Earthen Dwellings and Structures

The paper presents the investigations on use of geopolymer as a binder in the manufacturing of stabilised earth and clay compacts. Alkali with different molar concentrations was used to stabilise earthen compacts using natural soil and pure clay minerals along with ground granulated blast-furnace slag (GGBS) and fly ash. The results show that compacts using natural soil and pure clays result in lower compressive strength. The strength drastically increases with the addition of GGBS and fly ash. The optimum mix ratios generated can be exploited for the manufacture of geopolymer bricks.

Alkali activation of clay minerals in soil can be used to form a stabilising phase, such as a geopolymer. Because this requires low-temperature curing, typically <100 °C, it has the potential to be a lower-energy method than fired brick or even cement or lime stabilisation. Whilst this has been demonstrated for individual clay minerals and soils, it is unknown how effective this stabilisation method is for naturally occurring soils from around the world. The potential for stabilisation by alkali activation of a given clay mixture or soil could be approximately, but not fully, predicted from its clay mineralogical composition.

Interfacial bond development between masonry unit and the mortar is due to mechanical interlocking of cement hydration products into the brick pores. The paper presents results of investigations on moisture transport from fresh mortar bed to the cement-stabilised soil brick (CSSB) and its implications on the CSSB masonry bond strength. Three types of mortars (cement mortar, cement-lime mortar and cement-soil mortar) and one type of CSSB were considered in the experiments. The results show that the CSSB’s absorb moisture rapidly in the initial soaking period and attain 75% saturation in about 20 min. The fresh mortars loose considerable amount of water due to brick suction and the water–cement ratio reduces drastically in the initial one hour of contact with the bricks. Use of partially saturated (50–75%) CSSB’s for masonry construction yield maximum bond strength and is therefore recommended.

Cement-stabilised rammed earth (CSRE) structural elements experience bending stresses under lateral loads such as wind and earthquake loads. The flexural strength of CSRE walls is low. Reinforcing rammed earth will improve the flexural strength of rammed earth components to resist lateral loads. There is a need to examine the bond developed between rebar and CSRE matrix. This paper focuses on determining the bond strength between rebar and CSRE and establishes bond force—slip relationships for reinforced CSRE. The variables considered in the study included two dry densities and three types of rebars. Pullout tests were carried out for both dry and wet conditions. The pullout bond strength of rebars in CSRE matrix was found to be greatly influenced by the dry density of CSRE and the type of reinforcement. The bond strength of deformed rebars is higher than the plain rebars irrespective of the specimen density.

Cement-stabilised rammed earth (CSRE) has been used for the construction of load-bearing walls, retaining walls, foundations, etc., across the world. Determining the shear strength parameters of CSRE assumes importance in the analysis of CSRE behaviour under compression and in determining the in-plane shear strength of CSRE walls. There are limited studies on the shear strength parameters of CSRE and hardly any information on Mohr–Coulomb failure envelopes for CSRE. The paper presents the experimental studies on characterising the shear strength parameters and generating the Mohr–Coulomb failure envelopes for CSRE. Triaxial compression tests were performed and the shear strength parameters, cohesion and angle of internal friction were determined in dry and wet conditions. Cohesion of CSRE is found to be a function of cement content irrespective of confining pressure. Mohr–Coulomb failure envelopes of the form $$ \tau_{\text{csre}} = c + \sigma \tan \phi $$ were generated.

Stabilised rammed earth is receiving renewed attention by researchers across the globe due to its improved strength and durability vis-a-vis un-stabilised rammed earth. Rammed earth walls are predominantly subjected to compressive loading and occasionally to lateral loads. The present study focuses on evaluating shear bond strength of cement-stabilised rammed earth using triplet specimens in dry and wet conditions. Three types of bonding techniques were used while casting the specimens and tested at three normal stress levels. The influence of bonding techniques, moisture content and normal stress levels on the shear bond strength is discussed.

The paper presents the results of experimental studies on flowable earth concrete (FEC). It is envisaged that FEC will minimise the cost of formwork to construct load-bearing walls. FEC will be convenient to build monolithic walls with minimum compaction energy. The results on characteristics of FEC such as workability and compressive strength are discussed. The variables considered include clay content of the mix and cement content. The results indicate the feasibility of producing monolithic FEC walls for load-bearing buildings. The compressive strength of FEC can be easily tweaked through the mix design.

