Non-Stabilised Rammed Earth Constructions

Department

Alexandre Robert McCormack

Bertrand François

Université libre de Bruxelles

Vrije Universiteit Brussel

Department of architectural and civil engineering

Brussels May 2013


Supervisor :

Bertrand François



of architectural and civil engineering

Brussels May 2013


Bertrand François




Brussels May 2013


0

1

Abstract Earth constructions are gaining in popularity yet are still rarely subject

to thorough academic research and are almost unknown to the general

public. However, they present considerable environmental advantages

in a time when the concerns of energy and lifecycle assessment are at

their highest. The main concern with non-stabilised earth is the strength

of the material compared to default construction materials such as steel

or concrete. In this master thesis, the aim is to present the

characteristics of non-stabilised rammed earth constructions and

implement them into a project design adapted to a temperate climate.

Geotechnical testing had to be modified to identify the parameters

which contribute to the compressive strength of rammed earth

constructions. Once non-stabilised rammed earth had been established

as a feasible construction material, the characteristics were applied to

an urban Co-Housing project in Brussels.

Water content and compaction energy were found to be the largest

contributor to the strength of the material. A compressive strength of

3.8 MPa was achieved with a fine grain soil classified as clayey silt.

Furthermore, under ambient interior humidity it was demonstrated that

at least part of a wall could attain an increase in strength through the

natural drying process leading to a compressive strength of 7MPa.

However, contrary to what was predicted, grain-size distribution did not

play a further role in optimising compressive strength as a lesser value

of 2.4MPa was reached. A possible advantage for a well graded soil

would be to prevent shrinkage. On the other hand, the shrinkage limit

was well over the water content used for the finer grain soil.

Without further analysis on a full scale rammed earth wall of the

possible influence of shrinkage and cracking, 2.4 MPa was used for the

project design. It was demonstrated that non-stabilised rammed earth

could be adapted to a 4 storey building using a minimum of 70cm thick

walls and a security factor superior to that of uncontrolled masonry. All

the characteristics and implications of a non-stabilised rammed earth

construction were fulfilled in the design of the Co-operative housing

project and even instilled further ideas such as participatory building.

2

Acknowledgements It could not have been done without the people who were behind me. I’d

like to thank the following:

My supervisor, Bertrand François gave me the opportunity to carry out

this master thesis. It has been the most passionate part of my five years of

studying architectural engineering.

Paul Jacquin took his time to read and answer all my questions during the

year. He and his work have been brilliant guidance.

Nicolas Canu has been of great help in the laboratory. He showed me all

the technical material and was always there whenever I had a problem.

The whole team I worked with on the rammed earth construction

workshop in April 2012 in Flanders. They have certainly helped in my

personal attraction for rammed earth. Thank you to Quentin Chansavang

and Hugo Gasnier from CRATerre for their contribution.

3

Table of Contents Abstract ....................................................................................................... 1

Acknowledgements ..................................................................................... 2

List of Figures ............................................................................................... 5

List of Tables ................................................................................................ 6

Photos .......................................................................................................... 6

List of Drawings ........................................................................................... 6

Introduction ................................................................................................. 7

Rammed Earth Constructions ..................................................................... 7

Part One : Material Characteristics ............................................................. 1

1 Environmental advantages and lifecycle assessment of Rammed

Earth ............................................................................................................ 2

1.1 Embodied Energy ......................................................................... 2

1.1.1 Concrete and Steel .............................................................. 2

1.1.2 Rammed Earth ..................................................................... 2

1.1.3 Embodied energy compared to the total building .............. 3

1.2 Recyclability ................................................................................. 3

1.3 Natural Resource Abundance ...................................................... 4

1.4 Water consumption ..................................................................... 4

2 Building properties .............................................................................. 4

2.1 Thermal inertia ............................................................................. 4

2.2 Hygrometry .................................................................................. 4

2.3 Fire safety ..................................................................................... 4

2.4 Thermal transmittance ................................................................. 4

3 Soil Characterisation (François, 2011; Verbrugge, 2010) ..................... 5

3.1 Porosity ........................................................................................ 5

3.2 Water content .............................................................................. 5

3.3 Bulk density .................................................................................. 5

3.4 Dry bulk density ............................................................................ 5

3.5 Soil structure and fabric ............................................................... 6

3.6 Soil-water interaction ................................................................... 6

3.7 Grain-size distribution .................................................................. 6

3.7.1 Dry sieving analysis .............................................................. 6

3.7.2 Sedimentation analysis ........................................................ 6

3.8 Shrinkage limit .............................................................................. 6

3.9 Compaction .................................................................................. 6

3.10 Proctor compaction test............................................................... 7

4 Soil classification .................................................................................. 7

4.1 Grain size classification ................................................................ 7

4.2 Consistency limits ......................................................................... 8

5 Compressive Strength Characteristics of RE ........................................ 8

4

5.1 Laboratory Testing ....................................................................... 8

5.2 Soil preparation ........................................................................... 8

5.3 Soil identification ......................................................................... 8

5.4 Standard geotechnical testing ..................................................... 8

5.4.1 Normal proctor test ............................................................. 8

5.4.2 Unconfined Compression .................................................... 9

5.5 Optimising soil structure with grain-size distribution ............... 10

5.5.1 Optimum normal proctor .................................................. 11

5.6 Adapting the testing procedure ................................................ 11

5.6.1 Compaction energy ........................................................... 11

5.6.2 Compressive strength of optimally mixed soil .................. 11

5.7 Cohesion .................................................................................... 12

5.8 Suction ....................................................................................... 12

5.9 Hygrometry ................................................................................ 13

5.10 Size of samples .......................................................................... 15

5.10.1 Increased size of cylindrical sample .................................. 16

5.10.2 Imperfections .................................................................... 16

5.11 Type of ramming ....................................................................... 16

5.12 Shrinkage ................................................................................... 16

Part Two : Application to Urban Co-Housing in Brussels .......................... 18

1 Identified technical characteristics ................................................... 22

1.1 Insulation .................................................................................... 23

2 Co-Operative housing......................................................................... 23

2.1 Multigenerational bartering ....................................................... 24

2.2 Multiple sociological backgrounds ............................................. 24

2.3 Participatory building ................................................................. 24

3 Tour et Taxi......................................................................................... 25

3.1 Local soil ......................................................................................... 26

4 Concept and Development ................................................................ 26

4.1 Context ....................................................................................... 26

4.2 Preliminary approach ................................................................. 27

4.3 Orientation and Sunlight ............................................................ 27

4.4 Internal Walls ............................................................................. 29

5 Predimensioning ................................................................................ 31

5.1 Load calculations ........................................................................ 31

5.1.1 Floor loads .......................................................................... 31

5.1.2 Self-weight ......................................................................... 31

5.1.3 Combination of permanent and variable actions .............. 31

5.2 Resistance to vertical loads ........................................................ 31

5.2.1 Security factor .................................................................... 31

5.2.2 Vertical lifting loads ................................................................ 32

5.3 Resistance to horizontal loads (Wind) ....................................... 32

5

6 Sustainability ..................................................................................... 33

6.1 Construction materials .............................................................. 33

6.2 Net zero energy building ........................................................... 33

6.3 Green roofs ................................................................................ 33

6.4 Solar panels ............................................................................... 33

6.5 Aquaponic systems .................................................................... 33

6.6 Water harvesting system ........................................................... 33

ANNEX ....................................................................................................... 43

1. Identification paper for MLD soil used in tests ................................. 43

2. Rammed Earth Workshop April 2012 : Construction of 50m² hunting

house (photos by Nicolas Coeckelberghs) ................................................. 50

List of Figures Figure 1 : Embodied energy comparison of different construction

materials (Prof.Geoff Hammond, 2008) ...................................................... 2

Figure 2 : Energy for concrete structure compared to total initial

embodied energy ........................................................................................ 3

Figure 3 : Energy for concrete structure compared to total amount of

energy necessary over 100 years including replacement of materials ....... 3

Figure 4 : Normal proctor compaction test for MLD soil ............................ 8

Figure 5 : Compressive strength of equivalent dry density samples at

different water contents .............................................................................. 9

Figure 6 : Grain-size optimisation of MLD soil with sand and gravel ......... 10

Figure 7 : Compressive strength of compacted mixed soil at different

water contents ........................................................................................... 11

Figure 8 : Compressive strength of compacted non-mixed MLD soil at

different water contents ............................................................................ 12

Figure 9 : Variation of mass of water in soil samples over 28 days at

ambient interior relative humidity (+/- 40% RH, +/- 22°C) ........................ 13

Figure 10 : Variation of mass of water in soil samples over 28 days at

controlled relative humidity simulating rainy conditions (94% RH, 22°C) . 13

Figure 11 : Compressive strength of compacted non-mixed MLD soil

specimens after 28 days at given relative humidity .................................. 14

Figure 12 : High compaction energy non-mixed MLD soil at 8% water

content at 50% relative humidity during 28 days ...................................... 14

Figure 13 : Compressive strength comparison of maximum dry density

sample at 28 days under ambient interior conditions ............................... 14

Figure 14 : Scheme of characteristic implementation of rammed earth to

architecture ................................................................................................ 22

Figure 15 : Google Earth view on Tour et Taxi, Brussels Local soil ............ 25

Figure 16 : Penetration test point N°794 Tour et Taxi, Brussels, ULB soil

mechanics laboratory ................................................................................. 26

Figure 19 : Diagram summarising stages of research ................................ 44

6

List of Tables Table 1 : Estimated U-value for rammed earth and with added 10cm cork

insulation ..................................................................................................... 5

Table 2 : Grain-size classification of the ABEM/BVSM (François, 2011) ..... 7

Table 3 : Laboratory standards of compaction test .................................... 7

Table 4 : Dimensions of samples used for testing ..................................... 16

Table 5 : Permanent loads used for pre-dimensioning wall thickness ...... 31

Table 6 : Variable loads used for pre-dimensioning wall thickness .......... 31

Table 7: Characteristics and identification table of MLD soil used for

testing ........................................................................................................ 43

