Max Blythe Dissertation

WEATHERING EARTH

A data-led study into the effect weathering has on rammed earth erosion in a UK setting and how it can be used in the effort towards net-zero emmissions.

Max Blythe Newcastle University Architecture Dissertation Project

Architecture K100 - Newcastle University Dissertation Project submitted towards Architecture BA Honours Degree, Newcastle University Tutor: Carlos Calderon | dE8 Copyright © Max Blythe Word Count: 5,678 Max Blythe | 180297731 | Newcastle University

Acknowledgements

I would like to thank my family for their love and support throughout my studies. Particularly that of my parents who provide alot for me to be able to study at the Newcastle University.

I would also like to thank my friends, who consistently push me and help me through the most stressful times of my degree.

Finally, I would like to thank my dissertation tutor, Carlos Calderon. His guidance and expertise helped me approach this project with the right mindset, while his interest and enthusiasm also encouraged my enjoyment in the project. It has been great working with you.

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Fig. 1 - Un-stabilised Rammed Earth Block

CONTENTS CHAPTER 1: 1.1

Glossary & Nomenclature

6

1.2

Abstract

7

1.3

Rammed Earth: An introduction

9

CHAPTER 2: 2.1

Net Zero: Rammed Earth as a Solution

10 - 12

2.2

Existing Literature on Rammed Earth

14 - 17

CHAPTER 3: 3.1

Experimentation

18 - 29

3.2

Results

30 - 33

3.3

Discussion

34 - 40

CHAPTER 4: 4.1

Conclusion

43

4.2

COVID-19: Its Impact

44

4.3

Supplementary Data

46

5

References & Bibliography

47 - 54

6

List of Figures

55

7

Appendices

56 5

Glossary & Nomenclature Weathering: the breaking down or dissolving of rocks and minerals. [1] Freeze-thaw weathering: occurs when rocks are porous or permeable, when temperatures fall, the water freezes and expands forcing the crack to enlarge. The ice melts and water makes its way deeper into the cracks, causing more damage.

Erosion: the geological process in which earthen materials are worn away and transported by natural forces such as wind or water. [2] Precipitation: rain, snow, sleet, or hail that falls to or condenses on the ground. [3] Photogrammetry: the science and technology of obtaining reliable information about physical objects and the environment through the process of recording, measuring and interpreting photographic images and patterns of electromagnetic radiant imagery and other phenomena.

[4] Formwork: The mould which the rammed earth is build into.

Sub-Soil: The area of soil beneath the topsoil layer. Like Topsoil, it is made up of clay, sand, silt and gravel, but with a lower organic matter content.

GHG - Greenhouse Gas CO₂ - Carbon Dioxide RE - Rammed Earth HL - Hydrated Lime

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Abstract:

Rammed Earth (RE) is a material with an immensly rich history, with use dating back thousands of years all over the world. But it could also be a highly effective material in the UK for the long term need to address net zero carbon in the building industry. However, initial perceptions around durability often prevents the use of this traditional material, favouring the highly pollutant man-made materials seen in most of our 21st century architecture. This thesis aims to understand one of its main perceived limitations : its ability to withstand maritime climate conditions. Adopting a direct experiment using local sub-soil to make RE blocks, I aim to understand how much the UK weather actually impacts the condition of the material and how this may affect its use in the building industry in the future. By positioning RE outside, in the months transitioning between the Autumn and Winter seasons , it provides some key answers regarding the materials ability to withstand weathering processes ,which is one of the biggest causes for concern in the industry surrounding the material in modern architecture.

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Rammed Earth: An Introduction In recent years, RE has gained popularity among some Architects, including world renowned Peter Zumthor, as well as those aiming to address environmental sustainability issues in their construction and adhere to recent legislation towards achieving Net Zero Carbon. With RE’s direct and indirect Carbon Dioxide (CO₂) emissions being much lower than other popular construction materials, like concrete and timber, it is easy to see why the material has seen a resurgence [5]. Its strength works on an opposite process to concrete (where a chemical bond is formed using cement as a binder). With RE, the clay acts as the binder, creating an electrical bond, fixing the material together into something solid [6]. This creates a surprisingly strong material, with a density similar to that of concrete at approximately 2t/m³ and in major advocate, Rowland Keables words: “from a sustainability point of view, you can knock it down, crush it all up, add some water to it and re-build it again. And that’s something you can’t do with concrete” [7] Currently, the material is much more popular in arid climates, where less rain and frost are present throughout the year, resulting in less erosion due to weathering. Therefore, can this traditional building technique be revived in the much cooler, maritime climate of the UK?

Fig. 2 (left) - Cement Stabilised Block

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Net Zero: Rammed Earth as a Solution Climate change and Global Warming have been highly relevant topics since the first commitment by government officials during the Kyoto Climate Conference in 1997.

Between then and now there have been several other initiatives to counteract the effects of greenhouse gas (GHG) emissions. This includes the Climate Change Act (2008), and perhaps the most important one for the UK, an agreement by the UK parliament to “reduce the UK’s net emissions of greenhouse gases by 100% relative to 1990 levels by 2050” [8] . This made it legally binding for the UK to aim towards this target, and as such, action must take place to achieve this.

