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This paper investigates the viability of using a commercially available liquid polymer (LP) in lieu of ordinary cement to stabilize soil during rammed earth (RE) construction. The scope of this study includes modifying and testing the locally available natural soil with two different LPs at various percentages. Once the optimum moisture content (OMC) of the soil with LPs was determined using the Proctor test, test samples were prepared by chemical and mechanical stabilizations. Following the curing process in an unconfined open-air laboratory environment for 7 days, soil samples were tested to determine the unconfined compressive strength (UCS) and California bearing ratio (CBR) values. The results demonstrate that the lubrication effect of polymers is different than that of water. The first polymer type yields a lower OMC compared to water, while the second polymer achieves a higher OMC. The CBR and UCS values of polymer-stabilized soils are improved for both polymer types at all dosages. The CBR values of polymer-modified soils showed as high as a 10-times improvement compared to Portland cement (PC) stabilization. A similar trend is observed for the UCS results as well. The UCS value of polymer-stabilized soils reached over 1900 psi (13 MPa), which was over 3-times higher than the UCS of PC-stabilized soil. [ABSTRACT FROM AUTHOR]

Earthen construction is one of the world's oldest and most popular construction methods, and it is still the target of prejudice due to the loss of ancestral knowledge. Due to the need for more effective and healthy building solutions, this study conducted a survey to determine the interest and knowledge of construction professionals regarding sustainable and natural materials and building techniques to understand how open these professionals are to changes in their working methods and if they identify urgency in that change. With the intent of proving the durability of earthen construction materials, laboratory research was developed which involved the preparation and performance evaluation of samples of earthen elements from the most-used techniques: rammed earth and compressed earth blocks. This evaluation was performed using the accelerated erosion test, simulating periods of rainfall and drying, and the post-test loss of resistance was also evaluated. According to the results obtained from the research survey, there is a predominant lack of knowledge about earthen construction and other traditional and sustainable materials. On the other hand, the experiments demonstrated that earthen construction can be durable when using either a small percentage of stabilizing material or a covering plaster. [ABSTRACT FROM AUTHOR]

The influence of hydric state on the elasto-viscoplastic behaviour of a unstabilised rammed earth (URE) wall has yet to be studied in the literature. This paper presents an experimental campaign on a rammed earth wall. The aim is to evaluate the link between the mechanical properties (including viscosity) and the varying hydric state inside the drying wall after manufacture. Cyclic axial compression and stress relaxation tests were carried out for this purpose. A compression test was conducted up to 0.1 MPa, followed by a stress relaxation test. These tests were periodically performed over 32 weeks. In addition, the hydric state inside the wall was monitored by humidity sensors. The results show that both the elastic modulus and the dynamic viscosity coefficient increase as the structure dries. A dependence of the mechanical behaviour on time is therefore found in these samples in the transient state. This can occur when the sample is in the drying or wetting phase. As rammed earth is a material particularly sensitive to water, this result is crucial for the durability of earthen constructions. [ABSTRACT FROM AUTHOR]

This research is focused on tulou, collective dwellings of Fujian (China), built with rammed earth and wood. Except for the evident variation in size and in shape between different tulou, all of them apparently share a similar design and layout features and also the scientific literature on this topic does not highlight substantial differences among them. Despite the generic uniformity, it is however possible to clearly distinguish two groups of tulou, built by different populations and reflecting different life styles and dwelling ideas: the Minnan and Hakka tulou. Starting from this new assumption and through a systematic analysis of eight significant case studies, in this paper it is proved for the first time that the functional differences, already partly recognized by previous studies, can be clearly linked to the typological and construction ones as well as. Thanks to this new methodological approach, in the future it will be possible to set up the analysis of this vast heritage in a more orderly manner, allow a greater integration of various disciplinary research and plan a "Manual on tulou restoration", intended as a guide for restoration and dissemination of the knowledge regarding the original materials and techniques of tulou. [ABSTRACT FROM AUTHOR]

يدرس هذا البحث، كما هو ظاهر من العنوان التمثيل القنصلي للتجار والدول المسيحية في المدن والموانئ في دول الغرب الإسلامي. ويركز بصفة خاصة على الدولة الحفصية لأنها تمثل بامتياز النموذج الذي تتوفر فيه الوثائق التي تسمح لنا بدراسة هذا الموضوع. تعتمد الدراسة في أساسها على الوثائق وهي في مجملها المعاهدات المبرمة بين أطراف العلاقات، مسلمين من جهة ومسيحيين من جهة أخرى، والمراسلات المتبادلة بينهم على اختلاف وتنوع مواضيعها واغراضها. وهي وثائق تزخر بالمعلومات التي تخص الموضوع بالدرجة الأولى

The article is focused on design of mixture of rammed earth, producing, testing and determination of fracture energy of unfired rammed earth and its stress-strain curve in tensile bending test. Three different mixtures of rammed earth were designed and tested. The amount of water and binder is one of the key properties of the rammed earth, the amount of the water is expressed by the water-clay ratio. Mechanical properties of the earth material highly depend on the composition of sand, clay and water. The prescription AGL III with 80 % of sand, 20 % of clay and 0.400 water-clay ratio reached the maximum value of fracture energy 4.858±0.002 J/m2 and set AGL V had the minimum value 1.934±0.310 J/m2. [ABSTRACT FROM AUTHOR]

