Earthen Building Materials Research Articles

Hierarchical organization and skilled workforces for constructing the Tartessic earthen building at Casas del Turuñuelo (Guareña, Spain)

This article presents the results of the geoarchaeological study of earthen building materials used in a Tartessic public building at Casas del Turuñuelo. The construction dates back to the fifth century BCE and is one of the monumental buildings of Tartessic culture, characterized by its complex architecture, prestige goods, and intentional destruction after a feast and animal sacrifice. We applied an integrated methodology combining macro and micro approaches to investigate earthen construction processes, such as techniques, labour organization, workers’ specialization, and environmental exploitation. The sample mainly consists of mudbricks, but we also include other forms of earthen materials such as mud plasters, mud mortars, and geological soils for comparison. In total, 64 samples from different building parts were studied through X-ray fluorescence, X-ray diffraction, thin-section petrography, and CHN analyses. The results reveal that the workforce involved in the construction process used different resources and presented different skill levels, but was centrally planned and organized. This study reflects on the communities’ knowledge of the environment, the logistic effort and technical skill employed in the building process, and the existence of strong political structures capable of managing the erection of the complex Tartessic buildings.

Surface characterization of consolidated earthen substrates using an innovative multi-analytical strategy

This study evaluates the combined use of innovative non-destructive methods and standard laboratory techniques for assessing the surface effects of various consolidation treatments (i.e., bacterial biomineralization, alkaline activation, colloidal dispersions containing nanolime or nanosilica, and ethyl silicate as a standard) on earthen building materials. It demonstrates that novel portable equipment (i.e., portable digital microscope, air permeameter, and mobile surface (contact angle) analyzer) and advanced strategies for the application and data interpretation of conventional analytical and testing methods (i.e., scanning electron and confocal microscopy, Leeb hardness testing, and visible light spectrophotometry) can yield complementary and extremely valuable quantitative results for the evaluation of consolidation treatments on such complex substrates. Our multi-analytical approach allows a detailed characterization of surface and near-surface features of treated earthen mock-ups. It is possible to disclose significant differences in the film-forming propensity and in-depth distributions of consolidants and their effect on key properties such as surface roughness and appearance, permeability, water behavior, and mechanical properties. Even though, the substrate's inhomogeneity and surface texture has proven to be especially challenging, this methodology offers a promising strategy for long-term in-situ monitoring of treatment performance and weathering behavior of built heritage materials.

Brick by brick: illuminating the cognitive landscape of the past through sensory archaeology

ABSTRACT This contribution explores the use of sensory archaeology and neuroarchitecture in the study of the earthen built environment. First, the paper discusses multi-sensory experiences focusing on earth as a building material. Second, I look at the archaeological remains of building materials to consider the sensory perception of earthen architecture manufacturers in the Eastern Mediterranean during the Bronze Age. In this latter endeavour I draw on Material Engagement Theory (MET), archaeological earthen remains, and ethnoarchaeological data to investigate the sensory aspects of working with earthen building materials. The main goal is to understand interactions between brain, mind, and culture by studying how people contributed to the manufacturing and construction of earthen architecture. While archaeology is quite visual, I argue that material culture, specifically the production of earthen architecture, shaped a multi-layered sensory experience that included all senses, rather than just visual stimulation.

Structural, acoustical, and thermal evaluation of an experimental house built with reinforced/hollow interlocking compressed stabilized earth brick-masonry

