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Proceedings of International Structural Engineering and Construction, 11(1), 2024
Leading Construction Technology Systems for Today’s Environmental and Social Crises
Edited by Villacís, E., Ayarza, C., Bucheli, J., Yazdani, S., and Singh, A.
Copyright © 2024 ISEC Press
ISSN: 2644-108X
www.doi.org/10.14455/ISEC.2024.11(1).SUS-01
SUS-01-1
RAMMED EARTH CONSTRUCTION: A CIRCULAR
SOLUTION FOR SUSTAINABLE BUILDING
GIAMMARCO MONTALBANO1, GIOVANNI SANTI1, and NAJEM KHOULOUD2
1Dept of Energy, Systems, Territory, and Constructions Engineering (D.E.S.T.e.C.),
University of Pisa, Italy
2National School of Architecture of Marrakech (ENAM), Marrakech, Morocco
The building and construction sector is one of the most harmful industries to the
environment, responsible for producing high levels of greenhouse gas (GHG) emissions,
energy consumption, and waste. Rammed earth, a traditional building technology is
deemed as a promising solution to tackle these challenges. In addition, the low level of
skill required for rammed earth buildings paves the way for self-built activities. This
paper presents the preliminary findings of an ongoing research study focused on the
rammed earth construction technique. The primary objective is to assess its sustainability
and circularity within the context of Europe and the Mediterranean. The methodology
employed is based on an analysis of rammed earth techniques and a review of relevant
regulations related to the selected context. The analysis includes case studies of
contemporary European rammed earth buildings. They aim to illustrate possible design
strategies that incorporate rammed earth alongside well-established construction
technologies. These case studies also shed light on how the integration of various
construction technologies introduces circularity variables into buildings, thereby
influencing their overall sustainability. These variables are contingent upon the
techniques, technologies, and performance characteristics of the selected building
elements. As a result of this analysis, the paper initiates a discussion on the role that
rammed earth constructions can play in the development of sustainable hybrid buildings.
Keywords: Sustainability, Sustainable construction, Circular buildings, Frugal
architecture, Vernacular architecture, Raw earth.
1 INTRODUCTION
The growing concern about climate change is placing the concept of sustainability in the spotlight.
In this context, the construction sector plays a crucial role in achieving the environmental goals set
by the Paris Agreement in 2015. This sector is responsible for approximately 40% of global
operational and process-related CO2 emissions (UNEP 2022), as well as significant consumption
of natural resources and the generation of waste. Additionally, the sector must face the increasing
of the by 2050 (UN DESA Population Division 2022), which will rise the demand for housing.
The scientific community deems the establishment of a circular economy (CE) within the building
and construction sector as a key factor in reducing its environmental impact. Here, the choice of
building material is fundamental to enable the application of CE practices. Specifically, raw earth,
a traditional material used in vernacular architectures globally, is widely recognized as a sustainable
option due to its abundant availability, recyclability, and low embodied energy throughout its life
cycle, as also the frugal architectures represent. In the European context, only a few countries have
ruled the use of raw earth (Jiménez Delgado and Guerrero 2007). The lack of clear regulations and
Villacís, E., Ayarza, C., Bucheli, J., Yazdani, S., and Singh, A. (eds.)
SUS-01-2 © 2024 ISEC Press
uncertainty about its mechanical behavior restrict its use. This paper examines the use of raw earth
in construction, specifically the rammed earth (RE) technique. It presents preliminary findings
from ongoing research by the DESTeC department at the University of Pisa on the sustainability
and circularity of raw earth in RE construction.
2 MATERIALS AND METHODS
This qualitative research seeks to investigate the role of the RE construction technique in promoting
sustainability and supporting the CE within the European and Mediterranean regions. The analysis
encompasses an evaluation of the features of raw earth and RE construction, emphasizing their
sustainability and circular potential. A comprehensive review of global codes about earthen
construction has been conducted to determine the countries where RE is ruled. However, this paper
focused only on European and Mediterranean codes due to the specific context of our study. Two
case studies showcasing the use of the RE technique in contemporary European architecture are
presented. These case studies are located in different European countries and demonstrate the
influence of regulatory frameworks on technological choices. Furthermore, a comparative analysis
is performed with an example of Moroccan vernacular architecture. This comparison aims to
identify possible connections between contemporary and traditional construction methods and to
facilitate a discussion on their contributions to sustainability and circularity.
