The requirements of conservators who take care of historical monuments are that the materials for rehabilitation of old renders should have a composition as similar to the historical materials as possible and should provide improvement in durability. Fine and coarse sepiolite and synthetic zeolite pellets were chosen as additives in the development of lime mortars for conservation work, due to their unique adsorption properties providing water to the mortar system and acting as water reservoirs in conditions of low humidity. Flexural and compressive strength and the dynamic modulus of elasticity were studied at 28, 90 and 180 days of curing. Addition of both fine and coarse sepiolite and zeolite pellets caused improvement of mechanical strength of mortars, clearly evident at later ages of curing. Elasticity modulus ranged from 2.3 GPa to 3.6 GPa relating to a high deformation capability of mortars and confirming their suitability for use in conservation work., Slávka Andrejkovičová, Eduardo Ferraz, Ana L. Velosa, António S. Silva and Fernando Rocha., and Obsahuje bibliografii
Diatomite is a siliceous sedimentary rock, and it can be used in many industrial applications due to its high porosity, low density porous and permeable structure, chemical resistance, high purity, high specific surface area, absorptive capacity and to its absorbent properties. The best known Portuguese occurrences of diatomite are located in the regions of Óbidos and Rio Maior. The purpose of this research is to characterize the Rio Maior and Amieira diatomite and beneficiate this rock to be used in some potential applications locally or not. The studied diatomites present a fine texture; chemically the samples have a high SiO2 content, the principal minerlas are quartz and amorphous opal. The studied diatomites benefited with temperature and addition of NaCl (acting as accelerator of the crystallization process), with 5 % of NaCl being reduced the transformation temperature of the amorphous opal in opal C / CT at about 200 ºC. The diatomites from Rio Maior and Amieira in natural state has an enormous potential as absorbent, of heavy metals (e.g. in soil contamination) or dyes (textile industry). These diatomites after beneficiation can be used in construction materials (as additive), being more reactive and crystalline than in the natural state, diatomites can be promoters of mechanical resistance in mortars and geopolymers. and Costa Cristiana, Velosa Ana, Cerqueira Angela, Caetano Paulo, Rocha Fernando.
The clay deposit of Vila Nova da Rainha (VNR) is included in the lithostratigraphic formation named "Argilas de Tomar", and is located at the lower section of the Tertiary Tagus’ river basin. Clay from one quarry is being extracted for the production of construction ceramics. In this work the firing transformations undergone by VNR clays containing quartz, alkaline feldspar, iron oxy-hydroxides, and clay minerals have been studied. Carbonates have not been identified in these raw materials. The clay layers can be subdivided in three groups based upon composition and ceramic properties. The first group, VNR0, is represented by smectite-kaolinite sandy-silty clay, the second group (VNR1 and VNR2) corresponds to illite-kaolinite bearing clay and the third group (VNR3 and VNR4) is represented by illite-smectite silty clay. The firing process involves the formation of hematite and mullite both influencing the technical properties of the fired products. With regards to the ceramic properties assessed at 1100 ºC the first group showed the lowest total shrinkage value (7.35 %) the highest water absorption value (12.2 %) and the lowest mechanical bending strength value (12.0 MPa); the same properties assessed in the second group provided the highest firing shrinkage values (7.0-5.0 %), the lowest values of water absorption (0.1-0.2 %) and relatively high mechanical bending strength values (47.8-48.0 MPa); the third group showed firing shrinkage values within the range 3.5-4.2 %, water absorption values within the range 1.4-4.5 %, and the highest mechanical bending strength values (49.2-52.0 MPa). The results of the ceramic properties being appraised indicate that the raw materials being studied are suitable for the production of high-quality construction ceramics, such as brick, roof tile and rustic floor tile., João F. Coroado, Eduardo Ferraz, Celso F. Gomes and Fernando Rocha., and Obsahuje bibliografii
Three different metakaolins processed by a Portuguese factory were studied aiming to assess the influence of chemical and mineralogical composition of metakaolin on mortar characteristics. Mineralogical analysis of both the fine and clay fractions was carried out by X-ray diffraction. Chemical composition (major elements) was analyzed by X-ray fluorescence. Mineralogical composition reveals some significant differences between the studied samples, in both analyzed fractions, metakaolin 2 being richer in kaolinitic minerals. From a chemical point of view, siliceous content is always high (aroun d 60 %) as well as Al2O3 content (around 30 %); once again metakaolin 2 is the one richer in Al2O3 and poorer in sodium and potassium. Metakaolin from the three different batches was incorporated in lime mortars in order to produce a pozzolanic reaction and hence enable them to harden in high relative humidity conditions or, when access to CO2 is limited, as in the case of mortars supporting glazed tiles. Mortars with the same volum etric ratio were tested for flexural and compressive strength at ages of 28 and 90 days, and the module of elasticity was dete rmined. A relation between the mechanical strength achieved by lime mortars with the addition of metakaolin from different batches and metakaolin mineral and chemical composition was assessed. The knowledge of the influence of the metakaolin com position on the strength of the mortars is an important step in improving their performance and extending their application., Ana Luisa Velosa, Fernando Rocha and Rosário Veiga., and Obsahuje bibliografické odkazy