• Properties of rammed interface layers of earthen structures were analyzed. • Tensile and shear strengths of these layers were lower than compressive strength. • The rammed pit interface showed superior properties compared to other types. Layer interfaces are the weakest parts of traditional rammed earthen structures. Different ramming technologies for the interfaces between layers were found to have a significant effect on the level of destruction. Accordingly, four interface treatment methods were simulated to reveal the mechanism and damage mode for the interfaces between different layers: no interface, fine interface, coarse interface and rammed pit interface. Moreover, elastic wave velocity, tensile strength, compressive strength and shear strength tests were performed to explore the effects of different interface treatment technologies on different layers. The results showed that the tensile and shear strengths of the rammed earthen layer interfaces were much lower than the compressive strength. The tensile strength was only 1/30 of the compressive strength, which was the decisive factor in the ultimate destruction of such sites. An effective measure to improve the shear strength of rammed earthen sites is to increase the depth and uniform area of friction of the layer interface, and the roughness of the contact surface between layers. The interface treatment with the rammed pit layer provided superior results to the coarse and fine layers. The abovementioned results provide a theoretical basis for the scientific cognition of traditional ramming and consolidation technologies of earthen sites. [ABSTRACT FROM AUTHOR]

Abstract Design, construction and operation of built environments emit 40% of global anthropogenic greenhouse gases. Search for alternative building materials is imperative for ensuring sustainable habitat for world's increasing population. Rammed earth is one such material with dramatically lower embodied energy and emission than concrete or brick. This paper explores further reduction of operational emission of rammed earth by improving its thermal resistance by recycling industrial by-products such as crumb rubber. The dividend from the introduction of the filler material is examined. The results have been validated with experimental data. Effect of volume fraction, size, shape and spatial distribution of the filler has been presented. It is noted that the recycled fillers considerably improve the thermal insulation. However, they induce increased thermal stress on rammed earth. Thus, a trade-off between strength and thermal resistance needs to be reached. The results would be useful for arriving at an optimal spatial design of the filler to achieve the target thermal resistance and strength. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Non-destructive ultrasonic wave velocity was used to assess the RE materials. • Thermal and mechanical properties of sustainable stabilizers were experimented. • Sustainable additives were considered as replacement for industrial stabilizers. • A simple method for evaluating the sensitivity to humidity was introduced. • SEM was considered to check reaction and bond between aggregates and binders. Abstract The overall behavior of rammed earth (RE) as a low embodied energy construction method can be enhanced by using stabilizers. Several studies have been performed on cement and lime stabilized RE. However, studies on other additives, especially the sustainable ones, are limited. In this research, the effect of stabilizers including cement, pozzolan, microsilica, fiberglass, guar gum and phase change material (PCM) was evaluated on the performance of RE mixtures. The mixtures were assessed by considering the durability, shrinkage, thermal conductivity, mechanical properties and their sensitivity to the humidity. Then, the correlations were determined between the mechanical properties and the non-destructive wave velocity. Scanning electron microscope (SEM) used to analyze the reaction and the bond between the stabilizers and aggregates. The improvement in ductility and energy absorption of RE is significant by limiting the guar gum content. Pozzolan, especially used in conjunction with microsilica, improved the mechanical behavior of the RE mixtures. Fiberglass significantly enhanced the ductility, the tensile strength, and the energy absorption. It was concluded that aggregate volume fracture and admixture type are the most effective parameters on the thermal conductivity. Furthermore, the wave velocity is a proper tool to evaluate the suitability of the RE. More durable, sustainable and eco-friendly mixtures can be achieved by using a sufficient amount of guar gum and pozzolan with microsilica to improve the mechanical behavior of RE materials and also reduce the carbon footprint of RE materials. [ABSTRACT FROM AUTHOR]

This article reports pull-down tests performed on rammed earth construction in Bhutan. The pull-down specimens involved an old rammed earth building component as well as a newly prepared rammed earth wall. Both the wall specimens were tested in out-of-plane direction. Theoretical rigid body formulation and finite element (FE) models were developed to predict the response of the rammed earth structures under out-of-plane loading. The validated FE model was further extended to parametric study of material and physical characteristics of rammed earth construction and their effect on critical response quantities. The change in elastic modulus showed effect in the pre-cracking phase of the wall. Density of rammed earth on the other hand affected the post-peak response of the rammed earth wall. Furthermore, an increase in the physical characteristics, namely, the thickness of wall and the vertical superimposed load on top of the wall, enhanced the rocking resistance capacity of the out-of-plane loaded rammed earth walls. [ABSTRACT FROM AUTHOR]

