Resistance of modified hardened cement paste to frost and de-icing salts.
Skripkiunas, Gintautas ; Nagrockiene, Dzigita ; Girskas, Giedrius 等
Modifikuoto cemetbetonio atsparumas salciui ir leda tirpdanciu
drusku poveikiui
Modificetas cementa pastas salizturiba un pretestiba pretapledojuma
salim
Modiitseeritud kivistunud tsementpasta vastupidavus kulmale ja
libedustorje sooladele
1. Introduction
When de-icing salts are applied on bridges and carriageways in
winter, part of the salt usually gets onto road and bridge structures.
Studies of Lithuanian scientists have revealed that the highest chloride
concentrations in snowmelt runoff are observed in highways (Storpirstyte
et al. 2003) where the majority of bridges and flyovers are also
located. NaCl and Ca[Cl.sub.2] solutions are used to reduce the
slipperiness of roads (Baltrenas et al. 2009; Rimkus 1999) where
chlorides turn snow or ice to brine. Rimkus (1999) states that lately
about 100 000 t of white technical salt is used on Lithuanian roads
during the winter season. Reduced durability of concrete is one of the
biggest concerns for the operators of road structures in cold climates.
The complexity of chemical composition and structure of hardened cement
paste and the variety of factors affecting concrete structures under the
afore-described conditions makes it difficult to assess explicitly the
chemical and physicochemical processes that occur simultaneously in
hardened cement paste. Investigation into the resistance of concrete to
aforementioned factors is focused on the resistance of the binding phase
in concrete, i.e. hardened cement paste (matrix).
The decrease in the durability of concrete exposed to de-icing salt
solutions (DSS) is described as superficial damage caused by a salt
solution on top of the frozen layer. This damage is progressing and is
observed in the form of scaled concrete pieces (Jana 2004; Valenza II,
Scherer 2007). It should be noted that salt scaling is not the same as
freeze-thaw damage, which is characterized by the reduction of the
entire structure strength, because superficial scaling of concrete
initially causes no threat to mechanical integrity of concrete. Research
into the alternatives of using secondary materials to ensure the
durability of concrete is done for the sake of global climate protection
and with the aim to reduce the use of clinker Portland cement (Nili,
Zaheri 2011; Skripkiunas et al. 2009).
The properties of modern building materials containing cement and
various modifying agents (Si[O.sub.2] micro particles, ash, sodium
silicate solution, plasticizers) highly depend on nanostructures formed
during cement hydration. These structures influence the key properties
of the material, i.e. strength and durability. It is hard to retain
materials in nanodispersion under natural conditions because of
thermodynamic instability, whereas the disadvantage of artificial
nanodispersions is low production capacity. Nanodispersions in the form
of by-products, such as Si[O.sub.2], are an exception. Nano Si[O.sub.2]
dispersion is unique because it has a big amount of free surface energy.
This free energy is generated by high chemical activity of the material
(Beaudoin et al. 2009; Jo et al. 2007; Lotov 2006).
To obtain better characteristics of construction materials at macro
level the formation of nano phases must be controlled and properties of
such materials have to be analysed at micro level because nano additives
act as supplementary crystallization centres in cementations materials
and change the direction and rate of physical and chemical processes
(Raki et al. 2010; Skripkiunas et al. 2008b; Sobolev et al. 2008).
Sodium silicate solution additive ([Na.sub.2]O x nSi[O.sub.2]) as well
as super plasticizer (PCE) have nanostructures in their composition.
Sodium silicate solution contains undissolved Si[O.sub.2] nano particles
of 1-2 nm in size and even a small amount of sodium silicate solution
(0.03-1%) influences cement hydration (Kiricsi et al. 2006; Pundiene et
al. 2005; Sandberg et al. 1989; Skripkiunas et al. 2008). High
Si[O.sub.2] activity enables Si[O.sub.2] to bind free Ca[(OH).sub.2]
(portlandite) in hardened cement paste. Stable and less water soluble
hydro silicates formed in the reaction enhance concrete durability and
strength. Studies of researchers (Gartner et al. 2002) have shown that
the use of Si[O.sub.2] nano particles in the production of cement matrix
influences the material's resistance to C-S-H destruction, whereas
portalindite is transformed into C-S-H gel. According to Lotov (2006)
cement starts binding due to the formation of nanodispersion particles
that bind the bigger part of water. Concrete strength starts increasing
with the increase of solid phase concentration in the system
cement-water. Observation and examination of hydration processes at nano
level is important for a new approach to cement hydration (Chen et al.