With the increasing demand on affordable construction that addresses the global challenges of the modern world, earthen construction is being reintroduced and investigated as a potential sustainable and affordable building method. Compressed stabilized earth blocks (CSEBs) are a common form of enhanced earthen building materials. Previous studies focused on the structural performance of CSEB walls and prisms consisting of one type of bricks with the same mixture, analyzed their thermal and acoustic properties as units only, or evaluated the thermal performance of solid unreinforced CSEB masonry.The present research is the first complete structural, acoustical, and thermal investigation of an experimental house built with a novel reinforced/hollow interlocking compressed stabilized earth brick-masonry (ICSEB) using varying stabilizer contents, compliant with the Egyptian code for building with stabilized soil—Part One: Building with compressed stabilized soil units (EG-SE2016). Methods depend on experimental testing, codified theoretical calculations, finite element analysis, and live measurements. According to the structural experimental testing program, reinforcement was found to triple the load bearing capacity of ICSEB columns and, although minimal rebars were used in the ICSEB walls, it has improved their load bearing capacity by 23% for single walls (125 mm) and 58% for double walls (250 mm). In addition, doubling the thickness of the unreinforced ICSEB walls increased the load bearing capability by 164%, while raising the thickness of the reinforced wall from 125 mm to 250 mm increased the load bearing capacity by more than threefold (3.38). Based on the codified theoretical calculations and findings of the finite element analysis, it is safe to recommend reinforced double ICSEB walls as a reliable construction for a two-story residential building. Acoustically, double ICSEB walls attained the noise reduction index value of 40 dB, which is required by the Egyptian code for acoustic insulation and noise control in residential buildings, to protect against the average outdoor noise levels of 65–70dBA. Thermally, reinforced double ICSEB walls kept the indoor air temperature and relative humidity values within the thermal comfort zone, 23.9–25.7 °C and 28–36%, respectively, despite the fluctuating outdoor temperatures and relative humidities (16–37 °C and 7–88%, respectively). Indoor air temperatures were 1.5–2 °C lower than those of concrete masonry walls. Additional research is required to evaluate resistance to environmental aspects, such as exposure to water, wind, and corrosion, and to further investigate their thermal and acoustical properties.

Optimization in recipe design of interlocking compressed earth blocks by incorporating fine recycled concrete aggregate

Interlocking Compressed Earth Blocks (ICEBs) have recently surfaced as a valuable and innovative inclusion among earthen building materials. They offer workable answers to the common problems with burned bricks and cement blocks. Researchers frequently used river sand in their studies to address and reduce the finer content in soil. This study explored recipes to make ICEBs from construction and demolition wastes. Fine recycled concrete aggregate (FRCA) was used as a soil modification within the ICEBs as a part of this investigation to support eco-friendly, low-carbon product development driven by global climate concerns and the need for improved construction waste management to combat pollution. ICEBs, made by mixing construction and demolition trash, regulate environmental impact and address the scarcity of building materials. Due to the inherent diversity of soil and the lack of a standardized mix design for the manufacturing of ICEB, 40 different mix ratios were generated using the proportionated blends of sand and FRCA. Based on the compressive strength results, the best recipes representing conventional river sand and the FRCA were selected. The prepared samples of ICEBs using the optimized mix recipes of river sand and FRCA were further analyzed for mechanical, thermal, and durability performance alongside the required forensic endorsements, and the test results were enhanced for both ICEBs compared to first-class burnt clay bricks. Sand-incorporated ICEBs achieved 13.72 MPa compressive strength, while FRCA-incorporated ICEBs reached 13.38 MPa. Both ICEBs showed a noticeable improvement in compressive strength compared to various studies. The durability of ICEBs, in terms of water absorption, improved around 70% compared to fired bricks commonly used in the construction industry. The test findings reveal that FRCA incorporated ICEBs showed 14.3% lower thermal conductivity than ICEBs with sand incorporation. Therefore, the use of ICEBs specially designed with FRCA provides the most sustainable alternative to conventional fired bricks used by the construction sector in the developing countries.

