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The reuse of load-bearing building components has the potential to promote the circular economy in the building sector. One recent aspect of the efforts to improve reuse rates in buildings is estimating the reusability of the structural elements. This study develops a probabilistic predictive model using advanced supervised machine learning methods to evaluate the economic reusability of the load-bearing building elements. The results of sensitivity analysis and visualization techniques used in this study reveal that the most important economic factor is the need to purchase reused elements early in a project, which could have cash flow implications. The other most important factors are the potential financial risks, the procurement process, and the labour cost. This study unveils that the relationship between variables is not linear, and none of the identified factors could alone determine if an element is reusable or not. This study concludes that the complex interdependencies of factors affecting reuse cause a high level of uncertainty about the feasibility of reusing the load-bearing building structural components from an economic aspect. Nonetheless, this paper reveals that by using the probability theory foundations and combining it with advanced supervised machine learning methods, it is possible to develop tools that could reliably estimate the economic reusability of these elements based on affecting variables. Therefore, the authors suggest utilizing the approach developed in this research to promote the circularity of materials in different subsectors of the construction industry.

The global challenge of large-scale climate change mitigation requires action also in the building and construction sector. From a life cycle perspective, and considering the mitigation timeframe, the issue of reducing embodied GHG emissions is gaining attention. Effective ways to reduce embodied GHG emissions have been proposed by the use of fast-growing, bio-based materials, due to carbon sequestered in the biomass. Another promising, yet largely under-explored option is to harness the environmental potentials and low embodied GHG emissions of earth-based materials for building construction. Earth construction dates back from 10,000 to 8000 BC and has been derived in many vernacular construction techniques. More recently, some earthen techniques have been modified, using stabilizers, mainly cement and lime, to increase strength and water stability. The objective of this article is to compare existing literature performed on the LCAs applied to various earthen construction techniques and seek for key factors. Transports as well as binder stabilizations are very influent on the results. Climate, nature of local soil, and geographical context are very influent on functionalities of buildings, mix design and transports, themselves influencing environmental impacts. According to design choices and local context, earthen construction is not always better than concrete. This means that no universal solution can be recommended with the LCA of an earthen wall. The solution has to be adapted to the local context. All references comparing walls material to conventional materials at the building scale, find better environmental performances of earthen walls compared to fired brick walls. However, a full comparison between earthen construction and conventional materials should account for the use phase: combining LCA models with thermal and durability models is a key research issue. Finally, it certainly would be useful to seek for solutions with best environmental performances in a local context, accounting for the nature of soil, the building's functional requirements as well as geographical and cultural specificities. Such an approach would ensure to lower environmental impacts but represents a drastic change in current construction practices. Whereas today building materials are standardized in order to fit with construction working practices, this paradigm shift would require to adapt construction working practices to the local material and context. As earthen construction is today, in many countries of the world, a re-emerging technique, and new professional practices are yet to be established, it seems possible to make this paradigm shift happen. Certainly, in the current context of the need to substantially reduce building-related GHG emissions, there is still strong potential in earth construction techniques for both research and building practice.

