3D Printable Self Reinforced Strain Hardening Cement Composite Developed at University of Michigan

Concrete has been in use as far back as 6,500 BCE when the Bedouins in Southern Syria and Northern Jordan used it in construction. More famously, the Romans used concrete to build structures such as the Colosseum and the Pantheon. Their mixture was made of quicklime and a type of volcanic ash that was then mixed with a pumice aggregate. The development of concrete for construction allowed the Romans to explore forms that would have been otherwise unthinkable had they needed to be constructed with stone. It also enabled them to build more quickly as concrete allowed them to mask small inaccuracies and eliminate the quarrying and transport times associated with stone construction. Their concrete, the recipe for which was lost during the Middle Ages, had the same amount of compressive strength as modern Portland cement. This meant that it could bear weight placed upon it to the same degree. However, because it was not reinforced, the tensile strength, which measures its capacity to resist being pulled apart, was far less.

Modern concrete is reinforced with additional materials in order to compensate for its tensile deficiencies. The first method for reinforcing concrete was the introduction of rebar into the wet mixture that would then harden in place. Other materials that are now used to improve the tensile strength of concrete are polymers or mixtures of additional composite materials either with or without additional support from rebar. This type of reinforcement is especially important in areas where the buildings might be exposed to stress and shocking, such as regions prone to earthquakes and seismic activity.

As 3D printing has continued to make inroads into the construction industry, the search for the perfectly printable concrete has been hot and heavy. Now a research team from the University of Michigan is introducing a material that just might create the magic that the construction industry has been looking for. They are not the first to approach the creation of the perfect printable construction material, but there are some key differences in this new Engineered Cementitious Composite (ECC) as lead researcher Daniel Soltan explained:

“[W]hile other printable concretes have included polymer fibers, this is the first printable cementitious composite that exhibits strain-hardening behavior, which is what makes it ultra-durable, self-healing, and bendable/stretchable. This bending/stretching occurs only at loads above the point at which traditional concretes would crack/fail. Not only does the printable ECC bend/stretch at these excessive loads, but it continues to carry an INCREASING load, even as it is accumulating “damage” in the form of microcracks.”

Soltan, who works in the Office of Technology Transfer and holds a PhD in Macromolecular Science and Engineering, has written a paper explaining the intricacies of the materials which he and his team expect to be published in the next several months in the Journal of Cement and Concrete Composites. While we must wait for all of the details regarding the material and its processes until the publication of the paper, in the meantime, it is possible to envision the kind of tectonic shift this could create in the practice of contemporary architecture. Its potential was succinctly expressed by noted architect and critic Matthew R. Dudzik, AIA:

Printed ECCs (blue curves) outperformed cast versions of the same composition (red curves) in direct tension, sided by the high degree of control over fiber alignment.

“The replacement of steel rebar for readily available polymer fibers and the general reduction of cement needed, due to the extra strength rendered from this material, allows this product to be environmentally friendly. While the material does have attributes that lend themselves to printability the process through which ECC is printed is not yet fully clear. Should the process of printing ECC allow it to, as 3D printed items typically easily do, generate non normative geometries this could have huge implications on our built environment. Given the increased performance attributes of ECC coupled with the architecture and design possibilities of the digital age could allow the material to easily realize spaces that today remain conceptual.”

That will be the true measure of the value of this product: not simply the mechanization of something that humans could do, but rather the creation of possibilities for forms previously out of reach. That is the ‘talent’ of 3D printing and fundamental to the nature of its contribution to the world of creation. If so, this could be only the beginning of the development of a new vocabulary for architecture, much in the same way that concrete first moved the conversation from the post and lintel and to the arch and vault.

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