Papers by Keyword: Volcanic Ash

Abstract: The aim of this study is to analyze the mechanical and physical properties of refractory bricks produced via geopolymerization using volcanic ash. Volcanic ash was combined with 12 M sodium hydroxide (NaOH) and sodium silicate (Na₂SiO₃) as activators, with a liquid-to-solid ratio of 0.2. Two brick prototypes were produced: a cylindrical specimen for testing compressive strength and water absorption, and a rectangular prism for analyzing thermal conductivity. The bricks were calcined at 600°C and 800°C, showing favorable performance compared to well-known commercial refractory bricks. Cylindrical specimens calcined at 600°C reached an average compressive strength of 5.51 MPa, while those calcined at 800°C averaged 6.60 MPa—more than double the 2.80 MPa of commercial bricks. The average density of the specimens at both temperatures was similar, around 1.58 g/cm³, significantly higher than the 0.95 g/cm³ of commercial counterparts. Moreover, the average thermal conductivity of the geopolymer bricks was 0.008 W/m·K, indicating superior insulating properties compared to the 0.39 W/m·K of commercial refractory bricks. These results demonstrate optimal properties in refractory bricks made from geopolymer-based volcanic ash.

Abstract: The research results on the development of fire-retardant composite cement mortar mixtures on exfoliated vermiculite and volcanic ash with the use of a multifunctional additive are presented D-5. Compositions of fire-retardant composite mortars, which make it possible to significantly improve the physical and mechanical properties of mortar mixtures and mortars, are proposed. Introduction of a multifunctional supplement D-5 in mortar mixtures makes it possible to improve the composite mortar mixtures properties and improve the solution characteristics. Replacement of finely dispersed fraction of exfoliated vermiculite d<0,63 mm volcanic ash by volume in mortar mixtures does not cause a noticeable increase in the solution density, while their strength characteristics increase. The developed composite mortar mixtures meet the requirements of GOST 28013–98 and have a low-cost price due to volcanic ash use.

Abstract: Fiber-gypsum-cement-vermiculite-concrete composites with use of gypsum, Portland cement, volcanic ash, expanded vermiculite and basalt fibers are considered. The results of studies of the compositions and physical and mechanical properties of fiber-gypsum-cement-vermiculite-concrete composites, the dependence of the composite characteristics on the reinforcement with basalt fibers are presented. Graphical interpretations of regression equations for compressive and flexural strength of composites are presented.

Abstract: The studies’ results to determine the gypsum, ash and Portland cement components proportions, which would ensure a decrease in the specific binder consumption, as well as the ash grain composition’s effect on the properties of the gypsum cement pozzolan composite, are presented. It was revealed that the use of volcanic ash together with Portland cement in gypsum concrete composites allows reducing gypsum consumption by up to 50% without a significant decrease in strength characteristics. At the same time, the developed gypsum concrete composites have increased water resistance. The influence of the ash particle size distribution on the strength properties of the composite is ambiguous; in the compositions with a high ash content it is advisable to use larger fractions, and with a content of less than 50% ash in the composite, - the small fractions. To study the parameters’ effect of the dispersed reinforcement with basalt fibers on the properties of a gypsum-cement composite, an experiment with such a second-order composite rotatable plan as regular hexagon was conducted. It was found that the maximum values ​​of optimization parameters are observed in the central area of ​​the plan with and . The compressive strength of a fiber gypsum cement pozzolan composite increases by 1.15-1.18 times, when bending, by 1.56-1.72 times with respect to the strength of the initial matrix.

Abstract: CMAS attack is known to occur owing to the deposition of volcanic ash onto thermal barrier coating (TBC) surface at a high-temperature environment. The serious problem is TBC spallation resulting from the infiltration of molten volcanic ash into the porous microstructure of TBC. The infiltration induces inner stress and phase transformation, which directly results in those serious problems. In this study, the diffusional equation for expressing the infiltrating process of the molten ash into the porous structure of TBC and the associated constitutive equation considered regarding phase transformation are formulated. The equations are installed into commercial finite element (FE) code (MARC) using the user subroutine. The numerical simulation results are compared with the cross-sectional SEM observation for the volcanic-ash-deposited TBC sample exposed at a high-temperature to confirm verification of the model proposed herein.

Abstract: Based on the Volcanology and Geological Hazard Mitigation Center, Mount Sinabung itself is still at hazardous status up until now that can certainly erupt at any time and sprayed a lot of volcanic material which will lead to the abundance of volcanic ash material in the area of Mount Sinabung. How to optimize the volcanic ash waste is what scientists need to think about. In this study, volcanic ash obtained from Mount Sinabung is used as substitution of fine aggregate in the manufacture of concrete brick (paving block). The variations used were 0%, 25%, 50%, and 75% of the starting weight of the fine aggregate used. From the test results, it is obtained optimum compressive strength of 25.2 Mpa and optimum water absorption of 5.998% which means concrete brick (paving block) meets the classification contained in SNI 03-0691-1996.

