The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Daniela Ciancio - One of the best experts on this subject based on the ideXlab platform.
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weathering s beneficial effect on waste stabilised Rammed Earth a chemical and microstructural investigation
Construction and Building Materials, 2017Co-Authors: Alessandro Arrigoni, Chris Beckett, Renato Pelosato, Giovanni Dotelli, Daniela CiancioAbstract:The most common method to improve the mechanical properties of a Rammed Earth mix is to add chemical stabilisers like cement and/or lime. Varying the stabiliser type will affect strength gain but also the environmental impact. In this paper, the effect of wetting-drying cycles on the long-term unconfined compressive strength of stabilised Rammed Earth (SRE) mixes was investigated through the chemical characterisation of the soil components and microstructural analyses. The mixes were stabilised using different agents characterised by distinct environmental impacts, such as cement, calcium carbide residue and fly ash. These last two are considered waste materials, significantly affecting their use's associated environmental implications. The results of this experimental campaign support others in this series of work and showed an improvement of the mechanical properties after cyclic wetting-drying due to the formation of new hydration products which bound particles together. The use of waste materials proved to be an effective solution to stabilise RE.
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reduction of Rammed Earth s hygroscopic performance under stabilisation an experimental investigation
Building and Environment, 2017Co-Authors: Alessandro Arrigoni, Chris Beckett, Monika Woloszyn, Anne-cécile Grillet, Renato Pelosato, Giovanni Dotelli, Daniela CiancioAbstract:One of the acknowledged qualities of Rammed Earth (RE) is its moisture buffering capacity. Recently, stabilisation of RE has become a common practice to improve the mechanical resistance but very little is known about the effect that stabilisation has on hygroscopic properties. The present study aims to fill this gap by understanding the role that stabilisation plays in the buffering and sorption capacity of RE. The use of alternative stabilisers such as fly ash and calcium carbide residue and a comparison with traditional unstabilised RE (URE) have also been investigated. Moreover, the effect of weathering, simulated by cyclic wetting-drying, on hygroscopic performance has been analysed. Moisture Buffer Value (MBV) testing, moisture and nitrogen adsorption-desorption isotherms and mercury intrusion porosimetry were performed on stabilised samples to examine microstructural phenomena responsible for behavioural changes. URE was confirmed to be a good-to-excellent passive air conditioner according to the MBV scale but its performance seemed to be highly influenced by the soil particle size distribution and mineralogy. Based on the experimental outcomes of the mixtures investigated, stabilisation had a detrimental effect on the moisture buffer capacity of Rammed Earth, likely due to the inhibition of the physico-chemical interactivity between moisture and clays. Weathering had a variable effect on the buffering capacity, depending on the availability of unreacted particles in the matrix.
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optimum lime content identification for lime stabilised Rammed Earth
Construction and Building Materials, 2014Co-Authors: Daniela Ciancio, Chris Beckett, J. Antonio H. CarraroAbstract:Abstract The rising price of energy and a recognition of the human impact on climate change has resulted in growing interest in environmentally–friendly construction techniques such as Rammed Earth. Modern Rammed Earth is generally stabilised with small quantities of Portland cement in order to improve its strength and durability, however an alternative is to use lime to stabilise the raw soil. This is common practice in road construction, for example, but is less common in RE. This paper presents experimental results illustrating the existence of an optimum lime content that maximises the unconfined compressive strength and stiffness of an engineered lime-stabilised Rammed Earth and the experimental procedures employed to determine it. The effect of curing regime (oven as opposed to natural drying) on the final unconfined compressive strength of the material was also investigated. An optimum lime content for the tested soil has been identified and several methods to determine its rough value presented which have the potential to reduce testing times and so associated costs.
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effect of compaction water content on the strength of cement stabilized Rammed Earth materials
Canadian Geotechnical Journal, 2014Co-Authors: Chris Beckett, Daniela CiancioAbstract:Current guidelines suggest that stabilized Rammed Earth materials be compacted at their optimum water content to achieve their maximum strength. Although this is true for traditional Rammed Earth, ...