Noting that GHG emissions need to be reduced, we need to understand the sectors they are most prominent in. As seen in Figure 3, CO₂ is by far the most emitted GHG in the UK, Methane being the next. With CO₂ being the main GHG emitter, it should be at the forefront of emission reduction.

When looking at the sectors that produce the most CO₂ emissions, we Fig. 3: GHG emissions by gas, UK, can see that 2018 the building and construction industry is responsible for 39% of global emissions [9] . This includes the power production required to construct and allow buildings to function, which in the UK is more likely to have come from a non-renewable resource than a renewable one, therefore producing more emissions. Consequently, attention is needed when it comes to the materials used in our buildings, as this could contribute to a greater reduction in CO₂ emissions in order to achieve net zero, with a

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75% reduction in CO₂ emissions necessary to meet the 2050 target [10]. When thinking about the materials that emit the most CO₂, cement and concrete are major contributors. 9.4 million metric tons of cement were produced in 2017, releasing 7.5 million metric tons of CO₂ into the atmosphere [11]. Consequently, approximately “8% of global CO₂ emissions” [12] came from concrete production. These compounds are an issue in the aim towards net zero; an alternative needs to be found. Materials such as cross laminated timber are becoming more popular as a CO₂ reducing option. However, with trees being vital to offsetting the carbon surplus towards a net zero result, a different solution is preferred.

RE is a building material with an incredibly rich history.

With widespread use Fig. 4 - Co₂ emissions by sector in Asia and arid climates during the 18th and 19th century, evidence of the material dates as far back as 2,500 years ago, on sections of The Great Wall of China [13]. In recent decades, a resurgence of the traditional technique has taken place in the modern world. The material boasts 1/40th of the emissions when compared to concrete with a 20% cement make-up [14] , offering a sustainable alternative to concrete which may be needed in environmentally conscience building construction. RE has similar qualities in load capacity and fireproofing, as well as being a highly breathable material with great thermal massing, offering the lowest embodied energy of any masonry material [15].

EXAMPLE 1: Bushey Cemetery Looking at examples of a RE building in the UK, the award-winning Bushey cemetery in London’s green belt is a great recent example. The site of Jewish Religion makes use of the imperfections and weatherability of RE to increase the buildings relationship to the Jewish Faith.

Using the natural degradation of the material to tie in with the buildings semi-permanence, with the intention for it to “crumble” back down to earth once the cemetery is full. This is a direct metaphor for the site, with people resting into the earth once passing [16].

However, early tests produced worrying signs, the earth from the site was collapsing during the manufacturing process and weathering quickly once completed [17]. After consulting a structural engineer, they determined that some clay may be absent from the soil. A 5% addition of cement to the mix would be sufficent to make it strong enough to withstand the elements and help to bond the mix together. Hence, the final mix now comprised of “sand, limestone,

gravel, 5 per cent cement and clay spoil”[18] , with everything except the cement being available on site. Despite this more durable mix, the building was still designed to crumble away and eventually be taken down, so the question of whether RE is a suitable material for buildings with a more permanent typology still remains, in spite of this being an excellent example of the materials use.

Fig. 5 - Bushey Cemetary under construction, highlighting the Rammed Earth in the building.

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EXAMPLE 2: Mount Pleasant Ecological Park, Porthtowan While RE can be made into taller, more monumental structures like that of the cemetery, its best use is arguably in low-rise structures of 1-3 storeys [19]. As most UK buildings fit this typology [20], it is important to look at a successful example to assess how practical it is in these settings.

A great example of this is the Educational Centre at Mount Pleasant Ecological Park, a community learning facility in Porthtowan, Cornwall. It is the “largest load-bearing rammed earth structure in the UK” [21], with the decision to use the material being solely driven by its local availability. Tim Stirrup, the Architect states: “North Cornish coast is bare of trees. If this was a forest, it would have been built out of wood, because we wanted to use a material that was available locally and was very low impact” [22].

Prior to construction they had to establish if the local sub-soil was suitable for RE, conducting the necessary erosion and compaction tests.

Structurally, findings were encouraging, the earth tested had a “structural strength of 0.49N/mm² (a standard concrete block is 3.5N/ mm²). Although weaker than concrete blocks its mass…gives it its strength” [23]. A 2005 government funded study led by Peter Walker of Bath University backed this further, showing that “un-stabilised rammed earth can have a compressive strength of up to 3.5N/mm²” [24], making it just as strong as the standard use concrete blocks. Since its construction, the RE used in the Centre has been a great success, maintained annually using a lime wash [25], to help protect the un-stabilised wall from the elements. This Educational Centre is a great example of RE being utilised in its intended and most suited manor, demonstrating the overall strength of the material in a low-rise building.

Moreover, the use of lime wash highlights an alternative method to help the RE withstand the UK climate, without the use of cement.

