Dana Koňáková

• Doctor of Engineering
• Scientific worker at Czech Technical University in Prague

Commercially available conductive filaments are not designed for electrochemical applications, resulting in 3D printed electrodes with poor electrochemical behavior, restricting their implementation in energy and sensing technologies. The proper selection of an activation method can unlock their use in advanced applications. In this work, rectangul...

In this study, we explored and described various parameters of microbially induced calcite precipitation (MICP) using the alkaliphilic bacterium Sporosarcina pasteurii DSM 33, which exhibits ureolytic activity, to stabilize and strengthen waste concrete fines (WCF). Bacterial cell concentration, single and repeated addition of bacterial suspension,...

Calcined clays have become one of the most researched themes in the field of cement replacement in recent years. However, it is not only pure kaolinite that can be used for thermal activation. There are other options such as the use of lower-grade clays. The brick soils can be considered as a representative of these lower-grade clays. The studied s...

One of possible application fields of Alkali activated aluminosilicates (AAA) lies in their higher thermal stability compared to Portland cement based systems. AAA may be thermally loaded just moderately (e.g. thermal insulating foams) or more intensively (refractory AAA concrete; ceramics derived from AAA). Thermal loading is obviously causing num...

In this study, we explored the potential of microbiologically induced calcite precipitation (MICP) for enhancing the microstructural integrity of waste concrete fines (WCF). Traditionally, ureolytic bacteria, such as Sporosarcina pasteurii, have been widely used in MICP due to their ability to produce calcium carbonate via urea hydrolysis, but this...

Thermally activated clays (TACs) have been identified as possible supplementary cementitious materials (SCMs). To find a suitable clay and to optimise the activation process, it is necessary to determine its pozzolanic activity. However, the nature of clays is different from that of conventional SCMs. Therefore, the results of commonly used methods...

Acid (usually by phosphoric acid) activation of aluminosilicate precursors provides a new group of inorganic materials with promising chemical and thermal stability. The three mixtures in system metakaolin – phosphoric acid were prepared; they differed in Al/P molar ratio (1, 1.5, 2). Compressive and bending strength were determined in the age of 1...

Nowadays, there are more and more attempts to replace cement with some kind of suitable pozzolana. Thermally activated clays have become the favoured materials in this field. However, the investigated clays are generally pure kaolinite or kaolinitic clays. This article is aimed at the possibility of thermal activation of brick soils, more specifica...

The paper deals with analyzes of Isothermal Conduction Calorimetry response obtained during the alkaline activation of four types of precursors (metakaolin, slag and two kinds of waste ceramic powders) to geopolymers. The first two precursors are traditionally used, while the latter two are emerging materials and knowledge of their alkaline activat...

The possibility to valorise biomass combustion ash in air lime based plaster was evaluated by means of mechanical properties. The possible effect of vegetable fibres (hemp, flax) was examined as well. The biomass ash improved significantly the mechanical properties of plaster. On the other hand, the vegetable fibres are limiting the compressive str...

With the scarcity of raw materials, energy intensiveness and environmental burden connected with producing Portland cement, there is a growing need to find substitute binders. Thermally activated clay also appears to be a suitable material for partial cement replacement. However, not all clays are the same. It depends very much on the place of coll...

The thermally activated clay minerals are well-known as perspective supplementary cementing materials (SCMs) able to reduce the Portland clinker consumption and thus also the related CO 2 emissions. The best SCM performance among clay minerals is provided by thermally activated kaolin (metakaolin). Nevertheless, kaolinitic clays are not available e...

Restoration of historical buildings requires an application of suitable and convenient materials which are compatible with historical legacy. On the other hand, the used materials have to show adequate durability and fulfil current tendencies of environmental-friendliness policy. Most historical buildings have their facades made of lime-based, or m...

The main purpose of the research was to evaluate the abrasion resistance of a composite material made from a combination of flax fiber and bio-based epoxy resin. In the second group of samples, bio-epoxy was enriched with corundum additive. Composite material samples were produced using vacuum infusion technology. A Taber Abraser rotary abrasion ma...