Earthen construction is re-gaining popularity as an ecological and economical alternative to contemporary building materials. While building with earth offers several benefits, its performance due to water ingress is a concern for its widespread application. This limitation is often solved by adding chemical stabilisers such as Portland cement and hydraulic lime. Chemical stabilisers are a subject of widespread debate as they increase the cost and embodied energy of the structure, and reduce the desirable characteristics of raw or unstabilised earth. This along with perceived environmental performance, renewability, and proven effectiveness in traditional earthen construction has led to a growing interest in biological or organic stabilisers. Although the strengthening mechanism of biological stabilisers is widely covered in scientific studies, discussion regarding the water-resistance is limited. This review aggregates the research from the field of earthen construction and geotechnical engineering and extends it to explain the possible mechanism responsible for the water-resistance behaviour of biologically stabilised earthen materials. This study includes a wide range of traditional and industrial biological stabilisers derived from animals (cow-dung, casein, chitosan), plants (starch, guar gum, cactus mucilage, lignin, tannin) seaweeds (alginate, agar, carrageen) and microbes (xanthan gum, gellan gum). A conceptual model of water-ingress in unstabilised earthen blocks is proposed and the response of biological stabiliser to water ingress and related physico-chemical and physical factors is discussed using the model at microscale (stabiliser interaction with clay, sand) and macroscale (hydraulic conductivity of block). Properties of stabilisers such as hydrophobicity, stability under wet conditions or interaction with cations have a dominant effect on the overall response to water ingress. Key gaps have been identified in the existing knowledge that are necessary to investigate in order to understand the water-resistance behaviour comprehensively. The study concludes with a brief assessment of biological stabilisers based on their performance and feasibility to use in contemporary earthen construction., Construction Technologies and Architecture, 1, ISSN:2674-1237, Bio-Based Building Materials

Earth is an ancient construction material that is attracting numerous scientific investigations due to the sustainable characteristics of this material and the significant heritage of existing earth constructions. Several studies have recently been conducted to investigate the seismic performance of earth buildings. This chapter presents the state of the art related to the seismic performance of earth structures. Since the seismic performance of a structure depends both on the dynamic and static characteristics of the material and the structure, the chapter starts with a summary of the static characteristics, followed by the results on the dynamic characteristics. Then the existing methods for the earthquake performance evaluation are presented. Finally, the techniques of seismic strengthening are cited and discussed. This chapter is a useful repertoire for further studies on the seismic design of earthen structures., This chapter is prepared in the case of the RILEM Technical Committee TC 279-TCE (Testing and characterisation of earth-based building materials and elements). The authors wish to thank the French National Research Agency (ANR) for funding the PRIMATERRE project (ANR-12-Villes et Bâtiments Durables). Several results presented in this paper are the outcome of this project. The funding from the ReBuMAT project (German-Vietnamese Collaborative Project on Resource-efficient Construction using Sustainable Building Materials) is acknowledged. Part of this work was also carried out within the framework of project POCI-01-0145-FEDER-016737 (PTDC/ECM-EST/2777/2014), financed by FEDER funds through the Competitivity Factors Operational Programme—COMPETE and by FCT—Foundation for Science and Technology. The funding provided is kindly acknowledged. This work was partly financed by FEDER funds through the Competitivity Factors Operational Programme—COMPETE and by national funds through FCT—Foundation for Science and Technology within the scope of project SafEarth (PTDC/ECM-EST/2777/2014).

Earth based building materials having low or negligible carbon footprint are looked upon as a sustainable alternative building material in the construction sector. The confidence of using any building material is augmented with through understanding of its mechanical properties. A brief review on the mechanical properties of the building materials such as Rammed Earth, Earth Blocks (Adobe, Compressed Earth Block, and Extruded Blocks) and Cob, which are manufactured using raw earth or by adding very little additives are presented in this chapter. The mechanical behaviour of earth based building material is highly dependent on raw material, manufacturing technique and testing conditions. Therefore it is highly recommended to conduct through experimental campaign for every soil mix. This chapter also presents various experiments recommended to study the mechanical properties of the materials.

To facilitate the adoption of the circular economy (CE) in the architecture, engineering and construction (AEC) sector, some authors have demonstrated the potential of recent designs that take into account the sustainable management of an asset’s end-of-life (EOL), providing an alternative to the dominant designs that end with demolition. However, there is no review of the literature that encompasses a large range of sustainable designs in the current CE context. This paper provides a critical review of journal papers that deal with the barriers to implementing sustainable designs and approaches to the EOL management of assets that have the potential to fulfil the principles of the CE. Eighteen approaches related to prefabrication, design for change, design for deconstruction, reverse logistics, waste management and closed-loop systems were found. Through an analysis of the barriers that are common among these 18 approaches, we classified them into six different categories (organisational, economical, technical, social, political and environmental). Two Sankey diagrams illustrate the interrelation between the barriers, their categories and the 18 approaches. The diagrams clearly show that most of the barriers are common to multiple approaches and that most of the barriers relate to organisational concerns. The study gives a detailed map of the barriers that would help stakeholders from the AEC sector develop strategies to overcome the current obstacles in the shift to a CE.