2004; Gartner et al. 2002,) values. G. Skripkiunas and M. Dauksys with
colleagues (Dauksys et al. 2009; Skripkiunas et al. 2008b; Skripkiunas
et al. 2010) examined the effect of various nanomodifiers on the
strength of hardened cement paste matrix, durability and rheological
properties.
Nanodispersion system is formed in the initial stage of hydration
of binding phase (Portland cement, aluminous cements) (Kiricsi et al.
2006). It is therefore necessary to explore the possibilities of halting
the formation of large crystallized hydration products in the initial
stage of structure formation by inducing the formation of amorphous
nano-sized hydration structures where more energy is accumulated.
Another group of researchers claims that nano additives in the material
(new nanostructures, i.e. super plasticizers, super strong nanofiber,
Si[O.sub.2], [Fe.sub.2][O.sub.3], A[I.sub.2][O.sub.3] and organic
montmorinollite nanoparticles) may improve the nanostructure of
cementations materials (Asao 2003; Jo et al. 2007; Kuo et al. 2006).
Super plasticizer, when mixed with cement and water, adsorbs on the
surface of cement particles [C.sub.2]S, [C.sub.3]S, [C.sub.3]A,
[C.sub.4]AF. For this reason particles of all types, irrespective of
their initial charge (before adding super plasticizer particles
[C.sub.2]S and [C.sub.3]S are negative and particles [C.sub.3]A,
[C.sub.4]AF are positive) become negatively charged, i.e. all particles
have the same charge and therefore particle sticking and coagulation is
disturbed (Yoshioka et al. 2002), the workability of cement paste
improves, less amount of water is required to produce the paste. To this
end, the binding phase consisting of colloidal sodium silicate solution
([Na.sub.2]O x nSi[O.sub.2]) and suspension super plasticizer based on
modified polycarboxylic ether may be used. H. Hommer, K. Wutz and H. Li
(Hommer, Wutz 2005; Li et al. 2004) have noted in their research papers
that super plasticizers of new generation not only disperse the material
and actively influence cement hydration process but also improve the
structure of cementations materials due to nanodispresion particles
present in their composition.
According to research results (Skripkiunas et al. 2008) sodium
silicate solution changes the microstructure of the hardened cement
paste, accelerates binding time, enhances closed porosity and has
insignificant effect on the strength of hardened cement paste. The said
factors have a positive effect on frost resistance of hardened cement
paste. It is therefore necessary to explore the possibilities of halting
the formation of large crystallized hydration products in the initial
stage of structure formation by inducing the formation of amorphous
nano-sized hydration structures where more energy is accumulated. To
this end, the binding phase consisting of colloidal sodium silicate
solution and suspension super plasticizer based on modified
polycarboxylic ether may be used.
A three-component binding phase consisting of colloidal sodium
silicate solution, Portland cement and super plasticizer was used in the
research into the effect of multicomponent disperse systems on the
durability of binder matrix. The research revealed the effect of sodium
silicate solution on the durability of hardened cement paste exposed to
de-icing salts under cyclic freeze-thaw conditions.
2. Materials
Portland cement CEM I 42.5 R manufactured by SC Akmenes cementas
was used for the tests. The parameters of the cement paste of normal
thickness were as follows: water content 25.4%; specific surface 360
[m.sup.2]/kg; particle density 3110 kg/[m.sup.3]; bulk density 1220
kg/[m.sup.3].
