Papers by Nadezda Stevulova
Advances in Materials Science and Engineering
Hemp Fibre Reinforced Composites
Proccedings of 10th International Conference "Environmental Engineering"
The conventional homogeneous materials can no longer effectively satisfy the growing demands on p... more The conventional homogeneous materials can no longer effectively satisfy the growing demands on product capabilities and performance, due to the advancement in products design and materials engineering. Therefore, the fibre reinforced composites with better properties and desirable applications emerged. Natural fibres have high strength to low weight ratios and have good sound and thermal insulation properties. Combination of organic filler and inorganic matrix creates high-quality products such as fibre boards and composites. The great importance is attached to industrial hemp as source of the rapidly renewable fibres and as non-waste material. Industrial hemp fibre has great potential in composite materials reinforcement. However, improving interfacial bonding between fibres and matrix is an important factor for its using in composites. This paper deals with hemp fibre reinforced composites in civil engineering as component part of sustainable construction. Prepared lightweight co...
Today, the growing trend in the construction indust ry is to create a sustainable construction by... more Today, the growing trend in the construction indust ry is to create a sustainable construction by minimizing the production of emissions and repla cing the limited material resources for the renewable raw materials. This article deals wit h the using of alternative materials (plant fibers) that are environmentally friendly. The grea t importance is attached to the industrial hemp, specifically to the woody part of hemp plant called hemp hurds, as reinforcement for composite materials for the purpose of the construc tion. In this article, the attention is given to the investigation of physical and mechanical pro perties (compressive strength, density, thermal conductivity coefficient) of the prepared l ightweight composites based on hemp hurds (3 different mean particle length) as a filler and two alternative binders such as MgO-cement and hydrated lime with cement addition after 28, 60 , 180 days of hardening. This paper deals with the problematic of the use of hemp hurds in buildin...
Chemical engineering transactions, 2017
Lightweight Composites Based on Technical Hemp Hurds in Construction Industry Ivana Schwarzova*, ... more Lightweight Composites Based on Technical Hemp Hurds in Construction Industry Ivana Schwarzova*, Nadezda Stevulova, Tomas Melichar Technical University of Kosice, Faculty of Civil Engineering, Institute of Environmental Engineering, Vysokoskolska 4, 042 00 Kosice, Slovakia Brno University of Technology, Faculty of Civil Engineering, Institute of Technology of Buildings, Materials and Components, Veveri 331/95, 602 00 Brno, Czech Republic [email protected]
Introduction Following a normal growth in population, the amount and type of waste materials have... more Introduction Following a normal growth in population, the amount and type of waste materials have increased accordingly. Many of the non-decaying waste materials will remain in the environment for hundreds, perhaps thousands of years. The non-decaying waste materials cause a waste disposal crisis, thereby contributing to the environmental problems. The problem of waste accumulation exists worldwide, specifically in the densely populated areas. Most of these materials are left as stockpiles, landfill material or illegally dumped in selected areas [1]. In the world is increasing demand and interest in aggregates from non-traditional sources such as from industrial by-products and recycled construction and demolition wastes. The American Concrete Institute (ACI) focuses on the removal and reuse of hardened concrete whereas the Department of the Environment and Water Resources in Australia and CSIRO have developed a guide on the use of recycled concrete and masonry materials. The Waste ...
Recycled Cellulosic Fibers and Lignocellulosic Aggregates for Sustainable Building Materials
World Academy of Science, Engineering and Technology, International Journal of Civil, Environmental, Structural, Construction and Architectural Engineering, 2016
Sustainability is becoming a priority for developers and the use of environmentally friendly mate... more Sustainability is becoming a priority for developers and the use of environmentally friendly materials is increasing. Nowadays, the application of raw materials from renewable sources to building materials has gained a significant interest in this research area. Lignocellulosic aggregates and cellulosic fibers are coming from many different sources such as wood, plants and waste. They are promising alternative materials to replace synthetic, glass and asbestos fibers as reinforcement in inorganic matrix of composites. Natural fibers are renewable resources so their cost is relatively low in comparison to synthetic fibers. With the consideration of environmental consciousness, natural fibers are biodegradable so their using can reduce CO 2 emissions in the building materials production. The use of cellulosic fibers in cementitious matrices have gained importance because they make the composites lighter at high fiber content, they have comparable cost - performance ratios to similar b...
