The article discusses the ways to improve the building materials’ and products’ biostability as well as their effectiveness. Impregnation of the readymade concrete and the reinforced concrete articles with special polymer compositions or monomers is one of the methods to improve the concrete properties. The article describes the ways aimed at increasing the materials biostability by introducing the fungicidal additives into their composition.

Development and Research of Methods to Improve the Biosistability of Building Materials

Introduction. The study considers the issue of safety of the human vital activity environment in the field of construction and usage of buildings, which includes, along with other types of safety, thermal, biological and mechanical safety. The last ones cannot be provided if there are inorganic hygroscopic salts in construction materials of external enclosures due to influence of the salts on the thermal, mechanical and other properties of the materials. Thermal conductivity coefficient of damped saline construction materials is determined on a developed experimental facility operating according to the principle of unsteady thermal conditions. A statistical analysis of the experimental results on thermal conductivity of materials possessing various structures and densities is carried out. Significance of the influence of the “salt content” factor on the thermal conductivity of saline materials in comparison with control non-saline samples is revealed. \nMaterials and methods. Construction materials for the study are selected as follows: autoclave lime-and-sand brick and burnt brick with a density of 1800 kg/m3, autoclave foamed silicate with a density of 650 kg/m3, wood concrete with a density of 616 kg/m3 and mineral wool slabs with a density of 150 kg/m3. The generally accepted methods of laboratory research and statistical processing of experimental results are used. Laboratory methods include preparation, salinization with sodium chloride, potassium sulfate and calcium chloride, and measurements of the thermal conductivity coefficient of construction material samples. \nResults. The determination of thermal conductivity of wetted saline materials under unsteady thermal conditions makes it possible to eliminate drying of the samples and migration of salts and moisture. The presence of salt crystals increases the thermal conductivity of dry materials up to 80 % (rel.). Damping the samples promotes the dissolution of the crystals and lowering the thermal conductivity of the samples to values lower than those of non-saline samples with the same moisture content. \nConclusions. The study proves the significance of the salinization effect on the thermal and physical characteristics of construction materials that must be taken into account when thermal engineering calculating external enclosures and predicting their moisture state during usage.

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Safe usage of external enclosures under adverse environmental exposure

1 The manufacture ofUHPC has until now been extremely difficult and complex and can hardly be mastered in conventional precast plants - in ready-mixed concrete plants, nearly impossible to achieve. Dyckerhoff has now developed a cement according to the standards that considerably facilitates the manufacture of UHPC and permits moreover the use of conventional mixing plants and even the usual aggregates. The following article focuses on successfully executed high performance concrete projects. Using selective special pozzolans, this conception has now been further developed into the first special cement, Nanodur® CEM II/B-S 52,5 R, for UHPC without silica fume.

From Mikrodurto Nanodur technology: Standard cement for practice-oriented manufacture of UHPC

The research results in the field of microbiological corrosion of building materials of domestic and foreign experts are presented. It is shown that microorganisms cause corrosion of concrete on cement and other binding metal and other materials. Metals in the order of decreasing the rate of biocorrosion are arranged in the following row: aluminum, mild steel, zinc, brass, copper, stainless steel.

Concrete, due to its high surface activity, is capable of adsorbing a wide variety of substances, including microorganisms: bacteria and mycelial fungi. Among bacteria, nitrifying agents, thionic, iron and silicate bacteria and others participate in the corrosion of cement concrete (mainly due to their acid secretions). According to the data of a number of authors, on the surface of stone building materials mycelial fungi of the genera Penicillium, Aspergillus, Trichoderma, Cephalosporium prevail.

Biodeterioration in this case mainly comes down to the disruption of cohesion of constituent components as a result of exposure to mineral or organic acids, as well as enzymes and due to chemical reactions between the cement stone of solutions and concretes and the waste products of microorganisms.

The compositions of bituminous composites at various ratios of the materials used without inclusion in the composition of fungicides showed non-fungal resistance and non-fungicide.

Comparison of concrete on gypsum and phosphogypsum binders showed that samples on a phosphogypsum binder overgrow microorganisms somewhat more, wood materials are subject to significant biodeterioration at high humidity.

