Back on Stream after 58 Days
New Technology Employed
The Alz Canal is an important lifeline in the region – not just as a source of energy and cooling water. For its shutdown, 3.8 metric tons of fish were fished out and relocated to the Alz river.
Whereas Stauber and his team had to keep their eyes on the big picture, WACKER applications engineer Klaus Bonin and his colleagues focused on a relatively small area to be renovated. “Last year’s comprehensive restoration of the Alz Canal gave us an opportunity to use a brand-new technology that we’d developed, and test it under real-life conditions,” Bonin recalls. As the chemical engineer explains, “We renovated an area of roughly two square meters with what is known as a self-filling concrete compound, or SFCC.” SFCCs can only be formulated with the aid of dispersible polymer powders – the field in which Bonin and his laboratory assistants, Peter Rauchberger and Christine Köster, specialize.
“We had estimated 70 days for the renovations, but we brought the canal back on stream on October 26, 2016 – after just 58 days.”
Infrastructure repair engineer at WACKER
“The idea of developing a self-filling concrete compound came from Indonesia. Researchers there were looking for a simple, quick-drying technology for making relatively small road repairs,” the engineer recalls. “The time frame for blocking off roads and restoring the road surface is usually small.” Customized dry-mix mortars modified with dispersible polymer powders meet those constraints. Unlike traditional concrete, which is transported as a prepared, ready-to-pump mixture of cement, additives and aggregate stone, this product is handled somewhat differently: the desired filler aggregate (pebbles or crushed rock) is separate from the cementitious binder – in this case the dry-mix mortar. At the construction site, the stone is first spread out on the prepared section of roadway, after which the dry-mix mortar is then combined with water as directed and poured over the layer of gravel. “The compound then fills in all the gaps between the rocks and binds them into a solid layer of concrete. Depending on the formulation, the system sets very quickly – sometimes in even less than an hour if requested. We can adjust that to the customers’ precise specifications,” Köster explains. “Since the pieces of crushed stone are packed close together, you end up with a strong bond after just a short period of time.”
The key issue is for the SFCC to have the right flow characteristics – the right rheology, in other words. Using VINNAPAS® 7016 F dispersible polymer powder from WACKER meets that requirement: “It gives us a really unique rheological profile – one you can’t get with conventional flow improvers,” Bonin explains. “After all, you don’t want the liquid mixture to flow too slowly or too quickly through the pebble structure. If the formulation is not intrinsically stable, if it solidifies too early or forms air bubbles, then it won’t work the way it’s actually supposed to – and that will jeopardize the stability of the entire concrete structure.”
Recycling with Concrete
One advantage of the new WACKER development is that stones that have broken loose or other solid recyclable materials can be crushed and then mixed with the SFCC, allowing old construction materials to be immediately reincorporated into a project. “Since our modified dry-mix mortar can be mixed with water on site, using SFCC allows us to recycle materials right on the construction site. That reduces the amount of new construction materials that we have to transport,” says Köster.