Two types of suspension super plasticizers were used as concrete
additives: polycarboxylic ether based super plasticizer with dry
particle concentration of 18.7%, pH value 6.4; electrical conductivity
4.390 mS/cm (hereinafter --super plasticizer R) and modified
polycarboxylic ether based super plasticizer with dry particle
concentration of 36.1%, pH value 4.4; electrical conductivity 1.480
mS/cm (hereinafter--super plasticizer F). Electric conductivity and pH
values were determined by Mettler-Toledo Device MPC 227 (pH electrode
InLab 410, 0.01 pH, and electric InLab electrode 730, the measurement
range of 0-1000 [micro]S/cm). Measuring was made at the ambient
temperature of 21 [+ or -] 0.5 [degrees]C.
Sodium silicate water solution (NST - [Na.sub.2]O x nSi[O.sub.2])
having silicate module 3.3, dry [Na.sub.2]O x nSi[O.sub.2] and water
ratio 60:40, average density value of liquid glass solution of 1382
kg/[m.sup.3] was also used as an additive. The hydrolysis reaction in
sodium silicate solution is expressed by the equation:
[Na.sub.2]O X Si[O.sub.2] + [H.sub.2]O = 2[Na.sup.+] + 2O[H.sup.-]
+ Si[O.sub.2].
5% sodium, 5% calcium and 5% magnesium chloride solutions were used
as freezing media. Tap water was used as freezing media for control
specimens.
3. Research methodology
Cement pastes were made of dry matter and mixed in forced action
mixer Auto mix. Concrete specimens were formed in impermeable prism
moulds 40 x 40 x 160 (mm). Settled specimens were left in moulds for 20
h at the ambient temperature of 20 [degrees]C [+ or -] 2[degrees]C.
Hardened cement specimens were left for 28 days at the ambient
temperature of 20 [degrees]C [+ or -] 2 [degrees]C and [greater than or
equal to] 95% humidity. Prior to the experimental research the
compressive strength, the initial length of the specimens and the
initial ultrasonic pulse velocity were determined according to LST EN
196-1:2005 "Methods of Testing Cement--Part 1: Determination of
Strength" after 28 days of hardening. The change in compressive
strength, relative deformations, loss of weight and ultrasonic pulse
velocity in specimens was measured after 56 freeze-thaw cycles where the
surface of specimens was treated with different saline solutions.
Glass plates were inserted at the ends of 40 x 40 x 160 (mm)
concrete prisms during the experimental research into the change of
relative deformations and ultrasonic pulse velocity in order to
determine the deterioration of the internal concrete structure.
An ultrasonic wave propagation time measuring method was used in
ultrasonic test. The method is based on electronic modelling of the
leading short pulse propagation, i.e. the propagation of the pulse
between two transducers placed at a certain distance. Ultrasonic pulses
transmitted by the generator are turned into mechanical pulses in the
transducer and propagate in the form of elastic waves across the
researched material. The receiving transducer converts the mechanical
pulse, which has propagated through the material, into electric pulse
and displays it on the screen. The experimental research employs
universal transducers where electric pulse is converted into mechanical
pulse and vice versa. In the experimental research relative deformation
(relative elongation) after 56 freeze-thaw cycles of specimens exposed
do de-icing solutions is calculated as the ratio of absolute deformation
and initial length of the specimen. Repeated saturation of the specimen
surface covered with 3 mm layer of water for (72 [+ or -] 2) h at room
temperature was assumed as the initial length of the specimen for
deformation measuring.
To determine the amount of scaled matter after freeze-thaw cycles
the specimens were cut into 40 x 40 x 40 (mm) cubes and the cut surface
was used as the test surface. Freezing and thawing was conducted by
leaving the specimens for 56 days in a climatic chamber with controlled
temperature and heating time and digital defrosting and ventilation
controller (Dixell digital controller with defrost and fans management
min set point -50 [degrees]C/-58 [degrees]F; max set point 110
[degrees]C/230 [degrees]F). One freeze-thaw cycle lasted for 24 h at the
temperature changing from -22 [degrees]C to 24 [degrees]C. During one
cycle the temperature was above 0 [degrees]C from 7 to 9 h.
4. Research results
Table 1 shows the change in compressive strength and density of
hardened cement paste modified with sodium silicate solution (NST -
[Na.sub.2]O x nSi[O.sub.2]).
