Paulina Faria

Unstabilized Rammed Earth: Characterization of Material Collected from Old Constructions in South Portugal and Comparison to Normative Requirements

Unstabilized rammed earth is a recyclable, economical, and eco-friendly building material, used in the past and still applied today. Traditionally, its use was based on a long empirical knowledge of the local materials. Because this knowledge was mostly lost or is no longer sufficient, in many countries normative documents have been produced to allow the assessment of rammed earth soils. With the aim of contributing for a refining of these normative requirements, this article presents a research work that included: (i) collection of Unstabilized rammed earth samples from six constructions in Portugal; (ii) a literature survey of normative and complementary documents to identify the most mentioned key-properties, the test procedures and the corresponding threshold limits; and (iii) a discussion of the test procedures and of the thresholds limits in the light of the experimental results. The analyzed properties are the particle size distribution, maximum particle size, plasticity, compaction, linear shrinkage, organic content, and salt content. The work highlights the advantages of taking into account the characteristics of existing constructions as a basis for the establishment and further refining of consistent threshold values. In particular, it shows that it is essential to adjust the requirements to the specificities of local materials.

Experimental Characterization of an Earth Eco-Efficient Plastering Mortar

AbstractEarthen plastering mortars are becoming recognized as highly eco-efficient. The assessment of their technical properties needs to be standardized, but only a German standard exists for the moment. An extended experimental campaign was developed in order to assess multiple properties of a ready-mixed earth plastering mortar and also to increase scientific knowledge of the influence of test procedures on those properties. The experimental campaign showed that some aspects related to the equipment, type of samples, and sample preparation can be very important; although others seemed to have less influence on the results and the classification of mortars. It also showed that some complementary tests can easily be performed and considered together with the standardized ones, whereas others may need to be improved. The plaster satisfied the requirements of the existing German standard but, most importantly, it seemed adequate for application as rehabilitation plaster on historic and modern masonry build...

Eco-efficient earthen plasters: the influence of the addition of natural fibers

Clayish earth-based mortars are being 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 fibers—oat straw and typha fiber-wool—on 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.

Hydric Behavior of Earth Materials and the Effects of Their Stabilization with Cement or Lime: Study on Repair Mortars for Historical Rammed Earth Structures

AbstractEarthen building materials bear interesting environmental advantages and are the most appropriate to conserve historical earth constructions. To improve mechanical properties, these materials are often stabilized with cement or lime, but the impact of the stabilizers on the water transport properties, which are also critical, has been very rarely evaluated. The researchers have tested four earth-based repair mortars applied on three distinct and representative rammed earth surfaces. Three mortars are based on earth collected from rammed earth buildings in south of Portugal and the fourth mortar is based on a commercial clayish earth. The main objective of the work was over the commercial earth mortar, applied stabilized and not stabilized on the three rammed earth surfaces to repair, to assess the influence of the stabilizers. The other three earth mortars (not stabilized) were applied on each type of rammed earth, representing the repair only made with local materials. The four unstabilized earth...

Consolidation and chromatic reintegration of historical renders with lime-based pozzolanic products

Abstract Historical renders are exposed to several degradation processes that can lead to a wide range of anomalies, such as scaling, detachments, and pulverization. Among the common anomalies, the loss of cohesion and of adhesion are usually identified as the most difficult to repair; these anomalies still need to be deeply studied to design compatible, durable, and sustainable conservation treatments. The restitution of render cohesion can be achieved using consolidating products. Nevertheless, repair treatments could induce aesthetic alterations, and, therefore, are usually followed by chromatic reintegration. This work aims to study the effectiveness of mineral products as consolidants for lime-based mortars and simultaneously as chromatic treatments for pigmented renders. The studied consolidating products are prepared by mixing air lime, metakaolin, water, and mineral pigments. The idea of these consolidating and coloring products rises from a traditional lime-based technique, the limewash, widely diffused in southern Europe and in the Mediterranean area. Consolidating products were applied and tested on lime-based mortar specimens with a low binder–aggregate ratio and therefore with reduced cohesion. A physico-mechanical, microstructural, and mineralogical characterization was performed on untreated and treated specimens, in order to evaluate the efficacy and durability of the treatments. Accelerated aging tests were also performed to assess consolidant durability, when subjected to aggressive conditions. Results showed that the consolidants tested are compatible, effective, and possess good durability.

Evaporation from porous building materials and its cooling potential

AbstractEvaporative cooling is a traditional strategy to improve summer comfort, which has gained renewed relevance in the context of the transition to a greener economy. Here, the potential for evaporative cooling of common porous building materials, like natural stone and ceramic brick, is evaluated. The work has relevance also to the protection of built heritage because evaporation underlies the problems of dampness and salt crystallization, which are so harmful and frequent in this heritage. It was observed that the drying rate of the materials is, in some cases, higher than the evaporation rate of a free water surface. Surface area measurements by a three-dimensional optical technique suggested, as probable cause of this behavior, that surface irregularity gives rise to a large effective surface of evaporation in the material. Surface temperature measurements by infrared were performed afterward during evaporation experiments outside during a hot summer day in Lisbon. Their results indicate that ordi...