Table 8 : Grain-size distribution curve of MLD soil.................................... 43

Table 9 : ABEM/BVSM soil classification (François, 2011) ........................ 43

Photos Photo 1 : Context scale model of Tour et Taxi, Brussels ........................... 28

Photo 2: Unconfined compression and comparison of size 1 and size 2

samples ...................................................................................................... 45

Photo 3 : Unconfined compression for small size samples ....................... 45

Photo 4: Some sheared samples ............................................................... 45

Photo 5 : Rammed Earth Block 15cm well graded soil .............................. 46

Photo 6 : Ramming 15cm block with 6kg hammer via a wooden piece ... 46

Photo 7: Laminated sample due to high compaction energy and low water

content ...................................................................................................... 47

Photo 8 : Diagonal and cone shearing ....................................................... 47

Photo 9 : Preparation of soil dried at approximately 35°C ........................ 48

Photo 10 : Bell for controlled relative humidity ......................................... 48

Photo 11: Sheared sample with non-parallel surfaces .............................. 49

List of Drawings Drawing 1 : Site implantation 1/ 500 ......................................................... 30

Drawing 2 : Sustainability scheme ............................................................. 31

Drawing 3 : Ground floor 1/200 ................................................................. 32

Drawing 4 : Second floor 1/200................................................................. 33

Drawing 5 : Third floor 1/200 ..................................................................... 34

Drawing 6 : Fourth floor 1/200 .................................................................. 35

Drawing 7: Section AA' ............................................................................... 36

Drawing 8 : Section BB' .............................................................................. 37

Drawing 9 : Section CC' .............................................................................. 38

Drawing 10 : Second floor plan insulation ................................................. 39

Drawing 11 : Render 1 ................................................................................ 40

Drawing 12 : Render 2 ................................................................................ 41

Drawing 13 : Render concept colour .......................................................... 42

Drawing 14 : Render 4 passageway ........................................................... 43

7

Introduction The aim of this master thesis is to demonstrate the feasibility of earth as a

construction material and more specifically within the rammed earth

technique. It is developed to draw more attention towards this building

material from the scientific academia as well as the general public.

The thematic was essentially oriented towards non-stabilised rammed

earth where adding concrete or lime diminishes some beneficial

characteristics of the material. Besides the positive aspects of using earth

as constructions, the main concern and disadvantage of non-stabilised

rammed earth compared to modern construction materials is

fundamentally its strength. On this behalf, the study takes place in two

parts. First earth is defined as a construction material by identifying its

characteristics. Secondly, the application of these characteristics and the

achieved strength was implemented into a design case in order to

illustrate its possibilities but also to understand its limits in modern

architecture.

Identifying the material characteristics was done mainly in three parts.

First it was pointed out the environmental advantages that make earth

buildings so appealing and secondly the material was viewed from

geotechnical standards. The third part takes part in identifying the main

parameters contributes to the optimisation and development of the

strength of the material. This was achieved by laboratory testing.

Rammed Earth Constructions The use of earth in buildings stretches back well over a millennia

(A.Jacquin, 2008). Different techniques have been developed to achieve

sufficient strength to be used as a construction material. One among

these techniques is rammed earth or so called pise.

The technique of rammed earth is usually found in arid climates where

the soil is drier. It consists of compacting successive layers of

approximately 12 to 15cm of soil inside a formwork. The strength

developed by this technique relies essentially in the compactness

achieved. Historically, this was done by hand generally using a wooden

rammer. In modern rammed earth buildings, pneumatic rammers are

used to make it slightly less labour intensive and can help achieve a much

higher compacting rate. However, even with this modernised technology

this type of construction still remains very labour intensive. Although the

construction material is cheap, the amount of labour needed renders

these projects today rather expensive. If a market was developed for

rammed earth buildings, the technique could be adapted and

industrialised thus reducing labour cost. It would most certainly also

favour control over the material.

1

Part One : Material Characteristics

1

1.1The

designing sustainable architecture.

materials is still rarely taken into account

to con

environment and directly or indirectly causes CO2 emissions. This needs

to be factored in if high energy material is necessary for all structural

cases of a building. We need to compare the embo

earth with that of concrete and steel, generally the default building

materials in modern architecture.

1.1.1

According to the so called “

energy in materials, it can be demonstrated

1GJ/m3. The same procedure for steel gives 23GJ/m3. However,

considering the Crawford (2011) procedure, concrete requires

and steel 85.46 GJ/m3. The Crawford (2011) is a much more precise

technique for calculating embodied

the elements required for the processing of the material itself. Obviously,

to properly compare the materials, we must take into account the ratio of

the embodied energy over the E

enormous strength, less is required when it comes to designing the

structure.

1 Environmental

assessment

1.1 Embodied EnergyThe lifecycle assessment



to consider. The energy used to process the material impacts on the






1.1.1 Concrete and Steel

According to the so called “








the embodied energy over the E


structure.

Environmental advantages

ent of Rammed Earth

Embodied Energy lifecycle assessment of a building is of the utmost concern when



sider. The energy used to process the material impacts on the






Concrete and Steel

According to the so called “process analysis








the embodied energy over the E-modulus of the material. If a mater


advantages and lifecycle

of Rammed Earth

of a building is of the utmost concern when

designing sustainable architecture. Embodied energy in construction

materials is still rarely taken into account yet remains an important aspect




cases of a building. We need to compare the embodied energy of rammed


process analysis” for defining embodied

energy in materials, it can be demonstrated that concrete requires




technique for calculating embodied energy as it takes into account all of



modulus of the material. If a mater


lifecycle


mbodied energy in construction

remains an important aspect




died energy of rammed


” for defining embodied

that concrete requires


considering the Crawford (2011) procedure, concrete requires 5.01GJ/m3


energy as it takes into account all of



modulus of the material. If a material has



mbodied energy in construction

remains an important aspect




died energy of rammed


” for defining embodied

that concrete requires


GJ/m3


energy as it takes into account all of



ial has


1.1.2

It is still very difficult to determine the embodied energy of a material. In

the case of the construction of a rammed earth project of 50m2, it was

possible

of 1 cubic metre of rammed earth. Fuel was needed for ramming and in

some cases for drying the soil with a heater. The fossil fuel consumption

was then converted to the amount of energy requir

not sufficient to calculate

of the soil was carried out by

earth mixer and sand and gravel had to be transported to the site, but

manpower was used

slightly over

in the order of M

estimated that non

0.5GJ/m3

embodied energy of

Figure

(Prof.Geoff Hammond, 2008)

Em

bo

die

d E

ne

rgy

1.1.2 Rammed Earth



possible to quantify the amount of fuel required for the implementation




not sufficient to calculate

of the soil was carried out by


manpower was used

slightly over-estimate each of these components, the total

in the order of MJ’s per cubic metre

estimated that non-stabilised rammed earth ha

0.5GJ/m3 (Clare Lax, 2010)

embodied energy of other materials

Figure 1 : Embodied energy


0

5

10

15

Em

bo

die

d E

ne

rgy

GJ/

m3

Rammed Earth



to quantify the amount of fuel required for the implementation




not sufficient to calculate the total embodied energy used.

of the soil was carried out by an excavator, the soil was mixed with an


manpower was used for mixing and carrying. Nevertheless, even if we

estimate each of these components, the total

J’s per cubic metre. With more precise calculations, it is

stabilised rammed earth ha

(Clare Lax, 2010) and therefore is

other materials (see

: Embodied energy comparison


Construction materials






was then converted to the amount of energy required. However, this is

the total embodied energy used.

excavator, the soil was mixed with an


for mixing and carrying. Nevertheless, even if we

estimate each of these components, the total

. With more precise calculations, it is

stabilised rammed earth has an embod

and therefore is low

see Figure 1).

comparison of different construction

Construction materials






ed. However, this is

the total embodied energy used. The excavation




estimate each of these components, the total energy used is


s an embodied energy of

compared to the

construction materials

2






ed. However, this is

The excavation




energy used is


ied energy of

compared to the

materials

It should be pointed out that the embodied energy for steel or other

metals is disproportional when compared to other materials. H

the E

quantity of steel used. It is for this reason that in order to compare

realistically the embodied energy of materials,

should

rammed earth walls are twice or three times (sometimes more) thicker

than concrete walls.

1.1.3According to ULB PhD student André

passive house represents 18.2% of the in

materials

eventual replacement of some of these. However, taking into account the

consumption of the building over 100 years, the energy used in the

creation of a conc

(see figure 3

building above all other aspects. However, if we look at the accumulation

of this percentage over a large number of dwellings,

becomes considerable. For rammed earth buildings, this percentage

would be insignificant and so continue to contribute to a decrease in the

environmental footprint of the building. This is just one aspect of the

lifecycle assessment, yet th

environmental footprint of a material.



the E-Module of steel is consider



should be taken into consideration



1.1.3 Embodied energy compared toAccording to ULB PhD student André


materials (see figure 2



creation of a conc

see figure 3). This clearly demonstrates the importance of insulating a






lifecycle assessment, yet th




of steel is considerably high, thus reducing the sections and



be taken into consideration



Embodied energy compared toAccording to ULB PhD student André


see figure 2) and 7.2% over 100 years if one considers the



creation of a concrete structure represents only 3.7% of the total energy

. This clearly demonstrates the importance of insulating a






lifecycle assessment, yet there are other variables that establish the




ably high, thus reducing the sections and


realistically the embodied energy of materials, the sections generally used

be taken into consideration. For example, It could be argued


Embodied energy compared to the totalAccording to ULB PhD student André Stephan, a concrete structure of a

passive house represents 18.2% of the initial embodied energy of all

and 7.2% over 100 years if one considers the



rete structure represents only 3.7% of the total energy







ere are other variables that establish the



metals is disproportional when compared to other materials. However,



the sections generally used

It could be argued


the total building tephan, a concrete structure of a

itial embodied energy of all







of this percentage over a large number of dwellings, the energy then






owever,



the sections generally used

It could be argued that


tephan, a concrete structure of a

itial embodied energy of all







the energy then





1.2 Some movements

as the cradle to cradle concept. There is a tendency now to exploit

recyclable

It is essential that bui

they will last forever. Perhaps this is not the way to view things, for

although some buildings last for a century or more there is always the

possibility t

urban area evolves;

years later. We have seen also,

and the following recession, how

considerably and how we inherited vistas of

demand ceased

that construction was suspended and

years to come.

