Earthen Buildings Research Articles

Sample key features affecting mechanical, acoustic and thermal properties of a natural-stabilised earthen material

The use of natural materials has become more important as a result of the growing need to conserve energy, exploit renewable materials, and incorporate architecture and construction into sustainable methods of production. Accordingly, the present work investigates the engineering properties of a new earthen building material. This proposal is based on traditional unfired earthen masonry and consists of compressed earth blocks stabilised with natural polymers and wool fibers for use as insulating and structural load-bearing walls in buildings. The conducted experimental study enabled us to determine the mechanical performance, thermal conductivity, noise mitigation, modulus of elasticity, porosity percentage, and diameter through mercury intrusion porosimetry. The influence of soil characteristics on thermophysical and acoustic properties of tested material were investigated. The experimental data show good efficiency and a significant improvement in the engineering properties of these materials compared to traditional compressed earth blocks. In this research, a comprehensive analysis of the interaction of different properties is proposed as an assessment methodology that could be applied to any kind of stabilised soil material. The correlation of the results, being the type of soil the only variable of the analyzed samples, has allowed identifying sample key features and tests so as to obtain the best mechanical, thermal and acoustic performances.

Earthen Architecture in Greece: Traditional Techniques and Revaluation

A big part of traditional architecture both in rural and urban areas in the Greek territory has been built with raw earth. The aim of this paper is to present earthen buildings’ constructions in Greece and show their important contribution to our heritage. The use of earth as a basic constructing material has given different earthen building cultures and techniques. Earthen construction encloses many varied uses and applications, as walls or as plasters. In different periods of time and historical contexts, from the indigenous inhabitants to the neighborhoods of the refugees of Asia Minor Catastrophe, the earth constructions had a primary role. The existence of earthen architecture was investigated in urban and rural sites in Greece. Building information, documentation, and records of buildings’ design, construction techniques, elements, and systems are presented. Today, there is still a rich architectural heritage throughout the country, which has lasted through the years and withstood seismic activities and poor conservation.

Tulou, earthen buildings in Southeast China

Tulou, earthen buildings in Southeast China

Utilisation of Mass and Night Ventilation in Decreasing Cooling Load Demand

The building sector consumes 36% of the world’s energy and produces around 40% of energy-related carbon emissions. While the building industry moves towards a zero net greenhouse-gas emission policy, ventilation is, and will be, a necessity for the preservation of air quality—especially in climates defined by unsavoury conditions. Therefore, a “mixing mode” cooling system was employed to lower the required energy consumption at an earthen building situated in the premises of Istanbul Technical University. A room of the high-mass earthen building was monitored under different ventilation and shading conditions. Night ventilation was conducted using two modes, 3.2 and 2.3 air changes per hour, and the air conditioning unit, operating from 08:00 to 17:00, had a set temperature of 23 ∘C. Night ventilation was somewhat impactful, reducing the average expected cooling energy demand up to 27%. Furthermore, the earthen building proved to be extremely effective on moderating extremes of temperature under non-ventilated conditions. During a rather hot day, with an outdoor maximum temperature of 35 ∘C, the indoor maximum temperature of the high-mass building was only 25 ∘C, namely within thermal comfort levels. The diurnal temperature proved to be key in the effective application of night ventilation.

Thermal conductivity of two kinds of earthen building materials formerly used in Algeria

Traditional building materials based on earth offer the following advantages: easily accessible, inexpensive, and above all, environmentally friendly. This investigation is intended to determine the thermal conductivity of traditional building materials obtained by mixing two kinds of soil (agricultural and soil taken from a type of desert land (Hamada)), separately, with different amounts of straw, according to the expertise of the inhabitants of M'Sila (a province of Algeria). Then, find the best mass proportion (soil/straw), which gives the lowest thermal conductivity of the obtained earthen materials. Four samples were prepared for each soil, in addition to the reference one (without straw). The considered samples were obtained by sun-drying of the handy dough formed by soil, straw, and water. The hot wire method is the technique used to determine the thermal conductivity in longitudinal and transverse directions. All the tested samples display a thermal anisotropy as the thermal conductivity measured in the longitudinal direction is significantly different from that measured in the transverse direction (p < 0.05). The thermal conductivity of the tested samples is strongly affected by the quantity of the straw added (p < 0.05). All the samples tested with and without straw are within the range ([0.1, 2] W/m° C) recommended for construction materials. It was observed that adding a straw mass equivalent to one-twentieth of the mass of both soils (5% by mass) gives to the Adobe formed a minimum thermal conductivity. The thermal conductivity of the studied earthen based materials depends on their compositions.

