Octet-truss engineered concrete (OTEC) for lightweight structures
This is one of three linked projects on architected polymer–concrete composites, developed with Professor Claudia Ostertag (Civil and Environmental Engineering): octet-truss engineered concrete · polymer lattice-reinforced concrete · polymer–PCM lattice concrete.
The common idea is to borrow from the mechanics of architected cellular materials. Stretching-dominated lattices, such as the octet truss, carry load axially through their struts and so are far stiffer and stronger for their weight than foams with random pores. We use that geometry in three ways: as the concrete itself, as a 3D-printed polymer reinforcement inside concrete, and as a hollow printed container that both reinforces concrete and stores heat.
Ultra-high-performance fiber-reinforced concrete (UHP-FRC) is strong enough that much of it can be removed without giving up useful strength, provided the remaining material is arranged efficiently. In octet-truss engineered concrete, the concrete itself forms an octet-truss lattice, so that the void space is engineered rather than random. The voids also give the material the thermal-insulating benefit of porous concrete.
Parham Aghdasi, Ian Williams, Brian Salazar and Nicole Panditi developed UHP-FRC and “green” UHP-FRC mixtures, cast OTEC unit cells 50.8 mm across with a range of strut diameters, and cast five-cell beams for four-point bending. The unit cells deform in a mainly stretching-dominated way, and their compressive strength considerably exceeds that of foamed green UHP concrete with randomly oriented pores. That makes OTEC a promising route to lightweight structural elements.
Banner: 3D-printed octet-truss pattern (left), a cast UHP-FRC octet-truss unit cell (center), and an OTEC beam specimen (right). From Aghdasi et al., Composite Structures 207, 373 (2019).
Key publications
[J25] P. Aghdasi, I. Williams, B. Salazar, N. Panditi, H. Taylor, and C. Ostertag, “An octet-truss engineered concrete (OTEC) for lightweight structures,” Composite Structures, vol. 207, pp. 373–384, 2019. doi:10.1016/j.compstruct.2018.09.011 (open-access version)
[C10] P. Aghdasi, I.D. Williams, B. Salazar, H.K. Taylor, and C.P. Ostertag, “Ultra-high-performance fiber-reinforced cementitious composite octet lattice unit cells,” in Proc. First International Conference on Concrete and Digital Fabrication, Zurich, Switzerland, Sep. 2018.