Papers by Keyword: Moisture Expansion

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Authors: Andrea Pešová, Jana Andertová, Vladimir Machovič, Ondrej Gedeon
Abstract: One of the general symptoms of ageing is a volume change due to the moisture exposure, known as an irreversible moisture expansion (IME). It is assumed IME of fired clay-based materials is governed by the presence of inner-surface and interlamellar OH-groups, present in clay minerals and assumed to be also abundant in amorphous intergranular phases. IME was measured on a series of clay-based ceramic bodies with a variable content of clay raw minerals under two different hydrothermal conditions. IR spectroscopy was used to correlate IME with the increasing amount of inner and interlamellar hydroxyl groups.
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Authors: Ana M.G.D. Mendonça, Alexsandra Cristina Chaves, Gelmires Araújo Neves, Lisiane Navarro de Lima Santana
Abstract: The study of moisture expansion (ME) in ceramic products has been object of research in the past few years, especially in UFCG. The ME is the increase of the dimensions of the ceramic materials by adsorption of water, it occurs slowly and is relatively small, being able to compromise the adherence of the ceramic plates to the subfloor, lead to the cracking of the glaze and conduct to the appearance of cracks in bricks, if the tensions generated by the deformation contained in the pieces exceed the limit resistance of the materials. Aiming to contribute with this research, this study aimed to characterize the alternative ceramic masses from ceramic blocks, seeking to determinate their influence in the development of the moisture expansion phenomenon. Compositions were formulated through the design of simplexes network mixtures technique. The specimens were conformed by uniaxial pressing at 20 MPa, dried in an oven at 110 °C and fired at temperatures of 800°, 900° and 1000 °C. After firing the MEs were determined by boiling and immersion. The results showed that the higher the percentage of granite waste in the formulation, lower the ME.
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Authors: Jozefa Lukovičová, Gabriela Pavlendová, Stanislav Unčík
Abstract: The problem of the reconstruction of the historical building surface layers is in material compatibility. The basics of the convenient choice of materials for reconstruction is understanding some physical properties of used materials. The crucial properties are moisture and temperature induced deformation. The effect of moisture sorption on the elastic behavior of innovative plaster for renovation is investigated. The measurements are performed for moisture content from the dry state to the saturation water content and temperature range of 10 - 40°C.
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Authors: Ibrahim Mohamad H. Wan, B.H. Abu Bakar, M.A. Megat Johari, P.J. Ramadhansyah
Abstract: This paper presents the behaviour of moisture movement of calcium silicate brick masonry walls exposed to sodium sulphate environment. The walls were exposed to three sodium sulphate conditions with sulphate concentrations of5%, 10% and 15%. For comparison, some walls were also exposed to dry and wet condition which acts as a control conditions. All specimens were prepared and cured under polythene sheet for 14 days in a controlled environmental room and maintained at relative humidity and temperature of 80 ± 5% and 25 ± 2°C, respectively. After the curing period, the specimens were exposed to sodium sulphate as well as drying and water exposures, during which moisture movement was measured and monitored for a period of up to 7 months. As a result, the moisture expansion was observed and recorded for all masonry wall specimens after exposed to the sulphate condition.
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Authors: Fei Xue, Wan Hua Zhao, Yao Long Chen
Abstract: Granite is a kind of high damping material with low thermal expansion, so it is widely used in aerostatic guideways. However, moisture expansion may occur when the granite works in a moist environment, so the applicability of granite to oil hydrostatic guideways is investigated in this paper. By error modeling for a typical closed hydrostatic guideway with four pads, it is shown that the motion errors are mainly determined by geometric errors of the rails when film stiffness of each pads are equal. Experiments on rails of Jinan Dark Green granite are carried out, and the results show the rail straightness variation by the moisture expansion may be less than 1μm/300mm. According to the previous analysis on the error averaging mechanism of hydrostatic guideways, the motion straightness variation may be less than 0.1μm/300mm. In addition, the thickness variation may be less than one ten-thousandth of the rail thickness and the viscosity of liquid has little influence on the moisture expansion.
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Authors: R.A. Andrade, Heber Carlos Ferreira, Romualdo Rodrigues Menezes, Gelmires Araújo Neves
Abstract: Information from technical literature indicates moisture expansion in ceramic materials is reduced due to calcium oxide being incorporated in their raw materials, and, therefore, 12.0% and 18.0% calcium carbonate was used to obtain fired products at temperatures of 850, 900, 950 and 1000oC. Some of these were re-fired to 1000oC, autoclaved and pulverized. Important reductions in moisture expansion occurred for re-fired products obtained from clay/carbonate mixtures. It was found that a few crystalline phases, resulting from incorporating calcium carbonate, appear at temperatures below 900oC in autoclaved and pulverized samples, obtained on using 12.0% and 18.0% calcium carbonate.
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Authors: J.V. Almeida, Victor M. Ferreira, A.M.S. Correia
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Authors: M.A. Carvalho, Ana M. Segadães
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Authors: Hesham Mesbah, Moira A. Wilson, Margaret A. Carter
Abstract: Kaolinite (2SiO2.Al2O3.2H¬¬¬¬2O), an aluminosilicate mineral, is the most common constituent mineral in clay used in manufacturing traditional ceramics such as whitewares, some refractories and structural clay products. On firing, kaolin (mainly kaolinite) undergoes several phase transformations. Immediately following firing, kaolin starts to chemically combine with atmospheric moisture. This reaction causes a mass increase that is proportional to the fourth root of time. The consequence of this mass gain is an accompanying expansive strain. Kaolinite transformations following firing at a range of temperatures between 700 and 1200 oC were examined by XRD. Following firing, high accuracy mass gain measurements were carried out using a microbalance under precisely controlled conditions of temperature and relative humidity. It was found that the formation and development of crystalline phases increases with increasing firing temperature. This causes a reduction in the amorphous phase which, in turn, leads to reduced mass gain. Kaolin fired at 1200 oC exhibited the least reactivity with moisture and mullite was found to be the dominant crystalline phase after firing at that temperature. SEM was used to examine microstructural changes in the fired specimens. The reactivity of the ceramic with moisture is shown to be directly related to the crystallinity of the fired clay.
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