The results show that the compressive strength as well as density
of hardened cement paste after 28 days of setting slightly reduces or
increases and mainly depends of the plasticizing additive and
water/cement ratio. Irrespective of cement mix composition, the
compressive strength and density of hardened cement paste after 28 days
of setting did not change or changed insignificantly when NST content
was increased up to 0.8%. Based on the evaluation of previous research
results and literature analysis the most appropriate cement composition
was developed for the experimental research into durability. NST added
at 0.5% of the matrix content should react with polycarboxylic ether
super plasticizer and water/cement ratio should be 0.27.
4.1. Results of research into the effect of NST on the compressive
strength of hardened cement paste exposed to de-icing salts
Figs 1 and 2 illustrate the changes in compressive strength of
hardened cement paste with and without NST after 56 freeze-thaw cycles
when the surface of hardened cement paste is exposed to different
de-icing salt solutions. The solid line in the figures illustrates the
value of compressive strength prior to freezing; the columns represent
the values after 56 freeze-thaw cycles.
Research results have shown that NST additive has an effect on the
compressive strength of concrete exposed to de-icing salt solutions
under cyclic freeze-thaw conditions. The compressive strength values
before freezing were similar in compositions with and without NST
additive; the compressive strength of hardened cement paste made of
Portland cement without NST additive was 85.4 MPa (standard deviation
[sigma] = 2.5 MPa) and 82.8 MPa in composition without NST additive
(standard deviation [sigma] = 2.5 MPa). After 56 freeze-thaw cycles the
adverse effect of saline solutions on the compressive strength is mostly
expressed in specimens made without NST additive and exposed to 5%
Ca[Cl.sub.2] solution. The compressive strength in specimens made
without NST additive and exposed to 5% Ca[Cl.sub.2] solution dropped
down to 50.1 MPa ([sigma] = 1.5 MPa). 5% NaCl and 5% Mg[Cl.sub.2]
de-icing salt solutions reduced the compressive strength to 70.1 MPa
([sigma] = 0.81 MPa) and 76.1 MPa ([sigma] = 1.4 MPa) respectively. NST
additive was found to reduce the loss in compressive strength in
hardened cement paste with NST additive after 56 freeze-thaw cycles in
saline solutions. When NST is added to the cement mix at 0.5% of the
matrix content the compressive strength is similar as in specimens
before freezing. The biggest drop in compressive strength was observed
when the surface of specimens was treated with 5% NaCl solution. The
compressive strength value reduced to 80.2 ([sigma] = 3.2 MPa).
The experimental research results presented in Figs 1 and 2 show
that after 56 freeze-thaw cycles and treatment with different salt
solutions the biggest drop in compressive strength was observed in
specimens without NST additive treated with 5% Ca[Cl.sub.2] solution
(50.1 MPa), and the least drop was recorded in specimens with 0.5% NST
treated with 5% Mg[Cl.sub.2] solution (87.8 MPa, [sigma] = 2.0 MPa).
The standard deviation of compressive strength ranges from 0.8 MPa
to 2.5 MPa in hardened cement paste without NST and from 2.0 MPa to 3.2
MPa in hardened cement paste with NST. Therefore, it could be stated
that NST additive slightly changes the standard deviation of compressive
strength. Low values of standard deviation confirm insignificant
variation of research results and prove the reliability of obtained
results. Smaller change in compressive strength of hardened cement paste
modified with NST additive compared to control specimens exposed to
de-icing salt solutions is explained by the following reasons:
1. The amount of sodium silicate solution reacting with
polycarboxylic ether super plasticizer in cement paste enables to bind
free Ca[(OH).sub.2] in hardened cement paste and produce stable and less
soluble in water hydrosilicates that increase the compressive strength
of concrete.
2. In the presence of NST the matrix contains more hydro silicates
during the setting compared to cement mix compositions without NST
because Ca[(OH).sub.2] react with Si[O.sub.2], which is formed during
sodium silicate hydrolysis, and produce calcium hydro silicates (C-S-H)
from sodium silicate. The amount of NST used in the research (at 0.5% of
the total matrix content) enables Si[O.sub.2] to bind free
Ca[(OH).sub.2] portlandite in hardened cement paste.