Life cycle assessment and life cycle cost analysis of different walling materials with an environmental approach (comparison between earth-based vs. conventional construction techniques in Iran)

PurposeClimate change, environmental concerns, and economic problems pose challenges to the construction sector in Iran, which must provide affordable solutions while addressing environmental issues. Hence, natural earthen building materials are critically needed to reduce energy-intensive and costly construction practices dramatically. The purpose of this paper is to provide a framework for comparing life cycle assessments (LCA) and life cycle costs (LCC), for load-bearing walls of an single-family affordable housing unit in a desert part of Iran, Ardakan City.MethodsTo do so, both LCA and LCC for the unit were performed, considering a cradle-to-site perspective. For this purpose, 22 load bearing wall systems are assessed, including 18 stabilized and unstabilized earthen construction techniques, such as adobe, rammed earth (RE), and compressed earth block (CEB), in addition to four conventional wall assemblies of fired brick (FB), autoclaved aerated concrete block (AAC), ceramic block (CB), and concrete masonry unit (CMU). As well as assessing the environmental impact and life cycle costs associated with the life cycle of each wall, the optimal assembly of the wall is also examined.ResultsResults show that unstabilized earthen walling alternatives have significantly lower environmental impacts than conventional materials.ConclusionsSensitivity analysis indicates that by utilizing local materials to the maximum extent possible, impacts can be further minimized. Considering the results, transportation may even account for a greater proportion of EI than wall components.

Turf Building in Iceland – Past, Present, and Future

Abstract For a millennium, turf was the primary building material in Iceland. It was used for dwellings, outhouses, boundary walls, raised roads, and other man-made structures. Turf is known as an earthen building material in many countries, especially in northern latitudes, but the knowledge of how to build using it has mostly disappeared. As turf was used well into the twentieth century in Iceland, the skilled craft of locating, harvesting, and building with this material has been retained. This is also facilitated by still standing historical buildings and the need for continual maintenance. Archaeologists also benefit from learning about turf as they frequently interpret the remains of turf walls in the archaeological record. This means that Iceland is in a unique position to disseminate knowledge on this important intangible heritage. However, because of a lack of adequate funding and strategies for maintaining the craft, these skills are in danger of disappearing in Iceland as well. In this article, we discuss the state of knowledge on turf, what turf is, the preservation of the intangible building heritage, the revival of interest in turf, and how the various strands of evidence serve as background for the interpretation of turf as heritage and as an archaeological material.

Study of the physicochemical, mineralogical, and geotechnical properties of clayey soils to improve the durability of eco-construction materials in the rural region

This study aims to preserve and improve the durability of earthen buildings in rural areas of Morocco, particularly in the Al Haouz province of the Marrakech-Safi region. In this paper, a survey was conducted to identify defects in earthen building materials and investigate factors that lead villagers to use cement over traditional earth-based construction methods. To propose solutions to these shortcomings, mineralogical, physicochemical, and geotechnical studies were conducted on four soils commonly used as rural building materials. Subsequently, some corrections were implemented in the treatment of raw materials and the production process of compressed earth blocks (CEBs), which were then subjected to mechanical, physical, and morphological characterization. The findings of this study revealed several building pathologies in earthen construction in this region, including ceiling water leaks, formulations made, and cracks. Research shows that the key factors influencing the durability of building materials are particle size distribution, mineralogy composition, moisture content, and construction process.

Satisfaction and representations of raw earth habitat: a case study of Auroville, India

ABSTRACT This exploratory study presents, for the first time, an analysis of how residential satisfaction (RS) can be related to earthen building materials. The study utilizes an ongoing world-renowned project in Auroville, India, which aims to promote the environmentally friendly Compressed Stabilized Earth Block (CSEB) as a substitute for non-ecological fired-brick. The research employs the semantic differential (SD) method as a means to examine satisfaction. It seeks to explain the limitations of CSEB usage compared to fired-brick and compares satisfaction levels among different groups of residents. For the first time, it has been proven through our findings that CSEB has a significant positive impact on RS, while fired-brick demonstrates no influence on RS. The restricted use of CSEB cannot solely be attributed to its level of house-building-material satisfaction (HBMS), as CSEB surpasses fired-bricks in HBMS rating. Despite this, houses constructed with CSEB offer equivalent levels of RS to those constructed with fired-bricks, sparking a resourceful discussion on various interpretations related to RS theories. One perspective posits that CSEB technology may not be widely adopted, while others emphasize the importance of supporting its development despite the anticipated positive behavior toward it.

