Fresh Properties and Autonomous Deposition of Pseudoplastic Cementitious Mortars for Aerial Additive Manufacturing

Additive Manufacturing (AM) in relation to the construction industry is an emerging technology. However, ground-based AM on construction scales may be limited by the dimensions, reach and weight of the ground-based deposition platform. Aerial additive manufacturing (AAM) can revolutionise construction-based AM by employing multiple untethered unmanned aerial vehicles (UAV, known as 'drones') depositing material using miniature deposition devices. This study investigates aerial platform and cementitious material requirements for AAM and details development of structurally viable cementitious composite material with suitable rheological properties to demonstrate AAM as a novel aerial approach to complement ground-based activities. A synergistic combination of natural hydrophilic and partially synthetic hygroscopic polymeric hydrocolloids was developed in cementitious material to achieve optimal rheology properties in the fresh state. Analysis involved oscillation and flow tests, calorimetry, microscopy, computed tomography and mechanical tests. AAM application considerations focused on technical characteristics of UAV platforms, flight times, payloads and developed extrusion systems with optimal nozzle dimensions. Results demonstrate critical material parameters of 1700 kg/m3 density, 4° phase angle, 1.1 kPa yield stress, < 10 MPa complex modulus, and the ability to be processed through miniature deposition devices with 500 N force and 250 mA current. Material extrusions were realised using a custom-designed miniature deposition system which a UAV can carry and power. AAM will significantly impact automated construction by enabling new advances in aerial platform applications featuring multiple coordinated agents depositing bespoke material. This is particularly relevant to elevated or challenging construction conditions where an automated aerial approach can crucially reduce safety risks.