RU2471188C1 - Method of testing structural materials for biostability - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method involves dipping and holding samples of the test materials at room temperature into a weakly aggressive medium - mixture of organic acids: 0.9-1.1% acetic acid, 0.9-1.1% citric acid, 0.09-0.12% oxalic acid, said acids being in ratio of 1.8:2.7:0.8-2.1:3.1:1.2. After exposure, the samples are removed and dried to constant weight and their strength characteristics are then determined.

EFFECT: high efficiency and reliability of tests.

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Description

The invention relates to the construction, in particular to the field of testing building materials for biostability in the laboratories of manufacturers.

The problem of biodeterioration is relevant in all industries from food to space, but it is most relevant in the construction industry due to the fact that biological damage to building products and structures leads not only to a decrease in their strength characteristics, but also to a deterioration of the indoor microclimate, which the queue adversely affects human health.

Known methods for testing building materials for biostability according to GOST 9.049-91 “Unified system of protection against corrosion and aging. Polymer materials and their components. Laboratory test methods for resistance to mold fungi. " This standard establishes three laboratory test methods for mold resistance. The essence of these methods is to withstand materials contaminated with fungal spores under optimal conditions for their development, followed by assessment of fungus resistance by the degree of development of molds and by changing the characteristic properties of materials.

The main disadvantage of these methods should be attributed to the fact that they are intended for testing only polymer building materials (plastics, compounds, rubbers, adhesives, sealants). In addition, this method does not allow to judge the changes in the physico-mechanical characteristics of the studied materials, and its use is dangerous to human health.

A known method of testing building materials for biostability in accordance with GOST 9.048-89 "Methods of laboratory tests for resistance to mold fungi", which consists in the direct effect of microorganisms on the studied samples and exposure of infected test samples in different conditions for the development of molds for a certain time.

After exposure, the biostability of the materials is evaluated in points.

The disadvantages of this method include its danger, because when testing samples and products for mushroom resistance, mushrooms are used, which can be a source of danger to humans. It is also worth noting that the use of this method is complicated by the need to create special conditions to maintain the viability of microorganisms, as well as the need to obtain a permit from the sanitary and epidemiological surveillance authorities. In addition, further testing to determine the strength characteristics of the samples is difficult, due to the need for their mandatory decontamination (disinfection).

Known work Turkova Z.A. [Turkova Z.A. The role of physiological criteria in the identification of micromycetes biodestructors // Methods of isolation and identification of soil micromycetes-biodestructors. Vilnius, 1982. P.117-121], which investigated the effect of citric acid and hydrogen peroxide on polyester and polyurea polymer building composites. In this paper, we consider the effect of only one organic acid on polymeric building materials, there is no analysis and does not consider the effect of other organic acids (metabolic products).

There is also a known method of testing [V.F.Smirnov. Plastics. 1977, No. 1, pp. 63-67] in solutions of organic acids (oxalic, or succinic, or citric, or α-ketoglutaric, or malic, or fumaric) polymer building materials based on polyamide PA6-211-DS-K. Samples were placed in a solution of one of these organic acids with a concentration of 10 ^-2 mol and kept for 14 days.

The disadvantages of this method include the lack of analysis of the joint effect of organic acids on the material, which does not reflect the effect in the natural environment in which building materials are used. In addition, only one polymer material is considered in the work and mineral building materials (concrete) are not considered at all.

The objective of the invention is to bring the test conditions closer to the natural one by assessing the joint effect of organic acids on building materials and developing a method for testing building materials on the bio-stability of a person safe for human health in laboratory conditions, including in the laboratories of manufacturers.

The result is achieved by the fact that in the method of testing building materials for biostability, which consists in immersing and holding samples of building materials in a slightly aggressive medium, extracting, drying to constant weight and then determining the strength characteristics according to the invention, a mixture of organic acids is used as a slightly aggressive medium: 0.9 -1.1% acetic acid, 0.9-1.1% citric acid, 0.09-0.12% oxalic acid in the ratio: 1.8: 2.7: 0.8-2.1: 3, 1: 1.2.

To solve this problem, we chose a slightly aggressive medium, which is a mixture of organic acids, which are the most common metabolites of microorganisms. Acetic acid (LAVERNA, Moscow Chemical Company, ChCH ice, GOST 61-75) is a colorless transparent liquid; oxalic acid (ChP, GOST 22180-76) is a transparent crystals soluble in water; citric acid (ChDA GOST 3562-69) is a colorless crystal.

The method of testing building products for biostability is as follows:

The aggressive medium is prepared in the indicated ratios (table 1) and within the specified concentrations.

Table 1 No. p / p Name of components Concentration% Percentage one Acetic acid 0.9-1.1 32-34 2 Oxalic acid 0.09-0.12 30-49 3 Lemon acid 0.9-1.1 15-17

Samples of the studied products are laid on the bottom of the container made of a material resistant to microorganisms in such a way as to exclude contact of the samples with each other and fill with the above slightly aggressive medium so that the upper edge of the medium is higher than the upper edge of the samples. Then the container is hermetically sealed and the samples are kept at room temperature for 28 days.

At the end of the exposure, the samples are dried to constant weight, weighed and tested for strength characteristics. By changing the strength characteristics they judge the degree of damage to the material.

Samples of cement-sand stone with a size of 20 × 20 × 20 w / c 0.6, protected by polymer coatings that were exposed in the above environments for 28 days, were selected as objects of study. The tests showed that the impact of the proposed aggressive environment and environment with microorganisms on building materials is identical. The test results are presented in table 2.

table 2 Sample No. Cube compressive strength, R _SJ, MPa Exposure in the proposed environment Exposure in a medium with microorganisms one 10.83 10,42 2 11.67 13.34 3 12.50 12.50 four 12.50 10,42 5 10.83 12.50 Average value 11.67 11.53

The method of testing building materials for biostability according to the invention allows us to understand the general picture of the effect of metabolic products of microorganisms that imitate a mixture of organic acids on a material, since acetic acid characterizes the action of monobasic acids, oxalic acid - dibasic, citric - tribasic. It should also be noted that the proposed test method can be applied in the laboratory of manufacturers of building materials without special permission from the sanitary and epidemiological surveillance authorities and without harm to human health, due to the lack of contact with pathogenic microorganisms.

Claims (1)

A method of testing building materials for biostability, which consists in immersing and holding samples of building materials in a slightly aggressive environment, extracting, drying to constant weight and then determining the strength characteristics, characterized in that a mixture of organic acids is used as a slightly aggressive medium: 0.9-1, 1% acetic acid, 0.9-1.1% citric acid, 0.09-0.12% oxalic acid, in a ratio of 1.8: 2.7: 0.8-2.1: 3.1: 1 , 2, respectively.