Xeric Morphologies. MAA Thesis - C-Biom.A Studio IAAC

XERIC STRATIFICATIONS

STEFANA ZAPUC

C-BIOM.A THESIS STUDIO 20/21 MAA02 MARCOS CRUZ KUNALJIT CHADHA

xeric stratifications author: Stefana Zapuc supervisor: Marcos Cruz Kunaljit Chadha Institute of Advanced Architecture of Catalonia

Master in Advanced Architecture II (maa02) September, 2021 Barcelona, Spain

Thesis presented to obtain the qualification of Master Degree from the Institute of Advanced Architecture of Catalonia.

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acknowledgements

I would like to thank our thesis studio supervisor, Marcos Cruz, for his support in completing this research project. His always constructive critiques and creative inputs were a source of inspiration and motivation for pushing the bio-architectural boundaries throughout the entire year.

Secondly, I would like to mention Kunal Chadha’s contribution and thank him for his immense help throughout the fabrication process. His suggestions and assistance in setting up the robotic strategies made the completion of the prototypes possible.

I would also like to acknowledge Ricardo Mayor’s support and patience while introducing us to robotic fabrication, as well as his help with any technical issues encountered along the way.

Lastly, I would like to thank Mümin Keser, for sharing his Houdini knowledge and helping us develop our computational skills.

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Fig. 1. Desertified Land Overview (Fertile riparian areas in desert and dry mountain ranges. Cherlet et al., 2018).

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preface DESIGNING WITH BIOLOGICAL SYSTEMS

The project is formulated in the context of climate change and the need for the proactive integration of biology into emergent design agendas.

Biology is a fundamental aspect of all living matter that is frequently overlooked in the way the designs for the living are being conceived. Biological systems can serve as a model for both the integration of environmentally impacting abilities and their embedded geometrical, structural, and functional systems.

The core ideas explored in this thesis are built upon design philosophies that embrace growth as an intrinsic part of an architecture that facilitates growth conditions as design parameters. The world of bacteria serves as a starting point for formulating the main intent, which looks at creating new ways of designing relationships between the inert and the living.

The microbiome becomes a model for the mediation between Growing Matter as Design Matter.

Strategically, the research aim arises from the study of soil and the micro bacterial world it unveils.

Comprehending soil’s structure, substrates, nutrient cycles, and the overall ecosystem it affects could be the base for starting to design with nature rather than against it.

Recognizing the impact of soil depletion upon the ecosystem establishes the relevance of employing the use of natural materials and living matter as essential design principles, together with the implementation of advancing fabrication technologies, for the development of novel bioarchitectural morphologies.

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abstract

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abstract

During the past decades, agriculture has been depleting the soil, due to the increased chemical use and harmful practices that damage the microbes and microorganisms in the topsoil. When soil is damaged, it loses its capacity to store carbon, releasing it back into the atmosphere.

The permanent decline in the quality of soil, vegetation and water resources are contributing factors in causing the deterioration of the economic productivity of the land and disrupting the ecosystem and the micro and macro climates (Mcsweeney, 2019). This process is known as desertification.

The research focus of this paper emerges from the potential of restoring degraded soil, which displays a storing capacity of up to 3 million tons of carbon annually. The aim of the thesis is thus to investigate, test and experiment soil bioremediation strategies, by rethinking the properties of desertified soil, from an exhausted material towards a zero-emission building material alternative.

The process involves developing a biomaterial derived from sand, composed of natural binders that provide durability and allow for robotic fabrication implementations, while seeking to reintroduce gradual remediation into infertile soils.

To achieve this, the research will follow three phases: material experimentation (1), extrusion prototyping (2), and architectural application and contextualization (3).

Using bioconstructors such as the Sabellaria Alveolata as a model species, the initial stage (1) consists of understanding the biological and chemical processes of cementing together particles of sand and rock by secreting adhesive enzymes and binders. Consequently, a series of materials experiments are set up, by mixing natural binders with aggregates and altering the resulting compositions into an extrudable material.

Driven by computational form-finding and algorithmic strategies, the proposal aims to achieve structurally complex geometries fabricated through robotic suspension printing techniques (2), that challenge the idea of architectural cantilevers. The second phase thus investigates support-based 3D printing methods, establishing a stratification system based on the alternating deposition of sand as a support medium and as a building biomaterial.

Finally, the defined geometrical morphologies and fabrication techniques are addressed at an architectural scale (3), through the proposal of a series of canopy networks inhabiting the xeric lands of the Canary Islands.

key words desertification, bioremediation, suspension 3D printing, infertile soil composite, sand binding, robotic fabrication, sand as reusable support, cantilevering prototype

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index

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abstract

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index

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introduction

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03.1. Matter interchanges and cycles between biological and built environments 03.2. FRAMEWORK. Defining Desertification 03.3. FRAMEWORK. Soil fertility and Biosequestration 03.4. FRAMEWORK. Soil Microbiome

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17 19 21

03.5. Scientific Interest Research Questions Thesis Statement Research Aims Objectives & Methodology

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03.6 State of the Art - Prototypes using sand as a base material

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material experiments

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04.1. Bioadhesive species & enzymes 04.2. Natural Binders Catalogue

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04.3. Sand Solidification Series A. Sodium thiosulfate Series B. Arabic gum / Pine resin Composite Materials

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04.4. Strength tests

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05 06 07

extrusion experiments Altering the consistency of the material into an extrudable paste

geometrical studies

fabrication development 07.1. Suspension 3D printing 07.2. State of the Art 07.3.Redefining Suspension printing techniques

final fabrication strategy + prototyping

78 80 83 87 101

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08.1. Robotic stratification of sand support

08.4. Prototype Series C

114 118 126

architectural application

143

09.1. Context + Site Location 09.2. Design Methodology

146 152

09.3. Final Design 09.3. Final Prototype 1:20

158 162

08.2. Prototype Series A 08.3. Prototype Series B

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Multi material morphologies

07.4.A. Gel as support 07.4.B. Sand as support

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conclusions

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bibliography

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introduction

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introduction

MATTER INTERCHANGES AND CYCLES BETWEEN BIOLOGICAL AND BUILT ENVIRONMENTS

Soil is a fundamental element in the environmental carbon cycle. Containing more microorganisms in a few grams than the total number of people on earth, the study of soil represents an essential model for understanding biological interactions from micro to macro scales.

In the context of climate change, soil has been receiving increased interest, due to its capacity to act as a natural sink for carbon. This intrinsic characteristic of soil displays immense storage capacity, being able to hold more carbon than both plants and atmosphere combined (Tickell, 2020).

However, when depleted of its nutriments, devoid of organic matter and turned into dust, soil no longer possesses the capacity to biosequester carbon. This phenomenon is currently occurring on large scales. Desertification rates have been increasing during the past decades, with the implementation of harmful agricultural practices. As a consequence, the global land area currently covered by drylands measures over 46.2% (Mirzabaev et al., 2019), with 24 billion tons of fertile soil being lost every year (UN, 2019). Desertified lands are characterized by sandy soils, the most infertile group of soils, lacking organic matter and thus being unable to sustain growth.

Parallelly, the built environment is one of the largest contributors to the overall carbon emissions, from production to use. Since the Industrial Revolution, there has been a 50% increase in atmospheric CO2 emissions (Zomer, Bossio, Sommer and Verchot, 2017). That period was also the early stages of the built environment starting to shift from the use of raw materials to the mass production of synthetic ones, from the organic to the inorganic (Grigg, 1987).

The data points to an increased necessity for addressing this issue through “new design techniques for building systems and technologies” (Meggers et al., 2012). This paper investigates one of the many potential solutions, by taking advantage of the storage characteristics of soil and by looking at the reintegration of organic matter into advanced building techniques.

Agricultural lands are estimated to be responsible for 24% of global greenhouse gas (GHG) emissions (Zomer, Bossio, Sommer and Verchot, 2017), while the building construction industry for 39% building sector (UN, 2020). Combined in an effort to absorb carbon emissions rather than produce them, the two fields have the potential to contribute towards the interlink of biotechnology, material sciences, and architecture.

The core idea brought forward in this research originates thus in rethinking the matter of soil as a construction material. However, instead of employing the use of fertile soils, the proposal inquires the possibilities of repurposing the depleted soil caused by desertification, by biologically inoculating it with organic matter and photosynthetic bacteria, solidifying it, and building with it through advanced fabrication techniques.

In areas affected by desertification, the possibilities of utilising local raw materials rich in organic matter are limited. In this case, the use of conventionally disregarded resources, such as infertile soil, can become an opportunity not only for environmental remediation, but also for a new type of bioarchitectural morphologies.

The thesis aims to address the global issue of desertification by starting from its smallest element: a grain of sand.

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Fig. 2. Impact of Desertification on Soil Fertility (Pixabay image, n.d.)

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desertification [RESEARCH PROBLEM ]

DEFINING DESERTIFICATION (term for land degradation) Degradation includes the temporary or permanent decline in quality of soil, vegetation, water resources or wildlife.

It also includes the deterioration of the economic productivity of the land – such as the ability to farm the land.

24 BILLION TONS fertile land lost every year ISSUE

DESERTIFICATION

24 BILLION TONS fertile land lost every year

AIR POLLUTION

50 %

increase in CO2 emissions since 1990

URBANIZATION

3.5 BILLION PEOPLE live in cities today

OPPORTUNITY RESTORATION of degraded land has the potential to store up to 3 million tons of carbon annually

CARBON SEQUESTRATION and the integration of bioreceptive strategies within the urban design

SUSTAINABLE URBANIZATION and the integration of BIOMATERIALS in the construction industry

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CARBON CYCLE

CAUSES OF SOIL DEPLETION

INTENSIVE HARMFUL AGRICULTURAL PRACTICES

NATURAL PROCESSES// EROSION

inorganic fertilisers heavy metals

CO2

EFFECTS Soil is broken up and its natural structure is destroyed, killing many of the vital bacteria and fungi that live there and eventually harming the ecosystem.

CO2 BIOREMEDIATION adding microbes and nutrients back into the soil

PRIMARY TEXTURES OF SOIL

CLAY

Fig. 3. SANDY SOIL (Clerk, 2018)

sandy clay sandy clay loam sandy loam

Fig. 4. INFERTILE SOIL

silty clay clay loam

silty clay loam

loam

silt loam

SAND

SILT

(Erskine, 2020)

Fig.5. SOIL EROSION

(Weyerhaeuser, n.d.)

CLAY

SAND

SILT

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soil fertility and biosequestration [ FRAMEWORK ]

To recognize the underlying causes of desertification, the fundamental structure and biodiversity of soils must be understood. Being regarded as the main reservoir of biodiversity (Bardgett and van der Putten, 2014), soil ecosystems consist of countless micro-organisms that control and regulate growth, water intake and circulation, as well as carbon and nitrogen storage and cycles.

One gram of soil is estimated to be comprised of about 1 billion bacterial cells (FAO, ITPS, GSBI, SCBD and EC, 2020). Functionally, the bacteria have essential roles in secreting substances that ‘bind soil particles together, further enhancing soil aggregation’, porosity, water retention, and providing improved structures for plant roots (Costa et al., 2018).

These bacteria are hence the core elements of soil fertility.

SOIL AND CARBON SEQUESTRATION

As previously mentioned, a vital soil function is its capacity to biosequester carbon. This process is achieved though the production of a carbon glue called glomalin, that is secreted by soil mycorrhizal fungi, and that is responsible for the storage of carbon absorbed from the atmosphere. The system relies on the creation of ‘pocket-like’ microbiomes, that fix the carbon and regulate water and air circulation (Wallenstein, 2017).

However, in the case of desertified (infertile) soil, these micro-organisms and most of the organic matter is absent. Normally, topsoil contains abundant organic matter quantities. This is the result of decomposed plant and animal tissue and is protected by soil aggregates.

When agricultural production resorts to tilling or the use of inorganic stimulants, these aggregates are destroyed, exposing the organic matter to eventually be eliminated.

In this circumstance, soils lose their fertility and their inherent capacity to biosequester carbon (Wallenstein, 2017).

