Papers by Keyword: Artificial Aggregate

Abstract: This study was conducted as a part of a research to assess the influence of the volumetric properties of geopolymer artificial aggregates made of fly ash to the performance of asphalt mixture to be used in pavement layers. This paper presents the parameters adopted during the production of geopolymer artificial aggregates which may affect the volumetric properties and the structure of the aggregates. The investigated volumetric properties included specific gravity and water absorption. In the experiment laboratory, two variables were utilized for producing the artificial aggregates, which might affect the considered volumetric properties. Those variables are pan-granulator slopes and alkaline ratios (the ratios of Sodium Silicate to Sodium Hydroxide). The pan-granulator slopes were set at 3 different angles, i.e. 45^o, 50^o, and 55^o. The selected alkaline ratios were 1.5, 2.0, 2.5, and 3.0. The test results indicated that the best volumetric properties were obtained at a slope of 50^o and alkaline ratio of 2.5. The bulk specific gravity values at the best volumetric properties were found to be: 1) oven dry at 1.9 grams/cm³; 2) saturated surface dry (SSD) at 2.0 grams/cm³, and 3) apparent at 2.1 grams/cm³ with 6% water absorption. In addition, the interfacial transition zone and microstructure aggregates were examined by using Scanning Electron Microscope (SEM). In this study, it was found that there were effects of Na₂SiO₃/ NaOH ratios and the granulation method on the volumetric properties.

Abstract: Main object of this paper are results of ash usage in order to create artificial aggregates. Ashes are mineral residue of coal burning in thermal power stations. Fly ashes (high temperature ashes) are highly used in practice as supplement of cement and silicate components of silica materials. FBC ashes are not used such great scale. They can be used for restoration, mounds or for example also for production of ash autoclaved aerated concrete. [1] Production of artificial aggregate from sintered ash is possible mainly because of the fly ashes. [2] Focus of this paper is to compare various types of ashes for lightweight aggregate produced with cold-bonding. Apart from the fly ashes and FBC ashes are also tested bottom ashes from FBC technology. From the results could be assumed, that bottom ashes compared to their granularity could be used only very hardly. Fly ashes splendidly react with cement and reach higher strengths. But they need more than 10 % of binder in order to reach quality results. FBC ashes better cooperate with quicklime, but in order to reach suitable parameters they need smaller portion of binder.

Abstract: Combustion of coal creates a high amount of by-products in heat power plants. The largest share occupies fly ash as solid mineral residuals. Global pressure grows currently for the use of energy by-products. Utilization as a raw material for production of artificial sintered aggregate is one of the ways to make optimal use of even low-quality fly ash. Environmental and economic reasons lead currently to trying to upgrade the technology, which will fully use of the principle of self-sintering process based on content of combustible substances.The amount of combustible substances is today increasing by coal as a primary and finite resource. There is also best way for utilization of industrial wastes that contain a suitable share of combustible substances for ensure the smooth running of sintering.The paper deals with laboratory verification of selected industrial wastes as a correction component in the sintered aggregate production technology. As an alternative raw materials were selected coal tailings, sludge from paper industry, sludge from waste water treatment plant and fly ash from municipal waste incineration plant. The aim of the study was to investigate the effect of corrective components to the quality of the resulting sintered aggregates.

Abstract: In a world is of ever-increasing pressure on the use of fly ash in building materials. Despite these efforts the majority of produced energy by-products end up as reclamation material and only small part as high-quality materials. Technology of sintered artificial aggregate is fully based on the fly ashes and allows processing a high percentage of this raw material. The work is devoted to assessing the impact of fly ash character on the quality artificial aggregate. There were selected three fly ashes from high-temperature combustion technology and two from the FBC combustion. The results clearly show that the FBC ashes are not too useful for sintered aggregate technology. For fly ashes is determined primarily by their fineness and the amount of amorphous silica phase.