Fig. 6 (above) - Mount Pleasant Ecological Park, with the rammed earth walls shown. Fig. 7 (next) - Weathered metal pole on site of experiment.

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Existing Literature on Rammed Earth

Research has already taken place to understand how weathering affects RE. As shown in these examples, it is one of the major barriers to overcome before widespread use of the material can commence, especially in the UK. Further research is required to produce industry building regulations, which are currently limited. Better regulations would encourage RE use throughout the UK, where the benefits towards net zero will be really felt. As previously mentioned, one major form of research was headed by Peter Walker via the University of Bath [26]. This report gives a comprehensive overview of the material, including everything from construction methods and tests to proposing regulation strategies for the material going forward. It also touches on weathering, but with limited test results he states that it’s difficult to come to an accurate conclusion about its ability to withstand rain specifically - “the performance of natural rammed earth under driving rain cannot be readily predicted in the absence of test data” [26] . While weathering of RE is what is relevant for this experiment, understanding the materials structural capacity is relevant for future use, given that there may be a correlation between this and how the material weathers. If the RE weathers easily, this is going to affect how it performs structurally over time, as the material wears away. In another report, Walker outlines that overall, many of the strength and durability factors are heavily reliant on the density of the material [27], with this being dependant on the specific soil composition used and as such “it is impossible to predict an exact value” [26] for many of these strength fields, with “no prior testing” [26] . Considering this, it is essential that the soil used for this experiment is tested, as it may not be entirely suitable for construction. Despite all of this, the report was written in 2003, so acknowledging

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that some of this information may be out of date is important and that more tests and studies have since been conducted.

More recent research comes from the Department for Civil Engineering, Lyon University in collaboration with the Indian Institute of Science, Bangalore [28]. This research has a sole focus on the weathering of RE. The experiment within the report tested the weather resistance of many variations of unstabilised and stabilised RE walls, they display and analyse the erosion data collected from

Fig. 8 - The series of Rammed Earth walls detailed in the Lyon based experiment.

these variations over a 20-year period.

This is by far the most comprehensive weathering and erosion analysis of RE that has been published. With a wide variety of grain sizes and densities used, which we know already is a vital component when talking about durability, both structurally and aesthetically.

When measuring the RE walls, they utilised a method called stereo-photogrammetry.

Using a stereoscope, they superimposed two photos of individual walls taken from different positions, allowing them to see the relief change over time. This was done in a laboratory setting, to attain accurate profiling, something which wasn’t available to me. I would need an alternative method to measure the change in relief.

Despite the thoroughness and longevity of

the experiment, this research is partially irrelevant to RE use in the UK. With climate and soil type being so important to the lifetime of RE buildings [26], an experiment of this standard must take place in the UK. This will allow us to understand how RE performs in the UK climate, as it is significantly different to that of Lyon. The weathering also took place between 1985 and 2005, which is problematic when trying to understand the potential future use of RE, given that global warming has arguably altered the climate in this time and may alter it further in the future.

Fig. 9 - One of the Rammed earth walls showing the roof canopy impliments to replicate real world use of rammed earth.

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When it comes to learning construction methods of RE, there is some literature that has been published. Although the number of sources is limited, the ones that do exist cover all there is to know about the process. The most recent of these is the “Essential rammed earth construction: the complete step-by-step guide” by Tim Krahn. This was the book most of my understanding for the process of making RE came from, alongside educational videos on “youtube.com” which largely helped me see the process visually. The essential guide is key for understanding many of the tests and details of the RE process, with the “Drop Test” and “Jar Test” being crucial for my experiment.

The “Drop Test” [29] is a test whereby a handful of soil mix is picked up and squeezed in the hand. Dropped from shoulder height onto “a clean sheet of plywood or similar smooth, hard surface” [29] . This tests the earths moisture and clay content; with its resulting ability to be rammed determined by how the ball ‘splats’ on the surface [30]. Figure 11 shows a diagram taken from the book, indicating how the earth should break up when it hits the floor. This is a process I used several times before making each block, to test the moisture content of the soil mix.

The other key test was the “Jar Test” [31] , this is essential in understanding soil composition in the absence of laboratory soil analysis

equipment. The test involves putting the raw sub-soil into a jar, filling it with water and allowing gravity to separate the sediments, with the larger particles (sand and gravel) moving to the bottom and the smaller (clay and silt) to the top. Although no accurate measurements are collected, such as grain size, the test is still incredibly useful in roughly understanding the composition of the soil, with ranges in acceptable compositions also given in the book. These ranges are stated by three important figures in RE research in the UK, Rowland and Julian Keable and the previously mentioned Peter Walker of Bath University.

Krahn summarises these mixes in percentages, stating the Keable’s as “50%-70% sand and gravel, 15%-30% silt and 5%-15% clay” [32] and Walker’s as “45%-80% sand and gravel, 10%30% silt and 5%-20% clay” [32] . These mixes are deemed suitable for RE construction and this is arguably the most important test that must be carried out prior to ramming.

Krahn also touches on stabilisers for RE and while this is not an exhaustive list, it certainly influenced my choice of stabilisation compound.