SOIL TYPOLOGY BY TEXTURE

Based on their texture, soils are mainly classified into sand, clay and slit, with subcategories derived from their mix in various proportions, as seen in the attached diagram. Soil texture is influenced by its fertility levels, as they are a direct cause of organic matter presence and structural ability to retain nutrients and control water flow.

Consequently, sandy soil is considered the most infertile, being unable to sustain growth.

MAIN CHARACTERISTICS OF DESERTIFIED SOIL

erosion loss of soil biodiversity

increasing salinity nutrient imbalance acidification pollution water logging compaction

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Fig. 6. Cyanobacterial Crust (Nagovitsyn, 2011)

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soil micorbiome

[ CYANOBACTERIAL GROWTH AS A METHOD OF SOIL REMEDIATION ]

Amongst experimental approaches for restoring infertile soil, demonstrated to function as sustainable strategies, Bioremediation stands out for employing the use of microorganisms such as bacteria or fungi (Fingerman and Nagabhushanam, 2005).

The process of bioremediation presents three main methodologies, including ‘natural attenuation’ (microorganisms removing contaminants), ‘bioaugumentation ’(bacterial inoculation), and ‘biostimulation’ (altering environmental conditions) (Park et al., 2011; G. Lacalle, M. Becerril and Garbisu, 2020).

One species that have proved effective in bioremediation research are cyanobacteria, displaying promising capacities of removing environmental pollutants and stabilizing desertified soil (Lau, Matsui and Abdullah, 2015). Cyanobacteria are free-living photosynthetic bacteria, also known as ‘green-blue algae’, present in numerous extreme habitats ranging from aquatic to terrestrial; they can occur in areas including barren soils, rocks, or Antarctic environments (Marine Life Database, 2020).

In xeric environments, cyanobacteria are commonly found in the form of cyanobacterial crusts (or biocrusts), formed on the top surface of the soil. These crusts are regarded as a potential solution of degraded soil restoration (Park et al., 2017), as their presence promotes beneficial habitats for soil biota (Liu et al., 2011).

The inoculation of cyanobacterial specimens as a method for promoting the growth of biocrusts has been the focus of various research aimed at soil remediation through novel biotechnological strategies (Chamizo et al., 2018). Additionally, cyanobacteria display the capacity to fix carbon and nitrogen in soil (Singh, Kumar, Rai and Singh, 2016), further enhancing its beneficial impact when reintroduced into infertile soils.

CYANOBACTERIA

GROWTH HABITATS

aquatic habitat

lichens Fig. 7.

plants Fig. 8.

protists Fig. 9.

CYANOBACTERIA

Fig. 12.

AQUATIC HABITAT BIOFILM

Fig. 13.

terrestrial habitat sponges Fig. 10.

sloths Fig. 11.

Fig. 7 (Pixabay, n.d) Fig. 8 (Fay-Wei Li/BTI, n.d.)

Fig. 9 (Shutterstock, n.d.)

Fig. 10 (Freeman, n.d.)

Fig. 11 (Wu, Minden pictures, n.d.)

Fig. 12 (Bayraktar, n.d.)

Fig. 13 (McKay, n.d.)

Fig. 14 (Veste, 2011) Fig. 15 (Morlock, 2015)

TERRESTRIAL HABITAT BIOLOGICAL SOIL CRUST

Fig. 15.

Fig. 14.

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scientific interest

‘When resources are degraded, we start competing for them’ (Maathai, 2008). The enhancement of soil microbiomes represents an efficient way to transform decaying plants into soil organic matter, maximizing the amount of carbon sequestration (Cherlet et al., 2018).

The storage capacity of the soil has immense potential, being able to hold more carbon than both plants and atmosphere combined. If we started reusing bioremediated infertile soil, we could bio se-quester carbon through our buildings.

DESIGNING WITH SOIL

research questions

Can the challenges of soil depletion and resource scarcity be addressed by building with bioremediated exhausted resources?

How can infertile soil (sand) be turned into a building material?

What are the ways in which sand can be implemented into robotic fabrication strategies?

HOW CAN WE BUILD WITH DUST?

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03.5

thesis statement

Xeric Morphologies explores the potential of remediating infertile soils such as sand, by developing a solid sand composite with natural binders, that can be robotically fabricated into cantilevering morphologies though reusable sand support printing techniques.

research aims The main aim of the research is to develop a biomaterial derived from sand, as an alternative construction material to current industrialized materials and methods that produce harmful emissions.

The process involves achieving sand biocementation and developing durable, natural binders, capable of providing organic matter for the eventual growth of microorganisms and species specific to xeric environments. The dual use of sand is investigated, employing its application both as an extrudable construction material and as reusable support medium for robotic 3D printing.

On an architectural scale, the project aims to explore the capabilities of the material and the fabrication strategy to construct cantilevering structures for arenaceous habitats.

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research aims

1. Re-evaluate the environmental impact of the construction industry, by enhancing the use of natural materials within the technological and scientific advancements, in order to create sustainable cities.

2. Proposing an alternative to the current industrialized construction materials and methods that produce harmful emissions, waste, as well as air, soil and water contamination, to instead combat them.

3. Strengthen urban resilience and create a network of bioreceptive systems, capable to adapt to changing environment conditions and population growth.

SUSTAINABLE DEVELOPMENT GOALS UN, Sustainable Development Goals, 2020 COP 21, Paris Agreement, 2015, United Nations Framework Convention on Climate Change (UNFCCC) United Nations Convention to Combat Desertification (UNCCD)

GOAL 9

GOAL 11

GOAL 12

GOAL 13

GOAL 15

TARGETS:

TARGETS:

TARGETS:

TARGETS:

TARGETS:

9.4 upgrade infrastructure and industries to make them sustainable, with increased resource-use efficiency and greater adoption of clean and environmentally sound technologies and industrial processes

11.3 enhance inclusive and sustainable urbanization and participatory, integrated human settlement planning

12.2 achieve the sustainable management and efficient use of natural resources

13.1 strengthen resilience and adaptive capacity to climate-related hazards and natural disasters

15.3 combat desertification, restore degraded land and soil, including land affected by desertification, drought and floods, and strive to achieve a land degradationneutral world

9.5 enhance scientific research, upgrade the technological capabilities of industrial sectors

11.6 environmental impact of cities // air quality and municipal and other waste management

12.4 management of chemicals and all waste to reduce their release to air, water and soil

13.2 integrate climate change measures into national policies, strategies and planning

15.9 integrate ecosystem and biodiversity values into national and local planning and development processes

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objectives and methodology

The research is carried through applied research, divided into progressive phases such as: 1. Material research and experiments, for developing a recipe of sand, natural binders and aggregates 2. Fabrication experiments, from material extrudability to robotic fabrication with reusable support 3. Geometrical studies and architectural application hypothesis

OBJECTIVE 1

methodology

To conduct a series of material experiments that investigate possible compositions of natural binders through which to achieve sand solidification. To test and record the composites’ quantities and their resulting strength and durability properties, as well as their capacity to sustain plant growth.

- evaluate the performance of the material within the defined categories of suspension printing, including the use of hydrogels and sand as reusable support media - test the contribution of the support media to the consistency of the extruded material - design and build an extruder mechanism and a support deposition system - create a catalogue of the resulted prototypes - fabricate iterative prototypes, pushing the boundaries of the geometry output

methodology - research and catalogue bio adhesive binders and divide them into categories based on their type - conduct materials tests using binders from each individual category, as well as composite adhesives - record a catalogue of resulted materials, through photographs and data sheets of quantities for each material + the process - post evaluations: conduct compressive strength tests and extrudability tests

OBJECTIVE 2 To develop an additive manufacturing strategy for fabricating prototypes using the material developed in the initial stage. To fabricate structurally complex cantilevering structures developed computationally, through robotic suspension printing. To redefine the possibilities of suspension fabrication techniques in the context of the proposed material and to fabricate prototypes with the suggested system.

OBJECTIVE 3 To develop an architectural proposal that aims to bioremediate desertified soil, by supporting plant growth within xeric environments contexts. This proposal will implement the presented material and the fabrication process developed throughout the research, challenging its scalability and its potential impact onto the selected ecosystem.

methodology research and analyse a suitable site for the proposal - establish the relationship between the material prototypes performance and the collected site data, as a starting point for the design - assess and develop the geometry studies based on the scale of the proposal + implement environmental optimisation strategies - create a catalogue of design iterations

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state of the art PROTOTYPES USING SAND AS A BASE MATERIAL The first step in understanding the implications of developing a solid sand material is by evaluating existing research projects and recent developments in the field.

Using sand as a base material, the selection of the state-of-the-art projects takes into consideration three main criteria: a range of biocementation binders and composites, various digital fabrication techniques and different scales of application. The assessment methodology includes creating a comparative table of parameters for assessment, as it follows: material used for the binding process, properties of the material, solidification time, fabrication technique, scale of prototype, and integration of growth.

Here, the utilized binder is Polypavement, a commercial eco-polymer used in the solidification of soil.

The prototyping system involves an automated spray nozzle that combines particles of sand with the liquid binder on with wire scaffolding or free-form.

A prototype sample is estimated at three hours of fabrication time and one hour of solidification and drying. Discussed limitations include the height and overhang angle restrictions of the technique. The scale of the final results is categorized as medium-sized prototypes, with further digital speculations being made upon potential pavilion-scale implementations (Kulik, Shergill and Novikov, 2012).

The projects, in ascending order of their scale are illustrated on the following page.

1. Time Dune’, developed by Munro Studio, is a series of experimental material tests looking at sand solidification through supersaturated salt (sodium thiosulfate) solutions.

The fabrication technique adopts the manual application of melted salt over pre-formed sand formations. The results provide a solid, but thin and fragile crust of sand-salt material. Scale-wise, the project is categorized into a material test and smallscale prototypes, with speculative intentions upon larger architectural applications using the described technique (Munro Studio, n.d).

2. Stone Spray’ is a 6-months research project developed at IaaC by students Anna Kulik, Inder Shergill and Petr Novikov. The proposal focuses on sand binding though the design of a fabrication technique that employs a mechanized robotic arm using a spray system to deposit the materials (Stone Spray – IAAC Blog, 2012).

3. ‘Sandprint’, developed at Bartlett by Xiyangzi Cao, Shuo Liu and Zeyu Yang, is a material and fabrication research project focused on the use of sand as a casting technique.

The proposed fabrication method consists of creating a casting mold filled with sand and crossed by hollow tubes. Plaster is cast inside the tubes, utilizing the sand as support and as a surface texture coating layer. The scale of the project is realized at furniture / object sizes, in the form of columns and chairs morphologies, with further computational hypotheses upon pavilion scale structures.

The described solidification time is estimated at an hour for a prototype sample measuring 800 x 800 x 1200 mm. The project is considered for its contribution within the developed fabrication strategy and the use of sand as support, rather than a sand-binding technique ( SoomeenHahm Design, 2014).

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DUNE

TIME DUNE

MAGNUS LARSSON

MUNRO STUDIO

STONE SPRAY IAAC

SCALE: urban

SCALE: material test

SCALE: prototype

BIOCEMENTATION : bacillus pasteurii

BIOCEMENTATION : sodium thiosulfate

BIOCEMENTATION : poly pavement

SOLIDIFICATION TIME: 14 - 28 days

SANDPRINT

RC6 B-PRO BARTLETT

SCALE: prototype BIOCEMENTATION: plaster, water, glass fiber SOLIDIFICATION TIME: 1h

SOLIDIFICATION TIME: 5 - 10 min

SOLIDIFICATION TIME: in contact with surface, completely 1 hour

SANDWAVES

PRECHT + MAMOU-MANI

SCALE: pavilion / 58 individual 3d-printed elements BIOCEMENTATION : furan resin (cellulose of pine trees and corn kernels)

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4. ‘Sandwaves’, a project by Mamou Mani and Studio Precht, is considered the “largest sand-printed installation” (Mani, 2019) currently fabricated.

It consists of an undulating wall structure in the form of a pavilion and is formed by 58 modular 3D printed components assembled to-gether. The project addresses the use of natural binders, by solidifying the base sand material with furan resin, composed of “cellulose of pine-trees and corn kernels” (Mani, 2019).