Figure

structure compared to total amount of

energy necessary over 100 years

including replacement of materi

Recyclability Some movements are taking into account the lifecycle of materials such


recyclable materials as much as possible.

It is essential that bui



possibility that they will be replaced as technologies emerge or as an

urban area evolves;

years later. We have seen also,



demand ceased. If we take the examples of Ireland and Spain, we will see


years to come.

Figure 3 : Energy for concrete



including replacement of materi

18,2

81,8

Recyclability are taking into account the lifecycle of materials such


as much as possible.

It is essential that buildings last in time, but it may be a bias to believe



hat they will be replaced as technologies emerge or as an

dwellings built in the 70’s were destroyed 20 or

years later. We have seen also, particularly in the recent economic boom



If we take the examples of Ireland and Spain, we will see


: Energy for concrete



including replacement of materials

Embodied energy of

concrete structure

Rest of embodied

energy

Embodied energy of

concrete structure

Energy Consumption

and rest of embodied

energy including

material replacement

are taking into account the lifecycle of materials such


as much as possible.

ldings last in time, but it may be a bias to believe




built in the 70’s were destroyed 20 or

particularly in the recent economic boom

and the following recession, how construction demand

considerably and how we inherited vistas of urban scarification


that construction was suspended and structural skeleton

Figure 2 : Energy for concrete

structure compared to total

initial embodied energy

Embodied energy of

concrete structure

Rest of embodied

Embodied energy of

concrete structure

Energy Consumption


energy including

material replacement







built in the 70’s were destroyed 20 or 30


truction demand increased

urban scarification when the


structural skeletons left visible for

: Energy for concrete

structure compared to total

initial embodied energy

96,3

Embodied energy of

Energy Consumption


material replacement3







30


increased

when the


for

3,7

4

1.3 Natural Resource Abundance Soil is one of the most predominant materials on earth. It is abundant

and can be considered universal to some extent. A US geological survey

shows that over half of the world’s production of cement comes from

China (Oss, 2011). Using soil as a building material would avoid

dependency on importation and could also prevent some change in

landscapes due to excessive excavation. Moreover, organic soil is

incompatible with earth construction and would not encroach on

agricultural activity.

1.4 Water consumption There is a growing concern on freshwater scarcity in the world (Arjen Y.

Hoekstra, 2012). Concrete requires a large fraction of drinking water for

hydration reaction. The soil used in rammed earth building needs to be at

the drier state which often leads to actually drying the soil rather than

adding water to it.

2 Building properties

2.1 Thermal inertia It has been established in the case of low energy buildings that internal

gains can become overwhelming requiring cooling systems to

compensate. Thick walls that serve as thermal inertia can compensate the

increase of heat. Furthermore, there is natural thermal regulation during

summer as walls cool during the night and absorb the heat during the day.

As materials are improving and the amount we use in construction has

financial consequences, we tend to minimise as much as possible

materials used thus dealing with sometimes thin structures.

2.2 Hygrometry It has also been demonstrated that earth walls quickly absorb or emit

water in the air in accordance with the ambient relative humidity. Dr Paul

Jacquin shows that the pores in the earth walls become natural

regulators. Relative humidity is an important factor in the interior quality

of a building. This is one of the reasons that living in an earth home is

qualified as being very comfortable.

2.3 Fire safety Rammed Earth is an inert material and is classified as non-combustible.

The Commonwealth Scientific and Industrial Research Organisation

(CSIRO) gives a fire resistance rating of 4 hours (Earth Structures (Europe),

2013).

2.4 Thermal transmittance Rammed earth has a low insulating performance that can go up to a U-

value of 2.0 W/m²K for a 300mm thick rammed earth wall (Vasilios

Maniatidis, 2003). Passive houses in Belgium deal with values in the order

of 0.15W/m2K (Descamps, 2012). The presented values in Table 1 can are

estimated for different wall thicknesses assuming the thermal

conductivity is λ = 0.6 W/m.K. It was also calculated with 10cm of added

corkboard (EnviroNomix, 2009).

5

3 Soil Characterisation (François, 2011; Verbrugge, 2010) Soil is composed of solid particles that vary in size and nature. Voids

between particles are filled with air or water. This leads to a three phase

material and it is important to be able to define these phases in order to

identify the structure of the soil. The deformation properties and

resistance created by the soil depend essentially on how each phase is

dealt with.

3.1 Porosity

� =��

��

The porosity is defined by the ratio of the volume of voids in the material

that are either a liquid or gas phase to the total volume of soil.

When all the pores of the soil are filled with water, it is called a saturated

soil, when they are only partially filled it is an unsaturated soil.

3.2 Water content

� = �

�

This is the mass of water over the mass of solid particles. It is an

important factor in rammed earth constructions.

In order to determine the water content, a mass of soil is measured in its

specific state. It is then dried in an oven at 105°C for 24 hours and re-

weighted in order to determine the loss of water. �� = � + �

3.3 Bulk density

� = ��

��

This unit is kg/m3 and is defined by the mass of soil over the total volume.

Again an important factor when it comes to the material characteristics of

rammed earth.

There are various ways in which the bulk density is determined

experimentally. In this study, it was achieved quite simply, since the

volume of the samples was known and the mass of soil was determined

just by weighing the samples.

3.4 Dry bulk density

�� = �

��

Usually, we take into account the dry bulk density which is the dry mass of

soil over the total volume.

Wall thickness 0,30 0,40 0,50 0,60 0,70 0,80 0,90

U-value RE 1,51 1,21 1,01 0,86 0,75 0,67 0,60

+ 10 cm cork 0,32 0,30 0,29 0,27 0,26 0,25 0,24

Table 1 : Estimated U-value for rammed earth and with added 10cm cork insulation

6

3.5 Soil structure and fabric We generally distinguish granular soils and fine-grained soils for which the

mechanical behaviour differs. In granular soils, resistance is mainly by

friction between coarse particles, finer soils generate their resistance

essentially via physico-chemical forces between thin particles.

For rammed earth constructions, we deal with dense soil where particles

are tightly agglomerated.

3.6 Soil-water interaction Three types of water are constituted in the structure of soil: free water

which fills the large voids; absorbed water which is strongly linked to clay

platelets and form water bridges between particles and finally

constitutive water which enters the composition of clay platelets and is

thus considered part of the solid phase.

3.7 Grain-size distribution

3.7.1 Dry sieving analysis Sieves of decreasing mesh size are stacked one on top of the other. A

mass of dry soil is placed on top and the stack of sieves is then shaken for

a given amount of time. Each sieve recuperates a fraction of the soil

corresponding to a specific size of particles.

3.7.2 Sedimentation analysis For particles finer than 0.74 µm, a different procedure is needed to

establish the grain size. The sedimentation analysis is based on Stockes

law which leads to a relation between falling velocity of a spherical

particles to their diameter. The standard procedure is made by dispersing

soil particles in a column of water and estimating their rate fall. In order

to establish this, the density is measured over time with a hydrometer.

Coarser particles will sink faster, thus reducing the density at the top of

the column.

3.8 Shrinkage limit As it dries, soil will continue to shrink until it reaches the shrinkage limit.

This is established by measuring the volume at different times during the

drying process. The volume is measured through submersion in mercury

and the water content given by weighing the specimen.

It is crucial for soil used in rammed earth constructions to be under the

shrinkage limit or cracks or even stability problems will occur during the

drying process of the walls.

3.9 Compaction In geotechnical engineering it is known that compaction has a key role in

the mechanical properties of soil. The efficiency of compaction depends

on the soil, the water content, the compaction energy, the type of

compaction (dynamic or static) and the timing of compaction. Rammed

earth constructions are generally formed by using dynamic compaction in

the framework. It should be added, particularly in this type of

construction, that the thickness of the layers successively compacted will

affect the dry density achieved and therefore optimise the mechanical

properties.

7

3.10 Proctor compaction test This test has been standardised in soil mechanics for field compaction. It

determines the relation between water content and dry bulk density in

order to establish the optimum water content. There are various

standards that differ in compaction energy such as the number of

compacted layers or the dimension of the mould as addressed here in this

table (Table 3).

Normal

Proctor

Modified

Proctor

Mould

Diameter [mm] 152,4 152,4

Height [mm] 127 127

Volume [dm3] 2,316 2,316

Rammer

Diameter [mm] 50,8 50,8

Mass [kg] 2,49 4,54

Drop height [mm] 305 457

Number of drops per layer 55 55

Number of layers 3 5

Energy [Nm or J] 1229 5593

Volumetric energy [MJ/m3] 0,531 2,415

Table 3 : Laboratory standards of compaction test

Usually, at least five points are addressed on the curve. The water content

is verified precisely by extruding a soil specimen from the top, middle and

bottom of the mould.

In this master thesis, we will see that the standard geotechnical proctor

test is unsuitable for the study of rammed earth and that we are generally

dealing with far greater compaction energy.

4 Soil classification

4.1 Grain size classification Particles are categorised by their grain size into different groups: gravel,

sand, silt and clay (Table 2). Sand can be subdivided into coarse, medium

and fine yet the classifications depend on what terminology is used.

Identifying particles only by their grain size can lead to false indications as

some clay platelets may have the same dimensions as silt or vice versa yet

they differ from a mineralogical point of view.