Lightweight composites based on natural fibres as organic filler are studied for several years. U... more Lightweight composites based on natural fibres as organic filler are studied for several years. Using renewable resources (like natural fibres) instead of non-renewable is very current topic in developed countries. The use of alternative and environmentally friendly materials like plant fibres from hemp, jute, sisal and the others as reinforcement for composite materials is attractive for the purpose of the construction. The great importance is attached to the industrial hemp, specifically to the woody part of hemp plant called hemp hurds as a reinforcement for composite materials for the purpose of construction. Hemp hurds composite is a prospective building material because of its unique properties (exceptional thermal insulation, antiseptic, acoustic and mechanical properties). In this paper, the attention is given to the physical modification of hemp hurds (cooking in water for a time period) and to the preparation of the lightweight composites based on this organic filler and o...
In this paper, the overview of knowledge about the properties of lightweight composites based on ... more In this paper, the overview of knowledge about the properties of lightweight composites based on hemp hurds with MgO-cement as an alternative binder is given. There are summarized the results of the development of density, compressive strength, thermal conductivity, thermal behaviour and water sorption of the composites in the dependence on different filler portion and its mean particle length. Decrease in density, compressive strength and thermal conductivity coefficient with an increasing share of hemp hurds (20-60 vol. %) in hardened composites was found. Physical and mechanical properties of bio-composites depend also on the particle size in length dimension of hemp hurds. Compressive strength and water sorption of composites after 28 days of hardening increase with decreasing mean particle length, while this effect on thermal conductivity of composites was not confirmed. Thermal loading of composites (50-200°C) led to their damage by increasing temperature. The most significant...
This article discusses about the possibility of using industrial hemp as a source of natural fibr... more This article discusses about the possibility of using industrial hemp as a source of natural fibres for purpose of construction. The technical hemp (Cannabis Sativa) is the source of two types of fibres; bast fibres (used mainly in the paper and textile industries) and woody fibres hurds. In recent decades hemp hurds have experienced a renaissance in use in the construction industry. This material is waste resulting from the processing of hemp stem on bast fibres. For the purposes of construction it has potential thanks to their exceptional thermal insulation, antiseptic, acoustic and mechanical properties. One of the aspects of using hemp products in building industry is that these materials are environmentally friendly in comparison to the used conventional materials (such as conventional insulating materials with polymer matrix or based on mineral wool). In this article, the lightweight composites based on hemp hurds (as a biomass) and nonconventional binders MgO-cement are teste...
Civil and Environmental Engineering
This study is aimed at the application of alternative binder (AB) into bio-aggregate-based compos... more This study is aimed at the application of alternative binder (AB) into bio-aggregate-based composite. The technically important parameters (density, thermal conductivity, water absorption and compressive strength) of 28, 60 and 90 days hardened green composites containing chemically and physico-chemically modified hemp hurds (HH) with AB compared to the Portland cement (PC) are presented. Testing of two reference bio-composites with original HH confirmed higher values of compressive strength and thermal conductivity unlike water absorption for all hardened specimens based on alternative binder (MgO-cement) compared to conventional PC. Changes in the final properties of hardened bio-composites were affected by treatment process of organic filler and alkaline nature of MgO-cement. The combination of purified HH by ultrasound treatment and AB appears to be promising for preparation of bio-based composite material with better properties compared to PC. In this paper, other option of the...
Materials
This paper aims to develop recycled fiber reinforced cement plaster mortar with a good workabilit... more This paper aims to develop recycled fiber reinforced cement plaster mortar with a good workability of fresh mixture, and insulation, mechanical and adhesive properties of the final hardened product for indoor application. The effect of the incorporation of different portions of three types of cellulose fibers from waste paper recycling into cement mortar (cement/sand ratio of 1:3) on its properties of workability, as well as other physical and mechanical parameters, was studied. The waste paper fiber (WPF) samples were characterized by their different cellulose contents, degree of polymerization, and residues from paper-making. The cement to waste paper fiber mass ratios (C/WPF) ranged from 500:1 to 3:1, and significantly influenced the consistency, bulk density, thermal conductivity, water absorption behavior, and compressive and flexural strength of the fiber-cement mortars. The workability tests of the fiber-cement mortars containing less than 2% WPF achieved optimal properties c...
