Non-Stabilised Rammed Earth Constructions
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Transcript of 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
Alexandre Robert McCormack
Supervisor :
Bertrand François
Université libre de Bruxelles
Vrije Universiteit Brussel
of architectural and civil engineering
Brussels May 2013
Alexandre Robert McCormack
Bertrand François
Université libre de Bruxelles
Vrije Universiteit Brussel
of architectural and civil engineering
Brussels May 2013
of architectural and civil engineering
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
designing sustainable architecture.
materials is still rarely taken into account
to consider. The energy used to process the material impacts on the
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 Concrete and Steel
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.
Environmental advantages
ent of Rammed Earth
Embodied Energy lifecycle assessment of a building is of the utmost concern when
designing sustainable architecture.
materials is still rarely taken into account
sider. The energy used to process the material impacts on the
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.
Concrete and Steel
According to the so called “process analysis
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-modulus of the material. If a mater
enormous strength, less is required when it comes to designing the
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
sider. The energy used to process the material impacts on the
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 embodied energy of rammed
earth with that of concrete and steel, generally the default building
process analysis” for defining embodied
energy in materials, it can be demonstrated that concrete requires
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 energy as it takes into account all of
the elements required for the processing of the material itself. Obviously,
to properly compare the materials, we must take into account the ratio of
modulus of the material. If a mater
enormous strength, less is required when it comes to designing the
lifecycle
of a building is of the utmost concern when
mbodied energy in construction
remains an important aspect
sider. The energy used to process the material impacts on the
environment and directly or indirectly causes CO2 emissions. This needs
to be factored in if high energy material is necessary for all structural
died energy of rammed
earth with that of concrete and steel, generally the default building
” for defining embodied
that concrete requires
1GJ/m3. The same procedure for steel gives 23GJ/m3. However,
considering the Crawford (2011) procedure, concrete requires 5.01GJ/m3
and steel 85.46 GJ/m3. The Crawford (2011) is a much more precise
energy as it takes into account all of
the elements required for the processing of the material itself. Obviously,
to properly compare the materials, we must take into account the ratio of
modulus of the material. If a material has
enormous strength, less is required when it comes to designing the
of a building is of the utmost concern when
mbodied energy in construction
remains an important aspect
sider. The energy used to process the material impacts on the
environment and directly or indirectly causes CO2 emissions. This needs
to be factored in if high energy material is necessary for all structural
died energy of rammed
earth with that of concrete and steel, generally the default building
” for defining embodied
that concrete requires
1GJ/m3. The same procedure for steel gives 23GJ/m3. However,
GJ/m3
and steel 85.46 GJ/m3. The Crawford (2011) is a much more precise
energy as it takes into account all of
the elements required for the processing of the material itself. Obviously,
to properly compare the materials, we must take into account the ratio of
ial has
enormous strength, less is required when it comes to designing the
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
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 to quantify the amount of fuel required for the implementation
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-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
(Prof.Geoff Hammond, 2008)
0
5
10
15
Em
bo
die
d E
ne
rgy
GJ/
m3
Rammed Earth
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
to quantify the amount of fuel required for the implementation
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 the total embodied energy used.
of the soil was carried out by an excavator, the soil was mixed with an
earth mixer and sand and gravel had to be transported to the site, but
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
(Prof.Geoff Hammond, 2008)
Construction materials
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
to quantify the amount of fuel required for the implementation
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 required. However, this is
the total embodied energy used.
excavator, the soil was mixed with an
earth mixer and sand and gravel had to be transported to the site, but
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
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
to quantify the amount of fuel required for the implementation
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
ed. However, this is
the total embodied energy used. The excavation
excavator, the soil was mixed with an
earth mixer and sand and gravel had to be transported to the site, but
for mixing and carrying. Nevertheless, even if we
estimate each of these components, the total energy used is
. With more precise calculations, it is
s an embodied energy of
compared to the
construction materials
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
to quantify the amount of fuel required for the implementation
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
ed. However, this is
The excavation
excavator, the soil was mixed with an
earth mixer and sand and gravel had to be transported to the site, but
for mixing and carrying. Nevertheless, even if we
energy used is
. With more precise calculations, it 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.
