Jean-Claude Morel

Building houses with local materials: means to drastically reduce the environmental impact of construction

This paper describes the process of materials selection, design and construction used for a series of small residential buildings in Southern France. Whenever possible, materials were resourced in situ in order to minimise the environmental impact of the new buildings. In particular, the process of materials selection, stone masonry with stabilised in situ soil mortar, and the form of construction are outlined. Guidance for a more generalised adoption of the design process is also provided. The energy consumed in the building of one house is compared to a typical concrete house. By adopting local materials the amount of energy used in building decreased by up to 215% and the impact of transportation by 453%. However, adoption of local materials in developed countries can be hindered by the loss of traditional building crafts and a lack of appropriate building standards. These problems are also discussed in this paper.

A model to measure compressive strength of compressed earth blocks with the '3 points bending test'

Abstract This article proposes a modelling of the ‘3 points bending test’ on compressed earth blocks (CEB) which will give their compressive strength. This test is already used in situ for CEB quality control. Conventional bending modelling gives the tensile stress at failure using three of the principal assumptions of the Strength of Materials theory, which are in fact not respected here. This is why it is proposed in this paper to model the arch behaviour in compression, which is of primary importance for aspect ratios less than three. Considering a proposed lattice, a behaviour at failure is obtained, close to that of a CEB during a 3 points bending test. The compressive stress at failure is obtained by using this lattice. The validation of the model is given using experimental data. Then the model gives information on the CEB structure such as isotropy, dry density gradient within the CEB, and effect of friction with the experimental direct compression test device, leading to confinement of the sample.

Comparaison de méthodes d’essais de mesures des caractéristiques mécaniques des mortiers de terre

RésuméIl existe encore très peu d’études sur les mortiers de terre, mais déjà proce’edures d’essais sont différentes selon les auteurs. Cependant toutes les procédures utilisées pour les mortiers classiques sable: chaux: ciment ne sont pas applicables sans un minimum de précautions du fait de l’activité de l’argile et de la faible raideur des mortiers de terre. L’article présente certaines procédures d’essais, leur comparaison pour le cas de la résistance à la compression montre des écarts importants. Pour les mesures de maniabilité et de résistance à la traction, les premiers résultats obtenus peuvent servir de base à une discussion sur le choix des procédures d’essais. On donnera ensuite les premiers éléments permettant de corréler les mesures faites sur mortier avec le comportement des maçonneries.AbstractThere are few studies on soil mortars, yet different procedures are utilized. All the testing procedure for classical sand-lime-cement mortars cannot be used without appropriate checking because of the activity of clay and because article presents some laboratory procedures used on soilcement mortars; their comparison in the case of the compression strength measurement shows some major differences in the results. For the measurement of workability and tensile strength, the first results can give a base for the choice of a procedure.Finally some elements will be given to correlate the soil mortar characteristics with the masonry behaviour.

How Properties of Kenaf Fibers from Burkina Faso Contribute to the Reinforcement of Earth Blocks

Physicochemical characteristics of Hibiscus cannabinus (kenaf) fibers from Burkina Faso were studied using X-ray diffraction (XRD), infrared spectroscopy, thermal gravimetric analysis (TGA), chemical analysis and video microscopy. Kenaf fibers (3 cm long) were used to reinforce earth blocks, and the mechanical properties of reinforced blocks, with fiber contents ranging from 0.2 to 0.8 wt%, were investigated. The fibers were mainly composed of cellulose type I (70.4 wt%), hemicelluloses (18.9 wt%) and lignin (3 wt%) and were characterized by high tensile strength (1 ± 0.25 GPa) and Young’s modulus (136 ± 25 GPa), linked to their high cellulose content. The incorporation of short fibers of kenaf reduced the propagation of cracks in the blocks, through the good adherence of fibers to the clay matrix, and therefore improved their mechanical properties. Fiber incorporation was particularly beneficial for the bending strength of earth blocks because it reinforces these blocks after the failure of soil matrix observed for unreinforced blocks. Blocks reinforced with such fibers had a ductile tensile behavior that made them better building materials for masonry structures than unreinforced blocks.

