| 1. |
- Ghasemi, Yahya, 1982-, et al.
(författare)
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A theoretical study on optimal packing in mortar and paste
- 2019
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Ingår i: Advances in Cement Research. - 0951-7197 .- 1751-7605.
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Tidskriftsartikel (refereegranskat)abstract
- Packing density of particles is regarded as a key factor affecting workability of cementitious mixtures. While the value can be easily measured, and several models exist for estimating the parameter, no generally accepted definition exist for the optimal packing. Current study aims at exploring the concept of optimal packing in mortars and paste using particle packing and excess water layer theories. A semiempirical method is used for calculating water demand of mixtures based on their specific surface area. The approach allows for estimating optimal packing considering water demand and water to cement ratio of mixtures in addition to packing density.
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| 2. |
- Hökfors, Bodil, 1971-, et al.
(författare)
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On the phase chemistry of Portland cement clinker
- 2015
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Ingår i: Advances in Cement Research. - : Thomas Telford. - 0951-7197 .- 1751-7605. ; 27:1, s. 50-60
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes the formation of a phosphorous belite solid solution and its impact on alite formation. A sub-solidus phase relation for the ternary system silicon dioxide–calcium oxide–phosphorus pentoxide (SiO2–CaO–P2O5) is reported. The ternary system is based on Rietveld refinements of X-ray diffraction patterns from experimental tests. The overall picture is based on known phase diagrams, relevant Rietveld refinements models, stoichiometric relationships as a function of increasing phosphorus pentoxide concentration and vacancy theories for solid solutions of phosphate belites. A tool is developed for predicting the chemistry of the product as well as the chemistry during heating when producing Portland cement clinker. A thermodynamic database for phase chemistry calculations of clinkering reactions has been created and evaluated. Suitable compounds and solution species have been selected from the thermochemical database included in FactSage software. Some solution compositions have been uniquely designed to allow for the proper prediction of the cement clinker chemistry. The calculated results from the developed database for heating raw materials in cement clinker production and cooling of the product are presented in this paper. The calculated results provide a good prediction of the phases and quantities formed during heating and non-equilibrium cooling. The prediction of the amounts of alite, belite and aluminoferrite phases in the product according to the Scheil method is good. The temperature interval for the existence of all of the major phases is relevant. The thermodynamic data for a solution phase of alite with substituting ions of primarily magnesium oxide and phosphorus pentoxide would improve the predictability of the developed database.
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| 3. |
- Hökfors, Bodil, 1971-, et al.
(författare)
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Simulation of oxy-fuel combustion in cement clinker manufacturing
- 2015
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Ingår i: Advances in Cement Research. - Thomas Telford : ICE Publishing. - 0951-7197 .- 1751-7605. ; 27:1, s. 42-49
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Tidskriftsartikel (refereegranskat)abstract
- A thermodynamic process model is used as an evaluation tool. Full oxy-fuel combustion is evaluated for circulation of 20–80% of flue gases to the burn zone of a rotary kiln. The full oxy-fuel combustion simulations exhibit altered temperature profiles for the process. With 60% recirculation of flue gases, the temperature in the burn zone is comparable to the reference temperature, and carbon dioxide concentration in the flue gases increases from 33 to 76%. If water is excluded, carbon dioxide concentration is 90%. The partial oxy-fuel combustion method is evaluated for 20 and 40% recirculation of flue gases from one cyclone string to both calciners. Fuel and oxygen feed to the burning zone and calciners are optimised for the partial oxy-fuel scenario. The lowest specific energy consumption is desired while maximising the amount of carbon dioxide theoretically possible to capture. By introducing partial oxy-fuel combustion with 20% recirculation of flue gases in the carbon dioxide string, total carbon dioxide emissions increases by 4%, with 84% possible to capture. Within the limits of the model, the introduction of full oxy-fuel and partial oxyfuel combustion is possible while maintaining product quality. When simulating partial oxy-fuel combustion, the energy consumption will increase even when no power consumption for the production of oxygen is included.
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| 4. |
- Lui, Gui Qun, et al.
(författare)
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Sintering characteristics of BCSAF cement clinker with added wastes from production of manganese and magnesium metals
- 2017
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Ingår i: Advances in Cement Research. - : Institution of Civil Engineers (ICE). - 0951-7197 .- 1751-7605. ; 29:6, s. 227-235
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Tidskriftsartikel (refereegranskat)abstract
- The production of belite-calcium sulfoaluminate-ferrite (BCSAF) cement with the addition of industrial wastes as feedstock has been studied for many years. The preparation of clinkers is essential in cement production, in which all raw materials react with each other to generate key phases in cement under some specified conditions. The objective of this study was to investigate the sintering characteristics of BCSAF cement clinkers. Four BCSAF clinkers with different compositions were examined. High-temperature microscopy, quantitative x-ray powder diffraction analysis and scanning electron microscopy were used to analyse sintering features and phase composition. The results show that the use of wastes from the production of manganese and magnesium metals, which were added to the raw materials to make clinker pellets, can significantly reduce the firing temperature of BCSAF clinker. The firing temperatures of clinkers with added wastes were below 1300°C, much lower than the temperature used for conventional Portland cement (1450°C). The ferrite phase was always found to inter-grow with the C4A3S¯">C 4 A 3 S ¯ C4A3S¯ phase or C2AS phase, just like the interstitial phase. The ferrite phase acted as a solid solution during cement sintering. A small quantity of iron oxide can make the clinker more porous, leading to energy savings in subsequent grinding processes.
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