Ifsttar PhD subject

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Title : Identification of soil suitability criteria for the refurbushing of excavated soils for earth building

Main host Laboratory - Referent Advisor MAST - GPEM  -  HAMARD Erwan      tél. : +33 240845651

Director of the main host Laboratory RICHARD Patrick  -

Laboratory 2 - Referent Advisor GERS - CG  -  RAZAKAMANANTSOA Andry  -    -  tél. : +33 240845804

PhD Speciality Génie Civil

Axis of the performance contract 2 - COP2017 - More efficient and resilient infrastructure

Main location Nantes

Doctoral affiliation UNIVERSITE DE NANTES

PhD school Sciences de l'Ingénierie et des Systèmes (SIS)

Planned PhD supervisor CAZACLIU Bogdan  -  Université Gustave Eiffel  -  MAST - GPEM

Planned PhD co-supervisor DUC Myriam  -  Université Gustave Eiffel  -  GERS - SRO

Planned financing Contrat doctoral  - Ifsttar

Abstract

The construction sector is recognised as one of the main contributors to climate change and is responsible for 50% of the European Union's waste production. The sector's environmental impacts are mainly generated during the service life by heating, but also by the extraction and production of common building materials such as cement. Today, the building sector is the main contributor to climate change and energy consumption in the world. One of the challenges is therefore to find constructive solutions that have a low impact on the environment.

Among the possible constructive solutions, the rediscovery and rationalization of traditional processes and materials such as earth is promising. Raw earth has been used as a building material since the Neolithic period. In France, there are about 1 million earthen dwellings (rammed earth, adobe and cob).

Raw earth construction is likely to have major environmental interests. Among the waste produced by human activities, excavated soil represents the main mass, i.e. about 75%, and was estimated at between 2.7 and 5.9 tonnes/inhabitant/year in Europe for 2005. This makes it one of the most available materials in the world in terms of quantity, but also in terms of geographical distribution, as the deposit linked to excavation can be found on or near the construction site. Earth walls have a high thermal inertia allowing a good management of solar gains reinforced by their hygroscopicity which allows it to regulate indoor air humidity. Finally, the low amount of transformation required to use raw earth as a building material gives it a very low embodied energy compared to conventional materials. Thus, for an earth wall, the embodied energy is 20 times less important than for a hollow cinder block wall.

The main interest of the raw earth material processing processes is their ability to adapt to the resources available locally and thus to use soils as close as possible to the construction site while limiting transport. However, the identification of the implementation techniques adapted to a particular soil is nowadays carried out by experienced master craftsmen. This determination is based on a "sensory" approach (analysis of the earth through touch, smell and taste) that requires a long learning time.

This approach is not available to inexperienced builders. Providing soil identification solutions would facilitate this work. In addition, the development of earth building sector requires a secure supply of raw materials. To ensure this supply, it is again necessary to identify soil for the producers of the resource (earthwork contractors, quarries) and the companies in charge of implementation. The development of a decision support tool based on the French Road Earthworks Guide (GTR) is proposed as the objective of this thesis work.

This development will use the recent and ongoing work at IFSTTAR, based on the cross-referencing of heritage and soil data, which has made it possible to develop new methods for assessing the suitability of soils for the construction of Brittany. The characteristics of Breton cob are now known. The deployment of these methods in other territories, particularly in the Ile de France region, as well as their synthesis on a national scale, should make it possible to produce the decision support tool targeted.

In addition, the Eco Terra research programme funded by Ademe (ongoing project) has made it possible to make progress in determining the characteristics of earth suitable for the light earth technique. A study carried out jointly by ENTPE, Cerema and IFSTTAR on the characterisation of soil taken from rammed earth buildings in the Auvergne-Rhône-Alpes region is currently being published. Heritage and soil data are also being acquired for Normandy (wattle and daud and cob), Tarn-et-Garonne (adobe) and the Auvergne-Rhône-Alpes region (rammed earth). The thesis work will consist in continuing this work of crossing soil and heritage data, using statistical tools, to enrich existing data.

The comparison between the types of soils suitable for the different techniques studied (adobe, cob, rammed earth, light earth) will be carried out in a multidisciplinary approach, combining geology, pedology, geotechnics, soil mechanics and geochemistry. This approach should identify the soil characteristics necessary for the implementation of wet (cob, adobe and light earth) and dry (rammed earth and CEB) techniques as well as characteristics for the implementation of monolithic (rammed earth and cob) and masonry (adobe and CEB) techniques. It will then be possible to rationally explain what makes land suitable or not and to establish a decision support tool.

