Rammed Earth Houses Research Articles

Architectural Features and Soil Properties of Traditional Rammed Earth Houses: Eastern Croatia Case Study

Architectural Features and Soil Properties of Traditional Rammed Earth Houses: Eastern Croatia Case Study

Structural Stability Evaluation of Natural Fiber Retrofitted Low-Cost Rammed Earthen Houses Under Seismic Loading

Earthen houses constructed using the rammed technique have long served for housing across the globe. However, despite their environmental benefits, these houses may pose unacceptable earthquake risks for the communities. To address this, the current study focuses on investigating the seismic response of unreinforced and retrofitted rammed earth model houses using unidirectional shaking table experiments. Retrofitting is performed using two different approaches. The first method is the traditional way using cement, lime and natural fibers like straw and jute mixed with soil. The second method is a new and innovative approach that uses bitumen-treated natural fibers such as jute and bamboo strips as external encasing reinforcement along with special L-shaped corner reinforcement using jute and bamboo sheets. The study shows that rammed earth houses retrofitted using the proposed novel and low-cost methods with jute/bamboo fibers demonstrate promising results in terms of structural strength and ductility compared to the stabilized counterpart. The fundamental period of the retrofitted and unreinforced houses is found in the order of 0.08 and 0.12 indicating an enhancement in lateral stiffness depending on various level retrofitting methods. The study provides valuable insights and points toward potential changes in the seismic design guidelines for low-cost rammed earthen houses.

Fizikalna svojstva tla u zidovima tradicijskih kuća od nabijene zemlje u istočnoj Hrvatskoj

In eastern Croatia rammed earth houses were traditionally built in the past. The choice of suitable soil for building rammed earth houses depends on several soil properties. Moreover, since there are no standards or recommendations for construction of rammed earth houses in Croatia, the construction and renovation of such houses is almost non-existent nowadays. With the aim of forming detailed recommendations for eastern Croatia area in near future, soil samples were collected from existing houses to test the physical properties of the soil. Obtained results showed that Atterberg limits are within the limits of the recommended values and published results in the literature, while particle size distribution differs from most recommendations and published results.

Earthly Matters, Earthy Visions: National Architecture Narratives and the Unexpected Culture of Norwegian Rammed Earth Houses

Abstract: This research paper shares the neglected story of rammed earth houses in Norway, with a focus on the past conditions that enabled its craft and emergence. Architectural representations in the country have been inexorably tied to craft traditions and localisms, framed as a marriage of natural materials and the built form; however, wood and stone occupy center stage of this material-oriented ethos. Very little attention is given to old rammed earth building techniques. Beyond tectonic considerations, the paper's aim is to document the value-tinged discourse around the making of rammed earth houses, or jordhus, built at the end of the nineteenth century, between 1920 and 1930, and during the post–World War II building boom. I examine and document the social circumstances and ideologies that caused Norwegian individuals to turn to—and away from—such a material. Based on Asbjørn Klepp's seminal "Jordhus i Norge," as well as Akershus Museum's little-known surveys, building projects in Østland, Vestland, and Sørland are the focus of this study of the social, cultural and technological histories embedded in rammed earth free-standing walls. Notions of sustainability and craft, of vernacular knowledge and home aesthetics are then utilized to qualify and weigh the significance of jordhus for present-day building narratives of Norway, thus shedding new light on established methods for the writing and telling of the country's architectural narratives: in the concluding section, I briefly comment on rammed earth's resurgence in the face of current climate concerns and describe a contemporary case study (Raab Jordhus, 2019) that shows the material's significance for future Norwegian architectural cultures.

Shear Strength of Reproduced Soil Mixtures Based on Samples from Rammed Earth Walls from Eastern Croatia

Earthen architecture largely supports the concept of sustainable building. In the seismically active area of eastern Croatia, there is a large number of rammed earth houses, many of which are over 100 years old. All these houses were built using empirical knowledge, i.e., without applying national design standards. In order to support the preservation of ethnic villages and traditional rammed earth houses, a field survey was conducted. Parts of the walls of traditional rammed earth houses were collected, and the material was thoroughly analyzed. Samples of rammed earth were reproduced, and tests were carried out with the aim of determining the shear strength to subsequently determine the seismic behavior of Croatian traditional earthen architecture. This paper presents the results of shear strength tests on samples with different particle size distributions, lime content, the straw of different cereals but also hemp fibers. An increase in shear strength was observed with the addition of natural fibers to the samples.