He touches mostly on the addition of Portland Cement to stabilise RE, with this being the most commonly used additive, he educates readers into the new ways of offsetting the cement with products like fly ash [33], to reduce the environmental impact of including cement in the mix. However, as I personally discovered later, it is nearly impossible to purchase fly ash for small scale projects, with large minimum volume per order required, putting it out of reach for individuals and small projects. This can be the reason cement is not subsidised

Fig. 10 - Jar test detailed in the Tim Krahn book mentioned Fig. 11 - Drop Test detailed in the Tim Krahn book above mentioned above.

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Fig. 12 - Cement Rammed Earth Block in the experiment setting

by other materials, which limits the positive impact stabilised RE construction can have.

However, one potential solution he states is Hydrated Lime (HL). Although similar to concrete, the lime is deemed a lower carbon footprint for a number of reasons: (1) “the parent material is fired at a lower temperature, less energy is required for the initial part of the manufacturing process” [34] (2) lime based construction materials will continue to undergo carbonation as long as they are exposed to CO₂ and the correct “temperature and vapour pressure ranges” [34] . He also suggests other additions; (1) sealants, typically added to the mix to reduce permeability to liquid water. (2) oxides which change the pigment of the mix, making for artistic use of the material (3) how much of these additives need to be included in the mix.

With the core of the experiment focusing on processes of weathering and erosion, it is important to distinguish how various weather conditions can affect the condition of RE. Wind is arguably the biggest contributor, influencing what weather arrives at a specific location and the resulting processes which wear away the material. It is key to erosion of material away from its initial place as well as the direction of rainfall which can further destroy material, with the impact against loose areas detaching it from the host. Rainfall directly affects material through processes of chemical weathering, but also indirectly, combining with changes in temperature for processes like freeze-thaw weathering which can cause deeper damage. Studies have also shown that lower humidity’s can cause soil surface moisture to be reduced, resulting in an increased susceptibility to wind erosion, which in the case of RE, would give greater erosion at surface level [35].

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18 Fig. 13 - Sub-soil sample collected from site

Experimentation The research conducted suggests the need for an experiment to understand how RE is affected by the overall process of weathering within the UK climate.

For this to be carried out, some blocks of RE were created.

THE EXPERIMENT IN CONTEXT: The experiment was conducted at my home in Welton, Lincolnshire, with Figure 18 showing the proximity of it to the nearest city, Lincoln. This is important to the experiment, with both the eventual sub-soil composition and weather conditions being specific to this place throughout the duration of testing.

Fig. 15 - Removing large rocks from sample for composition test

PRELIMINARY TESTING: To increase the realism of this experiment to a realworld setting, the use of local or on-site soil is key.

As previously stated, this is of the main driver behind RE construction, resulting in reduced emissions. I was unable to dig up the sub-soil at the experiment site, therefore, I had to find another place to obtain the sub-soil. I contacted a local building site that was excavating at the time, they agreed for me to use some of their waste sub-soil and I retrieved a sample (see left), ready for testing. Figure 14 shows the locality of this sub-soil.

Fig. 16 - Shaking the water and sub-soil mixture to all sediments to then seperate.

80 rox App

0m

Location of Sub Soil

Location of Rammed Earth Blocks

0

500m

Fig. 14 - Proximity of soil to the experiment site

As stated previously, in the absence of laboratory equipment, I used the Jar Test to obtain the soil composition information. The results showed an approximate soil composition of 70% Sand and Gravel (42/60mm), 18.3% Silt (11/60mm) and 11.7% Clay (7/60mm), making it a suitable soil for RE. (Fig. 17)

CLAY SILT SAND GRAVEL

Fig. 17 - Results of composition test

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20 Fig. 18 - Location of Experiment

21 Fig. 19 - Timeline of Experiment

Additional earth was retrieved in rubble bags (approximately 60kg) and a prototype needed to be made, in order to further understand the process on a practical level. MDF was used as the main formwork (see below) and four strips of Spruce battens were attached to the outside of the two longer pieces of MDF, to allow for even pressure distribution, a technique used in a successful home example I found online. [36] The formworks interior measurements which resulted in the block size, 12” x 12” x 5” (l x w x h), stemmed from the size of the tamper which I purchased (10” x 10’‘), a standard piece of equipment for RE making. However, when working with a larger scale wall or block, a pneumatic tamper is preferred [37], something

which was not available to me, also contributing to the block size. With the formwork made, the collected sub-soil needed screening. Using a sheet of gridded steel wire with holes sized 1.5cm x 1.5cm, ensured that no larger stones or clay pieces passed into the mix. It is at this stage where testing the moisture content of the earth mix is necessary, using the Drop Test.

The results (see Fig. 24) showed the moisture content for the prototype was suitable for ramming, with the description matching that stated by Keable. Using the Tamper and a non-specifically sized portion of wood I began ramming to create the prototype un-stabilised RE block. With this a success, I then moved to the three test blocks.

