Papers by Keyword: Dolomite

Abstract: Dolomite is a raw carbonate mineral rich in contents with calcium, magnesium and oxide compounds also including other minor impurities from other compounds. It could be easily found in sedimentary rock which is most likely known as dolostone associated with limestone and chalk carbonates. This mineral has been used in a variety of industries including agricultural, metallurgy, constructions, biomass and others. Currently, there are abundant sources of local dolomite minerals but have very limited applications when compared to other types of carbonate minerals. This was contributed by the lack of basic technical information on dolomite properties and no extensive research has been done to evaluate the new potential of this mineral. Therefore, this paper made a brief review on the important characteristics, properties and thermal behavior of dolomite and based on these findings discussed the dolomite's suitability and potential to be used as bioceramics and in biomedical applications.

Abstract: Dolomite is widely used in the construction, glass ceramics, iron and steel, pharmaceutical industries, as a source of CaO and MgO and as thermal energy storage material. Thermal decomposition analysis of natural dolomite of the so-called Jeddih limestone has been carried out. A thermogravimetry analysis (TGA) in the air evaluates the thermal decomposition of dolomite. The natural dolomite has been analyzed by x-ray flourescence (XRF) and x-ray diffraction (XRD) to test crystal structure and decomposition phase, fourier transform infra-red (FTIR) was utilized to identify the presence of functional groups. The particle morphology was observed by scanning electron microscopy. TGA curve shows that the thermal decomposition of dolomite occurs in two stages. The first stage is in temperature range of 600 - 779°C and the second one is at the temperature 779°C. The results are in line with the XRD and FTIR measurements. Which shows that calcite begins to grow at a temperature of 600°C and MgO phase is observed at 700 - 900°C. Moreover, CaO phase starts to be found at 800°C.

Abstract: Dolomite has great potential to be employed as filler or nanofiller in polymer composite/nanocomposite system. However, the research on dolomite as filler or nanofiller in polymer composite is still immature, requiring further investigations on how to optimize the dispersion of the dolomite in the polymer matrix, thus improving its properties. Particle size reduction of dolomite can be an efficient approach to increase its surface area and facilitate its dispersion and distribution within polymer matrix in order to develop homogeneous composite/nanocomposite system. In this study, the dolomite in pulverized form was obtained from Perlis Dolomite Industry, Malaysia with the average particle size of 150μm. In order to reduce the size of this dolomite, we have initially employed the planetary ball milling method. Results indicate that the particle size of dolomite has been reduced from 150μm to 2μm after subjected to ball milling process. This shows that upon ball milling procedure, the size of dolomite particle is still in micronmeter. Next, the ball milled dolomite was subjected to tip-sonication process to obtain dolomite in nanosize range. Several tip-sonication parameters, which were; amplitude and number of sonication repetition were applied in order to select the best parameters that can produce the finest dolomite powder. SEM and TEM were used to characterize the microstructure of the raw dolomite and the size reduced dolomite. Our results show that when the ball milled dolomite was tip-sonicated, much smaller particle size was obtained. Dolomite with the smallest particle size (~200nm) was obtained when the tip-ultrasonication was performed 3 times at amplitude of 50. These findings indicate that the combination of ball milling and tip-sonication is an efficient method to produce very fine dolomite particles, up to nanosize range. Furthermore, it is a clean, simple method and not involved any toxic and harmful chemicals.

Abstract: Cement grouts have many purposes in various civil engineering applications such as precast construction, soil stabilization and structural rehabilitation. Using filler materials as a component in cement grouts has been increasingly implemented. The incorporation of such fillers not only does improve the fresh and hardened properties of grouts but also contributes to the decarbonization of grouts by reducing the amount of Portland cement, thereby lowering the carbon footprint of grouting materials. This study aims at assessing the influence of various filler materials on the properties of cement grouts. Three different fillers were used in this study: commercial limestone, commercial pure dolomite, dolomitic quarry dust. These fillers were assessed in terms of their effect on the spread, flowability, cohesion and compressive strength at 3, 7 and 28 days. The results show that fresh properties of the grout were dependent on the type of fillers. Dolomitic quarry dust improved the workability and flowability more than the commercial limestone and dolomite did. The compressive strengths of cement grouts did not change significantly with the incorporation of the fillers. However, cement grout samples including quarry dust exhibited slightly higher 28-d compressive strength than other samples although the same mix had lower 1-d compressive strength than other mixes. This study highlights the benefits of utilizing quarry dust in cement-based binders without compromising the performance.

