Earth Building Research Articles

Cow Dung Biostabilized Earth Mortars: Reusability and Influence of Cow Dung Processing and Cow Diet

Historically, cow dung has been widely used as a biostabilizer in earth building, although the scientific research on this subject is still limited. The available research provides evidence of the positive effects of this bioaddition on earthen blocks and plasters, as it improves their physical and mechanical properties and durability in water contact. The present research does not aim to characterize biostabilized earthen mortars or to explain the interaction mechanisms between the earth and cow dung components, because this topic has already been investigated. Instead, it aims to investigate strategies to optimize the collection and processing of cow dung so as to optimize their effects when used in earth-plastering mortars, as well as considering the effects of using them fresh whole, dry whole, and dry ground (as a powder); the effects of two different volumetric proportions of cow dung addition, 20% and 40% (of the earth + added sand); the effects of 72 h (fermentation–humid curing) before molding the biostabilized mortar; the influence of the cow diet; and the potential of reusing cow dung stabilized mortars. The results show that as the freshness of the cow dung increases, the mortar’s durability increases under water immersion, as well as the mechanical and adhesive strength. Collecting cow dung fresh and drying (composting) it in a plastic container is more efficient than collecting cow dung that is already dry on the pasture. The cow diet and the use of dry (composted) cow dung, whole or ground into a powder, does not result in a significant difference. A 72 h period of humid curing fermentation increases the adhesive strength and durability under water. The proportion of 40% promotes better durability under water, but 20% offers greater mechanical and adhesive strength. Finally, cow dung addition does not reduce the reusability of the earth mortar. The new mortar obtained by remixing the mortar with water presents increased properties in comparison to the original reference mortar with no cow dung addition. Therefore, the contributions of this research are innovative and important, offering technical support in the area of biostabilized earth-plastering mortars. Furthermore, it is emphasized that cow dung addition can be optimized as an efficient traditional solution to increase the mechanical resistance, but especially to increase the durability of earth mortars when in contact with water. This effect is particularly important for communities lacking financial resources, but also reveals the possibility of using eco-efficient waste instead of binders obtained at high firing temperatures.

Primitive asteroids as a major source of terrestrial volatiles.

The origins of Earth's volatiles are debated. Recent studies showed that meteorites display unique mass-independent isotopic signatures of the volatile element Zn, suggesting that Earth's Zn originated from materials derived from different regions of the Solar System. However, these studies largely omitted meteorites from the differentiated planetesimals thought to represent the Earth's building blocks, which underwent melting and substantial volatile loss. Here, we characterize the mass-independent Zn isotope compositions of meteorites from such planetesimals. We incorporate these results in mixing models that aim to reproduce Earth's abundance and isotope compositions of Zn and other elements. Our results suggest that, while differentiated planetesimals supplied ~70% of Earth's mass, they provided only ~10% of its Zn. The remaining Zn was supplied by primitive materials that did not experience melting and associated volatile loss. Combined with other findings, our results imply that an unmelted primitive material is likely required to establish the volatile budgets of the terrestrial planets.

Firing the wall: A novel way to protect earth buildings

It is widely recognized that external earthen renders are susceptible to accelerated degradation caused by environmental factors. Therefore, chemical stabilization has become a common approach to address this issue. This study focuses on the stabilization of earth renders by heat treatment, considering criteria such as energy efficiency and the judicious use of resources. Different earth rendering mortars with additives such as wheat paste and horse dung were investigated. These were subjected to surface heat treatment at 400 °C for one minute. Changes in mechanical properties, including shear strength, adhesion and water erosion resistance were examined. The results showed that surface heat treatment at 400 °C improved water erosion resistance but negatively affected shear strength and adhesion to the adobe substrate. Interestingly, the mortar containing wheat paste showed the least reduction in shear strength and adhesion, with a 16 % decrease, while it experienced a water erosion resistance. The phenomenon was observed in all specimens and is attributed to the microstructural changes induced by the irreversible processes of dehydration and dehydroxylation, which alter the clay components on the surface of the earthen render. Overall, heat treatment shows promise for improving the durability of earthen renders against environmental degradation.