Colorimetry of Clays as a Tool to Identify Soil Materials for Earthen Buildings Restoration

In the restoration field and the cultural heritage, the treatment of colour is very important, being an important factor for the decisions and interventions in historic buildings. However, some of these have not the same recognition and protection by authorities, being really vulnerable, especially against natural phenomena like the earthquakes. After the 2017 Puebla Earthquake, the remainders of the earthen architecture of Jojutla de Juarez were collected to be analysed. Natural clays of the quarries near the town were compared by colorimetry tests with the traditional adobe samples which were collected in the locality. There also were conducted particle size analysis and the Unified Soil Classification System, USCS, to obtain the composition and properties of the soils and the adobe bricks, as well as the additives used, mainly straw as fibre reinforcements of the adobe masonry. One of the factors observed which contributed to change the colorimetric values of the clays was the use of stabilizers like lime, on the other hand, these stabilizers also helped to change the USCS classification of the soils and their cohesive properties.

Analysis of the earthen architectural heritage in Piedmont (northern Italy): typologies, construction techniques and materials

Piedmont is characterized by the presence of numerous earthen buildings mainly concentrated in the province of Alessandria. Studies conducted over the last decade, however, have shown the presence of interesting examples of these buildings also in the provinces of Asti, Torino, Biella and Cuneo. They are generally two-storied rural constructions, built with both fired bricks (for the bearing structures) and adobe (for internal and external walls).

SIMULATION-BASED ANALYSIS OF EARTHEN HERITAGE ARCHITECTURE AS RESPONSIVE REFUGEE SHELTERS (CASE STUDY: DOMES OF NORTHERN SYRIA)

Abstract. Syria has been struggling through a continuous conflict for more than nine years so far. This conflict has had a disastrous consequence, for not only Syria urban areas but also its world heritage and historical sites. Moreover, the ongoing conflict resulted in the displacement of over 13 million people that is more than half the population; including more than 6.1 million internally displaced. This long-term encampment is a growing aspect of a growing refugee crisis. The Syrian refugees have to face another crisis in the camps due to a significant shortage of resources and support. One solution was using earthen buildings that have been a traditional architectural style in Syria for 11 thousand years. As a part of the cultural heritage, it depends on community participation and achieves environmental and economic efficiency in addition to preserving memory and identity of the place. This paper discusses the creation of sustainable shelters through the revival of heritage vernacular earthen architecture in northern Syria. A comparative analysis was conducted between the humanitarian agencies shelters (HAS) and different historical vernacular dwellings (HDS) from the same region with an arid steppe climate (hot summer and a short cold winter); they were modelled in numerical thermal simulations framework as a means to assess the shelters’ building energy demand and indoor comfort quality. The comparison resulted in the superiority of the heritage dwelling. The paper is concluded with passive approach optimization to the different historical earthen domes with consideration of the historical characteristics and background.

TOWARDS A SUSTAINABLE AND CONTEXT-BASED APPROACH TO ANTI-SEISMIC RETROFITTING TECHNIQUES FOR VERNACULAR ADOBE BUILDINGS IN COLOMBIA

Abstract. In Colombia earthen buildings, mostly adobe, makes up 80% of the national monumental heritage and historic urban centres. Moreover, vernacular earthen techniques have been largely used for dwellings in rural villages, small towns or informal settlements and represent, nowadays, a huge architectural and cultural heritage of the country. Due the brittle behaviour and low ductility of the building material, characterized by both low tensile and bending strength, earth constructions show high seismic vulnerability; nevertheless, though Colombian earthquake hazard level is considered very high, current national seismic building regulations do not include any reference to earthen architecture. Seismic failure mechanisms most frequently occurring to masonry architecture, as adobe buildings rehabilitation techniques and seismic behaviour improvement practices, have been widely published. This paper aims to investigate possible causes associated to failure mechanisms due to common adobe building practices in Colombia and intervention strategies, to be eventually implemented in order to reduce risks. The paper focuses on strategies and technologies for seismic retrofitting, while evaluating their effectiveness and feasibility through ‘sustainability’ indicators, based on literature quantitative and qualitative data, and strictly related to rural Colombian economic, social and environmental conditions, where available resources are scarce and labour often not qualified.