Annoyance from industrial noise: Indicators for a wide variety of industrial sources

In the study of noises generated by industrial sources, one issue is the variety of industrial noise sources and consequently the complexity of noises generated. Therefore, characterizing the environmental impact of an industrial plant requires better understanding of the noise annoyance caused by industrial noise sources. To deal with the variety of industrial sources, the proposed approach is set up by type of spectral features and based on a perceptive typology of steady and permanent industrial noises comprising six categories. For each perceptive category, listening tests based on acoustical factors are performed on noise annoyance. Various indicators are necessary to predict noise annoyance due to various industrial noise sources. Depending on the spectral features of the industrial noise sources, noise annoyance indicators are thus assessed. In case of industrial noise sources without main spectral features such as broadband noise, noise annoyance is predicted by the A-weighted sound pressure level L(Aeq) or the loudness level L(N). For industrial noises with spectral components such as low-frequency noises with a main component at 100 Hz or noises with spectral components in middle frequencies, indicators are proposed here that allow good prediction of noise annoyance by taking into account spectral features.

A Procedure to Measure the in-Situ Hygrothermal Behavior of Earth Walls

Rammed earth is a sustainable material with low embodied energy. However, its development as a building material requires a better evaluation of its moisture-thermal buffering abilities and its mechanical behavior. Both of these properties are known to strongly depend on the amount of water contained in wall pores and its evolution. Thus the aim of this paper is to present a procedure to measure this key parameter in rammed earth or cob walls by using two types of probes operating on the Time Domain Reflectometry (TDR) principle. A calibration procedure for the probes requiring solely four parameters is described. This calibration procedure is then used to monitor the hygrothermal behavior of a rammed earth wall (1.5 m × 1 m × 0.5 m), instrumented by six probes during its manufacture, and submitted to insulated, natural convection and forced convection conditions. These measurements underline the robustness of the calibration procedure over a large range of water content, even if the wall is submitted to quite important temperature variations. They also emphasize the importance of gravity on water content heterogeneity when the saturation is high, as well as the role of liquid-to-vapor phase change on the thermal behavior.

First exploratory study on the ageing of rammed earth material

Rammed earth (RE) is attracting renewed interest throughout the world thanks to its “green” characteristics in the context of sustainable building. In this study, the ageing effects on RE material are studied on the walls which have been constructed and exposed for 22 years to natural weathering. First, mechanical characteristics of the “old” walls were determined by two approaches: in-situ dynamic measurements on the walls; laboratory tests on specimens which had been cut from the walls. Then, the walls’ soil was recycled and reused for manufacturing of new specimens which represented the initial state. Comparison between the compressive strength, the Young modulus of the walls after 22 years on site and that of the initial state enables to assess the ageing of the studied walls.

Historical Rammed Earth Process Description Thanks to Micromorphological Analysis

ABSTRACT Rammed earth was traditionally used in western European countries before industrial building materials replace it during 20th century. Construction strategies developed by former builders were dictated by locally available construction materials and engendered local constructive cultures. Unfortunately, this knowledge was orally transmitted and is lost today. The rediscovery of these cultures can provide answers to modern rammed earth construction processes. Micromorphological analysis of earth walls provides information to rediscover traditional rammed earth process. This methodology is applied for the first time, on a rammed earth wall of a farm located in Bresse (France). Thanks to this methodology, pedological horizon, extraction depth, and location of the material source are identified. The surface area excavated for the construction of the building is estimated. Micromorphological study gives information on mixing degree and water content at implementation time. Strain features associated with ramming effect and rammed earth boundary layer are also highlighted.

Weathering and durability of earthen material and structures

: Durability of earthen structures is mainly dependent on the action of water on the walls. In this chapter, the relevance of the current tests measuring the resistance of earthen material to water is analysed and some pertinent tests are suggested to corresponding domains of application. The second part of the chapter deals with the use of plaster to increase durability. The validation of the plaster is proposed thanks to two in situ tests: the shrinkage test and the shear test for surface coatings. The long-term performance of earthen material is then analysed through research that has been conducted on walls exposed to natural climatic conditions for several years.

Yield Design Modelling Of Dry-stoneRetaining Walls

Over the past few years, there has been a steady increase in the interest in dry-stone walling not only to preserve existing constructions but also to build new ones. Yet, no structural design method has been validated till today. In this study, a simplified model dedicated to dry-stone is propounded. This simulation, implemented in the rigorous framework of yield design homogenization, can meet engineering expectations. First, the model is introduced, and the parameter measurement detailed. Then, the validity of the method is assessed by comparisons with micro and macro-mechanical methods, and field trials. As a conclusion, possible improvements of the model are discussed.