Journal of Renewable Materials
The aim of this study was to characterize two types of cellulosic fibers obtained from bleached w... more The aim of this study was to characterize two types of cellulosic fibers obtained from bleached wood pulp and unbleached recycled waste paper with different cellulose content (from 47.4 percent up to 82 percent), to compare and to analyze the potential use of the recycled fibers for building application, such as plastering mortar. Changes in the chemical composition, cellulose crystallinity and degree of polymerization of the fibers were found. The recycled fibers of lower quality showed heterogeneity in the fiber sizes (width and length), and they had greater surface roughness in comparison to high purity wood pulp samples. The high purity fibers (cellulose content > 80.0 percent) had greater crystallinity and more homogeneous and smooth surfaces than the recycled fibers. The presence of calcite and kaolinite in all of the recycled cellulosic fibers samples was confirmed, whereas only one wood pulp sample contained calcite. The influence of the chemical composition was reflected in the fiber density values. Changes in the chemical composition and cellulose structure of the fibers affected the specific surface area, porosity and thermo physical properties of the fibers. More favorable values of thermal conductivity were reached for the recycled fibers than for the wood pulp samples. Testing the suitability of the recycled fibers with inorganic impurities originating from the paper-making processes for their use as fillers in plastering mortars (0.5 wt.% fiber content of the total weight of the filler and binder) confirmed their application by achieving a compressive strength value of 28 day-cured fiber-cement mortar required by the standard as well as by measured more favorable value of capillary water absorption coefficient.
IOP Conference Series: Materials Science and Engineering
The application of bio-based material such as cellulose fibres derived from renewable source to c... more The application of bio-based material such as cellulose fibres derived from renewable source to cement mortars was investigated and the properties of fresh mixtures and hardened mortars were characterized. The mixtures composition consisted of combined addition of the selected kind of cellulose fibres (bleached wood pulp) and superplasticizer (polycarboxylate ester). The aim was to produce a cement mortar with the improved properties for indoor application. The 0.5 wt.% fibre addition (from weight of filler and binder) and superplasticizer dosage of 1% in the mixtures were used. Reference cement mortar did not contain cellulose fibre and superplasticizer. The comparative study of the fresh fibre cement mixture properties has been showed worse flowability behaviour of mixture with plasticizer, as expected. The the beneficial effect of the superplasticizer was not proven even on the compressive and flexural strength of fibre cement mortars after 7, 28 and 90 days of hardening. The per...
An experimental study on MWCNT–water nanofluids flow and heat transfer in double-pipe heat exchanger using porous media
Journal of Thermal Analysis and Calorimetry
This paper presents the results of an experimental investigation on the heat transfer characteris... more This paper presents the results of an experimental investigation on the heat transfer characteristics of multi-walled carbon nanotube aqueous nanofluids inside a countercurrent double-pipe heat exchanger using porous media. Aluminum porous media (ε = 67%) were used because of the construction of the medium, with porous plate media at the center of the inner tube and with three porous plates on the walls of the inner tube. The effects of operating parameters including flow rate (4600 < Re < 7600), mass fractions of nanofluids (0.04–0.25 mass%), and inlet temperature of nanofluids (Tin = 50 °C) on the heat transfer coefficient were investigated. The results indicate that imposing the plate porous media increases the heat transfer coefficient significantly, and the highest increase in the heat transfer coefficient is 35% which is obtained in the test of the lowest mass fraction (0.04 mass%) with three-plate porous media in the experiment range. As the mass fractions increased, the value of heat transfer enhancement assisted by porous media gradually decreased. Also the lower range 100 (L h−1) of the volume flow rate has a powerful enhancement on the enhancement coefficient, while the higher ranges 300 (L h−1) have low influence.
Optimal arrangements of a heat sink partially filled with multilayered porous media employing hybrid nanofluid
Journal of Thermal Analysis and Calorimetry
Although many studies have addressed the urge of exploring the porous media partially embedded in... more Although many studies have addressed the urge of exploring the porous media partially embedded in a channel due to its wide engineering applications, the heat transfer and fluid flow of a channel consisting of multilayered metal foam are relatively untouched. To tackle this research gap, a numerical study is conducted to analyze a channel partially filled with a three-layered porous medium—occupying sixty percent of a heat sink—over the Reynolds numbers ranging from 50 to 150 and water base fluid. To this aim, two configuration models of porous media are evaluated here: metal foam with (A) similar particle diameters (2 mm) and different porosities (0.75, 0.85, 0.95) and (B) similar porosities (0.88) and different particle diameters (1, 2, 3 mm). Darcy–Brinkman–Forchheimer and local thermal non-equilibrium methods are used to solve the momentum and energy equations in the porous region, respectively. The validity assessment of the local thermal equilibrium method elucidates that its accuracy is questionable at higher porosities and particle diameters of the metal foam—highlighting the necessity of incorporating the LTNE method under the mentioned circumstances. Among the considered geometries, the optimal arrangements of metal foam at both models are selected according to the performance evaluation criteria value.