Table 2 : Grain-size classification of the ABEM/BVSM (François, 2011)

Fraction number Name of group Range of diameter (mm)

I Clay <0,002

II Silt 0,002-0,06

III Fine Sand 0,06-0,2

IV Coarse Sand 0,2-2

V Gravel 2-20

VI Stone >20

8

4.2 Consistency limits In order to better qualify the soil and at the same time consider some of

its mechanical properties, classifications such as ABEM/BVSM have taken

into account the plasticity index in the criteria.

5 Compressive Strength Characteristics of RE

5.1 Laboratory Testing The aim of the laboratory testing was to understand the characteristics

leading to maximum compressive strength in rammed earth. The

identification of the parameters was performed by questioning former

publications on the subject of non-stabilised rammed earth. The starting

point was from standard geotechnical testing.

5.2 Soil preparation Soil used throughout the whole study originated from Marche-les-Dames,

Belgium. Once it had arrived at the laboratory, it was first dried in small

layers on plates in a hot room at approximately 40°C, over several days.

The soil was then collected and separated in a grinder without altering the

particles. A water content of approximately 0-0.3% was obtained yet

throughout testing this was considered null. Anytime a specific water

content was needed, the corresponding amount of distilled water was

added and thoroughly mixed. To ensure the soil had uniformly distributed

the water between particles, it was kept in a cool room for over 24 hours

in a sealed bag.

5.3 Soil identification Sieving and sedimentation analysis tests were carried out to specify the

grain-size distribution. Liquid and plastic states were delimited with their

respective experimental determinations. The soil identification is given in

anew.

5.4 Standard geotechnical testing

5.4.1 Normal proctor test

The density and water content were defined with a standard proctor test.

The normal proctor test was performed 3 times for each of 5 different

water contents. The optimal water content was 14.79% and dry density

was 1840kg/m3 (See figure 4).

Figure 4 : Normal proctor compaction test for MLD soil

17,20

17,40

17,60

17,80

18,00

18,20

18,40

18,60

10 11 12 13 14 15 16 17 18 19 20 21

gd

(K

N/m

³ )

w (%)

Saturation Line

9

5.4.2 Unconfined Compression

Cylindrical samples of 72mm in height and 36mm in diameter were made

at first using a static compaction method. The cylindrical mould was

lubricated before the soil was put in order to reduce friction at release.

The mass of soil and its water content used for the testing was

determined with the optimum proctor. For each compression, 3 to 4

samples were tested for statistical consistency. All samples were put

under unconfined compression. The displacement of the press was at

0.0667mm/min and the stress and strain was taken every 2 seconds.

5.4.2.1 Specimen at optimum proctor water content

The first samples sheared at 0.23 MPa into a barrel shape. The soil clearly

demonstrated high plasticity and was not suitable for rammed earth. The

resulting compressive strength was demonstrated to be much too low to

be exploitable as a construction material.

5.4.2.2 Dried specimen

The water content appeared to be too high thus contributing to the

plasticity of the soil. To complement this observation, the same samples

were put into a confined chamber set at 30°C for 14 days. Under the same

conditions they sheared abruptly with a quick cracking sound at 5 MPa.

The water content was found to be 1.8%. It is unclear whether any

chemical reaction occurred within the clay platelets or if the soil structure

had been altered at this temperature. It seemed that the conditions set by

standard geotechnical procedures were unsuitable for testing the

strength characteristics of rammed earth. However, the first parameter to

be identified that could play key role was the water content of the

material. It was assumed that by initially lowering the water content, it

may increase the compressive strength.

5.4.2.3 Equivalent dry density

The same soil samples at different water contents (2%, 4%, 6%, 8%, 10%),

were taken while decreasing the dry density to 1732kg/m3. This dry

density was meant to reflect the dry density achieved during the standard

proctor test. However, the optimum proctor dry density could not be

achieved with 2% water content so a slightly lower overall dry density was

taken. High compaction energy and high density leaded to lamination of

samples (See Photo 7 in Annex). In this case, the compaction energy was

ignored only to achieve the wanted density. The samples at 2% turned out

to be brittle and difficult for testing. Their shearing results were

inconsistent. All the samples with over 4 % water content were

demonstrated to have consistent shearing values. The unconfined

compression test at 6% showed the highest compressive strength of 1.4

MPa. This value is what the NZ requires for non-stabilised rammed earth

constructions and can be used safely for a one-storey building.

Figure 5 : Compressive strength of equivalent dry density samples at different

water contents

0,5

1

1,5

0% 2% 4% 6% 8% 10% 12%

Co

mp

ress

ive

stre

ng

th [

MP

a]

Water content

10

The possible contributing factors as to why there is optimal water content

with the same porosity could be explained by unsaturated soil theory

briefly mentioned in 5.8.

5.5 Optimising soil structure with grain-size

distribution Soil used for rammed earth is most commonly a mixture of clayey silt,

sand and gravel. The evenly graded grain size creates more density in the

soil, filling in the gaps between the coarse particles with finer particles.

The assumption would be to approach the theory as one would with

concrete where a structural skeleton is achieved using gravel and sand.

Cementation then holds the grains in place.

The sand used for optimising the grain-size distribution of the soil is a

graded calibre used for concrete. Small sized gravel used for concrete was

also added to the mix. Taking into account the diameter of the samples

generally used, it was decided to avoid using a calibre greater than 5mm.

The optimal grain size distribution was achieved using the suggested

interval by CRATerre (CRATerre, Hubert, & Houben, 2006).

The soil soon appeared to lack a percentage of medium and large size

sand. This part of the curve was optimised accordingly by comparing 4

different mixes of soil and sand that were respectively: 40/60, 50/50,

60/40, 70/30. The amount of clay was thought to play an important part

in the cohesion of the soil, thus 50% of soil and 50% of sand was

considered the best compromise. The grain-size distribution was

extended by mixing small gravel with 50% of the original soil. 2 different

mixtures of soil/sand/gravel were made: respectively 50/25/25 and

50/37.5/12.5. Mixing the gravel did not seem to affect much the previous

shape of the curve after adding the sand and simply further extended the

grain size with the mixture of 50% soil, 25% sand and 25% gravel.

Figure 6 : Grain-size optimisation of MLD soil with sand and gravel

0

10

20

30

40

50

60

70

80

90

100

0,001 0,01 0,1 1 10 100

Re

tain

ed

pa

rtic

le f

ract

ion

(%

)

Grain size (mm)

100% MLD soil 30/70

40/60 50/50

60/40 50/25/25

50/37.5/12.5 Craterre optimal interval

IVIIIIII V

11

5.5.1 Optimum normal proctor

The optimum normal proctor was established for the well graded mixed

soil. At optimum proctor water content and dry density, the compressive

strength did not pass 0.27 MPa. Once again, the achieved dry density did

not reflect that of what is achieved on site. The standard geotechnical

testing procedures being put to question, a new testing setup was

undertaken.

5.6 Adapting the testing procedure At first the geotechnical tests were in fact not questioned and it was

thought to be grain structure the main problem. It was later understood

that the water content and compaction energy were other factors to be

considered. The way the laboratory testing and how the hypotheses were

raised are resumed in diagram in the annex.

5.6.1 Compaction energy

The compaction energy was increased by sequentially ramming the soil

mixture in layers with a 2.5kg proctor hammer directly inside the mould.

The compaction was achieved until the hammer bounced and no longer

seemed to affect the thickness of the layer. The dynamic compaction in

multiple layers was to mimic the same ramming process in-situ. The

proctor hammer would however impact the soil via a metal rod closely

fitting the mould, so the compaction process would be considered

confined as the soil did not have room for displacement.

A sample was taken at each water content in order to establish the

maximum density achieved with the proctor hammer in the mould, after

which the soil did not appear to compact further. The process was again

repeated at the given density for the final samples in 5 successive layers

at 6 different water contents (dried soil, 2%, 4%, 6%, 8%, 10%). The

samples at a theoretical 0% water content were unusable as the samples

became laminated and quickly dismantled at the limits of their compacted

layers.

5.6.2 Compressive strength of optimally mixed soil

The sample at a water content of 4% sheared at the highest stress value

of 2.4 MPa. However, its achieved dry density was 2198 kg/m3 yet lower

than the sample at 6% which was 2212 kg/m3 with a shear value of 1.4

MPa. This reinforces the assumption that water content is a greater factor

in the resistance of the material than soil density.

Figure 7 : Compressive strength of compacted mixed soil at different water

contents

1950

2000

2050

2100

2150

2200

2250

0

0,5

1

1,5

2

2,5

3

3,5

4

0 2 4 6 8 10 12 14

Dry

de

nsi

ty [

kg

/m3]

Co

mp

rssi

ve

str

en

gth

[M

Pa

]

Water content %Mixed max compaction Dry density mixed maximum compaction

12

The shear value of 2.4 MPa represents a very satisfying result for rammed

earth construction. The water content and the mixture are feasible and

fewer risks are taken when using well graded soil as theoretically it is less

prone to shrinkage. This will be the value used for the architectural

application in Part II of the Master Thesis.

5.7 Cohesion Another possible factor contributing to the strength of the material was

cohesion. It seemed from the previous results that high water content

could cause the material to be too plastic or low water content would

render the material brittle and less cohesive. The hypothesis that the

main contributor to cohesion was clay content had been raised. It was

assumed that the water content may be ideal for the clay platelets to be

partially submerged in water thus contributing to electro-statical forces in

the material.

It appeared inconvenient to add clay to the mixture (different clay type,

difficulty in mixing…), therefore samples using only the original soil were

made whilst taking into account the adjusted testing procedure. 5

different water content samples were set at 10%, 8%, 6%, 4% and 2%. At

maximum compaction energy and an ideal water content of 8%, the

sample sheared at a surprising 3.8 MPa.

This study questions the necessity of having a well graded soil as

suggested by CRATerre or by any scientific publication. The optimal

mixture and high density may not necessarily contribute to the strength

of the material but this may be for other reasons. Another important

factor to consider in earth construction is shrinkage. ThIS is discussed

further in the master thesis at 5.12.

