Raw Earth Research Articles

Thermal Performance of Lightweight Earth: From Prediction to Optimization through Multiscale Modeling

This study investigates the prediction of the thermal conductivity of lightweight earth and raw earth blocks incorporating plant aggregates. Given the high variability of raw materials, it is not currently possible to predict the thermal performance of this type of material before sample production. This is a major obstacle to using these eco-materials, although their use is widely encouraged to improve building performance under evolving regulatory frameworks such as The French RE2020 standard. The incorporation of plant aggregates into earth-based materials offers improved insulation properties without compromising their mechanical integrity, positioning them as promising sustainable alternatives. Mean-field homogenization techniques, including the Mori-Tanaka as well as double inclusion models, are used to develop predictive tools for thermal behavior, using rigorously selected experimental data. The selected methods are particularly relevant. The Mori-Tanaka model appears to be better suited when the proportion of aggregates is limited, whereas the double inclusion scheme proves its worth when a higher proportion of aggregates is incorporated. This study emphasizes the influence of aggregate types and processing methods on thermal conductivity, highlighting the need for precise formulation and processing techniques to optimize performance. This paper demonstrates the relevance of the applied homogenization techniques applied. It enables the real morphology of the materials studied, such as aggregate shape and intrinsic cracking, to be taken into account. It contributes to the advancement of eco-material modeling toward predictive digital twins, with the goal of simulating and optimizing complex material behavior under various environmental conditions.

Experimental investigation of Catalan vault structures based on earthen materials

The Catalan vaulting have succeeded in reducing reliance on support centers, resulting in lowered costs and expedited construction processes. This research advances the study of Catalan vaulting by exploring innovative, environmentally friendly earth-based materials. The study conducts a comprehensive comparative analysis of load-bearing behaviors across distinct vault elements: those fabricated from terracotta, raw-earth tiles, and shot-earth. Constructed and tested at a 4-meter span, full-scale vault specimens are subjected to varying distributed load configuration, followed by rupture testing employing a linear load at a quarter of the span. Experimental evidence, corroborated by FE results, indicates that both terracotta and raw earth tile vaults offer commendable performance, yet their failure loads are surpassed by vaults constructed using shot-earth. Therefore, shot-earth emerges as a sustainable alternative for constructing vault elements. Furthermore, the study demonstrates that incorporating reinforcement within shot-earth vaults increases their strength and ductility.

Raw earth stabilised by alkaline activation of slag: Effect of clay on slag hydration

Alkali-activated slag is used as a cement substitute to stabilise poured earth materials, aiming to enhance their mechanical properties and decrease their water sensitivity. However, the interaction between electrically charged clay particles contained in the earth and the alkaline solution can modify the consistency and, more significantly, lead to the absorption of chemical elements. This can have a detrimental effect on the stabilisation efficiency. In order to optimise slag activation, it is essential to understand the interaction between the clay and the alkaline medium, and its effect on slag hydration. This study examines the microstructural effects of the interaction between the alkaline solution and clays on slag hydration, through microstructural characterization (SEM, FTIR, and DTA-TGA analyses). The impact of three distinct types of earth and two levels of sodium concentration are investigated. Clayey activity causes changes in alkaline conditions, leading to the formation of hydrates that are typically produced at very high sodium concentrations, such as hydrotalcite and depolymerised C-A-S-H. Only formulations with a sodium concentration higher than 1.6 M provide robustness with respect to the three types of raw earth studied. This alkaline context has a limited effect on the microstructure of the clay particles.

Performance of Earth Plasters with Graphene-Based Additive.

A central debate is the improvement in the mechanical and water resistance of sustainable earthen architecture without additives or stabilizers. This innovative work aims to test the effects of a graphene-based additive, optimized for the improvement in concrete properties, on the strength and water resistance of raw-earth plasters without any stabilizer other than sand. Given the heterogeneous nature of raw earth, three different soils were tested by adding three increasing graphene-based additive contents (0.01, 0.05 and 0.1 wt% of the earth-sand proportion). The link between soil intrinsic properties, i.e., geotechnical and mineralogical properties, and their interaction with the additive were investigated through geotechnical characterization, as well as mineralogical characterization, by XRD and ATR-FTIR analyses. The experimental tests carried out focused on the adhesion properties of the twelve different plasters on standard hollow bricks and on their interaction with water through capillary rise tests and erosion resistance tests. Conclusion from the experimental tests suggests that the graphene-based additive in earth plasters, by increasing the cohesion of the mixture, improves their adhesion performance.