Energy performance of rammed earth building: A Kathmandu valley case study

Energy performance of rammed earth building: A Kathmandu valley case study

Compressive Strengths of Cube vs. Cored Specimens of Cement Stabilized Rammed Earth Compared with ANOVA

Cement-stabilized rammed earth (CSRE) is a variation of the traditional rammed earth building material, which has been used since ancient times, strengthened by the addition of a stabilizer in the form of Portland cement. This article compares the compressive strength of CSRE determined from specimens cored from structural walls and those molded in the laboratory. Both types of specimens underwent a 120-day curing period. The tests were conducted on specimens with various grain sizes and cement content. An analysis of variance (ANOVA) was performed on the obtained results to determine whether it is possible to establish a conversion factor between the compressive strength values obtained from laboratory-molded cubic samples and those from cored samples extracted from the CSRE structure. The study revealed that the compressive strength of CSRE increases significantly over the curing period, with substantial strength gains observed up to 120 days. The results indicated no statistically significant difference in the mean unconfined compressive strength (UCS) between cubic and cored specimens for certain mixtures, suggesting that a shape coefficient factor may not be necessary for calculating CSRE compressive strength in laboratory settings. However, for other mixtures, normal distribution was not confirmed. These findings have implications for the standardization and practical application of CSRE in construction, highlighting the need for longer curing periods to achieve optimal strength and the potential to simplify testing protocols.

Effect of Cow Dung Additions on Tropical and Mediterranean Earth Mortars-Mechanical Performance and Water Resistance.

Cow dung (CD) is a material that has been used for millennia by humanity as a stabilizer in earth building techniques in vernacular architecture. However, this stabilization has been little addressed scientifically. In this study, the effect of CD additions was assessed on earth mortars produced with one type of earth from Brazil and two other types from Portugal (from Monsaraz and Caparica). The effect of two volumetric proportions of CD additions were assessed: 10% and 20% of earth + sand. The German standard DIN 18947 was used to perform the physical and mechanical tests, and classify the mortars. In comparison to the reference mortars without CD, the additions reduced linear shrinkage and cracking. An increase in flexural and compressive strengths was not observed only in mortars produced with earth from Monsaraz. In mortars produced with the earth from Caparica, the addition of 10% of CD increased flexural strength by 15% and compressive strength by 34%. For mortars produced with the earth from Brazil, the addition of 10% of CD increased these mechanical strengths by 40%. The increase in adhesive strength and water resistance promoted by the CD additions was observed in mortars produced with all three types of earth. Applied on ceramic brick, the proportion of 10% of CD increased the adherence by 100% for the three types of earth. Applied on adobe, the same proportion of CD also increased it more than 50%. For the water immersion test, the CD additions made possible for the mortar specimens not to disintegrate after a 30 min immersion, with the 20% proportion being more efficient. The effects of the CD on mechanical performance, including adhesion, were more significant on the tropical earth mortars but the effects on water resistance were more significant on the Mediterranean earthen mortars. CD has shown its positive effects and potential for both tropical and Mediterranean earthen plasters and renders tested, justifying being further studied as an eco-efficient bio-stabilizer.

Follow the Trace: Becoming a Seismo-Detective with a Campus-Based Raspberry Shake Seismometer

Abstract Seismic signals, whether caused by earthquakes, other natural phenomena, or artificial noise sources, have specific characteristics in the time and frequency domains that contain crucial information reflecting their source. The analysis of seismic time series is an essential part of every seismology-oriented study program. Enabling students to work with data collected from their own campus, including signals from both anthropogenic and natural seismic sources, can provide vivid, practical examples to make abstract concepts communicated in classes more concrete and relevant. Data from research-grade broadband seismometers enable us to record time series of vibrations at a broad range of frequencies; however, these sensors are costly and are often deployed in remote places. Participation in the Raspberry Shake citizen science network enables seismology educators to record seismic signals on our own campuses and use these recordings in our classrooms and for public outreach. Yale University installed a Raspberry Shake three-component, low-cost seismometer in the Earth and Planetary Sciences department building in Summer 2022, enabling the detection of local, regional, and teleseismic earthquakes, microseismic noise, and anthropogenic noise sources from building construction, an explosive event in a steam tunnel, and general building use. Here, we discuss and illustrate the use of data from our Raspberry Shake in outreach and education activities at Yale. In particular, we highlight a series of ObsPy-based exercises that will be used in courses taught in our department, including our upper-level Introduction to Seismology course and our undergraduate classes on Natural Disasters and Forensic Geoscience.