Exploring mudbrick architecture and its re-use in Artaxata, Armenia, during the 1st millennium BC. A multidisciplinary study of earthen architecture in the Armenian Highlands.

Mudbrick constructions are extremely common in ancient western Asia, including the 1st millennium structures of the southern Caucasus and Armenian highlands. However, in the Caucasus the geoarchaeological study of these materials to provide insight into building practices and social structure is a topic little researched, especially when focusing on the longue durée. Artashat/Artaxata (Ararat region, Armenia) was the capital of the Armenian Kingdom of the Artaxiads, founded in the eighties of the 2nd century BC, but even before this the site was occupied in the Chalcolithic period, (ca. 5200-3500 BC), Early Iron Age (ca. 1200-900 BC) and in the Urartian period (ca. 800-600 BC) as well. All the previous occupation phases showed communities that made extensive use of earthen constructions as determined during past and recent archaeological excavations. This multidisciplinary study seeks to examine mudbrick architecture as a proxy for environmental and social interactions during the 1st millennium BC combining geoarchaeology, archaeobotany and building archaeology. We analyzed changes and continuities in architectural form and practices, alongside reconstruction of technological and social processes, to identify issues of raw material procurement, attestation of re-use, and consistency of building practices. The results of the geoarchaeological analysis of the earthen building materials used in different parts of the ancient city point to a re-use of materials over time.

Quantitative evaluation of thermal conductivity of earth materials with different particle size distributions

The thermal conductivity of earth materials is closely related to density and particle size distribution. However, existing studies on the thermal conductivity of these materials have neglected the influence of particle size distribution, leading to inconsistent results and hindering the quantitative evaluation of the thermal performance of earth materials. To promote the utilization of earthen building materials in energy-efficient design, this study establishes a quantitative assessment model for the thermal conductivity of earth materials, grounded in their microscopic agglomeration morphology and pore structure properties, through experimental analyses and theoretical derivation. The average prediction error of the model is about 1.77%, which improves the precision of characterizing the thermal conductivity of earth materials. Utilizing this model, the impact of clay, sand, and gravel content on the thermal conductivity of earth materials was investigated quantitatively. The findings reveal that the thermal conductivity of earth materials attains its minimum value when the sand content is approximately 37.3%, and diminishes progressively with tthe increase of the clay content. The above findings offer a theoretical foundation for optimizing the thermal performance and fabrication process of earth materials, thereby fostering the integration and application of these materials in sustainable building systems.

A review on the use of date palm fibers to reinforce earth-based construction materials

The use of natural fibers to reinforce earth construction materials is an old concept. Indeed, for some of these materials such as cob and adobe, the use of plant fibers is a common practice. This fiber reinforcement mainly aims to improve the mechanical behavior of earthen materials and reduce shrinkage cracks. Straw fibers are the most commonly used. But nowadays, the concept of fiber reinforcement has expanded to include fibers from various origins. The focus of this paper will be on the use of date palm fibers in reinforcing earthen building materials. The present review discusses the following axes: the origin of these fibers, their properties, the main treatment techniques applied to them before their use, the earth construction techniques concerned by this type of reinforcement, and the impact of date palm fibers on the earth-based materials’ physical, mechanical and thermal properties. The main results and conclusions can be summarized as follows: the reinforcement of earth-based materials with date palm fibers affects their physical properties by decreasing their dry density and increasing their water absorption capacity as the fiber content increases. Tensile strength and ductility are enhanced when increasing date palm fiber content. Compressive strength can increase but decrease when an optimal fiber content is reached. The addition of palm fibers has also improved the thermal insulation of earthen materials. Regarding the durability of earth-based materials, it does not seem to be affected by date palm fiber reinforcement.