Abstract: In order to decrease CO₂ level, converting the gas into hydrocarbon fuel gasses has been performed by using photoreduction method under TiO₂/SiO₂ photocatalysis. The silica (SiO₂) for TiO₂/SiO₂ preparation was purified from volcanic ash, that mixed with TiO₂ suspended in water. The photoreduction process of CO₂ was carried out in a batch technique, by exposing CO₂ and water vapor in the presence of TiO₂/SiO₂ photocatalyst with UV lamp for 24 h. The gasses produced from the photoreduction were determined by gas chromatography method. In the research, the effects of HCl and HNO₃ as hydrogen ion supplier were also evaluated. The research results indicate that the photoreduction of CO₂ with the water vapor over the photocatalyst of TiO₂/SiO_{2-volcanic ash} has successfully produced methane and ethylene as fuel gasses, while in the presence of TiO₂ no ethylene was resulted. The methane produced by TiO₂/SiO₂ was observed to be larger than by TiO₂ powder. The content of TiO₂ in TiO₂/SiO₂ with low level strongly influenced the yield of the products. In contrast, the yield was independent on the TiO₂ content in high level. The presence of the acids was found to increase the methane produced , and no ethylene was formed, but instead, methanol was resulted. The effect of HCl was higher than HNO₃.

Abstract: Study on the elemental composition of nanoparticles is of great importance due to their high mobility in the environment and ability to penetrate into human organism. A global aspect is the transport of nutrient and toxic elements with environmental nanoparticles, which can serve as a carrier for these elements. Nanoparticles in complex polydisperse environmental samples such as dust, volcanic ash, or soil may represent only about thousandths or less of bulk sample. Therefore, their recovery followed by quantitative determination of analytes is a difficult task. A novel technique, sedimentation field-flow fractionation in a rotating coiled column, was applied to the fractionation of urban dust and volcanic ash samples with water being used as a carrier fluid. nanoand submicron particles have been separated, weighted, characterized by electronic microscopy and static laser light scattering, and then quantitatively analyzed by ICP-AES and ICP-MS (after digestion). In urban street dust samples, the elements that may be of anthropogenic origin (Zn, Cr, Ni, Cu, Cd, Sn, Pb) were found to concentrate mainly in <0.3 and 0.3-1 μm fractions. It has been shown that the concentrations of Cr, Ni, Zn, Pb, Sn in the finest fraction (<0.3 μm) of street dust can be one order of magnitude higher than the concentrations of elements in bulk sample and coarse fractions. For volcanic ash samples, it has been evaluated that nanoparticles may concentrate potentially toxic elements of volcanic gases. The concentrations of Zn, Cu, Pb, Tl, Bi, Sn, As, Sb in the size fraction <0.2 μm can be two orders of magnitude higher than the concentrations of these elements in bulk sample. Hence, measuring the total concentrations of elements in dust and ash leads to underestimation of the hazard of these samples. The proposed approach to the separation and quantitative analysis of environmental nanoparticles can be a powerful tool for risk assessment related to toxic elements in dust, ash, and other particulate matter.

Abstract: This work presents a study of morphological, structural, and compositional properties of volcanic ash obtained from Nevado del Ruiz volcano in Colombia. The volcanic ash samples were subjected to hydration and annealing processes at atmospheric pressure to obtain zeolite-type natural structures for different applications, like water decontamination and air pollution control. The strong influence of hydration and annealing processes on the formation of zeolite phases was observed. Rietveld refinement was performed with X-ray diffraction (XRD) patterns, obtaining the presence of natural zeolites: gismondine, hydrated calcium aluminosilicate, litosite, clinoplitolite-Na, and phillipsite-K. From scanning electron micrographs, a morphological change of the ash sample was observed with increasing annealing temperature (290 K < T < 673 K). The surface was dominated by the presence of agglomerates or granules around 5 µm in size; other regions with tubular form or flake-type structures were observed with less presence on the surface ash, associated with the formation of the labradorite phase.

Abstract: All thermal power plants including gas turbine (GT) of Tokyo electric company are located along Tokyo bay. If Mt. Fuji is exploded, volcanic ash is fallen down in Kanto area. If volcanic ash is inhaled into GTs, the ash would be firstly impacted and deposited onto thermal barrier coating (TBC) of the blades. Such deposition of the volcanic ash causes the delamination of the ceramic coating. In this study, TBC delamination mechanisms due to the volcanic ash deposition is discussed based upon thermal stress evaluated by a laser monitoring measurement system.