Highlights • The behaviour of rammed earth was investigated under compression and shear loading. • The repair effectiveness of clay- and lime-based grouts was compared. • The clay- and lime-based grouts present similar repair performance. • The injection repair was unable to recover the interlocking of the coarse particles. • Sonic tests were not sufficiently sensitive to evaluate the repair effectiveness of injection. Abstract Earth constructions constitute an important part of the built heritage and are spread worldwide. Rammed earth is among the most used earth construction techniques, though it exhibits a high seismic vulnerability. Nevertheless, the structural behaviour of rammed earth structures is still insufficiently comprehended. Thus, the preservation of this built heritage requires exhaustive characterisation of its mechanical and structural behaviours, as well as the development and validation of adequate intervention solutions. In this context, this paper presents an experimental program aimed at evaluating the effectiveness of grout injection to repair cracks and at further characterising the in-plane shear behaviour of rammed earth walls. The experimental program included the testing of rammed earth wallets under diagonal compression, which were subsequently repaired with injection of a clay-based or a hydraulic lime-based grout, and retested. Furthermore, sonic tests were conducted on the wallets before the destructive tests. The obtained results allowed to highlight that both grouts led to similar repairing performances, though the interlocking contribution promoted by the coarse particles of the rammed earth to the shear behaviour was found to be irrecoverable. [ABSTRACT FROM AUTHOR]

Highlights • DEM to investigate the in-plane seismic behaviour of rammed-earth walls. • A real earthquake excitation was applied to the model. • Excitation was scaled at different amplitudes to assess the damages. • For excitations lower than 2.3 m/s2, rammed-earth walls had satisfying performance. Abstract Rammed earth (RE) is a construction material which is manufactured by compacting the soil within a formwork, in superimposed layers. RE is attracting scientific studies because of its sustainable properties : a very low embodied energy and an advantageous living comfort due to a particular benefic hygro-thermal behaviour. Numerous studies have been conducted to investigate RE material and RE structures, however, a lack of knowledge on the seismic performance of RE buildings is noticed. This paper presents an advanced numerical study to investigate the in-plane seismic behaviour of RE walls. First, a numerical model of an in-situ RE wall was constructed by using discrete element modelling (DEM). The relevancy of the numerical model was verified by comparing dynamic properties of the model with that measured on the in-situ wall. Then, a real earthquake excitation was applied to the model, in order to evaluate the seismic performance of the RE wall studied. This is the first time, to our knowledge, that a dynamic discrete explicite analysis was performed for a RE wall. The excitation was scaled at different amplitudes to assess the damages following different earthquake intensities. The results showed that for seismic excitations lower than 2.3 m/s2, RE walls studied had satisfying in-plane earthquake performance. [ABSTRACT FROM AUTHOR]

Highlights • Cement-stabilised rammed earth protects embedded carbon steel from corrosion. • Carbonation deteriorates the initially-passive embedded steel environment. • Low capillary absorption and rapid desorption inhibit corrosion. • Corrosion potential higher than −200 mV SCE indicates negligible corrosion. Abstract Cement-stabilised rammed earth (CSRE) reinforced with steel is a modern adaptation of an ancient construction technique, permitting the use of a wider range of structural forms and applications than those used traditionally. However, corrosion behaviour of steel embedded in CSRE is not yet understood, casting doubt on the longevity of these structural solutions. In this paper, we assessed the ability of a range of CSRE mixes stabilised with 10% cement to protect embedded steel against carbonation-induced corrosion by using electrochemical measurements and considering also material alkalinity, carbonation resistance and capillary absorption. Results demonstrated that the pH of the CSRE mixes was sufficiently alkaline to provide the appropriate environment for passivation of steel reinforcement. Based on the experimental results, carbonation would most likely have reached the reinforcement within approximately 5–15 years (50 mm cover) or 30–75 years (150 mm cover), depassivating the reinforcement within the design life span. The findings demonstrated that a corrosion potential of −200 mV SCE indicates conditions of negligible corrosion of steel in CSRE. As behaviour varied little between the four tested soil mixes (of varying granularity), it is reasonable to expect that findings presented here also apply to other soil mixes stabilised with 10% cement. [ABSTRACT FROM AUTHOR]

Rammed earth (RE) is a construction material which is manufactured by compacting the soil in a formwork, in different layers. Several recent studies have investigated this material. The seismic performance of RE buildings is an important topic which needs to be carefully investigated. The complex numerical model seems a performant approach to investigate the seismic performance of a whole building. To correctly establish the model, the shear parameters of the material, which are the cohesion and the friction angle, should be identified. This paper first presents experimental studies on the shear parameters of RE through the direct shear tests, at two different scales. The differences of the results at different scales are analyzed. Then, the obtained experimental values are used in a numerical model to simulate the shear behavior of RE walls which are loaded by a constant vertical stress and pushed horizontally on the top. From the obtained results, the values for numerical models are recommended. [ABSTRACT FROM AUTHOR]

With the introduction of the modern rammed earth technique, a large number of modern rammed earth buildings were constructed in China Mainland. China has a vast territory, which faces the Circum-Pacific seismic belt on the east and the Eurasian seismic belt on the south; earthquake has constantly threatened the safety of people’s lives and property. Consequently, it is necessary to probe in the seismic performance of rammed earth buildings. Two un-stabilized rammed earth specimens, one un-stabilized rammed earth reinforced with geogrid sheets’ specimens, and four stabilized rammed earth specimens were built for obtaining a better insight on the behavior of un-stabilized rammed earth/stabilized rammed earth walls under cyclic in-plane loads. Testing results are discussed in terms of failure mode, shear capacity, hysteretic curve, stiffness degradation, and total energy dissipation to provide comparisons of the seismic performance between un-stabilized rammed earth and stabilized rammed earth specimens. Different failure modes indicated that the cohesion between particles and the bond strength between layers are the two key parameters for the shear capacity of rammed earth buildings. It is also demonstrated that stabilized rammed earth specimens have higher shear and energy dissipation capacity but weaker deformation capacity than un-stabilized rammed earth. [ABSTRACT FROM AUTHOR]