It should be pointed out that the embodied energy for steel or other
metals is disproportional when compared to other materials. H
the E-Module of steel is consider
quantity of steel used. It is for this reason that in order to compare
realistically the embodied energy of materials,
should be taken into consideration
rammed earth walls are twice or three times (sometimes more) thicker
than concrete walls.
1.1.3 Embodied energy compared toAccording to ULB PhD student André
passive house represents 18.2% of the in
materials (see figure 2
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). This clearly demonstrates the importance of insulating a
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.
It should be pointed out that the embodied energy for steel or other
metals is disproportional when compared to other materials. H
of steel is considerably high, thus reducing the sections and
quantity of steel used. It is for this reason that in order to compare
realistically the embodied energy of materials,
be taken into consideration
rammed earth walls are twice or three times (sometimes more) thicker
than concrete walls.
Embodied energy compared toAccording to ULB PhD student André
passive house represents 18.2% of the in
see figure 2) and 7.2% over 100 years if one considers the
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 concrete structure represents only 3.7% of the total energy
. This clearly demonstrates the importance of insulating a
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 there are other variables that establish the
environmental footprint of a material.
It should be pointed out that the embodied energy for steel or other
metals is disproportional when compared to other materials. H
ably high, thus reducing the sections and
quantity of steel used. It is for this reason that in order to compare
realistically the embodied energy of materials, the sections generally used
be taken into consideration. For example, It could be argued
rammed earth walls are twice or three times (sometimes more) thicker
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
eventual replacement of some of these. However, taking into account the
consumption of the building over 100 years, the energy used in the
rete structure represents only 3.7% of the total energy
. This clearly demonstrates the importance of insulating a
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
ere are other variables that establish the
environmental footprint of a material.
It should be pointed out that the embodied energy for steel or other
metals is disproportional when compared to other materials. However,
ably high, thus reducing the sections and
quantity of steel used. It is for this reason that in order to compare
the sections generally used
It could be argued
rammed earth walls are twice or three times (sometimes more) thicker
the total building tephan, a concrete structure of a
itial embodied energy of all
and 7.2% over 100 years if one considers the
eventual replacement of some of these. However, taking into account the
consumption of the building over 100 years, the energy used in the
rete structure represents only 3.7% of the total energy
. This clearly demonstrates the importance of insulating a
building above all other aspects. However, if we look at the accumulation
of this percentage over a large number of dwellings, the energy then
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
ere are other variables that establish the
It should be pointed out that the embodied energy for steel or other
owever,
ably high, thus reducing the sections and
quantity of steel used. It is for this reason that in order to compare
the sections generally used
It could be argued that
rammed earth walls are twice or three times (sometimes more) thicker
tephan, a concrete structure of a
itial embodied energy of all
and 7.2% over 100 years if one considers the
eventual replacement of some of these. However, taking into account the
consumption of the building over 100 years, the energy used in the
rete structure represents only 3.7% of the total energy
. This clearly demonstrates the importance of insulating a
building above all other aspects. However, if we look at the accumulation
the energy then
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
ere are other variables that establish the
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
as the cradle to cradle concept. There is a tendency now to exploit
recyclable materials as much as possible.
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 that they will be replaced as technologies emerge or as an
urban area evolves;
years later. We have seen also,
and the following recession, how
considerably and how we inherited vistas of
demand ceased. If we take the examples of Ireland and Spain, we will see
that construction was suspended and
years to come.
Figure 3 : Energy for concrete
structure compared to total amount of
energy necessary over 100 years
including replacement of materi
18,2
81,8
Recyclability are taking into account the lifecycle of materials such
as the cradle to cradle concept. There is a tendency now to exploit
as much as possible.
