Is 3-D Printed Concrete Really Concrete?

There’s a consistent stream of articles in both the popular and the scientific press about the next great construction “advancement,” 3-D printing. Futuristics predict that 3-D printing will rapidly revolutionize the concrete construction industry. There’s some truth in this prediction, as two traditional formwork manufacturers, Peri and Doka, have invested in start-ups that now offer 3-D printers for concrete elements. In addition there a handful of independent start-ups also offering franchise territories.

But while the excitement is on the rise, 3-D printing in concrete has some serious technical hurdles before being accepted in commercial construction of structures in which we live or work. One of the initial hurdles is whether the material used in the 3-D printing process is actually concrete, and if so, how do we test it?

The material used to create the layers of a 3-D-crafted element can appear to be mortar-like, and thus very different than fresh concrete. Some printing processes even employ layering materials that are geopolymers. And just as important, how do these materials compare in performance and service to cast-in-place or precast concrete? Should these 3-D printed structures be tested as assemblages, as are many masonry materials, testing the bonding of each layer?

The concrete and masonry industries have adopted several hundred standard testing procedures for both ingredients and mixtures. Common testing procedures such as slump, and breaking of cylinders and and prisms to determine strength, have almost a century long legacy. But how does the material coming from a 3-D printer compare to traditional concrete? Acceptance of 3-D printed concrete would be aided if there were approved consensus methods to compare to current material standards.

Fortunately, there a number of material scientists who are taking on the challenge of developing test procedures for materials that will be used in 3-D printing. And these professionals want to share the current status of their results and will do so at the Symposium on Standards Development for Cement and Concrete for Use in Additive Construction, scheduled for 1:00 p.m. to 4:00 p.m. on Monday and Tuesday, December 7 and 8, 2020. The virtual symposium is sponsored by ASTM Committees C01 on Cement and C09 on Concrete and Concrete Aggregates and is a follow-up to the  ASTM International Conference on Additive Manufacturing (ASTM ICAM 2020).

The organizers’ goal is to present potential test methods for additive construction that may be standardized through ASTM’s standards development process. Researchers will discuss a wide range of procedures for both fresh and hardened materials. The topics include measurements of early-age material properties (prior to initial setting), setting time, shape stability, print stability, compressive strength, and durability.

The event is free to the concrete industry, but it requires pre-registration Registration for Symposium on Standards Development for Cement and Concrete for Use in Additive Construction is now open and will close on November 30. For more information click here or visit the symposium's webpage at http://www.astm.org/CementDec2020Reg