Construction and demolition debris, mainly concrete and masonry rubble, represent a significant share of municipal waste. Recycling crushed concrete aggregates and using them as substitutes for natural ones might therefore be determinant in reducing landfilling and mineral resource depletion. An innovative way to give new value to Recycled Concrete Aggregates (RCAs) is to ram them in layers to form load-bearing walls for stabilised Rammed Earth (RE) applications. However, the success of those few existing RE projects using RCA is mainly due to the knowledge and experience of the contractors rather than official standards or guidelines or scientific literature. The objective of this study was to further the knowledge of this building technique by determining the effect of different RCA replacements on the material’s mechanical resistance, sustainability and hygroscopic properties: indicative of the structure’s structural, environmental and hygrothermal performance. Mechanical resistance was assessed by means of the Unconfined Compressive Strength (UCS, commonly used for rammed earth-like materials), hygroscopic properties via Moisture Buffer Value (MBV) and sorption isotherms while the sustainability was assessed via consequential Life Cycle Assessment (LCA). Microstructural investigations via mercury intrusion porosimetry, nitrogen adsorption-desorption isotherms, scanning electron microscopy and X-ray diffraction were performed to understand and explain material mechanical and hygroscopic behaviour. The building technique, already proven to be durable, was demonstrated to be resistant (from 4 to 12 MPa at 28 days depending on the RCA replacement and cement content), sustainable (down to 25 kg CO 2 -eq. of embodied carbon per square meter of load-bearing wall) and to have good moisture buffering abilities (0.88 g/(m2%RH) for mixtures containing only RCA). Strength appeared to be more related to the particle size distribution of the mix rather than to the percentage of RCA added. The amount and type of stabiliser added to the mix and the distance covered by the RCA during its lifetime strongly affected the environmental sustainability of the mixture; to maximise the potential of this building technique, reducing the amount of cement in the mixture by using alternative stabilisers should be the main priority. [ABSTRACT FROM AUTHOR]

Rammed earth is widely utilized in both developed and developing countries due to its low embodied energy and good natural moisture buffering of indoor environments. However, its application in seismic active regions was limited owing to its intrinsically low resistance to dynamic actions. This paper presents the test results of four cement-stabilized rammed earth walls with confining tie-column elements under cyclic loading, aiming at assessing the cyclic behavior of proposed rammed earth walls with confining tie-column elements. The test results revealed that the proposed confining tie-column elements could significantly improve the cyclic behavior of cement-stabilized rammed earth wall, exhibiting good strength and ductility. [ABSTRACT FROM AUTHOR]

Rammed earth is a traditional construction technology that has proven to be sustainable. This paper explores further improvement of its multifunctional performance by increasing the strength, reducing moisture permeation and increasing the thermal resistance. Surface application of microbial cementation was found to increase the strength by 25%. The water permeability and erosion of the blocks also reduced by 24% and 62% respectively, due to surface application of microbial cementation. The thermal test showed that addition of crumb rubber resulted in a temperature difference of around 30 °C even after 6 h. However, the addition of crumb rubber also reduced the strength. This research demonstrates that significant improvement of overall performance of rammed earth materials can be achieved through various treatments. However, the overall performance requirements are specific to the engineering application and synergistic and antagonistic interactions must be considered to obtain an optimal performance. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Rammed earth has been considered as a sustainable construction technique that uses local soil to build structural walls. However, some natural soil do not have adequate strength and must be treated in order to improve their engineering properties. Chemical stabilization is a recent technique for this purpose and Portland cement is the most commonly used binder material. In the current study, industrial by products such as calcium carbide residue (CCR) and fly ash (FA) are investigated as binders instead of hauling them to landfills. Two different ratios of binders (CCR:FA = 40:60 & CCR:FA = 60:40) at five different binder contents (3%, 6%, 9%, 12% & 15%) were utilized to investigate strength properties of a model soil. Based on the CCR and FA ratios, soil specimens were grouped as A and B. The unconfined compressive strength (UCS) for both groups was tested after four different curing times (3, 7, 28 & 60 days). The UCS values of Group A specimens showed better performance at 12% binder content, whereas, Group B specimens showed an improved strength behavior at 15% binder content for all curing conditions. Also, results of SEM images for Group A specimens at 12% binder content indicated formation of a more integrated soil matrix with reduced soil voids and therefore, significant improvement of the soil strength. [ABSTRACT FROM AUTHOR]