It is essential that buildings last in time, but it may be a bias to believe
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
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
and the following recession, how
considerably and how we inherited vistas of
If we take the examples of Ireland and Spain, we will see
that construction was suspended and
: Energy for concrete
structure compared to total amount of
energy necessary over 100 years
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 the cradle to cradle concept. There is a tendency now to exploit
as much as possible.
ldings last in time, but it may be a bias to believe
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
hat they will be replaced as technologies emerge or as an
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
If we take the examples of Ireland and Spain, we will see
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
and rest of embodied
energy including
material replacement
are taking into account the lifecycle of materials such
as the cradle to cradle concept. There is a tendency now to exploit
ldings last in time, but it may be a bias to believe
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
hat they will be replaced as technologies emerge or as an
built in the 70’s were destroyed 20 or 30
particularly in the recent economic boom
truction demand increased
urban scarification when the
If we take the examples of Ireland and Spain, we will see
structural skeletons left visible for
: Energy for concrete
structure compared to total
initial embodied energy
96,3
Embodied energy of
Energy Consumption
and rest of embodied
material replacement3
are taking into account the lifecycle of materials such
as the cradle to cradle concept. There is a tendency now to exploit
ldings last in time, but it may be a bias to believe
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
hat they will be replaced as technologies emerge or as an
30
particularly in the recent economic boom
increased
when the
If we take the examples of Ireland and Spain, we will see
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
.
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-avr
.
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-avr
.
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-avr
.
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-avr
.
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-avr
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-avr
.
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-avr
.
29
-avr
.
01
-ma
i
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lk d
en
sity
0
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2,0
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2,2
7
2,5
0
2,7
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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
Thermal mass and hygrometric
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
Thermal mass and hygrometric
properties are lost but the structure
appears on the outside.
Exterior
Thermal mass and hygrometric
properties are kept yet the structure
does not appear.
Middle
This technique is used by Sirewall. The
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
Insulation mplemented in 3 differents ways to a façade.
Thermal mass and hygrometric
properties are lost but the structure
appears on the outside.
Thermal mass and hygrometric
properties are kept yet the structure
chnique is used by Sirewall. The
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
mplemented in 3 differents ways to a façade.
Thermal mass and hygrometric
properties are lost but the structure
Thermal mass and hygrometric
properties are kept yet the structure
chnique is used by Sirewall. The
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 the soil. Most insulating materials
lose their quality and performance when in contact with a moist
environment. Furthermore, the wall is no longer acting as a whole but as
Inside
Inside
Inside
mplemented in 3 differents ways to a façade.
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
the soil. Most insulating materials
lose their quality and performance when in contact with a moist
environment. Furthermore, the wall is no longer acting as a whole but as
Outside
Outside
Outside
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
the soil. Most insulating materials
lose their quality and performance when in contact with a moist
environment. Furthermore, the wall is no longer acting as a whole but as
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
two separate parts. Sirewall stabilises their walls with up to 20% of
cement thus increasing the resistance and dealing with thinner walls. As
for the non-stabilised rammed earth project in this master thesis, this
solution will be abandoned.
Co-Operative housingThe co-operative housing program is essentially interesting in the case o
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 be found in traditional privat
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, smaller financial benefits can
carpooling, reducing costs in maintenance tools (lawnmower, working
tools, etc…), sharing meals
services between each other. In some co
two separate parts. Sirewall stabilises their walls with up to 20% of
increasing the resistance and dealing with thinner walls. As
stabilised rammed earth project in this master thesis, this
solution will be abandoned.
Operative housing operative housing program is essentially interesting in the case o
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 of program and therefore the strategy of the
program should lay within the concept of densifying the urban area.
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-operating as a whole. The motives for this
choice of living are various seen as multiple aspects convey advantages
found in traditional privat
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 site contribute to a greater sentiment of ownership.
, smaller financial benefits can
carpooling, reducing costs in maintenance tools (lawnmower, working
, sharing meals. Others may see the benefits of exchanging
services between each other. In some co
two separate parts. Sirewall stabilises their walls with up to 20% of
increasing the resistance and dealing with thinner walls. As
stabilised rammed earth project in this master thesis, this
operative housing program is essentially interesting in the case o
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
of program and therefore the strategy of the
pt of densifying the urban area.
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
operating as a whole. The motives for this
choice of living are various seen as multiple aspects convey advantages
found in traditional private housing. In some cases,
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
ite contribute to a greater sentiment of ownership.
