Tomáš Melichar - Academia.edu (original) (raw)

Papers by Tomáš Melichar

AIP Conference Proceedings, Dec 31, 2022

DOAJ (DOAJ: Directory of Open Access Journals), Mar 1, 2017

Zenodo (CERN European Organization for Nuclear Research), Jun 4, 2014

In this article our research focused on study of basic physical and mechanical parameters of poly... more In this article our research focused on study of basic physical and mechanical parameters of polymer-cement repair materials is presented. Namely the influence of applied aggregates in combination with active admixture is specially considered. New formulas which were exposed in ambient with temperature even to 1000°C were suggested. Subsequently densities and strength characteristics including their changes were evaluated. Selected samples were analyzed using electron microscope. The positive influence of porous aggregates based on sintered ash was definitely demonstrated. Further it was found than in terms of thermal resistance the effective micro silica amount represents 5% to 7.5% of cement weight.

Advanced Materials Research, Apr 1, 2015

The article presents results and findings of the research focused on the modification of composit... more The article presents results and findings of the research focused on the modification of composition of cement-bonded particle boards with alternative raw materials. The attention was paid either to binder substitution, either to substitution of filling agent. The modification of matrix composition was realized using the blast furnace slag to 30% of cement weight. Fibrous waste from the glass fiber production was applied as a substitution of wooden chips in the mixture. The influence of both mentioned components was examined separately. The emphasis was laid on strength and elastic parameters and also on durability in view of board resistance to frost.

Materiali in tehnologije, 2017

In this article our research focused on study of basic physical and mechanical parameters of poly... more In this article our research focused on study of basic physical and mechanical parameters of polymer-cement repair materials is presented. Namely the influence of applied aggregates in combination with active admixture is specially considered. New formulas which were exposed in ambient with temperature even to 1000°C were suggested. Subsequently densities and strength characteristics including their changes were evaluated. Selected samples were analyzed using electron microscope. The positive influence of porous aggregates based on sintered ash was definitely demonstrated. Further it was found than in terms of thermal resistance the effective micro silica amount represents 5% to 7.5% of cement weight.

Intention of this article is to present research results in area of modification of existing text... more Intention of this article is to present research results in area of modification of existing texture of cement bonded particleboards by secondary product, which is formed during the production of such boards. Considering that mentioned secondary product is not used in any way so far, it is concerned as a waste. It is characterized as relatively fine-grained particular substance, which contains mixture of cement matrix and mineralized chips, whereas these two components can be partially interconnected. First part of the paper shows analysis of alternative raw material itself, as well as proposal of preliminary treatment and dosage into mixture for cement-bonded particleboard production. Further the testing of cement-bonded particleboards of modified composition by above mentioned raw material was done. Examination was carried out with help of setting basic parameters according relevant normative documents (bending strength, density, elastic modulus etc.).

This article presents a study focusing on a detailed analysis of the properties of a by-product f... more This article presents a study focusing on a detailed analysis of the properties of a by-product from the production of cement-bonded particle boards, specifically cuttings. The volume of cuttings increases with the growth of production every year and these cuttings are not used further. Such cuttings represent landfill waste. Considering the composition of these cuttings, their re-use in the further production of particle board appears to be the most suitable option. Therefore, cuttings were subjected to adjustment of composition, size-reduction and separation of grain of defined size. Subsequently, all properties relevant to their possible re-use in production of particle boards were established. Thermic and caloric methods were predominantly used to define the contents of wood matter in relation to the cement matrix. Graininess, mineralogical composition and efficiency indexes, etc. were also studied

IOP Conference Series: Materials Science and Engineering, 2018

Procedia Engineering, 2017

Advanced Materials Research, 2015

Results of an experimental study focused on evaluating the suitability of selected alternative ad... more Results of an experimental study focused on evaluating the suitability of selected alternative additives and their influence on high temperature resistance of repair mortars based on cement are presented in the article. As an alternative substitute, fly ash and blast furnace slag were selected and added in different dosage up to 10% of cement weight not as a substitution component. Aggregates of amphibolite origin were chosen in regard to the thermal resistance to high temperature.