Open Engineering
Nowadays, there is paying an attention to the utilization of natural, renewable and biodegradable... more Nowadays, there is paying an attention to the utilization of natural, renewable and biodegradable resources of raw materials of lignocellulosic character, residues from agricultural crops and wood processing as well as waste from papermaking industry in building composite materials preparing. Also recycled fibres coming from waste paper are considered as valuable material. The objective of this study is to utilize these recycled cellulosic fibres into cement composites and characterise their impact on resulting physical and mechanical properties of fresh and hardened cement composites. Manufactured cement composites contained 0.2%, 0.3% and 0.5% addition of cellulosic fibres. In fresh fibre cement mixtures reduction in workability with increasing amount of cellulose fibres was noticed. Density as well as compressive and flexural strength of 28 and 90 days hardened fibre cement composites was tested. Distribution of cellulosic fibres with 0.5% addition in hardened fibre cement compos...
Materials
This experimental study was focused on the application of an alternative binder based on MgO, and... more This experimental study was focused on the application of an alternative binder based on MgO, and the variation of its components by the combination of two MgO products obtained by the calcinations of natural magnesite, siliceous materials (river sand and silica fume), and alkaline admixture in the mixture for a preparation of composite based on biomass waste such as hemp hurds as organic filler. This paper presents the results of the effect of an MgO binder composition on the compressive strength of the bio-aggregate-based composites. Other physical properties, such as the bulk density, thermal conductivity coefficient, and water absorption, were also investigated. The measured strength parameters of the bio-composite samples that were hardened for 28 days demonstrate that the binder consisting of optimal calcined MgO and silica fume as a total replacement for sand ensures a good binding of the matrix with hemp hurd compared to other varied compositions of alternative binder. No si...
Selected Scientific Papers - Journal of Civil Engineering
This paper presents physical and mechanical properties of cementitious composites/plasters contai... more This paper presents physical and mechanical properties of cementitious composites/plasters containing cellulosic fibers in portion 2.0% and 5.0% of filler replacement after 28 days of hardening. Cellulosic fibers (Greencel) originated from bleached wood pulp and unbleached waste paper used in this experimental work were characterized from the point of view cellulose structure. Experimental investigations reveal that adding cellulosic fibers reduces composites density (up to 8.2 %) in comparison with composites without any fibers. Moreover, the presence of wood pulp and recycled fibers in composites cause higher values of water absorbability than sample without fibers. Also, the decrease in compressive strength values for tested fiber cement plasters was observed (14.1 - 18.0 MPa) in comparison to reference sample (26.6 MPa). But the identified compressive strength values are in accordance with European standard (5 MPa) for plasters.
Physical and thermal behavior of cement composites reinforced with recycled waste paper fibers
In this study, three types of recycled waste paper fibers were used to manufacture cement composi... more In this study, three types of recycled waste paper fibers were used to manufacture cement composites reinforced with recycled cellulosic fibers. Waste cellulosic fibers in quantity of 0.2, 0.3, and 0.5 wt.% were added to cement mixtures. Physical properties such as density, water capillarity, water absorbability and thermal conductivity of fiber cement composites were studied after 28 days of hardening. However, durability of composites was tested after their water storage up to 90 days. Final results of tested properties of fiber cement composites were compared with cement reference sample without cellulosic fibers.
Journal of Civil Engineering, Environment and Architecture
The development in the field of building materials tending to biocomposites made from natural res... more The development in the field of building materials tending to biocomposites made from natural resources is increasing worldwide. Natural fibre-reinforced composites are attractive due to their environmental and economic advantages. Natural fibres such as kenaf, jute, hemp and sisal are combined with inorganic matrix (based on conventional and/or non conventional material) in biocomposites for their application in building industry. A great importance in Europe has technical hemp as sustainable and fast renewable resource of lignocellulosic fibres with high specific strength, which can be utilized as filler/reinforcement material in composites. This paper presents the results obtained from an experimental study of the mechanical and physical properties of biocomposites prepared with Portland cement as a binder and chemically treated and untreated hemp hurds as a filling agent.
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Papers by Nadezda Stevulova