Energy Saving and Thermal Comfort Performance of Passive Retrofitting Measures for Traditional Rammed Earth House in Lingnan, China

The traditional rammed earth houses sharing similar patterns in the Lingnan region, south China, and distributed in rectangular arrays, are gradually losing their vitality and becoming uninhabited under modern living conditions. This research examined a typical pattern called the “Four-point gold” house and analyzed the suitability of different retrofitting technologies by field measurements and building simulation. To optimize energy consumption, indoor thermal comfort, and the corresponding economic performance of the retrofitting measures for the prototypical house, five measures, including wall insulation, reflective roof coating, carpet, sunshade, and natural ventilation, are proposed after considering the status quo of the building envelope. It is found that the best performance in energy-saving, dynamic investment payback period, and annual indoor thermal comfort are 2192.27 kWh/a, 9.17 years, and 1766 h, respectively. Different parameters are included to be clustered by K means clustering technique, and the comprehensively optimized scheme consists of a regime of 30 mm XPS 30 mm, ZS-221 white coating, carpet, 0.5 m sunshade width, and turning off windows (doors). The proposed retrofitting strategy can be promoted to a wide range of traditional rammed earth houses in the Lingnan region in China and holds a conspicuous energy-saving potential for the suburban and rural residential sectors in the region.

Rammed earth, as a sustainable and structurally safe green building: a housing solution in the era of global warming and climate change

Today with rapidly increasing population and their housing demands, the whole world has been victimized by critical consequences of global warming and climate change. From simple to complex construction, materials being used not only consume massive energy and resources during their life cycle but also deteriorate the environment releasing an enormous amount of dust, solid waste, and greenhouse gases. With an intention to provide immediate solution in the form of sustainable alternative materials, rammed earth is chosen in this study where, natural sub-soil is used as primary constituent, i.e. clay (15–25%), sand (50–60%), gravel (15–20%) with/without small percentage of stabilizer like cement (3–5%), and minimum water (8–12%), and finally tamping the mix in required formwork using simple methods/tools, have clearly justified this construction as low consumer of resources and energy compared to other conventional building materials like brick and cement. This paper outlines environmental impacts of building construction and justifies suitability of rammed earth as an ideal sustainable housing both in terms of environmental and structural stability, based on results obtained from lab tests (compressive strength: 1.5–6.5 MPa, water resistivity, optimum water content) of 100 mm stabilized and un-stabilized cube samples (with variation in moisture content, soil and stabilizer types), site investigation for around 6 years, constructing and demonstrating two small-scaled stabilized and un-stabilized rammed earth houses, discussion with local people, builders and masons. Comparatively, cement-stabilized (5% cement) samples had better overall results than un-stabilized and dung-stabilized samples. In addition, cost comparison showed that 360-mm-thick rammed earth wall was 10–15% cheaper than 230-mm-thick brick wall. Similarly, further verifying and comparing the obtained findings with previous-detailed studies is one of the highlighting parts of this paper.

BuildSense

Buildings can achieve energy-efficiency by using solar passive design, energy-efficient structures and materials, or by optimizing their operational energy use. In each of these areas, efficiency can be improved if the physical properties of the building along with its dynamic behavior can be captured using low-cost embedded sensor devices. This opens up a new challenge of installing and maintaining the sensor devices for different types of buildings. In this article, we propose BuildSense, a sensing framework for fine-grained, long-term monitoring of buildings using a mix of physical and virtual sensors. It not only reduces the deployment and management cost of sensors but can also guarantee accurate and fault-tolerant data coverage for long-term use. We evaluate BuildSense using sensor measurements from two rammed-earth houses that were custom-designed for a challenging hot-arid climate so almost no artificial heating or cooling is required. We demonstrate that BuildSense can significantly reduce the cost of permanent physical sensors while still achieving fit-for-purpose accuracy, fault-tolerance, and stability. Overall, we were able to reduce the cost of a building sensor network by 60% to 80% by replacing physical sensors with virtual ones while still maintaining accuracy of ≤1.0°C and fault-tolerance of two or more predictors per virtual sensor.