Advanced Materials Research, 2015

The paper analyses the possibility of alkali activated materials utilization as matrix for repair... more The paper analyses the possibility of alkali activated materials utilization as matrix for repair mortars, determined for rehabilitation of reinforced concrete structures, exposed to chemically aggressive surroundings. alcali activated materials have owing to their specific properties a high potential especially for utilization in materials determined for specific applications. Materials showing in comparison with the cement matrix significantly higher resistance against the effect of chemical substances are the so-called alkali activated materials. The rehabilitation of reinforced concrete structures exposed to extreme conditions is the area for effective utilization of the alkali activated extraordinary properties.

Advanced Materials Research, 2015

Experience obtained from often tragic road accidents has proven that in a fire the tunnel lining ... more Experience obtained from often tragic road accidents has proven that in a fire the tunnel lining is destructed very intensively by high temperatures. Concrete, usually applied using the sprayed concrete technology (so-called shotcreting) is used for building the linings of road tunnels. The topic of the present article is the development of a concrete mix determined by the sprayed concrete technology so that this material is to the maximum extent resistant to extreme temperature effects occurred in a fire. It is apparent that using this type of concrete is one of the way of increasing the fire safety of road tunnels.

Advanced Materials Research, 2012

Cement-chip boards are building elements that combine the advantageous properties of wood and cem... more Cement-chip boards are building elements that combine the advantageous properties of wood and cement. It is this synergistic effect which determines the versatile use in the building industry. The boards can be used in any place where the favourable properties of this construction material can fully be appreciated. The disadvantage of the cement-chip boards remains in their relatively high price. Reduction of the price and possible improvement of physical and mechanical properties can be achieved by partial substitution of the raw materials. The basic ingredients of the cement-chip board include the binding material (cement) and filler (wood). The filling material may be partially replaced by secondary raw materials or completely replaced by other herbal sources, such as technical hemp. As the individual components mutually influence each other and, as their effects may not only be added up (additive effect), but also mutually reinforced (synergistic effect), it is not so easy to de...

Advanced Materials Research, 2013

The cement-bonded particle boards can be used among other also with reconstructions of various ty... more The cement-bonded particle boards can be used among other also with reconstructions of various types of buildings as a part of final surface treatment. The paper deals with partial results of the research focused on optimisation of cement-bonded particle board composition with alternative raw materials. Specifically it is analyzing of basic parameters of the waste originating during processing (modification of surface format and quality) of the boards. Upon results and findings a design of new formulas of cement-bonded particle boards is mentioned further, i.e. the composition modified with above stated waste. The outputs presented in the article form an important initial information source in the solved questions. In view of subsequent phases of the research it is a relatively essential and also it can be said a key phase.

Applied Mechanics and Materials, 2013

The intention of the research presented in this article was to study the basic physico-mechanical... more The intention of the research presented in this article was to study the basic physico-mechanical parameters of mineral lightweight renders. Both alternative and primary raw materials were used to modify the filling agent; namely utilized quartz sand, diatomite and hydrophobised perlite. Determining and evaluating the basic parameters of plasters with the modified composition enabled to assess the effect of substituting the filling agent within the particular designed formulas. Emphasis was placed on the parameters in the fresh and hardened conditions of the plasters – workability, water volume, density, compressive and flexural strength. It was found that by appropriately adjusting the water dosage then better parameters could be obtained than in the reference formula – commonly commercially produced renders.

Materiali in tehnologije, 2015

Solid State Phenomena

The article deals with the influence of crystallization additives on the life of self-compacting ... more The article deals with the influence of crystallization additives on the life of self-compacting concrete (so-called SCC concrete), which are exposed to chemically aggressive environments. The focus is not only on the effect of the crystallization additive on the characteristics of the capillary-pore structure of SCC concrete, but especially long life durability of self-compacting concrete (two years expozition). The effect of individual types of aggressive environment is assessed on the basis of a set of physico-mechanical and physico-chemical analyzes.

Solid State Phenomena

This article analyses the effect of crystallization additives on the long-term durability of self... more This article analyses the effect of crystallization additives on the long-term durability of self-compacting concretes (SCCs) in relation to specific types of chemically aggressive environments. The effect of both an inorganic acid solution and the aggressive solutions produced during plant ensilage were tested, while the effect of diesel on these modified concretes was also investigated. Attention was given to the effect of crystallization additives on the characteristically capillary porous structures of self-compacting concrete, specifically in terms of the long-term durability of SCCs in relation to the above-stated chemically aggressive solutions. The effect of aggressive environments was evaluated through a set of physical-mechanical trials and physical-chemical analyses.

