Cementitious and polymeric materials for aerial additive manufacturing

Abstract

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.

Date of Award	17 Jun 2020
Original language	English
Awarding Institution	University of Bath
Supervisor	Richard Ball (Supervisor) & Paul Shepherd (Supervisor)