A. Velosa

Fine sepiolite addition to air lime-metakaolin mortars

Abstract Lime-based mortars with admixtures of metakaolin (10,20 and 30 wt.%) and fine sepiolite (5 wt.%) were prepared with the aim of facilitating their use as repair mortars in lowhumidity conditions. The mechanical properties and the dynamic modulus of elasticity were studied after 28,90 and 180 days of curing. With an increasing amount of metakaolin in lime mortars, improved mechanical strength was observed mainly after 90 days. Addition of fine sepiolite, due to its adsorption properties for storing water for later supply to the mortar system and its microfibrous morphology,led to an improvement of compressive and flexural strength of blended air lime/air lime-metakaolin mortars, especially at later ages of curing. Incorporation of fine sepiolite into air lime-metakaolin mortars resulted in comprehensive densification of the core of the mortars. Air lime mortar containing 5 wt.% of fine sepiolite and 20 wt.% of metakaolin appears to be an optimal admixture.

Characterization of Renders, Joint Mortars, and Adobes from Traditional Constructions in Aveiro (Portugal)

The huge and special architectural heritage of Aveiro (Portugal) from the beginning of the past century is characterized by the use of stone or adobe (mud sun-dried blocks), as structural material, with lime renders and mortars. Some of those buildings are situated in the city core and show different degradation degrees, promoted either by weathering in urban context, lack of maintenance, or the seaside proximity. To preserve this type of construction, a study was carried out in order to characterize renders, joint mortars and adobes, to know the composition and behaviour of each in the construction. For this purpose, samples were extracted from various locations of several buildings. The study of mineralogy was performed by x-ray diffraction (XRD), their thermal behaviour was obtained by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), and these data were complemented by chemical analysis by x-ray fluorescence spectroscopy (XRF). The aggregate particle size distributions were obtained by dry sieving. Mechanical compressive strength (Rc) and capillarity performance were also evaluated. The results have shown that the mineralogical composition of joint mortars, renders and adobes are similar and the presence of efflorescences was detected in some samples. In general the capillary coefficients of the adobe samples are higher than those of the renders and mortars related with them. The Rc values were similar for the renders, mortars, and adobes. These studies have also been undertaken to support sustainable interventions, allowing the extraction of salts, the consolidation of renders and production of new compatible renders and mortars to substitute and refill the gaps capable of guaranteeing the integrity and prolonging the existence of this kind of architecture and building technique.

Influence of the mineralogical composition on the properties of adobe blocks from Aveiro, Portugal

Abstract Earth materials have been used in the form of adobe or rammed products for the construction of load-bearing walls in buildings. In Portugal, the adobe has been used predominantly on the central coast, particularly in the Aveiro district. Although many old adobe buildings in Aveiro have been abandoned, some of them can be refurbished with minor maintenance and repair works. Representative samples from typical adobe blocks, from various constructions in the region were collected and characterized for their mineralogical composition, particle size, aggregate content, water uptake, durability and strength. These basic properties provide a basis for the development of adequate interventions, preserving the characteristics of the buildings. This study compares the main characteristics of adobes from two different locations (Anadia and Murtosa). The most important differences between the two groups of adobes are the particle size distribution, the mineralogical composition, the water absorption and the mechanical and durability properties. The study improved the knowledge of the traditional construction methods and will enable decisions for rehabilitation of adobe buildings to be made. Knowledge of the main characteristics of adobes allows those participating in the rehabilitation process to obtain the basis for the rehabilitation and conservation of old buildings.