Mechanical behaviour of rammed earth column: A comparison between unreinforced, steel and bamboo reinforced columns

This paper presents an experimental study on the behavior of cement stabilized rammed earth (CSRE) column reinforced with steel under axial loading and its comparison with unreinforced and bamboo reinforced columns. Effects of structural parameters such as tie / stirrup spacing on the failure pattern, lateral and axial deformation of columns are studied. Test results show that the load-capacity of columns increases with increase in lateral / tie reinforcement ratio. Maximum axial and lateral deformations occur in columns with least tie spacing. Behavior of CSRE columns reinforced with close tie spacing is characterized by gradual spalling of cover at the failure zone. Steel reinforced columns perform better than other column types in terms of load-capacity; hence it may be used as structural member adjacent to walls for low-rise rammed earth houses. Proposed reinforcement technique can be adopted in the field for enhancement of greater strength and performance of columns.

Hydric characterisation of rammed earth samples for different lime concentrations

The rehabilitation of ancient rammed earth houses, as well as the use of earthen materials in modern constructions, are a growing matter of concern, especially in area such as Rhône-Alpes, France, where 40% of old constructions are in rammed earth. A current pathology observed for this type of construction is related to the rising damps, for which the water from the ground is absorbed by the wall. This situation leads to a very saturated state. As it has been proven that the compressive strength is altered by the presence of water in the pores, a better understanding on high relative humidity range is necessary to be able to predict the mechanical behavior of buildings and thus ensure a better risk assessment. The present study describes experimental results of the water uptake experiments and moisture storage at high relative humidities.

Measured and simulated thermal behaviour in rammed earth houses in a hot-arid climate. Part A: Structural behaviour

Heating and cooling of residential buildings consumes around ten percent of the world's energy. One approach for reducing these costs is to exploit the high thermal mass of sustainable building materials, for example rammed earth (RE), for intelligent solar passive design. However, there is a lack of scientific evidence about the thermal performance of RE houses in real-world settings.This research investigated to what extent thermal performance in unconditioned RE structures in rural Australia can be captured by current accreditation software. Two custom-designed houses were built in the hot-arid city of Kalgoorlie-Boulder, Western Australia: one comprising traditional solid cement-stabilised rammed earth walls (RE) and the other walls with an insulating polystyrene core (iRE). Otherwise the houses were identical in orientation and design. The houses were instrumented to monitor indoor temperature and humidity conditions prior to and during occupancy. Results were compared to those simulated using cutting-edge assessment software BERS Pro (v4.3) as an example of that used for energy efficiency accreditation in Australia. This first paper in this series discusses the houses' construction and instrumentation and results obtained during the unoccupied period, i.e. those purely demonstrative of the structure's thermal performance. A second paper in the series presents data gathered during occupancy, to contrast occupant thermal comfort with that predicted numerically.Measured data showed that both houses performed nominally-identically: the houses did not receive any relative benefit from including iRE. Simulated data was also similar per house. However, measured performance did not match that simulated: simulated rooms had poorer thermal stability and lag and, consequently, exaggerated internal temperature variations. Collected data has been made publicly available for future analyses.

Measured and simulated thermal behaviour in rammed earth houses in a hot-arid climate. Part B: Comfort

