T. MELICHAR et al.: DURABILITY OF MATERIALS BASED ON A POLYMER-SILICATE MATRIX ...
751–758
DURABILITY OF MATERIALS BASED ON A
POLYMER-SILICATE MATRIX AND A LIGHTWEIGHT
AGGREGATE EXPOSED TO AGGRESSIVE INFLUENCES
COMBINED WITH HIGH TEMPERATURES
VZDR@LJIVOST MATERIALOV NA OSNOVI IZ
POLIMER-SILIKATNIH MATRIC IN LAHKEGA DODATKA,
IZPOSTAVLJENIH AGRESIVNIM VPLIVOM V KOMBINACIJI Z
VISOKIMI TEMPERATURAMI
Tomá{ Melichar, Jiøí Byd`ovský, Ámos Dufka
Brno University of Technology, Faculty of Civil Engineering, Veveøí 331/95, 602 00 Brno, Czech Republic
melichar.t@fce.vutbr.cz
Prejem rokopisa – received: 2016-07-15; sprejem za objavo – accepted for publication: 2017-03-16
doi:10.17222/mit.2016.190
The paper presents the results and findings of the research focused on an examination of progressive degradation of newly
developed composite materials. These materials consisted of a polymer-silicate matrix and a mix of fillers with a considerable
proportion of a porous aggregate. The matrix also contained a larger amount of alternative raw materials, in particular high-
temperature fly ash and blast furnace slag. Prepared mixes were tested after different periods of exposure to an aggressive
environment – for 45 d and 90 d (50 and 100 cycles). First, after 45 d and 90 d, reference materials (i.e., those not exposed to
aggressive influences) were tested. In parallel, tests were carried out with materials exposed to a solution of chloride ions and
subjected to cyclic freeze and thaw. The last mode of testing in this research included materials exposed to cyclic freeze and
thaw, chloride-ion solution and the consequent thermal load of up to 1000 °C. The level of degradation was evaluated by means
of physico-mechanical, physico-chemical and microstructural test methods. It was found that the exposure to cyclic freeze and
thaw, water and chloride ions has no considerable influence on the reduction of the thermal resistance of the developed mix
designs of polymer-silicate-based composites.
Keywords: durability, porous aggregate, polymer-silicate matrix, long-term exposure, chloride ions, water, frost, fire, micro-
structure
^lanek predstavlja rezultate in izsledke raziskave, osredoto~ene na preverjanje napredujo~ega slab{anja na novo razvitih kompo-
zitnih materialov. Ti materiali so sestavljeni iz polimer-silikatnih matric in me{anice polnil z znatnim dele`em poroznih
agregatov. Matrica je vsebovala tudi ve~jo koli~ino alternativnih surovih materialov, visokotemperaturni dimni{ki pepel in
`lindro. Pripravljene me{anice so bile testirane po razli~nih ~asih izpostavljanja agresivnemu okolju – 45 d in 90 d (v 50 in 100
ciklih). Najprej so bili, po 45 d in 90 d, testirani referen~ni materiali, tisti, ki niso bili izpostavljeni agresivnim vplivom.
Vzporedno pa so bila izvedena testiranja materialov, ki so bili izpostavljeni raztopini kloridnih ionov ter nato cikli~no
zamrznjeni in nato staljeni. Zadnji na~in testiranja v tej raziskavi je bilo izpostavljanje materialov cikli~nemu zamrzovanju in
taljenju, kloridni raztopini ionov in ter toplotni obremenitvi do 1000 °C. Stopnja degradacije je bila ocenjena glede na
fizikalno-mehanske, fizikalno-kemi~ne in mikrostrukturne testne metode. Ugotovljeno je bilo, da izpostavljenost cikli~nemu
zamrzovanje in taljenju, vodi in kloridnim ionom, nima ve~jega vpliva na zmanj{anje termi~ne odpornosti na razvite me{anice iz
polimer-silikatnih kompozitov.
Klju~ne besede: vzdr`ljivost, porozne me{anice, polimer-silikatna osnova, dalj{e izpostavljanje, kloridni ioni, voda, led, ogenj,
mikrostruktura
1 INTRODUCTION
Technical papers, stating results of the research
focused on the problems of the resistance of silicate
(cement) matrix based composites, focus mainly on an
assessment of the influences of individual adverse fac-
tors and aggressive environments. Scientists do not focus
on a synergic action of more than two types of adverse
influences, one of which is extremely high temperature.
Several factors are crucial for a gradual degradation of
polymer-silicate composites exposed to chloride ions,
frost and high temperature. The first of them is mecha-
nical deterioration of the composite caused by freeze-
thaw cycles together with the water containing chloride
ions. A water solution with chlorides penetrates through
the surface and subsequently deeper into the structure of
a composite material with a capillary-porous system.
Depending on the depth of the ingression of the men-
tioned solution, affected areas are damaged during the
temperatures changes above and below zero. The depth
of penetration depends on the components used, in parti-
cular, the material base of the matrix, the used additions,
their activities and the structure of the aggregate.
This problem is solved, in considerable detail, by J.
G. Jang et al.1 Apart from the influence of individual
factors, the authors also described a combination of
aggressive CO2 and Cl– ions, and it was proved that when
the two act in synergy, the penetration of Cl ions is
Materiali in tehnologije / Materials and technology 51 (2017) 5, 751–758 751
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS
UDK 67.017:620.17:620.192.47 ISSN 1580-2949
Original scientific article/Izvirni znanstveni ~lanek MTAEC9, 51(5)751(2017)
increased. This implies that the testing of a synergic
action of negative influences affecting a given material is
quite important because it is impossible to give an exact
prediction only on the basis of an evaluation of indi-
vidual aggressive substances. M. Maes et al.2 confirmed
that a replacement of Portland cement with blast-furnace
slag in amounts of 50 % and 70 % considerably in-
creases the resistance to the actions of Cl– and SO4–2. It is
also interesting that increasing the contents of sulfates in
a solution increases the attack of chlorides. On the other
hand, the concentration of chlorides has no influence on
the sulfate attack on the mortar with blast-furnace slag.
Slag generally has good resistance to sulfate attack,
which was proved by M. Maes et al.2, inter alia, with
negligible changes in the volume and expansion. This
finding is quite important from the viewpoint of a posi-
tive influence of blast-furnace slag on the resistance of a
cement matrix to extreme temperatures.
The presence of Cl– ions in silicates is also important
for a possible formation of Friedel’s salt – 3CaO·Al2O3·
·CaCl2·10H2O. This chemical compound can develop
from free Cl– ions, which bind to C3A or C4AF. However,
the reaction of the mentioned components is consider-
ably influenced by several factors. As A. Delagrave et
al.3 and D. Izquierdo et al.4, Q. Yuan5 and L. Tang6 state,
concentration of chloride ions, type of cement,
replacement of cement, temperature or water-cement
ratio are important. According to F. P. Glasser et al.7, a
penetration of chloride ions with the consequent
formation of Friedel’s salt can, inter alia, cause a gradual
filling of the porous structure of a given composite,
which eventually slows down the transportation of Cl–
ions. The filling of pores is critical particularly for the
thermal resistance where a porous structure is an
advantage. The thermal decomposition of Friedel’s salt is
also important, i.e., gases developed during the
dissociation, components remaining as residua and their
capability for a further reaction with water consequently
lead to an increase in the volume.