, smaller financial benefits can also be developed by
carpooling, reducing costs in maintenance tools (lawnmower, working
. Others may see the benefits of exchanging
services between each other. In some co-housing communities, people
23
two separate parts. Sirewall stabilises their walls with up to 20% of
increasing the resistance and dealing with thinner walls. As
stabilised rammed earth project in this master thesis, this
operative housing program is essentially interesting in the case o
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
of program and therefore the strategy of the
pt of densifying the urban area.
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
operating as a whole. The motives for this
choice of living are various seen as multiple aspects convey advantages
e housing. In some cases,
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
ite contribute to a greater sentiment of ownership.
also be developed by
carpooling, reducing costs in maintenance tools (lawnmower, working
. Others may see the benefits of exchanging
housing communities, people
23
two separate parts. Sirewall stabilises their walls with up to 20% of
increasing the resistance and dealing with thinner walls. As
stabilised rammed earth project in this master thesis, this
operative housing program is essentially interesting in the case of
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
of program and therefore the strategy of the
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 brought
together by sharing spaces and tasks. The group of residents develop a
operating as a whole. The motives for this
choice of living are various seen as multiple aspects convey advantages
e housing. In some cases,
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
ite contribute to a greater sentiment of ownership.
also be developed by
carpooling, reducing costs in maintenance tools (lawnmower, working
. Others may see the benefits of exchanging
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
of ULB shows many penetration tests on the site of Tour et Taxi. There are
two zones to which the side is divided that define two different lay
types. Overall, embankments vary
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 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
of ULB shows many penetration tests on the site of Tour et Taxi. There are
zones to which the side is divided that define two different lay
mbankments vary in depth
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
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
of ULB shows many penetration tests on the site of Tour et Taxi. There are
zones to which the side is divided that define two different lay
in depth from 2 to 4m, alluvial clay
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
of Tour et Taxi (see Figure 16).
: Penetration test point N°794 Tour et Taxi, Brussels,
Geotechnical 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
zones to which the side is divided that define two different layer
from 2 to 4m, alluvial clay
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 testing is rather
common in Belgium and an analogical type could be easily found in the
: Penetration test point N°794 Tour et Taxi, Brussels, ULB soil mechanics
Geotechnical 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
er
from 2 to 4m, alluvial clay
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
common in Belgium and an analogical type could be easily found in the
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
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
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
services that they can provide.
Concept and Development
Most 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 on the north side
proposed rows of residential and office buildings that redraw a circulation
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 implantation for a co
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
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
services that they can provide.
ment
Most masterplans suggested residences in the south-west corner of the
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
on the north side. Some masterplans
al and office buildings that redraw a circulation
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
ation for a co-housing community. Furthermore,
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-housing communities would be
housing community is beneficial for each inhabitan
communities can be beneficial for every individual
elationships. Furthermore, this group
n be beneficial for the rest of the neighbourhood via
26
west corner of the
site. After comparing and understanding how these masterplans were
developed, it was finally taken into consideration only the south-west
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
. Some masterplans
al and office buildings that redraw a circulation
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 extent with the
“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
housing community. Furthermore,
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
housing communities would be
housing community is beneficial for each inhabitant. A group of co
individual group as it
elationships. Furthermore, this group
n be beneficial for the rest of the neighbourhood via
26
west corner of the
site. After comparing and understanding how these masterplans were
west
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
. Some masterplans
al and office buildings that redraw a circulation
through the site and transits into the urban tissue. These rows of separate
blocks communicate with the long existing building to the south yet
nt with the
“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
housing community. Furthermore,
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
housing communities would be
co-
group as it
of
n be beneficial for the rest of the neighbourhood via
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.
hand, unlike fired earth bricks, in the case of rammed earth constructions,
its resistance will incre
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, 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
for uplifting to occur. Tension is unfavourable for a rammed earth wall
and in fact its tensile strength could be considered null. It is possible to
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.
hand, unlike fired earth bricks, in the case of rammed earth constructions,
resistance will increase in time.