Heating and cooling of residential buildings consumes around ten percent of the world's energy. One approach for reducing these costs is solar passive design using building materials with high thermal mass such as Rammed Earth (RE). Several studies have examined the performance of small RE structures or individual rooms within RE dwellings and have demonstrated the material's capacity to provide comfortable internal conditions passively. However, there is a lack of scientific evidence about the performance of full RE houses in real-world settings spanning several seasons. This research investigated the thermal performance of RE structures prior to occupancy and over the course of an occupied year. Two custom-designed houses were built in the hot-arid city of Kalgoorlie-Boulder, Western Australia: one with traditional solid RE walls and the other with walls with an insulating polystyrene core (iRE). Otherwise the houses were identical in orientation and design.This study is presented in two Parts. Part A examined the houses' performance without occupants: This Part examines their occupied behaviour in terms of the occupants' thermal comfort. Comfort was examined using qualitative and quantitative data from sensor measurements as well as occupant surveys and simulated results using state-of-the-art assessment software BERS Pro. Comfort scores for measured and simulated data were determined using rules built into BERS Pro's engine Chenath and a modified version of the ANSI/ASHRAE Standard 55-2010 SET* method.Real-world thermal comfort of both houses outperformed their simulated behaviours: occupants reported comfortable conditions throughout Summer (outdoor maxima 45°C) and Winter (minima 1°C) with no artificial cooling and with minimal heating. The Chenath and SET* methods agreed with comfort performance in Summer but scored Winter performance poorly. Similarly, simulations predicted poor performance in Winter. Consequently, predicted energy demands due to heating were likely far higher than those needed in reality. This paper therefore argues from measured evidence of RE and iRE houses for the suitability of RE as a sustainable building material able to curb domestic energy demands. Collected data has been made publicly available for future analyses.

Analysis of the seroprevalence of and factors associated with Chagas disease in an endemic area in Northeastern Brazil.

Chagas disease (CD) is currently considered a neglected disease; hence, identifying the factors associated with its high prevalence is essential. This study aimed to identify the seroprevalence of and the possible factors associated with CD in inhabitants of the City of Limoeiro do Norte, Northeastern Brazil. Between April and November 2013, blood collection was conducted and a semi-structured questionnaire was administered. Blood samples that showed positive or possible serology for anti-Trypanosoma cruzi antibodies based on indirect immunofluorescence, hemagglutination indirect, and an enzyme-linked immunosorbent assay were analyzed. Associations between CD positivity and the study variables were analyzed using prevalence ratios (PR) with 95% confidence intervals (CI). A total of 812 individuals were analyzed, of which T. cruzi seropositivity was determined in 4.2% (34 individuals). Sociodemographic variables showing a significant association with T. cruzi positivity included age >50 years (PR = 27.6; 95% CI = 6.66-114.4), elementary level education (PR = 5.15; 95% CI = 1.83-14.47), and retirement (PR = 7.25; 95% CI = 3.72-14.14). Positivity for T. cruzi was 6.17 times higher in those who had a history of living in rammed earth houses compared with those who did not (95% CI = 2.19-17.37). There was no evidence of vertical transmission in the individuals studied. Among the individuals infected with T. cruzi, the majority reported having a comorbidity (p < 0.01). This study demonstrated the seroprevalence of CD and identified factors associated with a high prevalence of CD.

Strategies for reducing heating and cooling loads of uninsulated rammed earth wall houses

Abstract The research reported in this paper investigated the potential reduction of heating and cooling loads in a hypothetical uninsulated rammed earth wall house. The analysis was performed in three different climate zones in Australia, namely: climate zone 3, 5 and 7, representing hot arid, warm temperate and cool temperate climate, respectively. The investigation involved simulating the energy load for a rammed earth house with different building parameters using the home energy rating software AccuRate developed by the Australian Commonwealth Scientific and Industrial Research Organisation (CSIRO). In Australia, new building designs must comply with the energy efficient provision of the Building Code of Australia in the National Construction Code (NCC), and one method of compliance is through an assessment of the predicted energy loads. The simulation results show that it is possible for an uninsulated rammed earth wall house in Australian climate zones 3 and 5, to fulfil the minimum requirement of the NCC as long as the building is designed carefully by optimising a number of passive solar strategies. In climate zone 7, however, uninsulated rammed earth houses cannot meet the NCC requirement even after applying passive solar design strategies.

