Cement Composites Biodeterioration
by Acidithiobacillus Thiooxidans
ALENA LUPTAKOVA1, ADRIANA ESTOKOVA2, MILOSLAV LUPTAK3
1Department of Mineral Biotechnology,
Institute of Geotechnics of Slovak Academy of Sciences,
Watsonova 45, Kosice, SK-040 01,
SLOVAK REPUBLIC
2Department of Material Engineering, Civil Engineering Faculty,
Technical University in Kosice,
Vysokoskolska 4, Kosice, SK-042 00,
SLOVAK REPUBLIC
3Institute of Materials and Quality Engineering,
Faculty of Materials, Metallurgy and Recycling,
Technical University in Kosice, Letná 9, 042 00 Košice,
SLOVAK REPUBLIC
Abstract: - The focus of this work was to study the biodeterioration of special cement composites by sulfur-
oxidizing bacteria Acidithiobacillus thiooxidans. The laboratory prepared cement composites that contained the
selected additives - silica fume (a secondary raw material) and zeolite (a natural raw material), as partial
replacements for the binder. The tests were carried out in laboratory conditions. During the experiments,
changes to the pH values and the Ca and Si concentrations were observed in the liquid phases. Based on the
achieved results, it can be concluded that concrete composites with partial replacement of the binder by silica
fume and zeolite have a higher resistance to biogenic sulfuric acid.
Key-Words: - cement composites, concrete, biodeterioration, biocorrosion, Acidithiobacillus thiooxidans, silica
fume, zeolite.
Received: March 29, 2024. Revised: August 29, 2024. Accepted: September 21, 2024. Published: October 29, 2024.
1 Introduction
The biodeterioration of building materials represents
a branch of science that focuses on the study of the
unwanted changes that are caused by the activity of
microorganisms (MO) on building materials, [1].
One of the most used building materials is concrete.
This is most commonly in the form of monolithic
structures or prefabricated elements. The concrete
biodeterioration caused by the biogenic sulphuric
acid is known as microbiologically influenced
concrete corrosion (MICC) or concrete
biocorrosion, [2]. In 1945 was conducted the initial
research on the influence of biogenic sulphuric acid
on the concrete corrosion process using the bacteria
Acidihiobacillus thiooxidans, [3].
Additional studies have supplemented and
expanded on the knowledge of the biocorrosion
process [4], [5]. The sulfuric acid produced by
Acidihiobacillus thiooxidans (A. thiooxidans) reacts
with the surface of the concrete converting the
cementation material into the main corrosive
products of biocorrosion - gypsum or ettringite.
Both mentioned products subsequently cause a loss
in the strength of the concrete.
Concrete is a composite material. Its main
components are cement, gravel aggregate and water.
It can contain different additives to improve its
properties such as treatability, plasticity, speed of
hardening, water permeability, resistance against
aggressive environments etc., [6]. Additives are the
mineral materials that are added to the concrete
during the mixing process. Fly ashes, blast furnace
slag, pigments, silica fume and zeolites all belong to
this group.
Silica fume is an industrial waste which is
formed during the production of crystalline silicon
or ferrosilicon in arc furnaces. Silica fumes
influence the porous structure of concrete, which
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DOI: 10.37394/232015.2024.20.50
Alena Luptakova, Adriana Estokova,
Miloslav Luptak
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Volume 20, 2024
then in turn enhances the concrete's hardness and
resistance to aggressive environments. The use of
these waste products as additives in the concrete
decreases their negative impact on the environment.
Additionally, they can contribute to improving the
resistibility of the prepared concrete composite.
Zeolites are crystalline aluminosilicates which
contain alkali and alkaline earth metals. Their use is
advantageous from an economic point of view due
to their natural abundance and low production costs.
The composites which contain zeolite harden faster
and have higher values of longstanding strength in
comparison with the cement composites based on
the blast furnace slag.
The aim of this work was to study the
biodeterioration process of cement composites by
the bacteria A. thiooxidans. The experiments
focused on the changes in pH values and Ca and Si
concentrations in the liquid phases. These changes
were occurring while the composite samples were
under the influence of biogenic acid. Cement
composites contained a binder which was partially
replaced by the chosen additives: silica fume (as the
secondary raw material) and zeolite (as a natural
raw material).
2 Materials and Methods
2.1 Microorganisms
The sulfur-oxidizing bacteria A. thiooxidans used in
the experiment was isolated from the acid mine
drainage (the Pech shaft, the Smolnik deposit,
Eastern Slovakia), [7]. A selective nutrient medium
for A. thiooxidans (pH 4.0) was applied [8] for the
isolation, cultivation, preparation of the active
bacterial culture of A. thiooxidans and for the
biodeterioration experiments.
2.2 Cement Composites Samples
Cement CEM I 42.5 N was used for the preparation
of the four studied cement composites samples (S-0,
S-Si, S-Si-Z and S-Z). The composition of the
samples was prepared with regard to the aggressive
environments in accordance with STN EN 206-1.
