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Sealer and coating systems for the protection of concrete bridge structures

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Abstract

Concrete bridge structures most often experience different forms of deterioration, such as surface scaling, spalling, and internal frost damage due to environmental and chemical attacks. Sealers and coatings are used to reduce these forms of concrete deterioration by limiting penetration of water and water-borne deleterious agents, such as chlorides and sulphates. Moreover, sealers and coatings are used to resist chemical attack and corrosion damage due to de-icer and anti-icer chemicals, such as NaCl, CaCl 2 , and MgCl 2 . They also facilitate moisture vapour transmission, and thus aid rapid drying and mitigate the effects of corrosion. This paper presents the key aspects of sealers and coatings used for the protection of concrete bridge structures. It highlights different types and selection criteria of sealers and coatings, surface preparation and application methods required for applying these products, and their role in protecting concrete. In addition, the different evaluation methods and performance criteria for sealers and coatings are discussed in this paper.
International Journal of the Physical Sciences Vol. 6(37), pp. 8188-8199, 31 December, 2011
Available online at http://www.academicjournals.org/IJPS
DOI: 10.5897/IJPSX11.005
ISSN 1992 - 1950 © 2011 Academic Journals
Review
Sealer and coating systems for the protection of
concrete bridge structures
Md. Safiuddin* and K. A. Soudki
Department of Civil and Environmental Engineering, Faculty of Engineering, University of Waterloo,
200 University Avenue West, Waterloo, Ontario, Canada N2L 3G1.
Accepted 7 September, 2011
Concrete bridge structures most often experience different forms of deterioration, such as surface
scaling, spalling, and internal frost damage due to environmental and chemical attacks. Sealers and
coatings are used to reduce these forms of concrete deterioration by limiting penetration of water and
water-borne deleterious agents, such as chlorides and sulphates. Moreover, sealers and coatings are
used to resist chemical attack and corrosion damage due to de-icer and anti-icer chemicals, such as
NaCl, CaCl2, and MgCl2. They also facilitate moisture vapour transmission, and thus aid rapid drying
and mitigate the effects of corrosion. This paper presents the key aspects of sealers and coatings used
for the protection of concrete bridge structures. It highlights different types and selection criteria of
sealers and coatings, surface preparation and application methods required for applying these
products, and their role in protecting concrete. In addition, the different evaluation methods and
performance criteria for sealers and coatings are discussed in this paper.
Key words: Bridge structure, chemical attack, concrete, de-icer and anti-icer, durability, freezing and thawing,
moisture vapour transmission, physical attack, sealer and coating, wetting and drying.
INTRODUCTION
Concrete deterioration is often identified in many
components (decks, piers, abutments, girders, and
barrier walls) of the bridge structure due to exposures to
aggressive environments (freezing and thawing, wetting
and drying, extreme temperature changes, etc.) and
corrosive chemicals (de-icers, anti-icers, etc.). De-icer
and anti-icer chemicals (de-icing and anti-icing salts),
such as NaCl, CaCl2, and MgCl2 are regularly used on
bridge decks to maintain safe driving conditions during
the winter weather in many cold-region countries. Other
chemicals, such as calcium magnesium acetate and urea
are also used as de-icer or anti-icer to a lesser degree.
Darwin et al. (2008), Kozikowski et al. (2007), and Sutter
et al. (2008) reported that CaCl2 and MgCl2 can cause
severe scaling, which not only damages the concrete
surface but also accelerates the ingress of deleterious
agents (chlorides, sulphates, etc.) and increases the
degree of saturation. In such conditions, chlorides can
penetrate the concrete cover more rapidly and carbon
*Corresponding author. E-mail: msafiudd@engmail.uwaterloo.ca
or safiq@yahoo.com.
dioxide can more easily diffuse from the atmosphere,
thus contributing to corrosion of the embedded
reinforcing steel. In addition, the increased degree of
saturation can cause strength loss due to the formation of
ice (Scherer and Valenza, 2005).
The deterioration of concrete in bridge structures can
occur due to physical and chemical attacks when
exposed to aggressive environments and corrosive
chemicals. In cold-region countries, the most common
physical deterioration of concrete is caused by the
actions of freezing and thawing. This attack is intensified
in the presence of de-icer or anti-icer chemicals used in
bridge maintenance during winter. As a result, the bridge
structures in cold-region countries are often deteriorated
due to the internal frost damage and surface scaling of
concrete (Filice and Wong, 2001; Julio-Betancourt,
2009). Moreover, the physical distress of concrete in
bridge structures can frequently be observed due to
wetting and drying with and without de-icer/anti-icer
chemicals associated with temperature changes (Darwin
et al., 2007, 2008).
