[Image above] Printing layers of cement paste in a 3-D printer. Credit: Austin Thomas/NIST

Is there a material that cannot be 3-D printed?

Scientists have 3-D printed glass, human tissues, ceramic foams, and extraterrestrial soil. We’ve also reported on 3-D printed magnets and submarine hulls made of carbon fiber.

3-D printing, or additive manufacturing, is the process of extruding layers of a material through a “printer” type of machine to create a three-dimensional object. And the materials used can range anywhere from metal, glass, plastics—even chocolate!

What about concrete?

A while ago we reported on a 3-D printed bridge made of concrete and thermoplastic polypropylene. And this project illustrates how big things can be accomplished with concrete and a 3-D printer.

But before we venture into the construction world and print real buildings in which people can live or work, scientists need to perfect the formula and process of 3-D printed concrete.

The National Institute of Standards and Technology’s Summer Undergraduate Research Fellowship (SURF) program offers students opportunities to pursue STEM careers by engaging them in research projects. Mechanical engineering student Austin Thomas recently participated in one of NIST’s latest projects, additive manufacturing of cement. The goal of the project was to generate new ideas for improving the 3-D printing process using concrete as a material.

Led by NIST advisor Scott Jones, Thomas and a student team used trial and error approaches to measure the concrete’s viscosity, yield stress, and any printing defects. These variables are important because if 3-D printing is the future of construction, any defects could affect a building’s stability.

The team also printed carbon-fiber mesh that they layered into the cement paste to reinforce the concrete. Thomas says the most important habit he picked up during his fellowship was documenting and labeling specimens during the ever-changing “recipe.”

Reinforcing the cement paste with carbon fiber mesh. Credit: Austin Thomas/NIST

And the most significant purpose of these types of SURF projects is exposing students to research they may not otherwise have access to, Thomas believes.

“What is especially valuable about the research I did is that it allowed me to apply my existing knowledge of 3-D printing and manufacturing technology while gaining knowledge in materials characterization and cementitious materials in general—topics that would not be covered in any of my classes,” he says a NIST article.

Watch the video to see NIST’s 3-D printer in action.