This research examines vanadium‐deficient V2C MXene, a two‐dimensional (2D) vanadium carbide with exceptional electrochemical properties for rechargeable zinc‐ion batteries. Through a meticulous etching process, a V‐deficient, porous architecture with an expansive surface area is achieved, fostering three‐dimensional (3D) diffusion channels and boo...

This study investigates the potential of microbially-induced calcite precipitation (MICP) in converting waste concrete fines (WCF), an underutilized byproduct generated during the crushing of old concrete, into construction material. WCF samples treated with Sporosarcina pasteurii DSM 33 for periods ranging from 14 to 90 days exhibited up to an 11%...

This article deals with the possibility of thermal activation of bentonitic clays. Specifically, the impact of temperature on the overall performance of two varying thermally activated bentonitic clays was investigated and compared with conventional kaolinitic clay. Firstly, the raw materials were characterized; their phase composition, granulometr...

Nowadays, metakaolin is currently widely used as a supplementary cementitious material in the concrete industry. However, there are significant differences between kaolinitic clays, which can be used for the production of metakaolin. They can vary in the granulometry as well in the mineralogical composition (more precisely the content of varying im...

In this study, three industrial by-products (ultrafine fly ash, ground granulated blast-furnace slag (ggbs) and circulating fluidized bed co-fired fly ash) were used to produce ternary cementless composites without using alkali activators. The finenesses of ultrafine fly ash, ggbs and co-fired fly ash were 33,800, 5830 and 5130 cm 2 /g, respectivel...

Cement-based composites have a very broad field of applications but their composition has to be designed with care to meet the desired functional properties. High-temperature resistant mixtures can be stated as a characteristic example in that respect. The standard calcium silicate binder should be replaced usually by high alumina cements which can...

Nowadays it is almost impossible to design a cement-based mixture without the application of some plasticizing additives. There have been developed many types of plasticizers, but they are mostly directed for Portland cement applications. In the case of calcium aluminate cement (CAC), they are also widely employed, but their impact has not been pro...

The building industry produces brick waste, which is not using efficiently enough. Instead of looking for the use of such waste materials, we draw on non-renewable resources, burden the environment, and all this is very expensive. This work focuses on the recycling of such waste, specifically on the ceramic powder generated in the production of bri...

Supplementary cementitious materials (SCMs) are widely used with Portland cement. Similar approach was applied for calcium aluminium cement in this paper. Potential SCMs were ceramic powder, calcined shale and sintered mullite. Cement pastes with 5% or 15% of SCM were prepared and their phase compositions and basic physical and mechanical propertie...

Cement composites are often employed in severe conditions. They might be exposed for instance to high temperatures and/or high mechanical loads. However, their properties are mostly measured in laboratory conditions only, so that designers cannot take into account the changes in their material parameters after loading. In this paper, basic physical...

Current tendencies in the field of waste management are influenced by environmental issues, putting among others an emphasis on waste reuse rather than landfilling. By-products of brick industry represent a typical example of a material with a great potential to be further processed to contribute to the environmental protection efforts. Due to its...

The influence of metakaolin (MK) additive in ordinary Portland cement (OPC) paste to its pH was studied by direct pore solution pH measurement and by XRD and thermal analysis. This research program was motivated by importance of pH for reinforcement corrosion; while the steel demands the high pH for its corrosion protection, the basalt-based reinfo...

In the case of Portland cement (PC) and ordinary concrete, supplementary cementitious materials (SCM) have been successfully employed for decades. Despite that calcium aluminate cement (CAC) shows somehow different performance (composition, properties, stability, durability, etc.) the idea of SCM could be useful also in the case of this primarily r...

The alkaline activation of aluminosilicates represents an alternative to cement based materials, which has many benefits, the environmental in particular. The mix design is though, as compared with the concrete mixtures, still less advanced as different principles are to be applied. Empirical approaches, that are usually employed, can exploit desig...

The effect of high-temperature exposure on the behaviour of fiber reinforced composites based on Portland cement is studied. Three reinforced composites with the amount of fibers from 0.5 to 1.5 % and one reference without fibers were prepared. Their basic and mechanical properties were measured and studied. The application of aluminosilicates fibe...