Earthen plasters based on illitic soils from Barrocal region of Algarve: contributions for building performance and sustainability

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 the needs of mechanical ventilation and air conditioning. This study is part of an ongoing research regarding earth-based plasters and focuses on mortars specifically formulated with soils extracted from Portuguese ‘Barrocal’ region, in Algarve sedimentary basin. This region presents high potential for interior plastering due to regional geomorphology, that promote the occurrence of illitic soils characterized by a high adsorption capacity and low expansibility. More specifically, this study aims to assess how clayish earth and sand ratio of mortars formulation can influence the physical and mechanical properties of plasters. For this assessment four mortars were formulated with different volumetric proportions of clayish earth and siliceous sand. The results from the physical and mechanical characterization confirmed the significantly low linear shrinkage of all the four mortars, as well as their extraordinary adsorption-desorption capacity. These results presented a positive correlation with mortars ́ clayish earth content and are consistent with the mineralogical analysis, that confirmed illite as the prevalent clay mineral in the clayish earth used for this study. Regarding mechanical resistance, although the promising results of the adhesion test, the flexural and compressive strength results suggest that the mechanical resistance of these mortars should be slightly improved. Considering the present results the mortars mechanical resistance improvement may be achieved through the formulation of mortars with higher clayish earth content, or alternatively, through the addition of natural fibers to mortars formulation, very common in this type of mortars. Both those options will be investigated in future research.

The compatibility of earth-based repair mortars with rammed earth substrates

Earth constructions are susceptible to degradation due to natural or human causes. The degradation of the exterior surface of earth walls is very common, either due to lack of maintenance or to the use of incompatible materials, and often requires the application of a repair mortar. This work analyses experimentally the performance of earth-based repair mortars applied on rammed earth surfaces. The mortars are based on earth collected from rammed earth buildings in south Portugal or on a commercial earth. Eight repair mortars were formulated, with the unstabilized soils or including also small binder content. Four types of binder were tested: hydrated air-lime, natural hydraulic lime, Portland cement and natural cement. The repair mortars were applied on two types of standard defects purposely made on rammed earth blocks, representing the most currently defects found on exterior rammed earth surfaces: standard superficial defect and standard deep defect. The performance of the mortars, their compatibility with the substrates and the visual effectiveness of the intervention were evaluated. It was concluded that the mortars behaved differently when applied on different rammed earth supports. However, the best performances occurred always for the mortars made from unstabilized soil identical to that of the rammed earth substrate. Indeed, the use of stabilizers systematically worsened the behavior of the repair mortars, regardless of the type of binder used for that purpose.

Viability of ceramic residues in lime-based mortars

When we approach the subject of construction and rehabilitation of buildings we necessarily must think about external wall coatings as they are the elements more exposed to climate actions, mechanical and environmental conditions and, consequently, the first to be deteriorated and to need rehabilitation. Concerning to the replacement of old plasters and renders, air lime mortars are normally the ones that are more compatible with the existing elements, presenting, however, some limitations due to its slow setting time. As an alternative we may use natural hydraulic lime mortars. We know that brick dust and grains have been widely used in mortars in the past, improving its characteristics, and that actually there are many kinds of ceramic residues that are byproducts of industry and are normally carried into landfills. Within this context and associating the improvement of mortars characteristics to the necessity of sustainable construction practices, some mortars, formulated based on air lime or natural hydraulic lime, with the addition of ceramic residues, have been recently studied. The aim of this paper is to present the experimental work that has been developed concerning the behaviour of two types of these lime mortars with ceramic residues. Characteristics, particularly in terms of flexural and compressive resistances, capillary water absorption and water vapour permeability will be discussed. Comparison will be made between the characteristics of the mortars made with the two limes, and of mortars made with those limes with partial substitutions of siliceous sand by different types of ceramic residues. It will be possible to draw same conclusions about the interest and viability of recycling the ceramic residues as aggregates, its contribution as pozzolan and filler, and also if natural hydraulic lime-based mortars can be a good alternative to air lime-based mortar for ancient masonry.

Natural hydraulic lime mortars: influence of the aggregates

Natural hydraulic lime specifications changed with the 2010 version of standard EN 459-1 and new natural hydraulic limes appeared in the market. The characteristics of mortars depend on many different parameters such as the type of binder, the type of aggregates, the use of fillers and of super plasticizers applied in the mortars formulations; also on mixing and curing conditions. In this paper mortars with a Portuguese NHL3.5 were formulated with binder:aggregate volumetric proportions1:3, varying the aggregates type and proportions between them. Two coarse sands, a medium sand, a river sand, a finer sand, a calcareous filler and a ceramic powder were used, being the two last mentioned aggregates by-products from industry. Standardized prismatic mortar samples and samples of mortar applied on a brick surface were prepared and conditioned in two different situations: following standard EN 1015-11 and at 65% relative humidity but with daily water spray during the first days. Mortars were characterized in the fresh state and at the age of 28 days. Results showed the influence namely of the curing, particularly in terms of water capillary, and of the fillers. They also showed that NHL3.5 mortars seem to be adequate for old masonries conservation and repair and, in some situations, they can be an alternative to air lime based mortars.