Durability of mortars with blast-furnace slag as the
filler is described by Santamaría-Vicario et al.8 The
research focused on the influence of a combination of
several adverse environments – frost with water, alter-
nating between humid and dry environment, simulation
of a marine environment or crystallization of salts and
gaseous SO2. Based on the results and findings, the
possibility of using slag as a replacement of the aggre-
gate was confirmed. The development and research of
mortars with blast-furnace slag resistant to fire up to a
temperature of 900 °C is presented by S. Aydin9. The
tests involving blast-furnace slag as a replacement of the
binder included mortars containing up to 80 % of the
slag. Pumice was used as the filler. Mortars with 40 % of
the slag showed the best test results. The residual com-
pressive strength of these mortars exposed to 900 °C was
44 %, after they were gradually cooled down. After rapid
cooling with water, the residual compressive strength of
the mortar was around 40 %. The replacement of a fine
aggregate with industrial by-products is a part of the
research described by I. Yüksel et al.10 The amount of
the substitution was from 10–50 %, with the subsequent
thermal load of up to 800 °C at the age of 90 d. A posi-
tive influence of the replacement of the commonly used
dense aggregate with byproducts of the energy and
foundry industry was unambiguously proved. The
bottom ash showed the best results. One of the few
publications, in which the authors provide the results of a
research focused on the synergic action of high
temperature and adverse environment (in particular
CO2), was published by G. Yuan and Q. Li11. The authors
focus on the problems of concrete with various
water-cement ratios exposed to temperatures of up to 700
°C. One of the subsequent testing methods was the
exposure to an environment with a higher concentration
of CO2. The aim of the research presented by G. Yuan
and Q. Li11 was the verification of the influence of a
possible surface treatment of the tested concrete after its
exposure to heat. The results show that as the exposure
temperature grows, the resistance to carbonization
decreases.
2 METHODOLOGY OF EXPERIMENTAL WORK
As the aim of the research was to design a material
resistant to adverse environmental influences and
possible fire at the same time, the selected matrix
contained an increased amount of blast-furnace slag and
high-temperature fly ash. Fly ash as a substitution binder
increasing the thermal resistance was researched by A.
Nadeem et al.12 Microsilica was used as a supporting
addition and stabilizing component; its positive effect in
cement-based composites on the resistance to high
temperatures was proven, for example, by T. Harun and
C. Ahmet.13 Two types of aggregate were used. The
coarser fraction of 1–2 mm was amphibolite, which is
mined as a primary raw material. The fine-grained
residue from washing the aggregate, produced as a
by-product of adjusting the granulometric composition
of the mined amphibolite, was used. The remaining part
– a fine fraction of 0–1 mm – was fly-ash agloporite; the
dominant part of agloporite is an energy-industry
by-product – fly ash. As agloporite is created, through a
self-burning process, from alternative raw-material
resources, it can be characterized as an advantageous and
cheap raw material, which is relatively environmentally
friendly. The suitability of agloporite as a filler for
materials with an assumed thermal resistance can be
presumed, for example, on the basis of the results stated
by V. ^erný and [. Keprdová.14 Mix designs of tested
composite materials are listed in Table 1. Agloporite was
saturated with water before its application in the mix.
This fact was taken into account when correcting the
water-cement ratio, which was adjusted to achieve good
T. MELICHAR et al.: DURABILITY OF MATERIALS BASED ON A POLYMER-SILICATE MATRIX ...
752 Materiali in tehnologije / Materials and technology 51 (2017) 5, 751–758
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS
workability of the fresh mix (a slump of around 160
mm).
Out of each mix design, four sets of test specimens of
(40 × 40 × 160) mm were made. The first and the second
sets were treated in standardized conditions; then, after
28 d of maturing, the specimens were exposed to an
adverse environment. In the adverse environment, the
temperature was cyclically changing (above and below
zero), combined with a saturation of the solution with
chloride ions (in accordance with ^SN EN17). After 50
cycles (and after 45 d elapsed from the standardized
maturation), half of the specimens were subjected to
tests of strength characteristics. The other half of the test
specimens were exposed to temperatures of (22, 400,
600 and 1000) °C. The rate of the temperature increase
was around 10 °C min–1 with an isothermal dwell time of
90 min and slow cooling down. A similar procedure was
also applied for the third and fourth set, where the test
conditions were different regarding the number of
cycles: 100 cycles were made in an adverse environment
so that the specimens could be tested after 90 d. It is
important to emphasize that the testing was carried out
after 45 d or 90 d; however, the cycles were counted after
the standardized age of 28 d. The reason for this was the
exposure of the test specimens to the adverse envi-
ronment after the maturing process. The end of the
cyclical exposure at the ages of 45 d or 90 d simulated
the early age of a real structure.
T. MELICHAR et al.: DURABILITY OF MATERIALS BASED ON A POLYMER-SILICATE MATRIX ...
Materiali in tehnologije / Materials and technology 51 (2017) 5, 751–758 753
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS
Figure 4: Bending tensile strengths of mixtures MBS and MFA after
45 d and 90 d (R – temperature exposure; Cl – combination of
chloride ions, frost and exposure to extreme temperatures)
Figure 2: Percentage change of compressive strength due to
chloride-ion solution and frost attack – weight change of mixtures
MBS and MFA after 45 d and 90 d
Figure 3: Change of temperature resistance (compressive strength)
due to chloride-ion solution and frost attack – weight change of mix-
tures MBS and MFA after 45 d and 90 d
Figure 1: Compressive strengths of mixtures MBS and MFA after 45
d and 90 d (R – temperature exposure; Cl – combination of chloride
ions, frost and exposure to extreme temperatures)
Table 1: Composition of mixtures MBS and MFA
Component Unit Mixture
MBS MFA
Cement kg m–3 443 443
Blast furnace slag kg m–3 251 –
Fly ash kg m–3 – 238
Vinyl acetate copolymer % (wC+FBS, FA) 3 3
Microsillica % (wC+FBS, FA) 7 7
Amphibolite (by-product)
<0,063 mm kg m
–3 33 33
Porous aggregate 0–1 mm kg m–3 641 641
Amphibolite 1–2 mm kg m–3 792 792
Polypropylene fibres kg m–-3 1.1 1.1
Water kg m–3 193 201
increased. This implies that the testing of a synergic
action of negative influences affecting a given material is
quite important because it is impossible to give an exact
prediction only on the basis of an evaluation of indi-
vidual aggressive substances. M. Maes et al.2 confirmed
that a replacement of Portland cement with blast-furnace
slag in amounts of 50 % and 70 % considerably in-
creases the resistance to the actions of Cl– and SO4–2. It is
also interesting that increasing the contents of sulfates in
a solution increases the attack of chlorides. On the other
hand, the concentration of chlorides has no influence on
the sulfate attack on the mortar with blast-furnace slag.
Slag generally has good resistance to sulfate attack,
which was proved by M. Maes et al.2, inter alia, with
negligible changes in the volume and expansion. This
finding is quite important from the viewpoint of a posi-
tive influence of blast-furnace slag on the resistance of a
cement matrix to extreme temperatures.