Abstract: Nowadays, over 95 % of fly ash is used as construction products in the Czech Republic. However, around 80 % of fly ash is used for renovation of open-pit quarries and areas affected by human activity. Production of artificial aggregate is the way to use over 90 % of energy by-products in the building material industry. It is necessary to find appropriate combination of parameters of input materials and conditions of production to get optimal properties of aggregate. The paper gives an account of the influence of parameters of fly ash and conditions of firing on the quality of ceramic body made from fly ash. Temperatures of 1050 °C, 1150 °C and 1200 °C were examined. The research focused on the structure of the ceramic body as well as its physico-mechanical parameters.

Abstract: This study was conducted to compare the mechanical properties of fly ash artificial geopolymer aggregates with natural aggregate (rock) in term of its impact strength, specific gravity and water absorption.The raw materials used were fly ash, sodium hydroxide, sodium silicate and natural aggregate. After the artificial geopolymer aggregate has been produced, its water absorption, specific gravity and aggregate impact test has been done. All results obtained were compared to natural aggregate. The result shows that the fly ash geopolymer aggregate are lighter than natural aggregate in term of its specific gravity. The impact value for fly ash artificial geopolymer aggregate slightly high compared to natural aggregate while it has high water absorption value compared to natural aggregate. As conclusion, the fly ash artificial geopolymer aggregate can be used as one of the construction materials in concrete as an alternative for coarse aggregate besides natural aggregate with more lightweight properties.

Abstract: At present high temperature fly ashes are already quite widely used as a secondary raw material in building materials. Fly ashes are usually able to fully replace classical materials. FBC ashes also gradually finding their place for example in production of autoclaved aerated concrete, in binders or solidification of hazardous waste. However, the coarser types of energy by-products are relatively difficult to use. Therefore, this part of the work focused on the study of usability of bottom ashes for artificial sintered aggregates. The article will focus on results of laboratory firing in muffle furnace, dedicated to testing of maximum bottom ash content in the mixture with the fly ash and special type of clay.

Abstract: Production of artificial aggregate by clinkering process is currently relatively well-known way to efficiently use the potential of fly ash for building materials. Principle of clinkering can reduce the cost of natural gas and other potential external sources of heat through the use of own combustible substances. Course of firing and aggregate properties significantly depend on the type and character of the fly ash or fly ash mixture. Due to the high heterogeneity of these materials is relatively difficult to assess the impact of specific parameters (grain size, the content of Fe₂O₃, SiO₂, CaO, amorphous phase, etc.). Due to the experimental testing of a large number of different types of fly ash and their mixtures, it will possible to verify at least some principles based on experience with the production of ceramic body. This article discusses the results of the sub-tests, dealt with influence of physico-mechanical properties, chemical and mineralogical composition of fly ash on the quality of the resulting ash body.

Abstract: Production of artificial aggregates is one of the suitable ways how to use the maximum ratio of fly ash in construction materials. Subsequent use of aggregates is directed in addition to various embankments, filter layers and also for lightweight concrete. Concrete can be used wherever required low weight while maintaining the necessary strength. The contribution is geared to verify the applicability of newly produced artificial aggregates from different types of fly ash for standard concrete.

Abstract: Fly ash is currently secondary raw material, which is produced in huge quantities and its applicability is still not optimal. Even though it is used in cement, concrete, mortars, aerated concrete, ceramics, etc., it is still used, more than 80 % of it, for the reclamation of industrial areas and open cast mines. The production of artificial aggregate by clinkering fly ash utilizes at least 90 % of fly ash in the mixture and it is, together with aerated concrete, one of the ways to make the most of the potential of this raw material. This article deals with the description of the nature of individual fly ash types produced in the Czech Republic and the study of its influence on the behaviour during the thermal process. Chemical composition is the decisive parameter; it indicates the ratio of silicon, iron and aluminium oxides, and thus affects the melting point of the entire complex. This article points out the differences among the various fly ash types and it directly shows, using a picture-analysis, the changes in a sample cross-section during annealing.