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advances on the assessment of soil suitability for Rammed Earth
Construction and Building Materials, 2013Co-Authors: Daniela Ciancio, Paul Jaquin, Peter WalkerAbstract:A soil grading curve is one of the most useful tools to assess the suitability of material for Rammed Earth construction. Different and sometimes contradictory proportions of clay, silt, sand and gravel are proposed for Rammed Earth soils. This paper investigates the reliability of current guideline values through comparative performance testing of Rammed Earth specimens. Ten artificial soil batches (five of them stabilised with cement and/or lime) deemed suitable for Rammed Earth according to the current guidelines were tested in terms of compressive strength, shrinkage and erosion. The investigation shows that complying with soil particle size distribution criteria does not alone necessarily mean suitability of a soil for Rammed Earth. Based on these results, this paper proposes recommendations and criteria to be implemented in the assessment of soil for Rammed Earth.
Chris Beckett - One of the best experts on this subject based on the ideXlab platform.
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alternative stabilised Rammed Earth materials incorporating recycled waste and industrial by products a study of mechanical properties flexure and bond strength
Construction and Building Materials, 2021Co-Authors: Alexandra H Meek, Chris Beckett, Mohamed Elchalakani, Minhao DongAbstract:Abstract Developing low-embodied energy building materials can significantly contribute to reducing global greenhouse gas emissions. However, these new building materials must be properly understood before they can or will be adopted by the construction industry. Rammed Earth materials with low greenhouse gas emissions have been developed based on the principles of alkali-activated stabilisation as replacements for conventional construction materials. In previous work by the authors, the strength development, durability and sustainability, via life cycle assessment, of these new materials have already been studied. However, how these materials interact with and affect embedded reinforcement is poorly understood, as are methods to test these properties. Their applicability in modern construction is therefore currently limited. This paper extends the understanding of these materials through flexural and push-out testing of specimens reinforced with steel and glass-fibre reinforced polymer bars. We determine mechanical properties of the alternatively-stabilised Rammed Earth materials and study the composite behaviour of the reinforced materials. The suitability of current testing standards for elastic modulus, Poisson’s ratio, and indirect tensile, bond, shear and flexural strengths, originally designed for concrete specimens, were evaluated for RE materials. These were compared with design rules and predictions made using concrete standard AS 3600 and Rammed Earth standards (NZS 4297-4299), handbook (HB 195) and Rammed Earth and concrete literature. Results showed that existing testing procedures specified for concrete specimens were appropriate for estimating Poisson’s ratio and shear modulus as well as for determining flexural and shear strengths for Rammed Earth. Existing Rammed Earth recommendations given in NZS 4297 for estimating elastic modulus should continue to be followed. An alternative compressive reinforcement bond test, similar to RILEM AAC 8.2 push-out standard for autoclaved aerated concrete, was proposed; however, more work is required to establish a better prediction model for bond strength. Results indicated that current expressions to relate indirect tensile to unconfined compressive strength are suitable for compressive strengths up to 20 MPa.
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reinforcement corrosion in cement and alternatively stabilised Rammed Earth materials
Construction and Building Materials, 2021Co-Authors: Alexandra H Meek, Chris Beckett, Mohamed ElchalakaniAbstract:Abstract Developing low-embodied energy building materials can significantly contribute to reducing global greenhouse gas emissions. However, these new building materials must be properly understood before they can or will be adopted by the construction industry. In this paper, we examine the corrosion of reinforcement embedded within Rammed Earth materials in both atmospheric and accelerated carbonation conditions. Six Rammed Earth materials with alternative stabilisers to cement were studied – three stabilisers combined with a substrate of either crushed limestone or recycled brick and concrete – and contrasted against cement-stabilised crushed limestone. The stabilisers included industrial by-products fly ash, ground granulated blast furnace slag and silica fume, combined with sodium hydroxide or hydrated lime as activators, or with no activator, to form alkali-, lime- and self-activated Rammed Earth, respectively. Likelihood of reinforcement corrosion was assessed via changes in reinforcement half-cell potential and matrix carbonation. Half-cell potential results for four cement-stabilised Rammed Earth mixes that underwent accelerated carbonation showed that while uncarbonated cement-stabilised Rammed Earth protected steel from corrosion, once carbonated, the electrochemical behaviour was distinctly different and reinforcement was found to corrode. Self-activated Rammed Earth carbonated fully within 29 weeks. Carbonation rates of alkali- and lime-activated Rammed Earth were sufficiently slow that the carbonation front would not reach reinforcement with a typical cover depth of 150 mm over a typical 50 year design life. However, the carbonation front will likely breach a cover of 50 mm in that time. Electrochemical half-cell potential measurements of alkali-activated Rammed Earth were similar for both accelerated carbonation specimens and those only exposed to atmospheric conditions. Alternative Rammed Earth materials equilibrated to atmospheric moisture and CO2 levels gave half-cell potential readings above -200 mV SCE: a value previously shown to be indicative of a negligible corrosion rate in cement-stabilised RE. However, destructive testing revealed that reinforcement embedded in all specimens was corroded, i.e. this value is not indicative of negligible corrosion in these materials. Results therefore indicate that mild steel should not be used in RE materials not containing cement. Rather, galvanised, stainless steel or fibre reinforced polymer reinforcements should be used to avoid reduction in service life due to corrosion.