The Earth atmosphere‐like bulk nitrogen isotope composition obtained by stepwise combustion analyses of Ryugu return samples

AbstractThe nitrogen isotope compositions of two samples returned from the asteroid Ryugu were determined using a stepwise combustion method, along with Ivuna (CI) and Y‐980115, a CI‐like Antarctic meteorite, as references. The two Ryugu samples A0105‐07 and C0106‐07 showed bulk δ15N values of +1.7 ± 0.5‰ and +0.2 ± 0.6‰, respectively, significantly lower than Ivuna with +36.4 ± 0.4‰, but close to Y‐980115 with +4.0 ± 0.3‰. The Ryugu samples are further characterized by C/N and 36Ar/N ratios up to 3.4× and 4.9× the value of Ivuna, respectively. Among all Ryugu samples and CI chondrites, a positive correlation was observed between nitrogen concentrations and δ15N values, with samples with lower nitrogen concentrations exhibiting lower δ15N. This trend is explained by a two‐component mixing model. One component is present at a constant abundance among all CI‐related samples, with a δ15N value around 0‰ or lower. The other varies in abundance between different samples, and exhibits a δ15N value of +56 ± 4‰. The first 15N‐poor endmember is seemingly tightly incorporated into a carbonaceous host phase, whereas the 15N‐rich endmember can be mobilized and decoupled from carbon, potentially because it is in the form of ammonia. Asteroid materials with volatile compositions that are similar to those reported here for the Ryugu samples are attractive candidates for the volatile sources among Earth's building blocks.

Experimental study on thermal and humidity properties of modified rammed earth buildings in winter

Rammed earth materials have been used in traditional buildings for thousands of years. Currently, with the interest in environmentally friendly societies, rammed earth construction has regained attention owing to its characteristics of energy conservation, environmental protection, low cost, and local material extraction. In this study, cement, gravel, sand, and polypropylene fibers were used as the modifying materials of rammed earth. The thermal and humidity physical parameters are measured at different moisture contents after modification, and the isothermal hygroscopic curves are fitted. The experimental findings demonstrated positive correlations between the specific heat capacity and thermal conductivity and the moisture content. The temperature and humidity of a modified rammed earth test building were recorded for seven days during winter. The test findings revealed that, throughout the test, the moisture content in the middle of the wall was consistently higher than that in the inner surface. When the outdoor temperature fluctuation was 14.95 °C, the inner surface temperature and indoor temperature fluctuation were 2.73 °C and 3.08 °C, respectively. Moreover, the inner surface temperature of the wall became maximum 7–8 h after the maximum outer surface temperature is reached, on average. The above data show that a modified rammed earth wall has exceptional heat and moisture storage capacities as well as heat and moisture buffering characteristics, which can reduce fluctuations in indoor temperature and humidity and create a more comfortable indoor living environment.

Quantification and Optimization of Compaction Energy Used in Earth Construction: Case of Static and Dynamic Compaction

Earth construction is a sustainable and environmentally friendly approach to building. In addition to their good thermal performance, earth materials are abundant, inexpensive, and readily available, reducing the need for resource-intensive materials like concrete and steel. Regarding the construction process of earth structures, which is based on compaction, there is often a difference between the laboratory compaction process and the onsite one. The energy consumed onsite to produce earth structures is still approximative and uncontrolled, which affects considerably the mechanical performances of earth walls. Then, the investigation of the optimal compaction energy is necessary. To optimize the on-site compaction energy used in rammed earth (RE), an experimental study is carried out to compare the dynamic compaction usually applied to produce RE walls to the static compaction using a mechanical press. By considering increasing dynamic and static energies, the physical and mechanical properties are analyzed for each case. The obtained results show that RE walls can be replaced by prefabricated pressed earth blocks where the compaction energy is reduced by 60% and the compressive strength is enhanced by 70% using static compaction, thus achieving 4 MPa without stabilization. This solution allows to reduce the execution time and to control the quality of earth buildings.