3. Modification of hardened cement paste with NST enables to change
durability parameters.
4.2. Results of research into the effect of NST on ultrasonic pulse
velocity in hardened cement paste exposed to de-icing salts
The experimental research in ultrasonic pulse velocity in the
structure of hardened cement paste is based on the ratio of ultrasonic
pulse propagation time and the distance of travel across the specimen
within a specified time period. Microcracks in the structure of hardened
cement paste are filled with air having the acoustic resistance of 43
g/[cm.sup.2]s. This parameter ranges within the limits of (0.9-1.2) X
[10.sup.6] g/[cm.sup.2]s in hardened cement paste, i.e. is 100 000 times
higher. That means that microcracks formed in hardened cement paste
practically stop the propagation of ultrasonic pulse generated by
ultrasonic wave diffractions around the microcrack. The growing number
of microcracks increases the pulse propagation distance and reduces the
velocity. Figs 3 and 4 illustrate the kinetics of ultrasonic pulse
velocity after 56 freeze-thaw cycles when the surface of hardened cement
past is treated with different saline solutions.
The curves in Figs 3 and 4 show that ultrasonic pulse velocity
after 56 freeze-thaw cycles is lower in specimens with NST additive
irrespective of the freezing media on the surface of the specimen. That
means that there are smaller microcracks in the cement matrix of
specimens with NST additive. From Fig. 3 may see that in hardened cement
paste without NST additive and exposed to 5% Ca[Cl.sub.2] solution the
drop in ultrasonic pulse velocity is 681 m/s (from 3900 m/s to 3219
m/s); whereas in hardened cement paste with NST additive the ultrasonic
pulse velocity drops from 3777 m/s to 3698 m/s, i.e. reduces by 79 m/s.
The comparison of control specimens and specimens with NST additive has
revealed similar trends in the change of ultrasonic pulse velocity.
Figs 3 and 4 show that after 56 freeze-thaw cycles the change in
ultrasonic pulse velocity is 2.3 times higher in specimens with NST
additive exposed to 5% sodium chloride solution and 3.2 times higher in
specimens exposed to 5% magnesium chloride solution compared to control
specimens. The lowest ultrasonic pulse velocity after 56 freeze-thaw
cycles was observed in hardened cement paste with NST additive and
exposed to 5% Mg[Cl.sub.2] de-icing solution.
According to experimental research results the standard deviation
of ultrasonic pulse velocity in specimens without NST additive was 86.9
m/s and in specimens with NST additive it was 81.5 m/s. Therefore, it
could be stated that research results are reliable because the standard
deviation values are not big and similar.
The summary of ultrasonic pulse velocity results after 56
freeze-thaw cycles in the presence of de-icing salt solutions shows that
introduction of 0.5% NST additive into the mix causes the reduction in
ultrasonic pulse velocity. A lower drop in ultrasonic pulse velocity in
specimens with NST additive compared to specimens without NST additive
may be explained by the bigger amount of amorphous compounds that cover
calcium hydro silicate crystals and partly close capillary pores. For
this reason smaller microcracks develop in the cement matrix of
specimens with NST additive.
4.3. Results of research into the effect of NST on deformations in
hardened cement paste exposed to de-icing salts
One of the objectives of experimental research was to determine
changes in the relative length of specimens subjected to de-icing salts
under cyclic freeze-thaw conditions. The humidity of capillary porous
materials is closely related to the expansion-contraction deformations.
The volume of hardened cement paste increases with its humidity due to
bigger dimensions of polycrystalline material structures and the action
of capillary forces. Surface tensions develop because molecular force
balance between the particles on the surface of the pores disappears.
Partial compensation of surface forces that are not in equilibrium on
the surface of the pores occurs during adsorption process, thus reducing
the surface tension of hardened cement paste. Hardened cement stone
expands under the influence of tension forces. Defects in the structure
of hardened cement paste are caused by the variation of sorption
capacity of cement under repeated freeze-thaw conditions and exposure to
de-icing solutions. Figs 5 and 6 illustrate the kinetics of hardened
cement paste deformations after 56 freeze-thaw cycles when the surface
of hardened cement paste is exposed to different salt solutions.
