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[Image above] A sample panel of unreinforced concrete flooring inspired by Gothic cathedrals on display at the Venice Biennale. Credit: Block Research Group

It’s not news that concrete—one of the most widely used construction materials across the globe—is not very friendly to the planet we call home. Estimates suggest that production of standard Portland cement alone accounts for nearly 5% of the world’s total carbon emissions. Plus, incorporation of so much concrete in our landscapes doesn’t come without its own environmental toll.

So, despite the ubiquity and long history of concrete in human civilizations, many research groups have been searching for better solutions, manufacturing practices, and alternatives to reduce the negative impact of concrete on planet earth.

While some solutions lower processing temperatures to reduce the energy requirements of cement and concrete production, another solution is simply to use less of the material in each application.

But that’s difficult when it comes to flooring—typical concrete floors require a thickness of ~25 cm and steel reinforcements to sufficiently support the loads of a building. So far, there has been little in the way of solutions that can offer comparable structural support with less materials.

Researchers at ETH Zürich, however, have developed a new modular and thin concrete flooring system that weighs 70% less than conventional concrete floors and could offer a greener building solution.

Inspired by ancient building principles, the thin concrete flooring system uses an arched design to offer a higher ratio of structural support to the amount of material used—allowing the concrete flooring to shrink in thickness to just 2 cm.

Individual slabs are joined together without mortar. Credit: Block Research Group

Akin to vaulted ceilings, the arched design distributes stresses within each flooring panel. A computationally optimized design of internal ribbing within the panels distributes compressive forces and provides the top of the panels with a flat surface to walk upon.

Together, the arched design and internal ribbing offer sufficient structural integrity to be able to eliminate internal steel reinforcements within the material and shrink the thickness of standard concrete flooring, together reducing weight by 70%—all without sacrificing strength.

“Stress tests have shown that it can withstand an asymmetric load of 4.2 tonnes, which is more than two and a half times what the applicable building codes in Switzerland stipulate,” according to an ETH press release.

Load tests show that the new type of floor fulfills Swiss construction standards. Credit: Block Research Group

The thin concrete slabs within a panel interlock together like puzzle pieces, requiring no mortar and offering a modular flooring solution. While this configuration is convenient and versatile, however, it questions the safety of the flooring system in the event of disasters, such as earthquakes, bombings, and other events.

As with many new research developments, cost is a current barrier for this innovative concrete floor, because the panels are cast in double-sided molds. But the team is eyeing additive manufacturing—the researchers have already adapted their panels to be 3-D printed with sand and a binder instead of cement. Although slabs 3-D printed this way can’t support as much weight—only 1.4 tonnes—they are still strong enough to meet Swiss building standards.

The scientists will next put the concrete slab flooring to the test in a real-world installation in an experimental building being constructed on the roof of a research building near Zürich, Switzerland.

The paper, published in Engineering Structures, is “Design, fabrication and testing of a prototype, thin-vaulted, unreinforced concrete floor” (DOI: 10.1016/j.engstruct.2017.01.075).