Performances of compressed stabilized bricks using phosphate waste rock for sustainable construction

Huge volumes of phosphate waste rock are generated during the extraction of sedimentary ores, and deposited around the mining site, covering large surfaces and causing many environmental problems. This study presents a cost-effective and environmentally friendly solution allowing the valorization of phosphate waste rock (PWR) to produce eco-friendly compressed stabilized earth bricks-CSEB. CSEB is one of the earthen building materials family, offering many advantages in terms of insulation and thermal properties, good mechanical performances, use of local raw materials, and low embodied energy… For the soil classification, PWR was first characterized using chemical, mineralogical, and geotechnical properties. Then, various mixtures were formulated at the laboratory scale using PWR with cement as a stabilizer and red marl employed to enhance the cohesion and brick’s consistency. The objective was to investigate the role of cement and red marls additions, curing conditions, and brick shapes on different CSEB properties. The optimal formulation that satisfied the requirements of the international standards was adapted to the pilot scale, using hollow and solid brick forms with a size of (250*125*75) mm3. The laboratory results showed that the use of 10% cement with 10% red marl seems to be the most adequate. The pilot scale findings revealed that the addition of cement and red marl improves the compressive strength that reaches 5.70 and 2.56 MPa, for hollow bricks in dry and wet states, respectively. For solid blocks, 4.51 and 2.44 MPa were obtained in both states, respectively. The obtained water absorption coefficients respect the requirements of the standards. The thermal conductivity values are acceptable; 0.44 and 0.51 W.m-1.K-1. The TCLP test of the elaborated bricks showed that the concentrations of leached contaminants (Pb, Cd, As, Cr) are below the requested limits.

Thermal comfort and passive survivability in earthen buildings

Earthen building materials have been regaining popularity due to their environmental, economic, and health advantages. Furthermore, given projected thermal survivability in the face of climate change, passive strategies that minimize use of fossil fuels for operational space conditioning are becoming increasingly necessary. Using the lens of passive survivability, this research investigates the abilities of four earthen wall assemblies (cob, light straw clay, unstabilized rammed earth, insulated unstabilized rammed earth) and three conventional assemblies (concrete masonry unit (CMU), insulated CMU, insulated wood frame) to provide adaptive thermal comfort in six distinct climates, with and without passive heating and cooling systems. Residential dwellings were evaluated through simulation with heat and moisture transport algorithms, showing that passive conditioning is especially beneficial with earth assemblies, bringing 25–70% of uncomfortable annual hours into the adaptive comfort zone, alongside strikingly lower diurnal temperature swings in all examined climates, and in all seasons, than conventional walls. Further investigation into the heat and moisture fluxes reveals that the thermal stability of the earth dwellings is provided in part by moisture sorption and evaporation. Together, for the first time, these results show that the thermal performance of earth assemblies can, with well-designed passive heating and cooling strategies, equal or outperform conventional assemblies in a range of U.S. climates, supporting their expanded inclusion in U.S. building codes. This research provides a novel contribution to the thermal performance optimization of earth construction, critically linking thermal and hygroscopic performance with passive design strategies such as shading, natural ventilation, and movable insulation.

Compressed Stabilized Earthen Blocks and Their Use in Low-Cost Social Housing

Earthen techniques have been historically used in construction of housing in Africa, Asia and Latin America. In the past two decades the interest in earthen material has grown considerably, leading to the development of sustainable materials such as compressed earth blocks (CEB), compressed stabilized earth blocks (CSEB) and interlocking stabilized soil blocks (ISSB). Scientific publications from various countries and context have examined the physical aspects of these earthen building materials, but so far, the results are not well connected to housing practices for and by low-income households with their self-organizing skills. This research sought to close this gap by documenting the housing projects where earth blocks are applied in participatory social housing. The study provides an overview of relevant practical examples from the three world regions (Africa, Asia and Latin America), with their cultural and climatic differences, and an analysis of similarities and possibilities. Based on the lessons learned from these examples, recommendations are made on further research on sustainable building materials within social housing practices, which can benefit the scientific community. We propose to set up a worldwide database of housing projects where earthen techniques have been applied responsibly. We conclude and recommend that more high-quality pilot projects with CSEB and ISSB are needed to get a broader picture on the potential of these materials for social housing, and the necessary support for local communities wishing to be involved in these sustainable housing practices.