The presence of Cl– ions in silicates is also important
for a possible formation of Friedel’s salt – 3CaO·Al2O3·
·CaCl2·10H2O. This chemical compound can develop
from free Cl– ions, which bind to C3A or C4AF. However,
the reaction of the mentioned components is consider-
ably influenced by several factors. As A. Delagrave et
al.3 and D. Izquierdo et al.4, Q. Yuan5 and L. Tang6 state,
concentration of chloride ions, type of cement,
replacement of cement, temperature or water-cement
ratio are important. According to F. P. Glasser et al.7, a
penetration of chloride ions with the consequent
formation of Friedel’s salt can, inter alia, cause a gradual
filling of the porous structure of a given composite,
which eventually slows down the transportation of Cl–
ions. The filling of pores is critical particularly for the
thermal resistance where a porous structure is an
advantage. The thermal decomposition of Friedel’s salt is
also important, i.e., gases developed during the
dissociation, components remaining as residua and their
capability for a further reaction with water consequently
lead to an increase in the volume.
Durability of mortars with blast-furnace slag as the
filler is described by Santamaría-Vicario et al.8 The
research focused on the influence of a combination of
several adverse environments – frost with water, alter-
nating between humid and dry environment, simulation
of a marine environment or crystallization of salts and
gaseous SO2. Based on the results and findings, the
possibility of using slag as a replacement of the aggre-
gate was confirmed. The development and research of
mortars with blast-furnace slag resistant to fire up to a
temperature of 900 °C is presented by S. Aydin9. The
tests involving blast-furnace slag as a replacement of the
binder included mortars containing up to 80 % of the
slag. Pumice was used as the filler. Mortars with 40 % of
the slag showed the best test results. The residual com-
pressive strength of these mortars exposed to 900 °C was
44 %, after they were gradually cooled down. After rapid
cooling with water, the residual compressive strength of
the mortar was around 40 %. The replacement of a fine
aggregate with industrial by-products is a part of the
research described by I. Yüksel et al.10 The amount of
the substitution was from 10–50 %, with the subsequent
thermal load of up to 800 °C at the age of 90 d. A posi-
tive influence of the replacement of the commonly used
dense aggregate with byproducts of the energy and
foundry industry was unambiguously proved. The
bottom ash showed the best results. One of the few
publications, in which the authors provide the results of a
research focused on the synergic action of high
temperature and adverse environment (in particular
CO2), was published by G. Yuan and Q. Li11. The authors
focus on the problems of concrete with various
water-cement ratios exposed to temperatures of up to 700
°C. One of the subsequent testing methods was the
exposure to an environment with a higher concentration
of CO2. The aim of the research presented by G. Yuan
and Q. Li11 was the verification of the influence of a
possible surface treatment of the tested concrete after its
exposure to heat. The results show that as the exposure
temperature grows, the resistance to carbonization
decreases.
2 METHODOLOGY OF EXPERIMENTAL WORK
As the aim of the research was to design a material
resistant to adverse environmental influences and
possible fire at the same time, the selected matrix
contained an increased amount of blast-furnace slag and
high-temperature fly ash. Fly ash as a substitution binder
increasing the thermal resistance was researched by A.
Nadeem et al.12 Microsilica was used as a supporting
addition and stabilizing component; its positive effect in
cement-based composites on the resistance to high
temperatures was proven, for example, by T. Harun and
C. Ahmet.13 Two types of aggregate were used. The
coarser fraction of 1–2 mm was amphibolite, which is
mined as a primary raw material. The fine-grained
residue from washing the aggregate, produced as a
by-product of adjusting the granulometric composition
of the mined amphibolite, was used. The remaining part
– a fine fraction of 0–1 mm – was fly-ash agloporite; the
dominant part of agloporite is an energy-industry
by-product – fly ash. As agloporite is created, through a
self-burning process, from alternative raw-material
resources, it can be characterized as an advantageous and
cheap raw material, which is relatively environmentally
friendly. The suitability of agloporite as a filler for
materials with an assumed thermal resistance can be
presumed, for example, on the basis of the results stated
by V. ^erný and [. Keprdová.14 Mix designs of tested
composite materials are listed in Table 1. Agloporite was
saturated with water before its application in the mix.
This fact was taken into account when correcting the
water-cement ratio, which was adjusted to achieve good
T. MELICHAR et al.: DURABILITY OF MATERIALS BASED ON A POLYMER-SILICATE MATRIX ...
752 Materiali in tehnologije / Materials and technology 51 (2017) 5, 751–758
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS
workability of the fresh mix (a slump of around 160
mm).
Out of each mix design, four sets of test specimens of
(40 × 40 × 160) mm were made. The first and the second
sets were treated in standardized conditions; then, after
28 d of maturing, the specimens were exposed to an
adverse environment. In the adverse environment, the
temperature was cyclically changing (above and below
zero), combined with a saturation of the solution with
chloride ions (in accordance with ^SN EN17). After 50
cycles (and after 45 d elapsed from the standardized
maturation), half of the specimens were subjected to
tests of strength characteristics. The other half of the test
specimens were exposed to temperatures of (22, 400,
600 and 1000) °C. The rate of the temperature increase
was around 10 °C min–1 with an isothermal dwell time of
90 min and slow cooling down. A similar procedure was
also applied for the third and fourth set, where the test
conditions were different regarding the number of
cycles: 100 cycles were made in an adverse environment
so that the specimens could be tested after 90 d. It is
important to emphasize that the testing was carried out
after 45 d or 90 d; however, the cycles were counted after
the standardized age of 28 d. The reason for this was the
exposure of the test specimens to the adverse envi-
ronment after the maturing process. The end of the
cyclical exposure at the ages of 45 d or 90 d simulated
the early age of a real structure.
T. MELICHAR et al.: DURABILITY OF MATERIALS BASED ON A POLYMER-SILICATE MATRIX ...
Materiali in tehnologije / Materials and technology 51 (2017) 5, 751–758 753
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS
Figure 4: Bending tensile strengths of mixtures MBS and MFA after
45 d and 90 d (R – temperature exposure; Cl – combination of
chloride ions, frost and exposure to extreme temperatures)
Figure 2: Percentage change of compressive strength due to
chloride-ion solution and frost attack – weight change of mixtures
MBS and MFA after 45 d and 90 d
Figure 3: Change of temperature resistance (compressive strength)
due to chloride-ion solution and frost attack – weight change of mix-
tures MBS and MFA after 45 d and 90 d
Figure 1: Compressive strengths of mixtures MBS and MFA after 45
d and 90 d (R – temperature exposure; Cl – combination of chloride
ions, frost and exposure to extreme temperatures)
Table 1: Composition of mixtures MBS and MFA
Component Unit Mixture
MBS MFA
Cement kg m–3 443 443
Blast furnace slag kg m–3 251 –
Fly ash kg m–3 – 238
Vinyl acetate copolymer % (wC+FBS, FA) 3 3
Microsillica % (wC+FBS, FA) 7 7
Amphibolite (by-product)
<0,063 mm kg m
–3 33 33
Porous aggregate 0–1 mm kg m–3 641 641
Amphibolite 1–2 mm kg m–3 792 792
Polypropylene fibres kg m–-3 1.1 1.1
Water kg m–3 193 201
3 RESULTS
The diagrams below show the dependency of indivi-
dual observed parameters on the exposure to aggressive
environments and high temperatures, including their
combination (Figures 1 to 6). The first compressive
strength and tensile bending strength were examined.
The first diagram of a given set – observed parameters
(Figures 1 to 4) – shows the development of the above-
mentioned parameters in a given environment and at a
given temperature (labeling: R – with no aggressive ex-
posure, Cl – exposed to a solution of chlorides and frost).
