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0.25% of 3D-Admix is required to transform normal concrete into SpaceCrete mix, the company stated

California-based start-up SpaceCrete has said that it has developed an admixture and inline-delivery system that allows 3D printing (or rapid slip forming) with standard pumpable concrete. The company is the brainchild of civil engineer and serial inventor Michael Butler.

According to a report, the system is not yet commercially available, however it is covered by US patents with EU patents pending.

"We work at the interface between machine control and finished concrete structure. We developed the admixture and delivery system that allows vertically-shaping fluid concrete, rather than traditional forming. The vertical shape can be defined by simple or sophisticated construction hardware or new technology – such as 3D printing – but using essentially normal concrete," explained Butler.

The SpaceCrete system is said to use inline mixing to modify the pumped concrete with a special admixture called 3D-Admix. According to Butler only 0.25% of 3D-Admix is required to transform normal concrete into SpaceCrete.

He stated, "A five-inch [127mm] slump becomes zero slump inline – but with extreme shear thinning – so you can still pump it and work it as needed." He added that extreme shear thinning means that vibrating SpaceCrete consolidates it thoroughly, locking it into place and enabling it to build up vertically.

As SpaceCrete allows pumped concrete to be ‘stacked’ vertically without forming, it opens up many new ways to build with the material.

"Normal delivered concrete can become 3D print material with a very low dose of 3D-Admix injected into the pump line. Or you can slip-form vertically very rapidly with pumpable concrete. The form pressure is gone the moment you stop vibrating it," remarked Butler.

Using a vertical screed rail, you can define a finished vertical plane of concrete as fast as you can pump it, Butler notes.

"This allows you to place solid concrete walls over rough excavations, insulating foam panels, or any vertical surface. SpaceCrete really is a new concept, and sceptical contractors are very impressed. It is way greener and cheaper than 3D-print mortars; but our method development is rapid-light slip forming, not 3D-printing," he continued.

SpaceCrete meets all existing US codes and is "a healthy replacement for noxious shotcrete", according to Butler.

The report noted that Butler is now looking for commercial partners to help perfect SpaceCrete and make it commercially available. "We are solely a method and material R&D developer on a very low budget. We would like to share our knowhow, trade secrets and IP [intellectual property] with an established construction-related business, preferably one having significant manufacturing and/or marketing infrastructure in place," he explained.

SpaceCrete is currently making samples of 3D-Admix available in small quantities, the report concluded.