This special issue provides an assessment of the contribution of soils to Nature's Contributions to People (NCP). Here, we combine this assessment and previously published relationships between NCP and delivery on the UN Sustainable Development Goals (SDGs) to infer contributions of soils to the SDGs. We show that in addition to contributing positively to the delivery of all NCP, soils also have a role in underpinning all SDGs. While highlighting the great potential of soils to contribute to sustainable development, it is recognized that poorly managed, degraded or polluted soils may contribute negatively to both NCP and SDGs. The positive contribution, however, cannot be taken for granted, and soils must be managed carefully to keep them healthy and capable of playing this vital role. A priority for soil management must include: (i) for healthy soils in natural ecosystems, protect them from conversion and degradation; (ii) for managed soils, manage in a way to protect and enhance soil biodiversity, health and sustainability and to prevent degradation; and (iii) for degraded soils, restore to full soil health. We have enough knowledge now to move forward with the implementation of best management practices to maintain and improve soil health. This analysis shows that this is not just desirable, it is essential if we are to meet the SDG targets by 2030 and achieve sustainable development more broadly in the decades to come. This article is part of the theme issue ‘The role of soils in delivering Nature's Contributions to People’.

The use and development of earth as a building material is notably constrained by its specific thermal and mechanical behaviours in relation to water, currently not considered in construction norms and technical guides. As the compressive strength decreases with the presence of water in pores, a good prediction of water content evolution within earthen walls is critical to ensure safety. The key parameter driving the flow of liquid water through the material is the intrinsic permeability. In this paper, a novel analysis of the water absorption test is developed, enabling thereby the identification of the intrinsic permeability. Through the comparison with permeability measurements made with an oedometer at a variable hydraulic load for samples with different dry densities, this new method could be validated. This work gives therefore the opportunity to use simple standard absorption tests to assess the intrinsic permeability of earthen materials.

Based on the RILEM Technical Committee 274-TCE work, this paper is a discussion of the remaining engineering challenges faced by earthen architecture. The assessment of earth material performances requires the development of appropriate procedures and standards. This is discussed in particular for the characterisation, hygrothermal behaviour, mechanical behaviour, and durability of earth materials. One other important challenge, since one of the main advantages classically put forward, is its ecological performance, is a proper assessment of life cycle assessment of earth materials, elements and buildings. Moreover, the paper develops why the approach to earthen construction must be different compared to the dominant construction materials, to preserve its ability to contribute to the ecological transition in the construction sector. In particular, the needs of using local soils, with an architectural approach coping with the limits of the materials, and developing an architectural optimisation to preserve the earthen materials multifunctionality rather than selecting a sole property to be maximised. Lastly, the findings of the paper can be used to develop a holistic approach to earthen construction to foster the development of new earthen architecture projects.

The need for a vast quantity of new buildings to address the increase in population and living standards is opposed to the need for tackling global warming and the decline in biodiversity. To overcome this twofold challenge, there is a need to move towards a more circular economy by widely using a combination of alternative low-carbon construction materials, alternative technologies and practices. Soils or earth were widely used by builders before World War II, as a primary resource to manufacture materials and structures of vernacular architecture. Centuries of empirical practices have led to a variety of techniques to implement earth, known as rammed earth, cob and adobe masonry among others. Earth refers to local soil with a variable composition but at least containing a small percentage of clay that would simply solidify by drying without any baking. This paper discusses why and how earth naturally embeds high-tech properties for sustainable construction. Then the potential of earth to contribute to addressing the global challenge of modern architecture and the need to re-think building practices is also explored. The current obstacles against the development of earthen architecture are examined through a survey of current earth building practitioners in Western Europe. A literature review revealed that, surprisingly, only technical barriers are being addressed by the scientific community; two-thirds of the actual barriers identified by the interviewees are not within the technical field and are almost entirely neglected in the scientific literature, which may explain why earthen architecture is still a niche market despite embodying all the attributes of the best construction material to tackle the current climate and economic crisis. This article is part of the theme issue ‘The role of soils in delivering Nature's Contributions to People’.