The fabrication method involves the use of standard existing sand or metal printers, based on a powderprinter system, by using an ExOne large scale 3D printer. The technique involves the stratified deposition of thin resin binder layers over a bed of sand (V., 2020).

CONCLUSIONS

5. The project ‘Dune’, by Magnus Larsson, is a theoretical application of bacterial biocementation sand techniques, in the form of a masterplan modelled as an “inhabitable green sandstone”. The project deals with sand solidification through a biochemical process known as” microbially induced carbonate precipitation (MICP)” (Larsson, 2010).

The reviewed projects serve as proof of concept, as well as consolidating a base for creating a catalogue of sand binders to be further developed. This thesis aims to contribute to the presented topic, in the form of a novel sand-based material and its specific fabrication technique.

The procedure involved the injection of the Bacillus pasteurii microorganism specimens in sand, added “in a growth medium mixed with urea and a calcium source” (Larsson, 2010). Although not specified in the case of this project, similar studies indicate solidification times of laboratory samples between 14 to 28 days for 20 MPa UCS (Khan, Amarakoon, Shimazaki and Kawasaki, 2015).

The final outcome remains at a speculative level, based on the established sand biocementation tests.

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material experiments

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material experiments

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bioconstructors

SAND BIOADHESIVE SPECIES The methodology for the development of a sand binder includeds the analysis of biological species with sand-binding characteristics, in order to examine the biochemical processes and the involved substances that facilitate adhesion.

Four species were considered, including the Sabellaria Alveolata, the Burrowing Spider, the Caddisflies, and the Difflugia.

SABELLARIA WORMS

BURROWING SPIDERS

CADDISFLIES

Fig. 16 (Farr, 2018)

Fig. 17 (R. Foelix et al./Journal of Arachnology 2017)

Fig. 18 (Lemmo, 2019)

DIFFLUGIA Fig. 19 (Tsukii, 2005)

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SABELLARIA WORMS

Sabellaria Alveolata are marine worms about 30 mm long which build habitable tubes by cementing together particles of sand and rock (AskNature, 2016). The process involves binding a number of overlapping layers of sand and shell grains stuck together with mucus (Foy and Oxford Scientific Films 1982:32-33).

The agglomeration of tubes creates a stable reef substrate which increases biodiversity by providing habitat for other shore-dwelling animals such as anemones, snails, shore crabs and seaweeds such as sea lettuce (Subsea UK, Aberdeen, 2017).

BURROWING SPIDERS

Leucorchestris is a burrowing spider species that stabilizes its burrow wall with a layer of silk, produced by inserting long spigots far into the sand to stabilize and like its grains (Peters, 1992/ AskNature, 2016).

CADDISFLIES

Caddisflies are a type of aquatic larvae insects that use sand binding as a defence mechanism against predators. To do so, the specie builds protective cases, by cementing surrounding materials onto their shells such as pebbles, sand, and aquatic plants, with silk or mucus (AskNature, 2016).

DIFFLUGIA

Difflugia is a protozoan species that displays a multi-phase digestion and protection system. This consists of the ingestion of sang grains together with its food; the sand particles are later migrated towards the exterior surface, forming a protective layer bond together by a secretion (AskNatue, 2016).

Ultimately, the Sabellaria worms were selected for further investigation of their bioadhesive capabilities.

Extensive research is still being developed for a comprehensive overview of the chemical compositions and reactions of their adhesive enzymes. Characteristics that have been identified as responsible for the adhesion include: high abundance of carbon, the presence of phosphorus and nitrogen (confirming a proteinaceous composition), and the presence of polymers, calcium, and magnesium.

Overall, the major components consistently found in the cemented sand reefs are C, N, Na, Mg, P, Cl, K and Ca (based on energy) (Sanfilippo et al., 2019). Further research is conducted upon the essential functions of calcium and magnesium, found in particularly high concentrations within the secretory glands (Sanfilippo et al., 2019): “The proteins are deposited onto the sand surface as a colloidal emulsion rich in calcium and magnesium (Stewart et al., 2004) that sets within seconds”.

Separate studies validate the mechanical strength added by the calcium and magnesium, through their chemical removal using a “divalent ion chelator (EDTA)” (Sun et al., 2007). The results are characterized by half the original strength after the Ca2+ and Mg2+ ions are removed from the cement (Fantner et al., 2005).

Furthermore, the enzymes possess hydrophobic properties, displaying rapid solidification of the sand reefs after contact with seawater and high stability when interacting with shore waves.

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natural binders FOR SAND BINDING

SOLIDIFYING SAND

Using the mechanisms and principles of bioadhesion, the species are used as a model for natural binders, throughout a series of material tests aimed at solidifying sand. For the purpose of conducting the experiments, the identified enzymes and animal proteins are substituted with several available natural polymers that display similar characteristics and that target the process of binding the sand particles together into a composite.

The materials are then categorized into salts [1], glues [2], enzymes [3] and living matter [4]. The conducted tests focus on the first two classes – salts and natural glues - establishing a series of trials which use an experimental methodology to research the effect of integrating each ingredient either individually or as a composite. The outcomes are then evaluated based on their effect as a binder, a (de)flocculant, their impact on the consistency of the mix, and the overall performance of the resulting sand composite.

RETHINKING THE PROPERTIES OF DESERTIFIED SOIL, FROM AN EXHAUSTED MATERIAL TOWARDS A LOW - CARBON EMISSION BUILDING MATERIAL ALTERNATIVE

MATERIAL SOLIDIFICATION

BINDER CATEGORIES

SALTS

SODIUM THIOSULFATE

GLUES

GUM ARABIC PINE ROSIN CORN STARCH CHITOSAN CELLULOSE LIGNIN / LIGNOCELLULOSE CALCIUM CARBONATE

ENZYMES

SABELLARIA WORMS CEPHALOPODS MUSSELS

LIVING MATTER BACILLUS PASTEURII CYANOBACTERIA (Synechococcus)

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BIOMATERIAL CATALOGUE

XERIC STRATIFICATIONS |

A series of materials were researched and integrated in the mix to bind, alter the consistency or act as (de)floculants.

GUM ARABIC

PINE ROSIN

CORN STARCH

CELLULOSE

CALCIUM CARBONATE

AGAR

CHITOSAN

SODIUM THIOSULFATE

37

material experiments. sand solidification SERIES A The initial experiments (Series A) investigate the binding results of sand particles with salts [1], by using sodium thiosulfate. Varying the quantities of components, as well as the mixing process, between 10-50 grams of sand are mixed with different quantities of 5 to 40 sodium thiosulfate to test and compare the outcomes.

The salt is composed of ‘ions of sodium and thiosulfate in a ratio of 2:1’ and has the molecular formula Na2O3S2 (7). It is supplied in the form of colourless salt crystals and its main properties include solubility in water g/100ml at 20 °C: 20.9 (lo.org. n.d.) and melting point at 48.5 °C.

1. the gradual addition of the liquid solution over the sand particles (while homogeneously mixing) 2. the addition of dry sand in the solution (while homogeneously mixing) 3. the stratification of thin layers of sand and STP solution (allowing the liquid to infiltrate the sand particles without mixing) 4. pouring the liquid salt over a predetermined sand formation or dune (resulting in a solid crust being formed with the top layers of the sand).

The crystallization of sodium thiosulfate pentahydrate (STP) is performed, by boiling the salt granules at a temperature of 100°C. The result is a supersaturated solution which is then mixed with the sand particles following various experimental methods (Hussein et al., 2019.).

The supersaturated salt solidifies within minutes after being removed from the heat source, requiring a rapid mixing process. Depending on the size of the sample and the permeability of the containing mould, the sand-salt composites solidify completely after 1-2 days.

STP BINDING PROCESS

RESULTS

The production process examines the way in which the variation of parameters such as the material proportions, the melting temperature, as well as the mixing technique affect the created samples. The initial ratio follows a 2:1 parts of dry sand to STP solution, systematically adjusting the quantities to create a catalogue of comparable samples.

All the samples succeeded in producing a solid sand material. This method displays rapid solidification time, happening almost instantaneously once the supersaturated STP solution has cooled down. Further final observations include the tendency of the salt to form thin layers of crusts on the top surface of the solidified material.

The trials using a supersaturated solution demonstrate a better performance than the ones where the salt crystals are dissolved in small quantities of water prior to mixing. Different methods of combining the sand particles and the STP solution are assessed, including:

The optimal quantities are validated by the 2:1 ratio of sand to salt binder, achieved with a mixing method of STP solution over sand particles. The obtained solidified material is not hydrophobic or durable, dissolving when in contact with water or heat. The figures attached highlight the best results. These factors are critically determining the need of leading a second series of material investigations (Series B).

38

XERIC STRATIFICATIONS |

SERIES A

EXPERIMENT 1.

EXPERIMENT 2.

EXPERIMENT 3.

40 g sodium thiosulfate 80 ml water 30 g sand + 10 ml diluted solution

5 ml diluted salt solution 10 g sand

12 g salt 24 g sand (sald over sand)

EXPERIMENT 4.

EXPERIMENT 5.

EXPERIMENT 6.

20 g salt 45 g sand

15 g salt 30 g sand (salt over sand)

12 g salt 30 g sand (sand over salt)

EXPERIMENT 7.

EXPERIMENT 8.

EXPERIMENT 9.

20 g salt 55 g sand (sand over salt) cylindrical mold

10 g salt 30 g sand 1.5 g agar 0.8 chitosan 25 ml water

8 g salt 30 g sand 0.5 g agar 0.4 chitosan 15 ml water

39

SERIES B ‘Engineering design of buildings is a matter of exploiting the properties of materials for practical ends’ (Hall, 2017).

Built upon this idea, the second series consists of testing ingredients with natural glue or gum properties, including pine resin, gum Arabic and thickening agents such as carboxymethyl cellulose, chitosan, agar, starch, calcium carbonate and alginate.

Existing biomaterial engineering research largely utilizes polymers as “a major class of engineering materials” (Hall, 2017). Polymers describe large molecules, composed of structures of atom networks. Several polymers found in plants create cellulose, lignin, and resins (Encyclopedia Britannica, 2021), encompassing binding properties and displaying potential to be tested as bio adhesives in the process of developing a solidified sand composite. Organic polymers are thus a core element of living systems, providing support or acting as an energy source, by composing key biological components such as “proteins, cellulose, and nucleic acids”.

EXPERIMENTAL PROTOCOL

PINE RESIN / ROSIN

The initial binding tests are conducted using pine resin as a natural binder for the sand particles.

The resin is supplied as pellets that are melted at temperatures between 100°C - 120°C. The melted pine resin proves quite a challenging material to work with, for a number of reasons including: - solidifying excessively fast - being tough to remove from laboratory utensils - flammable - requiring high production temperatures.

Additionally, the cooling down process produces crystallization, causing the reduction of the adhesion strength of the resin glue (De Luca et al., 2018). For additional flexibility, small quantities of beeswax are introduced during the melting phase.

This makes the resin easier to work with and eliminates the formation of solid fibres. Ratios of ± 1:1 sand to resin glue are used as main quantities for the test samples. The addition of beeswax pellets outputs a more malleable material, which allows for the manipulation of the form once the materials are mixed.

The final samples achieve sand solidification, however observations of the binding process point towards combining the resin with several composites, to attain better material performance and strengthen the mix.

GUM ARABIC

The second tested material is the Gum Arabic, which acts as a glue and binder due to its structural composition of polysaccharides (or polycarbohidrates), long polymers of simple sugars, and binding glycoproteins (Mariod, 2018).

Gum Arabic is a plant-based material, naturally extracted from the sap of acacia tree species and its common uses involve its functions as a food thickening agent or as a natural binder. The gum is soluble in water and presents low viscosity levels (Mariod, 2018). The gum is available in powder form or as granules – smaller granule sizes facilitate an easier dissolving process.

The procedure is set up by initially dissolving the Arabic Gum in heated water, at a 1:2 ratio of gum to water. The resulting solution is then mixed with dry sand particles, using again a 1:2 ratio of dissolved gum solution to sand.