A. Bags of raw sub-soil.

B. Timber Battens fixed to MDF using screws.

C. MDF Board - aren’t fixed to anything, held in place with sash clamps that sit on the battens.

D. Complete Mould without clamps

F. Ramming begins, using 10”x 10” tamper and a non-specfic block of wood.

E. Screening method, using 1.5cm x 1.5cm gridded wire, using tressel tables to facilitate.

Fig. 20 - Equipment involved in Rammed Earth creation

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Fig. 21 - Mass of additive used.

Fig. 22 - Addition of addative to mix

Fig. 23 - Adding further water to mix

Fig. 24 - Results of Drop Test

Fig. 25 - Use of cooking oil to lubricate mould

Fig. 26 - Earth Ramming using tamper

Fig. 27 - Ramming using wood for even density on edges and corners

Fig. 28 - Spirit level to ensure flat block

The only step that differed in the creation of these three blocks was the addition of cement powder and HL into the earth mix for two of the blocks. These went into each respective mix at a ratio of 5% by mass. With the earth in each bag weighing 15kg, this meant adding 750g (see fig.21) of one of the additives to two of the earth mixes, a ratio used by the Bushey Cemetery. After checking the moisture content again, and adding any additional water necessary to the mix, the same formwork was used to make the three RE blocks.

Fig. 29 - Finished block, in this case, un-stabilised

However, during construction, some of the faces throughout the three blocks were subjected to damage during the formwork removal. This may have been due to: (1) increased moisture in one side of the formwork (2) not enough lubricant on the formwork (3) not enough drying time inside the formwork (4) excessive ramming. However, for this experiment, I could still measure the erosion with these flaws in the blocks.

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THE EXPERIMENT: Rationale and Experimental Apparatus: The experimental set up was designed alongside the limitations (see p.26). 3 blocks of RE of 12’’x 12’’ x 5’’ in size were created onto three concrete paving slabs which sat on top of four trestle tables as seen below.

These tables elevate the blocks off the floor to simulate conditions of a wall at that height (0.7m). There was one un-stabilised block, one stabilised with cement, included at a ratio of 5% by mass, and another using hydrated lime as a stabiliser, under the same ratio.

These additives were drawn from background research. They are common stabilisers of RE which are cited particularly by Krahn and Walker as methods that have been used in past earthen construction, as well as in other areas of the built environment, being a wellestablished technique in civil engineering groundworks [38] . Alongside is a Weather Station, to capture the climate in addition to

the erosion that takes place. This is attached to a metal pole which elevates the station the required 2m off the ground. This pole is attached to a non-specific piece of fence post using screws, to ensure the station doesn’t fall over in windy conditions. Finally, there are a series of holes in the ground which are used to benefit the consistent recording of photographic results.

E.

A. B.

A. B.

A.

C.

B.

A. Rammed Earth Blocks B. Concrete Paving Slabs C. Trestle Table D. Tripod Holes E. Youshiko YC9388 Weather Station

C.

D.

Fig. 30 - Experimental Setup

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Experimental Operation, measurement, and assumption Weather Recording: Recording the climate and weather was done using a Youshiko YC9388 Weather Station, recording precipitation, temperature, humidity, wind speed and direction. The device has an accuracy recording of +- 1˚C for the temperature, +- 7% for the rainfall and +- 2mph for the wind speed.

Tripod Holes: Around the setup, there are a series of selfmade holes in the ground, where the tripod legs sit. This is to ensure the resulting photos are taken from the same position, making them easy to compare. The series of photos are taken square on to each face on all the blocks, allowing for a detailed look at each face.

Point Cloud and Photogrammetry Data: As well as the photos mentioned previously, additional general photos of each block were taken, covering all faces and corners. With the absence of laboratory access for accurate profile analysis, I utilised Autodesk Recap Photo to create point cloud relief data and Rhinoceros to turn this into profiles for each block. This made for a more detailed and specific look at erosion analysis than the photos provide, allowing better comparisons. Fig.32-35 shows where each profile cut was made on each block, with the same cut taking place every time to allow for the best comparison.

Frequency of Data: The weather station collected temperature, precipitation, humidity, wind direction and wind speed data every 30 minutes from 12th September 2020 – 12th December 2020. While the photographic data was taken on a weekly basis in line with the start and end date of the experiment.