Past builders have developed very low-embodied energy construction techniques optimizing the use of local building materials. These techniques are a source of inspiration for modern sustainable building. Unfortunately, this know-how was orally transmitted and was lost as earth construction fell into disuse during the 20th century in European countries. The absence of written documents makes necessary to use an archaeological approach in order to rediscover these construction strategies. Micromorphological analysis of thin sections collected in earth building walls was used for the first time to describe cob construction technique and highlighted several typical pedofeatures allowing to clearly identifying this process. Finally, a first comparison of the cob and rammed earth micromorphological features permitted to identify two key factors to distinguish these two techniques, the manufacturing state (solid or plastic) and the organization of the material in the wall. Keywords: Cob, Rammed earth, Micromorphology, Architectural heritage, Pedology

Dry stone masonry is a widespread building technique, which has been used in Europe and all around the world in both monumental and vernacular architecture. Amongst them, dry stone structures retaining slopes have received growing attention over the past two decades, but only a few studies concentrate on the influence of localised loading upon the backfill. This paper describes an experimental campaign, comprising two tests on full-scale structures, which has been undertaken in France in order to investigate the behaviour of dry stone road retaining walls. The results of these tests are compared with those of a previous experimental campaign, and of a theoretical approach.

This chapter introduces the case of the earthen constructions including most of the techniques used in the vernacular heritage and the modern green building architecture. It starts by presenting the variety of earth building techniques focusing on the common points between all of them. It then explains these particularities which are linked to the affinity with water of the earthen material and construction. This leads to a specific hygrothermal and mechanical behavior of the materials and structures. The impact of these characteristics on building design is given. A full discussion of the case of earth stabilization is then included to show their relationship with the gain (or loss) obtained in the framework of the sustainability. By the end of the chapter, an assessment of the hygrothermal, mechanical, and durability performance is proposed.

The construction sector is the largest consumer of raw materials and accounts for 25%–40% of the total CO2 emissions globally. Besides, construction activities produce the highest amount of waste among all other sectors. According to the waste hierarchies, reuse is preferred to recycling; however, most of the recovery of construction and demolition wastes happens in the form of recycling and not reuse. Part of the recent efforts to promote the reuse rates includes estimating the reusability of the load-bearing building components to assist the stakeholders in making sound judgements of the reuse potentials at the end-of-life of a building and alleviate the uncertainties and perceived risks. This study aims to develop a probabilistic model using advanced supervised machine learning techniques (including random forest, K-Nearest Neighbours algorithm, Gaussian process, and support vector machine) to predict the reuse potential of structural elements at the end-of-life of a building. For this purpose, using an online questionnaire, this paper seeks the experts’ opinions with actual reuse experience in the building sector to assess the identified barriers by the authors in an earlier study. Furthermore, the results of the survey are used to develop an easy-to-understand learner for assessing the technical reusability of the structural elements at the end-of-life of a building. The results indicate that the most significant factors affecting the reuse of building structural components are design-related including, matching the design of the new building with the strength of the recovered element.