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 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
for uplifting to occur. Tension is unfavourable for a rammed earth wall
tensile strength could be considered null. It is possible to
resume tension through the second façades or it is possible to post
tension a rammed earth wall (Ward, 2006)
It is very unlikely that the project needs this kind o
structure and the exterior passage way work together as a whole via
hand, unlike fired earth bricks, in the case of rammed earth constructions,
If the rammed earth project was designed with the original soil that
developed a compressive strength of 3.8 MPa demonstrated in Part One
the security factor could go up to 6.
There are some negative effects with in-situ ramming such
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
erial. Nevertheless, it has been demonstrated in Part
that rammed earth is most likely to dry to a certain extent and thus
Even if this should not necessarily be taken
ount in the design, it does prove a positive effect on the
Due to overhangs and depression on slanted roofs, there is the possibility
for uplifting to occur. Tension is unfavourable for a rammed earth wall
tensile strength could be considered null. It is possible to
resume tension through the second façades or it is possible to post
(Ward, 2006).
It is very unlikely that the project needs this kind of technology. The roof
structure and the exterior passage way work together as a whole via
hand, unlike fired earth bricks, in the case of rammed earth constructions,
original soil that
demonstrated in Part One
situ ramming such as: control of
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
erial. Nevertheless, it has been demonstrated in Part
that rammed earth is most likely to dry to a certain extent and thus
Even if this should not necessarily be taken
ount in the design, it does prove a positive effect on the
, there is the possibility
for uplifting to occur. Tension is unfavourable for a rammed earth wall
tensile strength could be considered null. It is possible to
resume tension through the second façades or it is possible to post
f technology. The roof
structure and the exterior passage way work together as a whole via
hand, unlike fired earth bricks, in the case of rammed earth constructions,
demonstrated in Part One,
ntrol of
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
erial. Nevertheless, it has been demonstrated in Part
that rammed earth is most likely to dry to a certain extent and thus
Even if this should not necessarily be taken
ount in the design, it does prove a positive effect on the
, there is the possibility
for uplifting to occur. Tension is unfavourable for a rammed earth wall
tensile strength could be considered null. It is possible to
resume tension through the second façades or it is possible to post
f technology. The roof
structure and the exterior passage way work together as a whole via
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
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 resistance to wind was calculated in analogy to a
resultant was calculated
Where e is the equivalent eccentricity of the applied load and is given by :
M / V = H.L / V < l/6 where I is the wall thickness, V is this cas
selfweight and L the height of the wall.
l/6 is the value taken for retaining structures. This is discussed further.
wind load of 0.4kN/m
variable actions 1.5 and a reduction factor of 80% was app
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
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
ance to wind was calculated in analogy to a
resultant was calculated
Where e is the equivalent eccentricity of the applied load and is given by :
< l/6 where I is the wall thickness, V is this cas
selfweight and L the height of the wall.
l/6 is the value taken for retaining structures. This is discussed further.
of 0.4kN/m2 was taken. It was multiplied by the coefficient of
variable actions 1.5 and a reduction factor of 80% was app
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
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
ance to wind was calculated in analogy to a
Where e is the equivalent eccentricity of the applied load and is given by :
< l/6 where I is the wall thickness, V is this cas
selfweight and L the height of the wall.
l/6 is the value taken for retaining structures. This is discussed further.
t was multiplied by the coefficient of
variable actions 1.5 and a reduction factor of 80% was app
The results were the following :
32
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
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 factor of
retaining wall. The
Where e is the equivalent eccentricity of the applied load and is given by :
< l/6 where I is the wall thickness, V is this case the
l/6 is the value taken for retaining structures. This is discussed further.
t was multiplied by the coefficient of
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
s case where the walls are individual
and stand alone. It is only when they receive a concrete/bentonite
chaining on each level and that they are secured altogether with the
factor of
The
Where e is the equivalent eccentricity of the applied load and is given by :
e the
t was multiplied by the coefficient of
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
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Clare Lax, P. W. (2010). Life cycle assessment of rammed earth. Bath: Bath
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cemen.pdf
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34