Adobe Bricks of the Champagne Region (France): Characterization of a Chalky Raw Earth Construction Material.

Raw earth bricks made from the soil of the Chalky Champagne region (France) have been used for at least two millennia in construction, a promising heritage in the context of reducing the carbon emissions of buildings. The present experimental study aims to measure the physical, mechanical, thermal, and hydric properties of adobes collected from a local village barn. The results show a high chalk content, estimated at 71%, and a clay content, acting as a binder, of 14%. Despite limited load-bearing capacity, these lightweight adobes are suitable for current single-story constructions, while their hydrothermal properties classify them as excellent moisture regulators for occupants. In association with other bio-sourced materials such as starch-beet pulp bricks, Chalky Champagne adobes yield promising insulating properties, and meet the criteria defined by current energy standards.

Combined impact of dune sand and crushed brick waste on the characteristics of raw earth bricks

The primary motivators behind the renewed focus on employing locally available materials, recycling industrial waste, and utilizing their characteristics for adobe bricks are cost-effective building materials, thermally efficient, consuming less energy and reducing environmental emissions. In light of this, this study examines how the physical characteristics and mechanical behavior of quicklime-stabilized adobe bricks' are affected when dune sand (DS) and crushed fired brick waste (CB) are combined. The thermal conductivity of adobe bricks was also studied. According to the data, the compressive and flexural strengths significantly improved with the addition of 40% CB. A slight strength increase was observed with the incorporation of 20% DS, which is not the case for the other types of sand. Addition of 20% DS to the mixtures resulted in a decrease in the TA and Cb. SEM technique confirmed that the use of CB and DS in the adobe bricks preparation procedure resulted in a reduction of voids in the matrix, thereby improving the characteristics, especially their physical characteristics. Additionally, there was an improvement in the apparent density when the M1 combination was included. This resulted in an increase in the speed at which ultrasonic waves propagated. Similarly, M3 combination helped to reduce the TA and Cb. With regard to M1 combination, it increased the compressive and flexural strength of adobe bricks by 71.75% and 52.23%, respectively, as compared to the RB. Significant increases in elasticity modulus were observed in compression and flexion. The combination of CB and DS slightly increased the thermal conductivity.

Analysis of the thermal performances of uninsulated and bio-based insulated compressed earth blocks walls: from the material to the wall scale

The lively international debate on the future of the built environment has placed emphasis on the possibilities offered by bio and geo-based building materials. Among these, raw earth-based materials offer several advantages associated to their reusability and low embodied energy.Nowadays, several companies are basing their production lines on prefabricated raw earth products, as is the case of compressed earth blocks (from now on CEBs). CEBs are commercialized for the construction of massive vertical envelopes, characterized by a high thermal inertia. Nevertheless, in order to compete with conventional building materials, it is also necessary to guarantee a high thermal resistance.In this work, this issue was solved by the design and testing of full-scale uninsulated and bio-based thermal insulated CEB walls. In this way, the thermal performance of CEB walls can be increased to meet the high energy requirements currently adopted in European Countries. Furthermore, the choice of bio-based insulations represents the main novelty of the study, aimed at finding hygrothermal compatible solutions at a low environmental cost.More in detail, this work reports the results of the thermal and physical material characterization of CEBs and of two innovative bio-based thermal insulations (lime hemp and sugarcane bagasse panels), and compare them with measurements made on full-scale uninsulated and insulated CEB walls. For this purpose, the walls are tested inside a double-room climatic chamber where they are subjected to variable temperatures on their two faces, reproducing typical indoor and outdoor conditions during summer and winter conditions in a continental climate.Results show the enhancement of thermal performances of compressed earth blocks walls when thin layers of bio-based thermal insulations are added. The thermal resistance of weakly bio-based insulated CEB walls is found to be nine times (for the sugarcane bagasse insulated CEB wall) and four times (for the lime hemp insulated CEB wall) higher than that of uninsulated CEB walls. Moreover, the addition of the insulation layers enhances the time lag and the decrement factor values of CEBs walls.