Fig. 31 - Indvidual elements of Experimetal Setup

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Assumptions: For this experiment, many assumptions have been adopted: (1) The end condition of the RE blocks made, would be the same condition to that of a larger wall, when subjected to the same climatic conditions. The blocks are a representation of a load bearing external wall. (2) The ramming process would result in the same density of each block if a pneumatic tamper had been used. With this equipment being too expensive to rent/purchase, a handheld tamper was used. (3) The values produced by the weather station are the correct ones, despite the stated accuracy range. This makes for clearer analysis of the weather vs erosion data (4) The profiles created using the photogrammetry are at the same accuracy level as lab-based analysis. This allowed me to use the profile as an indicator of erosion due to weathering for each RE block. (5) The blocks are raised off the ground using trestle tables to prevent erosion from groundwater with the absence of a concrete foundation, which most RE walls require. While this isn’t essential, it means the resulting condition of each block is only valid for a portion of wall at this height (700mm), with greater erosion potentially at the base of a wall. (6) The RE blocks are a representation of a portion of wall at the same height. The manufacturing process of a wall and these blocks is the same. However, with a shortage of time and the time frame needed to see very noticeable weathering on a full wall (20 years [28]), a test subject of this size is unnecessary for an experiment of this length. (7) RE walls often utilise roof overhangs to reduce the erosion on the walls as a result of precipitation. As this was not possible for this experiment, we must acknowledge these blocks are a valid testament for unprotected, un-maintained walls, with no mitigation for the weathering other than the additives included in the mix for each block.

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Fig. 32 - Photogrammetry section for Unstabilised block

Fig. 33 - Photogrammetry section for cement stabilised block

Fig. 34 - Photogrammetry section for Hydrated Lime stabilised block

Fig. 35 - Photogrammetry section for all blocks.

Fig. 36 - Site section to scale, showing the Experimental Setup amongst it.

Fig. 37 - Scale plan of site, showing the Experimental Setup amongst it.

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28 Fig. 38 - Image of Experimental Setup

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RESULTS:

(see appendix for all original weather data)

Fig. 39 - Humidity vs Time

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Fig. 40 - Temperature vs Daily Precipitation vs Time

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Fig. 41 - Temperature vs Rainfall rate on 04-12-20

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Fig. 42 - Wind speed and direction on site

Fig. 43 - Wind speed and direction on site, from 25-09-20 till 02-10-20

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DISCUSSION:

(For all final RE images see Supplementary Data)

Fig. 48 - Location of unstabilised face in question

Fig. 44 - Un-stabilised block on 12-09-20

Fig. 45 - Un-stabilised block on 12-12-20

VISUAL ANALYSIS: UN-STABILISED

Fig. 46 - Un-stabilised block on 25-09-20

Fig. 47 - Un-stabilised block on 02-10-20

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Throughout the duration of the experiment, we can observe that the un-stabilised block was affected by weathering the greatest out of the three blocks. The comparison between Fig. 44 (taken on 12-09-20) and Fig. 45 (taken on 12-12-20) shows the extent of the blocks degradation due to weathering, with damage caused to the left (NW) of the block in Fig. 45 being the biggest example of the damage. Moreover, we can note degradation in the upper portion of the block which has resulted in a large ‘crack’. While we cannot distinguish whether this crack goes deep into the blocks mass, it could still have caused structural complication, had this block been part of a load bearing wall. Looking at this in further detail we can see that both occurred between 25-09-20 and 02-1020 as seen in Fig. 46 and Fig. 47 respectively. During this period, approximately 15% of wind was coming from the NNW (as seen in Fig. 43) and with highs of 4 m/s reached in this time, this may have caused the material to dry too quickly, resulting in shrinkage [39] and the cracking seen in Fig. 47.

VISUAL ANALYSIS: STABILISED - HL & CEMENT When looking at the HL and cement stabilised blocks, we can observe that weathering had less of an impact on the visual appearance of both blocks, with only minor differences noticeable. For instance on the HL block in fig. 50 , where an already exposed area (seen in the upper left section of image), has eroded further over the duration of the experiment compared with the lesser erosion of the whole of the cement stabilised block. This would suggest that as a stabiliser, the HL, although slightly more sustainable, (at a ratio of 5% by mass) is not a strong enough additive to match the cements ability to withstand weathering.

Fig. 51 - Location of HL stabilised face in question

Fig. 49 - Hydrated Lime block on 12-09-20

Fig. 50 - Hydrated Lime block on 12-12-20

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When observing the south side of both the cement and HL blocks, these have weathered more, with the difference between fig. 59 and 60 showing this, with deeper and more frequent cracks appearing across the whole surface. This is possibly due to the wind directing more rainfall towards this surface, as depicted in Fig 55, although this may also be considered normal during initial exposure [40]. The reason the south side of these blocks are more exposed to wind, may be due to the local sheltering. With the adjacent house playing a huge role in breaking the wind, along with the bushes which surround the site to the NW (see Fig 56 and 57). Had the site been a completely open plain, I would expect the results to be different, with weathering more apparent on all sides of the surface. Despite this, if RE is to be used on a more widespread scale, it’s likely these structures could feature amongst existing built environments, thus providing sheltering for the material.

