Stabilization of earthen plasters: Exchange of knowledge and experiences between Italy and Morocco (original) (raw)
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Earthen Plasters Stabilized through Sustainable Additives: An Experimental Campaign
Sustainability
The earthen architecture widely spread in many countries of Europe, America, Asia, Africa, testifies to a particular material and immaterial culture. Nevertheless, it is a fragile heritage, which needs continuous maintenance. To encourage the preservation of such evidence of building techniques, an experimental campaign aimed at the development and evaluation of the performances of protective earthen plasters was undertaken. The durability of the plasters was improved through the addition of different additives, some of them traditional (such as lime and gypsum) and others innovative (geopolymers, enzymes), and resulting from industrial wastes (cement kiln dust). These additives have been selected considering low production costs and a reduced environmental impact, to improve the sustainability of the interventions. The performances of the earthen plasters in terms of efficacy (resistance to water erosion, water absorption, drilling, thermo-hygrometric cycles) and compatibility (cha...
Impact of local additives on properties of earthen plasters
2018
Earth is the oldest building material but it has often been replaced by more weather resistant materials. Recent researches have shown that this material has interesting properties in term of humidity, temperature and pollution control as well as a low environmental impact and compatibility with other natural building materials. Interest is growing in using traditional and/or modern local and natural stabilizers to increase the resistance of the material to water and yet to preserve its interesting properties as natural wall protection. However, properties of earth products differ according to the type of earth and type of stabilizers. As a part of an ongoing research, mechanical and surface properties and water resistance of stabilized earth plasters have been determined to understand the impact of different stabilizers on the durability of the plasters. Impact of sand, wheat chaff, eggwhite, hay juice or molasses have been compared and suitability of additives for the selected earth decided. Chaff, molasses, hay-juice and egg-white have shown interesting properties to increase both strength or water resistance of the material. Addition of sand or chaff has shown a decrease in density and shrinkage, but also in mechanical strength.
Key Engineering Materials, 2016
Clayish earth-based mortars can be considered eco-efficient products for indoor plastering since they can contribute to improve important aspects of building performance and sustainability. Apart from being products with low embodied energy when compared to other types of mortars used for interior plastering, mainly due to the use raw clay as natural binder, earth-based plasters may give a significant contribution for health and comfort of inhabitants. Due to high hygroscopicity of clay minerals, earth-based mortars present a high adsorption and desorption capacity, particularly when compared to other type of mortars for interior plastering. This capacity allows earth-based plasters to act as a moisture buffer, balancing the relative humidity of the indoor environment and, simultaneously, acting as a passive removal material, improving air quality. Therefore, earth-based plasters may also passively promote the energy efficiency of buildings, since they may contribute to decreasing t...
Construction and Building Materials
Abstract It is important to ensure indoor comfort by passive methods, avoiding mechanical equipment that has energy costs. To assess plasters common efficiency but also its contribution as moisture buffers, five different plastering mortars, including unstabilized and stabilized earth-based plasters, gypsum and cement-based pre-mixed plasters, were analyzed and their chemical, mechanical and hygroscopic characteristics compared. The materials and mortars were analyzed by X-ray diffraction and simultaneous thermal analysis. Linear shrinkage, dry bulk density, dynamic modulus of elasticity, flexural and compressive strengths, dry abrasion resistance, surface cohesion, surface hardness and sorption and desorption of mortars and plasters were also evaluated. The mechanical strength of earthen mortars is lower than gypsum and cement-based mortars. However, earth plasters show the highest hygroscopicity, acting as moisture passive buffers, improving thermal comfort and contributing to occupantś health.
Eco-efficient earth plasters: influence of clay content, sand particle size and support
Journal of World Architecture
Earth construction, including the use of earth mortars, has been extensively used in the past. However, with the appearance of hydraulic binders, the use of earth strongly decreased for new construction and even to repair old earth buildings, whose best solution would be the use of compatible materials such as earth mortars.Due to the innumerable advantages of earth and with the growing concern on eco-efficient construction, the interest on earth construction has resurfaced, namely on earth mortars.In order to optimize the composition of an earth plastering mortar made with a defined clayish earth and two siliceous sands with different particle size, six compositions were assessed. Mortars with different volumetric ratios were applied in two different supports (on the back of a tile and on a brick) and planar specimens were also produced. Distinct characteristics were assessed, such as their visual appearance, shrinkage, surface cohesion, surface hardness, dry abrasion resistance, u...