Rammed earth (RE) constructions are widespread in underdeveloped rural areas in developing countries. However, these RE constructions are often susceptible to earthquake damage due to their poor seismic performance. Precast concrete tie columns and ring beam (tie bars) were proposed to improve the seismic behavior of RE constructions. Four RE walls, including a traditional RE wall and three RE walls with precast concrete tie columns and ring beam (tie bars), were tested under reversed cyclic loading, and the seismic behavior of these tested specimens was evaluated in terms of failure pattern, energy dissipation, displacement ductility, and stiffness degradation. The results showed that a significant increase of the load-bearing and deformation capacity could be achieved with the application of precast concrete tie columns in combination with RE. The load-bearing capacity and deformation capacity of traditional RE wall were increased by an average of 113% and 417%, respectively. These test results could provide reference to the design and construction of the environmental-friendly structures in rural areas. [ABSTRACT FROM AUTHOR]

Despite the use of rammed earth became marginal in the second half of the past century, Portugal still holds an important built heritage. Recently, a growing use of rammed earth has been observed in modern constructions, but it is putting aside the roots of traditional rammed earth construction. The seismic behaviour of rammed earth buildings is still insufficiently comprehended, constituting a matter of great concern, since most of the traditional dwellings are built on regions with important seismic hazard. Moreover, the complex architecture of modern rammed earth buildings is expected to make their seismic behaviour even more fragile. This paper intends to provide a better comprehension on the seismic behaviour of rammed earth constructions from Portugal. For this purpose, twenty traditional dwellings were evaluated on the basis of a simplified approach, while a modern construction was investigated by means of destructive and non-destructive testing approaches. The main findings of these approaches are discussed in detail, but it can be highlighted that the architectural features of traditional rammed earth buildings benefit their seismic behaviour, while the complex architecture of modern rammed earth buildings demands using advanced engineering tools for their seismic assessment. [ABSTRACT FROM AUTHOR]

The present paper is concerned with the simulation of the Casagrande test carried out on a rammed earth material for wall-type structures in the framework of Limit Analysis (LA). In a preliminary study, the material is considered as a homogeneous Coulomb material, and existing LA static and kinematic codes are used for the simulation of the test. In each loading case, static and kinematic bounds coincide; the corresponding exact solution is a two-rigid-block mechanism together with a quasi-constant stress vector and a velocity jump also constant along the interface, for the three loading cases. In a second study, to take into account the influence of compressive loadings related to the porosity of the material, an elliptic criterion (denoted Cohesive Cam–Clay, CCC) is defined based on recent homogenization results about the hollow sphere model for porous Coulomb materials. Finally, original finite element formulations of the static and mixed kinematic methods for the CCC material are developed and applied to the Casagrande test. The results are the same than above, except that this time the velocity jump depends on the compressive loading, which is more realistic but not satisfying fully the experimental observations. Therefore, the possible extensions of this work towards non-standard direct methods are analyzed in the conclusion section. [ABSTRACT FROM AUTHOR]

A hierarchical constitutive model based on the framework of elasto-plasticity is developed to model the mechanical behavior of rammed earth which is a quasi-brittle material. This model holds two mechanisms of plastic deformation, one related to shear failure and another one to a tensile mode of failure. Different hierarchies for the model, which are merely levels of complexity, are proposed according to the amount of information available to identify the model parameters. The model was validated simulating a diagonal compression test and a pushover test on a wallette. The simple elasto-plastic model (level-1) was able to capture some basic features of the rammed earth behaviour essentially for a rather small range of deformations, it can be used for a first estimate of the loading capacity of a system. The more sophisticated model (level-2) was able to quantitatively retrieve the non-linear behavior of rammed earth over a larger range of deformations. [ABSTRACT FROM AUTHOR]

The use of earth as a building material offers many advantages in terms of sustainability: it is a natural material, most probably non-toxic and ecological, with low energy intensity, low carbon emissions and recyclable. Earth-based mortars are re-gaining its place as building materials for plastering, rendering and repair of earthen walls, not only in the sustainable context but also in terms of efficiency. However, the scientific knowledge about these mortars is still scarce. In particular, the opinions regarding the effects of adding fibers or mineral binders as stabilizers, to improve the performance of the mortar, are contradictory. The study presented in this article is intended to advance the knowledge about the effects of adding low amounts of hemp fibers, hydrated air lime, hydraulic lime, natural cement and Portland cement on the mechanical (flexural and compressive strength, dynamic modulus of elasticity), physical (shrinkage, thermal conductivity, porosity) and hydric (water absorption under low pressure, capillary water absorption, drying) characteristics of mortars formulated with different earth materials. Results show that the addition of the fibers decreases the thermal conductivity of the mortars, which is remarkably good for the mortars made from clayey soil, and slowers the drying of the mortars. They also show that adding the mineral binders will negatively affect the hydric behaviour of the mortars: the water absorption coefficient increases and the drying become slower as the percentage of binder increases. In addition, the use of these binders has no significant effect on the flexural and compressive strength of the mortar. [ABSTRACT FROM AUTHOR]

