Nadežda Števulová

Bio-Corrosion Resistance of Concretes Containing Antimicrobial Ground Granulated Blastfurnace Slag BIOLANOVA and Novel Hybrid H-CEMENT

The article deals with the study of biocorrosion of concretes by sulphuric acid induced by oxidizing bacteria Acidithiobacillus thiooxidans. The concretes were prepared from reference cement CEM I 42,5 N, the mixtures of CEM I 42,5 N and antimicrobial ground granulated blastfurnace slag BIOLANOVA (GGBS) (with amount of GGBS 65 mass % - CEM III/A 32,5 N, 75 mass % - CEM III/B 32,5 N, 85 mass % - CEM III/C 32,5 N a 95 mass % - CEM III/C 32,5 N) and novel hybrid cement H-CEMENT (HC). The experiments were carried out in model laboratory conditions at 30 °C during 91 days. The degree of deterioration of concrete samples has been studied on the base of the pH changes of leachate, the concentrations of selected ions such as S, Ca and Si and the mass changes. It has been clearly confirmed, that in the presence of bacteria, the pronounced degradation of the samples occurred with exception of HC sample, which behaviour proved differences to the other samples. The HC concrete possessed more alkali leachate in comparison with the others. The concentration of sulphur S in leachate was increased by metabolic activity of bacteria due to biogenic H2SO4 formation. The increase of S concentration acidified leachate and so promoted leaching next substances from the samples. The concentration of silicon Si in leachate was promoted by metabolic activity of bacteria, as well. The development of Ca leaching concentration has been similar at all composite samples as in the case of reference CEM I 42,5 N concrete, however the smallest portion of leached Ca has been determined at HC concrete. The Ca leaching concentration has been increasing with the amount of GGBS being added to the composite CEM III concretes. The different tendency has been also observed at the HC samples in regards to the mass changes. The increase in mass has been measured at all concrete samples with exception of HC concrete, at which the mass decrease has been found out. The results confirmed the resistance of the concrete composite samples containing GGBS and HC to the sulphate attack and the HC sample showed the highest resistance to the sulphate biocorrosion.

Characterization of Cellulosic Fibres Properties for their Using in Composites

Nowadays, the material recycling is growing trend in development of building materials and therefore using of secondary raw materials for production of new building materials. Transition from application non-renewable sources of raw materials to renewable raw materials in terms of sustainable composite is required. Renewable raw materials include organic sources of raw materials coming from natural plant fibres. This material is used to contribute environmental protection and to save non-renewable resources of raw materials. Wood fibres and cellulose fibres made from waste paper were selected for reinforcing cement-based materials. Application of cellulosic fibres into composites depends on their properties. Therefore, this paper is aimed to study of morphology and properties of cellulosic fibres. The comparison of strength parameters of 28 days hardened composites with 5% adding bleached wood and unbleached recycled fibres with those of reference composite without fibres showed that the values of compressive strength of fibrous cement based specimens were lower by 17 to 29 %.

Performance of Fiber-cement Boards in Biogenic Sulphate Environment

The paper presents the results of the study of selected fiber-cement boards parameters influenced by sulphur-oxidising (Acidithiobacillus thiooxidans) and sulphur-reducing bacteria (Desulfovibrio desulfuricans) attack. The experiments proceeded during 80 days under laboratory model conditions. The surface changes, chemical composition and pH of leachates as well as weight changes were investigated. The more extensive leaching of silicon and calcium ions from the cement matrix was confirmed under bacteria influence. The pH of liquid media has been settled to 7 and 9 for Acidithiobacillus thiooxidans and Desulfovibrio desulfuricans, respectively after initial increasing. Very small decrease in weight of samples in range 0.001 - 0.93 % was measured after the experiments.

Study of Cement Composites Properties with Filler Based on Wood Pulp

Sustainable building materials are based on the use of renewable materials instead of non-renewable. A large group of renewable raw materials are materials of plant origin containing cellulosic fibres which are used as filler into building material with reinforcement function of composite. This study aimed to establish the mechanical and physical properties of cement composites with organic filler, such as wood pulp. Pulp derived from wood pulping process is very interesting material as reinforcement in cement which contributes to a reduction of pollutants. In this paper, utilization of unbleached and bleached wood pulp in combination with cement matrix with emphasis on the physical and mechanical properties is studied. Varying the producing technology (wood pulp and cement ratio in mixture) it is possible to obtain composites with density from 940 to 1260 kg.m-3 and with compressive strength from 1.02 to 5.44 MPa after 28 days of hardening. The experimental results of mechanical properties indicate that cement composites with using unbleached wood pulp reaches higher values than composites based on bleached wood pulp. The percentage of water uptake increased with increasing the volume ratio of unbleached wood pulp in composite.

Basic Physical – Mechanical Properties of Geopolymers Depending on the Content of Ground Fly Ash and Fines of Sludge

Abstract The binding potential of fly ash (FA) as a typical basic component of building mixtures can be improved in mechanical way, which unfolds new possibilities of its utilization. This paper presents the possibilities of preparing the geopolymer mixtures based on ground (dm = 31.0 μm) FA, used in varying percentages to the original (unground; dm = 74.1 μm) one. As a modification, fine-grain sludge from the process of washing the crushed aggregates was used as filler in order to obtain mortar-type material. The basic physical-mechanical properties of mixtures are presented and discussed in the paper, focusing on time dependence. The following standard tests were executed after 2, 7, 28, and 120 days: density, total water absorption, flexural strength, and compressive strength. Ground FA provided for positive effect in all tested parameters, while incorporation of fine portion of sludge into the geopolymer mixture does not offer a significant technical profit. On the other hand, it does not cause the decline in the properties, so the environmental effect (reduction of environmental burden) can be applied through its incorporation into the geopolymer mixtures.

Implementation of recycled cellulosic fibres into cement based composites and testing their influence on resulting properties

Nowadays, the application of raw materials from renewable sources such as wood, plants and waste paper to building materials preparing has gained a significant interest in this research area. The aim of this paper is to investigate the impact of the selected plasticizer on properties of fibres composites made of cellulosic fibres coming from recycled waste paper and cement. Investigations were performed on specimens with 0.5 wt. % of fibre addition without and with plasticizer. A comparative study did not show positive influence of plasticizer on the density and thermal conductivity of 28 days hardened composite. The specimens after 1, 3 and 7 days of hardening with plasticizer exhibited the highest impact on compressive strength in comparison to composite without plasticizer but 28 days hardened specimens reached the same value of strength characteristic (41 MPa).

Role of Key Factors of Particulate Components in Biocomposites

The development of biocomposites based on natural fibres coming from plants and inorganic binder materials is in the foreground of research in the field of sustainable building materials. Biocomposites ́ properties are influenced by both particulate constituent characteristics. In last decades, the growing trend in using of plant fibres as filler and / or reinforcing material into biocomposites for building application is due to their renewability and environmentally friendly properties. Inorganic powdered binder substances, mainly Portland cement and/or hydraulic lime are used as matrix material in bio fibres reinforced composites. In this paper, the important characteristics of fibrous and isometric particles affecting the final properties of hardened composites will be discussed.

The Change of Swelling of Pulp Fibres under Recycling

During the process of monitoring of pulp fibres swelling, which is directly related to absorptivity, it was found that with the growing number of recycling cycles this characteristics significantly decreases. This phenomenon, which is considered as negative from the point of view of pulp fibres utilizing for paper manufacturing, could potentially find its positive application in other areas, eg. in the civil engineering for production of lightweight composites, where the reduction of water absorption of natural fibre materials is desirable.