The building technique known as rammed earth, made centuries ago in several countries, has been used in Australian civil construction for decades. It aims to inform and update professionals and students about the evolving technology that uses earth as the main building material in contemporary architecture. It aims to share design and building insights that may enrich the knowledge around the limits and needs, and thus contribute to the research of its productive chain, from the material’s supply to its maintenance. Through a relative accumulation of knowledge technique, it is possible to break with some preconceptions or misconceptions about earth as a civil building material.

Adobe blocks can be produced with earth and any stabilizer like lime and Portland cement. Furthermore, there is no need to burn them. So this work aims to characterize two different clays to produce adobe blocks. The clays were characterized by physical and mineralogical properties. The results showed that the strength could achieve 5 MPa at 28 days taking into account both types of clay. This work also brings results about flexural strength. In addition, a comparison between the two methods used for the analysis of the particle size distribution of clays is placed under discussion briefly.

With rapid industrialisation and the increase in popularity of concrete and brick constructions, a decline in earth houses has been observed especially in the rural areas of India. A survey was carried out in five regions of India to understand the technical and social factors favouring/limiting the construction and everyday use of earth houses. As an outcome of the survey, a low societal image of earth houses and durability issues, such as termite infestation and poor resistance to rain water, were the main reasons behind the choice of low-income households in favour of modern building materials over earth construction.

Traditionally, earth has been in use all over the Arabian Gulf for thousands of years, and earth construction methods are not new phenomenon in Saudi Arabia. Stabilised earth in the form of compressed stabilised earth blocks (CSEB) and rammed earth (RE) are also experimented in very few local projects and become successful and promising for the future construction industry of Saudi Arabia. However, being hopeful on the future prospect, it is essential to investigate and explore on the availability of suitable earth in Saudi Arabia for building. Up-to-date literatures on appropriate local soil types for construction are appeared to be very few. The aim of this paper is to investigate on the typologies and suitability of locally available soil appropriate for stabilised earth construction. To achieve the aim, this paper critically reviews the literatures, observes CSEB samples and refines the information to establish whether stabilised earth construction is sustainable considering availability of the soil in Saudi Arabian context.

Biocemented earthen structures like termite mounds can be ten times stronger than the surrounding soil and can last for decades to centuries. Their architecture harvests wind energy for ventilation in order to achieve highly controlled internal environment and has inspired construction of energy-efficient buildings but little is known about the chemical identity of the biocement used in termite construction and the trade-offs between strength and ventilation in a termite mound. By conducting field studies and controlled experiments on Odontotermes obesus termites, we establish the chemical identity of the biocement used in termite mound construction. We also demonstrate how high strength and optimum ventilation is achieved in a termite mound. Our results taken together will provide new insights into cost-effective and eco-friendly building constructions.

Three projects using earthen structures were presented as case studies during the ISES 2007, to reinforce the issue of “acceptability” as critical to the success of promotion of earthen structures in housing. This paper, presented in the ISES 2018, revisits the three projects after 11 years to examine the performance of the construction technologies. This paper takes a close look at how the users of the structures perceive the technologies they have been using. The perception is supported by evidence of how the structures have performed overall including whether and how repairs, additions and alterations have been made. Field visits by the author to two of the case studies and photographic evidence from one indicate that the technology used in the construction of the structures has performed satisfactorily and the building systems are appreciated by the users. Roofing solutions have not performed as expected; however, the use of earth in construction has been very successful and the earthen systems have performed to potential. The performance of the structures and the construction systems, make the case for promotion of earthen constructions in housing projects. Constructing in earth outweighs the social and environmental benefits when compared with the aspirational brick and RCC house.

This paper has investigated flexural strength behaviour of masonry prisms prepared by stabilized mud blocks using Mardini press; interlocking blocks are also prepared by doing modifications to the same. Flexural strength-carrying capacity in normal blocks of size (230 × 190 × 100) and interlocking blocks of 20 (230 × 190 × 80) and 30 (230 × 190 × 70) mm depth was determined by the set-up created and casting prisms as cantilever by applying load at the free end. The test was also carried for prisms cast by different combinations of mortars—cement mortar, lime–cement mortar and soil–cement mortar.

The building sector is responsible for large amounts of waste generated in Europe. Although a growing awareness leads to attempts for material recycling and reuse, recovery rates for high-grade application remain fairly low, as existing buildings are not designed for disassembly. In addition, the lifespan of buildings becomes noticeably shorter and structures are nowadays taken down after 20–40 years. The EU-funded RE4 research project aims to bring back construction and demolition waste (CDW) into the building cycle. This study focuses on the development of earthen construction materials containing a high portion of mineral CDW that constitutes one of the main waste streams in Europe.

