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Self-sensing properties of alkali-activated slag composites under compressive loading
Míková, Maria ; Kusák, Ivo (referee) ; Rovnaník, Pavel (advisor)
Production of construction materials requires a large amount of energy. That can be decreased by using of waste materials. This thesis deals with the self-sensing properties of composites. It presents electrical properties of building materials and their measurement. In the experimental part, the influence of conductive fillers on the self-sensing properties of aluminosilicate composites was examined. Test cubes were made of alkali-activated slag with a content of graphite powder, carbon black, carbon fibers, steel fibers or carbon nanotubes. The fractional change in resistence during cyclic compressive loading was monitored.
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Study of shrinkage reducing admixture efficiency in alkali activated systems
Fojtík, Ondřej ; Koplík, Jan (referee) ; Bílek, Vlastimil (advisor)
Significant drying shrinkage is one of the major issues for the wider application of materials based on alkali-activated slag (AAS). Some shrinkage reducing admixtures (SRA) were developed for the ordinary portland cement systems. A couple of previous studies focused on the efficiency of these SRA in alkali-activated materials. The studies were mainly concentrated on the SRA based on polypropylene glycol. This thesis deals with efficiency of the SRA based on 2 methyl-2,4-pentanediol in AAS pastes and mortars. Influence of the SRA and activator (waterglass) dose on the drying shrinkage and other properties of AAS (flexural and compressive strength, autogenous shrinkage, workability, setting time and microstructure) were investigated. It was found, that at the activator dose when Na2O/slag mass ratio equals 4 or 6 %, SRA causes retardation of hydration, which leads to shrinkage reduction, however strength is reduced significantly, weight lost during the drying is increased and the coarsening of the pore structure occurs. At the activator dose when Na2O/slag mass ratio reaches 8, 10 or 12 %, in the presence of SRA the drying shrinkage is reduced, weight lost during the drying is similar to the reference, strength is increased and microstructure is unchanged against reference. It has been proved that SRA works properly in AAS only at higher activator doses.
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Titanium oxide and its properties in building materials
Rypák, Peter ; Vyšvařil, Martin (referee) ; Rovnaník, Pavel (advisor)
Theoretical part of thesis deals with conclusion of aquired informations about photocatalysis of titanium dioxide, its influence on properties of chosen building materials and its practic use in research of building materials with abitlity to decompose organic and anorganic matters. Experimental part deals with influence of quantity of titanium dioxide on mechanical strength of tested samples based on alkali activated slag and its ability to decompose organic colorant Rhodamine B
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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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Silicate materials with enhanced electrical conductivity
Míková, Maria ; Kusák, Ivo (referee) ; Rovnaník, Pavel (advisor)
This bachelor thesis deals with electrical properties of cement- or aluminosilicate-based materials used in building industry. It presents the summary of the most commonly used functional fillers with ability to increase conduction of the composites and theirs characteristics. Thesis also deals with measured electrical properties and applications of composites with enhanced electrical conductivity. In the experimental part, the influence of graphite powder concentration on the characteristics of alkali activated slag was examined. Electrical, mechanical properties and microstructure was observed. Microstructure was examined by means of mercury porosimetry and scanning elektron microscopy.
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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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Self-sensing properties of alkali-activated slag composites under compressive loading
Míková, Maria ; Kusák, Ivo (referee) ; Rovnaník, Pavel (advisor)
Production of construction materials requires a large amount of energy. That can be decreased by using of waste materials. This thesis deals with the self-sensing properties of composites. It presents electrical properties of building materials and their measurement. In the experimental part, the influence of conductive fillers on the self-sensing properties of aluminosilicate composites was examined. Test cubes were made of alkali-activated slag with a content of graphite powder, carbon black, carbon fibers, steel fibers or carbon nanotubes. The fractional change in resistence during cyclic compressive loading was monitored.
|
|
|
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 shrinkage reducing admixture efficiency in alkali activated systems
Fojtík, Ondřej ; Koplík, Jan (referee) ; Bílek, Vlastimil (advisor)
Significant drying shrinkage is one of the major issues for the wider application of materials based on alkali-activated slag (AAS). Some shrinkage reducing admixtures (SRA) were developed for the ordinary portland cement systems. A couple of previous studies focused on the efficiency of these SRA in alkali-activated materials. The studies were mainly concentrated on the SRA based on polypropylene glycol. This thesis deals with efficiency of the SRA based on 2 methyl-2,4-pentanediol in AAS pastes and mortars. Influence of the SRA and activator (waterglass) dose on the drying shrinkage and other properties of AAS (flexural and compressive strength, autogenous shrinkage, workability, setting time and microstructure) were investigated. It was found, that at the activator dose when Na2O/slag mass ratio equals 4 or 6 %, SRA causes retardation of hydration, which leads to shrinkage reduction, however strength is reduced significantly, weight lost during the drying is increased and the coarsening of the pore structure occurs. At the activator dose when Na2O/slag mass ratio reaches 8, 10 or 12 %, in the presence of SRA the drying shrinkage is reduced, weight lost during the drying is similar to the reference, strength is increased and microstructure is unchanged against reference. It has been proved that SRA works properly in AAS only at higher activator doses.
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