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weathering s beneficial effect on waste stabilised Rammed Earth a chemical and microstructural investigation
Construction and Building Materials, 2017Co-Authors: Alessandro Arrigoni, Chris Beckett, Renato Pelosato, Giovanni Dotelli, Daniela CiancioAbstract:The most common method to improve the mechanical properties of a Rammed Earth mix is to add chemical stabilisers like cement and/or lime. Varying the stabiliser type will affect strength gain but also the environmental impact. In this paper, the effect of wetting-drying cycles on the long-term unconfined compressive strength of stabilised Rammed Earth (SRE) mixes was investigated through the chemical characterisation of the soil components and microstructural analyses. The mixes were stabilised using different agents characterised by distinct environmental impacts, such as cement, calcium carbide residue and fly ash. These last two are considered waste materials, significantly affecting their use's associated environmental implications. The results of this experimental campaign support others in this series of work and showed an improvement of the mechanical properties after cyclic wetting-drying due to the formation of new hydration products which bound particles together. The use of waste materials proved to be an effective solution to stabilise RE.
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reduction of Rammed Earth s hygroscopic performance under stabilisation an experimental investigation
Building and Environment, 2017Co-Authors: Alessandro Arrigoni, Chris Beckett, Monika Woloszyn, Anne-cécile Grillet, Renato Pelosato, Giovanni Dotelli, Daniela CiancioAbstract:One of the acknowledged qualities of Rammed Earth (RE) is its moisture buffering capacity. Recently, stabilisation of RE has become a common practice to improve the mechanical resistance but very little is known about the effect that stabilisation has on hygroscopic properties. The present study aims to fill this gap by understanding the role that stabilisation plays in the buffering and sorption capacity of RE. The use of alternative stabilisers such as fly ash and calcium carbide residue and a comparison with traditional unstabilised RE (URE) have also been investigated. Moreover, the effect of weathering, simulated by cyclic wetting-drying, on hygroscopic performance has been analysed. Moisture Buffer Value (MBV) testing, moisture and nitrogen adsorption-desorption isotherms and mercury intrusion porosimetry were performed on stabilised samples to examine microstructural phenomena responsible for behavioural changes. URE was confirmed to be a good-to-excellent passive air conditioner according to the MBV scale but its performance seemed to be highly influenced by the soil particle size distribution and mineralogy. Based on the experimental outcomes of the mixtures investigated, stabilisation had a detrimental effect on the moisture buffer capacity of Rammed Earth, likely due to the inhibition of the physico-chemical interactivity between moisture and clays. Weathering had a variable effect on the buffering capacity, depending on the availability of unreacted particles in the matrix.