The objective of the research is to investigate the mechanical properties of the newly designed lightweight cement-based refractory composite before and after high-thermal loading. To produce convenient refractory material was chosen binder system based on aluminous cement. Lightweight composite/concrete (LWC) is an effective and easy way to deduce...

Alkaline activation is a globally expanding, innovative technology that involves the chemical reaction between an aluminosilicate precursor and an alkaline activator which results in a very compact and well-connected structure. The alkali activated aluminosilicates (AAA) are usually prepared with the utilization of industrial waste, and therefore,...

Basic physical and mechanical properties of several cement composites are determined as functions of thermal load and the results are compared with reference materials. Bulk density, matrix density, and open porosity are measured using the water vacuum saturation method. Compressive and bending strengths are determined according to the European sta...

As nuclear energy is increasingly utilized, a radioactive waste management becomes more and more important issue to be addressed. The radioactive waste is currently stored in special repositories, whose construction brings new challenges for civil and material engineering. In this article, a new type of concrete, with improved sorption properties,...

Concrete is a suitable material for secondary casings in multi-barrier systems used in radioactive waste repositories, because it is durable and radiation- and thermal resistant and it has good mechanical properties. The casings should also limit possible leaching of radionuclides in case of failure of inner barriers. An efficient way to tackle thi...

Many practical applications of concrete require adjustment of its properties. If concrete is used as casing for radioactive waste deposits, its main purpose is to mitigate radionuclide release and the mix design must conform to this requirement. In this article bentonite as a material with great sorption capacity is used as a concrete component. Th...

Concrete casing for radioactive repositories have to meet many strict requirements. One of the most important is a radiation protection and a radionuclide inhabitation. Bentonite, with a great sorption capacity, seems to be a suitable material for this purpose. Therefore, the main aim of this study was to assess an impact of the bentonite utilizati...

This article is focused on modern plasters with improved thermal insulating ability. Studied plasters composed of expanded perlite and silica sand. Regarding the matrix, three kind of binder was used. Lime was partially replaced by ceramic powder. This waste material shows good pozzolanic reactivity and thus bring economic and ecological benefits....

This article is focused on modern plasters with improved thermal insulating ability. The studied plasters were composed of lime, cement, ceramic powder, expanded perlite and silica sand. Regarding the matrix, three kinds of binders were used. Lime was partially replaced by ceramic powder. These waste materials show good pozzolanic reactivity and th...

Several alkali activated aluminosilicate (AAA) materials prepared using waste brick powder as precursor are analyzed from both functional and environmental points of view. The functional properties in hardened state are assessed by the measurement of basic physical properties and mechanical parameters. The environmental impacts are examined by dete...

The effect of external environment on heat and moisture transport and storage properties of the traditional fired clay brick, sand–lime brick and highly perforated ceramic block commonly used in the Czech Republic and on their hygrothermal performance in building envelopes is analyzed by a combination of experimental and computational techniques. T...

Several high-strength concrete mixes containing ternary binders composed of Portland cement, silica fume, and waste brick powder are designed. Taking into account the functional properties of hardened mixes, together with their supposed environmental qualities and economic benefits, the practical limits of pozzolan content in the binder are analyze...

Most supplementary cementitious materials (SCM) have been only rarely used in high performance concrete (HPC) design to date, silica fume being one of the very few exceptions in that respect. The content of many SCMs in blended cements was also often low because at higher dosage they were not capable to replace Portland cement effectively. Their en...

The effect of high temperature exposure on the durability of fiber-reinforced composite materials based on high alumina cement is studied. A combination of X-ray diffraction- and thermal analyses of hydrated phases shows a simultaneous presence of all principal hydrates (CAH10, C2AH8, C3AH6, AH3) in significant amounts during the whole 2–28 days hy...

New kind of plasters with improved thermal insulating ability are presented in this article. Improvement was reached by utilization of lightweight expanded perlite with high porosity. The second used aggregate was silica sand. Regarding the binder, three kind were combined for the reason of better plaster performance. Pure lime, Portland cement and...

Plasters containing lightweight aggregates are mostly characteristic by low bulk density and low thermal conductivity but these favorable properties are often achieved at the expense of mechanical strength. In this paper, lightweight lime-based plasters are designed which have good thermal and mechanical properties at the same time. As their suppos...