The richness of the traditional know-how in ancient India extends to the mud homes built during those times. They are exemplary examples of sustainability through simplicity relevant even today. If revived, they can be great tools to achieve the zero energy goal in mud construction; unfortunately, these methods are being altered or abandoned. Traditional recipes and natural additives used to achieve a durable mud home have survived the tests of time. This paper tries to throw light on some of these forgotten mud mixes that were used in India with specific case studies from the southern state of Kerala. The secondary objective of this study is to evaluate the feasibility of re-introducing them into mainstream construction.

In the majority of cases, earthen construction materials for real buildings require amendment to deliver suitable material properties, which could be some additional strength or resilience to erosion. In modern earthen construction, in India, Australia and other parts of the world, cement and lime have been successfully used as stabilisers, providing both strength and durability benefits. However, the use of cement is detrimental to the green credentials of earthen construction materials, due to the large carbon footprint of that material’s manufacture and, for some time, researchers have been motivated to find more appropriate stabilisers and manufacturing methods. In this paper, we present recent findings from two projects that are linked by this motivation and involve the study of bio-based stabilisers and alternative manufacturing methods for in situ and unit-based materials. Results are presented from laboratory testing of strength and durability of a range of materials, bio-stabilisers and manufacturing processes, indicating that there could be viable alternatives to cement and lime, certainly for many current uses of earthen construction materials.

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

Bhuj-2001, earthquake of magnitude 7.7 (Richter scale), occurred in Kutch region of India and devastated large number of buildings rendering millions of people homeless. It was a daunting task for the government to provide houses for the homeless in a short period of time. Use of local materials such as soil was exploited to build thousands of houses. Hunnarshala Foundation based at Bhuj (India), a not-for-profit organization, embarked upon construction of more than 2000 rammed earth houses in and around Kutch district of India. The paper presents the innovations developed and the methodology adopted to construct 2000 cement-stabilized rammed earth (CSRE) houses within a span of about two years.

Cement stabilized rammed earth (CSRE) can be seen today as a load-bearing wall but the strength and stability of these walls can be increased by adding stabilizer such as cement, lime, and other binder. To stabilize earthen material and to achieve required strength, soil is generally reconstituted using sand, but it can also be replaced with construction and demolished waste (C&D) having gradation similar to sand. It can be further reinforced with natural fiber such as bamboo, which is renewable, natural, and very long growing structures in longitude direction. Bamboo fiber is added at a rate of 1%, 3% by weight to the mixture, and the strength of CSRE prisms were examined under compression. The compressive strength of CSRE increases with increases in dry density, and dry density is sensitive to moisture content. Prisms under compression were studied with and without bamboo fiber and construction and demolished (C&D) waste under dry condition and fully saturated condition, which shows increase and decreases in strength. Result shows that the addition of bamboo fiber in CSRE increases the durability, strength, and sustainability.

The use of conventional cement is still unavoidable in the foreseeable future, and many efforts are being made, in order to reduce its use in building materials. These efforts include the utilization of supplementary cementing materials such as fly ash, silica fume, granulated blast furnace slag, rice husk ash, and metakaolin. Of late, geopolymer is emerging as a binding material which can be adopted for the production of precast products, and masonry unit is one such convenient product which can be produced. Geopolymers, also known as alkali activated products, can be made by using a variety of ingredients that are abundantly available locally. In the present study, combinations of geopolymer–lime, lime–pozzolana cement, tank-bed soil, and brick powder-based masonry units were made. Some of the favourable proportions, based on the compressive strength and water absorption, were considered to produce geopolymer bricks using ‘adobe’ approach. The modulus of elasticity of the masonry units ranged from 1800 to 6000 MPa, which is much higher than the modulus of similar strength, table-moulded bricks of South India. From among the 14 different types of units, 5 were chosen for evaluating the prism strength. The compressive strength of the stack-bonded prisms was found to be in the range of 1.8–5.5 MPa. This is also much higher than that of the prisms made using table-moulded bricks of South India, with cement mortar. It appears that geopolymer-based masonry has a potential to be used as load-bearing wall elements of low-rise structures.