Failure of rammed earth walls: From observations to quantifications

Nowadays, rammed earth construction is attracting renewed interest throughout the world thanks to its “green” characteristics in the context of sustainable development. Firstly, using a local material (soil on site or near the site), rammed earth constructions have very low embodied energy. Secondly, rammed earth houses have an attractive appearance and present advantageous living comfort due to substantial thermal inertia and the “natural regulator of moisture” of rammed earth walls. This is why several research studies have been carried out recently to study the mechanical and thermal characteristics of rammed earth. However, to our knowledge, there are not yet sufficient studies on the tensile strength and the shear strength of rammed earth. The tensile strength of rammed earth is neglected in general due to its very low value, but in extreme conditions (e.g., seismic conditions), knowing the tensile strength is necessary for structural design. Moreover, the shear strength is required in many cases to check the local failure of rammed earth quickly, which has been observed in old structures (especially those submitted to concentrated loads). This paper presents experimental results on tensile strengths and the Poisson ratio of rammed earth specimens. Local failure tests were also conducted on 1m×1m×0.3m wallettes manufactured in the laboratory. The shear strength was then identified using a simple method based on compressive strength, tensile strength and Mohr’s circle theory. The approach proposed was validated by tests on the wallettes. Finite Element (FE) modeling was also carried out to confirm the results. Last, the method presented was validated for stabilized rammed earth lintels presented in the literature.

Analysis for the Shake Table Test of Rammed Earth Wall Panels

Traditional Rammed earth houses are still widespread in rural areas of western China. However, the seismic damage of earth houses is usually serious due to its poor seismic resistance and little research has been conducted on dynamic tests of rammed earth structure. A simple and low-cost method to reinforce the rammed earth wall is put forward in the paper. The shake table testing for both the wall panels with and without reinforcements has been carried out. The test results are analyzed from the aspects of damage phenomenon, dynamic behavior, and acceleration and displacement responses of both specimens. The results show the effectiveness of the reinforcement method on improving the seismic capacity of the rammed earth wall.

Shake Table Test on Rammed Earth Wall Panels

Traditional Rammed earth houses, which possess people traditional cultures, are still widespread in rural areas of western China. However, the earth houses damage is usually serious due to its poor seismic resistance. A simple and low-cost method to reinforce the rammed earth wall is put forward in the paper. In order to test the reinforcement effectiveness, shake table testing for both the wall panels with and without structural reinforcements have been carried out. The performances of the wall panels during dynamic testing are presented and discussed briefly. The result of the test demonstrated the effectiveness of the reinforcement method on improving the seismic capacity of the rammed earth wall. The reinforcement can restrain the crack development and increase the structural integrity of the wall panels. The method can be applied to both existing and new building rammed earth houses.

Regeneration of vernacular architecture: new rammed earth houses on the upper reaches of the Yangtze River

In rural areas of western China, most of the vernacular architectures are made of earth. In the process of urbanization, few residents like to build their houses with earth because the old traditional earth house cannot meet their requirement for higher standard of living. As a result, much more energy will be consumed if industrial building materials are used instead of earth. The regeneration of the traditional earth house, therefore, becomes a challenge in new village construction. This paper briefly describes a project about creating a new prototype of earth house for the migrants along the upper reaches of the Yangtze River to shed light on finding an appropriate approach for regenerating the traditional earth houses with the concept of low-energy housing. It includes an investigation of the traditional earth house and the environment condition of the new settlement, the new house design process, and the quantitative evaluation of the living quality of the new house.

Pityriasis versicolor in the central African republic: a randomized study of 144 cases

The prevalence and the principal epidemiological characteristics of pityriasis versicolor have been studied in a randomized population of 870 adult individuals (418 males and 452 females) in the Central African Republic. The general clinical prevalence was 16.6%. Males were affected more often than females (20.6% vs. 12.9%). For both sexes, the maximum prevalence was in the 15 to 25-year-old age groups (23.5%). Lesions commonly occurred over the face (49.3%) and upper trunk (48.6%). Different climatic areas within the country, type of urbanization, religion and general hygiene showed no relevance to the disease. The prevalence was higher among people living in rammed-earth houses than in people living in hard-built houses. The sebaceous activity of the skin, a feature which is racially and genetically determined, probably constitutes a primary factor for developing this mycosis, associated with the tropical climate as an additional environmental factor.