The article compares different types of aluminate cements with the reference Portland cement, used in refractory composites. The rate of influence of elevated temperatures (400 °C and 1000 °C) is studied. The investigated parameters are basic physical characteristics and mechanical properties. Results show the best behaviour of the mixture containi...

The paper is dealing with an influence of fine pozzolanic admixture supplementing a part of cement on various properties of high-strength concrete. The measured characteristics were basic physical properties, compressive strength and thermal properties (thermal conductivity and specific heat capacity). Replacing the cement by the natural pozzolana...

Knowledge of materials behavior under heat treatment is of high importance in construction and safety engineering; tunnels represent a special field because of their specific safety issues. In the case of fire, tunnel structure and surrounding rock are subjected to extreme temperatures which induces irreversible changes in the material’s microstruc...

The experimental analysis of several types of fine-grained high performance concretes is presented in this paper. Besides mechanical parameters, presented analysis aims also at determination of basic physical and heat and moisture transport and storage parameters. Within the frame of this paper, three different mixtures of fine-grained high perform...

Three renders commonly used in the Czech Republic on the exterior side of building envelopes are exposed for 2 years to the environmental conditions of the city of Prague. The effect of external environment on their possible damage is monitored using the measurement of a variety of material properties in selected time intervals. The experimental re...

There are more than seven billion people currently living on the Earth and the demands of population are rising. Lime and cement are parts of most building materials, so their global consumption grows. Therefore, it is necessary to think both economically and ecologically, and search for a suitable alternatives and replacements. This study is aimed...

The thermal conductivity and specific heat capacity of characteristic types of porous building materials are determined in the whole range of moisture content from dry to fully water-saturated state. A transient pulse technique is used in the experiments, in order to avoid the influence of moisture transport on measured data. The investigated speci...

The heat and moisture transport and storage parameters of three different natural stones used on the Czech territory since medieval times are determined experimentally, together with the basic physical properties and mechanical parameters. The measured data are applied as input parameters in the computational modeling of hygrothermal performance of...

This article deals with the comparison of two different renovation plasters produced by different companies in the Czech Republic. The selected stuccos were Feinputz 212 supplied by HASIT Šumavské vápenice a omítkárny s.r.o and Kbelosan F from Knauf Praha spol. s.r.o. They were studied in the means of basic physical properties, mechanical propertie...

In this paper, the properties of plasters based on lime – brick powder binder of varying composition (ceramics content from 0 to 80 %) are studied. The plasters are prepared with a constant water amount. The pore size distribution is thus influenced in a positive way; the total porosity increases with the ceramics content but the volume of capillar...

A potential application of waste ceramic dust as cement replacement in lime-cement plasters is studied using both experimental and computational approaches. A comprehensive experimental analysis of the material properties of lime-cement plaster and three lime-pozzolan plasters containing different amounts of waste ceramics is performed at first. Th...

The paper is dealing with selected parameters of four marbles with respect to their utilization as building materials. Stones from four function quarries in the Czech Republic were chosen and scopes of physical properties were determined. Basic physical, mechanical and thermal properties belong among studied characteristics. Bulk density of studied...

Brick have been used for thousands years and during that time they went throw the long development. One of the possibilities how to changed properties of ceramic products is to change material compositions. This article is focused on utilization of lightening additives. Commonly used sawdust is compared with straw. The matter of measurement was to...

This article is focused on cement based composites. Two cements differing in mineralogical composition are utilised as main binder in composites mixtures. Results of measured physical parameters of studied materials are presented. For the sake of comparison, a reference material with Portland cement was also prepared. Basic physical properties (mea...

This article deals with concrete containing waste material originating in a coir fibres extraction from outer protective peel of a coconut. Coir pith is used as cement replacement in amount of 5% and 10%. The influence of moisture content on the thermal properties of studied concrete is determined by means of experimental measurements of basic phys...

The water vapour transport and the liquid water transport of high performance concrete (HPC) with the content of natural pozzolana are the described in this paper. Studied properties are presented by means of water vapour diffusion coefficient, water vapour diffusion resistance factor and absorption coefficient respectively. The natural pozzolana (...