Earth has been used as construction material for thousands of years and still at present earthen shelters are widely inhabited due to their comfort and low environmental impacts. Despite their advantages, earthen materials are brittle and their performance can be enhanced with the addition of fibers. This study addresses the use of different dosages of micro-polypropylene fibers in adobe mixes. The results show that adobe mechanical damage performance is sensitive to the dosage of polypropylene fibers increasing impact strength and reducing drying shrinkage cracking.

Flexural toughness, impact resistance and shrinkage cracking performance of earthen materials can be improved with the addition of fibers. There are limited studies addressing these properties in fiber-mixed adobe. This study investigates the use of jute fibers, a natural one derived from plants, in adobe mixes, including a sensitivity analysis on dosage and lengths of incorporated fibers. The results show that fiber-reinforced adobe’s flexural toughness and shrinkage are sensitive to the dosage, whereas impact resistance is sensitive to both fiber dosage as well as fiber length.

The research discussed in this paper presents the results of a series of compression tests conducted on test cylinders and a limited number of compressed stabilized earth blocks (CSEB) with varying amounts of recycled materials. These included expanded polystyrene (EPS), polyethylene terephthalate (PET), paper and cardboard. A subset of specimens was heated to investigate load–deformation behaviour. Compressive strengths ranged from 1.12 to 2.25 MPa for EPS specimens, while the PET specimens had a range of 1.23–2.23 MPa. A range of 2.31–5.17 MPa was found for the CSEB specimens.

Cement stabilised rammed earth (CSRE) is used for the construction of buildings, especially load-bearing walls. Thinner (<300 mm) CSRE walls are prone to lateral bending before collapsing due to slenderness effects under concentric and eccentric compressions. The paper presents results of an investigation dealing with influence of slenderness and load eccentricity on compressive strength of CSRE walls. CSRE walls of slenderness 10 and 14 were tested for compressive strength by varying load eccentricity between 0 and 1/3rd of the wall thickness. Lateral deflections were monitored across the height of the walls. The results show that the compressive strength of the walls reduces with increase in slenderness and load eccentricity.

Increase in world population and their housing needs with limited resources tend to promote the usage of alternative building materials in the construction industry. Among those alternatives, earth masonry has been given much prominence in the sustainable design process. Although the load-bearing properties of earth masonry have been established by various researches, its dynamic behaviour has not been given due attention. However, a limited number of experimental studies have been conducted on dynamic performance and little attention has been given for numerical studies. This paper covers a review of numerical methods with different softwares, for the sequential procedure, its accuracy and limitations.

The research covered in this paper was aimed at investigating the suitability of the accelerated spray erosion test (ASET) for predicting durability of rammed earth walls. ASET was conducted on several specimens of unstabilised rammed earth, and in order to assess the suitability of the laboratory test as predictor of natural weathering, a field study was conducted to measure the natural weathering of a similar set of rammed earth specimens. The initial results of the study are presented in the paper, with parameters such as compaction effort and moisture content at the time of ramming, as well as soil composition, shown to be important determinants of behaviour.

Errors exist in all measurements, as no test results are perfectly reliable upon accuracy. An attempt made in understanding the error associated in measuring the thermal conductivity of cement-stabilized soil blocks was carried out. The errors such as repeatability and material errors were assessed in the current study. Both the errors will be expressed in relative standard deviations as erepeatability and ematerial. These results can be attributed to variation in how a specimen was cast, stored, and prepared for the experiment and includes aging, material stability, and ambient exposed conditions. The results of repeatability errors were found to be low for all the materials tested. The material errors can be attributed to the material heterogeneity and the inherent characteristics of the materials.

Cob is an earth construction type widespread in Normandy. In this study, thermal and hygrometric behaviour of cob is studied. Two different mixes currently used for cob constructions are used. Several cob formulations are developed by varying fibre content as well as soil mixes. Results show that a higher fibre content leads to a lower thermal conductivity due to thermal conductivity of wheat straw and cob smaller density. Results about hygrometric properties show that knowing hygrometric properties of each component allow to predict cob hygrometric properties. Knowing hygrometric properties allow to determine cob behaviour variation during the building life.

The present study aims to evaluate the impacts of raw material variability (earth and hemp) on hemp–earth performances. This work is performed in the framework of the ECO-TERRA R&D project in collaboration with four French research laboratories, short circuit hemp producers and craftsmen specialized in hemp and earth constructions. This article is focused on the thermal conductivity and mentions preliminary results of the mechanical characterizations. The results are compared to lime–hemp materials. The typical volumetric mass of a dry lime–hemp mixture is about 330–400 kg/m3, which corresponds to a thermal conductivity about λ = 0,11 W m−1 K−1.