To broaden the range of recoverable soils, the use of stabilisers of organic origin will be one of the parameters to be considered as part of the decision support tool (performance prediction with or without additives). To do this, we will use the results of the Alluvium project funded by the I-SITE FUTURE and which concerns the stabilization of the Grand Paris area with the help of biopolymers. Soils with too much clay (e. g. Ile-de-France green clays) or too little cohesion can be stabilised with biological stabilisers and thus be used in construction.

A final, more exploratory part of this thesis will focus on the development of site tests for masons to determine the suitability of construction techniques for earth building. There are now many site tests, often inspired by soil recognition tests in geotechnics, which are used by masons (ribbon test, hydrometer test, ball test …). However, these tests are often misunderstood, misused and redundant. A rational analysis of these tests, supplemented by a pedologist's vision, should make it possible to sort through the many existing tests and propose a more discriminating approach.

This work will be carried out in close collaboration with the profession through the Projet National Terre Crue, managed by IFSTTAR. It will benefit from a funding of IREX.

The PhD candidate will be part of a multidisciplinary team (geologist, soil mechanic, geotechnicians and physico-chemists). For this thesis, we are looking for a soil specialist with a background in soil science. It should be able to analyse soil data and draw up soil maps. He/she will therefore have skills in soil database analysis (French Référentiel Régional Pédologique) and Geographic Information System. He/she must also show sensitivity to the raw earth subject. He/she must be autonomous, curious, dynamic and have the ability to make proposals.

Hamard E, Cazacliu B, Razakamanantsoa A, Morel J-C (2016) Cob, a vernacular earth construction process in the context of modern sustainable building. Build Environ 106:103–119. doi: 10.1016/j.buildenv.2016.06.009
Hamard E, Lemercier B, Cazacliu B, et al (2018) A new methodology to identify and quantify material resource at a large scale for earth construction – Application to cob in Brittany. Constr Build Mater 170:485–497. doi: 10.1016/j.conbuildmat.2018.03.097
Hamard E, Cammas C, Lemercier B, et al (2019) Micromorphological description of vernacular cob process and comparison with rammed earth. Front Archit Res. doi: 10.1016/j.foar.2019.06.007

Keywords : Earth building, soil suitability, pedology, geology, geotechnics, eochemistry, soil mechanics