Sustainability of raw earth as a construction material are well-known. It is natural, locally
available, reducing CO2 emissions from transportation. Using raw earth also allows to reduce
construction site waste, since it represents a significant portion of C&D waste resulting from
excavation operations. In its natural state, raw earth is infinitely reusable (Bui and Morel 2015). It
means that when a raw earth building reaches its end of life, natural raw earth can be completely
reused or restored. Additives like cement enhances raw earth properties, but affect earth's low
embodied energy making it less sustainable (Arduin et al. 2022). Raw earth holds promise as a
sustainable alternative in developed countries like those in Europe; while it is widely used in the
construction of low-tech buildings in many developing countries (Giuffrida et al. 2019). The key
features of raw earth as a construction material are highlighted and associated with CE practices
(Table 1). These would come into play if raw earth were utilized as an alternative to commonly
used construction materials like concrete or bricks, which rely on construction techniques similar
to those used with raw earth.
Table 1. Raw earth features and circular economy practices.
Raw earth features
Circular economy
practices
Notes
Completely natural material and
easily available
Reduce
In its natural state raw earth has a very low
embodied energy. This is due to the fact that the
raw earth sourcing and processing do not involve
carbon intensive processes.
Raw earth can be sourced and
processed directly on site. Its
processing does not produce waste.
Reduce
Raw earth if not mixed can be
recycled and reused multiple times.
Reuse, Recycle,
Reduce
Earthen constructions that rely only on raw earth
use mechanical processes to compact raw earth,
without binding it with chemical adhesives.
2.1 Rammed Earth: Construction Techniques and Features
RE is one of the most used earthen construction techniques. It is a load-bearing and wet
construction technique. It allows to build continuous load-bearing walls with a very high density,
ranging between 1800 kg/m3 and 2000 kg/m3 (Giuffrida et al. 2019). RE involves compacting
Proceedings of International Structural Engineering and Construction, 11(1), 2024
Leading Construction Technology Systems for Today’s Environmental and Social Crises
SUS-01-3 © 2024 ISEC Press
layers of soil between temporary formworks up to the desired level. Each layer has a height of
about 8 cm to 15 cm (Bui and Morel 2015, Ávila et al. 2021) and the soil compaction is achieved
by using manual or mechanical rammer. Usually, the resulting walls have large thickness ranging
from 30 cm to 80 cm. Soils suitable for construction purposes are subsoils, excavated at least 1
meter below the surface (Gomaa et al. 2023), as topsoils can be sensitive to shrinkage and decay
(Morel et al. 2021). The average composition of the soil used in RE constructions is a mixture of
clay, sand, gravel, sometimes also fibers with different proportions (Ávila et al. 2021, Gomaa et al.
2023). Regarding structural features, two types of RE can be distinguished: unstabilized rammed
earth (URE) and stabilized rammed earth (SRE) (Bui and Morel 2015, Ávila et al. 2021). URE
consists of pure soil without additives, with clay acting as the binder. SRE involves blending pure
soil with artificial additives, commonly cement and lime, to enhance cohesion and mechanical
performance. However, the use of chemical stabilizers impacts the sustainability of RE, as they
result from energy-intensive production processes, emit high levels of CO2 and GHG gases, and
deplete natural resources (Arduin et al. 2022). These additives increase the embodied energy of
RE and complicate reuse due to chemical bonds formed with the soil. In contrast, URE provides a
sustainable and circular alternative to the stabilized version. URE's cohesion and mechanical
properties can be enhanced physical stabilization techniques. Physical stabilization involves
sorting and sifting the raw earth mixture to maintain proper particle proportions. Well-sorted
mixtures create denser RE walls by eliminating voids between particles. By focusing on particle
size through sorting and sifting, raw earth's mechanical properties can be improved naturally.