The article compares the basic physical, mechanical and both liquid water and water vapour transport properties of self-compacting concrete containing different pozzolanic admixtures. Limestone, fly ash and metakaolin were used. A concrete mixture without any pozzolana was also manufactured as a reference. The best values of studied properties were...

This article is focused on thermal expansion of cement-based composite. Studied materials are concrete containing alumina cement, silica aggregates and they are reinforced by basalt fibres. Three different concrete varying in fibres length were prepared and its basic physical properties and thermal expansion were measured. Fibres lengths were 6mm a...

The term sandstone is used for wide range of rocks containing quartz clasts which can be cemented by secondary precipitated quartz or calcite; moreover the space between clasts can be filled by matrix. These facts result in existence of numerous rocks having highly various properties. Sandstones have been used as construction materials due to their...

Concrete structures can sometimes be exposed to the extreme conditions during their lifetime. A fire or, more generally, exposure to high temperatures presents a typical example when a damage to building materials is likely to occur, which can lead eventually to a collapse of the whole structure. In this paper, high-temperature resistance of concre...

The effect of external environment on the aging process of commercially used lime-cement plasters is studied. Three different kinds of plasters are tested at three different ages, namely in the reference state after 28 days of standard curing and after one and two years of exposure to the environmental conditions of Central Europe. The basic physic...

The presented paper deals with utilization of raw and treated coir pith as potential component of cementitious composites. The studied material is coir pith originating from a coconut production. Its applicability as cement mixture component was assessed in terms of the physical properties of concrete containing different amount of coir pith. Basic...

Basic physical properties, pore structure, hygric properties and frost resistance concrete containing supplementary cementing materials. The amount of SCMs was kept constant to replace 10% of cement. Experimental results show that bulk density and matrix density of studied material vary only slightly except the mixture with fine natural pozzolana w...

Pozzolanic materials and their usage in concrete production are nowadays widely spread. Their application as additives is inherent especially for the purpose of high strength concrete. This article deals with evaluation and comparison of the influence of two different supplementary cementitious materials on the properties of high strength concrete:...

The rate of transport of liquids in porous environment is crucial engineering problem. It has importance in many fields like chemical engineering, hydropedology, economic geology and also in building materials science. The intensity of a liquid transport in porous body can be analyzed be means of three concepts – sorptivity, permeability and diffus...

In this article selected properties of a glass and polypropylene fibre reinforced cement composite materials are studied. They are determined either after preceding thermal treatment or during thermal loading. Basic physical properties (in concrete terms bulk density, matrix density and open porosity), mechanical properties (in concrete terms tensi...

In this paper, there are summarized the results of an experimental program focused on basic, mechanical and thermal properties of cement composites according to the high – temperature loading. Four different materials were studied, which differed in used kind of cement and amount of fibers. As a matrix for studied composites the aluminous cement wa...

The paper deals with self-compacting concrete (SCC) and the change of its properties after exposure to thermal loading. Two types of microfillers were used (along with appropriate amount of superplasticizer) to gain concrete which would meet the requirements for SCC – limestone powder and fly ash. Specimens were subjected to temperatures of 600 °C...

This article is focused on SCM questions. Studied material - metashale belongs among artificial pozzolana with natural origin. Shale is clay mineral and by its burning at 700°C similar material as metakaolin arises. Metashale is used as cement replacement up to 60% in concrete production. By means of measurement of basic physical properties, mechan...

Plasters have always been an important component of a building structure, and as many other materials they were subject of quite a few modifications during their development. In view of the fact that thermal insulation properties of building structures belong to their basic characteristics, thermal insulating capabilities of plasters become an impo...

Sandstones, clastic sedimentary rocks, were used as load-bearing materials for centuries. Even though nowadays these natural materials are usually used as decorative or facing materials, sandstones still belong to the group of building materials. Rocks, which can be called sandstones (from a geological point of view), vary widely. All properties de...

The influence of basalt fibres and aggregates on the thermal expansion of cement composites is analyzed. Four different composite mixes based on aluminous cement are designed and tested. Experimental results show that the application of basalt components leads to the reduction of the increase of open porosity after high temperature loading from 47%...