Fire Behavior of Raw Earth Bricks: Influence of Water Content and Cement Stabilization

This study focus on the effects of both water content and cement stabilization on the fire behavior of earth bricks. To observe the effect of cement stabilization, two materials are formulated: raw earth with only soil and water, and stabilized bricks with soil, water and cement (3.5% by mass of soil). Since the material’s mechanical strength can strongly influence its fire behavior, the raw bricks were compacted at 50 MPa to reach a compressive strength similar to the one of stabilized bricks. Four different water contents were tested; dry state obtained with oven drying and three others achieved through equalization at 50%, 75% and 100% of relative humidities. Bricks are then subjected to an ISO 834-1 standard fire. Results show that water content has caused a thermal instability behavior on the raw earth bricks after equalization at 50% and 75% relative humidities. Thermally stable bricks displayed a noticeable diffusion of cracks on their heated face. Furthermore, cement stabilization helps to prevent from thermal instabilities.

Starch Reinforcement of Raw Earth Constructions

The restoration, the protection, or the creation of earthen buildings require improving the mechanical strength of the material. The first way to do that is to use inorganic additives, but these additives change the structural properties of earth and have a high carbon footprint. In contrast, the other way to consolidate is the use of organic additives such as vegetal derivatives that rearrange the minerals in the earth, with the lowest carbon footprint as they are from waste management. After preliminary tests with ten different organic additives from traditional recipes, we found that wheat starch improves the earth strength up to 50 %. In this study, we related the mechanical strengthening to the physicochemical interactions between clays and starch. We focus on three clays that represent the three main groups of clays: kaolinite, illite and montmorillonite. For this study, we mainly focused on compressive test and rheological tests. We showed that the improvement of the mechanical strength with starch is depending on clay nature and their chemistry. Then, we can recommend formulations based on the earth nature for new sustainable buildings. Furthermore, we can understand why it was an interesting way to use starch as a strengthening agent in traditional recipes and how it could be used to repair and protect buildings made of earthen material.

Analysis of the mechanical behavior of adobe walls without reinforcement through computational modelling

The construction of civil structures on land has played an important role for centuries, however, due to the seismic requirements and the minimum safety standards that are currently required for any structure, this type of construction has been lagged, it is denoted that the related regulations they are widely dispersed and in most cases. In developed countries, numerous technical and legal problems arise to carry out construction with these materials. In relation to this work, a set of models of raw earth type walls are presented, through the SAP 2000 software, having as a supply of the mechanical properties of this material the Peruvian regulation E.080. For the analysis of these models, a static linear analysis for finite elements and a stress analysis of the service limit state concept were studied. Finally, the models with their respective stress studies, management and design recommendations are presented under the criteria of the analyses carried out, leaving open the possibility of both carrying out an experimental phase to develop the analogy with the postulates and proposed results, as well as such as the option to perform a static pressure analysis by finite elements in order to achieve greater precision and calibration of the model with respect to what can be evidenced in laboratory tests.

Resilience of Raw-Earth Technology in the Climate of Middle Europe Based on Analysis of Experimental Building in Pasłęk in Poland

The article concerns the experimental building in raw-earth technologies situated in Ecological Park in Pasłęk, in the northeast part of Poland with rather severe climate characteristics for middle and east Europe. The purpose of the designing and realization of the building was to demonstrate the methods of construction in traditional raw-earth technologies with current modifications and then to create the possibility for long-term research and observations at the site visits during the buildings’ exploitation. The building was designed as energy efficient with a passive solar system, green roof, and space arrangement. Construction effects of exploitation were checked. Also, physical aspects were analyzed and thermal-humidity environmental parameters were measured with specialized equipment. Examples of such measurements with appropriate conclusion are presented. Based on the analyses, the authors evaluate the resilience of the applied technology under the given climate conditions, as one of the possible sustainability technologies that can be used in Poland under given restrictions.

