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Utilization of by-pass cement kiln dust in alkali activated materials
Kiripolský, Tomáš ; Beranová, Denisa (referee) ; Kalina, Lukáš (advisor)
By-pass cement kiln dust (CKD) is a fine grained by-product of Portland clinker manufacturing. Its chemical composition is not suitable for the returning back into the feedstock and therefore has to be discharged. Such the increasing waste production contributes to lowering of the environmental impact of cement industry. The possible solution for the ecological processing of CKD is its incorporation into alkali activated blast furnace slag binders. Thanks to the high alkaline content, CKD serves as an effective accelerator for the latent hydraulic substance and at the same time solves the significant shrinkage of alkali activated materials which considerably limiting their practical applications. It was found out that the suitable amount of CKD (20 % replacement of slag) in combination with sodium carbonate increases the compressive strength development of about 10 % and reduces the drying shrinkage (11 % reduction). On the other hand this type of inorganic admixture accelerated the hydration process resulting in rapid loss of workability and shortening the initial setting time. The mechanism of action of CKD in alkali activated matrix has been investigated as well as its optimal dosage in the means of mechanical properties.
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Study of air-entraining admixtures in alkali-activated materials
Kiripolský, Tomáš ; Koplík, Jan (referee) ; Kalina, Lukáš (advisor)
Air entraining admixtures are surfactants, that are commonly used in Portland cement materials, because they form and stabilize small air bubbles distributed in the binder, thereby changing the pore size distribution. The aim of these additives is to increase the durability of the cured binder, especially in climatic conditions, where it must withstand low temperatures, and simultaneously improving the workability in the plastic state. The effect of air entraining admixtures in alkali-activated slag was studied for certain properties. Air entraining admixtures were able to entrain the air in the alkali-activated matrix, they changed the pore size distribution, which resulted in a reduction in capillary pressure in the porous complex, and there was a reduction of shrinkage under autogenous conditions, respectively. The improvement of workability is certainly also positive, but on the other hand there has been a bad effect on flexural strength and compressive strength. The morphology of the air entrained binder was observed by scanning electron microscopy, and simultaneously the effect of air entrained admixtures on hydration was observed by isothermal calorimetry.
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Study of air-entraining admixtures in alkali-activated materials
Kiripolský, Tomáš ; Koplík, Jan (referee) ; Kalina, Lukáš (advisor)
Air entraining admixtures are surfactants, that are commonly used in Portland cement materials, because they form and stabilize small air bubbles distributed in the binder, thereby changing the pore size distribution. The aim of these additives is to increase the durability of the cured binder, especially in climatic conditions, where it must withstand low temperatures, and simultaneously improving the workability in the plastic state. The effect of air entraining admixtures in alkali-activated slag was studied for certain properties. Air entraining admixtures were able to entrain the air in the alkali-activated matrix, they changed the pore size distribution, which resulted in a reduction in capillary pressure in the porous complex, and there was a reduction of shrinkage under autogenous conditions, respectively. The improvement of workability is certainly also positive, but on the other hand there has been a bad effect on flexural strength and compressive strength. The morphology of the air entrained binder was observed by scanning electron microscopy, and simultaneously the effect of air entrained admixtures on hydration was observed by isothermal calorimetry.
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Utilization of by-pass cement kiln dust in alkali activated materials
Kiripolský, Tomáš ; Beranová, Denisa (referee) ; Kalina, Lukáš (advisor)
By-pass cement kiln dust (CKD) is a fine grained by-product of Portland clinker manufacturing. Its chemical composition is not suitable for the returning back into the feedstock and therefore has to be discharged. Such the increasing waste production contributes to lowering of the environmental impact of cement industry. The possible solution for the ecological processing of CKD is its incorporation into alkali activated blast furnace slag binders. Thanks to the high alkaline content, CKD serves as an effective accelerator for the latent hydraulic substance and at the same time solves the significant shrinkage of alkali activated materials which considerably limiting their practical applications. It was found out that the suitable amount of CKD (20 % replacement of slag) in combination with sodium carbonate increases the compressive strength development of about 10 % and reduces the drying shrinkage (11 % reduction). On the other hand this type of inorganic admixture accelerated the hydration process resulting in rapid loss of workability and shortening the initial setting time. The mechanism of action of CKD in alkali activated matrix has been investigated as well as its optimal dosage in the means of mechanical properties.
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