Characterization of earthen plasters – Influence of formulation and experimental methods

All over the world there is a vast heritage of earth construction where earth plasters were applied. Nowadays, due to environmental but also technical reasons, new earth plasters are also applied on common new masonries. That is why its characterization, in the laboratory but also in situ, is very important. In the present study, a pre-mixed earth plastering mortar (as control) and nine earth-based plastering mortars formulated in laboratory with different compositions were characterized. These mortars were formulated with 1:3 (illitic clayish earth:aggregate) volumetric ratio. The aggregate comprises a variation of fine and coarse sand and the partial replacement of the fine sand by a phase change material (PCM). The influence of the addition of a low amount of oat fibers is also evaluated. The mortars were characterized by different methods in laboratory and on an experimental wall exposed outdoors by destructive and nondestructive methods: dry bulk density, dynamic modulus of elasticity, flexural and compressive strengths, adhesive and shear strengths, dry abrasion resistance, surface cohesion, ultrasonic pulse velocity and hardness. Results were discussed and some were correlated. Most mortars present good mechanical strengths. However, the addition of PCM significantly decrease the mechanical strength of mortars. In terms of mechanical properties, the addition of oat fibers only promotes an improvement on adhesive strength. The simple surface hardness by durometer present laboratory and in situ results well correlated for earth mortars without PCM.publishersversionpublishe

Natural hydraulic lime mortars: influence of the aggregates

3rd Historic Mortars Conference, 11-14 September 2013, Glasgow, ScotlandNatural hydraulic lime specifications changed with the new version of standard EN 459-1: 2010 and a new Portuguese NHL3.5 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 superplasticizers; also on mixing and curing conditions. In this paper NHL3.5 mortars with binder:aggregate volumetric proportions1:3 were prepared, 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. The two last mentioned aggregates were byproducts from industry. Prismatic mortar samples and samples of mortar applied over brick were prepared and conditioned in two different situations – following standard EN 1015-11 and at 65% relative humidity with initial daily water spray. 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, of the superplasticizer 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

Earth mortars constructive use on Neolithic domestic structures. Some case studies in Alentejo.

HMC08 - 1st Historical Mortars Conference: Characterization, Diagnosis, Conservation, Repair and Compatibility, LNEC, Lisbon, 24-26 September 2008Earth mortars were constructively used since Ancient Neolithic in Southwest Iberia pre-historic habitat places. According to archaeological information, these materials were applied on Neolithic Period to render ditches; latter, on Copper and Bronze Age, earth mortars were also used binding stone masonry, covering and filling vegetable structures, in mudbrick masonry and probably in massive walls. This paper aims to show some specific information about earth constructive traces obtained in interior Alentejo neolithic settlements of Defesa de Cima 2, Lajinha 8, Horta do Albardão 3, Valada do Mato (Évora district) and Toca da Raposa (Portalegre district). The analysed materials were composed by samples of burned clayish mortars coming from renderings or small thickness walls of probable storage bins and combustion structures. The samples descriptions include the drawing, measurement and photographic record of the chosen traces and also structural and granulometric analysis. The authors believe these analyses can contribute to deeper the knowledge of pre-historic domestic structures and constructive techniques, making possible technological reproduction of habitat settlements

NHL 3.5 mortars with scrap tire rubber

The use of wastes and industrial by-products as building materials is an important issue in order to decrease costs with waste management and the embodied energy of building products. Scrap tire rubber has been studied as aggregate for cementitious materials. Natural hydraulic limes are natural binders with particular characteristics of both air and hydraulic binders. Their specifications became stricter with the last version of EN 459-1:2010. In this study scrap tire rubber was used as additional aggregate of mortars, based on NHL3.5 and natural sand. Different particle size fractions and proportions of scrap tire rubber were used: a mix obtained almost directly from industry (only after sieving for preparation of particle sizes similar to mortar aggregate) and separated fine, medium and coarse fractions; 0%, 18%, 36% and 54% weight of binder, corresponding to 2.5%, 5% and 7.5% weight of sand. The influence of the rubbers´ additions on the mortars´ fresh state, mechanical and physical performance is presented, namely by flow table consistency, water retention, fresh bulk density, dynamic elasticity modulus, flexural and compressive strength, open porosity and bulk density, capillary absorption, drying and thermal conductivity. The use of the rubber mix coming from the waste tire industry seems advantageous and may open possibilities for use as raw material by the mortars industry