Raw Earth Construction Perspectives in Italy: An Overview Through the Rehabilitations of Casa Fenu in Villamassargia, Sardinia, and Casa di Teresa in Casalincontrada, Abruzzo

A detailed analysis of the rehabilitation processes of two publicly owned buildings in Sardinia and Abruzzo is taken as a basis for describing the background, difficulties and possible future developments of raw earth as a building material in Italy. Earthen construction techniques, despite a rich tradition and extensive documentation, are still considered outdated, and their use today requires a fortunate confluence of contextual factors. Archival research, literature review and a study of manuals were coupled with an examination of urban plans and public policies, as well as interviews with experts and stakeholders. This multi-approach research shows that there is a strong need to appropriate traditional knowledge so as to translate local skills into viable solutions able to meet today’s needs. The key issue may be investment in training and dissemination. The mindset of the artisan, that of the homo faber (Sennet 2008), needs to be more widely associated with action toward sustainable local development.

Circular building with raw earth: a qualitative assessment of two cases in Belgium

The built environment puts high pressure on our planet, and a great deal is related to resource extraction, material production and waste generation. In the context of circular construction, buildings must be designed and built in order to keep our natural resources in closed material loops for as long as possible. Raw earth has regained attention in the building industry as an abundant, low-impact and highly recyclable building material. However, little is known and experienced about the implementation of raw earth in circular building design. Therefore, this research offers a better understanding of the circularity of earth architecture by assessing two contemporary Belgian cases. Based on literature, semi-structured interviews and the analysis of technical documents, the circularity of the two cases is qualitatively assessed at different scales and levels. It appears that circularity is highest on the material scale and lowest on the building scale for both cases. It is also found that earth as a building material does not easily fit in existing circular assessment frameworks. This investigation represents a contribution towards the development of design support for circular building with raw earth.

CHARACTERIZATION OF LATERITIC SOILS FOR USE IN THE MANUFACTURE OF COMPRESSED EARTH BLOCKS (CEB)

Soil is a widespread natural resource. It comes from the degradation of the mother rock, following the phenomenon of climatic and chemical erosion. Therefore, all soils have very different characteristics depending on their origin [1,2]. Today it is estimated that more than one third of the worlds population lives in earthen housing [3]. In view of the advantages offered by the earth material, several developing countries have adopted the raw earth construction in order to face the housing crisis that is intensifying nowadays. Among the advantages of raw earth, we can highlight the low energy required for its implementation, its aesthetic qualities and good thermal inertia, which allows a cool habitat in summer and retains heat in winter. But the problem with earthen constructions is that they suffer from a lack of resistance, systematic cracking due to shrinkage and problems related to their sensitivity to water [4]. From ancient times to the present day, man has sought to avoid the disadvantages of the earth material, using several means of stabilization to improve its performance and its sensitivity to water, which has given rise to several earth products: adobe, adobe, cob, compressed earth block (CEB) and others. Stabilizing the earth is to give it the properties reversible against physical stresses [5], it is currently confirmed that the stabilization of CEB by binders and bitumen improves their mechanical resistance and insensitivity to water [6]. Thus, scientific studies have been conducted on the stabilization of raw earth by mineral binders (cement and lime) for the most part [7] and by fibers (animal, vegetable and synthetic). However, the use of these mineral binders in high proportions may call into question the ecological character of the material [8]. The knowledge of the physical characteristics of lateritic soils is very important for their better use in the manufacture of compressed and stabilized earth blocks. Some social strata for the manufacture of CEB use lateritic soils without control of their physical characteristics, which leads to consequences such as progressive crumbling of walls, cracks, poor performance of plasters, and discouragement of the use of the said technology. In this study we intend to compile the most reliable experimental data on the physical properties of natural earth and the mechanical properties of CEB. We will take inventory of the performances determined in previous works by several research teams regarding the characterization and stabilization of lateritic soils to be used in the manufacture of CEB. We will give an overview of the state of knowledge concerning the different properties (physical, mechanical and hygrometric properties). Finally, a literature review will also give some orientations for future scientific research.