Earthen Plasters Stabilized through Sustainable Additives: An Experimental Campaign (original) (raw)
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Stabilization of earthen plasters: Exchange of knowledge and experiences between Italy and Morocco
2016
The preservation of earthen architectural heritage and earthen contemporary architecture asks for the experimentation and the development of proper materials and intervention techniques in order to prevent decays which may compromise the conservation of earthen heritage over time. This research program, thanks to a bilateral cooperation between the CNRST-UCA and CNR-ICVBC, aims to design and test earth-based plasters stabilized with traditional products (gypsum or lime), in order to acquire information necessary to develop more durable earthen mixtures to be applied both on existing and new buildings. The experimental campaign intends to assess the capacity of these stabilized plasters to guarantee an appropriate protection of earthen walls. The plasters have been tested at first in laboratory, then they have been applied on an earthen building in the outskirts of Marrakesh. The performances of the on site plasters are still under study and will not be presented in this paper.
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Earth is the oldest building material but it has often been replaced by more weather resistant materials.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.
An experimental campaign was developed to evaluate the properties of earth plastering mortars, not only at the level of workability and physic-mechanical performance but also their susceptibility for biological colonization. A ready-mixed earth mortar and several other mortars formulated with a raw clayish earth were produced. The influence of partial replacement of fine sand by a phase change material (PCM) and the addition of low amounts of oat fibres and hydrated air lime were assessed. The experimental campaign shows that the PCM completely changes the mortar workability, with a decrease on wet density. The addition of PCM and fibres decreases the bulk density and, consequently, increases the porosity of the mortars. The presence of PCM, fibres and air lime decreases the thermal conductivity. Earth mortars are susceptible to mould development, and the fibres or PCM seem to intensify their bio-susceptibility. A low addition of air lime increases pH and inhibits fungal growth though decreasing the mechanical properties. Mortars with PCM, fibres and air lime present a higher surface roughness in comparison to other mortars, including the ready-mixed earth mortar with fibres. Surface roughness was found to be an important factor influencing the level of colonization.
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.
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 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...
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...
Environmental impacts of natural and conventional building materials: a case study on earth plasters
Journal of Cleaner Production, 2014
This study compares the environmental impacts of earthen plasters (based on clay) with those of conventional industrial plasters (based on cement or hydraulic lime) from a life cycle perspective. Environmental impacts were assessed via midpoint (Cumulative Energy Demand, Greenhouse Gas Protocol and Ecological Footprint) and endpoint (ReCiPe) indicators. Results show that the environmental performances of earthen materials, whose production is based on simple processes requiring relatively small amounts of energy, are substantially better than those of conventional plasters. The largest impact component is, for all plasters, the energy produced from fossil sources, which accounts for 63e85% of the overall embodied energy. However, the larger impacts of synthetic plasters stem mainly from CO 2 emissions during the calcination process in cement manufacturing. On the other hand, transport is very important, at least in relative terms, in determining the overall impact of earth plasters. This highlights the importance of finding local sources of raw materials to avoid nullifying the environmental benefits of natural building products.
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-efficiency of plasters for rehabilitation and new buildings
2nd International Conference on Sustainable, Environmentally Friendly Construction Materials, 2021
A review of the current state of art for air-lime, gypsum and earth based plasters for rehabilitation and new buildings, in terms of eco-efficiency, is presented. These mortars belong to Portuguese traditional architecture, responding to compatibility criteria most of the time. This factor, combined with a possible positive response to eco-efficiency evaluation, would bring interest for their application in rehabilitation as well as in new construction. To assess eco-efficiency of plasters, the considered factors are linked to the environmental impact of these products and to their contribution for occupants well-being. Some qualitative results concerning embodied energy for these mortars in a "cradle to gate" approach analysis are shown. The lack of a common, standardized and shared procedure for this evaluation seems an evidence, above all when the attempt of comparing results from different studies is made. Furthermore, common and specific characteristics mostly related to contribution for indoor comfort conditions are presented, as indicators of technical efficiency of those plasters. The potential for behaving as moisture regulators and passive removal materials not only affect users, but can also have an important role in energy savings. Lastly, durability is considered a key factor of eco-efficiency mainly to meet the purpose of minimising exploitation of raw materials. For this reason it is important to consider protective treatments or finishing system, for improving durability, always keeping in mind all the elements of the equation.