Consistent mixing is required throughout the combination of materials, to ensure the sand core is homogeneously bonded with the gum.

Solid samples are achieved after drying times between 5-7 days, constant exposure to air being essential in this phase. Further experiments examine the binding properties of Gum Arabic as a component in a composite material, assessing the potential improvement of the base mix, as explained in the sections below.

40

SERIES B1

EXPERIMENT 1.

EXPERIMENT 2.

1 part gum : 2 parts water 15 g gum + 30 g water solution 20 ml disolved gum (1:2) 40 g sand

1:2 gum to water solution 10 ml disolved gum solution 25 g sand

EXPERIMENT 3.

10 ml sodium thiosulfate supersaturated 4 ml gum arabic 25 g sand

EXPERIMENT 4.

EXPERIMENT 5.

EXPERIMENT 6.

20 g pine rosin 5 g beeswax 20 g sand

75 g pine rosin + 20 g beeswax solution 20 g sand + 30 g rosin solution

75 g pine rosin + 20 g beeswax solution 20 g sand + 20 g rosin solution

EXPERIMENT 7.

EXPERIMENT 8.

EXPERIMENT 9.

80 g rosin 20g wax 50 g sand

20g pine rosin 5 g beeswax 25 g sand

80 g rosin 20g wax 50 g sand (5 minutes)

EXPERIMENT 10.

EXPERIMENT 11.

80 g rosin 20g wax 50 g sand

75 g pine rosin + 20 g beeswax solution 20 g sand + 30 g rosin solution (over mold // too fibrous)

XERIC STRATIFICATIONS |

PINE RESIN / ROSIN

41

COMPOSITES

Several aggregates are integrated into the sand mix, in order to analyse the potential improvement of its properties. The tested aforementioned polymers and their characteristics include:

CELLULOSE

CORN STARCH

Varying quantities of carboxymethyl cellulose in powder form are integrated into the composite as a method of reinforcement.

Cellulose is an extremely abundant polymer, with an estimate of 1.5 trillion tonnes generated annually (Baghaei and Skrifvars, 2020). Cellulose is naturally extracted from plant or algal cells and displays high thermal stability and tensile strength properties.

Starch is introduced in the mixes as a thickening agent (Types of Thickening Agents, n.d.).

In material composites, cellulose provides biobased reinforcement, containing high crystalline fibres (Baghaei and Skrifvars, 2020). Within the tested material samples, the addition of cellulose contributed to the material strength and to an overall better consistency.

Being a polymeric carbohydrate composed of large numbers of glucose molecules, main properties of starch include its use as an emulsifier, viscosifier, and defoaming agent.

For the mixing method, starch undergoes a gelatinization process when mixed with water at temperatures above 60°C (Silva-Guzmán et al., 2018).

AGAR

CALCIUM CARBONATE

Agar is a polysachharide derived from red marine algae (Guo et al., 2021) species such as Gracilaria and Gelidium sp. (Giménez et al., 2013). Supplied in powder form, agar is soluble in boiling water and forms a solid gel when cooled down to temperatures between 34-43° (Jumaidin et al., 2017). Bacteriological agar is commonly used as a solid growth medium.

Calcium carbonate is produced from limestone and is a powder material insoluble in water (Calcium carbonate, 2021).

Using the model of the bioadhesive species discussed in the previous section, various quantities are introduced into the sand composite to test its impact on the strength of the resulting material.

Calcium carbonate’s presence in soils has proved to neutralize its acidity and act as a source for plant nutrition (Calcium Carbonate (Limestone), n.d.).

The agar is introduced initially into the material tests as a gelling and thickening agent.

Additionally, the agar hydrogel mix reintroduces organic matter into the infertile base soil.

Research into the impact of agar on different types of soil demonstrates that it aids the retention of moisture, increasing it by up to 6-10 days in the case of sand (Chaudhary et al., 2020).

42

CLAY

Chitosan is a polysaccharide derived from chitin (Cheung, Ng, Wong and Chan, 2015), mainly extracted from the exoskeleton of crustaceans such as shrimps and crabs. The shells contain proteins and calcium carbonate that give the materials added porosity, tensile strength, and structural properties (Ibrahim and El-Zairy, 2015).

Lastly, clay is added in various quantities to help bind the composites together, modify the composition into a paste-like material, and add organic matter, minerals, and fertility to the sand (clay |2021).

XERIC STRATIFICATIONS |

CHITOSAN

SERIES B2 GUM ARABIC

EXPERIMENT 1.

EXPERIMENT 2.

EXPERIMENT 3.

1.6 chitosan 1g cellulose 20 ml boiling water 20 g sand + 10 ml solution

1.6 chitosan 2 g cellulose 20 ml boiling water 20 g sand + 10 ml solutiom

25g cellulose 10 ml water 20 g sand

EXPERIMENT 4.

20 g corn starch 20 ml water 5 g cellulose 30 g sand

EXPERIMENT 4.

43

SERIES B2 GUM ARABIC + AGGREGATES

EXPERIMENT 1.

EXPERIMENT 2.

EXPERIMENT 3.

20 g rosin 5 g cellulose 5 g wax 45g sand

5 g cellulose 10 g sand

15 g rosin 3.5 g wax 7.5 g sodium thiosulfate 30 g sand

EXPERIMENT 4.

EXPERIMENT 5.

EXPERIMENT 6.

15 g calcium carbonate 20 ml water

15 g calcium carbonate 20 ml water 3 g cellulose 8 g chitosan

10 ml water 5.5 g cellulose 12 g chitosan

MANUAL EXTRUSION TESTS

EXPERIMENT 7.

EXPERIMENT 8.

EXPERIMENT 9.

20 g rosin 5 g cellulose 35 g sand

20 g rosin 5 g cellulose 35 g sand

cellulose + chitoosan + sand

44

SERIES B3

EXPERIMENT 1.

EXPERIMENT 2.

EXPERIMENT 3.

EXPERIMENT 4.

100 g sand 20 ml water 10 g clay 20 g gum arabic 10 g cellulose

100 g sand 20 ml water 20 g arabic gum 6.2 g chitosan 6 g cellulose

100 g sand 40 ml water 10 g gum arabic 10 g starch 5 g chitosan 25 g clay

100 g sand 10 ml water 25 g clay 10 g gum arabic 5.5 g cellulose 2 g calcium carbonate

EXPERIMENT 5.

EXPERIMENT 6.

EXPERIMENT 7.

EXPERIMENT 8.

100 g sand 25 g clay 50 ml water 10 g gum arabic 4 g calcium carbonate 8 g agar

100 g sand 20 g gum arabic 15 ml water

100 g sand 50 ml water 30 g clay 4 g starch 5 g cellulose

100 g sand 30 ml water 30 g clay 3 g chitosan 3 g cellulose 5 g gum arabic

7.

8.

4.

1.

5.

2.

XERIC STRATIFICATIONS |

SAND BRICKS

9.

6.

3.

RESULTS AFTER A WEEK

45

binders experiments catalogue SERIES A

SERIES B1

SERIES B3

46

XERIC STRATIFICATIONS |

SERIES B2

47

material strength tests TESTING THE STRENGTH OF THE COMPOSITES Following the solidification tests, the resulting composites are also assessed based on its compressive strength. To conduct the tests, iterations of sand + binder as well as multiple composite mixes are evaluated, in order to formulate a conclusion over the best mix to be taken further into the fabrication phase. Circular blocks of 50 mm diameter were tested, following the rule of sand + binder and the gradual addition of other aggregates, to verify their strength addition. A universal compressive strength testing machine is used to conduct the experiments, with a maximum force of 9 bars.

A comparative study between the single-binder and the multi-material composites is conducted based on their resulting strength, concluding in the overall better performance of the multi-material mixes.

1.

7cm in diameter 3 cm height Pressure: 4 bars

2.

5cm in diameter 4 cm height Pressure: 9 bars

3.

5.5 cm in diameter 6 cm height Pressure: 9 bars

4.

5cm in diameter 4 cm height Pressure: 8.5 bars

48

XERIC STRATIFICATIONS |

1. Composite: 200 g sand + 100 ml gum arabic dissolved solution (65 g gum / 25.5 ml water) 2. Composite: 200 g sand + 150g sodium thiosulfate - layers 3. Composite: 200 g sand + 60 g gum arabic + 50 g clay + 5 g cellulose 4. Composite: 200 g sand + 60 g gum arabic + 50 g clay 5. Composite: 200 g sand + 100 g clay + 30 ml water 6. Composite: 200 g sand + 60 g gum arabic + 50 g clay + 5 g cellulose + 5 g agar 7. Composite: 200 g sand + 100 g resin 8. Composite: 200 g sand + 60 g gum arabic + 50 g clay + 5 g cellulose + 5 g agar + 10 g chitosan (in green - binder only)

5.

5cm in diameter 8 cm height Pressure: 8.5 bars

6.

5cm in diameter 6.5 cm height Pressure: 8.5 bars

7.

5cm in diameter 14cm height Pressure: 4 bars

8.

5cm in diameter 4 cm height Pressure: 8.5 bars

49

extrusion experiments

05

50

XERIC STRATIFICATIONS |

05

extrusion experiments

51

52

53 XERIC STRATIFICATIONS |

54

XERIC STRATIFICATIONS |

extrusion tests MATERIAL CONSISTENCY The resulting catalogue of materials discussed in the previous section is further assessed according to its extrudability capacities, testing the consistency as well as the properties of the outputs.

SETUP The experiments are conducted by adjusting the consistency of the sand composites into an extrudable paste, strong enough to support its own weight. The extrusion tests are conducted on a modified Ender 3Pro 3D printer. The setup consists of a 3D printed extruder with a circular profile nozzle, a metal screw connected to a motor, pushing the material into the nozzle, and a cartridge connected to an air compressor.

COMPOSITES The composition of the mixture was achieved by testing various recipes of sand, clay, cellulose, Arabic gum, chitosan, and agar.

OBSERVATIONS Observations include that the granularity of the sand is an important factor in this fabrication technique, as the screw-system extruder can be easily clogged when larger particle sand is tested. A pressurebased system is recommended in this case, to eliminate the extrusion issues.

The sand makes the material denser and heavier, impacting the vertical build-up of the deposed layers.

This leads to frequent warping of the prototypes and to limited height and overhangs.

After a total drying time of 2 weeks, the print shrinks and the texture of the sand becomes more defined.

55

SETUP

MATERIAL COMPOSITION

sand arabic gum cellulose agar clay

RECIPE OF BEST RESULTS 100 g sand 50 g clay 100 g water 40 g gum arabic 6 g cellullose 5 g chitosan 10 g agar

DITIGAL TO PHYSICAL. PARAMETERS

slicing distance: 1.3 mm nozzle diameter: 2.0 mm pressure: 0.1 - 1 bar Offset height: 0.5 mm print speed: 4500 total print length: 103550 mm total print volume: 0.3 liters total print time: 29 minutes

slicing distance: 1.5 mm nozzle diameter: 3.0 mm pressure: 0.1 - 1 bar Offset height: 1 mm print speed: 4500 total print length: 16940 mm total print volume: 0.05 liters total print time: 10 minutes

slicing distance: 1.3 mm nozzle diameter: 3.0 mm pressure: 0.1 - 1 bar Offset height: 0.5 mm print speed: 4500 total print length:19132 mm total print volume: 0.07 liters total print time: 6 minutes

56

B.

C.

E.

F.

XERIC STRATIFICATIONS |

A.

D.

G.

H.

I.

J.

K.

L.

M.

N.

O.

57

58

59 XERIC STRATIFICATIONS |

EXTRUSION TESTS RESULTS

geometrical studies

06

06

geometrical studies

[COMPUTATIONAL STUDIES]

66

67 XERIC STRATIFICATIONS |

initial geometry studies

The initial computational studies focus on a multi – geometrical approach, intended to create a series of dual conditions that define spaces and functions through their resulting morphology. The factors investigated in the process of establishing these divergent conditions are built upon the ideas of growth entwined within the nogrowth, the inhabitable versus the uninhabitable, light versus shade, living versus inert matter.

