Browsing by Author "Rocha, Fernando"
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- An insight into the surface properties of calcined kaolinitic clays: The grinding effectPublication . Gamelas, José; Ferraz, Eduardo; Rocha, FernandoThe present work aimed characterizing in a systematic way the surface of metakaolinitic materials produced by calcination of a kaolinitic clay at different temperatures and to study the effect of grinding on the surface properties of metakaolinitic materials. Using X-ray photoelectron spectroscopy, it was found for all materials a Si/Al atomic ratio close to 1, confirming the presence of the 1:1 clay structure. By inverse gas chromatography, an increase of the Lewis basic properties of the surfaces of metakaolinitic materials in comparison to the original clay was found, which was due to the condensation of hydroxyl groups in the structure of the clay. The grinding of the metakaolinitic materials afforded a decrease of the dispersive component of the surface energy () as well as an increase of the specific interaction with sterically hindered molecules, caused by the diminishing of the materials surface nanoroughness. The Lewis basic properties of the materials surface also increased with grinding. Noticeably, for all studied materials a good inverse relation could be found between the and the specific interaction of trichloromethane (but not with dichloromethane), showing the importance of surface nanoroughness on the adsorption process of bulky molecules.
- Clays from Vila Nova da Rainha (Portugal): Appraisal of their relevant properties in order to be used in construction ceramicsPublication . Coroado, João; Ferraz, Eduardo; Gomes, Celso F.; Rocha, FernandoThe clay deposit of Vila Nova da Rainha (VNR) is included in the lithostratigraphic forma tion named “Argilas de Tomar”, and is located at the lower section of the Tert iary 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 cl ays containing quartz, alkaline feldspar, iron oxy-hydroxides, and clay minerals have been studied. Ca rbonates have not been identified in thes e 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 mu llite 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 lo west mechanical bending strength value (12.0 MPa); the same properties assessed in the second group provi ded 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.
- Deterioration of the “Quinta Nova Torres Vedras” wall tile panel – an analytical approachPublication . Triães, Ricardo; Santos, Luis; Coroado, João; Rocha, FernandoWall tile panels were commonly used in recreational open outdoors spaces in 18th Century noble houses I Portugal. The nature of their location and the lack of maintenance of such spaces, which lost their purpose during the 20th century, contributed to their natural deterioration. In order to preserve one such panel and facilitate the conservation treatment, it was removed from its location and transported to the facilities of the Polytechnic Institute of Tomar, Portugal. The interest in studying this particular panel was prompted by the advanced stages of deterioration observed in some tiles, where natural succession of biological colonisation and weathering were registered as some of the main deterioration causes. Furthermore, the advanced deterioration stages indicate that removal was a necessary action, as natural weathering would lead to its destruction. The study involved a thorough analysis of the environmental characteristics of the wall placement, the wall materials themselves, the mortar, the ceramic body and the glaze. The methodologies used involved microscopic and laboratory testing to evaluate the extent of lichen colonisation and its influence in the loss of glaze and posterior deterioration of the ceramic body. Results indicate that natural and environmental characteristics, combined with substrate typology and micro-organisms, contribute to accelerate the deterioration process, though appropriate techniques of preventive conservation can be used in specific panels or broader situations. This study will enable the development of innovative methodological and technical approach to the conservation problem here portrayed.