This article presents a laboratory and field investigation of pull-out resistance of wood bolts in rammed earth heritages. The laboratory testing involved axial tensile tests of four grout specimens prepared in specially designed moulds using PS-F (Potassium Silicate solution-Fly ash) slurry to investigate the performance of anchors. The field testing involved pull-out tests of three wood anchors installed in rammed earth heritages by gravity grouting. Experiments reveal that the failure mode is the pull-out of bolt from grout and average skin friction resistance of bolt–grout interface is approximately 0.34MPa. Load–displacement curves and elastic–residual displacement derived from cyclic loading indicate such anchor system has strong ductility with small elastic deformation and large residual deformation. Bond collapse firstly occurs at the loaded end and then propagates towards the full bonded length. Bond stress distribution is not uniform along the bonded length. Maximum bond stress distributes at the range from 0.3 m to 0.4 m. Emergence of compressive strain in the interface reveals such anchor system enjoys the advantages of both tensile and compressive anchor types, which significantly differs from results from other regular bolts. The research conclusion makes scientific senses to traditional material and craft in rammed earth heritages. [ABSTRACT FROM PUBLISHER]

Rammed earth constructions exhibit strength and deformation properties that evolve as a function of the relative humidity of the air in contact with the walls. This effect must be considered in the structural design of the construction. This work studies, through finite element simulation, the impact of the hygroscopic transfers through the wall on the structural response of a classical two-storey rammed earth building. The coupling between the mechanical and the hygroscopic behaviour is considered by the concept of effective stress for unsaturated soils, in order to reproduce the effect of suction on the strength, the stiffness and the volumetric variations of the rammed earth. The simulations show classical deformation of the structure due to distributed load on the floors while the hygroscopic changes in the rammed earth (essentially drying) induce additional displacements of the walls that remain in a very acceptable range. Finally, an extreme case is envisaged in which the loads on the floors are increased excessively in order to study the plastic response of the wall. [ABSTRACT FROM AUTHOR]

Rammed earth refers to a conventional construction method as well as a material comprising gravel, sand and fine soil. There has been an increasing interest due to it being a sustainable and environmentally friendly material. The strength of rammed earth depends on the material and environment (e.g. temperature and relative humidity). While rammed earth is an established and accepted construction material in some countries (e.g. Australia and New Zealand), its use in South China is mostly related to historical structures of which the UNESCO Tulou buildings in Fujian Province is an example. In addition, South China has a sub-tropical climate with a distinctive rainy, humid and hot season followed by a dry and cool season, and soils are granular due to the underlying igneous geology. With a coarse fraction (sand and gravel) in excess of 80%, their appropriateness as earthen materials is, at first sight, debatable. This paper aims to assess the pertinence of three representative soils from Hong Kong (residual soil, alluvium and completely decomposed granite) for unstabilised rammed earth. Unconfined compressive strength tests and shrinkage measurements at different relative humidity, as well as the organics content are determined. To aid the interpretation of the strength and shrinkage data, a fundamental characterization is conducted, namely of the wettability and particle attributes (size and shape). By comparing the results to established guidelines for earthen construction, the three soils are shown to achieve strengths in the range 0.2–1.4 MPa and shrinkage after equilibration for one week up to 4%, with the residual soil outperforming the others. Moreover, it was found the strength of the soils was influenced by the relative humidity and was strongly dependent on changes of dry density. The wettability results confirmed the higher organics for the alluvium while the more rounded particle shape and greater content of potassium feldspar of the completely decomposed granite corroborated with its lower strength. The results highlight the importance of conducting a fundamental characterization of natural soils for rammed earth via the particle attributes, wettability and mineralogy. [ABSTRACT FROM AUTHOR]

Specific architectural elements can be identified in constructions located in regions frequently exposed to earthquakes. These earthquake resistant features were developed empirically by local communities to protect their built-up environment. Research in these traditional earthquake resistant practices, resulting from a local seismic culture, is a relevant and positive approach, since it focuses on the strengths of a system rather than on its weaknesses. Its integration into current vernacular building practices can help to preserve and retrofit surviving in-use examples without prejudice to their identity. This paper presents an overview of the most common techniques traditionally used around the world, based on literature review. Additionally, it identifies the use of these techniques in the Portuguese vernacular heritage in order to contribute for the awareness and strength of the local seismic culture in Portugal. [ABSTRACT FROM AUTHOR]

In diverse parts of the world there exist some building systems that are generated for structural and constructive response to the earth constructions. In particular, this article discusses about the perpendicular unions of the walls of rammed earth. This is why, after a brief description of the reinforcement system, its advantages and consequences are developed, compared to other reinforcement systems. In this way, quantitative conclusions are obtained, demonstrating the increasing global resistance of the wall corners compared to horizontal efforts (wind and earthquake) according to the constructive reinforcement system which does not have it. It has also been analysed the collapse of these walls facing gravitational and horizontal loads. The ultimate goal of this work is to preserve the cultural heritage, traditional construction systems and to apply them, by implementing actual improvements, to their recovery. [ABSTRACT FROM AUTHOR]