The second diagram of a given set shows the percentage
changes of a particular parameter (Figures 2 and 5). The
last diagram of a given parameter (Figures 3 and 6)
shows the development of the temperature resistance
(which is characterized by the percentage decrease of a
given parameter). The curves presented as a solid line
(dash line) denote mix designs MBS (MFA), i.e., the
binder modified with blast-furnace slag (high-tempe-
rature fly ash).
Due to the chloride-ion solution and frost, failures are
possible even inside the composite. The formation of
cracks is the most likely failure. One of the key methods
of the assessment of the structure of a material exposed
to high temperatures is X-ray tomography (and CT). The
CT examination focused on the presence of cracks, in
particular, their number, width and orientation. It was
important to determine where the cracks were found: the
matrix, the aggregate or the transition zone. The location
of cracks is also important: close to the surface or in the
inner structure. Figures 7 to 10 show the test specimens
exposed to adverse conditions. To identify and evaluate
phase changes, an X-ray diffraction analysis was used
(hereinafter referred to as XRD). The observed para-
meters were phase changes and the formation of new
chemical compounds as products of the reaction of
T. MELICHAR et al.: DURABILITY OF MATERIALS BASED ON A POLYMER-SILICATE MATRIX ...
754 Materiali in tehnologije / Materials and technology 51 (2017) 5, 751–758
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS
Figure 8: CT picture – slice of MBS-45/Cl (45 d, Cl – exposure to
chloride solution and frost environment, 50 cycles), exposure to
1000 °C
Figure 6: Change of temperature resistance (bending tensile strength)
due to chloride-ion solution and frost attack – weight change of
mixtures MBS and MFA after 45 d and 90 d
Figure 7: CT picture – slice of MBS-45/R (45 d, R – reference sample
without chloride solution and frost environment), exposure to 1000 °C
Figure 5: Percentage change of bending tensile strength due to chlo-
ride-ion solution and frost attack – weight change of mixtures MBS
and MFA after 45 d and 90 d
chlorides with the matrix of a composite (Table 2). To
make the picture complete, electron microscopy was
used (hereinafter referred to as SEM). SEM focused on
the formation of micro-cracks and the products related to
the crystallization of chloride ions or their residua
(Figures 11 and 12).
Table 2: XRD – mineralogical composition of mixtures MBS and
MFA – selected samples
Mixture-age/
environment,
temperature
Identified components
MBS-90/R,
22
portlandite, calcite, -quartz, ettringite, mullite,
chlorite, actinolite, anorthite, hematite,
akermanite, merwinite, gehlenite, CSH,
amorphous phase
MBS-90/R,
1000
-quartz, mullite, chlorite, actinolite, anorthite,
hematite, akermanite, merwinite, wolastonite,
amorphous phase
MBS-90/Cl,
22
portlandite, calcite,  -quartz, ettringite,
mullite, chlorite, hematite, akermanite,
actinolite, wolastonite, gehlenite, biotite CSH,
amorphous phase
MBS-90/Cl,
1000
-quartz, mullite, actinolite, anorthite, hematite,
gehlenite, amorphous phase wolastonite
MFA-90/R,
22
portlandite, calcite, -quartz, ettringite, mullite,
chlorite, actinolite, anorthite, hematite, biotite
CSH, amorphous phase
MFA-90/R,
1000
-quartz, mullite, chlorite, actinolite,
amorphous phase, anorthite, hematite,
wolastonite
MFA-90/Cl,
22
portlandite, ettringite, mullite, calcite, -quartz,
anorthite, biotite, hematite CSH, amorphous
phase
MFA-90/Cl,
1000
-quartz, mullite, amorphous phase, anorthite,
hematite, wolastonite
4 DISCUSSION
The diagrams (Figures 1 to 6) show the development
of individual parameters and differences between the
tested mix designs at a given age and exposed to a given
environment.
Reference materials MBS-90 and MFA-90 showed
compressive strengths of 48 N mm–2 and 45 N mm–2. As
the diagram shows (Figure 1), the compressive strength
decreases more considerably after an exposure to an
aggressive environment. This fact is supported by the test
results of the materials stored in laboratory conditions (in
T. MELICHAR et al.: DURABILITY OF MATERIALS BASED ON A POLYMER-SILICATE MATRIX ...
Materiali in tehnologije / Materials and technology 51 (2017) 5, 751–758 755
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS
Figure 11: Microstructure of MBS-45/Cl (45 d, Cl – exposure to
chloride solution and frost environment, 50 cycles), exposure to
1000 °C, 5000× magnification
Figure 9: CT picture – slice of MBS-90/Cl (90 d, Cl – exposure to
chloride solution and frost environment, 100 cycles), exposure to
1000 °C
Figure 10: CT picture – slice of MFA-90/Cl (90 d, Cl – exposure to
chloride solution and frost environment, 100 cycles), exposure to
1000 °C
3 RESULTS
The diagrams below show the dependency of indivi-
dual observed parameters on the exposure to aggressive
environments and high temperatures, including their
combination (Figures 1 to 6). The first compressive
strength and tensile bending strength were examined.
The first diagram of a given set – observed parameters
(Figures 1 to 4) – shows the development of the above-
mentioned parameters in a given environment and at a
given temperature (labeling: R – with no aggressive ex-
posure, Cl – exposed to a solution of chlorides and frost).
The second diagram of a given set shows the percentage
changes of a particular parameter (Figures 2 and 5). The
last diagram of a given parameter (Figures 3 and 6)
shows the development of the temperature resistance
(which is characterized by the percentage decrease of a
given parameter). The curves presented as a solid line
(dash line) denote mix designs MBS (MFA), i.e., the
binder modified with blast-furnace slag (high-tempe-
rature fly ash).
Due to the chloride-ion solution and frost, failures are
possible even inside the composite. The formation of
cracks is the most likely failure. One of the key methods
of the assessment of the structure of a material exposed
to high temperatures is X-ray tomography (and CT). The
CT examination focused on the presence of cracks, in
particular, their number, width and orientation. It was
important to determine where the cracks were found: the
matrix, the aggregate or the transition zone. The location
of cracks is also important: close to the surface or in the
inner structure. Figures 7 to 10 show the test specimens
exposed to adverse conditions. To identify and evaluate
phase changes, an X-ray diffraction analysis was used
(hereinafter referred to as XRD). The observed para-
meters were phase changes and the formation of new
chemical compounds as products of the reaction of
T. MELICHAR et al.: DURABILITY OF MATERIALS BASED ON A POLYMER-SILICATE MATRIX ...
754 Materiali in tehnologije / Materials and technology 51 (2017) 5, 751–758
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS
Figure 8: CT picture – slice of MBS-45/Cl (45 d, Cl – exposure to
chloride solution and frost environment, 50 cycles), exposure to
1000 °C
Figure 6: Change of temperature resistance (bending tensile strength)
due to chloride-ion solution and frost attack – weight change of
mixtures MBS and MFA after 45 d and 90 d
Figure 7: CT picture – slice of MBS-45/R (45 d, R – reference sample
without chloride solution and frost environment), exposure to 1000 °C
Figure 5: Percentage change of bending tensile strength due to chlo-
ride-ion solution and frost attack – weight change of mixtures MBS
and MFA after 45 d and 90 d
chlorides with the matrix of a composite (Table 2). To
make the picture complete, electron microscopy was
used (hereinafter referred to as SEM). SEM focused on
the formation of micro-cracks and the products related to
the crystallization of chloride ions or their residua
(Figures 11 and 12).