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optimum lime content identification for lime stabilised Rammed Earth
Construction and Building Materials, 2014Co-Authors: Daniela Ciancio, Chris Beckett, J. Antonio H. CarraroAbstract:Abstract The rising price of energy and a recognition of the human impact on climate change has resulted in growing interest in environmentally–friendly construction techniques such as Rammed Earth. Modern Rammed Earth is generally stabilised with small quantities of Portland cement in order to improve its strength and durability, however an alternative is to use lime to stabilise the raw soil. This is common practice in road construction, for example, but is less common in RE. This paper presents experimental results illustrating the existence of an optimum lime content that maximises the unconfined compressive strength and stiffness of an engineered lime-stabilised Rammed Earth and the experimental procedures employed to determine it. The effect of curing regime (oven as opposed to natural drying) on the final unconfined compressive strength of the material was also investigated. An optimum lime content for the tested soil has been identified and several methods to determine its rough value presented which have the potential to reduce testing times and so associated costs.
Q. B. Bui - One of the best experts on this subject based on the ideXlab platform.
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characterizing the shear parameters of Rammed Earth material by using a full scale direct shear box
Construction and Building Materials, 2018Co-Authors: R Elnabouch, Q. B. Bui, Olivier Ple, Pascal PerrotinAbstract:Abstract Rammed Earth (RE) is one of the different techniques of Earth constructions. The RE wall is built by compacting the soil in a formwork, layer after layer (about 10–15 cm thick for each layer). RE buildings are recognized for their very low embodied energy and their positive hygrothermal behaviour. Several recent studies have investigated RE material and among different aspects, the seismic performance remains an interesting topic that needs to be explored. In order to propose a robust model for seismic investigation, the shear characteristics of RE material should be appropriately determined. These shear characteristics include the cohesion, the friction angle of the intralayers and also the cohesion, the friction angle of the interlayers (between the layers) as a RE wall contains multilayers. However, few studies have directly identified these parameters by experiments. This is the first time, to our knowledge, that a full-scale shear box (0.5 m width × 0.5 m length × 0.45 m height) was specifically developed to study the shear parameters of the Rammed Earth. This full-scale shear box was designed to reproduce the manufacturing conditions of a current Rammed Earth wall in Europe (50-cm-thickness). Direct shear tests were performed both for intralayers and interlayers. The results showed that the shear strength obtained at the interlayers were about 80–90% of the corresponding values obtained at the intralayers. Finally, the influences of the moisture content and the size effect on the obtained results were also discussed.
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Modeling Rammed Earth wall using discrete element method
Continuum Mechanics and Thermodynamics, 2016Co-Authors: T. T. Bui, Q. B. Bui, Ali Limam, J. C. MorelAbstract:Rammed Earth is attracting renewed interest throughout the world thanks to its "green" characteristics in the context of sustainable development. Several research studies have thus recently been carried out to investigate this material. Some of them attempted to simulate the Rammed Earth's mechanical behavior by using analytical or numerical models. Most of these studies assumed that there was a perfect cohesion at the interface between Earthen layers. This hypothesis proved to be acceptable for the case of vertical loading, but it could be questionable for horizontal loading. To address this problem, discrete element modeling seems to be relevant to simulate a Rammed Earth wall. To our knowledge, no research has been conducted thus far using discrete element modeling to study a Rammed Earth wall. This paper presents an assessment of the discrete element modeling's robustness for Rammed Earth walls. Firstly, a brief description of the discrete element modeling is presented. Then the parameters necessary for discrete element modeling of the material law of the Earthen layers and their interfaces law following the Mohr-Coulomb model with a tension cut-off and post-peak softening were given. The relevance of the model and the material parameters were assessed by comparing them with experimental results from the literature. The results showed that, in the case of vertical loading, interfaces did not have an important effect. In the case of diagonal loading, model with interfaces produced better results. Interface characteristics can vary from 85 to 100% of the corresponding Earthen layer's characteristics.
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effect of moisture content on the mechanical characteristics of Rammed Earth
Construction and Building Materials, 2014Co-Authors: Q. B. Bui, Jean Claude Morel, Stephane Hans, Peter WalkerAbstract:Abstract 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.