ANALYSIS AND CHARACTERISATION OF ADOBE BLOCKS IN JOJUTLA DE JUÁREZ, MÉXICO. SEISMIC VULNERABILITY AND LOSS OF THE EARTHEN ARCHITECTURE AFTER THE 2017 PUEBLA EARTHQUAKE

Abstract. The 2017 Puebla Earthquake on 19 September struck a big part of central Mexico causing the loss of historic buildings in several states, being the state of Morelos one of the most damaged in the whole country. Jojutla de Juarez was the most affected locality of Morelos presenting important structural damages or total collapse in the built heritage, being the traditional earthen buildings, made of adobe bricks, the most vulnerable buildings to seismic efforts. Some of the causes which contributed to the poor behaviour of the buildings were the improper handling of the constructive systems and materials, the insufficient resistance of the structures and the problems with the foundations. The adobe houses of Jojutla presented a mixture between the traditional building techniques and industrial materials like concrete, cement and steel; also with irregular heights and plant layouts and inadequate connections between the walls and foundations and roofs, resulting into a higher seismic vulnerability when the earthquake impacted. Also the adobe bricks presented irregularities in its composition and use of additives which resulted in completely different typologies and the loss of the traditional construction techniques. A study was conducted to determine the properties of the remains of the adobe bricks of the houses in Jojutla, considering that the structures were severely damaged and a whole study of the seismic vulnerability would not be convenient due the loss of the physical traditional buildings. The grain size and composition of the adobe samples of the buildings were determined as well as the natural aggregates like straw, sand, and its proportion. A colorimetric study of the adobes and clays was also conducted, analysing the change of colour on account of the aggregates in the bricks. Also the compressive strength of the pieces was tested with two methods: the compression test and the point-load test, in order to obtain the indicative values which could be compared to other patrimonial and vernacular study cases.

Assessment of the effect of natural hydraulic lime on the stabilisation of compressed earth blocks

Earthen construction is an alternative construction method that allows for the reduction of the embodied energy of building materials and the promotion of sustainability in the construction sector. Among the different earthen building techniques available, compressed earth blocks offer a remarkable potential for industrialisation. Due to the drawbacks associated with the use of non-stabilised blocks, such as the impact of weathering, previous researches had addressed the development of compatible stabilisers for performance improvement. Lime is a traditional binder whose properties are compatible with earth, especially when fine particles are present. Yet, there is limited research on the use of natural hydraulic lime, as most previous studies have focused on the use of hydrated lime, which requires an extended curing time.In the present study, two types of natural hydraulic limes (NHL2 and NHL3.5), in ratios ranging from 3% to 12%, were investigated for the stabilisation of compressed earth blocks. The results revealed that the replacement of soil with lime led to a reduction of the bulk density of the samples of up to 12.8% while increasing their mechanical strength by 48–56% and 12–35% in NHL2 and NHL3.5 respectively. Furthermore, the type of lime has a clear influence on the pore size and volume, and consequently, on both the capillary absorption and the absorption under atmospheric pressure. The results suggested that the addition of NHL2 induced an increase in pore size and volume, in line with the behaviour exhibited by hydrated lime, while the opposite took place when NHL3.5 was used.