Assessment of hygrothermal performance of raw earth envelope at overall building scale

Environmental challenges in the building sector have made raw earth a significant ecological alternative. The development of sustainable materials and a clear understanding of their behaviour are essential for sustainable construction. This work aims to respond to this societal issue.This investigation uses a HAM-BES cosimulation methodology that integrates dynamic thermal simulation code (TRNSYS) with a hygrothermal transfer model developed by Luikov and solved by Comsol Multiphysics. The study aims to investigate the energy needs of different building envelopes in several climates where there is raw-earth architecture. A comparison between a cob monolayer envelope and a polystyrene insulated polystyrene insulated brick multilayer envelope has been carried out. This study shows that the raw earth monolayer wall has a higher energy need for oceanic and tropical climate with, respectively, 14 and 19%. A decrease in demand has been found for the desert climate. Moreover, it was shown that the coupling of heat and mass transfers results in a notable reduction in energy demand that can reach 11.5% annually and up to 23% quarterly for tropical climate. These findings highlight the efficiency of raw earth materials and stress the importance of thoroughly understanding and incorporating heat and mass transfer dynamics in the evaluation of sustainability for biobased and earth-based construction materials.

Thermal properties of a raw earth-flax fibers building material

The aim of this paper is to investigate the thermal behavior of composite building materials comprised of silt and flax fibers, considering various initial conditions. The experiments were conducted on flax fibers alone, examining factors such as moisture content variation, fibers arrangement, and density. Subsequently, the thermal properties of the earth-flax fiber composite were studied, taking into account the influence of water content and fibers mass content. The thermal properties of both flax fibers and raw earth-flax fibers composite specimens were determined using the experimental unsteady-state method. The results indicate that the thermal conductivity and heat capacity of flax fibers increase with density, temperature, and moisture content. Regardless of fibers density and arrangement of fibers, linear relationships have been established for both thermal conductivity and heat capacity as functions of temperature. Additionally, it was demonstrated that the heat capacity and the thermal conductivity increase with water content, regardless of the percentage of added fibers. Moreover, mixing randomly flax fibers with compacted raw earth material has improved the thermal properties of the composite. This improvement pertains to its insulating capacity, ability to store heat, and, subsequently, its contribution to the thermal comfort provided by such earth composite material when used as a building material.

Shaping the sacred along the Silk Roads: the millenary artistic tradition of making “monumental terracruda sculptures”

This paper presents a depth revision of the technological, material, and symbolic knowledge of what we advocate to be identified as “monumental terracruda sculpture” along the Silk Roads. Through a highly interdisciplinary approach, combining a) the latest results of archaeometric analysis carried out on Buddhist examples, b) the documentation of traditional knowledge in making terracruda sculptures in Buddhist and Hindu religious practices, and c) the systematic review of the archaeological and anthropological literature on this topic, this work brings new evidence for proposing the existence of a common pattern of elaboration of monumental terracruda sculptures, connecting traditional Buddhist and Hinduist artworks with a millenary artistic tradition that uses raw earth as the preferred material for the representation of the sacred. The recognition of this common pattern in the production of monumental terracruda sculptures led to the questioning of the prevailing archaeological narrative of a Hellenistic origin of the technique as well as the causes of its popularity within Buddhism from the 4th century CE onwards. Based on the qualitative and quantitative evidence discussed in this paper, new interpretations about the origin and spread of this cultural expression are finally proposed. Finally, the need for future research that takes a systemic view of the subject is advocated, proposing a multidisciplinary vision that integrates archaeology, archaeometry, ethnographic research and the study of ancient religious texts.

INFLUENCE OF CONSTRUCTION TECHNOLOGY ON THE THERMAL PERFORMANCE OF VERNACULAR HOUSING

The canton of Zapotillo, located in the south of Ecuador, has a hot climate that has led the population to use endemic materials in the construction of their homes. These materials provide a comfortable indoor environment for the inhabitants, with earth, wood and stone being the main structural components of traditional houses. These vernacular houses represent years of empirical research and testing by local builders who have developed unique construction techniques. However, these houses have been overshadowed by new architectural typologies that use modern materials and construction systems with lower thermal performance. In the current landscape of Zapotillo, remains of the first settlements in the area can be found, blending into the overall landscape with contemporary constructions. Therefore, the aim of this research is to analyze the bioclimatic performance of vernacular houses in the canton, focusing on the technical and constructional study of selected cases, seeking to identify parameters that contribute to indoor comfort in relation to local climatic conditions. The research visualizes the energy characteristics of vernacular housing, highlighting the solar protection provided by the use of portals and terraces, as well as the comfort of the raw earth construction system to mitigate the effects of high temperatures during periods of extreme heat. The energy analysis programs Revit Insight, Rhinoceros, Grasshopper and Lady Bug tools are used to measure these variables, with the ultimate aim of rescuing vernacular values and adapting them to new projects, thereby revaluing the concept of traditional Zapotillo housing.

