Holistic Investigation of Robotically Assisted 3D Printed Cob Walls: From Fabrication to Environmental Impacts
Date
2021
Authors
Mohamed, Gomaa
Editors
Advisors
Soebarto, Veronica
Griffith, Michael
Jabi, Wassim
Griffith, Michael
Jabi, Wassim
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Thesis
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Abstract
The rapid increase in the adoption rate of large-scale 3D printing into the
construction industry has revealed a number of potential applications. This rapid
implementation has also led to a higher degree of construction process optimisations
and increased ability of mass customisation. Most existing applications of 3D
printing technologies in construction are, however, heavily dependent on concrete
and other cement-based materials, resulting in a pursuit to explore other building
materials with lower environmental impact and higher adaptability to natural
contexts. This pursuit has led to re-approaching earth materials and architecture to
be applied in modern constructions.
For centuries, earth architecture has offered potential solutions for several problems
associated with buildings, such as high CO2 emissions, high embodied energy of the
construction process, and depletion of natural resources. Yet this method of
construction is possibly on the edge of extinction as its slow and very labourintensive
process requires highly skilled craftsmen. Thanks to digital construction
methods and technologies, earth materials can now become a key to promoting a new
range of sustainable construction solutions that are adaptable to a local context. ‘Cob’
stands as one of many types of earth construction methods that has been utilised all
over the world. Its mix consists of subsoil (earth), water, and fibrous material
(typically straw), and its construction can comprise a variety of geometries and
design goals without the need for formwork or any mechanical compaction method. The main aim of this research is to leverage the qualities of conventional cob
construction as a groundwork for digital innovation through robotic-supported 3D
printing (3DP) techniques. This aim has been approached through a comprehensive
feasibility assessment of 3DP cob walls. The feasibility study included four main
lines of exploration. First is the material fabrication and design process. In this line,
the research systematically explored the relationship between the revised cob recipes
and the geometrical and design characteristics offered by the new 3DP system. The
findings of this exploration provide a new understanding about the opportunities and
challenges of the current 3DP cob process, which becomes the basis to develop a
novel 3DP system for earth-based materials.
The second line examined the structural feasibility of using 3DP cob walls used in
low-rise residential buildings. This investigation involved monotonic axial
compression tests, in addition to a numerical modelling via Finite Element Analysis
(FEA). The results proved the ability of 3DP cob load-bearing walls to support a
two-storey residential house and meet building regulations. The test also established
an optimised design chart, describing the relationship between building design and
the loadbearing capacity of 3DP cob buildings.
The third line of exploration involved investigating the thermal conductivity of 3DP
cob walls. The assessment has revealed a lower thermal conductivity of 3D printed
cob (as low as 0.32 W/mK) compared to its manually constructed cob counterparts,
which means using 3DP cob for the building walls would potentially reduce heating
and cooling energy use in the building. The fourth exploration focused on assessing the environmental impacts of 3DP cob
walls using a Life Cycle Assessment (LCA) method, from cradle to site. The results
showed a superior environmental performance of 3DP cob over the concrete-based
construction methods while providing the same structural functionality in a onestory
house. The results also indicate that the use of renewable energy resources
can further boost the environmental potentials of 3DP cob for future
construction.
In summary, this research brings 3DP cob construction closer to full-scale
applications. On a broader scale, the study contributes to the disciplines
of architectural design and construction by providing a framework capable of
bridging the knowledge gap between vernacular modes of architecture and
contemporary digital practice. Moreover, this technology is not exclusive for new
buildings as it can potentially be a useful strategy for conservation and
repairing existing cob buildings. This is expected to benefit architects, designers
and researchers currently looking into indigenous crafts as a source of material
and design knowledge for a revisited digital-based architecture.
School/Discipline
School of Architecture and Built Environment
Dissertation Note
Thesis (Ph.D.) -- University of Adelaide, School of Architecture & Built Environment, 2021
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