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first exploratory study on dynamic characteristics of Rammed Earth buildings
Engineering Structures, 2011Co-Authors: Q. B. Bui, Stephane Hans, Jean Claude MorelAbstract:Abstract Rammed Earth construction is attracting a renewed interest throughout the world thanks to its “green” characteristics in the context of sustainable development. Several studies have been carried out to investigate this material and evaluate its durability along with its mechanical, thermal and Earthquake capacities. This paper presents a study on the parameters needed for the seismic design of Rammed Earth buildings in accordance with current Earthquake standards. First, the dynamic parameters of buildings such as natural frequencies and damping ratios–which were necessary to determine the equivalent static seismic force–were identified using in-situ dynamic measurements. Then, these experimental values were compared with the values calculated by empirical formulas suggested in Eurocode 8 to demonstrate that these formulas were applicable for the cases of Rammed Earth structures. Then, modeling was done to find a simple suitable model for Rammed Earth structures. Laboratory experiments were developed to measure the Poisson’s ratio which was necessary for the models. The results provided by the shear-beam model were close to that of in-situ experiments, which showed a shearing behavior of Rammed Earth structures. Elements which influenced the dynamic behavior of this structural type were also discussed. Understanding the dynamic characteristics of Rammed Earth structures will help engineers in their design of new Rammed Earth buildings but also in Earthquake analyses of existing Rammed Earth buildings.
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assessing the anisotropy of Rammed Earth
Construction and Building Materials, 2009Co-Authors: Q. B. Bui, Jean Claude MorelAbstract:Rammed Earth construction is an ancient technique that is attracting renewed interest throughout the world today. Since it is carried out by stacking layers of Rammed Earth, it is possible that the Rammed Earth material is anisotropic. This paper presents the first study of this anisotropy, carried out on two scales. The first is the scale of Representative Volume Elements (RVEs) of the Rammed Earth material, with dimensions close to those of the walls on site, manufactured and tested in the laboratory. The second is the microscopic scale, for which tests were carried out on equivalent Compressed Earth Blocks (CEBs). A conventional homogenization procedure was carried out to determine the relationships of the microscopic scale and the RVE scale. The compressive strengths, elasticity moduli and failure moduli are similar in both directions of the material: perpendicular and parallel to the layers. The sum of these results allows us to propose the hypothesis that the Rammed Earth material is an isotropic material of the first order, if the layers remain adherent to each other.
Jean Claude Morel - One of the best experts on this subject based on the ideXlab platform.
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Energy evaluation of Rammed Earth walls using long term in-situ measurements
Solar Energy, 2017Co-Authors: Lucile Soudani, Antonin Fabbri, Jean Claude Morel, Monika Woloszyn, Anne-cécile GrilletAbstract:Abstract Available throughout the world and used in construction for thousand years, Earthen materials are known to improve indoor air quality while keeping the internal temperature relatively stable. In Rhone-Alpes, France, the Rammed Earth technic is the most spread and consists in compacting layers of Earth, one by one, within a framework. Current thermal standards, which are mainly based on thermal resistance of the material, urge to insulate walls. However, due to its interaction with its environment, and its couplings between heat and moisture transfers, the observed thermal behaviour of uninsulated Rammed Earth can be above the expectations. The objective of the paper is to highlight the living comfort provided by non-insulated Rammed Earth walls, for different orientations, from in-situ measurements performed over more than two years. Winter, with low energy use for heating, and summer, with no cooling device, are studied. The study points out the important role of solar irradiance on the thermal balance of the house, and thus the importance of a good architecture.
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Historical Rammed Earth process description thanks to micromorphological analysis
International Journal of Architectural Heritage, 2016Co-Authors: Erwan Hamard, Antonin Fabbri, Cécilia Cammas, Andry Razakamanantsoa, Bogdan Cazacliu, Jean Claude MorelAbstract:Rammed Earth was traditionally used in western European countries before industrial building materials replace it during 20th Century. Construction strategies developed by former builders were dictated by locally available construction materials and engendered local constructive cultures. Unfortunately, this knowledge was orally transmitted and is lost today. The rediscovery of these cultures can provide answers to modern Rammed Earth construction processes. Micromorphological analysis of Earth walls provides information to rediscover traditional Rammed Earth process. This methodology is applied for the first time, on a Rammed Earth wall of a farm located in Bresse (France). Thanks to this methodology, pedological horizon, extraction depth and location of the material source are identified. The surface area excavated for the construction of the building is estimated. Micromorphological study gives information on mixing degree and water content at implementation time. Strain features associated with ramming effect and Rammed Earth boundary layer are also highlighted. Running Head: Rammed Earth micromorphological analysis
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effect of moisture content on the mechanical characteristics of Rammed Earth
Construction and Building Materials, 2014Co-Authors: Q. B. Bui, Jean Claude Morel, Stephane Hans, Peter WalkerAbstract:Abstract 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.