[FIGURE 3 OMITTED]
[FIGURE 4 OMITTED]
[FIGURE 5 OMITTED]
[FIGURE 6 OMITTED]
The curves in the figures clearly illustrate that after 56
freeze-thaw cycles and exposure to salt solutions relative deformations
in hardened cements stone with NST additive (at 0.5% of the matrix
content) changed to 78.4 x [10.sup.-3] and to 205.9 X [10.sup.-3] in
specimens without NST additive.
Research results have shown that much smaller deformations occur in
hardened cement paste with NST additive after 56 freeze-thaw cycles and
exposure do de-icing salt solutions. Therefore, sodium silicate solution
is used to improve the durability of hardened cement paste.
The biggest increase in deformations after 56 freeze-thaw cycles is
observed in specimens exposed to 5% Ca[Cl.sub.2] solution where relative
deformations reached 205.9 X [10.sup.-3]. In specimens with NST additive
exposed to Ca[Cl.sub.2] solution relative deformations were 59.8 X
[10.sup.-3].
Fig. 6 illustrates that after 56 freeze-thaw cycles the relative
deformations in hardened cement paste with NST additive reduced 3.4
times when 5% Ca[Cl.sub.2] solution was used as freezing medium, 2.6
times when the freezing medium was 5% Mg[Cl.sub.2] solution and 1.9
times when the freezing medium was 5% NaCl solution. It should be noted
that relative deformations in specimens with and without NST additive
were insignificant when tap water was used as the freezing medium
compared to deformations when the freezing medium was de-icing salt
solution, i.e. 17.5 X [10.sup.-3] and 51.0 X [10.sup.-3] respectively.
Deformations, however, differ 2.9 times. That means that hardened cement
stone with NST additive is more resistant to cyclic freezing and thawing
when de-icing salt is applied.
The analysis of relative deformations in cement stone exposed to
different salt solutions under cyclic freeze-thaw conditions has shown
that after 56 freeze-thaw cycles hardened cement stone with NST additive
is mostly affected by 5% Na[Cl.sub.2] de-icing salt solution (relative
deformations 78.4 X [10.sup.-3]) and least affected by 5% Mg[Cl.sub.2]
de-icing salt solution (relative deformations 45.8 X [10.sup.-3]).
4.4. Results of research into the effect of NST on the surface
scaling in hardened cement paste exposed to de-icing salts under
freeze-thaw conditions
The research has shown that although surface scaling is relatively
insignificant in terms of mass (measuring unit is mg), however general
tendencies are observed. Small loss in surface mass is related to low
water/cement ratio (0.27, Table 1). The experimental research has
revealed that after 56 freeze-thaw cycles the loss in weight in
specimens with NST additive (at 0.5% of the total matrix content) is
lower compared to control samples irrespective of the freezing medium.
Figs 7 and 8 illustrate the amount of scaled matter per area unit after
56 freeze-thaw cycles when the surface of hardened cement paste is
exposed to different salt solutions.
After 56 freeze-thaw cycles the specimens with NST additive
compared to control specimens had the biggest difference in the mass
loss, i.e. 2.7 times, when the freezing medium was 5% Ca[Cl.sub.2]
solution. When the freezing medium on the surface of the specimen was 5%
NaCl and 5% Mg[Cl.sub.2], the mass loss differed 1.3 and 2.0 times,
respectively.
The analysis of hardened cement paste surface scaling caused by
de-icing salt solutions under cyclic freeze-thaw conditions based on the
data presented in Figs 7 and 8 leads to the conclusion that the biggest
scaling occurs in specimens without NST additive exposed to 5%
Ca[Cl.sub.2] solution (6.034 mg/[cm.sup.3]) and the smallest scaling is
observed in specimens with 0.5% NST additive exposed to 5% Mg[Cl.sub.2]
solution (1.508 mg/[cm.sup.3]).
5. Conclusions
The biggest drop in compressive strength occurs in specimens
without NST additive exposed to 5% Ca[Cl.sub.2] solution and the least
drop in compressive strength occurs in specimens with 0.5% NST additive
exposed to 5% Mg[Cl.sub.2] solution.