Table 2: XRD – mineralogical composition of mixtures MBS and
MFA – selected samples
Mixture-age/
environment,
temperature
Identified components
MBS-90/R,
22
portlandite, calcite, -quartz, ettringite, mullite,
chlorite, actinolite, anorthite, hematite,
akermanite, merwinite, gehlenite, CSH,
amorphous phase
MBS-90/R,
1000
-quartz, mullite, chlorite, actinolite, anorthite,
hematite, akermanite, merwinite, wolastonite,
amorphous phase
MBS-90/Cl,
22
portlandite, calcite,  -quartz, ettringite,
mullite, chlorite, hematite, akermanite,
actinolite, wolastonite, gehlenite, biotite CSH,
amorphous phase
MBS-90/Cl,
1000
-quartz, mullite, actinolite, anorthite, hematite,
gehlenite, amorphous phase wolastonite
MFA-90/R,
22
portlandite, calcite, -quartz, ettringite, mullite,
chlorite, actinolite, anorthite, hematite, biotite
CSH, amorphous phase
MFA-90/R,
1000
-quartz, mullite, chlorite, actinolite,
amorphous phase, anorthite, hematite,
wolastonite
MFA-90/Cl,
22
portlandite, ettringite, mullite, calcite, -quartz,
anorthite, biotite, hematite CSH, amorphous
phase
MFA-90/Cl,
1000
-quartz, mullite, amorphous phase, anorthite,
hematite, wolastonite
4 DISCUSSION
The diagrams (Figures 1 to 6) show the development
of individual parameters and differences between the
tested mix designs at a given age and exposed to a given
environment.
Reference materials MBS-90 and MFA-90 showed
compressive strengths of 48 N mm–2 and 45 N mm–2. As
the diagram shows (Figure 1), the compressive strength
decreases more considerably after an exposure to an
aggressive environment. This fact is supported by the test
results of the materials stored in laboratory conditions (in
T. MELICHAR et al.: DURABILITY OF MATERIALS BASED ON A POLYMER-SILICATE MATRIX ...
Materiali in tehnologije / Materials and technology 51 (2017) 5, 751–758 755
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS
Figure 11: Microstructure of MBS-45/Cl (45 d, Cl – exposure to
chloride solution and frost environment, 50 cycles), exposure to
1000 °C, 5000× magnification
Figure 9: CT picture – slice of MBS-90/Cl (90 d, Cl – exposure to
chloride solution and frost environment, 100 cycles), exposure to
1000 °C
Figure 10: CT picture – slice of MFA-90/Cl (90 d, Cl – exposure to
chloride solution and frost environment, 100 cycles), exposure to
1000 °C
diagram "22"). A combination of frost and chloride ions
caused a decrease in the strength of 27.5 % (MBS-90Cl)
and 29.6 % (MFA-90Cl). These values can be assessed
as adequate for the given type of material (i.e., the
material with a porous aggregate) after a given number
of cycles. The thermal resistance (a relative decrease in
the compressive strength) of the materials in individual
environments after being exposed to 1000 °C was
approximately 64–69 % (72–78 %) for the reference
samples (the samples exposed to the aggressive envi-
ronment). It is interesting that slag (i.e., MBS) showed
better results than the other reference material; however,
after the exposure to the aggressive environment and
high temperature, fly ash was better (i.e., MFA). For
illustration, MBS-90/Cl (MFA-90/Cl) showed a decrease
in the compressive strength of 75.1 % (74.1 %; Figure
2). A slight increase in the thermal resistance developed
over time in spite of the higher number of cycles in the
aggressive environment. The only exception was
MFA-90/Cl. An evaluation of the relative change in the
thermal resistance caused by the aggressive environment
shows an irregular development of the curves (Figure 3).
This is particularly clear for temperatures of 600 °C and
above. It is evident that the exposure to an aggressive
environment and 1000 °C caused a decrease in the
observed parameter of MBS (MFA) of approximately
11 % (2.5–7.2 %).
Further, the bending tensile strength was evaluated.
The differences are less obvious compared to the
development of the compressive strength (Figures 1 and
4). The increase in the bending strength in time was also
less considerable than the increase in the compressive
strength. The bending strengths of the test specimens not
exposed to aggressive environments and a thermal load
were from 7.3 N mm–2 to 7.6 N mm–2 (6.9 N mm–2 to
7.2 N mm–2) for mix designs MBS (MFA). After the ex-
posure of the samples to the aggressive environment with
chloride ions, the decrease was 12.6 % for MBS-90 and
13.9 % for MFA-90.
The decrease in the tensile bending strength caused
by the exposure to aggressive environments is then much
lower than that of the compressive strength. The negative
impact on the thermal resistance was also smaller. The
decrease in the tensile bending strength was 65.8 %
(62.3 %) for MBS-90/R (MFA-90/R) after the exposure
to 1000 °C (Figure 5). These facts imply that the substi-
tution of the primary binder with fly ash had a more
positive effect from the viewpoint of a combined ex-
posure involving an aggressive environment and a ther-
mal load. On the other hand, comparing the changes in
the thermal resistance in time and after the exposure to
adverse environments shows (Figure 6) that blast-fur-
nace slag had better results (MBS). The reduction in the
thermal resistance after the exposure to 1000 °C was
5.3 % for MBS-90/Cl-R and 6.1 % for MFA/Cl-R. The
reduction in the thermal resistance of MFA after the
exposure to 600 °C is also interesting for both tested
ages. It can be assumed that used high-temperature fly
ash contains components that react with chloride
solutions, possibly only during the thermal load. It could
also be a synergy reaction of both mentioned influences.
The synergy effect of an aggressive environment and
extreme temperatures causes a considerable degradation
of the structures of the materials based on a silicate
matrix and a porous aggregate. The given case is con-
firmed with the results of physico-mechanical tests of
materials MBS and MFA. The CT examination proved
the above character of the crack changes after the expo-
sure to the aggressive environment (chlorides and frost)
and the subsequent extreme thermal load. On the refe-
rence materials, only a small amount of randomly
oriented cracks was identified (Figure 7). The cracks
were rather small, i.e., with a smaller width. These
cracks mostly did not reach the transition zone between
the matrix and dense aggregate. On the contrary, the
number of cracks of the materials exposed to the aggres-
sive environment was larger (Figures 8 to 10). An
increase in the width and number of the cracks is evident
as the number of aggressive cycles and age of the sam-
ples grow. However, the increase was not considerable.
The orientation of the cracks was easily observable; the
cracks pointed towards the center of a test specimen
(Figures 8 and 9). The width and number of the cracks
and more cracks in the transit zone between the dense
aggregate and the matrix were evident compared to the
reference materials.
The last representative sample was FMA-60/Cl (Fig-
ure 10). It is interesting that its cracks are more close to
the surface, with an orientation similar to that of MBS.
Chloride ions combined with frost and the subsequent
thermal shock damaged more considerably the surface
areas of MFA, whereas MBS was damaged more evenly
throughout the whole structure.
