Two studies at the U.S. Department of Energy’s (DOE) Oak Ridge National Laboratory (ORNL) have relevance for the building and construction industry.

In one, ORNL researchers, in collaboration with machine tool manufacturer Cincinnati Inc., examined the potential use of multi materials and recycled composite in large-scale applications.ORNL used the Big Area Additive Manufacturing machine to 3D print a mold made of recycled thermoplastic composite and syntactic foam. Source: ORNL

The team adapted the Big Area Additive Manufacturing machine by adding a dual feed system to enable printing with multiple materials in a single build using one extruder. This was demonstrated by 3D-printing a mold that replicated a single facet of a precast concrete tool.

The large 3D printer produced a 400-lb, 10-ft-long mold made of recycled carbon fiber reinforced thermoplastic and syntactic foam within seven hours.

“New mechanical responses can be achieved with multi material printing such as soft and rigid segments within a part and impact resistant structures,” said ORNL’s Vidya Kishore.

Large-scale printing with multi materials and recycled composites could lower tooling costs and create opportunities to print structures with lightweight cores and tailored properties.

The mirage effect

In the second study, ORNL researchers developed an effective method for detecting air leaks from the roof and walls of a home or other building.

ORNL’s non-disruptive air leak detector captures air escaping from exterior walls and uses refractive imaging to calculate the leakage flow rate. Source: ORNL

Common detection options currently use a blower door and smoke or infrared thermography, methods which are costly and invasive. The ORNL method uses an imaging technique and is conducted from outside, so the occupants are not impacted by the process. The technique visualizes the flow of air leaks and calculates the volumetric flow of air based on the refraction effects imaged by cameras.

“Similar to a mirage over a black top road in the middle of summer, which looks fuzzy because air above the road is hotter than surrounding air, a building’s wall becomes blurry when indoor air meets outdoor air,” ORNL’s Philip Boudreaux said. “Refraction imaging allows us to see this.”

Correcting excess air leakage can decrease energy consumption in buildings and reduce potential for mold growth. The ORNL method does this faster, less expensively and with less disruption than other methods.