Compressive strength in specimens with NST additive changes
insignificantly after 56 freeze-thaw cycles irrespective of the type of
de-icing salt solution used as freezing medium.
Ultrasonic pulse velocity in hardened cement paste without NST
additive slows down significantly after 28-42 freeze-thaw cycles
depending on freezing media, whereas in specimens with NST additive it
remains constant.
Deformations in specimens without NST additive increase
significantly with the number of freeze-thaw cycles; specimens with NST
additive undergo 2.5 times smaller deformations.
Mass loss in hardened cement paste resulting from surface scaling
under cyclic freeze-thaw conditions is insignificant and shall not be
used as a parameter to describe deterioration processes.
Research results have shown that hardened cement paste with NST
additive is subject to much smaller scale deterioration processes after
56 freeze-thaw cycles and exposure do de-icing salt solutions.
Therefore, sodium silicate solution may be used to improve the
durability of hardened cement paste and concrete used in road building.
doi: 10.3846/bjrbe.2012.36
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Received 9 September 2011; accepted 2 March 2012
Gintautas Skripkiunas (1), Dzigita Nagrockiene (2) ([mail]),
Giedrius Girskas (3), Eugenijus Janavicius (4)
(1, 2, 3) Dept of Building Materials, Vilnius Gediminas Technical
University, Sauletekio al. 11, 10223 Vilnius, Lithuania
(4) Dept of Building Materials, Kaunas University of Technology,
Studentu g. 48, 51367 Kaunas, Lithuania
E-mails: (1) gintautas.skripkiunas@vgtu.lt; (2)
dzigita.nagrockiene@vgtu.lt; (3) giedrius.girskas@vgtu.lt; (4)
Eugenijus.Janavicius@mc-bauchemie.com
Table 1. The change in compressive strength of
hardened cement paste
Composition Water/ NST Super
No. cement content, plasticizer
ratio % content, %
R F
1 0.27 0 - 0.5
2 0.2 - 0.5
3 0.5 - 0.5
4 0.8 - 0.5
5 0 0.5
-
6 0.2 0.5 -
7 0.5 0.5 -
8 0.8 0.5 -
Composition Water/ NST Compressive
No. cement content, strength,
ratio % MPa
1 0.27 0 84.6
2 0.2 79.4
3 0.5 81.0
4 0.8 80.5
5 0 80.0
6 0.2 81.8
7 0.5 82.2
8 0.8 83.2
Composition Water/ NST Density,
No. cement content, kg/[m.sup.3]
ratio %
1 0.27 0 2140
2 0.2 2132
3 0.5 2131
4 0.8 2133
5 0 2106
6 0.2 2138
7 0.5 2115
8 0.8 2130
Fig. 1. The dependence of compressive strength on saline solution
type in specimens made of Portland cement without additives
Freezing media Compressive strength Compressive strength
after 56 freeze-thaw before freezing, MPa
cycles, MPa
Water 88.49 85.36
Sodium chloride 70.12 85.36
Calcium chloride 50.11 85.36
Magnesium chloride 76.10 85.36
Note: Table made from bar graph.
Fig. 2. The dependence of compressive strength on saline solution
type in specimens made of Portland cement with NST additive
Freezing media Compressive strength Compressive strength
after 56 freeze-thaw before freezing, MPa
cycles, MPa
Water 84.43 82.82
Sodium chloride 80.17 82.82
Calcium chloride 84.89 82.82
Magnesium chloride 87.81 82.82
Note: Table made from bar graph.
Fig. 7. The dependence of mass loss on
saline solution type in specimens with
Portland cement after 56 freeze-thaw
cycles
Mass loss
mg/[cm.sup.2]
Water 1.214
Sodium chloride 3.882
Calcium chloride 6.034
Magnesium chloride 2.963
Note: Table made from bar graph.
Fig. 8. The dependence of mass loss
on saline solution type in specimens
with Portland cement and NST additive
after 56 freeze-thaw cycles
Mass loss
mg/[cm.sup.2]
Water 0.401
Sodium chloride 3.060
Calcium chloride 2.208
Magnesium chloride 1.508
Note: Table made from bar graph.
