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ELSEVIER Procedía Engineering 108 (2015) 301 - 308 =
www.elsevier.com/locate/procedia
7th Scientific-Technical Conference Material Problems in Civil Engineering (MATBUD'2015)
Influence of salting mineral materials on the development of fungi
Elzbieta Stanaszek-Tomala*, Teresa Stryszewskaa
a Cracow University of Technology, Warszawska 24, 31-155 Krakow, Poland
Abstract
In this paper presents the effects of the combined action of two aggressive environments. Then determine the effect of the content of sulphate ions or chloride on the growth of microorganisms and the possible impact of chemical-biological corrosion properties of moisture, mechanical structure of the ceramic materials.
To assess changes in the samples as a result of corrosion-induced chemical and fungi, the following parameters were selected: a chemical analysis, the goal was to determine the content of sulphate ions or chloride; pH; colony-forming units; mass moisture and absorbability of water, and research on the microstructure under the scanning electron microscope.
The results allowed to formulate a number of statements: ceramic materials are resistant to mould; original ceramic salt contamination of chloride ions or sulphate did not stop the operation of the biological environment; by the co-operation of both aggressive environments, material properties change.
© 2015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
Peer-reviewunder responsibilityof organizing committee of the 7th Scientific-Technical Conference Material Problems in Civil Engineering Keywords: ceramics- brick; mould fungi; MgSO4;NaCl; absorbability of water; mass moisture
1. Introduction
An effect of aggressive external environment on the durability of potsherd is connected with easily soluble sulphate and chloride salts. The related literature review, including such author as Baszkiewicz and Kaminski [1] as well as Stryszewska and Kanka [2] allows one to conclude that the presence of soluble salts containing chloride and sulphate ions leads finally to brick deterioration. Except, of the problem of masonry salinity and moistness an
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* Corresponding author. Tel.: +48 12 628-23-45; fax: +48 12 628-23-67. E-mail address: estanaszek-tomal@pk.edu.pl
1877-7058 © 2015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
Peer-review under responsibility of organizing committee of the 7th Scientific-Technical Conference Material Problems in Civil Engineering doi:10.1016/j.proeng.2015.06.151
effect of microorganisms on mineral building materials is also of great importance.
In mineral materials such as brick, concrete or mortar microorganisms (bacteria, mould fungi, algae) cause slow corrosion, i.e. biological corrosion or biodegradation. The susceptibility of given material to colonisation by microorganisms relies on its specific properties. This has been defined as bioreceptivity (susceptibility to biological colonisation) by Guillite [3]. This paper presents the division into the following three groups: primary bioreceptivity caused by internal material structure; secondary bioreceptivity resulting from features of the material altered by chemical and physical factors; and tertialy bioreceptivity that is a subject to biological colonization of man modified materials (e.g. after using preservatives, conservation).
Cording to Caneva et al. [4] biodeterioration manifests by increased moisture content, stains (discolorations) and mineral salt efflorescences. There are various effects of fungal activity depending on material type, e.g. a lime bonding agent loses its effect, while concrete, mortar or brick crush due to washing out of acid calcium carbonate. This results from the reaction of calcium carbonate with carbon dioxide (formed by fungi in metabolic processes). In addition, fungi produce organic acids, and as reported by May et al. [5] and McCauley [6], its compounds with calcium salts cause the deterioration of building mineral materials. There is a scanty literature on biodegradation of ceramic materials. Only a few papers, e.g. Chee et al. [7] and Gottenbos et al. [8] deal with strictly fungal activity on bricks. The available literature, for example Tiano et al. [9] shows that the pH can inhibit microbial growth on ceramic substrates. Although, ceramic materials should be insensitive to microorganism activity, biological colonisation depends strongly on environmental conditions and even less sensitive to biosensitive surfaces are easily colonised. However, which content of soluble salts causing material destruction effects material susceptibility to subsequent action of microbiological activity (mould hype fungi are specified in the literature. A subsequent action, also defined in the paper of Fiertak and Stanaszek-Tomal [10], occurs when the reactions in which the products (effects) resulting from the action of salts become substrates (causes) for the activity of fungi. The effects of salts and then mould fungi were observed.