Abstract: This research studies on the effect of additive (Dolomite) on Biomass powder (Cassava rhizome) which passes Torrefied process and fixed bed at 250 degrees Celsius for one hour and a half. The gasifier with up-draft type was used in this experiment. Air pressure was fixed at 0.1 Bar. The useful heat (Q_useful) and Low heating valves (LHV) was investigated by using an Automatic Bomb Calorimeter. Moreover, the dolomite was varied 0, 10 and 15% by weight mixed with Cassava rhizome achieved with Torrefied process. When Low heating valves (LHV) slightly decreases from 21.96±0.22 MJ/kg to 18.15±0.50 MJ/kg, Q_useful heat from the burning from gasifier sharply increase when it is mixed with dolomite from 753.34±39.18 to 1,003.97±33.49KJ respectively. The loading of dolomite has significance affecting the useful heat. The present study reveals that low heating valves (LHV) decreases and Q_useful heat increase result from dolomite which gives a clean gas product and the Tar molecule can be easily broken. The CO₂ gas from the combustion process was absorbed by CaO, which is the main component in dolomite. The cost of mixing 8.9% of Dolomite with Cassava rhizome is the optimum ratio for the biomass combustion process.

Abstract: Dolomite is one of the commonest minerals that abound in the formation of a number of geological conditions. And it is found in abundance in eastern Algeria, especially Ain Mlila-Wilaya of Oum El Bouaghi-Algeria. The analyzed sample of raw dolomite has been by various physical-chemical techniques. The constituents of these carbonates are Ca, Mg, C, O, Al, Si, Fe, Ba, F, and Sr, analysis by XRD, and Raman, show that in addition to CaMg(CO₃)₂, we may have calcium carbonate. The Photoluminescence analysis characterizes the intrinsic and extrinsic defects of this carbonate. Differential thermal analysis reveals the different transformations of this mineral during heating. Indeed several stages including the elimination of water, the departure of CO₂, the formation of MgO, and finally the formation of CaO.

Abstract: In the present study, the CaO/Natural Dolomite as a heterogeneous catalyst was applied to synthesize biodiesel from coconut oil. The physico-characteristics of CaO/Natural Dolomite catalyst were determined using X-ray diffraction (XRD), X-Ray Fluorescence, and porosity analysis (specific surface area, average pore size diameter and total pore volume). The performance of CaO/Natural Dolomite catalyst was examined in a batch reactor for transesterification reaction of coconut oil with methanol. From the experiments, the optimum process conditions were achieved at a 60°C of reaction temperature, a 5 wt.% of catalyst amount, and 6 : 1 of methanol to coconut oil mass ratio. The CaO/Natural Dolomite catalyst exhibits high catalytic activity and reliable to be applied in biodiesel synthesis as a heterogeneous base catalyst.

Abstract: In this study, an activated natural dolomite catalyst is used as catalyst for the palm empty fruit bunches (PEFB) pyrolysis to produce bio-oil. The research was conducted in fixed bed reactors operating in batches by varying several parameters, which are temperature (400-600°C) and nitrogen gas flow rate (100-300 mL.min^-1). The results show that the catalytic pyrolysis process using an activated natural dolomite catalyst obtains a maximum liquid yield of 35.87% when using a 500°C catalytic pyrolysis temperature and the rate of nitrogen gas is 100 cm³/minute, while the yield of gas and solids is 53.12% and 11.76%, respectively. The use of the dolomite activation catalyst influences the product distribution of pyrolysis and the bio-oil chemical compounds.

Abstract: Geopolymer concrete (GPC) is the most advanced form of concrete amongst the various types of concrete developed so far. This paper aims at investigating the feasibility of using Ground Granulated Blast furnace Slag (GGBS) as a base material for geopolymer concrete. Effect of dolomite, which is a by-product from rock crushing plant on GGBS based GPC, was studied. Maximum compressive strength was obtained when GGBS and dolomite were proportioned at 70:30. Steel fibres were added to geopolymer concrete (SFGPC) to improve the ductile behaviour and its brittleness index was compared with Ordinary Portland Cement (OPC) concrete. Strength and behaviour of GGBS-Dolomite GPC and SFGPC flexural member subjected to cyclic loading are explained in this paper. Steel fibres are added at 0.25%, 0.5% and 0.75% volume fraction of concrete. Properties such as load deflection behaviour, ultimate load, crack width and ductility were compared with OPC concrete beams.

Abstract: In this study, the phonon-based thermal conductivity of magnesite (MgCO₃) and dolomite (CaMg(CO₃)₂) is calculated and compared with an earlier recent calculation on calcite (CaCO₃). Equilibrium molecular dynamics simulation by way of the elegant Green-Kubo formalism is used for calculating the thermal conductivity. The thermal conductivity is investigated over a wide temperature range (from 200 K to 800 K) for all of the above mentioned materials. The most reliable potential parameters are used for characterising the interatomic interactions. In all of the models, two independent mechanisms are considered. The first is temperature independent, which is relevant to the acoustic short-range and optical phonons, and the other is temperature dependent, which is linked to the acoustic long-range phonons. In the study, the heat current autocorrelation function (HCACF) is calculated over the averages of the NPT, NVT and NVE ensembles in the x- and z- directions. In addition, it is shown that the optical, acoustic short- and long-range phonon modes are the main contributors to the decomposition model of the thermal conductivity. In a further investigation, the effects of the computational cell sizes on the thermal conductivity are investigated with five different simulation blocks containing 30, 240, 810, 1920 and 6480 atoms. Finally, this research provides a comparison of the thermal conductivity from this study and experimental studies: they are in good agreement.