Reapplication Mortars for Old Tiles: Characteristics of Tiles and Mortars and Selection Criteria

Glazed ceramic tiles have been used as facade claddings prominently since the beginning of the 19th century and they are today considered significant historic heritage. Several deterioration mechanisms threaten this important legacy. Detachment due to aging and to several external actions is one of the most dangerous mechanisms. New mortars compatible with the old tiles and old substrates are needed to reattach the loose tiles without deteriorating the glazed surface, the ceramic part, or the adjacent pieces. The tiles of the 19th century are very porous and absorbent, with variations according to the factory where they were produced. The adhesion of mortars to tiles is commanded by the penetration of the fine particles in the tiles pores, which depend on several composition factors. In this study, the characteristics of late 19th-century tiles are studied and compared with the characteristics of several types of new tiles and replicas. New mortars are formulated with the objective of reapplication of old tiles. The adhesion mechanism of substrate/mortar/tile system is analyzed and the factors involved are identified.

Spent Brewery Grains for Improvement of Thermal Insulation of Ceramic Bricks

AbstractOne by-product of the brewing process is a waste containing spent grains (barley malt and maize grits). In the brewing process, this cake is composed mainly of organic matter containing high fiber content, provided by the separation of suspended particles through wort filtration. The study presented here was carried out to assess if the spent brewery grains could be recycled through their incorporation in a paste used in the manufacture of ceramic bricks, and how such incorporation affects some of the physical properties, namely mechanical strength, porosity, and thermal conductivity of the ceramic material. The main objective of the study was to decrease the thermal conductivity of the ceramic paste without significant losses of the mechanical strength of the final product. Spent brewery grains (SBG) characterized by powder X-ray diffraction, X-ray fluorescence spectrometry, scanning electron microscopy, thermogravimetry, differential scanning calorimetry, and heat of combustion were used as an a...

Characterization of Ancient Pozzolanic Mortars from Roman Times to the 19th Century: Compatibility Issues of New Mortars with Substrates and Ancient Mortars

The use of pozzolanic mortars is widespread, as natural pozzolans coming from South America to Europe and Japan were often incorporated in lime mortars to ensure a pozzolanic reaction and enable the capability of mortars to harden under water (Heikal 2000 ; Holmes and Wingate 1997 ; Moropoulou et al. 1998 ). Their use was especially prominent during the existence of the Roman Empire, when opus signinummortars were used throughout the occupied territories, wherever there was a lack of natural pozzolans; there is evidence that similar mortars incorporating crushed ceramics were employed in other locations such as Syria (Ingo et al. 2004) or Turkey (Degryse et al. 2002 ). Pozzolanic mortars continue to be used nowadays and examples of current applications of lime and crushed ceramic mortars are Surkhi in India and Homra in Egypt.

Adhesion of Air Lime-Based Mortars to Old Tiles: Moisture and Open Porosity Influence in Tile/Mortar Interfaces

The use of tiles in Portuguese facade coatings began in the nineteenth century with industrialized production of tiles. Nowadays, many nineteenth century facades are degraded and in urgent need of maintenance. New bonding mortars must be developed in order to substitute the existing ones. Compatibility, durability, and reversibility with the old materials must be respected. The tile/mortar adhesion strength is a very important characteristic in old tiles reattachment. It mostly depends on characteristics of mortars, porosity, and moisture content of tiles. Mortar in contact with a wet tile will have different binding characteristics than that in contact with a dry tile. This work studies the adhesion of lime-based mortars to old tiles and the influence of moisture and open porosity in the tile/mortar interface. New tiles with similar porous characteristics as nineteenth century tiles were used. A newly designed test was used to test the tile/mortar adhesion strength. The composition of mortars and moisture content of tiles was varied. Some trends of variation of mortar compositions and moisture conditions of tiles were observed in tile/mortar adhesion strength. The increase of moisture in tiles causes the increase of mortars’ open porosity. Mortars applied in wet tiles have higher values of adhesive strength than mortars applied in dry tiles. The tile/mortar adhesive strength increases with increasing open porosity of the mortar in the interface.