Zeolite and silica fumes were added to improve the
durability of concrete according to the appropriate
literature, [9]. The composition of the cement
composite samples is described in Table 1.
The prepared standardized concrete prisms with
dimensions of 100 x 100 x 400 mm were cured for
28 days in an aqueous environment and then cut into
small prisms with dimensions of 50 x 50 x 10 mm.
The test samples were gently abraded to remove
contaminant particles, sterilized in 70 % ethanol for
24 h, and dried at 80 °C to constant weight before
use in biodegradation experiments.
Table 1. Composition and labeling of cement
composite samples
Components
Cement composites samples
(calculation on 0.01 m3)
S-0
S-Z
CEM
I 42.5 N
(kg)
3.60
3.31
Water (L)
1.09
1.09
Zeolite (kg)
-
0.29
Silica fume
(kg)
-
-
S – sample, Si – silica fume, Z – zeolite
2.3 Study of Biodeterioration
The cement composite samples, containing four
various compositions (S-0, S-Si, S-Si-Z, and S-Z),
were placed into the liquid phase with bacteria A.
thiooxidans (S-0-At, S-Si-At, S-Si-Z-At, and S-Z-At
i.e. biotic conditions) and without bacteria (S-0-R,
S-Si-R, S-Si-Z-R, and S-Z-R i.e. reference abiotic
conditions). The volume of the bacteria inoculum
was 20 %. The volume ratio of the concrete sample
to the liquid phase was set to 1:10. The experiments
were carried out in glass jars (700 mL) covered by
cotton plugs in an aerobic atmosphere at laboratory
temperature. Bacterial inoculum was added at 7-day
intervals, over a period of 90 days to stimulate the
bacteria growth in the presence of the cement
composite samples. The experiments without
bacteria, which served as a reference abiotic
environment, proceeded the same way as the
experiment with bacteria. The change of pH, the
presence of bacteria as well as the concentrations of
calcium and silicon ions released, were measured in
leachates after each 7-day period.
2.4 Analytical Methods
The chemical composition of concrete samples and
leachates was analyzed before and after the
experiments by X-ray fluorescence analysis (XRF).
SPECTRO iQ II (Ametek, Germany) with SDD
silicon drift detector with resolution of 145 eV at
10.000 pulses was used for the analysis. The
samples were measured for 300 and 180 s at voltage
of 25 kV and 50 kV at currents of 0.5 and 1.0 mA
under a helium atmosphere by using the
standardized method of fundamental parameters. pH
changes were measured by pH meter PHM210
(MeterLab, France).
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3 Results and Discussion
3.1 The Changes in Calcium Concentration
Figure 1 and Figure 2 show the trend of the leaching
of calcium from the studied cement composites
throughout the duration of the experiment. All biotic
samples have been observed to contain significantly
higher concentrations of calcium in the leachates
(Figure 1) than in the abiotic samples (Figure 2).
The reason for the difference in the leached
concentration of calcium has to do with the activity
of the present bacterial culture. Bacteria A.
thiooxidans produced sulphuric acid which caused
the Ca to be leached out of the concrete to a higher
extent than in the experiments without bacteria.
From Figure 1 it is evident that there was a rapid
increase in leached calcium which occurred in the
presence of bacteria for the first 21 days of the
experiment (in the case of S-Si-Z-At until the 57th
day). Subsequently, the leaching process stabilized,
which is in accordance with the studied literature,
[10]. All studied biotic experiment samples record a
gradual increase in Ca concentration. In all abiotic
experiments, the initial leachability of Ca was from
95 to 80 mg/kg. After an observed gradual decrease,
the concentration of Ca stabilized until the end of
the experiment, when the concentration of Ca
achieved values of 18-25 mg/kg.
Fig. 1: The changes of Ca concentration – biotic
samples. (At – Acidithiobacillus thiooxidans)
The concentrations of leached calcium
compared to the total calcium in the concrete
composite before the experiments are shown in
Figure 3. The highest percentage of Ca leachability
of 7.03 % was achieved in the biotic sample S-Si-Z-
At (silica fume + zeolite). The lowest percentage
value 4.07 % of Ca leachability from the biotic
samples was observed in sample S-Z-At (zeolite).
The range of the percentage of leachability of Ca
from the concrete composites without the presence
of bacteria was 0.22 - 0.40 %. It is possible to claim
that the leachability of Ca under the influence of
bacteria was several times higher than in abiotic
conditions.
Fig. 2: The changes of Ca concentration – abiotic
samples. (R – reference abiotic conditions)
Fig. 3 Concentrations of leached Ca compared to
total calcium concentration in the concrete
composite
3.2 The Changes in Silica Concentration
Figure 4 and Figure 5 display the changes in the
leachability of silica during the whole experiment.