Exploring the integration of bio-based thermal insulations in compressed earth blocks walls

The growing concern about the environmental impact of contemporary construction has posed emphasis on the possibilities offered by bio-based and raw earth construction. The front challenge for the establishment of earth-based technologies in contemporary building markets is the guarantee of high structural and energy performances, while maintaining a low environmental impact. This work focuses on the performance analysis of compressed earth blocks (from now on CEBs) which are currently commercialized for the construction of massive vertical envelopes, with high thermal inertia. However, to obtain an acceptable comfort and an optimized thermal behavior, CEBs walls must also reach a high thermal resistance. This issue can be overcame by the design of insulated CEB stratigraphies using bio-based thermal insulations presenting hygrothermal properties compatible with raw earth-based materials. In this way, the thermal performance of CEBs walls can be increased, while preserving their hygroscopic behavior. In this spirit, this work reports the results of the experimental characterization of three materials: CEB, lime hemp and sugarcane bagasse bio-based insulation panels. It includes their composition, their main physical (dry density, porosity, capillary water absorption), thermal (specific heat capacity, thermal conductivity) and hygrometric (sorption isotherm, water vapor permeability) properties. Finally, these experimental data are used for the implementation of several numerical simulations at a wall scale in a reference climate to estimate the hygrothermal performances of both uninsulated and bio-insulated CEB walls. The simulations allow for a better comprehension of CEBs’ behavior in view of their combination with the chosen bio-based thermal insulations, and give insights into possible moisture-related issues as mold growth or increase of U-value.

Compared Environmental Lifecycle Performances of Earth-Based Walls to Drive Building Envelope Design

Raw earth has useful applications in contemporary buildings as a sustainable and circular construction material. The present study aims to assess the environmental performance of several earth-based wall systems with similar thermal performance, through a life cycle thinking approach. In particular, a life cycle assessment is developed for (a) unstabilized rammed earth (produced in situ), (b) compressed earth blocks (prefabricated in the factory), (c) stabilized rammed earth and (d) light earth, all combined with biobased (natural fibers, e.g., lime hemp, cork) and/or conventional materials for building insulation. Results show benefits in terms of avoided carbon emission, water footprint and embodied energy throughout the production chain and highlight limits and potential improvements. In addition, the CO2 offset by crops is also estimated based on carbon embedded in natural fibers. In particular, light earth wall systems are the most suitable to minimize environmental impacts, while massive constructive technologies (as unstabilized rammed earth) show a higher dynamic thermal performance for intended use in Mediterranean climates.

Prediction of thermal behavior of Earthen-Straw composite material with 3D numerical modeling of a random geometry without overlapping

Nowadays, stabilizing raw soil with straw fibers represents a sustainable eco-building practice. Moreover, the rebirth of the earth’s construction is primarily driven by the material’s thermal properties. In the present work, a 3D study of the earthen-straw composite material’s thermal behavior has been carried out to promote its use in construction and ensure satisfactory living conditions for the building. To consider the most possible influencing factors, the effect of fibers concentration on thermal conductivity was investigated for the straw contents of 5%, 10% and 15% by volume of earthen. Thus, a 3D model with a random distribution of straw fibers considered as cylinders without overlapping was designed under Catia V5. The distribution uses datasets from a hybrid algorithm developed for this purpose, which is then imported to Ansys Software to carry out the simulation allowing the computation of the thermal conductivity of the homogeneous material. It can be concluded that the proposed hybrid algorithm was efficient since the 3D numerical results based on the geometry generated by the algorithm’s output were satisfactory in comparison with those deducted from the 2D study and the existing theoretical models. On the other hand, adding straw fibers in the raw earth matrix with thermal conductivity equal to 0.75 W/(m.K) has enhanced its thermal insulation. Indeed, for 15% of straw fiber’s contents, we have found 0.633 W/(m.K) for the thermal conductivity of the earthen-straw composite material, which is equivalent to a decrease of 15.6% in this intrinsic parameter.