An experimental study for sustaining the architectural heritage value of traditional houses of Bursa

Bursa, the first capital of the Ottoman Empire, is one of the rare historical cities that has survived to the present day without losing its importance. As well as monumental structures such as mosques and Sultan complexes, traditional Bursa houses are also components of architectural heritage that reflect the identity of the city. The traditional building materials of these houses are wood, stone, brick and earth. Today, these materials are known as ecological building materials and their use is very important to ensure sustainability. Especially the application of traditional building techniques based on the use of these materials in restoration works is of great importance in terms of ensuring sustainability not only from an ecological point of view, but also from economic and cultural points of view. In this context, earthen building material consisting of natural raw materials and created by human hands are seen as ecological and renewable building materials. In different parts of the world, many civilizations have used earthen building materials with different usage techniques in the past. This material has not lost its importance to this day. In this study, the earthen building materials used in traditional Bursa houses are examined and their role in sustainable architecture is pointed out. For this purpose, a case study was conducted on traditional Bursa houses in three different historic neighborhoods; Hisar, Tuzpazari and Reyhan regions. Representative earthen building materials were taken from 22 traditional houses and listed with their qualities for experimental studies. Characterization tests were carried out on the samples taken from these houses. The results of the experiments have been used to develop some recommendations for the successful implementation of restorations that will help to carry out sustainable heritage conservation work in Bursa.

Burnt-Bricks Production Using Extracted Finer Particles from Soil with Fly Ash Addition

Earthen building materials, including mud, adobe, rammed earth, and bricks, have a long history of use in civil engineering construction all throughout the world. Burnt bricks are one of these materials thatis important. However, the availabilityof raw materials for making bricks is limited. As a result, numerous alternatives have been investigated as raw materials for making bricks. These substitutes include fly ash, rice husk and ash, industrial, and agricultural waste. The current study suggests a novel method for producing burnt bricks using extracted finer and fly ash.Finer particle extraction was done through soil washing. Since the extracted finer is having high plasticity index and high linear shrinkage, extracted finer was mixed with 20%, 25%, 30%, 40% and 50% fly ash. Fly ash is an industrial waste; hence the use of fly ash for this kind of production would give a sustainable solution for waste management. Every finer-fly ash combination underwent an Atterburg test to evaluate its qualities, particularly its plasticity index and linear shrinkage. Standard-type mold (220 x 115 x 75 mm) was used to producethe handmade bricks. Compressive strength, flexural strength, water absorption, density, and dimension variations of burned bricks were all examined. Results were compared with SLS 39: Specification for burnt clay bricks. Further, these properties were compared with the same properties of bricks made with soil taken from the brick-making industry mixed with fly ash and industrial available burnt-bricks.Additionally, wire-cut bricks were produced using extractedfiner and 25% fly ash. The dimensional variationof finer-fly ash mixed burnt bricks is decreasing when the fly ash % is increased relative to the mold size. Compressive strength of the Grade 2 category was demonstrated using bricks manufactured with a 25% fly addition, according to SLS 39. According to the aforementioned findings, burnt bricks composed of extractedfiner and fly ash have higher desirable qualities when 25% more fly ash is added. Additionally, it shows that using fly ash results in lightweight bricks.The wire-cut bricks made with this selected mixture give 10.64 N/mm2 of compressive strength and it satisfies the SLS 39 requirements for wire-cut bricks. Also, its water absorption was nearly 16% which is below the SLS required value (18%).

