How a new building technology could save two-thirds of the concrete

With more than four billion tonnes per year, cement is the most widely used material in the construction industry. But manufacturing and processing are responsible for six to eight percent of global greenhouse gas emissions, especially carbon dioxide. To reduce this climate impact, new variants of cement and new production processes are currently being tested in order to be able to reduce emissions by a quarter. But engineers at Technical University of Brunswick are pursuing a different strategy with intelligent 3D printing method: they want to make filigree and at the same time stable concrete structures in order to save 50-70% of the building material compared to to solid concrete elements. .

“In concrete construction in particular, it is common for the walls to be solidly concreted. However, we want to achieve a light and loose construction method that is more familiar with wood or steel, ”explains Dirk Lowke of the Braunschweig Institute for Building Materials, Solid Construction and Fire Protection. To do this, he and his colleagues developed a method to create finely structured three-dimensional structures from concrete – a mixture of cement and stone additives of different particle sizes. With this 3D injection printing process, liquid concrete is injected into a special carrier liquid, such as transparent gel. This carrier liquid holds the concrete in the desired positions until it has hardened. If the support – potentially recyclable – is removed, a filigree concrete structure in the form of a lattice remains.

Aerated concrete structures

“Concrete components are suitable, for example, for bridges or roof structures,” Lowke explains. These could be manufactured centrally in a factory and later assembled on site. It also opens up new design possibilities for architects and civil engineers to design filigree buildings with less material and high stability.

Swiss civil engineer Robert Maillart and Italian civil engineer Pier Luigi Nervi developed the first examples of such ventilated structures which were too expensive for large-scale use. Lowke, meanwhile, is convinced that pressure injection processes could significantly reduce costs.

Along with pure concrete structures, work is also being carried out to combine them with stabilizing structures made of steel or long strands of carbon fibers. Not only would concrete come out of the nozzle of a 3D printer, but also wire rope or fiber to further increase stability. However, this technology is not yet ready for use. However, engineers at Braunschweig predict that their patented process could be available for large-scale applications in a good ten years or so.

(baccalaureate)