Figure 8 : Compressive strength of compacted non-mixed MLD soil at different

water contents

5.8 Suction In reality, cohesion is not only made by clay particles. Doctorate Paul

Jacquin points out in his thesis (A.Jacquin, 2008) that the tensile strength

formed by liquid bridges contributes to strength developed in non-

stabilised rammed earth constructions. It was demonstrated by the

relation between suction and strength (Paul Jacquin, 2009). Geotechnical

testing does not take these phenomena into account.

1650

1750

1850

1950

2050

0

1

2

3

4

5

0 2 4 6 8 10 12 14

Dry

de

nsi

ty [

kg

/m3]

Co

mp

ress

ive

str

en

gth

[M

Pa

]

Water content %

Non mixed maximum compaction Dry density non-mixed maximum compaction

13

5.9 Hygrometry A certain amount of water content at a certain density is important for

the strength of the material. Also, it was shown that if the sample dries

further, its strength also increases in time. However, the water content

dealt with is rather low, thus raising the question that perhaps under a

given hygrometric state the rammed earth wall may on the contrary

absorb water, thus perhaps decreasing its strength.

In order to underlay this question, samples of same dry density with the

original soil (1740 kg/m3), at different water contents were put under a

specific hygrometric state. 2 samples of each water content (2%, 4%, 6%,

8%, 10%) were set at a controlled relative humidity of 94% (temperature

22°C) and at ambient relative humidity (+/- 43%, 22°C) in a non-occupied

room. These various levels of humidity were to reflect normal interior

conditions and outside rainy conditions. In order to achieve 94% relative

humidity, a saturated solution of potassium nitrate (KN03) filled the

bottom of a bell. The samples were all placed within the same bell on a

porous plate over the solution.

The goal was not to study the kinetics of absorption, but to test the

strength of the samples once they reached final equilibrium. The mass of

each sample was taken every few days in order to follow the fluctuations

and determine when they reached their final state. It was observed rather

quickly, all the samples converged to equilibrium. The specimens were

put through the standard pure compression test after 28 days to be sure

they met an equilibrium state.

Figure 9 : Variation of mass of water in soil samples over 28 days at ambient interior

relative humidity (+/- 40% RH, +/- 22°C)

Figure 10 : Variation of mass of water in soil samples over 28 days at controlled relative

humidity simulating rainy conditions (94% RH, 22°C)

-1

1

3

5

7

9

11

0 5 6 21 28

Wa

ter

con

ten

t v

ari

ati

on

(g

)

ΔW

C =

WC

1-W

Cn

Days

2% sample 1

2% sample 2

4% sample 1

4% sample 2

6% sample 1

6% sample 2

8% sample 1

8% sample 2

10% sample 1

10% sample 2

-5

-4

-3

-2

-1

0

1

2

3

0 3 21 28

Wa

ter

con

ten

t v

ari

ati

on

(g

) Δ

WC

=

WC

1-W

Cn

Days

10% sample 1

10% sample 2

8% sample 1

8% sample 2

6% sample 1

6% sample 2

4% sample 1

4% sample 2

2% sample 1

2% sample 2

14

It was revealed that at interior ambient relative humidity all samples

except those at 2% have dried out (Figure 9). As it had thought to be, the

compressive strength had increased. However, the samples at 8 and 10%

that were much less resistant at day 0 became the most resistant.

On the other hand, under relative humidity of 94% samples at 2% and 4%

had absorbed water (Figure 10). Under compression, they sheared at a

lesser value than Day 0. However, the sample at 6% which had seemed to

have a rather stable water content over time had gained in resistance.

Samples at 8% and 10% had lost water content and therefore gained in

strength.

Figure 11 : Compressive strength of compacted non-mixed MLD soil specimens

after 28 days at given relative humidity

In order to illustrate that the same process also occurs even for greater

dry density. The specimen of 8% water content of dry density 2180 kg/m3

was put under the same interior conditions (50% relative humidity) for 28

days. In fact, it also quickly reached equilibrium under a few days (Figure

13). The compressive strength had gone from 3.8MPa to 7 MPa (Figure

12). This is a great achievement for non-stabilised rammed earth.

Figure 12 : High compaction energy non-mixed MLD soil at 8% water content at

50% relative humidity during 28 days

Figure 13 : Compressive strength comparison of maximum dry density sample at 28 days

under ambient interior conditions

0

0,5

1

1,5

2

2,5

3

3,5

2% 4% 6% 8% 10%

Co

mp

ress

ive

str

en

gth

aft

er

28

da

ys

[MP

a]

Water content %

Day 0

50%

94%

2,05

2,1

2,15

2,2

05

-avr

.

07

-avr

.

09

-avr

.

11

-avr

.

13

-avr

.

15

-avr

.

17

-avr

.

19

-avr

.

21

-avr

.

23

-avr

.

25

-avr

.

27

-avr

.

29

-avr

.

01

-ma

i

Bu

lk d

en

sity

0

2

4

6

8

0,0

0

0,2

3

0,4

6

0,6

8

0,9

1

1,1

4

1,3

6

1,5

9

1,8

2

2,0

4

2,2

7

2,5

0

2,7

2

2,9

5

3,1

7

3,4

0

Str

ess

[M

Pa

]

Strain [mm]

Max compact

8% Day 0

Max compact

8% Day 28

ambient RH

15

5.10 Size of samples It was clear that the size of the samples were rather small compared to

standard compression concrete blocks. Australian codes have suggested

the size of the samples for rammed earth strength testing need to be

cylinders of 200mm in height and 110mm in diameter.

In this case, blocks of 150x150x150mm (see Photo 5) were made with the

ideal soil mixture, a dry density of 1996kg/m3 and optimal water content.

While using a 6kg hammer rather than a 2.5kg (see Photo 6), it was

quickly revealed with the first try that it became much easier to achieve

the dry density when ramming. Not only did the weight of the hammer

obviously play a role but also the soil had more room to move as only a

partial area was rammed. In this case, the aim was to be able to compare

only the size of the samples, thus the same dry density needed to be

carefully achieved.

In order to achieve the wanted dry density, the mass of soil was

calculated for the given volume. The formwork blocks where marked in

height every 3cm to control the compaction ratio of each layer. The

necessary amount of soil for each layer was then carefully compacted

until the given height was reached.

Qualitatively, the blocks seemed robust but slightly more fragile than the

smaller cylindrical samples. The sides were brittle and the corners were

more likely to break. It was difficult to achieve a planar surface but it was

presumed that the ductility of the material would contribute to making

the surface planar during the compression.

The compression test was performed on a press designed for concrete

thus dealing with at least a compressive strength of 10MPa. The first trial

was using a displacement far more superior than the displacement used

in the previous trials. The material quickly failed at 17 kN, which

translated to 0.76 MPa for the block. This is over 3 times less strong than

that achieved with smaller samples. It was predictable that the block

would shear at a lesser value due to imperfections but the difference was

far too significant. Some assumptions were raised: it could be that the

scale of the sample plays an essential factor, indeed the surface was far

too non-planar, the corners of the blocks did not contribute to the

strength of the material and/or the loading rate was too high. Generally,

for non-stabilised earth constructions, the corners of the walls are

bevelled. According to concrete experimentalists1, the change of

geometry between a cube and a cylinder changes empirically by a factor

of 1.26. A non-planar surface can also alter the results by an even greater

factor that makes them too erroneous to even take into consideration.

The loading rate in the previous tests took over 35 minutes before

shearing as to this test it took less than a minute.

It is impossible to demonstrate here if the scale of the sample does

indeed change significantly the compressive strength of the material. Of

course, the factor of slenderness of the sample surely contributes to a

change.

16

5.10.1 Increased size of cylindrical sample In order to be able to compare the previous results on the smaller

samples, all other factors had to remain constant. A larger cylindrical

sample was put to test. The geometry and height to diameter ratio of 2

were kept, thus not influencing the slenderness or form (see Table 4 and

Photo 2). The same loading rate was kept by using the same press in the

soil mechanics laboratory. The test was made with the mixed soil. The

samples were 51mm in diameter and 102mm in height. They were

compacted with a 6kg hammer via a round stem.

The suspected load to be achieved was slightly less by 6.7 %. This

difference could be accountable for more imperfections on the larger

contact surface and a slightly less dry density on average. In this case, the

maximum stress value reached was 2.23MPa for the mixed soil.

Size 1 Size 2

Height [mm] 72 103

Diameter [mm] 36 51

Ratio h/d 2 2,01960784

Area [mm²] 1017,87602 2042,82062

Volume [cm3] 73,2870734 210,410524

Table 4 : Dimensions of samples used for testing

5.10.2 Imperfections In order to illustrate the effect of imperfections on a rammed earth

sample under compression, a cylindrical specimen of size 2 (Table 4) was

made with non-parallel top and bottom surfaces. It could be seen slightly

by eye but was more distinguishable when put on the press. The results to

the stress developed had deviated by 68%. The resulting fractured sample

showed that less than half of the specimen had clearly fractured and was

submitted to most of the stresses in the material (see Photo 11 in Annex)..

5.11 Type of ramming During the whole testing procedure, a dynamic compaction with

distinguishable blows was used. Another mechanical procedure was

tested whilst using an electrical vibrating hammer used for concrete. In

order to test the efficiency of the ramming, a block of a well graded soil of

15x15x15cm was produced. While ramming manually with a hammer of

6kg via wooden piece in the mould, a dry density of 2150kg/m3 was

achieved. On the other hand, with the electric vibrating hammer, the soil

would not compact further to achieve more than 2080 kg/m3 in dry

density. CRATerre states that this type of ramming is not well adapted for

rammed earth (CRATerre, Hubert, & Houben, 2006).It is perhaps

preferred that ramming should be done by fewer concentred energy

blows rather than many lower energy blows.

5.12 Shrinkage This is an important aspect to earth constructions in general. Rammed

earth is slightly less subject to shrinkage than other techniques yet it is

crucial to the stability of a wall. CRATerre suggests that if there is

17

shrinkage of 1mm over 1m of rammed earth then some problems will

naturally occur (CRATerre, Hubert, & Houben, 2006).