These geometrical qualities seek to provoke design inquiries about implementing new relationships between humans, biological design systems, and the environment, whilst creating immaterial boundaries between enclosures and the exterior growth.

GEOMETRICALLY EXPLORED CONDITIONS

Level of finishing / Growth Solidification / Non – Solidification (coarse vs soft) Inner / Core / Outer Living pockets’ – how the growth is influencing the system Partly inhabitable, partly bio-receptive

68

69 XERIC STRATIFICATIONS |

GEOMETRICAL EXPLORATIONS The concept is further explored in a series of architectural elements, gradually increasing in scale, such as the Wall [1], urban Seat [2], the Column [3], and the Enclosure [4]. The studies speculate upon the possible architectural applications of the sand composite after its growth inoculation, as well as the potential interactions between the users and the biomaterial elements. The hypothesis is digitally explored through various procedural growth algorithms and parameters.

Additionally, ideas of porosity, decay, and substrates, together with impacting environmental factors such as water flow, erosion and sunlight exposure are computationally translated into the growth – embedded geometries.

70

71 XERIC STRATIFICATIONS |

CONCLUSIONS The digital models provide as well core discussion points that help start defining a fabrication protocol, as a basis to translate the digital tests into physical prototypes.

Thus, a set of factors to be taken into consideration can be extracted from the digital studies, in preparation for fabrication: 1. Multi materiality 2. Techniques of material extrusion 3. Material support 4. Structural stability 5. Chemical and physical material interaction between solidified sand and embedded growth 6. Stratified depositions 7. Horizontal growth & Scalability

72

XERIC STRATIFICATIONS | GROWTH multi - geometry shade condition sun - exposure condition

Phase 1

Phase 2

Phase 3

Phase 4

73

74

75 XERIC STRATIFICATIONS |

FURTHER DEVELOPMENT OF GEOMETRICAL STUDIES / CANTILEVERING STRUCTURES + CANOPIES In the context of arenaceous environments, the development of the established geometrical parameters will be defined by a cantilevering canopy geometrical topology, aimed to provide shade and shelter in extreme arid environments.

76

77 XERIC STRATIFICATIONS |

fabrication development

07

78

XERIC STRATIFICATIONS |

07

fabrication development

suspension 3D printing Initial fabrication explorations concluded that the weight of the sand-composite materials poses a challenge in the structural stability of the geometries while printing. Solutions are investigated accordingly to address the need of adding support to the extruded sand material.

Existing printing techniques are examined for a better understanding of what opportunities a supportbase fabrication strategy implies. Novel studies point towards Suspension 3D Printing techniques, which aim to unlock further potential of extrusion-based 3D printing (McCormack et al., 2020). As an alternative to the deposition of material layer by layer, suspension printing provides a solution for prototyping ‘nonself-supporting structures’ into a reusable gel support bath, through a free-form movement of the extruder (McCormack et al., 2020). This means added geometrical complexity, rapid printing time, and no support waste.

EXTRUSION NOZZLE

EXTRUDED MATERIAL

REUSABLE SUPPORT MEDIUM suspension tank

OPPORTUNITIES FREEFORM PRINTING no material waste (no supports needed)

PRINTING SPEED (30 mm / sec)

LARGE SCALE + LIGHTWEIGHT STRUCTURES

RIGIDITY + MATERIAL STRENGTH

79

state of the art

Evaluations of the existing projects and ongoing research set the basis for defining the main fabrication strategy. Projects are selected for a better comprehension of the methodology and the implied materials, as well as on the basis of established criteria such as: the gel matrix used, the extruded material, the solidification time, and the use of natural materials.

Suspension Printing research carried thus far commonly utilizes hydrogels as support baths. Existing projects developing this technique include: Soliquid (Jim Rhoné and Amaury Thomas), Rapid Liquid Printing (Self-Assembly Lab, MIT), Injection 3D Concrete Printing (I3DCP, Hack et al.), Buoyant Extrusion (Greyshed), and Suspended Depositions (Sci-Arc).

The suspension material can be described as a liquid material that is photo, chemically, or otherwise curable. Materials tested until now include urethane rubber, urethane foam, urethane plastic, silicones, acrylics, epoxy, concrete, plaster, liquid metals, wood slurries, etc. (Hack et al., 2020).

The overall conclusions validate the potential of the system, providing, however, only synthetic materials examples. Further analysis and experimentation is needed to test the fabrication strategy in terms of natural hydrogels, the applicability in case of the proposed sand composite material, as well as the investigation of more alternative support media and strategies.

80

XERIC STRATIFICATIONS | (Rhoné, Thomas, 2018)

SOLIQUID, 2018 JIM RHONÉ AND AMAURY THOMAS

(Self-assembly lab, MIT, Guberan, Steelcase)

RAPID LIQUID PRINTING SELF-ASSEMBLY LAB, MIT

(Hack et al., 2020)

(Johns, 2014)

(Barnshaw, 2012)

INJECTION 3D CONCRETE PRINTING (I3DCP)

BUOYANT EXTRUSION

SUSPENDED DEPOSITIONS

GREYSHED

SCI-ARC 2012

EXTRUSION MATERIAL

CONCRETE / PLASTER SUSPENSION MATERIAL

CARBOMER

RUBBER / SILICONE / FOAMS/ PLASTICS

CONCRETE

CARBOMER

CARBOMER / + SAND

URETHANE PLASTIC / RUBBER CARBOMER / + SAND

RESIN

CARBOMER / GELATINOUS MEDIUM

silicones, urethane rubbers, foams, and plastics to epoxy, UV curable resin, concrete, metal-filled epoxy

81

82

XERIC STRATIFICATIONS |

redefining suspension printing REDEFINING SUSPENSION PRINTING IN THE CONTEXT OF FABRICATING WITH SAND-BASED MATERIALS The implementation of suspension printing strategies into the proposed fabrication techniques entail the adaptation of the process to fit the developed material strategy.

The next section of the thesis thus focuses on redefining the concept of reusable support by investigating possible alternatives of the discussed fabrication system. The proposed options look at two methods: extruding a solid material into a liquid medium and extruding liquid substance (binder) into a solid medium. The support matrix hence looks at the different opportunities of using either hydrogel or sand particles as support.

The sand as support is further subcategorized into two variations: the stratified deposition of the binder and the support layer by layer (similar to a binder-jetting system), and the use preshaped sand dunes as a removable form to define the overall shape of the print. The schematic proposal for redefining suspension printing strategies is illustrated on the following page. The first three fabrication methods are experimentally tested and compared in the following section, in order to determine the final fabrication approach. Separately, each of the techniques opens up opportunities for individual research topic paths.

SUSPENSION 3D PRINTING

SOLID MEDIUM

LIQUID MEDIUM

sand as suspension medium

hydrogel as suspension medium

adhesive composite extrusion

sand composite extrusion

POLYMER-BASED HYDROGEL

83

redefining suspension printing techniques FOR FABRICATING WITH SAND

SUSPENSION PRINTING

SAND COMPOSITE

07.4A

BINDER

07.4B GEL AS SUPPORT

SAND AS SUPPORT

84

XERIC STRATIFICATIONS |

BINDER

BINDER + SAND BY LAYER

SAND COMPOSITE + BINDER

SAND DUNES AS SUPPORT

85

86

XERIC STRATIFICATIONS |

07.4.A

gel as support PRINTING IN HYDROGELS

SUSPENSION PRINTING

SAND COMPOSITE BINDER

SAND COMPOSITE + BINDER BINDER

SAND AS SUPPORT

LAYERED SUPPORT DEPOSITION

SAND DUNES AS SUPPORT

GEL AS SUPPORT

87

suspension in hyrogel baths LIQUID SUPPORT MEDIA

The initial fabrication series addresses the suspension extrusion in a hydrogel medium. The tested gels include carbomer, as well as organic hydrogels such as cellulose, alginate, and gelatine.

Having been previously researched and utilized in suspension printing prototyping, the initial experiments are set up using Carbomer Carbopol as suspension medium. The fabrication trials concentrate on formulating mixing ratios and methodologies, while evaluating the resulting density and viscosity properties, as well as the chemical reaction with the extruded sand composite.

Carbopol is a polymer frequently employed as “a thickening, suspending, dispersing, and stabilizing agent”.

Carbopol forms a colloidal dispersion when mixed in water, following very specific quantities, temperature, and pH levels (R. Varges et al., 2019). This resulting dispersion provides an efficient gel medium for supporting 3D printed extrusions (Carnali and Naser, 1992).

PREPARATION OF THE CARBOMER GEL The carbomer is mixed into water, using weight concentrations between 0.5% and 1% (w/v) carbomer-water, until fully dissolved. At this point, the mixture typically displays a pH value around 4.0 -5.0, de-pending on the alkalinity of the water and the carbomer quantity (Hack et al., 2020). At this pH level, the solution does not thicken, requiring a neutralizing agent such as sodium hydroxide or triethanola-mine 85% to bring the pH value to 7.0. Constant mixing is required during the preparation of the car-bomer gel, recommendable by using an automated blender.

The conducted experiments utilize tr-ethanolamine drops to exponentially neutralize the pH of the solution, which starts to gradually trans-form into a thick gel. pH indicators verify the condition of the gel throughout all the described steps. The outcome is a strong, transparent hydrogel, ready to be used as extrusion support. The carbomer preparation process and trials are illustrated in the figures below.

CARBOMER AS SUSPENSION GEL Initially, manual extrusions are attempted inside the prepared carbomer gel. Due to the high density of the sand composite, additional force is needed to extrude the material from a syringe. The suggested alternative considers using an open-source tool called the Biogun (designed by Markos Georgiou), consisting of a hand drill, customized with fitted 3D printed components, to eject denser paste materials (Wikifactory.com. n.d.).

The bio- extruder device is fabricated and successfully employed in extruding the sand composite into the gel. After an incubation time of 24 hours, the extruded material does not display any signs of drying, indicating that the existing composition might not be curable in the carbomer medium.

COMPOSITION & PROCESS

COMPONENTS

WATER

CARBOMER CARBOPOL

TRIETHANOLAMINE 85%

STRUCTURE

PARAMETERS viscosity density ph levels

H2O

CARBOMER HYDROGEL

PH

TEA

PH water tank

measuring ph levels of the water

adding triethanolamine to neutralize the ph

mix solution and test ph level

add carbomer powder between 0.5 - 1.0 % wv

mix carbomer powder until the gel forms

Biogun // Manual Extrusions BIOGUN Markos Georgiou Other Today Studio

requires more pressure

COMPONENTS

MATERIAL TUBE PRESSURE TUBE

NOZZLE

EXTRUSION TUBE

HAND DRILL

The sand-composite is then altered, by adding base materials which have been previously printed in the gel medium, including concrete and plaster. In the case of the modified material composition, solidification is achieved, however additional factors occur: - Water accumulates on the surface of the gel, gradually dissolving the carbomer back into a liquid mix. This indicates a significant shift in the pH levels of the gel, caused by the pH of the extruded material. The gelling process is reversed, collapsing the supported extrusion.

- The chemical reaction between the gel and the extruded material causes significant material erosion, producing a porous layer onto its surface.

- The curing process creates a white, flexible membrane around the outer surface of the extruded object.

- Due to pH imbalance, the extruded object is destabilized, causing breakage during the removal process Additional testing investigates variations of the carbomer gel weight concentrations, trials to balance the pH of the extrusion material to neutral levels, as well as reinforcing the carbomer with sand granules. The latter aids the gel-support density and reduces the accumulation of water.

CONCLUSIONS

All the tested samples conclude in the aforementioned observation, further research being required to obtain adequate results. Considering the main aim of the research and the deviations implied by the further development of the carbomer hydrogel suspension, this series of experiments is interrupted at this stage.

Subsequently, as a response to the issues created by the carbomer’s pH reactions and the established prerequisite of using natural materials, the suspension gel is replaced with bio hydrogels for the next series of experiments.

90

GEL PREPARATION

XERIC STRATIFICATIONS |

900 ml distilled water 9 g carbomer powder 6 ml triethanolamine

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92

93 XERIC STRATIFICATIONS |

OBSERVATIONS

POROUSITY

WATER ACCUMULATION

WHITE MEMBRANE

RESULTS

A.

