Construction projects using emerging bio-based materials have been realized over the past ten to fifteen years within Europe. Bio-based buildings utilize properties of natural materials to regulate internal environments, particularly fluctuations in temperature and relative humidity. Despite individual exemplar projects demonstrating functional performance and long-term operational cost savings, there hasn’t been a proliferation of commercial or domestic bio-based projects. With a growing shift towards circular economy construction, bio-based buildings could be readily adopted to meet this development. This study evaluates barriers faced by bio-based materials, making the upscaling of production and a breakthrough into mainstream construction challenging. Evaluation was achieved through senior professionals with experience in bio-based construction participating in semi-structured interviews based on core categories of finance, knowledge, and policy. Challenges include the upscaling of production by manufacturers of emerging materials, inconsistencies in life cycle assessment, material certification and accreditation, vested interests in the construction industry, and concerns regarding initial costs, availability, and knowledge of products. Potential solutions for upscaling bio-based construction are identified and include increased case studies, positive legislation, regional economic regeneration, the wellness agenda, long-term economic sustainability, and engagement with established construction companies. This insight has informed the procurement process, material evaluation, and adoption of policy.

This paper describes the first aerial additive building manufacturing system developed to create and repair civil engineering structures remotely using polymers extruded from unmanned aerial robots (drones). The structural potential of three commercially available expanding polyurethane foams of varying density (LD40, Reprocell 300 and Reprocell 500), and their feasibility for deposition using an autonomous flying dual-syringe device is described. Test specimens consisting of one and two layers, with horizontal and vertical interfaces, were mechanically tested both parallel and perpendicular to the direction of expansion. LD40 specimens exhibited ductile failure in flexural tests and provided evidence that the interfaces between layers were not necessarily regions of weaknesses. Hand-mixed specimens of Reprocell 500 possessed compressive strengths comparable to those of concrete and flexural strengths similar to those of the lower range of timber, though they exhibited brittle failure. There are challenge...

Additive Manufacturing (AM) methods in the construction industry typically employ ground-based deposition methods. An alternative to transform the role of AM in construction is to introduce an aerial capability. A recent project titled Aerial Additive Manufacturing (AAM), the first AM system to use untethered, unmanned aerial vehicles (or ‘drones’), has demonstrated the 3D-printing of cementitious materials during flight. An autonomous aerial system would minimise requirements for working at height, thus reducing safety risks and release AM from ground-based constraints. This study investigates viscous cementitious mortars for AAM. To assess workability and buildability, a robotic arm representing UAV movement in three-dimensional space moved a lightweight deposition device to extrude multiple layers. Constituents such as Pulverised Fuel-Ash, Silica fume, polyol resin, limeX70 and Polypropylene fibres were added to cement-based material mixes. Sand:binder ratios were a maximum of 1.00 and Water:binder ratios ranged from 0.33–0.47. Workability and buildability of mixes were evaluated using performance parameters such as power required for extrusion, number of layers successfully extruded, the extent of deformation of extruded layers and evaluation of mechanical and rheological properties. Rheology tests revealed mortars with a suitable workability-buildability balance possessed a Complex modulus of 3–6 MPa. Mechanical tests showed that resistance to deformation and buildability positively correlate and indicate compressive strengths in excess of 25 MPa. This study has demonstrated that structural cementitious material can be processed by a device light enough to be carried by a UAV to produce an unsupported, coherent multiple-layered object and further demonstrated the feasibility of untethered AAM as an alternative to ground-based AM applications in construction.