Correlation between relative humidity and the strength and deformation characteristics of unstabilised earth masonry

The mechanical properties of unstabilised earthen building materials are distinctively influenced by changes in material moisture content. However, this moisture-dependency often remains unconsidered in the calculation of the load-bearing capacity of earth constructions. This paper aims to derive a convenient way to sufficiently consider the impact of different material moisture contents on the mechanical properties of unstabilised earth masonry. Therefore, the influence of relative humidity and temperature on the strength and deformation characteristics of unstabilised earth blocks, earth mortar and earth masonry is evaluated by conducting compression tests under various climate conditions. The results show that the compressive strength and the modulus of elasticity are linearly correlated with the relative humidity, whereas changes in temperature at constant relative humidity have no significant influence. To account the distinct moisture-dependency, a general applicable modification factor for unstabilised earthen materials is provided, which enables the adjustment of the compressive strength and the modulus of elasticity in dependency of arbitrary hygroscopic material moisture contents.

‘Another wall of turf’

Excavation of a well-preserved stretch of the rampart of the Antonine Wall east of Watling Lodge, at Laurieston, allowed for the first micromorphological study of its earthen building materials. This revealed that the rampart core, as well as the cheeks, were constructed in well layered courses of turf blocks – but sourced from different grasslands. The evidence differs from macroscopic observations made at other sections in this area where the rampart material had been interpreted as representing a loose earth core with clay cheeks. Our results show that even when the characteristic striped sections indicative of turf are not visible in the field, thin-section analysis can confirm the use of intact soil blocks with the remains of grassed surfaces. It now seems possible that the visible variation between materials in the eastern and western sectors of the Antonine Wall may simply be due to different types of turf used, varying in subsoil composition and topsoil formation, and representing differences in landscape management and survival of vegetation. Combined with macroscopic field recording to identify Roman building practices, our analysis of this section at Laurieston also shows the care that was taken to construct a level, well-draining base for the rampart to avoid slumping and moisture build-up. Further excavations and thin-section analysis elsewhere along the Wall are now needed to confirm whether turf was more extensively used than so far anticipated for the eastern sector and whether the Antonine Wall could possibly have been built completely of turf. Such conclusions would suggest a much more standardised construction process and more extensive grassland exploitation than considered up until now. While our results demonstrate the importance of micromorphological analysis for understanding this earthen UNESCO World Heritage site, our interdisciplinary approach may also have wider relevance for research on linear earthworks in different geographical and chronological settings.

Freezing–thawing curves of earthen bricks with dielectric measurement: Insight into the influence of pore structure and initial moisture content

Under cold climate, poral water of building materials can be exposed to freezing–thawing (F–T) cycles that induce severe frost damage and jeopardize their durability. The F–T curve (variation in ice or unfrozen liquid content with negative temperatures) is a key property to examine and predict the behavior of porous materials under freezing temperatures. However, there is a lack of adapted procedures to evaluate the F–T curves of unsaturated earthen bricks. To fill this gap, this study proposes an experimental protocol, based on time domain reflectometry (TDR), to quantify the remaining liquid water in unsaturated earthen building materials at different temperatures from ＋10 °C to −20 °C. The validity of the device developed to determine F–T curves was verified with low temperature calorimetry (LTC). The dielectric measurement with TDR provides consistent quantification of remaining liquid water content with freezing temperatures. In this study, the influence of initial moisture conditions was investigated through both normal and pathological humid situations of earthen buildings. The normal service situation in winter season was studied with samples conditioned at relative humidity (RH) of RH75% and RH95% which lead to initial liquid saturation SL0 lower than 35% in the tested materials. The moisture pathological case was investigated with initial liquid saturation degrees of 75%, 85% and 95%. The necessary condition of water freezing in earthen materials, in function of their initial saturation ratio or conditioning relative humidity, was examined through a microstructural analysis. This approach also brought understanding about the dependency of the remaining unfrozen water with the freezing temperature.