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Earth-based mortars have been used all over the world since ancient times in an extensive range of building types from vernacular architecture to monuments. Plastering is one of the most common contemporary applications of earth-based mortars used for earthen-building conservation or modern architecture. Raw earth is a very diverse natural material, and clay minerals play a key role in plaster properties being responsible for their setting process and providing the capacity of balancing the indoor hygrometric conditions of buildings. This capacity offers significant benefits to energy savings delivering comfort and health of inhabitants and also contributes to building conservation. For this study, three mortars were produced with different clayish earths to assess the influence of clay mineralogy. Mortars characterization confirmed that clay mineralogy drives important plaster properties, such as vapour adsorption and drying shrinkage, while also having a significant influence on mechanical strength, dry abrasion, and thermal conductivity. Within the studied mortars, illitic clayish earth stands outs as more adequate for earth-based plasters, showing balanced properties, namely linear drying shrinkage, mechanical strength, dry abrasion, and water vapour adsorption. authorsversion inpress

PTDC/EPH-PAT/4684/2014. SAICT/23349/2016. Sem PDF conforme despacho. Earth mortars are known for being ecological but also reversible, contributing to comfort and aesthetic. Nevertheless, compatibility with different masonries is scarcely assessed. A commercial unstabilised ready-mixed earth mortar was produced with an ilitic earth with addition of sand and oat straw fibres. It was used to plaster different experimental masonry walls, at protected outdoors environmental conditions. The plasters applied on the masonries were visually monitored and characterized in situ by non-destructive techniques and in laboratory by bulk density and microstructure. The same mortar used for the plasters was characterized in laboratory in fresh state and, after drying, on prismatic specimens and specimens composed by a mortar layer applied on hollow bricks. Some variation of results occurs when the same unstabilised ready-mixed earth mortar is used to plaster different masonries, what may be related to the water absorption of the masonry materials. However, after six months the earth plaster presented durability on the different masonries when protected from rain. It proves that this ecological mortar is technically efficient to plaster different types of masonry, historical or contemporary. published

Plasters can be formulated with different binders, presenting different characteristics. Their main function is the protection of the substrate but, as indoor coatings, their influence on aesthetic performance and indoor air quality and comfort is also important. A plaster formulated with a clayish earth is compared to plasters formulated with common binders, namely hemihydrate gypsum, air lime and natural hydraulic lime. All the plasters have the same volumetric proportion binder:sand and were produced with the same siliceous washed sand. Results show that: the linear shrinkage of the earth mortar was the highest while the gypsum mortar presented no shrinkage; the bulk density of all the mortars were similar but there were differences on thermal conductivity, with advantages for the lime mortars, although this property is not significant for plasters application thicknesses; the gypsum mortar presented the highest mechanical properties while the lime mortars presented the lowest, even lower in comparison to the earth mortar; however, the resistance to dry abrasion was lower for the earth plaster; the earth plaster registers a very high hygroscopicity in comparison to all the other plasters, being an important contribution to indoor comfort, occupants health and energy consumption reduction. publishersversion published

PTDC/EPHPAT/4684/2014 SAICT/23349/2016 COMPETE 2020 [RESUMO] Em conservação, os rebocos de terra podem ser utilizados como camadas de sacrifício. No entanto, a terra é vulnerável quando em contacto com a água. A aplicação de tratamentos superficiais ecológicos em rebocos de terra pode aumentar a sua durabilidade, ecoeficiência e gama de aplicações. Neste artigo avaliou-se o comportamento de um reboco de argamassa pré-doseada de terra aplicado in situ sobre muretes experimentais de alvenarias de adobe e de blocos de betão (em exposição exterior com proteção), e em condições controladas de laboratório, sobre tijolo furado, após um período de quatro anos de envelhecimento. Foram aplicados diversos tratamentos superficiais sobre os rebocos: óleo de linhaça, mucilagem de aloé vera e água da cozedura de massa e de arroz. Os rebocos foram caracterizados de forma não destrutiva. O tratamento superficial com óleo de linhaça apresenta bons resultados e melhora a durabilidade do reboco, conferindo-lhe adequada protecção contra a degradação natural. [ABSTRACT] In conservation, earth renders can be used as sacrificial coatings. However, earth presents vulnerability when in contact with water. The application of ecological surface treatments on earth renders can be of great relevance, ensuring their durability while increasing eco-efficiency and extending its range of applications. The behaviour of a ready-mixed earth render applied in situ, on adobe and concrete block masonry experimental walls exposed outdoors with protection, and under controlled laboratory conditions, on hollow bricks, was evaluated after four years. Several superficial treatments were applied on the renders: linseed oil, mucilage of aloe vera and pasta and rice cooking water. The renders were characterized by non-destructive tests. The surface treatment with linseed oil presents good results and improves the durability of the earth render, giving it adequate protection against natural degradation. publishersversion published

