste in the old situation. At the facility, the waste is also separated into coarse waste such as glass and remnants of work gloves, dust and paint residue. Everything is collected in sealed containers. The grit is filtered out using a magnet and is ready for use again,” said Van der Ende.