Digital soil: Robotically 3D-printed granular bio-composites

Organic granular materials offer a valid alternative for non-biodegradable composites widely adopted in building construction and digital fabrication. Despite the need to find alternatives to fuel-based solutions, current material research in architecture mostly supports strategies that favour predictable, durable and homogeneous solutions. Materials such as soil, due to their physical properties and volatile nature, present new challenges and potentials to change the way we manufacture, built and integrate material systems and environmental factors into the design process. This article proposes a novel fabrication framework that combines high-resolution three-dimensional-printed biodegradable materials with a novel robotic-additive manufacturing process for soil structures. Furthermore, the research reflects on concepts such as affordance and tolerance within the field of digital fabrication, especially in regards to bio-materials and robotic fabrication. Soil as a building material has a long tradition. New developments in earth construction show how earthen buildings can create novel, adaptive and sustainable structures. Nevertheless, existing large-scale earthen construction methods can only produce highly simplified shapes with rough geometrical articulations. This research proposes to use a robotic binder-jetting process that creates novel organic bio-composites to overcome such limitations of common earth constructions. In addition, this article shows how biological polymers, such as polysaccharides-based hydrogels, can be used as sustainable, biodegradable binding agents for soil aggregates. This article is divided into four main sections: architecture and affordance; tolerance versus precision; water-based binders; and robotic fabrication parameters. Digital Soil envisions a shift in the design practice and digital fabrication that builds on methods for tolerance handling. In this context, material and geometrical properties such as material porosity, hydraulic conductivity and natural evaporation rate affect the architectural resolution, introducing a design process driven by matter. Digital Soil shows the potential of a fully reversible biodegradable manufacturing process for load-bearing architectural elements, opening up new fields of application for sustainable material systems that can enhance the ecological potential of architectural construction.

The effectiveness of rubber short fibers reinforcing on mechanical characterization of clay adobe elements under static loading

According to the evidence of numerous advantages of earthen buildings, there is an increasing interest to study adobe elements for sustainable development. This paper presents experimental investigation alongside numerical simulation of several adobe elements under compression, direct tension, three-point bending and indirect shear tests to have a better understanding of their basic mechanical properties. Two different mix-design of clay adobes including plain and short tire fibers reinforced adobes with unique soil type, water content and compacting level are provided. The tire fibers are the waste production of tire factories which are hazardous to the green environment. Numerical simulations are conducted in ABAQUS software for further analysis. In this direction, the material constitutive model and the damage indices are defined based on the experimental stress-strain relations which are achieved during this study and the model of concrete damage plasticity was considered in the software. Furthermore, the experimental observations for direct tensile and indirect shear tests were documented by means of a Digital Image Correlation (DIC) technique from a 2-D DIC system. The effectiveness of the added short fibers on the mechanical properties of the reinforced adobe were thoroughly discussed.

Energy performance of earthen building walls in the equatorial and tropical climates: a case study of Cameroon

Energy performance of earthen wall office buildings in equatorial and tropical climates is investigated using a Simulink model and EnergyPlus software. The main aim of this numerical simulation study is to quantify the magnitude of the effect of adding a fibrous material or a stabiliser in the compressed earth block on the energy requirement or thermal comfort of a building taking into account different operating modes of the cooling system (continuous, intermittent and no cooling) in some climatic conditions in Cameroon. For continuous air-conditioned space and intermittent air-conditioned space, the assessment parameters are cooling load and its peak, while it is thermal comfort index for no air-conditioned space. Thermophysical properties of the used earthen materials were previously measured. The results show that the mixing of sawdust or pozzolan with earth material improves its performances for continuously and intermittent cooling space case, and degrades it for non-air-conditioning space case. It can provide a reduction in peak sensible cooling rate by up to 6.3%, 7% and 10% in Yaounde, Douala and Garoua, respectively. The thermal comfort index obtained with earth block wall can be smaller than that of earth block with 8% of sawdust wall by up to 10.41% and 13.03% (in August) in Yaounde and Douala, respectively.

Assessment of Heritage Rammed-Earth Buildings: Alcázar of King Don Pedro I, Spain

Abstract The conservation and maintenance of earthen buildings is crucial, especially when dealing with heritage sites. This normally involves considerable effort in preliminary studies, which must...

Fujian Tulou Rammed Earth Structures: Optimizing Restoration Techniques Through Participatory Design and Collective Practices

Fujian Tulou is a significant part of the international built heritage. Renovation and strengthening of existing Haka Tulou’s earth constructions can ensure a better quality of life for their residents, as well as contribute to a long-lasting prominence of China’s heritage. Previous studies of Fujian Tulou mainly cover habitation patterns, construction features and architectural details. In this research a layout has been summarized of causes of deterioration, pathology of structure, focused on the buildings’ conservation value and restoration, in terms of history, culture and construction technologies. Out of Fujian’s more than 3,000 Tulou, only a few dozen have been awarded the status of World Heritage Sites by UNESCO. Along with that status, the 46 buildings chosen for the award. The buildings which belong to UNESCO’s heritage are on list of possible restoration while the rest remain in disintegration and the villages are getting vacant through years. The answer for the restoration could be found through participation and team work of experts and habitants. A Tulou is usually inhabited by one family clan for several generations, and the enclosed structure allows to the members of the community to work together and participate in a common goal.Therefore, it is necessary to find new intervention techniques for these earthen buildings, or to adapt those already existing —and proved— to the specific characteristics of the material. This is the context in which the present research aims at contributing to the development of grouting and stitching the cracks by means of earthen mortar in rammed earth walls, as collective restoration techniques.