Historical plasterwork techniques inspire new formulations
Construction and Building Materials, 2013
Lime putty, gypsum, rabbit skin glue, sand, limestone fines and marble dust were used. 100% Substitution of sand by limestone fines of an ''Escaiola'' is studied for the first time. Marble cut waste in mortar increases the strength and durability.
Evaluation of different raw earthen plasters stabilized with lime for bio-building exploitation
2019
The building sector generates around 5-8% of greenhouse gas emissions (GHG)[1] and the disposal of C&D waste at the end-of-life is a high environmental cost. The raw earth is a sustainable construction material with low embedded energy, available locally. It is the most ancient technique of construction, studied in recent years to reduce the environmental life cycle impact of buildings. Clay is responsible for the earth plastic behaviour and represents the binder that keeps together silt and sand grains. Earth sets through drying without chemical reactions, so it could be reinserted into the nature. At the same time, earthen constructions do not withstand weathering and develop lower mechanical performances compared with those which exploit hydraulic binders. We investigated the possibility of improving these characteristics by stabilizing earthen products with the addition of small amounts of lime preserving clay as eco-friendly binder and the full end-of-life recyclability. Four e...
Eco-efficient earthen plasters: The influence of the addition of natural fibers
2015
Clayish earth-based mortars are been recognized, all over the world, as eco-efficient products for plastering. Apart from being a product with low embodied energy when compared to other types of plasters, their application on the interior surface of walls may give a strong contribution for the health and comfort of inhabitants. As part of an ongoing research regarding earth-based plasters this work assesses the influence of the addition of two types of natural fibresoat straw and typha fiber-wollon the characteristics of plastering mortars made with a clayish earth. Mechanical and physical characteristics were tested, showing that addition of these fibers contribute to decrease linear drying shrinkage and thermal conductivity, as well as promoting the adhesion strength of plaster to the substrate. The improvement of mechanical resistance reveal to be dependent on the type of fiber added while the hygroscopic capacity of the plaster is maintained regardless of the fiber additions.
Earth-based mortars for masonry plastering
Earth mortars have been applied since unknown times. Their advantages are ecological but also cover several technical aspects, in terms of compatibility with masonries, reversibility, comfort, aesthetic and health. Some requirements of a recent German standard, which focus on non-stabilized earth plastering mortars, are presented. A commercial premixed Portuguese earth mortar was made within an ECVET workshop and applied as plasters on four different experimental masonry walls, at exterior environmental conditions. The plasters were observed during six months and characterized in situ by non destructive techniques, namely by ultra-sounds and for surface hardness. The same mortar used for the plasters was characterized in laboratory in fresh state and samples of mortar (only mortar and mortar layer applied on brick) were produced and characterized after drying. The characterization of the earth plasters applied on the walls and of the mortar samples is presented and discussed, showing the viability of their use as plaster for different masonry walls.
Durability Properties of Innovative Plasters for Renovation of Historical Buildings
2008
The current practice of the solution of the problem of historical buildings surface layers damage is based more or less on the method of analogy. At a reconstruction, usually such material and method of its application is used which is according to the meaning of supervisory authorities compatible with the original treatments and which already was found to be suitable at an application on some other building before. The durability of new surface layers is mostly estimated on the basis of experience because too few parameters are known for a reliable durability estimate. The choice of a material for reconstruction is then often less suitable regarding to the moisture and salt content in the masonry which leads to low durability and short service life of surface layers. In this paper, main durability properties of innovative lime plasters with metakaolin admixture, namely water sorptivity, moisture diffusivity, water vapor diffusion coefficient, thermal conductivity and specific heat ...