Maximizing fiber content in 3D-printed earth materials: Printability, mechanical, thermal and environmental assessments

Earth building materials are experiencing a new renaissance with novel avenues in advanced manufacturing methods such as 3D printing. However, current mix designs are still limited to little to no fiber reinforcement, which can improve ductility and thermal resistivity of the fabricated building assemblies. This research develops 3D printable earth-fiber composites while maximizing natural fiber content for low-carbon and high-performance materials in additive manufacturing. A range of mix designs are formulated and characterized for their printability, mechanical, thermal, and environmental carbon storage performance. The results of this work present successfully developed novel earthen mixtures with natural fiber content ranging from commonplace “cob” (2%wt fiber) to newly developed “light fiber clay” (up to13%wt fiber content and 49% by total volume), incorporating a range of agrowastes products, including wheat straw, hemp, banana, and kenaf fibers. The performance assessment results showcase meaningful improvement of the fiber-reinforced mix designs as opposed to the earthen counterparts, with up to 125% higher compressive strength and up to 86% lower thermal conductivity. The significance of this work lies in the advancement of sustainable and circular materials and assemblies for future manufacturing of socially equitable built environments.

Methodology to classify high voltage transmission poles using CNN approach from satellite images for safety public regulation application: Study case of rural area in Thailand

It is necessary to ensure security and community safety around High Voltage Transmission Poles (HVTP). Legislation requires a safety perimeter around HVTP and the High Voltage Lines (HVL) where no building and tree can be located. However, surveying thousands of kilometers of circuit is an expensive and challenging task that is currently performed by human inspection. Therefore, the use of automatic detection methods enables to facilitate the inspection is necessary to reduce time and cost. Convolutional Neural Network (CNN) is proposed in this work to detect, from Google Earth images, buildings and trees within the safety perimeter of HVTP. A dedicated 3 class (House, forest and HVTP) dataset of approximately 1 million tiles with a resolution of 0.09 m/pixel is created. Tiles size for trees and building classes is 64 × 64 pixels while for the HVTP 128 × 128 pixels is used. Three CNN models are built and optimized to classify each of these classes. Models validation shows that, except for houses where the accuracy is only 84 %, the other two classes have an accuracy of over 89 %. Moreover, by analyzing the classified HVTP, type can be identified. Finally, buildings and trees within the safety perimeter around the HVTP can be identified and displayed on the image demonstrating the usefulness of the tool.

RAMMED EARTH CONSTRUCTION: A CIRCULAR SOLUTION FOR SUSTAINABLE BUILDING

The building and construction sector is one of the most harmful industries to the environment, responsible for producing high levels of greenhouse gas (GHG) emissions, energy consumption, and waste. Rammed earth, a traditional building technology is deemed as a promising solution to tackle these challenges. In addition, the low level of skill required for rammed earth buildings paves the way for self-built activities. This paper presents the preliminary findings of an ongoing research study focused on the rammed earth construction technique. The primary objective is to assess its sustainability and circularity within the context of Europe and the Mediterranean. The methodology employed is based on an analysis of rammed earth techniques and a review of relevant regulations related to the selected context. The analysis includes case studies of contemporary European rammed earth buildings. They aim to illustrate possible design strategies that incorporate rammed earth alongside well-established construction technologies. These case studies also shed light on how the integration of various construction technologies introduces circularity variables into buildings, thereby influencing their overall sustainability. These variables are contingent upon the techniques, technologies, and performance characteristics of the selected building elements. As a result of this analysis, the paper initiates a discussion on the role that rammed earth constructions can play in the development of sustainable hybrid buildings.