Sustainability in earthen heritage conservation

Abstract Earth construction is the oldest building material known, with documented cases of the use of earth bricks since Mesopotamia around 10 000 BC. Earth construction exists throughout most of the world in different cultures, and for some countries it continues to be the main process of construction. Around 30% of the worlds population lives in buildings made from earth materials. Earthen construction is an environmentally friendly technique with a social and cultural contribution; this advantage is increased when this type of construction is applied in developing countries where the material costs counterbalance the labour costs, and where other materials and techniques are not available. Studies of material characteristics are required in order to understand the composition and specific properties of earth buildings, their heterogeneity and their degradation mechanisms. Results from two different types of adobes that represent these material characteristics in Aveiro district are shown, owing to the importance of determining and acknowledging the main characteristics of adobe buildings in order to have sufficient information to initiate conservation and rehabilitation actions.

O papel do metacaulim na proteção dos concretos contra a ação deletéria de cloretos

The objective of this study is to evaluate the protective capacity of concretes produced with metakaolin in relation to the transportation and penetration of chlorides. Thus, from a commercial concrete of fck equal to 30 MPa, more two other concretes were produced by replacing 10% of cement by metakaolin, by weight. In one of them, it was kept the same water/binder of the initial reference mix design (w/b = 0.60), and in the other concrete the compressive strength remained fixed. In all three mixes, the same range of concrete consistency was maintained, with a slump equal to (100 + 10) mm. The front of chlorides in the cement matrix was evaluated by spraying a solution of silver nitrate, after an attack of 8 weekly cycles of wetting and drying using a solution containing chlorides. To obtain an indicative of the internal structure of the concretes, it was carried out the test of water absorption by immersion, which permitted an evaluation of the concrete open porosity, as well as it was performed the analysis of concrete samples by means of XRD and SEM. These studies aimed to verify the potential of metakaolin in fixing chlorides in the form of Friedels salt, besides providing microstructural analysis of the concretes. It was concluded with this work that the incorporation of metakaolin decreases the diffusivity of chlorides to the extent that this mineral addition produces refinement of the concrete pore structure and also because it induces the formation of Friedels salt, which becomes it an effective agent in preventing the corrosion of reinforcement in chloride-rich environments.

Technical replicas of Portuguese ceramic tile bodies produced in the Oporto region in the late nineteenth to early twentieth centuries

Portugal is well known for its facades decorated entirely with ornamented glazed ceramic wall tiles called azulejos. On ageing, the tiles may detach and fall off, or deteriorate to such an extent that it becomes necessary to replicate them. Hence tile replication is a common practice in Portugal for façade restoration, but very often these new tiles do not have the same physical and/or chemical properties as the original ones. Such differences might be a factor in differential deterioration of the façades after restoration. One step toward an improvement in compatibility is to make new ceramic bodies with the same characteristics as the original ones. This study focuses on two types of glazed ceramic wall tiles from the Oporto region in Portugal: ‘calcic faience’ and pó de pedra. A total of 25 samples from the late nineteenth to early twentieth centuries were studied systematically as an attempt to improve knowledge of these materials and to create a basis for their replication. All samples were collected from facades that were under conservation/restoration at the time when sampling was performed. The original traditional ceramic bodies were analyzed by X-ray diffraction and X-ray fluorescence. Total open porosity, capillary absorption coefficient, and mercury intrusion porosimetry were also measured in order to gain knowledge on their physical characteristics in addition to their chemical and mineralogical compositions. High-temperature crystalline phases such as diopside, gehlenite, and mullite were found in the calcic faience, suggesting that the firing temperature of calcic faience bodies was within the range of 1100–1150 °C. Calcination trials were also performed in order to determine the most probable firing temperatures of the ceramic bodies. Collected data led to the assumption that the raw materials used for the ceramic bodies were kaolinitic clay, quartz sand, limestone, and talc. The raw materials for pó de pedra tiles were found to include kaolinite clay and quartz with firing temperatures estimated within the temperature range of 1150–1360 °C. Technical replicas made on the basis of these investigations were found to have the same mineralogical and capillary properties as the original tiles.