T. MELICHAR et al.: DURABILITY OF MATERIALS BASED ON A POLYMER-SILICATE MATRIX ...
756 Materiali in tehnologije / Materials and technology 51 (2017) 5, 751–758
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS
Figure 12: Microstructure of MBS-90/Cl (90 days, Cl – exposure to
chloride solution and frost environment, 100 cycles), exposure to
1000 °C, 5000× magnification
The XRD analysis was used for the identification of
crystal phases and their changes. XRD did not identify
Friedel’s salt in any of the tested specimens. The crucial
factor of the formation of this chemical compound is the
temperature, which is, inter alia, mentioned by Dela-
grave et al.3, Izquierdo et al.4, Yuan5 and Tang6. It is then
evident that the damage of the structure caused by the
combination of frost and the solution with chloride ions
is purely mechanical. The salt in the solution – NaCl – is
transported into the porous structure of the composite by
equalizing the concentration gradient. Sudden changes of
the temperatures above and below zero then cause the
crystallization of the salt and the change of the phase of
water, which necessarily causes a decrease in the me-
chanical properties of the given material. This corres-
ponds with the findings determined with CT. As regards
the changes in the structures of the analyzed materials, a
decomposition of chemical compounds (in particular
mineralogical phases) typical for silicates and the used
aggregate, due to the increasing temperature, was ob-
served. The development shows peaks with a decreasing
intensity and a gradual ceasing of portlandite, calcite and
CSH phases. At temperatures over 600 °C, mew phases
were observed (like -C2S).
SEM together with an element analysis showed the
presence of Cl– ions in some areas. Microcracks and the
degree of decomposition of the hydration products of the
matrix or the changes in the structure of the used aggre-
gate were marked, as shown in Figures 11 and 12.
Almost no failures were observable in the transit zone
between the porous aggregate (agloporite) and the
matrix. As regards the age of the tested materials/number
of cycles, no considerable differences in the microstruc-
ture were observed. A 5000× magnification clearly
shows a degraded polymer-silicate matrix. SEM images
clearly show spherical particles of fly ash also in MBS.
This was caused by an imperfect manufacturing process
of agloporite, during which not all granules (for the
production of the aggregate) were perfectly compacted
and fired. However, as this fly ash had gone through the
thermic process twice, it is almost an inert filler from the
viewpoint of high temperature. Only few microscopic
cracks were observed in the matrix.
5 CONCLUSIONS
The influence of a combination of an aggressive
environment (chloride solution and freeze-thaw cycles)
and a thermal load (of up to 1000 °C) was tested and
analyzed in detail on newly designed materials as it is
not a thoroughly examined area. Fly-ash agloporite is a
promising aggregate and its influence on polymer-sili-
cate materials is still not quite clear. The advantage of
agloporite is its thermal resistance and very good
interaction with a polymer-silicate matrix. However, an
exposure to cyclic changing of temperatures above and
below zero, intensified by a salt solution, makes the use
of the porous aggregate difficult. Blast-furnace slag
(MBS) and fly ash (MFA) were used for a modification
of the matrix composition. Physico-chemical and micro-
structural analyses proved that the action of the
above-mentioned environment disturbs the structures of
MBS and MFA in a mechanical way, causing an expan-
sion due to the change of the phase of water or crystalli-
zation of salt rather than the formation of new chemical
compounds. The extreme temperature then only inten-
sifies these phenomena by degrading the structures, in
particular that of the matrix. It was proved that CT is
crucial for the explanation of the changes/failures of the
inner structure. This analytical method is quite suitable
for examining the three-dimensional structure of a given
material. It is particularly applicable for revealing va-
rious cracks, their orientation, localization or number.
The tested materials have a large potential for future
research. An examination of the behavior of the mate-
rials over a longer time (e.g., 180 d and 360 d) would
also be very interesting.
Acknowledgements
This paper has been worked out with the financial
support of The Czech Science Foundation (GA^R),
project GA15-07657S, "Study of kinetics of processes
occurring in the composite system at extreme tem-
peratures and exposed to an aggressive environment", as
well as under project No. LO1408 "AdMaS UP –
Advanced Materials, Structures and Technologies",
supported by the Ministry of Education, Youth and
Sports under the National Sustainability Programme I.
6 REFERENCES
1 J. G. Jang, H. J. Kim, H. K. Kim, H. K. Lee, Resistance of coal
bottom ash mortar against the coupled deterioration of carbonation
and chloride penetration, Materials & Design, 93 (2016), 160–167,
doi:10.1016/j.matdes.2015.12.074
2 M. Maes, N. De Belie, Resistance of concrete and mortar against
combined attack of chloride and sodium sulphate, Cement and Con-
crete Composites, 53 (2014), 59–72, doi:10.1016/j.cemconcomp.
2014.06.013
3 A. Delagrave, J. Marchand, J. P. Ollivier, S. Julien, K. Hazrati,
Chloride binding capacity of various hydrated cement paste systems,
Advanced Cement Based Materials, 6 (1997), 28–35, doi:
10.1016/S1065-7355(97)90003-1
4 D. Izquierdo, C. Alonso, C. Andrade, M. Castellote, Potentiostatic
determination of chloride threshold values for rebar depassivation –
experimental and statistical study, Electrochim. Acta, 49 (2004)
17–18, 2731–2739, doi:10.1016/j.electacta.2004.01.034
5 Q. Yuan, Fundamental studies on test methods for the transport of
chloride ions in cementitious materials, Doctoral Thesis, Ghent,
Ghent University, 2009
6 L. Tang, Chloride transport in concrete-measurement and prediction,
Doctoral Thesis, Göteborg, Chalmers University of Technology,
1996
7 F. P. Glasser, J. Marchand, E. Samson, Durability of concrete –
degradation phenomena involving detrimental chemical reactions,
Cem. Concr. Res, 38 (2007) 2, 226–246, doi:10.1016/j.cemconres.
2007.09.015
8 I. Santamaría-Vicario, A. Rodríguez, C. Junco, S. Gutiérrez-Gonzá-
lez, V. Calderón, Durability behavior of steelmaking slag masonry
mortars, Materials & Design, 97 (2016), 307–315, doi:10.1016/
j.matdes.2016.02.080
T. MELICHAR et al.: DURABILITY OF MATERIALS BASED ON A POLYMER-SILICATE MATRIX ...
Materiali in tehnologije / Materials and technology 51 (2017) 5, 751–758 757
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS
diagram "22"). A combination of frost and chloride ions
caused a decrease in the strength of 27.5 % (MBS-90Cl)
and 29.6 % (MFA-90Cl). These values can be assessed
as adequate for the given type of material (i.e., the
material with a porous aggregate) after a given number
of cycles. The thermal resistance (a relative decrease in
the compressive strength) of the materials in individual
environments after being exposed to 1000 °C was
approximately 64–69 % (72–78 %) for the reference
samples (the samples exposed to the aggressive envi-
ronment). It is interesting that slag (i.e., MBS) showed
better results than the other reference material; however,
after the exposure to the aggressive environment and
high temperature, fly ash was better (i.e., MFA). For
illustration, MBS-90/Cl (MFA-90/Cl) showed a decrease
in the compressive strength of 75.1 % (74.1 %; Figure
2). A slight increase in the thermal resistance developed
over time in spite of the higher number of cycles in the
aggressive environment. The only exception was
MFA-90/Cl. An evaluation of the relative change in the
thermal resistance caused by the aggressive environment
shows an irregular development of the curves (Figure 3).
This is particularly clear for temperatures of 600 °C and
above. It is evident that the exposure to an aggressive
environment and 1000 °C caused a decrease in the
observed parameter of MBS (MFA) of approximately
11 % (2.5–7.2 %).
Further, the bending tensile strength was evaluated.