Biodegradation of wood occurs mainly due to the use of mushrooms as food sources of cellulose, lignin and other components.

Synthetic polymers and materials based on them are significantly superior to natural polymers in biostability. However, under certain operating conditions, they are damaged by biological agents. Biological damage to plastics, as well as other materials, occurs simultaneously with their aging under the influence of external physical and chemical factors (ultraviolet radiation, water, temperature changes, etc.). Additives that are usually always present in polymer compositions (fillers, plasticizers, stabilizers, antioxidants, modifiers, pigments, etc.) significantly affect the biostability of polymeric materials.

One of the effective ways to increase the biostability of composite building materials is the introduction of fungicidal additives in their composition. It is also shown that of great importance in increasing the durability and increasing the life of some building structures (metal products, communications, underground pipelines and some others) is their protection by paint and varnish coatings.

Microbiological corrosion of building materials

Due to the introduction of reinforcing fibers into concrete, it is possible to overcome one of the main disadvantages of concrete-low tensile and bending strength. This is due to the fact that the reinforcing fibers take on a tensile stress, resulting in increased tensile resistance (in percentage terms, this is about 250%). In addition, reinforcing fibers contribute to the uniform distribution of moisture in the concrete due to which internal loads are reduced, crack resistance is approximately doubled and the impact strength of the concrete is 12 times increased. In addition, the deformability, frost resistance, heat resistance, water resistance and corrosion resistance of concrete structures are significantly increased. What makes fibroblast ideal material for use in 3D printing.

Technology of 3-D Printing of Fiber Reinforced Mixtures

In this paper, we consider a method of increasing biological resistance and biological durability of buildings and constructions that are subject to destruction from the impact of microorganisms activity. This article presents the results of studies of innovative materials in the field of bioresistant building materials. Powders of milled quartz sand and limestone were the fillers for the composites. Limestone used for the experiments is from the Chechnya depostits. We have implemented optimization for the cement composites compositions using the methods of mathematical experiment design. We derived the dependences describing how the bioresistance coefficient, the elastic modulus and the water demand depend on the granulometric composition after 3 and 9 months of aging in the environment of filamentous fungi. We have found that the multifractional compositions have a higher bioresistance coefficient. We determined the fungal resist compositions.

Biological Resistance of Cement Composites Filled with Limestone Powders

In this paper, the results of testing cement composites under the conditions of the effect of high humidity and variable positive temperatures are given.By the coefficient of variation of hardness (stability), the compositions are compared with various fillers, plasticizing and other fungicidal additives.To decide on the stability (stability) of the structure and properties of composites, it is proposed to rely on the area of the polygon obtained as a result of piecewise linear approximation of the exposure points. Explanations of the influence of environmental factors on hardness change of the composites.

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Research of behavior of cement composites in conditions of high humidity and variable positive temperatures

The article presents the results of a study of impact strength of underground cement materials with different water content activated by mixing water with the addition of high range plasticizers, biocidal agents, pigments, ground quartz, silica fume and fine aggregate. Samples for testing are formed in plates of size 150×100×10 mm. Testing was conducted at impact drop-weight method ASTM D7136. The maximum contact force, contact duration and magnitude of the pulse of the drummer were considered as the test parameters. The good results of the studied parameters showed highly filled plasticized compositions of the new generation. The use of iron oxide with yellow and green glauconitic pigments allows obtaining good results. Activation of the mixing water led to a rise in the maximum contact force in the case of the processing mode of E+М (3–3) while reducing the duration of the contact and the magnitude of the impulse. During the test of the biocidal composites with different biocidal preparations, it was established that the best indicators of the impact strength correspond to materials with the addition of «Teflex Antiplesen».

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Irina V. Erofeeva

Papers

Biological Resistance of Cement Composites Filled with Limestone Powders

Research of behavior of cement composites in conditions of high humidity and variable positive temperatures

Impact strength of underground cement materials

Selection of compositions of decorative finishing powder-activated concrete with a grain texture surface by rheological properties

Strength and frost resistance of decorative and finishing powder-activated concrete with grain texture surface