Improvement of Mechanical Properties of Compressed Earth Blocks with Stabilising Additives for Self-Build of Sustainable Housing

Earth building technologies are increasingly being used to promote a natural and sustainable construction model and to empower self-building in resource-limited areas. This work focuses on investigating the use of different types of stabilising additives in compressed earth blocks (CEBs). To this end, empirical studies and laboratory analyses of earth samples taken from different sites in Ecuador were combined. Once the most suitable earth for use as a building material was determined, four types of CEBs were produced using equipment designed ad hoc to encourage self-building: earth-based, fibre additives, cementitious additives, and additives of other origin. The panels were characterised by means of compression tests to analyse their mechanical behaviour, obtaining the most promising results for the additivated samples with the highest percentage of cement and for the sample containing ground reeds, with a compressive strength of 3.3 MPa and 0.7 MPa, respectively. These samples were then subjected to more extensive tests using digital image correlation to analyse their full field strains and cracks, where the samples stabilised with cement showed a more homogeneous and consistent behaviour. Finally, an economic and comparative study with conventional construction systems was carried out to demonstrate the feasibility of using the proposed earth materials for cleaner and more economical buildings, mainly due to cost savings and lower pollution in terms of transport when using local resources.

Research on the non-use value of rammed earth buildings in Shaxi Ancient Town based on CVM

Architectural cultural heritage not only enriches the cultural landscape but also drives economic activity, although its value is often underestimated by the market. This article uses the rammed earth buildings of Shaxi Ancient Town as a case study, quantifying their non-use value through the contingent valuation method, and explores factors influencing public willingness to pay using correlation analysis and binary logistic regression models. The results show that respondents have a high support rate (72.9%) and willingness to pay (26.23 RMB per person) for the conservation and development of rammed earth buildings. The total non-use value reached approximately 29.79 million RMB, demonstrating the significant economic potential of these structures as architectural heritage. This provides critical insights for the conservation and development of rammed earth architecture in China and calls for enhanced recognition and protection efforts from all sectors of society.

Influence of crack propagation on the seismic behavior of historic rammed earth buildings: The Tower of Muhammad in the Alhambra (Spain)

The presence of defects in the form of cracks is frequent in rammed earth historic buildings located in seismic zones. The influence of these cracks, however, has not been directly taken into account in the numerical models for this kind of structures existing to date in the literature. In this light, this study presents an analysis of a FEM model of a heritage rammed earth structure – Tower of Muhammad of the Alhambra – under gravity loads and a seismic action, with and without the existing cracks, with the aim of assessing their influence. The results show that the inclusion of cracks in the model significantly influence the structural behavior of the building, changing the stress distribution and reducing its stiffness and load capacity. The model with cracks is also able to accurately show damage location in the walls due to crack propagation.

Seismic Performance of a 1:4 Scale Two-Story Rammed Earth Model Reinforced with Steel Plates Tested on a Bi-Axial Shaking Table

During the 16th and 17th centuries, Latin American cities adopted earthen construction techniques from European colonizers. As a result, rammed earth (RE) buildings now occupy an important place in Latin America’s cultural heritage. However, earthquakes around the world have shown that unreinforced earthen constructions are highly vulnerable. For several years, researchers in northern South America have been proposing a technique that consists of installing confining steel plates (or wooden elements) on both sides of the RE walls to form a grid. This system has shown excellent performance in controlling seismic damage and increasing strength and ductility capacity. Although researchers have tested full-scale one- and two-story earthen walls under pseudo-static loading in the laboratory, and one- and two-story earthen walls at 1:1 and 1:2 scales on uniaxial and biaxial shaking tables, the behavior of a complete reinforced module (one- or two-story) on a shaking table has never been assessed. The present study presents the results of shaking table tests performed on two-story RE modules at 1:4 scale. The experimental data indicate that the retrofit system with confining steel plates was effective in reducing the seismic damage of earthen constructions. In addition, the comparison of the results of the 1:4 scale tests with the 1:2 and 1:1 scale tests previously conducted by the researchers shows that the acceleration levels of the equivalent prototypes are in the same order of magnitude for the three scales.

Shrinkage Behavior of Stabilized Earth Bricks Reinforced with Wheat and Barley Straw

Due to its ecological and financial benefits, earth building has gained global attention, with earth bricks being extensively used. Shrinkage and crack development have a considerable impact on the performance and quality of earth bricks. This study employs laboratory experiments to examine the shrinkage behavior of earth bricks reinforced with wheat and barley straw. In addition to this, the impact of cement and gypsum additives is examined. The obtained results indicate that increased fiber content reduces crack formation effectively. However, higher levels of cohesive soil have been shown to have a negative influence on shrinkage behavior. In general, higher fiber contents contribute to the improvement of earth brick performance. These findings offer useful insights for improving the composition and characteristics of reinforced earth bricks, resulting in enhanced performance and quality in sustainable construction practices.