Therefore, the aim of this study was to trace effect of two environments, i.e. chemical and microbiological ones and then the determination of effect of the content of sulphate or chloride ions on microbial growth and possible impact of chemical and microbial corrosion on ceramic material moisture properties and microstructure.
Nomenclature
H2O the samples
MgSO4 the samples
NaCl the samples
uncont. the samples
SO4/uncont. the samples
SO4-P.ch the samples
SO4-C.h. the samples
Cl/uncont. the samples
Cl-P.ch. the samples
Cl-C.h. the samples
contaminated of water. contaminated of MgSO4 contaminated of NaCl
nothing contaminated / reference residing in laboratory conditions contaminated with MgSO4, residing in the climatic chamber conditions. were first contaminated MgSO4 and then Penicillium fungi were first contaminated MgSO4 and then Cladosporium fungi contaminated with NaCl, residing in the climatic chamber conditions. were first contaminated NaCl and then Penicillium fungi were first contaminated NaCl and then Cladosporium fungi
2. Methods and materials
2.1. Choice of a corrosive environment
When selecting chemical corrosion environment the papers showing a significant effect of salt solutions containing sulphate or chloride ions on mineral material properties were taken into account.
When selecting microbial corrosion environment the experiments carried out in facilities affected by microbial corrosion have been considered. As indicated by Albright [11] and Hyvarinen et al. [12] fungi of the genera: Cladosporium, Aspergillus, Penicillium, Alternaria, Fusarium, Mucor, Trichoderma are most numerous. For further analysis Penicillium was chosen as most common, and Cladosporium as predominated.
2.2. The test materials
The study used a brick of the chemical and phase composition described in Table 1. The chemical composition of the materials was determined by the X-ray fluorescence XRF elemental analysis spectrometer. The crystalline phase or mineral content of the materials was analysed by the X-ray powder diffraction (XRD). According to the XRF analysis, the brick contains a large fraction of silica as well as the oxides of aluminium, iron, calcium, magnesium and potassium. According to the XRD analysis, the main phases in the tested brick includes mainly quartz, albite and mullite.
Table 1. Chemical and phase composition of the raw materials used.
Chemical composition
Oxides Content SiO2 Al2O3 Fe2O3 CaO MgO MnO K2O P2O5 SO3 Na2O TiO2 Ignition losses
[%] 57.5 18.9 6.15 6.33 2.64 0.13 2.83 0.28 1.52 0.71 0.87 2.05
Phase composition
Content Quarz Albite Microcline Mullite Anorthoclase Hematite Halloysite/ mica
[%] 35.9 39.4 - 18.0 - 6.6 -
From the brick discs about 10 cm in diameter and 1-2 cm in height was cut. At beginning, the specimens were dried to get solid mass at 105°C. The prepared specimens were exposed to corrosion environment, according to Stryszewska [13] consisting of:
• magnesium sulphate of SO42- ion concentration of 50g/dm3;
• sodium chloride of Cl- concentration of 50g/dm3.
The corrosion exposure was carried out at two stages. During the first two days the tested materials were immersed up to the half-height in corrosive solutions. During this period the exposed specimens became wetted over its full height due to capillary action. The specimens were then completely poured with corrosive solutions and kept in such state until saturation. Subsequently, the contaminated samples were dried under laboratory conditions, i.e. at 20±2 oC for next two days.
At next test stage, the specimens exposed to chemical corrosion were contaminated by microbial environment, i.e. with mould fungi belonging to the genera Penicillium chrysogenum (LOCK 0531, strein F00680) and Cladosporium herbarum (LOCK 0490, strain E123). Pure cultures of fungi were swabbed into 10 ml of distilled water. Petri dishes containing the solidified medium MEA were inoculated with the selected fungal culture (suspension). The inoculated dishes were incubated at 25±1°C and a relative humidity of 95±5% for 5 days. Then the dishes were swabbed into 10 ml of distilled water (suspension having spore count 1 x 106 spores per ml). This suspension was used to contaminate the previously prepared pulleys made from the ceramic and stone materials to be tested. As a nutrient material was used to modify Malt Extract Agar Modified-8927 (MEA) from BioChemika. The contaminated test elements were placed in a biological testing chamber with a temperature of 25±1°C and a relative humidity of 95±5%. Exposure time was 24 months. For comparison the "witness" or control samples (uncontaminated) were also tested.