- Eggshell waste to produce building lime: calcium oxide reactivity, industrial, environmental and economic implicationsPublication . Ferraz, Eduardo; Gamelas, José A. F.; Coroado, João; Monteiro, Carlos; Rocha, FernandoEggshells wastes are produced in huge amounts worldwide. The recycling or valorization of this waste, which otherwise is usually disposed in landfills, represents an opportunity within a circular economy perspective. In the present work, the potential of chicken eggshell waste to produce calcitic lime was explored. After collection from an industry supplier, the waste was thoroughly characterized for its mineralogical, chemical, and thermal properties. The material was calcined at 1000 °C, and the obtained calcium oxide was evaluated for its reactivity in wet slaking tests. Comparison was made with commercial limestone used as reference. It was found that the calcium oxide from eggshell waste belonged to the most reactive class (R5—60 °C within 10 min), the same of the calcium oxide from limestone. However, different times were obtained to reach 60 °C (25 s and 4:37 min:s) and for 80% of the reaction (28 s and 5 min) for calcium oxide from limestone and eggshell waste, respectively. The lower reactivity of calcium oxide from eggshell waste was related to its larger size particles with smoother surfaces and lower specific surface area in comparison to limestone calcium oxide. Industrial, environmental and economic implications concerning the use of this waste to produce lime were also evaluated. The eggshell waste could be all consumed at an industrial scale in Portugal allowing for approximately 2.6% partial substitution of limestone in a lime factory.
- Manufacture of Ceramic Bricks Using Recycled Brewing Spent KieselguhrPublication . Ferraz, Eduardo; Coroado, João; Silva, Joaquim Pedro; Gomes, Celso; Rocha, FernandoIn the brewing process, kieselguhr performs as a filtration medium and one generated by-product is a sludge containing kieselguhr, which is mainly composed of fragmented diatom frustules associated to organic material retained during the clarification process. The physic-mechanic tests were performed on assemblages with brick composition and brewing spent kieselguhr containing 3, 9, and 15 wt% incorporation levels of sludge, being extruded and dried (105ºC) before being submitted to slow firing at 900ºC, 950ºC, and 1000ºC. The obtained results showed that, even when at its maximum incorporation level, the spent kieselguhr for all firing temperatures do not cause important losses on the properties exhibited by the clay paste without kieselguhr incorporation and the best incorporation levels are 4.2 wt% when fired at 900ºC, 9.8 wt% when fired at 950ºC, and 13.4 wt% when fired at 1000ºC. When fired at 950ºC, 15 wt% addition of spent kieselguhr increased by 27% the open porosity and decreased by 10% the bulk density of the brick paste. Furthermore, physic-mechanic tests and ecotoxicity evaluation on semi-industrial brick manufactured with 9 wt% of brewing spent kieselguhr were accessed. The results do no show any constrain concerning mechanical properties, and the ecotoxicity evaluation shows the safety of the brewing spent kieselguhr incorporation in ceramic products.
- Pozzolanic activity of metakaolins by the French standard of the modified Chapelle test: A direct methologyPublication . Ferraz, Eduardo; Andrejkovicová, Slávka; Hajjaji, Walid; Velosa, Ana Luísa; Silva, António Santos; Rocha, FernandoThis research was focused on the use of the modified Chapelle test as a direct laboratory methodology to access the pozzolanic activity of both experimental and commercial metakaolins. At the same time, this test was used in the evaluation of experimental metakaolins. This chemical test, performed during 16 hours at 90 °C, allows the quantification of portlandite fixed by the metakaolin sample. The calcium hydroxide that was not consumed is quantified by acid titration (HCl), and the test result is expressed in mg of fixed calcium hydroxide by g of metakaolin. According to this test, the pozzolanic activity of a metakaolin should not be less than 700 mg Ca(OH)2 / g metakaolin. The modified Chapelle pozzolanic activity of six commercial metakaolins was evaluated between 920 and 1560 mg Ca(OH)2 / g metakaolin. From the seven experimental metakaolins produced between 750 ºC and 940 ºC, a material with modified Chapelle pozzolanic activity value of 1240 mg Ca(OH)2 / g metakaolin was obtained, which is similar to some tested commercial metakaolins produced at industrial scale. The metakaolin produced at 800 ºC was ground, resulting in a particle size reduction of ≈ 4x less and a consequent increase of 21% in the pozzolanic activity.