AIP Conference Proceedings, Dec 31, 2022

DOAJ (DOAJ: Directory of Open Access Journals), Mar 1, 2017

Zenodo (CERN European Organization for Nuclear Research), Jun 4, 2014

In this article our research focused on study of basic physical and mechanical parameters of poly... more In this article our research focused on study of basic physical and mechanical parameters of polymer-cement repair materials is presented. Namely the influence of applied aggregates in combination with active admixture is specially considered. New formulas which were exposed in ambient with temperature even to 1000°C were suggested. Subsequently densities and strength characteristics including their changes were evaluated. Selected samples were analyzed using electron microscope. The positive influence of porous aggregates based on sintered ash was definitely demonstrated. Further it was found than in terms of thermal resistance the effective micro silica amount represents 5% to 7.5% of cement weight.

Advanced Materials Research, Apr 1, 2015

The article presents results and findings of the research focused on the modification of composit... more The article presents results and findings of the research focused on the modification of composition of cement-bonded particle boards with alternative raw materials. The attention was paid either to binder substitution, either to substitution of filling agent. The modification of matrix composition was realized using the blast furnace slag to 30% of cement weight. Fibrous waste from the glass fiber production was applied as a substitution of wooden chips in the mixture. The influence of both mentioned components was examined separately. The emphasis was laid on strength and elastic parameters and also on durability in view of board resistance to frost.

Materiali in tehnologije, 2017

In this article our research focused on study of basic physical and mechanical parameters of poly... more In this article our research focused on study of basic physical and mechanical parameters of polymer-cement repair materials is presented. Namely the influence of applied aggregates in combination with active admixture is specially considered. New formulas which were exposed in ambient with temperature even to 1000°C were suggested. Subsequently densities and strength characteristics including their changes were evaluated. Selected samples were analyzed using electron microscope. The positive influence of porous aggregates based on sintered ash was definitely demonstrated. Further it was found than in terms of thermal resistance the effective micro silica amount represents 5% to 7.5% of cement weight.

Intention of this article is to present research results in area of modification of existing text... more Intention of this article is to present research results in area of modification of existing texture of cement bonded particleboards by secondary product, which is formed during the production of such boards. Considering that mentioned secondary product is not used in any way so far, it is concerned as a waste. It is characterized as relatively fine-grained particular substance, which contains mixture of cement matrix and mineralized chips, whereas these two components can be partially interconnected. First part of the paper shows analysis of alternative raw material itself, as well as proposal of preliminary treatment and dosage into mixture for cement-bonded particleboard production. Further the testing of cement-bonded particleboards of modified composition by above mentioned raw material was done. Examination was carried out with help of setting basic parameters according relevant normative documents (bending strength, density, elastic modulus etc.).

This article presents a study focusing on a detailed analysis of the properties of a by-product f... more This article presents a study focusing on a detailed analysis of the properties of a by-product from the production of cement-bonded particle boards, specifically cuttings. The volume of cuttings increases with the growth of production every year and these cuttings are not used further. Such cuttings represent landfill waste. Considering the composition of these cuttings, their re-use in the further production of particle board appears to be the most suitable option. Therefore, cuttings were subjected to adjustment of composition, size-reduction and separation of grain of defined size. Subsequently, all properties relevant to their possible re-use in production of particle boards were established. Thermic and caloric methods were predominantly used to define the contents of wood matter in relation to the cement matrix. Graininess, mineralogical composition and efficiency indexes, etc. were also studied

IOP Conference Series: Materials Science and Engineering, 2018

Procedia Engineering, 2017

Advanced Materials Research, 2015

Results of an experimental study focused on evaluating the suitability of selected alternative ad... more Results of an experimental study focused on evaluating the suitability of selected alternative additives and their influence on high temperature resistance of repair mortars based on cement are presented in the article. As an alternative substitute, fly ash and blast furnace slag were selected and added in different dosage up to 10% of cement weight not as a substitution component. Aggregates of amphibolite origin were chosen in regard to the thermal resistance to high temperature.