In the global will of reducing fossil energy consumption and greenhouse gas emission in the building sector, the use of bio-based insulating materials is gaining interest thanks to their profitable properties and their suitability for the renovation of ancient buildings made out of unconventional materials. However, such materials are still lacking of characterization, and more precisely of on-site evaluation, as no complete measurement protocol is available. The starting point to fill this gap would be to set-up a protocol for whole building instrumentation, and this paper is investigating questions arisen in that goal, and more precisely regarding the impact of sensor locations on the assessment of key parameters. For that purpose, instrumented polystyrene and hemp concrete wallets of dimensions 0.9 × 0.9 × 0.1 m3 with well-known thermal and hydric characteristics are tested within a double climatic chamber. The impact of temperature sensor locations and implementations are tested through indirect estimation of the thermal conductivities of the materials composing the wallets. The effect of the hygrothermal processes on the measurement of thermal performance is also investigated through the analysis of the wall global transmittance. These results finally allow to provide some recommendations concerning the on-site instrumentation of hemp concrete walls.

Based on TopSolid applications, the enriched CAD solution allows end users to simulate the necessary operations to apply on the part for tape laying processes. It helps to generate the tool paths for the texturing and for the tape layout deposition on complex parts. Based on the CAD simulations, the enriched CAM simulate and generate the NC code to pilot the robots into the cell for the production line.&nbsp

Rammed earth is one of the most prominent earthen building materials, which is an in situ construction technique. Replicating in situ technique to build laboratory specimens is always a challenging procedure. Proctor method is one of the closest controlled techniques to replicate in situ rammed earth fabrication methodology in preparation of laboratorial specimens. This work attempts to understand the influence of Proctor method of manufacturing specimens on examining the compressive strength and stress–strain characteristics of unstabilised rammed earth (USRE). The results from two soils show good correlation of compressive strength with respect to compaction energy. The stiffness degradation of USRE calculated with the help of loading and unloading cycles is also discussed.

Rammed earth is a monolith structure constructed by compacting partially saturated soil in layers within a formwork. Few studies have pointed out the lack of experimental data on rammed earth layer interface strength and their importance in design consideration. Currently available testing procedures such as shear box, triaxial, triplet, push-over and diagonal compression tests have their own limitations, mainly their cost, which make them unlikely to become a standard procedure. This paper introduces a wedge tool technique to explore interface shear strength properties with ease. Three pairs of metallic wedges with different testing inclination angles (45, 30 and 20°) were designed and tested for two soils. Specimens tested at these inclinations provide a combination of shear and normal stress acting on the interface. Tests on two different soils showed that the new device can measure cohesion and the angle of internal friction with a correlation coefficient higher than 0·8; the results were found to be consistent with values classically obtained for these kinds of materials. The indirect shear test procedure developed is a robust way of measuring shear parameters while being simpler and less expensive than existing devices.

Earthen buildings can provide an answer to face difficulties in modern constructions in both terms of sociology, economics as well as ecology. However, the difficulty to understand and to predict their long term behavior represents an obstacle to their spreading. In some cases for example, unsuitable repairs on old constructions can lead to catastrophic situations. More specifically, during their lifetime, earthen walls have to face important variations of indoor and outdoor relative humidity, which induces variations and gradients in their water content. In this context, this paper aims at addressing an important aspect, not yet fully understood: the impact of these variations on the deformability and the strength of unstabilized earth. To that purpose, unconfined compression tests, with and without unload–reload cycles, were performed on different compacted earth samples conditioned at different relative humidities. Tested samples were prepared from materials coming from different existing constructions and sieved at 10 mm. During the tests, the axial and radial strains were measured using non-contact sensors and an image correlation system. This study shows that earthen materials have a complex mechanical behavior, involving the phenomena of plastic straining and mechanical damage. Moreover, both of these phenomena show a strong dependence on the relative humidity at which the samples were stored, as well as on the activity of the clayey portion of the earth.