Fig. 52 - Cement south face on 12-09-20

Fig. 53 - Cement south face on 12-12-20

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Fig. 54 - Location of south cement stabilised face

Fig. 54

Fig. 55

Fig. 61 - Location of south HL stabilised face

Fig. 56

Fig. 57

Fig. 54,55 (Top) - Diagrams showing impact of wind on rain direction. Fig. 56,57 (left) - Diagrams showing shading from surrounding features

Fig. 59 - Hydrated Lime south face on 12-09-20

Fig. 60 - Hydrated Lime south face on 12-12-20

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= Weathered Earth

Fig. 62 - Un-stabilised block section, with difference between start and end date of experiment shown

Fig. 63 - Cement stabilised block section, with difference between start and end date of experiment shown

Fig. 64 - Hydrated Lime stabilised block section, with difference between start and end date of experiment shown

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PHOTOGRAMMETRIC ANALYSIS:

Fig. 65 - Plan section of Un-stabilised block

Fig. 66 - Plan section of cement stabilised block

Using the photogrammetric data collected, we can clearly see the un-stabilised block has weathered the most, with the left (west) side losing approximately 4mm of earth in the upper region, as seen in Fig. 62. This will have been heavily contributed by the larger wind rates between the 25-09-20 and 02-10-20 as previously discussed. Fig.62 also highlights the top surface of the block as an area which suffered the most degradation with the same pattern following on all three RE blocks. This may have been caused by lower humidity values seen during the earlier stages of the experiment, which as the research suggests, makes it easier for wind to erode the RE. The rain throughout the experiment will have also soaked into this section and the resulting freeze-thawing in the colder months will have weathered this further. Both forms of weathering are pertinent. Despite this, the top is not something which would likely be exposed in a RE wall, with protective roof canopies common on most structures.

The un-stabilised block also has weathered around every corner, with varying levels of severity, shown in Fig.65. This could have one of several explanations: (1) the corners are naturally more susceptible to weathering because of their shape in comparison to a flat surface. The wind may be applying more pressure to the corner of the block with the earth blocking its path.

(2) the construction of the corners was not to the correct standard, where less ramming could have taken place in these regions, resulting in a looser packed region of earth. As the research stated, this would make the material weaker in this area. (3) they are susceptible to damage from multiple angles, resulting in more damage over the course of the experiment, as the direction of weathering changed.

When observing the HL and cement blocks in more detail, the evidence again suggests less weathering than the un-stabilised block. This is a great testament to both additives in their respective blocks, showing they drastically decrease the weathering damage. Only areas that were affected by construction issues were

Fig. 67 - Plan section of hydrated lime stabilised block

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weathered, with these being more exposed. Of the two it’s clear the cement block is more resistant, falling in line with the previous visual analysis. Its biggest area of damage seen in Fig.66 is only 1.5mm (approximately), so it’s clear to see why this additive is preferred in examples like the Bushey Cemetery.

Much of the block retains its mass, while still offering some rough qualities that arise from being weathered over time. Had this experiment lasted for longer than three months, I would expect to see much more evenly distributed damage across the whole surface provided there are no complications in construction and surfaces remain mostly flat and smooth to begin with.

Tying this in with the overarching theme of net zero emissions, these results are incredibly positive.

They suggest that RE can be used in a built environment setting for long periods, particularly for low rise structures, where it can easily replace high embodied energy materials like concrete and cement-based materials. However, I must acknowledge that a significant amount of wear took place on the un-stabilised block throughout the duration of the experiment. When the lifetime of a building is at least 360x the length of this experiment, this is a cause for concern. It would suggest that un-stabilised RE may only be used in interior environments, away from the damage the weather can cause. Or alternatively, in temporary structures where the damage is embraced or not an issue for the material’s use. However, with this test being valid for the soil in the test region, it is possible that soil in another area with a slightly different composition may be better at withstanding weathering and erosion.

SINCE THE EXPERIMENT:

On conclusion of the experimental period, the blocks were left out for my own personal interest.

During this time, there was much lower temperatures as well as snowfall. This resulted in the HL block suffering significant damage. Fig.68 shows this damage, with clear cracking and flaking on the surface of the block. This would suggest that HL as a stabiliser is still very susceptible to mechanical weathering processes, particularly freeze-thaw. As this is part of the UK maritime climate, the HL may need further protection with outer coatings and sealants to correctly protect it for use in modern architecture.

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41 Fig. 68 - Damage to Hydrated Lime block discussed left

42 Fig. 69 - Hydrated Lime Block on a Frosty Morning

CONCLUSION: From this experiment, we can conclude that RE is definitely a viable solution for future buildings in the UK, with its low embodied energy making it attractive in the aim to Net Zero carbon emissions. However, the unstabilised RE’s performance in this study would suggest it’s inappropriate for long term building typologies.

While it could be maintained to prevent this, it may counteract the low embodied energy of the material; employing somebody to service and maintain it could be necessary, potentially increasing CO₂ emissions with commuting and machinery. Coatings and sealants could be used to increase the ability of un-stabilised RE to withstand weathering and erosion, however, there is limited research into these and something which would require additional specialist help.

On the contrary, the cement stabilised RE shows better signs for long-term use in buildings, with the experiments results supporting this, alongside the examples currently in the UK. Even though this increases the embodied energy with the use of cement, stabilised RE still has less embodied energy than many of the standard building materials used in the UK currently. In the aim to Net Zero, this could be one of many solutions.