Thermal Performance and Characterization of a Sawdust-Clay Composite Material

In most research, scientists have been interested in the mechanical impact of sawdust on adobe bricks, mainly compressive strength. This present paper is devoted to the characterization of the thermal transport properties of clay-sawdust materials. To evaluate the thermal impact of sawdust on earthen building envelopes, clayey composites with different sawdust percentage additions were developed. The results show that sawdust positively affects the thermal properties of earthen blocks. Indeed, adding 10% of sawdust decreases the thermal conductivity of composites of 30% and improves the thermal resistance of earthen building envelopes of 31%, while reducing their density. Sawdust can therefore be used in smart lightweight brick manufacturing. The experimental results were used to analyze the thermodynamic behaviors of a residential building using Energy-Plus software. Findings results demonstrate that clay-sawdust composites can reduce the energy consumption of conventional and traditional residential buildings by 21% and 5.3%, respectively.

Probing the Person-Patina Relationship: A Correlational Study on the Psychology of Senescent Environments

There is a lack of research on people’s psychological perceptions to decay or patina that is part of the historic environment. Built heritage conservation doctrine and law are based on the assumption that all people have a similar, positive aesthetic perception to patina in the built environment, although there are very few empirical studies that have attempted to confirm or challenge this assumption. This study is based on the statistical analysis of survey data from 864 people in the United States who ranked 24 images of old, decayed building materials and 7 control images of new building materials based on aesthetic qualities, condition, and perceived age. The results indicate that people do not like decayed earthen building materials, concrete, or ferrous metals and have a neutral opinion of the aesthetic qualities of aged brick, preferring new brick as well as aged wood. While there are small differences based on race, ethnicity, and gender, the largest difference in responses is between people who work in the historic preservation/CRM field and those who do not. This finding appears to indicate that people who work in these fields have a different psychological response to decay/patina in the built environment than laypeople, which has important ramifications in terms of decision-making processes regarding interventions in the older built environment.

INTEGRATING EARTHEN BUILDING MATERIALS AND METHODS INTO MAINSTREAM CONSTRUCTION

ABSTRACTEarthen Building Materials and Methods (EBMM) exhibit excellent environmental, health, indoor air quality and affordability benefits. Despite these advantages, EBMM are not yet broadly implemented in mainstream construction. The main barriers and gaps to implementing earthen construction are analyzed through 126 survey responses and 10 in-depth interviews of a range of experts and end-users, and possible solutions to overcoming these barriers are presented. Specifically, the research indicates that according to earthen construction experts and potential homeowners, inability or difficulty in obtaining building permits is the strongest barrier to implementation. Additionally, existing technical data and environmental assessments must be synthesized and enumerated in order to support decision makers in advancing earthen building policy.

Seismic retrofitting of existing earthen structures using steel plates

During past earthquakes, existing earthen buildings have suffered severe damage or total collapse leading to fatalities and major economic and cultural losses. Poor mechanical properties, out-of-plane instability, lack of seismic diaphragms, and low strength of the connections between structural elements are the most common problems with these types of vernacular constructions. In this research, a novel retrofitting solution, based on steel plates, is proposed to enhance the seismic performance of earthen structures while protecting the life of the occupants and reducing the expected damages. A comprehensive experimental program is conducted to evaluate the seismic behaviour of earthen structural components under both unretrofitted and retrofitted conditions. The experimental program includes four cyclic tests of the proposed connections between steel plates and walls, five cyclic tests of earthen piers, and three full scale shaking table tests of 3.50 m high × 0.60 m thick walls. Observed damage states were related to measured drifts (for cyclic tests) and peak ground accelerations (for dynamic tests). Tests results show that the proposed retrofitting technique substantially increases the stiffness, strength, ductility, and stability of the specimens, which reduces damages and permanent displacements. Retrofitted specimen supported accelerations larger than 1.64g at the roof height without collapse; residual drifts for these demands did not exceed 1.1%.