2.3. The research methodology
To evaluate changes in specimen properties caused by chemical corrosion and mould fungi, the following parameters were chosen:
• chemical analysis to determine the content of sulphate or chloride ions before and after contamination. For testing purposes the water extracts of material/distilled water in the ratio 1:5 were prepared. Chemical analyses and certified tests were carried out spectrophotometrically by using the AL800 scectrophotometer manufactured by AQUALYTICA. The sulphate and chloride contents were expressed in percentage of the specimen total mass.
• pH value
The pH was tested by leaching. The mortar sample of 20g was collected from the surface and was put into 100 ml of distilled water (1:5 ratio). The suspension was stirred a few times within 24 hours. Then the suspension was filtered out and the pH was determined using an ion meter EUTECH CyberComm 6000 with a glass electrode attached.
• Colony-forming units
The indirect method of microorganism enumeration consists of spreading an appropriately diluted microorganism suspension on a solidified medium (also called a solid medium). The incubation and enumeration stages follow. A very important step is diluting the suspension appropriately, i.e. so that 1 cm3 contains 30 to 300 cells owing to the fact that numbers of colonies in this range are the easiest to count on the plate. Smaller numbers of colonies increase the error and greater ones make counting difficult. Serial dilutions are made in parallel from two separately analysed samples. The result so determined is given in cfu/cm2.
• Organic matter content
Determination of organic matter content was conducted on powdered paste and mortar specimens using the Walkley titration method, as described by Greweling and Peech see Nowosielski [14]. For each type of bar, 2.0 g samples were collected. To each sample, 5 ml of 1N potassium dichromate solution was added, immediately followed by 10 ml of concentrated sulphuric acid (96%). The resulting solution was stirred for one minute and then left to stand for about 30 minutes. After that time, 15 ml of distilled water and 10 drops of diphenylamine were added and the solution obtained was titrated with a solution of iron (II) sulphate (VI). Organic matter content is given as a percentage and calculated from the following formula: [%]=(0.69V)/m, where: V - volume of potassium dichromate reduced [ml]; M - sample mass [g]; 0.69 - solution titre.
• mass humidity (|iM), marking in accordance with DIN EN ISO 12570: 2002 [15] and absorbability of water (no) - measured according to ASTM (ASTM C 642) [16].
Mass moisture by mass was determined using the contaminated and uncontaminated samples. The test materials were weighed and then they were dried at 105°C to a constant mass. Moisture content by mass is calculated according to the following formula: |im=(mw-ms)-100%/ms, where: mw - mass of damp sample [g], ms - mass of dry sample [g].
The absorbability of water test was conducted according to ASTM (ASTM C 642) [16]. The specimens were dried at 105°C in oven until mass difference between two measurements at intervals of 24h was less than 0.5%. After cooling down, the specimens were immersed in water at around 21°C for 48h. Water absorption is calculated according to the following formula: nm=(mn-ms)100%/m5, where: mn -mass of sample saturated with water [g]; ms -mass of dry sample [g].
• structure that was studied under the Zeiss EVO MA10 scanning electron microscope equipped with the Bruker XFlash 6/30 energy dispersive X-ray spectrometer. Observations of changes in microstructure and the presence of fungi were carried on the surfaces of test samples. Furthermore, using the EDS was performed at selected locations and point quantitative analysis of surface elements.
3. Results and discussion
The tightness of ceramic materials was investigated by looking at mass moisture, absorbability of water. The
highlights of that research are shown in Table 2 which present the average values of three tests after exposure to microorganisms for 24 months. All tests were performed in triplicate. Scatter of results did not exceed 0.1%.