Main host Laboratory - Referent Advisor	MAST - GPEM - HAMARD Erwan tél. : +33 240845651
Director of the main host Laboratory	RICHARD Patrick -
Laboratory 2 - Referent Advisor	GERS - CG - RAZAKAMANANTSOA Andry - - tél. : +33 240845804
PhD Speciality	Génie Civil
Axis of the performance contract	2 - COP2017 - More efficient and resilient infrastructure
Main location	Nantes
Doctoral affiliation	UNIVERSITE DE NANTES
PhD school	Sciences de l'Ingénierie et des Systèmes (SIS)
Planned PhD supervisor	CAZACLIU Bogdan - Université Gustave Eiffel - MAST - GPEM
Planned PhD co-supervisor	DUC Myriam - Université Gustave Eiffel - GERS - SRO
Planned financing	Contrat doctoral - Ifsttar
Abstract The construction sector is recognised as one of the main contributors to climate change and is responsible for 50% of the European Union's waste production. The sector's environmental impacts are mainly generated during the service life by heating, but also by the extraction and production of common building materials such as cement. Today, the building sector is the main contributor to climate change and energy consumption in the world. One of the challenges is therefore to find constructive solutions that have a low impact on the environment. Among the possible constructive solutions, the rediscovery and rationalization of traditional processes and materials such as earth is promising. Raw earth has been used as a building material since the Neolithic period. In France, there are about 1 million earthen dwellings (rammed earth, adobe and cob). Raw earth construction is likely to have major environmental interests. Among the waste produced by human activities, excavated soil represents the main mass, i.e. about 75%, and was estimated at between 2.7 and 5.9 tonnes/inhabitant/year in Europe for 2005. This makes it one of the most available materials in the world in terms of quantity, but also in terms of geographical distribution, as the deposit linked to excavation can be found on or near the construction site. Earth walls have a high thermal inertia allowing a good management of solar gains reinforced by their hygroscopicity which allows it to regulate indoor air humidity. Finally, the low amount of transformation required to use raw earth as a building material gives it a very low embodied energy compared to conventional materials. Thus, for an earth wall, the embodied energy is 20 times less important than for a hollow cinder block wall. The main interest of the raw earth material processing processes is their ability to adapt to the resources available locally and thus to use soils as close as possible to the construction site while limiting transport. However, the identification of the implementation techniques adapted to a particular soil is nowadays carried out by experienced master craftsmen. This determination is based on a "sensory" approach (analysis of the earth through touch, smell and taste) that requires a long learning time. This approach is not available to inexperienced builders. Providing soil identification solutions would facilitate this work. In addition, the development of earth building sector requires a secure supply of raw materials. To ensure this supply, it is again necessary to identify soil for the producers of the resource (earthwork contractors, quarries) and the companies in charge of implementation. The development of a decision support tool based on the French Road Earthworks Guide (GTR) is proposed as the objective of this thesis work. This development will use the recent and ongoing work at IFSTTAR, based on the cross-referencing of heritage and soil data, which has made it possible to develop new methods for assessing the suitability of soils for the construction of Brittany. The characteristics of Breton cob are now known. The deployment of these methods in other territories, particularly in the Ile de France region, as well as their synthesis on a national scale, should make it possible to produce the decision support tool targeted. In addition, the Eco Terra research programme funded by Ademe (ongoing project) has made it possible to make progress in determining the characteristics of earth suitable for the light earth technique. A study carried out jointly by ENTPE, Cerema and IFSTTAR on the characterisation of soil taken from rammed earth buildings in the Auvergne-Rhône-Alpes region is currently being published. Heritage and soil data are also being acquired for Normandy (wattle and daud and cob), Tarn-et-Garonne (adobe) and the Auvergne-Rhône-Alpes region (rammed earth). The thesis work will consist in continuing this work of crossing soil and heritage data, using statistical tools, to enrich existing data. The comparison between the types of soils suitable for the different techniques studied (adobe, cob, rammed earth, light earth) will be carried out in a multidisciplinary approach, combining geology, pedology, geotechnics, soil mechanics and geochemistry. This approach should identify the soil characteristics necessary for the implementation of wet (cob, adobe and light earth) and dry (rammed earth and CEB) techniques as well as characteristics for the implementation of monolithic (rammed earth and cob) and masonry (adobe and CEB) techniques. It will then be possible to rationally explain what makes land suitable or not and to establish a decision support tool. To broaden the range of recoverable soils, the use of stabilisers of organic origin will be one of the parameters to be considered as part of the decision support tool (performance prediction with or without additives). To do this, we will use the results of the Alluvium project funded by the I-SITE FUTURE and which concerns the stabilization of the Grand Paris area with the help of biopolymers. Soils with too much clay (e. g. Ile-de-France green clays) or too little cohesion can be stabilised with biological stabilisers and thus be used in construction. A final, more exploratory part of this thesis will focus on the development of site tests for masons to determine the suitability of construction techniques for earth building. There are now many site tests, often inspired by soil recognition tests in geotechnics, which are used by masons (ribbon test, hydrometer test, ball test …). However, these tests are often misunderstood, misused and redundant. A rational analysis of these tests, supplemented by a pedologist's vision, should make it possible to sort through the many existing tests and propose a more discriminating approach. This work will be carried out in close collaboration with the profession through the Projet National Terre Crue, managed by IFSTTAR. It will benefit from a funding of IREX. The PhD candidate will be part of a multidisciplinary team (geologist, soil mechanic, geotechnicians and physico-chemists). For this thesis, we are looking for a soil specialist with a background in soil science. It should be able to analyse soil data and draw up soil maps. He/she will therefore have skills in soil database analysis (French Référentiel Régional Pédologique) and Geographic Information System. He/she must also show sensitivity to the raw earth subject. He/she must be autonomous, curious, dynamic and have the ability to make proposals. Hamard E, Cazacliu B, Razakamanantsoa A, Morel J-C (2016) Cob, a vernacular earth construction process in the context of modern sustainable building. Build Environ 106:103–119. doi: 10.1016/j.buildenv.2016.06.009 Hamard E, Lemercier B, Cazacliu B, et al (2018) A new methodology to identify and quantify material resource at a large scale for earth construction – Application to cob in Brittany. Constr Build Mater 170:485–497. doi: 10.1016/j.conbuildmat.2018.03.097 Hamard E, Cammas C, Lemercier B, et al (2019) Micromorphological description of vernacular cob process and comparison with rammed earth. Front Archit Res. doi: 10.1016/j.foar.2019.06.007
Keywords :	Earth building, soil suitability, pedology, geology, geotechnics, eochemistry, soil mechanics

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