The differences are less obvious compared to the
development of the compressive strength (Figures 1 and
4). The increase in the bending strength in time was also
less considerable than the increase in the compressive
strength. The bending strengths of the test specimens not
exposed to aggressive environments and a thermal load
were from 7.3 N mm–2 to 7.6 N mm–2 (6.9 N mm–2 to
7.2 N mm–2) for mix designs MBS (MFA). After the ex-
posure of the samples to the aggressive environment with
chloride ions, the decrease was 12.6 % for MBS-90 and
13.9 % for MFA-90.
The decrease in the tensile bending strength caused
by the exposure to aggressive environments is then much
lower than that of the compressive strength. The negative
impact on the thermal resistance was also smaller. The
decrease in the tensile bending strength was 65.8 %
(62.3 %) for MBS-90/R (MFA-90/R) after the exposure
to 1000 °C (Figure 5). These facts imply that the substi-
tution of the primary binder with fly ash had a more
positive effect from the viewpoint of a combined ex-
posure involving an aggressive environment and a ther-
mal load. On the other hand, comparing the changes in
the thermal resistance in time and after the exposure to
adverse environments shows (Figure 6) that blast-fur-
nace slag had better results (MBS). The reduction in the
thermal resistance after the exposure to 1000 °C was
5.3 % for MBS-90/Cl-R and 6.1 % for MFA/Cl-R. The
reduction in the thermal resistance of MFA after the
exposure to 600 °C is also interesting for both tested
ages. It can be assumed that used high-temperature fly
ash contains components that react with chloride
solutions, possibly only during the thermal load. It could
also be a synergy reaction of both mentioned influences.
The synergy effect of an aggressive environment and
extreme temperatures causes a considerable degradation
of the structures of the materials based on a silicate
matrix and a porous aggregate. The given case is con-
firmed with the results of physico-mechanical tests of
materials MBS and MFA. The CT examination proved
the above character of the crack changes after the expo-
sure to the aggressive environment (chlorides and frost)
and the subsequent extreme thermal load. On the refe-
rence materials, only a small amount of randomly
oriented cracks was identified (Figure 7). The cracks
were rather small, i.e., with a smaller width. These
cracks mostly did not reach the transition zone between
the matrix and dense aggregate. On the contrary, the
number of cracks of the materials exposed to the aggres-
sive environment was larger (Figures 8 to 10). An
increase in the width and number of the cracks is evident
as the number of aggressive cycles and age of the sam-
ples grow. However, the increase was not considerable.
The orientation of the cracks was easily observable; the
cracks pointed towards the center of a test specimen
(Figures 8 and 9). The width and number of the cracks
and more cracks in the transit zone between the dense
aggregate and the matrix were evident compared to the
reference materials.
The last representative sample was FMA-60/Cl (Fig-
ure 10). It is interesting that its cracks are more close to
the surface, with an orientation similar to that of MBS.
Chloride ions combined with frost and the subsequent
thermal shock damaged more considerably the surface
areas of MFA, whereas MBS was damaged more evenly
throughout the whole structure.
T. MELICHAR et al.: DURABILITY OF MATERIALS BASED ON A POLYMER-SILICATE MATRIX ...
756 Materiali in tehnologije / Materials and technology 51 (2017) 5, 751–758
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS
Figure 12: Microstructure of MBS-90/Cl (90 days, Cl – exposure to
chloride solution and frost environment, 100 cycles), exposure to
1000 °C, 5000× magnification
The XRD analysis was used for the identification of
crystal phases and their changes. XRD did not identify
Friedel’s salt in any of the tested specimens. The crucial
factor of the formation of this chemical compound is the
temperature, which is, inter alia, mentioned by Dela-
grave et al.3, Izquierdo et al.4, Yuan5 and Tang6. It is then
evident that the damage of the structure caused by the
combination of frost and the solution with chloride ions
is purely mechanical. The salt in the solution – NaCl – is
transported into the porous structure of the composite by
equalizing the concentration gradient. Sudden changes of
the temperatures above and below zero then cause the
crystallization of the salt and the change of the phase of
water, which necessarily causes a decrease in the me-
chanical properties of the given material. This corres-
ponds with the findings determined with CT. As regards
the changes in the structures of the analyzed materials, a
decomposition of chemical compounds (in particular
mineralogical phases) typical for silicates and the used
aggregate, due to the increasing temperature, was ob-
served. The development shows peaks with a decreasing
intensity and a gradual ceasing of portlandite, calcite and
CSH phases. At temperatures over 600 °C, mew phases
were observed (like -C2S).
SEM together with an element analysis showed the
presence of Cl– ions in some areas. Microcracks and the
degree of decomposition of the hydration products of the
matrix or the changes in the structure of the used aggre-
gate were marked, as shown in Figures 11 and 12.
Almost no failures were observable in the transit zone
between the porous aggregate (agloporite) and the
matrix. As regards the age of the tested materials/number
of cycles, no considerable differences in the microstruc-
ture were observed. A 5000× magnification clearly
shows a degraded polymer-silicate matrix. SEM images
clearly show spherical particles of fly ash also in MBS.
This was caused by an imperfect manufacturing process
of agloporite, during which not all granules (for the
production of the aggregate) were perfectly compacted
and fired. However, as this fly ash had gone through the
thermic process twice, it is almost an inert filler from the
viewpoint of high temperature. Only few microscopic
cracks were observed in the matrix.
5 CONCLUSIONS
The influence of a combination of an aggressive
environment (chloride solution and freeze-thaw cycles)
and a thermal load (of up to 1000 °C) was tested and
analyzed in detail on newly designed materials as it is
not a thoroughly examined area. Fly-ash agloporite is a
promising aggregate and its influence on polymer-sili-
cate materials is still not quite clear. The advantage of
agloporite is its thermal resistance and very good
interaction with a polymer-silicate matrix. However, an
exposure to cyclic changing of temperatures above and
below zero, intensified by a salt solution, makes the use
of the porous aggregate difficult. Blast-furnace slag
(MBS) and fly ash (MFA) were used for a modification
of the matrix composition. Physico-chemical and micro-
structural analyses proved that the action of the
above-mentioned environment disturbs the structures of
MBS and MFA in a mechanical way, causing an expan-
sion due to the change of the phase of water or crystalli-
zation of salt rather than the formation of new chemical
compounds. The extreme temperature then only inten-
sifies these phenomena by degrading the structures, in
particular that of the matrix. It was proved that CT is
crucial for the explanation of the changes/failures of the
inner structure. This analytical method is quite suitable
for examining the three-dimensional structure of a given
material. It is particularly applicable for revealing va-
rious cracks, their orientation, localization or number.
The tested materials have a large potential for future
research. An examination of the behavior of the mate-
rials over a longer time (e.g., 180 d and 360 d) would
also be very interesting.
Acknowledgements
This paper has been worked out with the financial
support of The Czech Science Foundation (GA^R),
project GA15-07657S, "Study of kinetics of processes
occurring in the composite system at extreme tem-
peratures and exposed to an aggressive environment", as
well as under project No. LO1408 "AdMaS UP –
Advanced Materials, Structures and Technologies",
supported by the Ministry of Education, Youth and
Sports under the National Sustainability Programme I.
6 REFERENCES
1 J. G. Jang, H. J. Kim, H. K. Kim, H. K. Lee, Resistance of coal
bottom ash mortar against the coupled deterioration of carbonation
and chloride penetration, Materials & Design, 93 (2016), 160–167,
doi:10.1016/j.matdes.2015.12.074
2 M. Maes, N. De Belie, Resistance of concrete and mortar against
combined attack of chloride and sodium sulphate, Cement and Con-
crete Composites, 53 (2014), 59–72, doi:10.1016/j.cemconcomp.