The shrinkage of the material is known to be caused mostly by clay

platelets. The soil mix at 4% water content is not expected to be subject

to much shrinkage. It can be pointed out for the non-mixed soil, the

shrinkage limit had been determined with the geotechnical procedure.

Knowing that its optimal water content for greatest resistance is at 8%,

the shrinkage limit occurs in fact at 15% water content. This suggests that

the soil no longer varies in volume under this value. It’s not yet clear

whether it is the case when the soil density is high but it does suggest that

perhaps the original soil could be used for a rammed earth project.

However, a test at the scale of construction should be considered before

validating this data and this type of testing for rammed earth

constructions.

18

Part Two : Application to Urban Co-Housing in Brussels

22

The aim is to drive the attention of the public to earth buildings and

demonstrate usage of earth as a potential construction material even in

temperate climates such as in Belgium.

It is essential to understand the characteristics of the material and keep

them in mind throughout the whole design process of a rammed earth

building. In this case, we are essentially dealing with all the characteristics

of non-stabilised rammed earth and implementing them into a feasible

urban co-housing project.

1 Identified technical characteristics The project’s technical constraints are more of a necessity in order to take

advantage of the characteristics of the material rather than some fixed

limits. Surely the compressive strength will be a factor to the limitation in

height of the project or the loadings that it can withstand but the

technicality of the material will determine the expression of the building.

In this case, the material becomes the essence of the project and

therefore an elaborate understanding and control of rammed earth

constructions needs to be the tool to any architectural application. There

is no linear process to architecture, so these characteristic determinations

are a small mindset to the context and program of the project (see Figure

14). It is crucial for any architect to consider these aspects if they are

willing to exploit all the advantages of non-stabilised rammed earth

constructions as well as creating a durable and long lasting project.

These were the characteristics that were primarily considered :

− Structure

o Rammed earth is the structure and skeleton of the building

− Expression and identification

o Users and public should perceive the material outside and

inside the building

− Need of insulation

o An added insulating envelope is needed to answer passive

house standards

− Hygrometry

o The internal surface of a rammed earth wall should be in

contact with the air inside the building.

− Protection

o In temperate climates, it is preferred to have protection

against direct contact to rain

− Thermal mass

o Rammed earth walls should be inside the building

Figure 14 : Scheme of characteristic implementation of rammed earth to

architecture

Protection

Exterior expression

Insulating envelope

Interior expression

1.1It can be i

Interior

Thermal mass and hygrometric

properties are lost but the structure

appears on the outside.

Exterior


properties are kept yet the structure

does not appear.

Middle

This te

material is expressed on both sides, part

of the thermal mass and hygrometric

regulation is exploited. It may seem to be

the best solution, however, the

technique implies that the insulation can never be changed without the

destruction of the walls. Another characterisation of a rammed earth can

be that dismantling or changing part of the building is easily implemented

without a destructive procedure or environmental impacts. Also, the

insulation is directly in contact with

lose their quality and performance when in contact with a moist

environment. Furthermore, the wall is no longer acting as a whole but as

1.1 InsulationIt can be implemented in 3 differents ways to a façade.

Interior




Exterior



does not appear.

Middle

This technique is used by Sirewall. The












Insulation mplemented in 3 differents ways to a façade.






chnique is used by Sirewall. The












mplemented in 3 differents ways to a façade.





chnique is used by Sirewall. The









insulation is directly in contact with the soil. Most insulating materials



Inside

Inside

Inside

mplemented in 3 differents ways to a façade.





the soil. Most insulating materials



Outside

Outside

Outside





the soil. Most insulating materials



two separate parts. Sirewall stabilises their walls with up to 20% of

cement thus

for the non

solution will be abandoned.

2 The co

RE constructions as it is already dealing with a community that is generally

concerned with their way of living and their environment. The scale of the

project also stays residential. It is less common for an urban project to be

developed with this type

program should lay within the conce

This way of living is becoming a new wave in modern society. A group of

individuals and families who live in their respective homes are brough

together by sharing spaces and tasks. The group of residents develop a

sense of community by co

choice of living are various seen as multiple aspects convey advantages

that may not

inhabitants are motivated by seeking a greater social experience. Some of

the operatives in a dwelling are shared thus creating a sense of

community and mutual support. Financial advantages can be found where

sharing part of the s

Furthermore

carpooling, reducing costs in maintenance tools (lawnmower, working

tools, etc…)

services between each other. In some co

Outside

Outside

Outside


cement thus increasing the resistance and dealing with thinner walls. As

for the non-stabilised rammed earth project in this master thesis, this


Co-Operative housingThe co-operative housing program is essentially interesting in the case o




developed with this type

program should lay within the conce




sense of community by co


that may not be found in traditional privat




sharing part of the s

Furthermore, smaller financial benefits can


tools, etc…), sharing meals



increasing the resistance and dealing with thinner walls. As

stabilised rammed earth project in this master thesis, this


Operative housing operative housing program is essentially interesting in the case o




developed with this type of program and therefore the strategy of the

program should lay within the concept of densifying the urban area.




sense of community by co-operating as a whole. The motives for this


found in traditional privat




sharing part of the site contribute to a greater sentiment of ownership.

, smaller financial benefits can


, sharing meals. Others may see the benefits of exchanging





operative housing program is essentially interesting in the case o




of program and therefore the strategy of the

pt of densifying the urban area.




operating as a whole. The motives for this


found in traditional private housing. In some cases,




ite contribute to a greater sentiment of ownership.

, smaller financial benefits can also be developed by


. Others may see the benefits of exchanging

services between each other. In some co-housing communities, people

23




operative housing program is essentially interesting in the case o





pt of densifying the urban area.






e housing. In some cases,





also be developed by



housing communities, people

23




operative housing program is essentially interesting in the case of






individuals and families who live in their respective homes are brought




e housing. In some cases,





also be developed by



housing communities, people

24

are grouped together because they already share a common way of life

(retirement, spiritual thinkers, environmentalists, etc…).

2.1 Multigenerational bartering A unique feature that can be found while deliberately mixing age groups

in a co-housing community is the exchange of services. For example, an

old age group whom are retired can use their spare time to look after

children of working parents. In exchange, a younger generation may help

and perform chores that an elder may no longer be able to achieve so

easily such as grocery shopping, driving or home maintenance. This may

reduce costs for social helpers and provide a sense of belonging for the

elder who tend to be dissociated from the rest of society.

2.2 Multiple sociological backgrounds All the operatives are distributed according to what one another can

provide. Some may indeed be retired or temporarily unemployed and

could spare time and notion for the maintenance and development of the

building. Working class people may have technical qualifications that

could contribute in that sense or others may indeed have a greater

income yet less spare time to spare and could therefore perhaps

contribute with an extra income for maintenance, tools or enhancement.

It may be utopic at a greater scale of sociability. However this can be

easily implemented within a small community of co-housers.

2.3 Participatory building A very unique feature of earth constructions is the simplicity of how it’s

achieved. During the participation on site of a rammed earth project in

Flanders, Belgium, the whole construction was made by mostly non-

qualified people, as for this reason it is often considered as DIY

construction. The only technical part played essentially in the formwork,

thus needing a supervisor to ensure its quality and reliability.

Due to the laborious aspect, yet very simplistic and comfortable way of

building with earth, it can be considered the possibility for future

inhabitants to participate themselves in the construction process. This

could not only accelerate and reduce the costs of labour but it also

constitutes a preliminary relationship with their new home. Another value

is accorded to the building where the inhabitants can relate to it as part of

their own work.

In the case of co-operative housing or so called co-housing, the future

inhabitants can also create a sense of community before actually living in

their homes. This is completely unique to earth constructions, at the

opposite to timber frames where connections and placements are crucial

or to concrete constructions which demands great care, detail and

qualifications.

Furthermore, the material is pleasant to work with. During the two week

participation on the rammed earth construction site, hands were

constantly plunged into the slightly moist and fresh soil. On the other

hand, the few days concrete had to be used on site (footings and lintels),

it became lot less enjoyable due to the unpleasant smell, the sensation of

dry skin, inhalation of cement dust, the use of unpleasant machines such

as a concrete vibrator ( and finally the maintenance of machinery.

25

3 Tour et Taxi The masterplan is not the main concern in this study, however the

feasibility of the project must be made by considering context and should

take into account the potential evolution of this site. This is why different

existing masterplans (Modus Expert, Citec, Bas Smets, 2008) made by

architects and students were taken into account rather than starting over

on the research which could be a whole master thesis to itself due to its

complexity.

There are two main reasons for choosing Tour et Taxi as the site for a

rammed earth project. Firstly, it is a growing part of Brussels that is

gaining more and more attention by the younger public. This is an

advantage for displaying a rammed earth construction and getting people

to know more about it in the future. It also corresponds well with the

idealistic way of living such as co-housing seen as the site itself is

surrounded by residents yet is also becoming quite culturally oriented.

Secondly, it is a vast terrain that covers a large surface in the middle of an

urban setting. If the project was to be developed with local soil, it would

be a great achievement to have the whole process done in-situ. This

requires a large area and space that is offered in Tour et Taxi. It was made

sure that the sites soil was viable for earth construction. Its layers were

studied via soil coring that had been effectuated by the soil mechanic

laboratory in the past. Under a 2 metre layer of embankment, there is

clayey silt which was the type of soil studied in the first part of the master

thesis.