B.

E.

C.

D.

0.5 % wv Carbomer Gel

1.0 % wv Carbomer Gel + 10 g sand

RESULTS

EXTRUSION

1.0 % wv Carbomer Gel

Beyond its properties of a support medium, the research suggests embedding a novel function into the gel, to stimulate the bioremediation of the extruded sand composite it suspends. The opportunities thus take account of the potential inclusion of growth mediums or bacterial infusions into the natural hydrogel, creating not only a supporting gel matrix bath, but also a fertilizing one.

Evident improvement is observed once the previous extrusion tests are repeated in support baths of cellulose, gelatine, and alginate. Cyanobacterial biomass in the form of spirulina is incorporated in small quantities in the suspension gels, to suggest the hypothesis of a growth embedded suspension gel. Within the organic hydrogels, the extrusion material solidifies, while the hydrogel acts as a coat mem-brane, forming a binding exterior layer around the geometry.

CONCLUSIONS

Concluding the first suggested fabrication technique, the method of gel as suspension opens multiple paths for in-depth research. In order to maintain the composition of the developed solidified sand un-altered, the second technique is introduced.

ALGINATE HYDROGEL

CELLULOSE HYDROGEL

GELATIN HYDROGEL

A PROLOGUE TO CYANOBACTERIAL GROWTH COMPONENTS

high resistance against rough conditions and invading organisms

cyanobacteria

nutrients WEEK 1

PREPARATION

WEEK 2

viscosity density ph levels

500 ml water

salts

nutrients

culture media

bacterial strain

mix

water

soil

wood

agar plates

LIQUID GROWTH MEDIUM

SOLID GROWTH MEDIUM

SAMPLES OF AQUATIC AND TERRESRIAL BACTERIA

CB.01

CB.02

CB.03

CB.04

SERIES A.

CB.01 : 20 g nutrient broth + 1 ml pond water sample CB.02 : 22 g nutrient broth + 1 ml pond water sample CB.03 : 22 g nutrient broth + 2 ml pond water sample CB.04 : 23 g nutrient broth + 0.5 ml pond water sample

CB.05

CB.01

SERIES B.

CB.02

CB.03

CB.04

CB.05

20 g nutrient broth + pond micro organisms

SOIL BIOSTIMULANT

COMPONENTS

spirulina

carbomer hydrogel

spirulina hydrogel

SUSPENSION HYDROGEL

REPLICATING CYANOBACTERIAL CRUSTS

sodium alginate

cellulose

spirulina hydrogel

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07.4.B

sand as support ROBOTIC ‘BINDER JETTING’

SUSPENSION PRINTING

BINDER SAND COMPOSITE

SAND COMPOSITE + BINDER BINDER

LAYERED SUPPORT DEPOSITION

GEL AS SUPPORT

SAND DUNES AS SUPPORT

SAND AS SUPPORT

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suspention printing in sand support SUPPORT AS SOLID MEDIA

The second described technique inverts the suspension method, considering the extrusion of liquid binders into supporting containers of sand. Throughout this phase, multiple prototype scales are investigated, ranging from manual extrusion to the use of a 3D printer, and finally to the scale of the robotic arm.

MANUAL EXTRUSIONS The methodology follows the steps established in the previous technique. Initially, binders are manually extruded with a syringe into a sand container. At this stage, wood glue is used as binder, for a rapid verification of the system. Solidification is achieved after a drying time of one week. The low level of control while manually extruding and the limited diameter of the syringe cause the geometry to break.

Furthermore, the trial demonstrates the need for a more systematic removal of the printed pieces, as the fixed bounding sand container restricts the procedure and affects the stability of the print.

3D PRINTED EXTRUSIONS AND TOOLS SETUP To grant a regulated movement of the extrusion path and better accuracy, the system is translated onto the Ender 3D printer. The required tool modifications include the design of tall extrusion nozzles, to prevent the collision of the extruder with the support tank, allowing a free movement.

Later, the level of the extruder is adjusted, and the sand tank is fixed onto the printing bed. For this procedure, the tested extruded binders are wood glue and a gum Arabic composite. Throughout the printing process, several observations are made: - The consistency of the extruded binder is too liquid for the motor – screw system of the printer.

In this case, a pressure-based extrusion system is recommended instead.

- The extrusion pressure is difficult to adjust, as there is no visibility over the ongoing process - The extrusion nozzle can be easily obstructed by the formation of solidified clumps of sand and binder - The restricted scale of the printer outputs objects that are particularly thin and fragile, not en-during the removal process ROBOTIC ARM EXTRUSIONS Lastly, the technique is set up on the ABB robotic arm, providing larger prototyping options and a pressure-based extrusion system. Similar to the

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3D printer, the nozzle is extended with a fitted 3D printed extension, to reach the depth of the sand container.

An improved removal system is tested, by suggesting extracting the sand from the container rather than the geometry, either through vacuuming or detaching the base / walls of the container. A modified tank design is fabricated, implementing a movable base for the release of the supporting sand without affecting the printed object. Although solid, the resulting prints did not maintain the intended geometry.

CONCLUSIONS

ENDER printer setup // glue extrusion in sand

XERIC STRATIFICATIONS |

Final observations upon the second suggested technique of suspension printing using sand consist of: little control over the pressure parameters, no visibility of the extruded geometry throughout the pro-cess, long residence and drying time, and inability to detect errors prior to removal. Moreover, the proposed material’s characteristics are not completely compatible with this fabrication method, as the mixture gets displaced within the sand tank. Conclusions confirm a better performance of the technique in the case of instant curing adhesives or epoxies rather than the natural materials investigated in this paper.

robotic setup

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final fabrication strategy

08

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08

final fabrication strategy + prototyping ROBOTIC ‘BINDER JETTING’

support stratification

SUSPENSION PRINTING

SAND COMPOSITE

GEL AS SUPPORT

BINDER

BINDER

SAND COMPOSITE + BINDER

SAND DUNES AS SUPPORT

SAND AS SUPPORT

LAYERED SUPPORT DEPOSITION STRATIFIED EXTRUSION + SUPPORT DEPOSITION

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robotic stratification of sand support PROPOSAL FOR THE FINAL FABRICATION STRATEGY

The final fabrication strategy is based on a layered support deposition, concomitant with the extrusion of the sand-composite. The parameters and fabrication methods come as a response to the previously tested strategies and the opportunities for their improvement. Briefly, the presented robotic fabrication technique is based on a pick & print algorithm, and alternates between depositing an extrudable paste and a supporting sand directly from the cartridge. The advantage of the direct use of the cartridges as extruders simplifies the system and provides a pressure-based extrusion mechanism, eliminating the risk of sand particles blocking the extruder channel. The manner in which the sand is deposited is optimized for supporting the geometry is delimitates, following accurately its form.

ROBOTIC SETUP + TOOLS To validate the hypothesis, various manual tests are initially conducted, by dispensing dry sand around the extruded sand composite. The outcomes display favourable potential for the use of sand as a reusable support, as it provides a layered bed for the supporting the weight of the sand paste, as well as for the larger cantilevering angles of the tested geometries. For more precision, the next steps in verifying the system include automatizing the process, by designing a customized setup with the necessary tools for the fabrication technique to be tested on a robotic arm.

The setup is designed for the implementation onto two ABB six-axis robot arms, respectively the IRB 120 and the IRB 140, which are then used for conducting the prototyping experiment.

The system is designed to alternate between extruding the sand composite and dispensing dry sand, layer by layer – building up the vertical stratification for the printed geometry and its support, simultaneously.

This allows for high levels of control and facilitates visibility over the evolution of the process throughout the entire operation. Unlike the previously tested fabrication technique (Suspension printing in sand [2]), this allows for progress supervision, early error detection and any necessary while-printing calibrations.

The setup consists of two main material cartridges: one for the sand composite, and the other one filled with dry sand for support. Both cartridges are placed on a CNC-milled base, designed to be mounted onto the robotic arm table and flexibly positioned according to the reach angles of the robot. The process then involves programming the robotic arm to alternate between picking one cartridge at a time, extruding the containing material, placing it back onto its base, and picking the other cartridge. Based on an original robotic pick & place algorithm, this system adapts the original code to a pick & print one, adjusting the extrusion system individually for each of the cartridges.

The new established pick & print strategy uses a pneumatic gripper with a dual action piston system attached to the flange of the robotic arm. The gripper tool - designed for tight clasp of the cartridges - is modified with an added 3D printed part, lined with threaded rubber for better cartridge adhesion, and mounted on the ABB flange.

Once all the tools are mounted in place, they are connected through pneumatic tubes to four individual solenoids, attached to the main air compressor system as it follows:

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XERIC STRATIFICATIONS | GRIPPER TOOL

ROBOTIC SETUP

CARTRIDGE TOOL

The gripper tool, equipped with two outlets, requires ±60 psi / 4 bars in each piston alternately. The digital outputs they connect to open each of the first two valves one at a time, to allow the gripper to open, close once it has picked the cartridge, and then open again when placing the cartridge back once it has printed.

The sand composite cartridge, composed of an extruder body, a nozzle, an interior airtight silicone piston and a threaded cap connects to the third solenoid valve and requires ± 7 psi / 0.5 bars, depending on the consistency of the material. The air pressure then pushes the piston down, extruding the sand paste at a speed between 20 – 25 %.

The dry sand cartridge uses the base container as the paste one, being however modified to enable the sand deposition only through gravity. To achieve that, the nozzle is attached to a small pneumatic piston, through a 3D printed connection piece. At the other end, this piece is lined with an elastic latex membrane, which, when pushed by the pneumatic piston, blocks the end of the nozzle, and prevents the dry sand from escaping the cartridge. On the lateral side, the new nozzle part is fixed to the last solenoid through a silicone tube, carrying ±55 psi to the piston.

Schematically, since the gripper tool and the dry sand cartridge require similar quantities of air pressure to

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D0_9 D0_11

GRIPPER TOOL

D0_2

D0_10

EXTRUDING MATERIAL SUPPORT MATERIAL

PRINTING BASE

operate, their solenoids are grouped together to the same pressure terminal regulator, adjusted accordingly at around 4 bars. The remaining solenoid corresponding to the sand composite paste is then individually connected to the second terminal, calibrated below 1 bar, dependent on the determined speed of the robotic printing.

The process is completed by calibrating the setup, measuring the TCP (tool centre point) and the extents of both the tools and the printing base board. The parameters are translated into Grasshopper for processing the test geometries, coding the tool path, interpolating the data for controlling the order of the operations, and regulating the switch of the defined digital outputs.

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sand path deposition development

1.

angle of depose

2.

1 LAYER OF SUPPORT - SCALE

MULTIPLE OFFSET PATH

The initial test used one layer of sand as a scaled offset of the geometry.

Integrating multiple interpolated paths to provide further support.

3.

XERIC STRATIFICATIONS |

geometry unsupported by sand

4.

MULTIPLE OFFSET PATH + BOUNDARY

LINEAR PATH + BOUNDARY

Adding a boundary to contain the support sand in place and allign the extrusion and the sand deposition.

The sand can also be deposited as a linear path, which fills the negative space between the printed geometry and the boundary.

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FURTHER APPLICATIONS OF THE STRATEGY

SAND SUPPORT

C1

C2

C3

C4

C5

C6

Looking at the dual materiality of the prototyping - the sand composite and the sand support, the setup allows for a multiplication of the cartridges, creating an array of materials palletes to print with.

The setup allows for mobility and easy access and interchange of materials and refilling.

MATERIAL PALETTE (options)

Extrusion Material Reusable support Growth medium Neri Oxman, MIT

EVALUATION OF THE SYSTEM AND FUTURE OPPORTUNITIES FOR DEVELOPMENT Fixed cartridges normally require pausing the process when access to the cartridges is needed and leave little space or modifications. Consequently, the alternative proposed setup aims at further increasing the operator’s mobility throughout the printing process, as well as easing the access to interchange and refill the materials, while operating the robotic arm.