2.2 Rammed Earth Codes in Europe
In many countries raw earth in constructions is thoroughly regulated. However, in the European
and Mediterranean area only a few countries ruled it. Here, the lack of regulations is one of the
hinders to the use of raw earth, especially in load-bearing structures (Jiménez Delgado and Guerrero
2007, Giuffrida et al. 2019). In Germany DIN standards1 rules prefabricated earth products, earth
plasters, and earth mortars; while the Lehmbau Regeln rules RE constructions. In Switzerland the
Regeln zum Bauen mit Lehm covers various earthen construction techniques, including RE. In
France, the XP-13-901 regulates compressed earth blocks (CEB), but there are not specific rules
for RE constructions. Spanish regulations cover RE constructions. UK has specific guidelines for
RE buildings design and construction, which became the reference document for RE. In Africa
there is the ARSO standard, which include only CEB (Jiménez Delgado and Guerrero 2007). The
other countries of the area do not have specific regulations for RE. Overall, the chosen area lacks
a common standard for regulating earthen construction, similar to Eurocodes for other common
building materials. The analysis of regulations reveals a focus on industrial products, as their
standardized dimensions and homogeneity facilitate mechanical property testing. However, RE
construction presents challenges for standardization due to the use of roughly processed raw earth,
often in its pure state, and the reliance on workers' expertise for manual labor. Additionally, testing
the mechanical properties of RE can be difficult due to the variability of soil composition, which
affects its mechanical features. Standardizing RE may require specific soils that may not be readily
available on-site, affecting the benefits of material availability and low embodied energy. This
1
DIN 18945 for Compressed Earth Blocks, DIN 18946 for raw earth-based mortars, DIN 18947 for earth plasters and DIN 18948
for other earth-based Panels
Villacís, E., Ayarza, C., Bucheli, J., Yazdani, S., and Singh, A. (eds.)
SUS-01-4 © 2024 ISEC Press
reliance on specific soils may also increase environmental impact through transportation-related
CO2 emissions.
3 DISCUSSION: CASE STUDIES ANALYSIS
In Europe, there are few new constructions utilizing RE among the new buildings. These projects
are mainly located in countries that have ruled this technique. In general, RE is gaining ground in
hybrid technologies, which integrate various construction systems. It is also evident in vernacular
construction techniques. In countries with stringent regulations regarding building safety and
performance and RE is not regulated, the development of hybrid technologies facilitates the
incorporation of RE alongside well-established methods like reinforced concrete, steel, or wood.
This is particularly pronounced in European countries. This section presents two European RE
architectures to illustrate the concept of hybrid technologies. In these projects, RE has different
structural functions: load-bearing and non-load-bearing. These functions have a significant impact
on the circularity of the building, introducing certain circularity variables, which will be explained.
The selected projects are: The Rauch House, a private building designed by Roger Boltshauser and
Martin Rauch, and a public RE tower designed by architect De Gouden Liniaal. The Rauch House,
built between 2005 and 2008 in Austria, stands out as a prominent RE construction. In this building,
RE walls fulfil load-bearing roles, and beams composed of reinforced trass lime mortar connect the
slabs to the walls, as illustrated in Figure 1.
1. Rich loam
2. Foam-glass insulation
3. Low fired mud tiles
4. Reed insulation
5. Cork-clay-trass-lime mix
6. Rammed earth floor
7. Reinforced trass-lime
mortar
8. T-beam 60/60
9. Foam-glass filling
10. Reinforced concrete
foundations
Figure 1. The Rauch House: Detail of the foundations, one of the most interesting to focus on due to the
rising damp phenomenon, and of the slab-rammed earth wall joint (graphic elaboration by the authors).
These elements are embedded within the thickness of the walls, serving the purpose of
distributing the loads from the slabs' primary structure along the top of the walls. This distribution
helps prevent concentrated loads. Foundations in RE buildings are crucial for both structural
integrity, especially in seismic areas to be compliant to the regulations, and for addressing moisture-
related issues. RE buildings are susceptible to moisture absorption due to their porosity.
Consequently, foundations must rely on well-established technologies such as concrete. Concrete
enables precise design in response to stress, ensuring resistance. It also helps to separate the ground
from the RE walls, reducing moisture absorption. Rauch House utilizes materials that can be reused
as the walls and floors are made from natural, raw earth. However, it incorporates elements from
other construction technologies, like concrete foundations and trass-lime reinforced beams, making
certain parts of the building non-reusable or non-recyclable. Nevertheless, these components
represent a small portion of the overall resources used for the building and they can be easily
separate from the RE. The RE Tower (2012), is located in the Negenoord, a former gravel quarry
situated on the Belgium-Netherlands border. The 12-meter observation tower combines a concrete
Proceedings of International Structural Engineering and Construction, 11(1), 2024
Leading Construction Technology Systems for Today’s Environmental and Social Crises
SUS-01-5 © 2024 ISEC Press
core with an RE outer shell. Collaborating with CRATerre, experts in earthen architecture, was
essential due to the lack of specific regulations for RE buildings in Belgium and the Benelux area.