The goal of this paper is to identify the effects of in-pore transport of liquid water and water vapor as well as phase changes on the hygrothermal behavior of earthen buildings. Indeed, one of the main assets used to promote these constructions is their role in moisture buffering hence temperature and relative-humidity quality controlling. However, there is no clear consensus yet concerning the impact of these phenomena on the global energy performance of the buildings. A coupled model is therefore proposed in this paper, based on heat and mass balances inside the earthen walls, in order to clarify this question. This model considers separately the kinematics of each phase (e.g. liquid water, vapor, dry air and solid matrix), in interaction with each other. It also takes into account the impact of pore water confinement on the liquid-to-vapor phase change, in particular on the resulting latent heat released or absorbed. The model is successfully compared to experimental results on instrumented full-scale rammed earth wall subjected to temperature cycles. It eventually allows identifying the singular hygrothermal behavior of earth material by testing the range of applicability of the simplifying assumptions which are commonly made in function of the permeability of the tested material.

WOS:000379589500010; International audience; In developing countries, most of the population cannot afford conventional building blocks made with the sand-cement mixture. In addition, these blocks do not provide thermal comfort and have a high embodied energy compared to vernacular materials. The main objective of this work was to produce low cost, resistant and durable (good resistance to water) blocks with a thermal behaviour enabling quality comfort indoor. For that purpose, the effects of cow-dung on microstructural changes in earth blocks (adobes) are investigated by means of X-ray diffraction, thermal gravimetric analyses, scanning electronic microscopy coupled with energy dispersive spectrometry, and video microscopy. The effects of these changes on the physical properties (water absorption and linear shrinkage) and mechanical properties (flexural and compressive strengths) of adobe blocks are evaluated. It is shown that cow-dung reacts with kaolinite and fine quartz to produce insoluble silicate amine, which glues the isolated soil particles together. Moreover, the significant presence of fibres in cow-dung prevents the propagation of cracks in the adobes and thus reinforces the material. The above phenomena make the adobe microstructure homogeneous with an apparent reduction of the porosity. The major effect of cow-dung additions is a significant improvement in the water resistance of adobe, which leads to the conclusion that adobes stabilized by cow-dung are suitable as building materials in wet climates.

An upper-bound solution for stone-facing embankments is developed to assess the stability of this type of structures. The embankment is treated as a cohesionless granular material whereas the facing is considered as composed of discrete stone blocks, laid dry one on the top of the other, complying with a Mohr-Coulomb interface law. This enables the assessment of the stability of the structure, solely resorting to its geometry, unit weight, and the friction angles of the embankment and facings. The model is finally used to assess the stability of an existing rockfill dam in the Pyrénées (France). Comparison with Distinct Element Method results and parametric analyses prove the robustness of the model on this case study.

Using in-situ soils for building constructions is attractive in the sustainable development because these materials have low embodied energy and present an interesting hygro-thermal behavior. Several researches have been recently carried out to study soil materials. However, the variability of soil characteristics on each construction site makes that the use of an unique construction technique (soil concrete, rammed earth, adobe, …) becomes difficult to satisfy several exigencies of the modern regulations (mechanical, thermal performances, durability and earthquake resistance), and the economic criterion. This paper introduces firstly a strategy which can facilitate the use of in-situ soils for building constructions. Relevant techniques corresponding to several in-situ soil types are proposed. Then, the application of the proposed approach is showed with a case study on a building project using a soil concrete. Several aspects are investigated: material optimization, architectural design, structural-thermal performances and life cycle analysis.