Further possible applications of the proposed fabrication strategy could also include expanding upon the idea of dual materiality (extrusion and support), the setup allowing the unrestricted multiplication of the cartridges with minimal disruptions or changes to the system. Explorations of the next steps in developing the strategy display thus the potential of creating an array of material cartridges to print with, creating a flexible material palette. In the case of the sand support experiments, the two existing materials could be augmented with the addition of other cartridges containing cyanobacterial hydrogels to inject growth, additional binder layers, or even multiple dust-based materials (such as salt, marble dust, saw dust, etc.) for varying the support in different parts of the printed structure.

The resulting multi materiality and the creation of dual conditions responds, in this manner, to one of the ways in which the digital geometry studies discussed in the previoous chapters could begin to materialize.

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G

EOME

TRY

DIFFE REN TIA L

G TH W RO

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geometrical system FOR CANTILEVERING STRUCTURES

PROTOTYPING SUPPORTED CANTILEVERS GROWTH PATTERNS & CAVITIES The extruded geometries opened up research questions about the complexity of the geometries that could be achieved once support is added.

CA

The development of the final geometry follows the evolution of one element within numerous parameters such as growth rate, point separation, and growth point origin. The resulting catalogue is then expanded into a multi-element typology, with several starting points creating a system of columns merging into one canopy. The last phase of the computation development implements collision parameters, constraining the growth into given areas. Subsequent to determining the design characteristics of the geometry, the outcomes are analysed by their curvature levels. The post – processing involves passing the geometries through an algorithm which calculates the cantilevering angle of each mesh. This provides the basis of a methodological system of assessing the limits of the cantilevering angles that can be achieved with the support of sand.

DIGITAL GROWTH STUDIES The computational studies looked at implementing the algorithm both verically and horizontally.

V LE TI N

S ER

N

Subsequently, the growth algorithm creates micro pockets within the geometries, additionally promoting the retention of nutrients for growth. On a structural level, the algorithm provides increased surface area for layer adhesion, aiding the support of the canopy. The computational studies look at implementing the growth algorithm both horizontally and vertically – progressively creating the cantilever.

ITHM LGOR

GROW TH I

The typology of a cantilevering column is thus formulated, by generating vertically displaced layers through algorithms of differential growth. The resulting forms follow a determined protocol for the gradual creation of cantilevering layers to be tested for support. This is attained by procedurally generating geometries that allow a constant stratification of layers in the Z axis, while displacing the growth path in the X and Y axis incrementally.

HA WT O R

DIFFE REN TIA L

G

Further reflections upon the initial extrusion tests examined in the 'Geometrical Studies' section rearticulate the concept of geometrical growth as a morphological language, in the context of the established fabrication strategy of layered support. The capabilities of the described system open up research questions about the geometrical complexities that can be achieved once support is added.

GRADUAL GROWTH FORMING CANTILEVERS As a starting point for verifying the research interest, a cantilevering column was designed and analyzed.

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robotic setup calibration INITIAL TEST OF THE SYSTEM The prototyping phase consists of a number of series, following an experimental approach for improving the fabrication technique as well as optimizing the geometry. The factors taken into consideration for this phase focus on: - the angle of sand deposition in relation to the printed object - the maximum displacement distance between two consecutive printed layers - the path of the sand deposition - the constraint of the support sand within a given boundary A set of experimental series is conducted, aimed at an experimental hands-on methodology for refining the system and discovering its functioning criteria, optimizing the process, discovering its limitations and its opportunities, as well as comparing the results towards the set hypothesis.

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prototype_series A

Series A serves as an initial trial for calibrating the parameters and observing the behaviour of the supported extruded geometry. For this experiment, a cantilevering column with maximum overhangs of 65 ° is utilized. Its total height reaches 120 mm and the maximum horizontal displacement between the top layers ranges around 10 mm.

The prototyping process begins with the deposition of the initial layers of sand-composite material and their corresponding sand support contours. This technique of 1:1 ratio of printed layer to support contour displays its drawbacks after the first printed layers. Due to the angle of sand repose and the density difference between extrusion and support, the height of the sand support remains at a lower height level than the printed geometry. After the 8th printed layer, the first cantilevering layer remains unsupported and bends under gravity until it reaches the lower level of the support. Throughout half of its total height, the cantilever continues to bend, however the print does not collapse, as its layers are supported by the sand bed accumulating below the print level. The resulting prototype displays a height difference of almost half for the sand support in relation to the final layer of the print.

After a residence time of one week to allow complete drying, the printed geometry is removed, by extracting the sand with a vacuum system for reuse in the following prototypes.

The primary observations and further improvements extracted from the first series of prototyping are primarily related to the sand deposition technique and its deposed behaviour. The increase in the contours of sand support per each layer, as well as the implementation of a bounding container serve as prospective opportunities for equalizing the level height of the print and its support. Furthermore, the option of reducing the horizontal displacement between layers is considered, by proposing the shift of the main cantilever onto one longitudinal axis, to aid the structural stability.

To extract the support, minimal disruption of the printed object is required. One of the advantages of using sand as support is the simple process of its removal. A vacuum system is used to extract the sand around the print, revealing the dried, self – supporting resulting cantilever. The extracted sand is easily recovered for further reuse. The structural output of the initial prototype is a bent canopy, the cantilevering being warped due to the sand not being deposited at the same height of the composite.

On a detail level of the material interaction, the support material adheres to the print, acting as a coat layer and forming complex micro layers and surface textures.

CANTILEVER ANGLE

63 °

failure point without supports

0°

65 °

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FROM DIGITAL TO PHYSICAL XERIC STRATIFICATIONS |

PRINTING PROCESS The robotic fabrication process, based on a pick & print algoritthm, alternates between the extrudable paste and the supporting sand cartridges

LAYER 1 - 1 x clay - sand composite + 1 x sand support contour

LAYER 4 - height of the sand support is lower than the printed geometry

LAYER 8 - the first layer of cantilever is unsupported and bends under gravity

LAYER 12 - cantilever is bent, however still not failing

LAYER 15 - cantilevering layers are supported at a lower height by the sand

LAYER 17 - the sand height is almost half the height of the printed geometry

OBSERVATIONS AND FURTHER IMPROVEMENTS

ANGLE OF SAND DEPOSITION

SAND HEIGHT

BOUNDARY

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prototype_series A RESULTS

BEFORE SUPPORT REMOVAL

3D PRINTED STRUCTURE OUTPUT

After a residence time of 1 week, the printed geometry is removed, by extracting the sand with a vaccuum system for further use.

Due to the sand not being deposited at the cantilever starts bucking down, creating a be

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e same height of the composite, the ent canopy.

XERIC STRATIFICATIONS |

CANTILEVER BENDING DETAIL The support material and the extruded one start interracting, forming complex micro layers and textures.

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prototype_series B

Series B emerges from the observations for improvement identified in the previous series. The adjusted tested geometry is built upon the idea of a linear cantilever direction, reducing the displacement distance between consecutive layers. This second experiment increases the initial height to 140 mm and decreases the maximum overhangs to 45 °. Moreover, it addresses the issues of sand deposition technique, adjusting the ratio to 1:8 ratio of printed layer to support contour. This readjustment assists in the increase of support volume, bringing the height of the sand support to significantly over 1/3 of the final print height. Due to the geometrical modifications of the geometry, minimal bending occurs at the extremities of the longitudinal cantilever.

The review of the second prototype trial reconfirms the conclusions of the initial one, adding further suppositions upon the process of support deposition. Four schematics are hence derived, exploring the options of the procedure. The initial once coincides with Series A of the prototypes, consisting of a single layer of sand support, following the path of a scaled offset of the printed geometry.

The requirement of its improvement draws the second option, integrating multiple interpolated paths to provide additional support. The next step necessitates the incorporation of a bounding box to contain the support sand in place and align the extrusion and the sand deposition, tackling the issue of the sand displacement still existent in the second option. Lastly, the optimized suspension deposition of the support takes into consideration alternative paths for the sand dispersion, proposing a linear path, which fills the negative space between the printed geometry and the boundary.

TOP VIEW

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ROBOTIC FABRICATION SETUP

CANTILEVER ANGLE

45 °

0°

45 °

Printing Speed: 10-20 % Pressure: 2 bars // 4 bars for gripper

PARAMETERS:

Layer Height: 3.8 mm Total height: 140 mm

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prototype_series B PRINTING PROCESS

RESULTS

BEFORE SUPPORT REMOVAL

3D PRINTED STRUCTURE OUTPUT

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TOP VIEW TEXTURE DETAIL

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SUPPORT REMOVAL

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prototype_series C

The geometries explored in this series intend to augment the geometrical complexity of the experiment, by adding a double curvature - cantilevering displacement both at the top and the base, for a comprehensive implementation of the system’s capabilities. The outputs are therefore morphologies that could not be otherwise printed without supports.

Bringing together the conclusions of all previous tests, Series C implements the deposition of sand following the strategy of multiple interpolated sand paths, contained within a boundary. To avoid extruder collision, the container is also gradually built-in layers, as opposed to being mounted at its full height in the beginning. The height is additionally increased to 200 mm for the printed object, while the tested geometry addresses both the organic displacement of layers (C1) and the linear cantilever typology (experiment C2).

The modifications of the sand path as well as the introduction of the support container successfully result in the canopies being fully supported. In the case of experiment C1, despite the large distance displacement of almost 30 mm of unsupported layers, the structure does not collapse. Its stability, however, is detrimentally lowered by its own weight. Those combined factors, together with the investigation of a shorter drying time of 48 hours, eventually result in the print – being still wet – fissuring on the middle axis, both in vertical and horizontal directions.

Nevertheless, experiment C2, following a stable linear cantilever and being allowed appropriate drying time of a week, proved successful, effectively supporting the cantilever both during the printing process and after the support removals. The results of the C2 series are ilustrated in the final prototype section.

Following the protocol set by the prototype series, several other trials were conducted, testing variables in the established parameters. Subsequent to this prototyping phase, the final cantilevering morphology was defined in conjunction with the optimized prototyping parameters.

TOP VIEW

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ROBOTIC FABRICATION SETUP

CANTILEVER ANGLE

75 °

0°

80 °

Printing Speed: 10-20 % Pressure: 2 bars // 4 bars for gripper

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prototype_series C1 PRINTING PROCESS

CROSS SECTION - MIDDLE OF THE COLUMN

BASE OF THE GEOMETRY

RESULTS

BEFORE SUPPORT REMOVAL

3D PRINTED STRUCTURE OUTPUT

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XERIC STRATIFICATIONS | GEOMETRY BEING SUPPORTED WITHIN THE BOUNDARY

TOP LAYERS OF THE CANOPY

TOP VIEW TEXTURE DETAIL

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PROTOTYPE 2

PROTOTYPE 3

PERSPECITIVE

ELEVATION

TOP VIEW

PROTOTYPE 1

CONCLUSIONS The concluding outcomes identify the optimal factors as: applying multiple sand contours per layer as support, utilizing a containing boundary for the support sand, and implementing cantilever directionality for better stability.

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PROTOTYPE 5

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PROTOTYPE 4

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architectural application

09

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09

architectural application

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calima desertification in canary islands

Fig. 20. Calima (Martin, 2020)

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context + site

Subsequent to defining the design morphology and validating its fabrication methodology through experimental robotic prototyping, the following phase for determining its specific architectural application entails the re-evaluation of the context within which the project is outlined.

Within the framework of desertification, the location of the Canary Islands is selected as a potential site to demonstrate the application of the developed system. Due to its geographical location, the islands display a “territory where ecosystems and agriculture” (Quintana et al., 2015) are extremely frail and prone to being directly affected by the desertification factors. Amongst numerous environmental triggers, the islands are also exposed to a particular phenomenon that aggravates the effects of desertification. This occurrence is called Calima.

Calima is a meteorological phenomenon consisting of the presence in the atmosphere of very small particles of dust and sand in suspension, affecting the Canary Islands. This climatic event is caused by the proximity of the Islands to the Sahara Desert and the direction of the wind, which carries with it the sand particles responsible for the frequent sandstorms. The primary soil topology on the islands is thus characterized by arid, deserted land and volcanic ash.