The wall mixture consists of clay, sand, gravel, and 6% cement. The choice of cement as a stabilizer
was made due to the contractor's inability to certify the material's strength using more sustainable
stabilizers like lime. Structurally, the tower exhibits a cooperative relationship between the earth
and the concrete core, even if the RE panels are not meant to be load-bearing. The landings within
the tower are connected to the concrete core at one end, while being supported by 80 cm thick RE
walls at the other end. The tower's foundations are built using concrete to raise the RE walls above
the ground, as shown in Figure 2, and prevent rising dump phenomena.
1. Rammed earth wall
2. Prefabricated sloped concrete
3. Reinforced concrete plinth
4. Reinforced concrete core
5. Reinforced concrete
foundations
6. Pile foundations
Figure 2. Detail of the foundations and the basement of the tower. It is evident that RE can be utilized
in damp environments as well (graphic elaboration by the authors).
The buildings presented here exhibit significant differences. The Rauch House can be regarded
as an example of sustainability and circularity due to its use of RE, even though some construction
elements are not circular, such as reinforced truss-lime beams and concrete foundations. The
Negeenord Tower does not prioritize sustainability, as evidenced by its extensive use of concrete
and cement. Therefore, when considering hybrid RE buildings, it is essential to consider that design
choices can introduce certain circularity variables into the construction process. The use of
concrete components and cement as additives represents the most significant circularity variables
found in the cases studied. A comparison between the two recent architectures presented and
vernacular architecture and technologies in RE can be drawn. To facilitate this, examples of
buildings built in Morocco, specifically in the village of Alnif (Figure 3), are presented2.
Figure 3. Rammed earth architectures in Alnif, Morocco. Left: Rammed earth vertical wall with
embedded wooden pillars. Center: Lightweight wooden floor. Right: Overview of the rammed earth wall-
floor joint (photos taken by the authors, 2023).
The surveys reveal a strong connection between RE buildings and the utilization of hybrid
technologies. However, in these Moroccan examples, it becomes evident that wood was the
2
The examples presented are part of a research that has been developed in the field of an international agreement between D.E.S.T.e.C
of the University of Pisa and The National School of Architecture of Marrakech (ENAM).
Villacís, E., Ayarza, C., Bucheli, J., Yazdani, S., and Singh, A. (eds.)
SUS-01-6 © 2024 ISEC Press
preferred material for building elements stressed by bending and shear, such as slabs. It is
noteworthy that a lightweight wooden technological system is combined with a thicker one in RE.
This choice not only reflects the relationship between buildings and their surroundings but also
demonstrates how regional material availability and worker skills influenced the selection of wood
and raw earth. Nonetheless, the combination of wood and RE proves to be a successful approach
in terms of circularity and sustainability. These Moroccan examples suggest to deepen the wood-
RE relationship.
4 CONCLUSION
Globally, raw earth presents a viable alternative to carbon-intensive building materials. However,
in European and Mediterranean areas, the absence of standardized regulations for designing,
testing, and validating material properties hinders its widespread adoption. The case studies
illustrate how RE can be integrated with existing regulated technologies, despite the trade-off of
incorporating less sustainable materials. The lack of common regulations contributes to
uncertainty, prompting designers to rely on well-known and standardized construction
technologies. This, in turn, facilitates the incorporation of circularity variables into the buildings.
Moreover, these circularity variables are subordinated to the techniques, technologies, and
performance of building elements, and can compromise the sustainability of the buildings. Lastly,
it is worthwhile to explore the historical relationship between wood technology and renewable
energy, as exemplified by Moroccan examples. These instances highlight the connection between
buildings and the environment, particularly in terms of materials and building technologies. Future
research will focus on the relationship between innovative lightweight structures and traditional
construction techniques such as RE. The research will be contextualized within the framework of
creative frugality in architecture and the building and construction sector.
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