Search

This study documents the evolution of cementitious and polymeric material development for aerial additive manufacturing (AAM). AAM is designed to bring multi-agent aerial mobility to additive manufacturing (AM, also known as 3D-printing) in the construction industry, in order to create or repair structures in challenging environments, ranging from working at height to post-disaster reconstruction. AAM involves coordinated unmanned aerial vehicles (UAVs - commonly referred to as 'drones') carrying lightweight deposition devices extruding material through a nozzle while in-flight. Prior to this study, investigations into AM construction involved large printing frames or ground-based robotic arms. AM can benefit the construction industry. With the extrusion method, a printed object is built up one defined layer at a time, only depositing material where required thus reducing wastage. Increased automation can reduce labour costs, formwork costs, accidents and fatalities, while offering bespoke design at minimal extra cost. However, the absence of formwork is a major challenge for 3D-printable construction materials while in the fresh state. Suitable rheological properties are needed, as material must possess sufficient workability to pass through a deposition system, yet retain the required buildability, following extrusion, to resist deformation due to subsequent layers. High-density polyurethane foam material was investigated. Cured foam was structurally viable, but fresh properties prior to curing proved rheologically unsuitable for formwork-free extrusion due to excessive lateral deformation. Focus then turned to cementitious materials and the development of novel pastes and mortars suitable for in-situ AAM in a range of environmental temperatures. Mixes are ordinary Portland cement-based and feature a wide range of additives and admixtures. Material was extruded from miniature deposition devices while attached to coordinated flying UAVs following pre-programmed trajectories. Suitable structural material possessed shear-thinning properties promoted by a combination of pseudoplastic hydrocolloids. Fibre volumes were up to 1% for structural compressive material 1700 kg/m3 and 2% for ductile material 1400 kg/m3. Cementitious material developed in this study shows the potential for AAM to be used for rapid, high precision repair work in infrastructure, elevated, marine or tidal applications, in addition to the creation of innovative lightweight structures.