Optimizing Polymer-Stabilized Raw Earth Composites with Plant Fibers Reinforcement for Historic Building Rehabilitation

This research focuses on the optimization of formulation, characterization, and damage analysis of plant fiber-reinforced polyester resin composites (jute and date palm). To better understand the characteristics and mechanical behavior of these materials, this study investigates the influence of resin content and plant fibers on the physico-mechanical behavior of the resin composites. Resinous composites consisting of polyester resin and raw earth were studied using a novel formulation based on an empirical method that follows the principle of earth saturation with polyester resin. Saturation was achieved with a 28% content of polyester resin, which appeared to be an optimal blend for the earth–resin composite. Plant fibers were randomly incorporated as reinforcement in the composites at various percentages (1%, 2%, and 3%) and lengths (0.5 cm, 1 cm, and 1.5 cm). Mechanical tests including bending, compression, and indentation were conducted to evaluate the mechanical properties of the composites. Analysis of fracture morphology revealed that the deformation and rupture mechanisms in bending, compression, and indentation of these composites differ from those of traditional concrete and cement mortar. The obtained results indicate that the composites exhibit acceptable performance and could be favorably employed in the rehabilitation of historic buildings.

Rediscovering raw earth heritage of Champagne area (France): Cartography and typology of a specific adobe vernacular architecture

The building sector has a strong impact on the environment in terms of pollution, through its carbon footprint and waste generation. In this context, raw earth construction is experiencing a revival of interest in its ability to use a local, reusable, and low environmental impact material. Vernacular architecture reflects the evolution of particular know-how, which has been able to adapt to specific factors linked to a nearby environment. Champagne area is one of the last uninvestigated earth heritage territories in France, whereas it presents an original and rich rural, urban, and industrial earth architecture. To cartography raw earth heritage in the studied area and its surroundings, the various buildings and construction practices observed in the field were geolocated on a digital tablet using QGIS software. This work completes the partial inventory that had been started on Champagne territory and reveals local variations and other uses of raw earth never described in the national survey maps of earthen construction techniques. The presence of the adobe heritage corresponds quite well to the area of the chalky Champagne. We notice two different types of boundaries. A first type where adobe architectures are directly replaced by other building materials, and a second type where adobes are combined with and then replaced by other earth construction techniques (cob, wattle and daub). This reveals a dialogue between different constructive cultures. This survey seems to show a certain coherence as to the presence of adobes in the constructions regarding the geological substratum. Our work will allow to characterize the earth used, to valorize the excavated earth in this territory, as well as to raise awareness and promote local raw earth architecture. In addition, the discovery of the use of cob in the Seine valley reveals the richness of this heritage in this geographical sector.

Comparative Study on the Impact of Sand and Lime on the Physical and Mechanical Characteristics of Unfired and Fired Earth Bricks

Earth bricks represent one of the most important and widely used building materials in current era, due to its unique physical and mechanical properties compared to other materials. Earth bricks are available in two main types: raw earth bricks and fired bricks. The physical and mechanical properties differ for each type, which affects their performance in various applications and their long-term durability. Several studies have been conducted to improve the properties of raw and fired bricks and address their weaknesses. In this research, we aim to investigate the effects of adding dune sand and lime on the physical and mechanical properties of raw earth and fired bricks, and compare the results. Sand was added by 25%, while lime was added by 0, 6, 8, 10, and 12% of the soil matrix weight. Initially, we determined the properties of the raw materials used. After creating the samples, they underwent tests for bulk density, longitudinal shrinkage, compressive strength, and flexural strength. The study revealed the positive impact of adding sand on the physical and mechanical properties of raw and fired bricks. It contributed to reducing the bulk density and longitudinal shrinkage of the samples, while increasing their compressive and flexural strength to varying extents. The results also showed the positive effect of lime on the physical and mechanical properties of raw bricks, as long as it was added at a ratio not exceeding 10%. However, the addition of lime to fired bricks affected the physical properties positively but it has a negative effect on the mechanical properties.