Earth building is experiencing a renaissance due to the emerging recognition of the damage the construction industry is doing to the global environment. Research over the past three decades has identified the hygroscopic nature of these materials, and our understanding of the factors governing their hydromechanical properties is now mature. However, little work has been done to unify methods to assess material durability: namely, how exposure to degrading agents, predominantly water, impacts a structure’s service life. Although strength is usually of primary concern to engineers, it is undeniable that earthen structures usually fail due to durability, rather than strength, issues. As earthen architecture and demands made of the material become more ambitious, the need for robust guidelines on how to predict the longevity of these structures becomes paramount. This paper presents a framework for assessing the durability of earthen materials based on perceived routes of exposure to water. The framework is built upon the findings of a review of nearly 60 articles discussing original durability testing programmes, comprising 118 investigations and almost 700 soil and stabiliser combinations. From these works, 12 assessment methodologies were identified, encompassing a range of earthen construction techniques, e.g. mud brick, compressed earth blocks and rammed earth. Each method is described and its suitability for assessing the real world durability of a range of earthen construction techniques appraised. From this, the efficacy of each test was determined and a shortlist of suitable tests created. The derived framework provides assessors with a method to determine likely exposure routes for an earthen construction element (e.g. an internal or external wall) and, from the shortlisted methods, to specify the range of tests necessary to ensure suitable durability given the construction and environmental conditions. This work forms part of the update to the Standards Australia Earth Building Handbook: SA HB 195.

After being almost abandoned at the end of the Second World War, the use of raw earth is currently regaining the interest of architects, engineers and policy makers for the construction of dwellings in industrialised countries. This renaissance is driven by growing ecological awareness and the promotion of construction techniques that minimize energy consumption and carbon emissions. Raw earth displays very interesting thermo-hygro-mechanical properties, which can contribute to the reduction of the environmental impact of buildings not only during construction but also during service life. Nevertheless, one of the reasons that still prevents dissemination of raw earth into construction practice is the lack of commonly agreed procedures for assessing material performance. The RILEM technical committee TCE 274 has been established as a first step for overcoming this obstacle. The objective of the technical committee is to critically examine current testing procedures in order to propose suitable experimental standards. The results of this work will be presented in future publications while the present paper summarizes the main challenges faced by the committee and briefly describes some of the existing procedures for measuring the engineering properties of earth materials.

ISI Document Delivery No.: GE4BB Times Cited: 0 Cited Reference Count: 58 Hamard, Erwan Lemercier, Blandine Cazacliu, Bogdan Razakamanantsoa, Andry Morel, Jean-Claude Elsevier sci ltd Oxford; A new methodology based on the cross-referencing of spatialized pedological and heritage data is proposed to identify and quantify soil resources available for earth construction. The paper underlines the pedological particularities of areas containing earth heritage and uses these particularities to propose criteria to assess the suitability of soils for modern earth construction. The methodology applied at the regional scale in France (for a given area of 27,200 km2 in Brittany) enabled to specify five new texture classes (balance between clay, silt, sand and gravel content) of suitability for cob soils. This result calls into question recommendations available in the literature. The methodology also provides data on the scale of availability of the resource to repair earth built heritage (cob) or to build new low impact buildings with integrated modern cob walls. In the studied area the potential waste recovery of 2.8 Mt per year is measured, highlighting the large availability of materials for earth construction. At least 23% of earthwork wastes of Brittany are suitable for earth construction (0.7 Mt). However, earth remains a non-renewable material and this resource has to be properly managed, requiring an appropriate building design and maintenance in order to increase longevity and to avoid the use of admixture, preventing earth reversibility at end of life.

Summary The dry-stone retaining walls (DSRW) have been tipped as a promising solution for sustainable development. However, before recently, their behavior is relatively obscure. In this study, discrete element method (DEM) approach was applied to simulate the plane strain failure of these walls. A commercial DEM package (PFC2D™) was used throughout this study. The authors used a fully discrete approach; thus, both the wall and the backfill were modeled as discrete elements. The methodology for obtaining the micromechanical parameters was discussed in detail; this includes the three mechanical sub-systems of DSRWs: wall, backfill and interface. The models were loaded progressively until failure, and then the results were compared with the full-scale experimental results where the walls were loaded, respectively, with hydrostatic load and backfill. Despite its complexity and its intensive calculation time, DEM model can then be used to validate a more simplified approach. Copyright © 2015 John Wiley & Sons, Ltd.