2014.06.013
3 A. Delagrave, J. Marchand, J. P. Ollivier, S. Julien, K. Hazrati,
Chloride binding capacity of various hydrated cement paste systems,
Advanced Cement Based Materials, 6 (1997), 28–35, doi:
10.1016/S1065-7355(97)90003-1
4 D. Izquierdo, C. Alonso, C. Andrade, M. Castellote, Potentiostatic
determination of chloride threshold values for rebar depassivation –
experimental and statistical study, Electrochim. Acta, 49 (2004)
17–18, 2731–2739, doi:10.1016/j.electacta.2004.01.034
5 Q. Yuan, Fundamental studies on test methods for the transport of
chloride ions in cementitious materials, Doctoral Thesis, Ghent,
Ghent University, 2009
6 L. Tang, Chloride transport in concrete-measurement and prediction,
Doctoral Thesis, Göteborg, Chalmers University of Technology,
1996
7 F. P. Glasser, J. Marchand, E. Samson, Durability of concrete –
degradation phenomena involving detrimental chemical reactions,
Cem. Concr. Res, 38 (2007) 2, 226–246, doi:10.1016/j.cemconres.
2007.09.015
8 I. Santamaría-Vicario, A. Rodríguez, C. Junco, S. Gutiérrez-Gonzá-
lez, V. Calderón, Durability behavior of steelmaking slag masonry
mortars, Materials & Design, 97 (2016), 307–315, doi:10.1016/
j.matdes.2016.02.080
T. MELICHAR et al.: DURABILITY OF MATERIALS BASED ON A POLYMER-SILICATE MATRIX ...
Materiali in tehnologije / Materials and technology 51 (2017) 5, 751–758 757
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS
9 S. Aydin, Development of a high-temperature-resistant mortar by
using slag and pumice, Fire Safety Journal, 43 (2008), 610–617,
doi:10.1016/j.firesaf.2008.02.001
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758 Materiali in tehnologije / Materials and technology 51 (2017) 5, 751–758
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B. MA[EK et al.: INFLUENCE OF THERMOMECHANICAL TREATMENT ON THE GRAIN-GROWTH BEHAVIOUR ...
759–768
INFLUENCE OF THERMOMECHANICAL TREATMENT ON THE
GRAIN-GROWTH BEHAVIOUR OF NEW Fe-Al BASED ALLOYS
WITH FINE Al2O3 PRECIPITATES
VPLIV TERMOMEHANSKE OBDELAVE FeAl ZLITIN S FINIMI
Al2O3 IZLO^KI NA RAST ZRN
Bohuslav Ma{ek1, Omid Khalaj1, Hana Jirková1, Jiøí Svoboda2,
Dagmar Bublíková1
1University of West Bohemia, Regional Technology Institute, Univerzitní 22, 306 14 Pilsen, Czech Republic
2Institute of Physics of Materials, Academy of Sciences of the Czech Republic, @i`kova 22, 616 62 Brno, Czech Republic
svobj@ipm.cz
Prejem rokopisa – received: 2016-07-20; sprejem za objavo – accepted for publication: 2017-04-20
doi:10.17222/mit.2016.232
To obtain the superior-high-temperature creep strength, a transformation of a fine-grained structure to large grains due to
abnormal grain growth or recrystallization is an important process in oxide-dispersion-strengthened (ODS) alloys. The
processing of steel is enabled with powder metallurgy, which utilizes powders consisting of a Fe-Al metal matrix with a large O
content, prepared with mechanical alloying, and their hot consolidation due to rolling. The thermomechanical characteristics of
new ODS alloys with a Fe-Al matrix are investigated in terms of the changes in the grain-size distribution. The recrystallization
and grain growth were quantified after heating up to 1200 °C, which is the typical consolidation temperature for standard
nanostructured ferritic steels. The results show that new ODS alloys are significantly affected by the thermomechanical
treatment leading to microstructural changes. Recrystallization is mostly affected by decreasing the deformation and increasing
the holding time, which leads to a growth of the grain size.
Keywords: grain growth, ODS alloys, steel, Fe-Al, Al2O3
Da bi pridobili najvi{jo temperaturo mo~i lezenja, je transformacija drobnozrnate strukture v ve~ja zrna ali celo v abnormalno
velika oziroma rekristalizacija pomemben proces pri zlitinah, oja~anih z oksidno disperzijo (angl. ODS). Obdelava jekla je
omogo~ena z metalurgijo v prahu, ki pomaga prahom, ki vsebujejo metalno matrico Fe-Al z veliko vsebnostjo kisika,
pripravljeno z mehanskim legiranjem in njihovo vro~o konsolidacijo pri valjanju. Termomehanske karakteristike novih
ODS-zlitin s Fe-Al matrico so bile preiskovane, ker je pri{lo do sprememb v velikosti porazdelitve zrn. Rekristalizacija in rast
zrn sta bili ovrednoteni po segretju do 1200 °C, ki je tipi~na temperatura konsolidacije za nanostrukturirana feritna jekla.
Rezultati ka`ejo, da na ODS-zlitine zelo vpliva termomehanska obdelava, ki pripelje do sprememb v mikrostrukturi. Na
rekristalizacijo najve~krat vpliva deformacija in pove~anje ~asa zadr`anosti, ki povzro~i rast velikost zrn.
Klju~ne besede: rast zrn, ODS-zlitine, jeklo, Fe-Al, Al2O3
1 INTRODUCTION
Historically, ODS alloys have been employed to
improve high-temperature mechanical properties. In
1910, the first utilization of an oxide dispersion was
reported by W. D. Coolidge. Using the classical powder
metallurgy, a tungsten-based alloy reinforced with tho-
rium oxides was developed to impede high-temperature
grain growth and therefore increase the life span of a
tungsten-filament lamp.1 After this first development,
several other applications with various metallic matrices
such as aluminium or nickel were implemented over the
decades. A notable improvement in the field was made
by J. S. Benjamin at the International Nickel Company
(INCO) laboratory: he proposed a new process based on
high-energy-milling powder metallurgy – later called
mechanical alloying.2 This process was introduced to
obtain a fine and homogeneous oxide dispersion within a
nickel matrix. Its aim was to produce high-temperature-
resistant materials for gas-turbine applications.3
Currently, mechanical alloying is still considered to
be the most effective process for obtaining fine and
homogeneously distributed particles. The volume frac-
tion of dispersed spherical oxides (usually Y2O3) is
typically below 1 % and the oxides typically have a
mean size of 5–30 nm. The mechanically alloyed powder
is then consolidated at high temperatures and pressures
to produce the bulk material in the form of a bar or tube
stock. Subsequently, different thermomechanical treat-
ments are applied to optimize its microstructure and
mechanical properties.
Oxides are much more resistant to coarsening in the
coarse-grained ferrite than the ’-precipitates in super-
alloys, and the limiting temperature for a long-term
operation is between 1000 °C and 1100 °C when the
mean size of oxides is 20–30 nm. This clearly indicates
that oxides are extremely stable and the microstructural
stability of ODS alloys is much higher than that of
nickel-based superalloys. However, a loss of mechanical
properties due to the coarsening of oxides was also
Materiali in tehnologije / Materials and technology 51 (2017) 5, 759–768 759
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS
UDK 67.017:621.78:669.15 ISSN 1580-2949
Original scientific article/Izvirni znanstveni ~lanek MTAEC9, 51(5)759(2017)