The highest increase of the Si concentration in the
liquid phase for biotic, as well as abiotic samples,
was observed after eight days. Subsequently, the
concentration of Si increased, later gradually
decreased, and finally decreased considerably at the
end of the experiment. This is most likely due to Si
0
100
200
300
400
500
600
700
800
900
1000
1100
020 40 60 80 100
Concentration of Ca (mg/kg)
Time (day)
S-0-At S-Si-At
S-Si-Z-At S-Z-At
0
20
40
60
80
100
120
020 40 60 80 100
Concentration of Ca (mg/kg)
Time (day)
S-0-R S-Si-R
S-Si-Z-R S-Z-R
4,36
5,72
7,03
4,07
0,22 0,23 0,4 0,27
0
1
2
3
4
5
6
7
8
S-0 S-Si S-Si-Z S-Z
Concentrations of leached Ca (%)
At - biotic conditions
R - reference abiotic
conditions
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precipitation. The final concentration of Si in all
samples was in the range of 500 - 590 mg/kg. The
largest recorded difference between the highest and
lowest detected Si concentrations was in sample S-
Z-At (zeolite). The highest concentrations were
measured on the 8th day and the lowest on the 90th
day. This fact can be explained by the properties of
the applied zeolite. Zeolite belongs to a group of
inorganic materials that contains a large amount of
active SiO2 and Al2O3, which has the potential to
react with Ca(OH)2 released by the hydration of
Portland concrete, [11].
Fig. 4: The changes of Si concentration – biotic
samples. (At – Acidithiobacillus thiooxidans)
Fig. 5: The changes of Si concentration – abiotic
samples. (R – reference abiotic conditions)
Figure 6 displays the concentrations of leached
Si compared to total Si concentration in all studied
concrete composite samples after the experiment
was completed (At - biotic conditions, R - abiotic
conditions). The highest percentage of Si
leachability was in abiotic sample S-0 (reference
sample without the replacement) with a value of 6.5
%, whereas the lowest percentage was found in
biotic sample S-Si (silica) with a value of 4.71 %.
Figure 4, Figure 5 and Figure 6 refer to the fact that
the applied nutrient medium had a fundamental
influence on the Si leachability. The presence of
bacteria most likely did not have a fundamental
influence on the leachability of Si.
Fig. 6: Concentrations of leached Si compared to
total silica concentration in the concrete composite
4 Conclusion
This contribution is focused on the study of the
influence of bacterially produced sulphuric acid on
concrete composites, which had their binder
partially replaced by chosen additives (silica fume
as the secondary raw material and zeolite as the
natural raw material). The leachability of Ca and Si
was observed in particular, and the following results
were achieved:
- Substantially higher concentrations of Ca were
measured in all the biotic samples than in the
abiotic samples. This is a result of the production
of sulphuric acid by the used bacteria A.
thiooxidans, which caused the leaching of Ca
from the concrete;
- The highest percentage of Ca leachability of 7.03
% was observed in sample S-Si-Z-At (silica fume
+ zeolite). Sample S-Z-At (zeolite) had the
lowest value of Ca leachability at 4.07 %;
0
200
400
600
800
1000
1200
1400
1600
1800
020 40 60 80 100
Concentration of Si (mg/kg)
Time (day)
S-0-At S-Si-At
S-Si-Z-At S-Z-At
0
200
400
600
800
1000
1200
1400
1600
020 40 60 80 100
Concentration of Si (mg/kg)
Time (day)
S-0-R S-Si-R
S-Si-Z-R S-Z-R
6,14
4,71
4,94
5,16
6,5
5,27 5,81
4,78
0
1
2
3
4
5
6
7
8
S-0 S-Si S-Si-Z S-Z
At - biotic conditions
R - reference abiotic conditions
Concentrations of leached Si (%)
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- The leachability of Ca under the influence of
bacteria was several times higher than in abiotic
conditions;
- The concentration of Si in leachates for all
studied samples (for biotic, as well as for
abiotic), after experiments were completed, was
in the range of 500 - 590 mg/kg. The achieved
results can most likely be explained by
understanding the properties of the applied
zeolite. Zeolite belongs to the aluminosilicate
group of minerals with a large amount of active
SiO2 and Al2O3, which has the potential to react
with Ca(OH)2 released by the hydration of
Portland concrete;
- The applied nutrient medium had a fundamental
influence on the leachability of Si. The presence
of bacteria most likely had no influence.
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Contribution of Individual Authors to the
Creation of a Scientific Article (Ghostwriting
Policy)
- Alena Luptakova has organized and executed the
experiments.
- Adriana Estokova processed and evaluated the
results.
- Miloslav Luptak executed the experiments.
Sources of Funding for Research Presented in a
Scientific Article or Scientific Article Itself
This work has been supported by the Slovak Grant
Agency for Science Grant No. 2/0108/23 and
Slovak Research and Development Agency under
the contract APVV-20-0140.
Conflict of Interest
The authors have no conflicts of interest to declare
that are relevant to the content of this article.
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Creative Commons Attribution License 4.0
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Volume 20, 2024