Table 2. Mass moisture, absorbability of water, chemical and biological parameters of brick.
content content pH contamination organic absorbability mass
of SO42- of Cl- of fungi matter of water moisture
%mass. %mass. 104 cfu/cm2 content %mass. %mass.
chemical contamination
H2O 0.77 0.01 8.0 - 0.01 26.81 0.57
MgSÜ4 1.51 0.01 7.6 - 0.02 27.81 3.98
NaCl 0.77 0.48 7.5 - 0.02 28.41 5.21
biological and chemical contamination after 24 months (conditions 25°C, 95%RH)
uncont. 0.77 0.01 8.0 - 0.01 26.81 0.57
SO4/uncont. 1.51 0.01 7.6 - 0.02 28.19 29.64
SO4 - P.ch. 1.13 0.01 7.1 6.6 9.13 26.89 28.86
SO4 - C.h. 1.20 0.01 7.1 7.9 8.83 26.87 28.25
Cl/uncont. 0.77 0.48 7.3 - 0.02 26.99 28.43
Cl - P.ch. 0.74 0.41 7.1 5.7 5.84 28.14 30.42
Cl - C.h. 0.42 0.33 7.3 4.0 6.01 28.60 30.16
The growth of mould fungi species of Penicillium and Cladosporium on the brick was evaluated based on the variation in the number of microorganisms per unit area, i.e. colony forming units (cfu) after 24-month contamination. The largest amount of fungi occurs on the brick contaminated primary by sulphate ions. For consequent contamination by fungi Penicillium is 6.6x104, and for fungus Cladosporium 7.9x104 cfu/cm2. The primary contamination by chloride ions inhibited slightly the growth of both microbial environments under investigation and reached 5.7 x104 for Penicillium, and 4.0x104 cfu/cm2 for Cladosporium.
When analysing pH for water solutions one may observe a decrease in pH for contamination by sulphate and chloride ions in 7.6 and 7.3, respectively. The contamination by fungi Penicillium or Cladosporium causes slight decrease in pH to the range of 7.1-7.3. This indicates that organic acids responsible for the pH decrease are produced by microorganisms. This correlates with the next analysed, i.e. content of organic substances. The largest percentage (%) of these substances was observed in the brick contaminated by SO42- - P.ch. and SO42- - C.h. and in both that the cases pH of water solutions decreases significantly compared to that of the brick contaminated by SO42- ions. The percentage of organic substances is lower by 2-3% of contamination by Cl- - P.ch. and Cl- - C.h. This is related to the brick pH decrease.
The content of sulphate ions in uncontaminated material is at the level of 0.77 % (w/w). This is connected with the presence of SO3 in the brick composition (Table 1). After contamination by sulphate ions, its content increase twice. The contamination by Penicillium or Cladosporium causes that the content of sulphate ions decreases to 1.1 and 1.2 % (w/w). For contamination by chloride ions the content of sulphates is at the initial level. Only for contamination by Cl- - C.h. the content of sulphate ions is lower by about 0.3 % (w/w). The contamination by chloride ions for bricks is about 0.5 % (w/w). For contamination by the fungus Penicillium this value slightly drops to 0.4 % (w/w) and to about 0.3 % (w/w) for Cladosporium. The losses in sulphate and chloride ions are associated with metabolic processes that occur in mould fungi.
The absorbability of water of uncontaminated bricks is about 27 % (w/w) and differs only slightly from that of contaminated specimens. For contamination by sulphate ions is about 28 % (w/w), and chloride ions are identical. The absorbability of water slightly decreases for contamination by SO42- - P.ch. and SO42- - C.h. compared to those of contaminated by sulphate ions only. However, for contamination by Cl- - P.ch. and Cl- - C.h. slightly increases to above 28% compared to those of contaminated by chloride ions only.
For mass moisture in mass one may observe a strong increase up to 29-30% compared to that of initial material. The moisture content in mass represents the water content in the material at the moment. It exceeds absorbability of water for all the materials. For primary contamination by chloride/sulphate ions and consequent mould fungi contamination this is connected with the formation of biofilm or so called biological membrane that adheres to, according to Costerton et al.[17] permanent surfaces or surfaces of other organisms. Biofilm, Chandra et al. [18], is a multicellular formation containing one or more microbial species or genera. According to many authors, among others Currie [19] it may contain bacteria and fungi as well as algae and protozoans. The colonisation of various surfaces by microbes is possible due to its adhesive properties. The structure of the formed biofilm is stabilised by polymeric substances so called EPS (extracellular polymeric substances). Biofilm, according to Zyska [20], forms complex multicellular structures in which numerous microorganism cells are surrounded by a mucus layer. Quoting Kolwzan [21], it microorganism cells are highly specialised to perform various functions and show different features than those of free cells. The formation of such clusters protect microbes from harmful effects of the external environment. This can make nutrients more available or increase water absorption. Thus, biofilm may exist under conditions where survival of single cells could be difficult or even impossible.