Structural and mechanical studies of a ground-granulated blast-furnace slag (GGBS) based binder and its use in earth concrete

The aim of this work is to characterize the mechanical properties with the understanding of the chemical reactions of a ground granulated blast-furnace slag (GGBS) based binder for earth concrete. Both binder paste and earth concrete samples are cured at 20 °C and 100% of relative humidity. Several characterization techniques are conducted, including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (ATR-FTIR) and mechanical tests. The compressive tests are done at 7, 28 and 90 curing days. This study shows that dicalcium silicates found in the binder powder leads to calcium silicate hydrates (C-S-H) formation in the early age. It also reveals the presence of portlandite, leading to the calcium-activation of the GGBS. This latent reaction creates several phases such as C-S-H and C-A-H in the mid and long term. The analyzis of the infrared specters corroborates those results. The C-S-H characteristic bands are identified around 400, 655 and 960 cm-1. C-A-H characteristic peak is identified at 850 cm−1. The mechanical study shows that the compressive strength of the binder reaches 13.9±0.3 MPa, 21.1±0.8 MPa and 25.4±0.7 MPa and the earth concrete 8.9±0.7 MPa, 16.6±0.3 MPa and 18.7±0.2 MPa at 7, 28 and 90 curing days respectively. Those mechanical properties are brought by the hydrates formed during the binder’s reaction. It creates a matrix that bounds the grains of raw earth together. This work highlights the high mechanical properties of earth concrete made out of this binder. It also shows the potential of calcium-activated GGBS and pozzolanic reactions in order to create low carbon earth concrete with good resistance. Such binder may foster the use of earth concrete in buildings, enhancing their thermal comfort and energy efficiency while reducing their environmental impact.

Durability of Raw Earth Blocks Reinforced with Wheat Straw Fibers

The key drivers of the growing interest in the recovery of local materials, particularly land and waste plants, are low-cost building materials, thermal comfort, decreased energy consumption, and decreased carbon dioxide polluting emissions. This work's primary objective is to test a bio-sourced composite material that takes the form of a block of unfinished soil that has been stabilized with cement and blended with wheat straw. This study is being done with the objective of examining the impact of this fiber at different weight percentages (0, 2, 3%, and 4%) on the mechanical behavior, durability, and thermophysical properties of the produced blocks. The results obtained indicated an increase in thermal conductivity, from 2.75 W/mK for the blocks without wheat straw fiber to 0.398 W/mK for those getting 4% of the wheat straw fiber, signifying an improvement in thermal insulation. While retaining the low performance threshold required by the earth construction standard, this improvement was accompanied by an average decrease in mechanical performance.

Influence of sawdust and flax shives on the high temperature mechanical behavior of earthen materials

Earthen materials have recently made headlines due to their high potential reuse in the construction industry. The growing request of earth-based materials is hampered by the lack of information on the fire behaviour of these materials, in particular for issues of instability. Vegetal additions are frequently used in earth construction because they stabilize the clay fraction’s shrinkage property and improve their insulating capacity. The current study focuses on the role the vegetal additions could play in their implementation inside earthen materials, specifically in terms of the latter's high temperature behavior. At various percentages, sawdust and flax shives were added to a raw earth mix. The percentages of those vegetal additions in the earthen matrix ranged between 0 and 7.5 percent of the dry weight of soil. The used additions were characterized before being mixed with soil that was itself characterized also. The manufactured specimens were therefore made up of a mix of raw earth soil mixed with water and vegetal additions, with the characteristics of each addition considered. The specimens were then heated to high temperatures in a furnace programmed to achieve target temperatures of 150 °C, 300 °C, 500 °C, 600 °C and 800 °C at a heating rate of 1 °C/min. The specimen’s residual mechanical properties were then examined. In the absence of vegetal additions, the compressive strength of the specimens increased with temperature. But, the addition of vegetal additions led to a decrease in strength between 150° and 300 °C, which is greater as the percentage of vegetal additions increased. For a lower mass percentage of vegetal additions (2.5%), the compressive strength increased again between 300 °C and 500 °C; and then between 600 °C and 800 °C for all the tested dosages. The comparison between the two types of vegetal additions illustrated the unfavourable influence of a larger size of additions on the residual properties of specimens. In terms of their contribution to the previously determined properties, the sawdust addition outperformed flax shives.