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first exploratory study on dynamic characteristics of Rammed Earth buildings
Engineering Structures, 2011Co-Authors: Q. B. Bui, Stephane Hans, Jean Claude MorelAbstract:Abstract Rammed Earth construction is attracting a renewed interest throughout the world thanks to its “green” characteristics in the context of sustainable development. Several studies have been carried out to investigate this material and evaluate its durability along with its mechanical, thermal and Earthquake capacities. This paper presents a study on the parameters needed for the seismic design of Rammed Earth buildings in accordance with current Earthquake standards. First, the dynamic parameters of buildings such as natural frequencies and damping ratios–which were necessary to determine the equivalent static seismic force–were identified using in-situ dynamic measurements. Then, these experimental values were compared with the values calculated by empirical formulas suggested in Eurocode 8 to demonstrate that these formulas were applicable for the cases of Rammed Earth structures. Then, modeling was done to find a simple suitable model for Rammed Earth structures. Laboratory experiments were developed to measure the Poisson’s ratio which was necessary for the models. The results provided by the shear-beam model were close to that of in-situ experiments, which showed a shearing behavior of Rammed Earth structures. Elements which influenced the dynamic behavior of this structural type were also discussed. Understanding the dynamic characteristics of Rammed Earth structures will help engineers in their design of new Rammed Earth buildings but also in Earthquake analyses of existing Rammed Earth buildings.
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compression behaviour of non industrial materials in civil engineering by three scale experiments the case of Rammed Earth
Materials and Structures, 2009Co-Authors: Jean Claude Morel, Stephane Hans, Nicolas MeunierAbstract:In order to give an example of a scientific approach adapted to non-industrial materials, we chose to study a structural element: a load-bearing building wall made of Rammed Earth material. Rammed Earth construction is an ancient technique which is attracting renewed interest throughout the world today. Although Rammed Earth is currently regarded as a promising material in the construction sector in the context of sustainable development, it is still difficult to quantify its durability, as well as its thermal and mechanical performances, which discourages people from using it. This paper is devoted to the study of the last problem. Three different scales were studied. The first is the scale of in-situ walls. Dynamic measurements were carried out on site to determine the Eigen frequencies of the walls. The elastic modulus was determined from the frequencies measured by using a finite element model. The second is the scale of a representative volume element (RVE). Rammed Earth RVE samples with dimensions similar to those of the walls on site were manufactured and tested in the laboratory. Finally, at the last scale, called the micro-mechanical scale, tests were performed on equivalent compressed Earth blocks (CEBs), which can replace the Rammed Earth RVE samples to facilitate laboratory tests.
Matthew R. Hall - One of the best experts on this subject based on the ideXlab platform.
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humidity buffering using stabilised Rammed Earth materials
Proceedings of the Institution of Civil Engineers - Construction Materials, 2012Co-Authors: David Allinson, Matthew R. HallAbstract:The humidity buffering potential of stabilised Rammed Earth materials is investigated based on the moisture buffer value concept. The moisture buffer value is (a) measured experimentally, (b) calculated from an analytical solution of the mass transfer and (c) simulated using a numerical solution of the combined heat and mass transfer. The numerical solution to the equations is described, as well as the modelling tool termed ‘CHAMP’ (coupled heat and mass transport in porous media). The results show that stabilised Rammed Earth can be a ‘good’ moisture buffering material under the Nordtest classification scheme. They also show that the moisture buffer value of stabilised Rammed Earth materials could be optimised or maximised by controlling the grading and mineralogy of the sub-soil and the manufacturing techniques. Sensitivity analysis of the moisture buffer value to the moisture transfer resistance at the surface is explored through numerical simulation and the need to control the experimental measurement...