Figure 15 : Google Earth view on Tour et Taxi, Brussels Local soil

3.1Geotechnical map 31.3.5 dating 1977 from the soil mechanics laboratory

of ULB shows many penetration tests on the site of Tour et Taxi. There are

two

types. Overall, e

between 0 and 4m, silt between 0 and 10m and finally alluvial sand and

gravel between 2 and 6m. It was not feasible to test the soil on the site

but it was considered that the clayey silt used for testin

common in Belgium and an analogical type could be easily found in the

alluvial clays

Figure

laboratory

3.1 Local soilGeotechnical map 31.3.5 dating 1977 from the soil mechanics laboratory


two zones to which the side is divided that define two different lay

types. Overall, embankments vary





alluvial clays or silt

Figure 16 : Penetration test point N°794 Tour et Taxi, Brussels,

laboratory

Local soil Geotechnical map 31.3.5 dating 1977 from the soil mechanics laboratory


zones to which the side is divided that define two different lay

mbankments vary in depth





or silt of Tour et Taxi (see

: Penetration test point N°794 Tour et Taxi, Brussels,

Geotechnical map 31.3.5 dating 1977 from the soil mechanics laboratory


zones to which the side is divided that define two different lay

in depth from 2 to 4m, alluvial clay





of Tour et Taxi (see Figure 16).

: Penetration test point N°794 Tour et Taxi, Brussels,



zones to which the side is divided that define two different layer

from 2 to 4m, alluvial clay



but it was considered that the clayey silt used for testing is rather


: Penetration test point N°794 Tour et Taxi, Brussels, ULB soil mechanics



er

from 2 to 4m, alluvial clay




4

4.1Most masterplans suggested residences in the south

site. After comparing and understanding how these masterplans were

developed, it was finally taken into consideration only t

parcel. It was viewed as a part that would shape the rest of the site into

something perhaps clearer. The issue was to relate the existing hanger

with the residential urban tissue

proposed rows of residenti

through the site and transits into the urban tissue. These rows of separate

blocks communicate with the long existing building to the south yet

create transparencies through the site and relate to some exte

“îlots” or “island” Brussel typology on the North side. It was wanted that

the rammed earth buildings would be seen via the big agora, that its

function is fully residential and so it was decided that the north row would

be the place of implant

there was an urge for the project to extend on the whole row, yet a co

housing community can become difficult when exceeding 30 or 40

dwellings. It was decided that multiple co

implemented in the same row.

A co

housing

extends the possibilities and r

communities ca

services that they can provide.

Concept and Develop

4.1 Context Most masterplans suggested residences in the south





with the residential urban tissue

proposed rows of residenti







be the place of implant




lemented in the same row.

A co-housing community is beneficial for each inhabitan

housing communities can be beneficial for every

extends the possibilities and r

communities can be beneficial for the rest of the neighbourhood via


Concept and Development

Most masterplans suggested residences in the south





with the residential urban tissue on the north side

proposed rows of residential and office buildings that redraw a circulation







be the place of implantation for a co




lemented in the same row.

housing community is beneficial for each inhabitan

communities can be beneficial for every

extends the possibilities and relationships. Furthermore, this group

n be beneficial for the rest of the neighbourhood via


ment

Most masterplans suggested residences in the south-west corner of the





on the north side. Some masterplans

al and office buildings that redraw a circulation







ation for a co-housing community. Furthermore,



dwellings. It was decided that multiple co-housing communities would be

housing community is beneficial for each inhabitan

communities can be beneficial for every individual

elationships. Furthermore, this group


26

west corner of the


developed, it was finally taken into consideration only the south-west



. Some masterplans




create transparencies through the site and relate to some extent with the




housing community. Furthermore,



housing communities would be

housing community is beneficial for each inhabitant. A group of co

individual group as it

elationships. Furthermore, this group


26

west corner of the


west



. Some masterplans




nt with the




housing community. Furthermore,

there was an urge for the project to extend on the whole row, yet a co-


housing communities would be

co-

group as it

of


27

The blocks are all interconnected via a more intimate green promenade

on the north side and via the strong public circulation axis on the south

side. Also, the communities have the possibility to organise meeting

altogether or proceed in an exchange monthly or yearly.

4.2 Preliminary approach There was a first intention for people to be able to common exterior and

interior spaces. However, it is important for individuals to sometimes

evade and have their own intimacy. A private home and private terrace or

garden was the first wish to be implemented whilst having a common

circulation and space. This led to the idea of a stacked boxed shaped

structure that could be moved and shaped according to sunlight and

context.

Once building volume and it’s structure was more or less defined, the

walls had to be pre-dimensioned as they would clearly have

consequences on the spatial organisation of the project. The total surface

needed was calculated for approximately 25 units. Apartments were given

different areas accordingly to whether it was for a large family (4-3

bedroom), a small family (2 bedroom), for a couple or for a single person

(1 room).

4.3 Orientation and Sunlight The orientation of the row of buildings does not allow the sun to

penetrate directly into a whole façade. It was necessary for preliminary

analysis on how the sunlight could be optimised in a single building block.

The boxed structure was still kept in mind and could be optimised in order

to maximise sunlight.

28

Photo 1 : Context scale model of Tour et Taxi, Brussels

29

4.4 Internal Walls The structure was preferred to have the least contact with any other

construction layer as possible in order to conserve all the hygrometric

properties as possible. Also, due to passive house standards, even a 90cm

earth wall could not provide the sufficient thermal resistance (Part one,

2.4), therefore it was clear that insulation was going to be needed. Other

aspects such as protection from erosion and taking the advantage of

thermal inertia had to be considered. This is where it was considered is

greater advantage to keeping the walls internal.

A skeleton was defined with straight lines. The idea of having linear walls

was to simplify the construction process and the formwork needed.

Nearly all the walls were decided to be transversal to the façade, thus

keeping them inside in order to maximise all the benefits of this type of

construction material. However, they were ever so inslightly inclided in

order to take into account the direction of the sun, the shadow upon the

other buildings and the intimacy in the apartments.

An extra thermal insulation could come around and protect the walls. On

the other hand, the structure could let the walls show the material on the

outside in order to attract attention to the material by passer byers. All of

the walls were simply further extended thus giving an interesting

perspective and showing the material.

To improve the privacy of the inhabitants, all floors are set higher than

the circulation spaces including bottom ground. Ground floor apartments

have higher ceilings for more light penetration

Distribution to the apartments is done via an internal footbridge. In front

of all vertical circulation, a large free space is given to encourage social

interaction.

30

Drawing 1 : Site implantation 1/ 500

31

5 Predimensioning

5.1 Load calculations All calculations were based on the Eurocode. However, the approach was

clearly simplified as it was only to give estimation to what the wall

dimensions would be for the design case if we wanted to achieve a 4

storey building.

5.1.1 Floor loads

A maximum span of 5m was considered between each wall. The flooring

was to be of wooden beams and finishing.

The considered loads for the building are showed in table 4.

Permanent Loads Span [m] Load [kN/m²] Repetition

Wood flooring 5 2,5 3

Partitions 5 0,5 3

Roof 5 1,5 1 Table 5 : Permanent loads used for pre-dimensioning wall thickness

Variable Loads Span [m] Load [kN/m²] Repetition

Dwelling 5 2 3

Maintenance/Snow 5 0,5 1 Table 6 : Variable loads used for pre-dimensioning wall thickness

5.1.2 Self-weight

The self-weight of a rammed earth wall was taken as 2290kg/m3

considering a 2200kg/m3 dry density and 4% water content of the soil

used.

A 4 storey building was presumed to be 14 metres high. The rammed

earth wall would be 13 metres high if we subtract 1m of footing. A 70cm

wall thickness was considered and thus its self-weight was 275 kN/m.

5.1.3 Combination of permanent and variable actions

Permanent and variable loads were multiplied by their respective partial

coefficients. NEd = 1.35g + 1.5q

The total load NEd was equal to 400 kN/m. It is interesting to point out

that nearly 93% of the achieved loading is the self-weight of the wall.

5.2 Resistance to vertical loads The compressive resistance of 2.4 MPa that was achieved with the mixed

soil during laboratory testing defined in Part One was chosen as the

design value. The calculated resistance for a 70cm thick wall turned out to

be :

NRd = 1680/ ϒM = 420 MPa thus NRd > NEd

A 70cm wall thickness is a satisfying design value, however there are

some other factors to be considered when realistically dimensioning the

walls such as the height and slenderness of the wall.

5.2.1 Security factor

The security factor on the material was taken as ϒM = 4. The highest

security factor given for fired earth bricks is 3.0 to 3.5. The arbitrary value

of 4 seems to be a reasonable coefficient and can be accountable for the

fact that there is still, as of today, very little control over the material and

many factors could contribute to decreasing the resistance. On the other

hand, unlike fired earth bricks, in the case of rammed earth constructions,

its

If the rammed earth project was designed with

developed a compressive strength of 3.8 MPa

the security factor could go up to 6.

There are some negative effects with in

quality over the soil, the possible change of water content in function of

outside relative humidity (especially in rainy conditions), the quality of

compaction and some possible eccentricities or loss of uniform repartition

of stresses in the mat

1,

increasing its performance.

into acc

durability.

5.2.2Due to overhangs and depression on slanted roof

for uplifting to occur. Tension is unfavourable for a rammed earth wall

and in fact its

resume tension through the second façades or it is possible to post

tension a rammed earth wall

It is very unlikely that the project needs this kind o

structure and the exterior passage way work together as a whole via

metal rods.


its resistance will incre








of stresses in the mat

1, 2.2 that rammed earth is most likely to dry to a certain extent and thus

increasing its performance.

into account in the design, it does prove a positive effect on the

durability.

5.2.2 Vertical lifting loadsDue to overhangs and depression on slanted roof


and in fact its tensile strength could be considered null. It is possible to


tension a rammed earth wall



metal rods.


resistance will increase in time.








of stresses in the material. Nevertheless, it has been demonstrated in Part

that rammed earth is most likely to dry to a certain extent and thus

increasing its performance. Even if this should not necessarily be taken

ount in the design, it does prove a positive effect on the

Vertical lifting loads Due to overhangs and depression on slanted roof


tensile strength could be considered null. It is possible to


tension a rammed earth wall (Ward, 2006)




If the rammed earth project was designed with the original soil that

developed a compressive strength of 3.8 MPa demonstrated in Part One


There are some negative effects with in-situ ramming such




erial. Nevertheless, it has been demonstrated in Part


Even if this should not necessarily be taken


Due to overhangs and depression on slanted roofs, there is the possibility




(Ward, 2006).