The selected setting displays the extreme environments and soil fertility issues that the project aims to address, becoming a relevant testing ground.

Studies indicate that around 82% of the archipelago is characterized by sandy soil types and currently at high risks of further desertification. Moreover, Lanzarote is amongst the islands considered to have 100% of its area “within the arid region” (Quintana et al., 2015). Lanzarote’s overall landscape is further characterized by a particular type of black, volcanic soil, otherwise known as a “picón” layer covering the topsoil.

These soil levels originate in the 18th-19th centuries, caused by the volcanic activity and eruptions at the time.

Within this soil typology of dust, ash and sand, numerous Vineyard Farms have been established in the southern-central area of the Lanzarote Island, occupying almost 2,000 hectares of the land. The morphology of the farms is characterized by dark semi-circular walls, built around shallow pockets in the soil, creating the effect of numerous craters in the landscape.

The vine pits measure around 4-5 meters in diameter, 2-3 meters in depth, and are strategically protected from the intense winds by their surrounding stone barriers, measuring around half a meter in height. The farming technique developed to adapt to this specific soil condition involves digging through the layer of ash to reach the lower and more fertile levels of the soil – hence the necessity for the crater-like landscapes (D.O. Lanzarote. n.d.).

Biologically, the volcanic ash exhibits favourable properties for promoting growth. It provides additional nutriments for the plant and has the capacity to absorb and store moisture. This attribute is particularly advantageous in the context of soil aridity and scarcity of precipitation. Moreover, the ash provides a protective coat for the lower substrates of the soil – where the vines are planted - reducing the erosion rates (Lanzarote Information. n.d.).

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Therefore, the chosen site returns to the initial idea of the research, contextualizing the proposed material development and fabrication strategy. A new type of dust – based material is introduced, adding an extra layer of materiality and of viable micro-organism interaction.

The site conditions further amplify the opportunities discussed both in the geometrical studies and the fabrication chapters, in terms of defining a new material condition or an additional support material. Reflecting back onto the material palette hypothesis, the volcanic ash can be introduced in the fabrication process and disposed similarly to the sand support, in order to create areas of increased nutriments, moisture and porosity.

Within the context of high aridity and intense sunlight, the geometrical morphologies of cantilevering structures are considered as the base for proposing an architectural application. Encompassing the previously explored material qualities and integrating the local infertile soils into the composition, the prototypes can become the base model for larger scale shading devices for the inhabitants, farmers, or visitors of the area.

CALIMA

Fig. 21. Dust Storm Approaching Canary Islands(NASA, 2020)

Fig. 22. Areal view of Lanzarote Desert (Stock Image, n.d)

Fig. 23. (Smith/®ICEX, 2017)

SOIL IN THE CANARY ISLANDS The primary soil topology on the islands is thus characterized by arid, deserted land and volcanic ash.

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site location

LANZAROTE VINEYARDS (La Geria)

CONCEPTUAL DEVELOPMENT Programmatically, the proposal looks at creating a new canopy structure on the vineyards land. The design intention, however, goes beyond building shaded spaces for its users and rather focuses on the possible emergence of micro-ecosystems onto the geometry.

The complex morphologies achieved through reusable support fabrication methods have the capacity to generate intricate cavities and porosity levels within the structure. This allows different species and microbes to inhabit and grow on it, thus reinstating a symbiotic relationship with its natural environment.

Built from the developed sand – based composite, the project speculates upon the larger scale possibilities of the system. Composed of sand, volcanic ash, natural binders, organic matter and cyanobacterial growth mediums, the project aims to become a ‘xeric seed’ for remediating the surrounding desertified areas.

SITE CONDITIONS

Fig. 24. Areal View of Lanzarote Volcanic Ash Vineyards (Google Maps image)

Fig. 25. (Smith/®ICEX, 2017)

Fig. 26. (Steinmetz, 2019)

LANZAROTE VINEYARDS

Fig. 27. (Smith/®ICEX, 2017) 148

SITE CONDITIONS

3-4m

Volcanic Ash XERIC STRATIFICATIONS |

Fertile Soil Layer Wind Direction Sun Exposure

SITE TOPOLOGY

WIND DIRECTION

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Fig. 28. Lanzarote Vineyards (2020)

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design methodology The design workflow involves computationally modelling the site and performing analysis through various environmental simulations, including erosion, water flow, wind direction and sun exposure. The results are then used to indicate the project’s optimal position following the criteria: - Location within the lowest topography avoids casting disruptive shadows on the vineyards, accumulates larger quantities of runoff water, and preserves higher levels of moisture.

- Orientation along the prevailing wind direction creates a protective barrier for the vineyard plantation, reducing the soil erosion in the area.

- Geometrical reconfiguration of the layout that creates maximum usable space and minimum ground-cast shadows, to allow sufficient sunlight for the surrounding plants - Position of the structural columns within the vineyard craters’ layout, to provide surface area of vertical growth of the existing plants and make use of the already existing ecosystem to re-fertilize the area.

Following the aforementioned parameters, schematic diagrams are drawn to investigate circulation strategies, connectivity to the site, cantilever linearity, as well as the relationships between the inner and outer spaces. The outlines of the sketches are then implemented into an optimization algorithm that selects the position based on the lowest height and the highest visibility field and that alters the overall shape to minimize the casted shadow amount. After 50 generations of optimization, a catalogue is created, and the best overall iteration is selected as the final plan layout of the proposal.

The layout is later populated with interlinked cantilevering columns, iterated from one to multiple elements, digitally constrained within the given plan (similarly to the geometrical explorations of the prototyping phase).

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XERIC STRATIFICATIONS | CONNECTION TO SITE

CIRCULATION

WIND DIRECTIONALLITY

CREATING INNER SPACES

LINEARITY

ORGANIC LINEARITY

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LOCATION OPTIMIZATION

Parameters:

Height Visibility Field

SUNLIGHT EXPOSURE OPTIMIZATION

Parameters: Height Visibility Field

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XERIC STRATIFICATIONS | INTEGRATING THE STRUCTURES

MULTIPLE ELEMENTS

1 ELEMENT

GROWTH BOUNDARY

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SHADE + GROWTH CONDITIONS GROWTH + STRUCTURE The concept of the proposal goes beyond creating shading spaces for humans, allowing for the emergance of micro ecosystems and spaces for species and microbes to inhabit and grow on.

ORGANIC MATTER

SOIL CYANOBACTERIA

GROWTH INTERACTION

CYANOBACTERIAL GROWTH CANOPY INFERTILE SOIL

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STRUCTURE INHABITING THE LANDSCAPE

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final design FINAL PROPOSAL AND FUTURE OPPORTUNITIES

The structure emerges from the landscape, creating a vertical stratification of architectural elements. The stepped base inhabits the landscape and organically permeates the interior spaces, providing seating for its users. The central portions of the columns support the cantilevers, while also providing vertical surfaces for the vines to attach on and expand.

Lastly, the canopy delimitates the interior spaces, offering shelter from the extreme environmental conditions. Through digital explorations, speculations are drawn upon the development of future cyanobacterial growth within the structure, envisioning the gradual transformation of the proposal. The models explore the manifestation of the final phase of the project, in which the build canopies develop an inherent micro ecosystem. To drive the hypothesis further, the project’s next steps would look at how the multiplication of the cantilevering sand structures could create a network of xeric remediation agents.

The design also addresses the growth interaction cycle that it creates through its multi-material composition and layering. In section, the soil existing on the site interacts with the material of the structure, creating a loop of organic matter exchange. The cyanobacteria present in the base soil gets transferred onto the surface of the printed structure, while the organic matter contained in the sand composite impacts the original condition of the soil fertility.

SCALABILITY AND CONSTRUCTION Although the proposed design applies quite directly the strategies of the scaled prototypes, further research is needed to verify the scalability of the structure. Ratios, proportions, layer heights, and overhangs’ angles require subsequent explorations and adjustments for a 1:1 prototype.

The next phases include translating the same process completed on the ABB robotic arm onto a KUKA robot, to exponentially increase the scale of the module and the volume of the support. Finally, a full-scale type of 3D printer such as the Crane-WASP could be employed to fabricate the proposal to its real scale.

In the case of the proposed design, the fabrication premise is built upon an on-site construction strategy, using a crane- type 3D printer. The advantages of this approach include the on-site availability of the raw materials for both the sand-composite and the reusable support. The abundant sand and volcanic ash present in the selected location would thus be directly deposited as support and returned on the ground once removed. Moreover, the issue of module transportation or off-site assembly would be eliminated.

Considerations upon the removal strategy of the sand support draw up several options. The first one includes an automated gradual removal of sand, to expose the structure and enhance the drying process. The later considers the application of a more natural removal process, investigating the alternative of allowing a longer residence time of the structure inside the support. This can facilitate the matter interchange between the supporting sand and the sand bio composite material, while the support can be left to be progressively removed by the wind, eventually exposing the entire structure.

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SOUTHERN ELEVATION

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09

final prototype SECTIONAL MODEL ON SITE

To complete the design phase, a 1:20 physical model of the proposal is robotically fabricated using the established strategy.

The final prototype (70 cm x 30 cm) looks at a section of the layered canopies inhabiting the landscape. The linearity of the geometry is derived from the conclusions of the prototyping series and aims at providing better stability for the cantilevers.

The prototype challenges the scale of the early tests, increasing the size of the elements to 200 mm height and over 450 mm length of the canopies.

The section of the landscape the canopies sit within is fabricated using the cnc mill, revealing the circular vine craters.

The three canopies inhabiting this section are individually 3D printed using the robotic setup, using sand as support. During a residence time of one week, the sand support is gradually removed in layers, to allow constant drying of the prints. The structures are then placed in position on the landscape base, creating a scaled fragment of the linear cantilevers of the design.

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FINAL PROTOTYPE The final prototype (70 cm x 30 cm) looks at a section of the layered canopies inhabiting the landscape. The linearity of the geometry is derived from the conclusions of the prototype series,

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XERIC CANOPIES INHABITING THE LAND

conclusions

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XERIC STRATIFICATIONS |

10

conclusions

CONCLUSIONS / FURTHER STEPS We are currently facing a significant soil crisis. Research estimates the growing degradation rates to cause the depletion of over 24 billion tons of fertile soil and the loss of 12 million hectares to desertification (UNCCD, 2019). Besides depleting the soil from fundamental microorganisms that fertilise it, the desertification process further leads to a greater environmental impact: eliminating the soil’s capacity to biosequester CO2.

In the search of fertile lands, the soil now turned to dust becomes a neglected resource.

The presented research builds upon the idea of ‘material discrimination’ and proposes to shift the current unsustainable construction materials and techniques towards this abundant resource without a current value - dirt.

By remediating it and re-evaluating its properties, infertile soil can open up new research paths for its integration within the bioesign field.

The thesis thus aims to contribute to the topic of biomaterial integration in architecture, by investigating opportunities for developing regenerated infertile soils such as sand into building materials. Using bioadhesive producing species as a model, the paper proposes a series of material tests that result in the development of a sand-based composite material that is durable, embedded with organic matter, and robotically extrudable.

Morphologically, the need for creating shading conditions within the described xeric regions is addressed. By exploring cantilevering structures, the research challenges the material’s applicability within advanced fabrication techniques.

The proposed prototyping strategy explores a secondary use of sand as a reusable support material, enabling the creation of geometrically complex prototypes and cantilevering structures. The project presents a fabrication system based on a pick and print algorithm, where the sand composite and support sand are robotically deposited to create canopy-like structures.

The ideas and experiments presented in this paper seek to open up additional research within the field.

Further steps and aspects for development include: the continuous improvement of sand solidification techniques and mixes, the inoculation of the material with living matter to validate the hypothesis, as well as the adaptation of the fabrication strategy for larger scale applications.

Finally, the project is set to be read as a blueprint for sand-based material applications (or any similar infertile soils) within architectural, biomaterial and fabrication studies.

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author: Stefana Zapuc supervisor: Marcos Cruz Kunaljit Chadha Institute of Advanced Architecture of Catalonia

Master in Advanced Architecture II (maa02)