This study analyses the mechanical behaviour under pseudo-dynamic loading of structural elements built in rammed earth and strengthened with polyester fabric strips. This strengthening technique was developed to exploit the strength potential of rammed earth and to solve its lack of tensile strength. For this reason, in-plane cyclic tests were carried out to investigate the shear behaviour of unstrengthened and strengthened walls. The strengthening technique requires low-tech equipment and workmanship, uses readily available, not expensive and industrially standardised materials. The experimental results were analysed in terms of stiffness degradation, energy dissipation capacity and equivalent viscous damping. Although the unstrengthened and strengthened walls confirmed a limited ductile behaviour, the findings confirm that the strengthening contributes to limit the spread of the diagonal cracks and provide an increase of strength in terms of horizontal load and displacement capacity. [ABSTRACT FROM AUTHOR]

Rammed earth is considered a very sustainable construction system due to its low embodied energy, long service life and high recyclability. However, authors found that there is a lack of experimental results at real scale regarding rammed earth thermal behaviour. For this reason, this paper is first focused on the characterization of two different types of earth in order to check the suitability of being used in rammed earth walls. After the characterization, two experimental cubicle-shape buildings were built in Barcelona and Puigverd de Lleida (Spain) in order to test the thermal behaviour of their walls in two different climatic conditions. Temperature profiles inside walls have been monitored using thermocouples and temperature profile of southern walls was analysed in free floating conditions during summer and winter periods of 2013. Results show that thermal amplitude from outside to inside temperatures are decreased by rammed earth walls, achieving constant temperatures in inner surface of southern walls. [ABSTRACT FROM AUTHOR]

Nowadays, the growth of energy consumption in buildings is an important topic. Rammed earth (RE) structures have attracted the attention of engineers and contractors in recent years due to their advantages such as sustainability, availability and low embodied energy content. These advantages result in less energy consumption in the life cycle of the RE structures. However, there is a lack of research on the mixture composition of RE materials containing admixtures. This research introduced integrated analytic network process (ANP) and genetic algorithm (GA) methodology to select the optimum mixture of RE material containing cement, expanded polystyrene(EPS), and phase change materials(PCM) with different moisture content. The five criteria for evaluations were cost, building weight, carbon footprint, mechanical strength and thermal performance. Thermal and mechanical experiments were performed on the different mixtures of RE. Based on the results of the ANP-GA approach, a RE mixture with mass ratios of 78% soil, 12% moisture, and 10% cement was found to be the most suitable RE mixture. ANP-GA eliminated EPS and PCM due to the low strength of EPS-RE and the high cost of PCM; however, they made RE perform well in thermal characteristic. This proposed the model can be used to select the ideal mixture of other engineering materials. [ABSTRACT FROM AUTHOR]

Rammed earth (RE) construction is attracting renewed interest throughout the world thanks to its sustainable characteristics: very low embodied energy, advantageous living comfort due to substantial thermal inertia, good natural moisture buffering and an attractive appearance. This is why several studies have recently been conducted to investigate RE. However, there have not yet been sufficient studies on the seismic performance of RE buildings. This paper presents an experimental study on the static nonlinear pushover method and its application to the seismic performance of RE structures. Several walls with different height/length ratios were built and tested to obtain nonlinear shear force–displacement curves. By transposing these shear force-displacement curves to an acceleration–displacement system and using the standard spectra presented in Eurocode 8, the performance points were determined, making it possible to assess the seismic performance of the walls studied in different conditions (seismicity zones and soil types). [ABSTRACT FROM AUTHOR]

Rammed earth (RE) has enjoyed a revival in recent decades due to the increasing awareness of environmental issues surrounding the building industry. Although RE in its traditional form is deemed a highly environmentally-friendly material, the same cannot be said for its modern stabilised counterpart. Comprehensive experimental procedures exist to estimate mechanical strength properties of stabilised RE (SRE). However, tests for material durability are far less common. Engineers and practitioners therefore assume that strength and durability are interchangeable properties, i.e. the stronger the material, the more durable. Inflated strengths are recommended to ensure adequate durability, leading to high environmental costs through excessive use of stabilisers. This paper rates the relevance of two acknowledged durability tests (accelerated erosion due to sprayed water and mass loss due to wire brushing) and relates outcomes to the strength and the environmental impact of several SRE mixes. The environmental impact of each mix was estimated using attributional and consequential life cycle assessment (LCA) approaches as well as an assessment of cumulative energy demand. Results demonstrated that it is possible to have durable SRE mixes without paying the cost of using environmentally-expensive stabilisers. [ABSTRACT FROM AUTHOR]

