Papers by Keyword: Limestone

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Authors: Carlos A. Anjinho, Pedro M. Amaral, Jorge Cruz Fernandes, Luis G. Rosa
Abstract: The objective of this work is to present a new laboratory testing methodology suitable for estimate the forces generated during multiple blade gangsawing employed on marble and limestone. This methodology allows analysing the tool behaviour aiming to contribute for developing new products and/or optimize the working conditions for processing different classes of stones. In the present research, 3 different diamond linear blades were tested against 2 types of stones (limestone and marble), studying the effect of two working parameters. The linear blades differ in the characteristics of the segments: size of diamond grit and type of metallic binders used to embed the diamond. The classification equipment used in this work consists in a special bridge cutting machine incorporating a tailored instrumentation / sensing system to control the working conditions while all the necessary cutting outputs are monitored and stored by special software. Taking into account the output parameters measured to evaluate the tool behaviour (vertical and horizontal forces, electric energy consumption, vibrations measured by accelerometers and tool wear); it is possible to classify and select tools with relation to the efficacy of the cut.
Authors: Kuo Hsin Lin, Po Hsueh Chang, Ching Tsung Yu, San Yuan Chen
Abstract: In this work, a series of CaO-based materials for medium-high temperature (500-800 °C) CO2 capture were synthesized from limestone by acidic treatment. In order to enhance its thermal stability, CaO-based materials were modified with Al(NO3)3. With various stirring time of 24, 48 and 72 hours, three types of CO2 capture sorbent were synthesized, named LA24, LA48 and LA72, respectively. TGA results showed the CaO-based materials were activated in the CO2 capture reaction of temperature range of 500-800 °C. LA24 exhibited the best CO2 capture capacity of 53.8 wt % as well as stability of 93.2 % after 10 cycles test. Furthermore, all of the modified CaO-based materials showed good thermal resistance upon 900 °C. It was consistent with expectation by the contributions of alumina coexistence with calcium oxide. XRD results indicated that CaO dominated in the diffraction spectrum before capturing CO2, and a side diffraction peak of Al2O3 was also observed. The characterization of CaO-based materials was also investigated by BET and SEM, respectively.
Authors: Tereza Valentová, Jan Valentin
Abstract: Deterioration of asphalt pavements by water immersion and increased moisture content, presents one of the principal issues for pavement technologists. Especially if concentrating on initial phases of the life-cycle of a pavement. Water in the form of rain precipitation and natural air moisture can be harmful to the bonds between bitumen and aggregate particles, which occurs through the medium deteriorated adhesion on the interface of those phases, or the overall deterioration of the adhesion. Even if it might look at the first glance that bituminous binder creates perfectly impermeable layer of particular aggregate particles, in reality the bitumen film makes unstable coating of aggregates in unequal thicknesses and frequencies. Those weakened areas are far more susceptible to water and moisture affects, which enter the asphalt layer on the boundary of aggregates and bituminous binder. To improve the adhesion between bitumen and aggregates and to get in general better functional characteristics of asphalt mixtures large number of available additives exists in civil engineering. First group can be defined as additives which are added directly to the bituminous binder and provides a kind of bitumen modification. Second group includes mineral additives, which may partially or completely replaced fine-grained particles, normally in the form of filler. In this article the objective was set to qualify effect of mechanically activated microfiller originating from limestone by-products or from recycled concrete as a substitute to fine-grained active filler in asphalt mixtures. The research targeted to utilize waste materials and to contribute to the reduction of overall negative impacts to the environment.
Authors: Ozgur Akkoyun, Nicola Careddu, Graziella Marras
Abstract: In this study, a new computer program developed to determine the colour properties of natural stone products is introduced. The program can scan any digitalised picture of natural stone products and produce several statistical results such as mean, variance, minimum and maximum colour values, skewness and kurtosis values of the colour histogram, energy, contrast, entropy and homogeneity values of the data which may be used to classify the typology and/or quality of natural stone products. As a case study, Orosei limestones (Sardegna, Italy) were used. There are several typologies of Orosei limestones such as Nuvolato (Cloudy), Venato chiaro (Light veined), Venato medio (Medium veined), Venato scuro (Dark veined), Perlato chiaro (Light pearled), Perlato medio (Medium pearled) and Perlato scuro (Dark pearled). The remarkable results produced by the program are presented.
Authors: Wen Ye, Yong Min Yang, Heng Chang Wang
Abstract: The aim of this paper is to systematically investigate the alkali activity of the aggregate selected from a stockyard, and examine its supression method, before pouring roller compacted concrete into the hydro project in Lechang gorge. Samples of natural sand, sandstone and limestone will be analysed through comprehensive petrographic method and accelerate mortar bar method. The results showed that natural sand is the aggregate without activity; sandstone core contains some wave shape with extinction characteristics of deformation quartz, because of active alkali-aggregate and the harm expansion of mortar, which is the aggregate with potentially harmful alkali-silicate reaction; wave shape and elastic deformation of the alkali in limestone are also the harmful element in concrete. The addition of level 1 and level 2 fly ash both has the ability to inhibit the reaction between alkali and silicate, and can control expansion rate of sandstone under 0.1 %.
Authors: Sergey M. Fomenko, E.E. Dilmukhambetov, Zulhair A. Mansurov, Zhanibek A. Korkembai, Aleksandr F. Reshetnyak
Abstract: This paper summarizes the results of the limestone furnace upgrade / refurbishment using the SHS-refractory material upon the furnace gas distribution coring.
Authors: Dušan Dolák, Karel Dvořák, Jaroslav Bureš, Dominik Gazdič
Abstract: Thermal treatment of materials involves phase transformations. In the case of conventional laboratory furnace or in an industrial process, the samples are analysed after cooling. In this way, these phases can be monitored. A possible solution is non-ambient XRD analysis. Using HT-XRD analysis, it is possible to monitor the mineralogical composition at different temperatures in real time. The results of measurements on chemically precipitated limestone and limestone from the Cretaceous era show slight differences in temperature of decarbonation, but not clearly demonstrated the presence of unstable phases. This measurement, however, allowed the observation of a change in the size of the crystallites in the change of temperature.
Authors: Eva Vejmelková, Jaroslava Koťátková, Monika Čáchová, Dana Koňáková
Abstract: The article compares the basic physical, mechanical and both liquid water and water vapour transport properties of self-compacting concrete containing different pozzolanic admixtures. Limestone, fly ash and metakaolin were used. A concrete mixture without any pozzolana was also manufactured as a reference. The best values of studied properties were recorded for the metakaolin concrete.
Authors: Lei Su, Gang Zhang, Yu Dong, Jian Feng, Dong Liu
Abstract: The thermal decomposition kinetics of magnesite and limestone, which are alkaline earth metal carbonates, were investigated using thermal analysis method. The research results showed that their kinetic decomposition characteristics and apparent decomposition activation energy have the comparability. Based on the thermodynamic/thermogravimetric data, the industrial production process of magnesite and limestone can draw on the experience of each other because of their similar decomposition thermodynamics and kinetics.
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