Energy-efficient residential building in Uzbekistan using local renewable raw materials based on the historical layout of housing

This article delves into the benefits of using low-tech, renewable, and local materials in architecture. Specifically, it compares the use of clay and straw with modern construction techniques, highlighting the significantly lower energy costs associated with the former. Through studies of thermophysical conditions, the thermal properties of walls made from these materials have been determined, which plays a crucial role in creating a comfortable microclimate inside buildings. Furthermore, research has identified buildings at risk due to their load-bearing capacity, leading to the development of construction methods for strengthening earthen walls that can be applied in building design and construction practice. Thanks to these newly developed methods and technologies, the construction of earth and straw buildings is now possible on a wider scale, including both standard and special designs.

Bayesian inference on the isotopic building blocks of Mars and Earth

Elements with differing siderophile affinities provide insights into various stages of planetary accretion. The isotopic anomalies they exhibit offer a deeper understanding of the materials responsible for the formation of terrestrial planets. By analyzing new iron isotopic anomaly data from Martian meteorites and drawing insights from published data for O, Ca, Ti, Cr, Fe, Ni, Sr, Zr, Mo, Ru, and Si, we scrutinize potential changes in the isotopic composition of the material accreted by Mars and Earth during their formation. Our methodology employs a Bayesian inference method, executed using a Markov Chain Monte Carlo (MCMC) algorithm.The Bayesian method helps us balance the task of emulating the compositions of the terrestrial planets (reflected in the likelihood) with the flexibility to explore the isotopic compositions of mixing components within permissible intervals (indicated by the priors of the nuisance parameters). A Principal Component Analysis of isotopic anomalies in meteorites identifies three main clusters (forming the three parts of the isotopic trichotomy): CI, CC=CM + CO + CV + CR, and NC = EH + EL + H + L + LL. We adopt CI, COCV, O, and E as endmember compositions in the mixtures. We are concerned here with explaining isotopic anomalies in Mars and Earth, not their chemical compositions. Previous studies have shown that Earth's chemical composition could not be well explained by solely considering undifferentiated meteorites, as it requires incorporation of a refractory component enriched in forsterite. The endmember chondrite components considered here are assumed to be representative of isotopic reservoirs that were present in the solar nebula, but the actual building blocks could have had different chemical compositions, and we use cursive letters to denote those putative building blocks (CI for CI, COCV for COCV, O for O, and E for E).Because Earth's mantle composition is an endmember for some isotopic systems, it cannot be reproduced exactly by considering known chondrite groups only and requires involvement of a component that is missing from meteorite collections but is likely close to enstatite meteorites. With this caveat in mind, our results suggest that Earth is primarily an isotopic mixture of ~92% E, 6% CI, and < 2% COCV and O. Mars, on the other hand, appears to be a mixture of ~65% E, 33% O, and < 2% CI and COCV. We establish that Earth's CI contribution substantially increased during the latter half of its accretion. Mars began accreting a mix of O and E but predominantly accreted E later.Mars' changing isotopic makeup during accretion can be explained if it underwent gas-driven type I migration from its origin near the O - E boundary to a location well within the E region during the first few million years of solar system history. Earth's later increased CI contribution may be attributed to the stochastic impact of an interloper carbonaceous embryo that moved inside the inner solar system region while nebular gas was still present, and subsequently participated in the stage of chaotic growth.The discovery that a significant portion of Earth's building blocks closely resembles enstatite chondrites contrasts with recent findings of Si isotopic anomalies in enstatite chondrites when compared to terrestrial rocks. We suggest that this discrepancy likely stems from insufficient correction for high-temperature equilibrium isotopic fractionation, whether of nebular or planetary origin. With appropriate adjustments for this influence, both the silicate Earth and enstatite chondrites exhibit comparable Si isotopic anomalies, reaffirming a genetic link between them.