Despite the positivity of this experiment, it is also clear that use of the material is unlikely to become widespread as constraints on soil composition and transportation of soil counteract the positive embodied energy of the material, its use could be limited to one off buildings around the country. There is also a “lack of authoritative guidance” [41] on the material, making projects more expensive and time consuming to complete. This, in my view will be the main reasons RE use doesn’t accelerate in the UK, with cost being a limiting factor in most construction. It is essential further research takes place into RE and legislation passed, if the material is to combat the aim towards net zero in the UK.

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COVID-19: Its Impact COVID-19 affected my dissertation on many different levels. Not only did it impact the topic I chose to begin with, but also elements throughout. Firstly, it affected my research. I would have tried to do a lot of in person research, meeting with professionals and visiting RE buildings around the country. With one (Hill Holt Wood) nearby this would’ve been an incredibly beneficial experience towards the project and I would’ve been able to get first-hand, primary research, from the few people who have had experience with the material. It also affected the measuring methods within my project and therefore the location. Ideally, I would have liked to have measured the change in depth of the RE more accurately, using specialist equipment like the stereophotogrammetry that is used in the example study in Lyon. This would have increased the quantitative data my experiment provided, which could’ve been useful for necessary research in the future. Stated in my limitations, it also affected the equipment I used to make the RE blocks, had I been able to source the correct formwork and a pneumatic tamper, I believe this would have made for more refined construction of the RE itself.

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45 Fig. 70 - Cement Block on a Frosty Morning

Supplementary Data

Link to all 168 Tripod Images taken throughout the entirety of the experiment

Link to all 44 Tripod Images taken throughout the entirety of the experiment

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www.greenspec.co.uk. (n.d.). GreenSpec: Environmental Advantages of Rammed Earth Construction. [online] Available at: https://www.greenspec.co.uk/building-design/rammed-earth/. [Accessed 09 July 2020] Wikipedia. (2020). Photogrammetry. [online] Available at: https://en.wikipedia.org/wiki/ Photogrammetry#:~:text=Photogrammetry%20is%20the%20science%20and [Accessed 25 Jan. 2021] Society, N.G. (2018). erosion. [online] National Geographic Society. Available at: https://www. nationalgeographic.org/encyclopedia/erosion/#:~:text=1%2F9-. [Accessed 25 Jan. 2021] Society, N.G. (2018). weathering. [online] National Geographic Society. Available at: https://www. nationalgeographic.org/encyclopedia/weathering/#:~:text=Weathering%20is%20the%20breaking%20 down. [Accessed 25 Jan. 2021].

Books: Sauer, M, & Kapfinger, O (eds) 2015, Martin Rauch: Refined Earth : Construction and Design with Rammed Earth, Detail Business Information GmbH, The, München. Available from: ProQuest Ebook Central.

Dethier, J. (2020). The art of Earth architecture : past, present, future. New York: Princeton Architectural Press.

Krahn, T. (2019). Essential rammed earth construction : the complete step-by-step guide. Gabriola Island: New Society Publishers Walker, P. (2005). Rammed earth : design and construction guidelines. Watford: Bre Bookshop Stevenson, A. (2010). Oxford dictionary of English. Oxford: Oxford University Press ; New York.

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LLIST OF FIGURES: Cover: Image by Author Fig.1, 2 : Image by Author Fig. 3: Department for Buisiness, Energy & Industrial Strategy (2020). 2018 UK Greenhouse Gas Emissions, Final figures. [online] Available at: https://assets.publishing.service.gov.uk/ government/uploads/system/uploads/attachment_data/file/862887/2018_Final_greenhouse_ gas_emissions_statistical_release.pdf [Accessed 12 May 2020].pg.6 Fig. 4: Simply Environmental. (n.d.). Introduction. [online] Available at: http://www.simplyenviro. com/sustainablebuilding [Accessed 12 May 2020] Fig. 5: The Architects’ Journal. (2016). On site at Waugh Thistleton’s extension of the Bushey Jewish Cemetery. [online] Available at: https://www.architectsjournal.co.uk/buildings/on-site-atwaugh-thistletons-extension-of-the-bushey-jewish-cemetery [Accessed 14 May. 2020].

Fig. 6: ottersurfboards.co.uk. (n.d.). Otter Surfboards | Where We Work. [online] Available at: https://ottersurfboards.co.uk/journal/where-we-work [Accessed 10 Jan. 2021].

Fig. 7: Image by Author Fig. 8,9: Bui, Q.B., Morel, J.C., Venkatarama Reddy, B.V. and Ghayad, W. (2009). Durability of rammed earth walls exposed for 20 years to natural weathering. Building and Environment Fig. 10: Krahn, T. (2019). Essential rammed earth construction : the complete step-by-step guide.

Gabriola Island: New Society Publishers. pg.40 Fig. 11: Krahn, T. (2019). Essential rammed earth construction : the complete step-by-step guide.

Gabriola Island: New Society Publishers. pg.36 Fig. 12 - 70: Image by Author

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APPENDICES:

All Photos, including those which created the photogrammetry images

Complete set of original weather data recorded throughout the experiment.

All Evidence Photos of Making Process

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