Fig. 1. Sample photographs ceramics-brick a) uncontaminated; contaminated by : (b) SO4-P.ch.; (c) SO4-C.h.
Fig. 2. Sample photographs ceramic-brick contaminated by: (a) Cl-C.h.; (b) Cl-P.ch.
Figures 1 and 2 illustrate a sample contaminated with bricks originally sulphate ions / with chloride and later as a result of subsequent contamination of mould fungi Penicillium/Cladosporium. Black spots visible in photographs are caused by fungi. They are discolorations or fungi themselves. One can observe that the larger spots are visible on the brick contaminated by sulphate ions. There are smaller discolorations on bricks contaminated by chloride ions, but this does not mean that fungi Penicillium/Cladosporium are not present (Table 2). On some specimens (Figure 1c) salinities are also visible (white spots).
The SEM images of the surfaces of the uncontaminated and chemical and biological contaminated bricks are shown in 3. Figure 3b to 3e clearly show the presence of mould fungi. In some cases (3e) spores or hyphae (3b, c and d) are visible. The results listed in Table 3 present surface analysis of test specimens. The figures indicate large C and O contents expressed in % of weight that reach from 23 to 44 for carbon, and from 32 to 46 for oxygen.
Fig. 3. SEM images of the masonry bricks (a) uncontaminated; contaminated of (b) SO4-P.ch; (c) SO4-C.h.; (d) Cl-P.ch.; (e) Cl-C.h.
Table 3. Mass moisture, absorbability of water of brick materials.
uncontaminated SO4-P.ch SO4-C.h. Cl-P.ch. Cl-C.h.
Element norm.C [wt.%] atom.C [at.%] norm.C [wt.%] atom.C [at.%] norm.C [wt.%] atom.C [at.%] norm.C [wt.%] atom.C [at.%] norm.C [wt.%] atom.C [at.%]
Oxygen 49.30 63.65 46.80 47.16 46.50 47.75 35.89 37.85 32.76 30.78
Carbon 2.26 3.89 27.70 37.19 23.40 32.02 27.76 39.00 44.27 55.40
Silicon 19.55 14.38 19.55 14.38 0.34 0.20 3.03 1.82 2.83 1.51
Aluminium 11.44 8.76 11.44 8.76 0.14 0.09 2.09 1.90 1.73 0.96
Sulfur 0.22 0.14 9.46 4.76 13.85 7.10 4.39 2.31 1.12 0.52
Calcium 7.05 3.63 1.08 0.43 0.14 0.06 3.45 1.45 3.66 1.37
Magnesium 2.27 1.93 7.03 4.67 10.65 7.20 0.77 0.53 0.44 0.27
Nitrogen - - 2.19 2.52 4.58 5.38 3.18 3.83 5.73 6.15
Sodium 0.64 0.57 0.28 0.20 0.13 0.09 10.69 7.84 1.04 0.68
Chlorine 0.05 0.03 0.03 0.01 - - 7.76 3.69 2.88 1.22
This means that fungi are present on the surface of test specimens along with organic metabolism products (organic acids). The biofilm layer is clearly visible on the brick surface. This membrane highly induces the variation in appearance and structure of the technical material, forming, for example, colour spots and stains and causing laminations or pitting Cwalina [22].
4. Conclusions
Based on the experiments carried out one may conclude that:
1. as a result of 24 -month exposure of bricks contaminated previously by chloride or sulphate ions their properties were altered due to consequential effect of biological environment,
2. primary chemical contamination of ceramic bricks by sulphate or chloride ions led to increased sustainability of this material to contamination by fungi Pénicillium or Cladosporium, whereas this effect was more clearly visible for bricks contaminated by sulphates. An increase of sustainability of this mineral substrate to microbial colonisation was connected, among other things, with pH decrease in the material due to chemical contamination, and
3. contamination by mould fungi and their physical presence caused that a bio film layer was formed, thus increasing brick moisture content in mass compared to its absorbability of water.
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