- Recycling Waste Seashells to Produce Calcitic Lime: Characterization and Wet Slaking ReactivityPublication . Ferraz, Eduardo; Gamelas, José A. F.; Coroado, João; Monteiro, Carlos; Rocha, FernandoThe present work aimed at valorizing marine bivalve shells. First, clam, mussel, edible cockle, wedge, razor, oyster, dog cockle and scallop shells wastes were thoroughly characterised for their mineralogical, chemical and thermal properties. Then, the materials were calcined at 1000 °C, milled and sieved to lower than 0.250 mm. The obtained calcium oxide was subjected to wet slaking test to evaluate its reactivity in the production of hydrated lime. The reactivity results of the calcined materials showed that, dog cockle (60 °C in 7:54 min:s) and edible cockle (60 °C in 9:20 min:s) can be classified in the most reactive class (R5) in which 60 °C is reached in less than 10 min. The remaining species were classified in the R4 class, reaching 60 °C between 10 and 25 min, with the lowest reactivity being found for oyster shell (60 °C in 19:09 min:s). Interestingly, the hydrated limes from seashells typically presented a white tonality superior that of the lime from commercial limestone used as reference. Overall, seashell wastes can be used in the production of lime, with several benefits, including, the inexistence of environmental impacts related to the exploitation of limestone on quarry, lesser energy spent in the comminution process, or, inexistence of disposal costs related with landfill tariff. These wastes could thus be used as raw materials in other industrial sector.
- Spent brewery grains for improvement of thermal insulation of ceramic bricksPublication . Ferraz, Eduardo; Coroado, João; Gamelas, José; Silva, Joaquim Pedro; Rocha, Fernando; Velosa, Ana LuísaOne 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 additive (pore-forming agent) to a brick paste, characterized by powder X-ray diffraction, particle-size analysis, mechanical strength, plasticity index, and thermal conductivity determinations. Powder mixtures obtained by addition of 5, 10, and 15% by weight of dry SBG to brick raw material (SBG-to-brick paste weight) were assembled. The powder mixtures were extruded and the green probes were dried (105°C) before slow firing at 900, 950, and 1,000°C. Drying and firing shrinkages and mechanical bending strengths were investigated in addition to bulk density, open porosity, water absorption, and thermal conductivity of the fired samples. The mixture of ceramic paste with SBG fired up to 900°C with an incorporation of SBG of 5% by weight was found to reach a compromise between the highest mechanical bending strength (15 MPa) and the lowest thermal conductivity (0.46 Wm−1K−1). When compared with the ceramic paste without SBG incorporation, a diminution of 12 and 28% of the values of these properties, respectively, was obtained.
- Synthetic zeolite pellets incorporated to air lime metakaolin mortars: Mechanical propertiesPublication . Ferraz, Eduardo; Andrejkovicová, Slávka; Velosa, Ana Luísa; Silva, António Santos; Rocha, FernandoIn this study synthetic fine and coarse zeolite pellets were chosen in the development of air lime–metakaolin mortars for repairing ancient masonry to be used in conservation and restoration of cultural heritage. Synthetic zeolite was used due to their particular water adsorption properties and act as an artificial pozzolan promoting the development of hydraulic phases. Physical, chemical, mineralogical and microstructural tests were accomplished to characterize the materials used in mortars’ preparation. Flexural, compressive strength and dynamic modulus of elasticity tests were performed in mortars at 28, 90 and 180 days of curing. Incorporation of both fine and coarse zeolite pellets caused improvement of mechanical strength of mortars. The highest flexural strength value (∼0.5 MPa) was achieved in both mortars with fine zeolites pellets at 90 days and 20 and 30 wt.% metakaolin, and coarse zeolite pellets at 180 days and 30 wt.% metakaolin as lime replacement. 1.0 MPa was the highest compressive strength value obtained at 180 days for mortars with both fine zeolite pellets and coarse zeolite pellets, with 20 and 30 wt.% of metakaolin, respectively. Elasticity modulus ranged from 2.3 GPa to 3.9 GPa confirming the high deformation capability of these mortars. Zeolite pellets type A is a promise synthetic material that could be successfully used in air lime–metakaolin render mortars for applications in the conservation and restoration of cultural heritage.