The European building sector is moving towards more complex and high-tech building approaches. While focusing on energy efficiency, aspects, e.g. occupant health, sustainability and life-cycle costing are often neglected. This study highlights the potential of earthen plasters in combination with natural ventilation for low-tech solutions. The EU-funded project [H]house established the outstanding performance of earthen materials in light of hygrothermal and air-purifying properties, which were further supported by experimental data from monitoring of naturally ventilated pilot buildings in Berlin. Additionally, [H]house demonstrated through LCC an increased cost-efficiency of earth-based low-tech solutions in comparison with conventional constructions relying on mechanical ventilation.

The sick building syndrome was identified in the mid-twentieth century associated with a number of complaints and environmental discomfort felt by inhabitants of buildings, leading to the development of many diseases and serious disturbances. The indoor air quality has been referred to as one of the main environmental risks to public health. In order to improve the development of construction products to reduce human exposure to aggressive pollutants and health risk, and monitor the improvement of indoor comfort conditions, it is proposed with this article to disclose the beginning of the INDEEd project on the effect of eco-efficient plasters.

It is important to control indoor humidity level in buildings as it influences occupant’s health and comfort. Some materials, when exposed to the indoor environment, help regulate relative humidity levels due to their capacity to absorb and desorb water vapour. The potential of earthen plasters to improve indoor comfort was investigated through experimentation and simulation. Results of clay moisture buffering capacity and computational simulation of the diurnal moisture variation in a clay plastered test room are discussed. This study compares measurement obtained in the laboratory with simulations output and identifies a discrepancy between the two methods in the quantification of the moisture buffering potential.

Vernacular Architecture of many settlements in India uses locally developed mud-based construction techniques for their housing needs which apart from being sustainable are climate responsive. The unique local earthen construction techniques of village Chigule have evolved over a period of time. The planning, earthen construction techniques, spatial organisation, use of local economic and sustainable materials for houses exhibit an eco-sensitive, well-evolved response to climatic and social concerns. This study attempts to document and understand this settlement for its age-old techniques of climate responsive earthen architecture, which unless preserved and conserved may be lost forever.

Typical Assam-type houses (ATH) is a result of local considerations and has withstood catastrophes of earthquake zone 5. But ATH is not the first choice of construction today anymore. Paper infers attributes of bygone ATH and ways to integrate them in prevalent construction techniques. A field study was conducted to detail out vernacularism about its sustenance, decoding planning, design, materials, construction techniques, etc. Proportion of wooden materials used and segmentation of walling are few of many findings which are crucial about ATH. Few pivotal sustainable aspects were also discovered. Combining both may give us an acceptable solution for tomorrow.

Many scholars have recognised vernacular architecture as an important and relevant area of study, although it has not received the due it deserves. The focus of this paper is a study of the use of mud in vernacular building traditions through a case study of a 113-year-old home in Puthiyankam—a village in Kerala. This structure brought to the forefront the use of mud as a material in various contexts. The study draws focus on two stratigraphic contexts—the wall and roof where mud has been used thus bringing out its versatility.

There is no building code recognized standard or guideline for engineering design of rammed earth structures in Canada. Structural engineers are left to do their own research on international design standards, published research and testing results and their own experience to come up with a rational design method that is defensible to their peers and regulators. Alternatively, engineers can choose to design stabilized rammed earth using accepted national standards for concrete or masonry, with the understanding that rammed earth’s material characteristics are not precisely covered by those standards. Case studies of two design processes resulting in the issuance of building permits and construction are examined. The first example follows an ad hoc methodology based on published materials and international codes and design guides. The second example follows attempts to use both the Canadian concrete and masonry design standards. Recommendations for establishing code compliant engineering design methods for rammed earth structures are given.

The hydromechanical behaviour of compacted earth samples was experimentally analysed with a triaxial apparatus at controlled hygrometry and temperature. The results show that the relative humidity at which the samples were stored have a strong impact on the mechanical characteristics of earthen material: both the maximum deviator stress and Young’s modulus decrease with the increase of relative humidity, meanwhile, more plastic characteristics are observed. Non-negligible swelling/shrinkage phenomena induced by variations of relative humidity are also observed. These results are eventually analysed in the light of a fully coupled hygrothermal–hydromechanical model.