It is very unlikely that the project needs this kind of technology. The roof



original soil that

demonstrated in Part One

situ ramming such as: control of








, there is the possibility




f technology. The roof



demonstrated in Part One,

ntrol of








, there is the possibility




f technology. The roof


5.3During the building process, the walls will be subject to wind. This should

be taken into account especially in thi

and stand alone. It is only when they receive a concrete/bentonite

chaining on each level and that they are secured altogether with the

wooden flooring could we consider the wind will no longer be a

stability

The resist

resultant was calculated

Where e is the equivalent eccentricity of the applied load and is given by :

e = M

selfweight and L the height of the wall.

l/6 is the value taken for retaining structures. This is discussed further.

A wind load

variable actions 1.5 and a reduction factor of 80% was app

urban situation

5.3 Resistance to horizontal loads (Wind)During the building process, the walls will be subject to wind. This should

be taken into account especially in thi




stability.

The resistance to wind was calculated in analogy to a



M / V = H.L / V < l/6 where I is the wall thickness, V is this cas



wind load of 0.4kN/m


urban situation. The results were the following :

Resistance to horizontal loads (Wind)During the building process, the walls will be subject to wind. This should

be taken into account especially in this case where the walls are individual




ance to wind was calculated in analogy to a



< l/6 where I is the wall thickness, V is this cas



of 0.4kN/m2 was taken. It was multiplied by the coefficient of


The results were the following :

Resistance to horizontal loads (Wind)During the building process, the walls will be subject to wind. This should

s case where the walls are individual




ance to wind was calculated in analogy to a


< l/6 where I is the wall thickness, V is this cas



t was multiplied by the coefficient of


The results were the following :

32

Resistance to horizontal loads (Wind) During the building process, the walls will be subject to wind. This should




wooden flooring could we consider the wind will no longer be a factor of

retaining wall. The


< l/6 where I is the wall thickness, V is this case the



variable actions 1.5 and a reduction factor of 80% was applied due to an

32

During the building process, the walls will be subject to wind. This should




factor of

The


e the


lied due to an

33

H 6,72 [kN]

V 275 [kN]

L 13 [m]

e 0,31767273 [m]

l/6 0,11666667 [m]

It has been demonstrated that e > l/6. This suggests the wall would be

rather unstable to wind. However, the resultant still remains within the

wall. l/6 is for long term retaining structures and in fact may not be

necessary for a short term construction process. Also, the period that the

construction would take place is most likely to be during summer when

there is less wind (NASA, 2001). However, to reduce the risks of the wall

collapsing, struts would have to be placed on the wall during the

construction process. In the case, we took e < l/6, they would have to be

placed up to 8 metres high for a 13 metre wall.

6 Sustainability

6.1 Construction materials As it was discussed in part 1, the environmental advantages and the

material properties of rammed earth contribute to the sustainable

aspects of the building. Also, very little concrete is used and is only

exploited to achieve lintels and support the terraces and circulation area.

Furthermore, the second material most used is wood which was taken for

the floors. The type of insulation included is cork. All these materials are

of low embodied energy and have a low environmental footprint.

6.2 Net zero energy building Even if the thermal transmittance is high for rammed earth, a 70cm still

insulates quite significantly. By adding 10cm of with all the detailing of

insulation taken into account, the energy performance of the building is

high. The large area of solar panels contributes to easily achieving NZEB

standards.

6.3 Green roofs A large area of green roofs is provided thus contributing to improving the

quality of the urban atmosphere

6.4 Solar panels The slanted roofs were designed to be oriented towards the south. A

considerable amount of energy can be provided by the large surface of

solar panels that are in optimal position.

6.5 Aquaponic systems The energy produced could contribute to aquaponic systems in the

basement. The systems can provide food all year round.

6.6 Water harvesting system The slanted roofs were also designed to control the rainflow and be able

to harvest water that will be stored in the basement. The stored rainwater

can be reused in many ways including watering green roofs and plants,

washing clothes and flushing toilets.

31

Water harvesting roof design

Southern oriented solar panels

Underground aquaponic systems

Green roofs

Drawing 2 : Sustainability scheme

32

Drawing 3 : Ground floor 1/200

33

Drawing 4 : Second floor 1/200

34

Drawing 5 : Third floor 1/200

35

Drawing 6 : Fourth floor 1/200

36

Section AA’

(Night and Day)

1/200

Drawing 7: Section AA'

37

Section BB’

1/200

Drawing 8 : Section BB'

38

Section CC’

1/200

Drawing 9 : Section CC'

39

Insulation detailing

15mm for 1m

Drawing 10 : Second floor plan insulation

40

Drawing 11 : Render 1

41

Drawing 12 : Render 2

42

Drawing 13 : Render concept colour

43

ANNEX

1. Identification paper for MLD soil used in tests

Table 8: Characteristics and identification table of MLD soil used for testing

Soil classification Plasticity

index

Grain-size distribution criteria

Clay Ip > 25 No criterion

Sandy clay 15 < Ip < 25 III+IV+V > 50%

Silty clay 15 < Ip < 25 III+IV+V < 50% and II < 50%

Silt 15 < Ip < 25 III+IV+V < 50% and II > 50%

5 < Ip < 15 III+IV+V < 50%

Clayey sand 5 < Ip < 15 III+IV+V > 50% and I > IIa*

Silty sand 5 < Ip < 15 III+IV+V > 50% and I < IIa*

Sand with a few clay 5 < Ip < 15 I > IIa*

Sand with a few silt Ip < 5 I > IIa*

Fine sand Ip < 5 III > 50%

Medium sand III+IV > 50% and IV < 50%

Coarse sand IV > 50%

Fine gravel V > 50%

Medium and coarse gravel VI > 50%

Soil MLD

Origin Marche-Les-Dames,

Belgium

Shrinkage limit 17.4%

Plastic limit 22%

Liquid limit 33.44%

Plasticity Index (Ip) 13.24

Clay proportion I 13%

Silt proportion II 58%

ABEM classification Silt / Silty Clay

Table 9 : ABEM/BVSM soil classification (François, 2011)

0

10

20

30

40

50

60

70

80

90

100

0,001 0,01 0,1 1 10 100

Re

tain

ed

pa

rtic

le f

ract

ion

(%

)Grain size (mm)

IVIIIIII V

Table 7 : Grain-size distribution curve of MLD soil

*IIa corresponds to the fine silt fraction (from 0.002mm to 0.02mm)

Drawing 14 : Render 4 passageway

Figure 17 : Diagram summarising stages of research: Diagram summarising stages of research: Diagram summarising stages of research

44

44

45

.

Photo 2: Unconfined compression and comparison of size 1 and size 2 samples

Photo 3 : Unconfined compression for small size samples

Photo 4: Some sheared samples

46

Photo 6 : Ramming 15cm block with 6kg hammer via a wooden piece Photo 5 : Rammed Earth Block 15cm well graded soil

47

Photo 8 : Diagonal and cone shearing Photo 7: Laminated sample due to high compaction energy and low water

content

48

Photo 10 : Bell for controlled relative humidity Photo 9 : Preparation of soil dried at approximately 35°C

49

Photo 11: Sheared sample with non-parallel surfaces

50

2. Rammed Earth Workshop April 2012 : Construction of 50m² hunting house (by BC-as)

33

Bibliographie

A.Jacquin, P. (2008). Analysis of Historic Rammed. Durham: Durham University.

Arjen Y. Hoekstra, M. M. (2012). Global Monthly Water Scarcity: Blue Water

Footprints versus Blue Water Availability.

Burroughs, S. (2008). Soil Property Criteria for Rammed Earth Stabilization. ASCE.

C. M. Gerrard, P. A. (2006). Analysis of Historic Rammed Earth construction. New

Delhi.

Clare Lax, P. W. (2010). Life cycle assessment of rammed earth. Bath: Bath

University.

CRATerre, Hubert, G., & Houben, H. (2006). Traité de construction en terre.

Grenoble: Parenthéses.

Debra F. Pflughoeft-Hassett, B. A. (2000). Use of bottom ash and fly ash in

Rammed-Earth Construction. Grand Forks,: University of North Dakota.

Descamps, F. (2012). Advanced Building Physics Course Notes. Brussels: VUB.

Earth Structures (Europe). (2013). Retrieved from

http://www.earthstructures.co.uk/:

http://www.earthstructures.co.uk/SREregcompliance.pdf

EnviroNomix. (2009). Cork insulation. Retrieved from http://www.cork-

insulation.com/.

François, B. (2011). Soil Mechanics Course Notes. Brussels.

Jacquin, P. (2007). Study of historic rammed earth structures. Durham: Durham

University.

Modus Expert, Citec, Bas Smets. (2008). Hefboomgebied n°5 «Thurn en Taxis»

Richtschema. Brussels.

NASA. (2001, October). Global Wind Speed. Retrieved from

www.earthobservatory.nasa.gov:

http://earthobservatory.nasa.gov/IOTD/view.php?id=1824

Oss, H. G. (2011, January). Retrieved from http://minerals.usgs.gov/:

http://minerals.usgs.gov/minerals/pubs/commodity/cement/mcs-2011-

cemen.pdf

Paul Jacquin, C. E. (2009). The strength of unstabilised rammed earth materials.

Scientific publication.

Prof.Geoff Hammond, C. J. (2008). Inventory of carbon and energy (ICE). Bath:

University of Bath.

Rauch, M. (n.d.). Retrieved from lehmtonerde: http://www.lehmtonerde.at/en/

Stuart Fix, R. R. (n.d.). Viability of Rammed Earth Building in Cold Climates.

Vasilios Maniatidis, P. W. (2003). A Review of Rammed Earth Construction. Bath:

University of Bath.

Verbrugge, J. C. (2010). Mécanique des sols. Brussels: P.U.B.

Ward, T. (2006). Patent No. US 7, 033, 166 B1. United States.

34

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