Advanced Materials Research, 2015

The paper analyses the possibility of alkali activated materials utilization as matrix for repair... more The paper analyses the possibility of alkali activated materials utilization as matrix for repair mortars, determined for rehabilitation of reinforced concrete structures, exposed to chemically aggressive surroundings. alcali activated materials have owing to their specific properties a high potential especially for utilization in materials determined for specific applications. Materials showing in comparison with the cement matrix significantly higher resistance against the effect of chemical substances are the so-called alkali activated materials. The rehabilitation of reinforced concrete structures exposed to extreme conditions is the area for effective utilization of the alkali activated extraordinary properties.

Advanced Materials Research, 2015

Experience obtained from often tragic road accidents has proven that in a fire the tunnel lining ... more Experience obtained from often tragic road accidents has proven that in a fire the tunnel lining is destructed very intensively by high temperatures. Concrete, usually applied using the sprayed concrete technology (so-called shotcreting) is used for building the linings of road tunnels. The topic of the present article is the development of a concrete mix determined by the sprayed concrete technology so that this material is to the maximum extent resistant to extreme temperature effects occurred in a fire. It is apparent that using this type of concrete is one of the way of increasing the fire safety of road tunnels.

Advanced Materials Research, 2012

Cement-chip boards are building elements that combine the advantageous properties of wood and cem... more Cement-chip boards are building elements that combine the advantageous properties of wood and cement. It is this synergistic effect which determines the versatile use in the building industry. The boards can be used in any place where the favourable properties of this construction material can fully be appreciated. The disadvantage of the cement-chip boards remains in their relatively high price. Reduction of the price and possible improvement of physical and mechanical properties can be achieved by partial substitution of the raw materials. The basic ingredients of the cement-chip board include the binding material (cement) and filler (wood). The filling material may be partially replaced by secondary raw materials or completely replaced by other herbal sources, such as technical hemp. As the individual components mutually influence each other and, as their effects may not only be added up (additive effect), but also mutually reinforced (synergistic effect), it is not so easy to de...

Advanced Materials Research, 2013

The cement-bonded particle boards can be used among other also with reconstructions of various ty... more The cement-bonded particle boards can be used among other also with reconstructions of various types of buildings as a part of final surface treatment. The paper deals with partial results of the research focused on optimisation of cement-bonded particle board composition with alternative raw materials. Specifically it is analyzing of basic parameters of the waste originating during processing (modification of surface format and quality) of the boards. Upon results and findings a design of new formulas of cement-bonded particle boards is mentioned further, i.e. the composition modified with above stated waste. The outputs presented in the article form an important initial information source in the solved questions. In view of subsequent phases of the research it is a relatively essential and also it can be said a key phase.

Applied Mechanics and Materials, 2013

The intention of the research presented in this article was to study the basic physico-mechanical... more The intention of the research presented in this article was to study the basic physico-mechanical parameters of mineral lightweight renders. Both alternative and primary raw materials were used to modify the filling agent; namely utilized quartz sand, diatomite and hydrophobised perlite. Determining and evaluating the basic parameters of plasters with the modified composition enabled to assess the effect of substituting the filling agent within the particular designed formulas. Emphasis was placed on the parameters in the fresh and hardened conditions of the plasters – workability, water volume, density, compressive and flexural strength. It was found that by appropriately adjusting the water dosage then better parameters could be obtained than in the reference formula – commonly commercially produced renders.

Materiali in tehnologije, 2015

Solid State Phenomena

The article deals with the influence of crystallization additives on the life of self-compacting ... more The article deals with the influence of crystallization additives on the life of self-compacting concrete (so-called SCC concrete), which are exposed to chemically aggressive environments. The focus is not only on the effect of the crystallization additive on the characteristics of the capillary-pore structure of SCC concrete, but especially long life durability of self-compacting concrete (two years expozition). The effect of individual types of aggressive environment is assessed on the basis of a set of physico-mechanical and physico-chemical analyzes.

Solid State Phenomena

This article analyses the effect of crystallization additives on the long-term durability of self... more This article analyses the effect of crystallization additives on the long-term durability of self-compacting concretes (SCCs) in relation to specific types of chemically aggressive environments. The effect of both an inorganic acid solution and the aggressive solutions produced during plant ensilage were tested, while the effect of diesel on these modified concretes was also investigated. Attention was given to the effect of crystallization additives on the characteristically capillary porous structures of self-compacting concrete, specifically in terms of the long-term durability of SCCs in relation to the above-stated chemically aggressive solutions. The effect of aggressive environments was evaluated through a set of physical-mechanical trials and physical-chemical analyses.