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moisture ingress in Rammed Earth part 3 sorptivity surface receptiveness and surface inflow velocity
Construction and Building Materials, 2006Co-Authors: Matthew R. Hall, Youcef DjerbibAbstract:Abstract Calculations and data for the sorptivity (S), surface receptiveness (o) and surface inflow velocity (uo) in different Rammed Earth mix recipes have been presented and compared with those of conventional masonry materials. The sorptivity of Rammed Earth is generally very low and compares favourably with conventional masonry materials. Capillary moisture ingress in Rammed Earth appears to obey the extended Darcy equation. The surface inflow velocity (uo) appears to decrease linearly against t0.01. The gradient of uo/t0.01 provides the surface receptiveness (o) which quantifies the surface finish of the material and is positively related to the effective hydraulic pore radius (r) of the soil. A Rammed Earth mix recipe appears to be optimised for low sorptivity and high dissipation where the 3.35 ratio, defined in this series of papers, is five or less.
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moisture ingress in Rammed Earth part 2 the effect of soil particle size distribution on the absorption of static pressure driven water
Construction and Building Materials, 2006Co-Authors: Matthew R. Hall, Youcef DjerbibAbstract:Abstract A novel adaptation of the initial surface absorption (ISA) test has been presented that is suitable for use with both unstabilised Rammed Earth (URE) and cement-stabilised Rammed Earth (SRE). It provides axial symmetry of the imbibed water and has identical test specimen geometry to the proposed initial rate of suction (IRS) ‘wick’ test, which has previously been discussed in this series of papers. The ISA rate for Rammed Earth is typically lower than that of conventional masonry such as fired clay bricks and in situ cast concrete. Both particle-size distribution and the ratio between total specific surface area to relative clay content (SSA t /CC), appear to be a significant factor in determining the non-saturated permeability of the Rammed Earth. The addition of ordinary Portland cement to selected Rammed Earth mix recipes can either significantly increase or decrease the non-saturated permeability of the material depending upon the amount of cement added. There appears to be an optimum level of cement dosage for impeding moisture ingress in SRE, and this level varies with contrasting mix recipes.
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Rammed Earth sample production context recommendations and consistency
Construction and Building Materials, 2004Co-Authors: Matthew R. Hall, Youcef DjerbibAbstract:Abstract A novel approach to specifying and creating Rammed Earth soil recipes, through a process of blending graded quarry material, has been presented. The soil recipes are highly consistent and reproducible, allowing the accurate control of parameters such as particle-size distribution. A novel technique for the consistent production of Rammed Earth cube samples has been presented that satisfies NZS 4298: 1998, and is in good agreement with the established Proctor standard for compaction. Under the proposed method for Rammed Earth sample production, the level of energy input used for compaction can be varied depending upon soil type. For a given compactive effort, the variation in dry density due to soil type did not appear to be directly related to the characteristic unconfined compressive strength of the Rammed Earth samples. Experimental data have been included.
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Moisture ingress in Rammed Earth: Part 1—the effect of soil particle-size distribution on the rate of capillary suction
Construction and Building Materials, 2004Co-Authors: Matthew R. Hall, Youcef DjerbibAbstract:Abstract The novel initial rate of suction (IRS) ‘wick’ test has been presented, and is suitable for determining the rate of capillary moisture ingress in unstabilised Rammed Earth that slakes on contact with water. Experimental testing was performed using the ‘wick’ test to investigate the effect of soil particle-size distribution on moisture ingress in Rammed Earth. Rammed Earth generally absorbs much less water due to capillary suction, and at a slower rate, than conventional masonry building materials such as bricks and concrete. Moisture ingress in Rammed Earth, due to capillary suction, increases linearly per unit inflow surface area against the square root of elapsed time t . The particle-size distribution of the soil is critical in determining the rate at which moisture may ingress. In a suitable soil, the ratio between the total specific surface area (SSA) of the aggregate fraction and the mass of the binder fraction appears to be positively linked with the rate of capillary suction in Rammed Earth. Experimental data have been included.