Earth-based mortars have been used all over the world since ancient times, in an extensive range of building types, from vernacular architecture to monuments. Plastering is one of the most common current applications of earth-based mortars, as for earthen-building conservation or contemporary architecture. Raw earth is a very diverse natural raw material, and clay minerals play a key role on plaster properties, being responsible for its setting process and the capability of balancing the indoor hygrometric conditions of buildings, which have strong benefits on energy saving for comfort and health of inhabitants and building conservation. For this study three mortars were produced with different clayish earths to assess the influence of clay mineralogy. Mortars characterizations confirmed that clay mineralogy drives important plaster properties, like vapour adsorption, drying shrinkage, and also have significant influence on mechanical resistance, dry abrasion and thermal conductivity. Within the studied mortars illitic clayish earth stands outs as more adequate for earth-base plasters, with balanced linear drying shrinkage, mechanical resistance, dry abrasion and vapour adsorption. authorsversion published

Resumo Admite-se como hipótese que as argamassas mistas de cal e terra tenham resultado da prática profissional quando as condições económicas possibilitaram a adição de cais às argamassas vernáculas só de terra, que são susceptíveis à ação da água. Em estudos anteriores verificou-se que a adição de baixos teores de cal aérea a argamassas de terra de cor escura, embora tornem as argamassas resistentes à água, conduzem a alterações da sua cor para tom mais claro e redução de resistências mecânicas. Neste estudo avalia-se o efeito que substituições de cal aérea por uma terra local caulinítica apresentam em argamassas de cal ao traço volumétrico 1:2, correspondendo a argamassas com traço em massa de 1:8, com substituições de 10% a 50%. As argamassas têm, pela sua formulação, menor energia incorporada e demonstram ser adequadas para aplicação em rebocos de edifícios antigos e mesmo em construção nova com características compatíveis. Os resultados da caracterização mecânica, física e por ataque de sulfatos foram positivos para uma substituição de 10%, variando percentualmente entre propriedades, mas muito há ainda a investigar para um conhecimento aprofundado deste tipo de argamassas mistas de cal e terra, muito utilizadas no passado, com vista à otimização de formulações que possam vir a ser aplicadas correntemente. Abstract Earth-lime mortars probably result from professional practices from the time when economical conditions enabled the addition of air lime to vernacular earth mortars, which are not durable when in contact with water. Previous studies have shown that the addition of low contents of air lime on earth mortars with dark colour, while turning the mortars water resistant, makes their colour lighter and weakens their mechanical characteristics. This study examines the partial weight replacement of lime by a local earth in air lime mortars with a 1:2 lime: sand volumetric proportion, corresponding to mortars with a 1:8 weight proportion, with replacements from 10 to 50%. The embodied energy of mortars is reduced by their formulation, and they are adequate for use as render in old buildings and also on new constructions with compatible characteristics. The results of the mechanical and physical characteristics, as well as on the reaction to sulphates attack, were particularly positive for a 10% lime replacement by earth, with variations between the assessed properties. Nevertheless, further research is still needed for a deeper knowledge of the characteristics of lime-earth mortars, widely used in the past, in order to optimise formulations to be applied in the present day.

9th International Masonry Conference 2014, 7-9 July, Universidade do Minho, Guimarães 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.

As it is now recognized worldwide, the use of earth mortars for plastering and rendering is very important due to eco-efficiency. Rendering mortars have to present durability to rain water. A ready-mixed earth mortar based on natural clayish earth, siliceous sand and cut oat fibers was analyzed. In addition to this, three other mortars with volumetric proportion 1:3 (clayish earth: aggregate) were formulated in laboratory. A coarse and a fine sand were used as aggregate. Oat fibers were added to one of these mortars while oat fibers plus air lime were added to another. Microstructure, mechanical strength, capillary absorption, drying and mineralogical composition were evaluated. It was concluded that the addition of a small amount of air lime causes a decrease of mechanical strength and an increase on capillary absorption. For that reason it does not seem the best technique to increase durability for rendering mortars. publishersversion published