This study assesses the structural vulnerability of part of a later medieval earthen building at Ambel (near Zaragoza, Spain), once a preceptory or monastic house belonging to the Military Orders. An inspection of its morphology and materials coupled with the results of an extensive campaign of static monitoring reveals marked structural inhomogeneities, the product of more than a thousand years of construction, failure, and repair from the 10th century to the present day. Building materials are inappropriately juxtaposed, there are discontinuities between construction phases and fundamental concerns remain over the long-term stability of the structure. The current condition of the structure is mainly influenced by structural discontinuities introduced at the time of construction, the unintended consequences of repair and modification and the material decay that has affected the base of the rammed earth walls. The overall findings of the static monitoring show that there is no related damage, variations in crack widths are related to the building seasonal cycle. While static analysis is an essential prerequisite before a suitable maintenance program can be fully defined, this study argues that no evaluation of the structural behavior of any historic building can afford to ignore its archaeological “biography” of modification and repair. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Synthetic and artificial fiber fabrics are commonly used as masonry structures reinforcement, both for seismic retrofitting of historical buildings and for realization of new constructions in seismic areas. Correspondingly, natural fiber fabrics are appropriate to earth buildings reinforcement, being compatible from the point of view of environmental sustainability. In this paper the results of tensile tests on jute yarns are reported, organized and statistically analyzed in order to interpret the basic laws of size effects involved. The great variability of yarns behavior and the difficulties in controlling the boundary conditions induced to perform numerical tensile tests on statistical samples of jute fabric, generated in compliance with the statistical distribution of yarns mechanical properties. The comparison between laboratory and numerical tests permits to make some considerations on the difficulties involved in the experimental analysis, in order to define a reliable experimental technique to determine the properties necessary to the successive design. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Rammed earth is one of the oldest masonry construction techniques such that there are many ancient structures built of rammed earth still existing. Recently, applications of rammed earth are encountered more often, due to its ecological advantages such as renewability, sustainability, environmental protection, insulation and use of environmentally-friendly materials. Although it has been widely used in masonry construction, knowledge related to behavior of these structures or structural members is limited. Under this circumstance, in this study, behaviors of stabilized and non-stabilized rammed earth walls were investigated comparatively with masonry brick and aerated concrete walls. For this purpose, non-stabilized, 10% cement stabilized, 10% cement stabilized with 1% glass fibers and 5% cement stabilized with 5% blast furnace slag mixtures were produced in dimensions of 20 cm × 150 cm × 150 cm rammed earth walls. Cyclic behaviors of the rammed earth walls were compared with masonry brick and aerated concrete walls with the same dimensions by using hinged loading test set-up. Structural properties such as load carrying capacities, total energy dissipation and stiffness degradation of the masonry walls were determined by utilizing the results of cyclic loading tests. At the end of the study, it was concluded that rammed earth wall stabilized using 10% cement showed the best structural performance. Surprisingly, performance of masonry brick wall fell behind of other masonry walls, even though it is the most commonly used material in masonry constructions. [ABSTRACT FROM AUTHOR]

The standard codes of practice on the rammed-earth construction are limited. It is essential to ascertain the characteristic compressive strength of the cement-stabilized rammed earth (CSRE) for the structural design of CSRE walls. The test procedures for determining the characteristic compressive strength of CSRE are not available in the standard codes of practices. The specimen size and its slenderness can affect the compressive strength of CSRE elements. This paper deals with the relationships between the specimen's aspect ratio and compressive strength for CSRE using two cement contents (7 and 10%) and two densities. Both cylindrical and wallette specimens having an aspect ratio varying between 2 and 5.81 were tested for compressive strength. The results show that there is hardly any reduction in compressive strength as the aspect ratio was increased from 2 to 5.81 (a reduction in compressive strength of 1 and 3-5% for specimens with density of 1,800 and 1,700 kg=m³, respectively). The study clearly demonstrates that the characteristic compressive strength of CSRE can be obtained by testing cylindrical (150 mm diameter and 300 mm height) or prism specimens (150 mm square cross section and 300 mm height) without applying any correction factor. Furthermore, since the moisture content in the specimen has a significant influence on the compressive strength of CSRE, it is recommended to adopt the wet compressive strength for structural design. [ABSTRACT FROM AUTHOR]

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 Rhône-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. [ABSTRACT FROM AUTHOR]

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The presence of cracks debilitates the structural performance of rammed earth. Grout injection is a repair solution put forward recently, where compatibility issues demand using mud grouts. Little is known on this topic, whereby an experimental program on the mechanical effectiveness of grout injection for repairing cracks in rammed earth was performed. Specimens tested under bending and diagonal compression were retested after repair with injection of mud grouts. Mud grouts incorporating the original soil of the rammed earth are shown to perform better and their injection achieves satisfactory shear strength recovery, but is less effective in recovering initial shear stiffness. [ABSTRACT FROM AUTHOR]

Rammed earth (RE) structures are widely used for more sustainable and environment-friendly buildings. Due to lack of design standards, the engineering decisions often rely on rule-of-thumb method which may lead to quite conservative or unsafe designs. In this study, load and resistance parameters were treated as random variables in reliability analysis. The reliability index and failure probability of RE structures were evaluated using First-Order-Reliability-Method (FORM) and then compared with Second-Order-Reliability-Method (SORM) and Monte Carlo Sampling method. The analysis was performed based on the different a) load combinations, b) wall geometry, c) material type (unstabilized or cement stabilized) and d) mechanical properties of the materials. Based on the results, the RE wall under moderate loading conditions require smaller wall thickness than recommended wall thickness by various guidelines such as New Mexico-USA, New Zealand and Zimbabwe Codes. However, larger wall thickness is needed under severe loadings conditions, especially when unstabilized materials are used. The compressive strength of unstabilized materials under severe loading conditions should be more than minimum recommended. The sensitivity analysis was performed by calculating different importance and sensitivity vectors. The results show that the compressive strength and the environmental loads factors are the most important random variables that contribute to reliability of the structures. The recommended wall thickness and compressive strength for different conditions are presented. [ABSTRACT FROM AUTHOR]