Earthen plasters: the potential of the clayey soils of barrocal region in Algarve

Due to their high adsorption capacity of water vapor, earthen plasters can act as a moisture buffer, contributing to balance the relative humidity of the indoor environment of buildings. As a consequence of this capacity earthen plasters may also contribute to the perception of thermal comfort, since a high relative humidity increases the thermal conductivity of air and restricts skin evaporation, increasing the discomfort associated with the perception of heat or cold. Simultaneously, earthen plasters may also contribute to the indoor air quality. In one hand, by mitigating health problems of the respiratory system associated with indoor environment with high relative humidity, in which increases the risk of development of microorganisms usually responsible for infections, allergies or asthma. In the other hand, by mitigating the probability of inflammation of the respiratory system airways associated to exceedingly dry indoor environments. Therefore it also becomes expectable that earthen plasters may contribute for reducing the needs for air conditioning and mechanical ventilation in buildings and, thereby, also allowing the reduction of the associated energy consumption. The «Barrocal» region, located in the sedimentary basin of Algarve, South Portugal, presents geomorphological characteristics that promote the occurrence of soils with a clay mineralogy dominated by illite, which is a clay mineral characterized by a high adsorption capacity of water vapor and low expansibility. This fact turns expectable that these soils have a high potential for interior plastering. In order to evaluate this potential four mortars were formulated with an increasing content of clayey soil extracted from a selected clay quarry from «Barrocal» region. The results from the preliminary characterization campaign confirmed the reduced linear shrinkage of these mortars, as well as their high adsorption-desorption capacity, that is positively correlated with the content of clayey soil present in mortar formulation. However, the mechanical tests showed that the mechanical resistance of these mortars should be improved, for instance through the addition of natural fibers for reinforcement, which will be investigated in future research. This research contributed to increase certainty regarding the potential of clayey soils of the «Barrocal» sub-region of Algarve to produce mortars suitable for eco-efficient interior plastering

Troia Roman baths (Portugal) – Assessment of history of interventions

International Seminar in Conservation. A Tribute to Cesari Brandi. Lisboa, LNEC, May 2006, p.273-282This paper presents a study of one of the roman architectonic complexes from Troia archaeological site: the Roman Baths. The first archaeological excavations campaigns and the different Roman monuments that constitute the whole site are presented, as well as the historical past conservation and restoration interventions and the most important decay factors. The Roman Baths are one example of a complex that has been intervened in, at least, two different periods of time. An assessment was made in order to understand and document its actual state of conservation, to help planning a future coherent conservation operation

Repair mortars for rammed earth constructions

Proceedingsof the XII DBMC – 12th International Conference on Durability of Building Materials and Components, Vol.2, Porto, FEUP, March 2011, p.689-696Rammed earth buildings, with resistant and monolithic walls, often have constructive pathology. A survey on more than thirty rammed earth buildings, mainly in Alentejo region (South Portugal), was conducted. As a result, it was found that surface deterioration of the walls seemed to be an usual problem. Many rammed earth buildings are deteriorating due to lack of maintenance and rehabilitation, but also due to incorrect repairs. Several of them were repaired by applying cement-based mortars in the attempt to overcome the general decay, of the walls that could or not be deep. This paper presents the most common pathology: problems due to water ingress and low drying capacity; salt transport and contamination; construction technology like voids left from the formworks; biological attack; different mechanical behaviour between the walls and the repair mortars - mechanical incompatibility. An intervention methodology for repair the degradation of exterior surface, including anomalies diagnosis and application of these repair mortars, is proposed. The support samples preparation - laboratorial rammed earth blocks with surface deterioration - is also described. Finally, an experimental campaign foreseen for the development and application of earth-based mortars for repair rammed earth walls is presented