The experimental determination of dynamic mass transfer properties of porous materials such as eco-efficient clay plasters is greatly influenced by the convective conditions at the surface of the material during the test. The measurement of the intrinsic vapour permeability of highly porous materials has shown to present wide discrepancies when the surface film resistance is not known. Therefore, a proper assessment of the hygric properties of clay plasters requires the determination of such resistance to vapour flow. An adapted experimental procedure was used to determine intrinsic water vapour permeability taking into account the influence of the surface film resistance. The moisture buffering test was used to measure dynamic exchange behaviour. The results gave evidence on the thickness of the active layer in the material and the impact of surface resistance on the exchange behaviour. A 1D mass transfer model was used to verify the validity of corrected vapour permeability by the surface film resistance and discuss its nature and influence on dynamic results.

Rammed earth (RE) is attracting renewed interest throughout the world thanks to its “green” characteristics in the context of sustainable building. In this study, the ageing effects on RE material are studied on the walls which have been constructed and exposed for 22 years to natural weathering. First, mechanical characteristics of the “old” walls were determined by two approaches: in-situ dynamic measurements on the walls; laboratory tests on specimens which had been cut from the walls. Then, the walls’ soil was recycled and reused for manufacturing of new specimens which represented the initial state. Comparison between the compressive strength, the Young modulus of the walls after 22 years on site and that of the initial state enables to assess the ageing of the studied walls.

Drystone walls are durable structures, owing to their intrinsic ductility, permeability, and the strength of the materials used. Nevertheless, they can be subject to slow deterioration, caused by weathering of the materials, by the application of loads for which they were not designed, by impact, or by inappropriate repair methods. It is then necessary to assess the condition of the structure, and to repair or to replace the construction. This paper aims to bring together advances on drystone retaining walls made by researchers in France and the UK over the last two decades. Three methods that are used to evaluate the stability of drystone retaining walls are summarised and compared: the distinct element method, limit equilibrium analysis and yield design analysis. The first proves to be most suited to back-analysis, while the second and third methods may also be used for design. The paper describes the use of design charts, an example of which is presented. These charts were based on the understanding obtained from these models, which has now been confirmed by full-scale testing.

Rammed earth is a sustainable material with low embodied energy. However, its development as a building material requires a better evaluation of its moisture-thermal buffering abilities and its mechanical behavior. Both of these properties are known to strongly depend on the amount of water contained in wall pores and its evolution. Thus the aim of this paper is to present a procedure to measure this key parameter in rammed earth or cob walls by using two types of probes operating on the Time Domain Reflectometry (TDR) principle. A calibration procedure for the probes requiring solely four parameters is described. This calibration procedure is then used to monitor the hygrothermal behavior of a rammed earth wall (1.5 m × 1 m × 0.5 m), instrumented by six probes during its manufacture, and submitted to insulated, natural convection and forced convection conditions. These measurements underline the robustness of the calibration procedure over a large range of water content, even if the wall is submitted to quite important temperature variations. They also emphasize the importance of gravity on water content heterogeneity when the saturation is high, as well as the role of liquid-to-vapor phase change on the thermal behavior.

In this paper, influence of moisture content on the mechanical characteristics of rammed-earth has been studied. Samples from different soils (sandy, clayey, stabilised) were manufactured and tested in unconfined compression at several moisture contents. Compressive strength, elastic modulus and Poisson's ratio were determined. A simplified method to measure the suction within rammed earth samples has been developed and validated. The variation of mechanical characteristics related to moisture content and suction are presented. This paper shows that a slight increase in the moisture content of dry rammed-earth is not followed by sudden drop in wall strength. Qualitative explanations at the nano-scale are presented.

International audience; This study presents an analysis of dry masonry retaining structures based on yield design theory: the structure stability is assessed using rigid block and shear failure mechanisms in the wall and its backfill. An application of this simulation on 2D scale-down brick and wood models is then addressed, showing close agreement between theoretical predictions and experimental results. Finally, the possibility of widespreading the study to periodic dry joint and dry-stone retaining structures is discussed.