Concrete bridge structures require special attention to
maintain their durability and service life under aggressive
environmental and chemical exposures. Without a
durability consideration, bridge structures may undergo
accelerated deterioration, such as surface scaling,
concrete spalling, and corrosion of the embedded
reinforcing steel. In this respect, experience confirms the
importance of providing protection to concrete bridge
structures. Concrete bridge structures can be protected
using the following methods (Drochytka and Petranek,
2002):
1. Improving the physical properties of concrete and
repair materials;
2. Altering the electrochemical behaviour of steel;
3. Applying surface treatments.
Many surface treatments, such as sealers, coatings,
membranes, and impregnation resins are currently used
for the protection of concrete bridge structures (Ibrahim et
al., 1999; Palle and Hopwood II, 2006; Wenzlick, 2007). It
is well accepted that the durability of reinforced concrete
primarily depends on the composition and properties of
its exposed surface layer (Pigeon et al., 1996). Coatings
and sealers are often used to protect this surface layer by
retarding the ingress of harmful chemicals (Jones et al.,
1995). Sealers are typically classified as either
penetrants or surface sealers that do not change the
appearance of concrete to any significant degree.
Coatings may be clear liquids, but typically are pigmented
to improve the aesthetics of concrete and to provide a
uniform appearance after restoration work for the bridge
structures. Penetrating sealers may be applied to all
exposed concrete surfaces, but the use of surface
sealers and coatings on trafficked surfaces is generally
limited due to their lower abrasion resistance.
To ensure effective performance, penetrating sealers
and surface coatings must have adequate adhesion to
the substrate, be applied at adequate thickness, and
provide good resistance to the ingress of water-borne
deleterious agents. Penetrating sealers must be applied
at the optimum rate to ensure good penetration into a
prepared substrate so that they can considerably reduce
the ingress of harmful chemicals. When it is desirable for
moisture vapour to transmit from the concrete under a
treated surface, both sealers and coatings should also
have an acceptable level of “breathability”.
The main objective of this study is to provide a review
of sealers and coatings, which are used for the protection
of concrete bridge structures. In this paper, the
mechanisms of concrete damages caused by de-icer and
anti-icer chemicals, and the influences of several key
factors are highlighted. The effects, application and
evaluation methods, and performance requirements of
different sealer and coating products are presented. In
addition, the selection criteria and surface preparation
methods for sealers and coatings are discussed. A
number of research needs with respect to the application,
performance, and evaluation of sealers and coatings are
Safiuddin and Soudki 8189
also identified.
DE-ICER AND ANTI-ICER CHEMICALS
Chemicals applied on bridge decks for winter highway
maintenance may be categorized as either de-icers or
anti-icers. De-icers are applied after snow falls to prevent
the formation of ice and to melt existing ice. In contrast,
anti-icers are applied before snow fall or at the early
stage of precipitation to prevent the formation of bond
between ice and road surface. Both de-icer and anti-icer
chemicals depress the freezing point of water by reducing
the temperature at which ice can form.
De-icer and anti-icer chemicals were first used on
roads, highways, and bridge decks in the U.S.A. during
the 1940s (TRB, 1991). Currently, the U.S.A applies
about 15 million tons of de-icing and anti-icing salts every
year (Shi, 2005). In Canada, the use of de-icing and anti-
icing salts on highways began during the 1950s (Julio-
Betancourt, 2009). De-icer and anti-icer chemicals can be
chloride-based or non-chloride-based. However, chloride-
based de-icer and anti-icer chemicals are commonly
used due to their low cost and relatively high
effectiveness (TRB, 2007). The most popular chloride-
based de-icer chemical is NaCl, followed by CaCl2. In
more recent years, MgCl2 usage has commenced; the
producers are promoting it as being more environ-
mentally friendly and less corrosive than NaCl and CaCl2.
In Southern Ontario of Canada, a formulated chloride-
based liquid de-icer/anti-icer, commercially known as
“Geomelt S30” has been used (Soudki et al., 2011). It
consists of an organic salt accelerator derived from
desugarized sugar beet juice (marketed under the name
of Geomelt 55 concentrate), which is blended with NaCl
brine. This product may allow less salt use for the same
effectiveness of other de-icers, and an improved
“stickiness” of the applied material to pavement surfaces.
De-icer chemicals penetrate the snow-ice layer to
break the ice-road surface bond or entirely react on the
ice surface to melt it and form slush. Both solid and liquid
de-icer chemicals are used depending on the road
conditions, degree of precipitation, and temperature. If
used in liquid condition, the mass concentration of de-icer
chemicals generally varies in the range of 20 to 32%
(Julio-Betancourt, 2009). Anti-icer chemicals can also be
used in solid or liquid condition. If used in liquid condition,
the concentration of anti-icer chemicals should be high
enough to prevent them from freezing before or after
application. In addition, liquid anti-icer chemicals must
have adequate viscosity to stick to the road surface.
When used in solid condition, the anti-icer chemicals
should start dissolving as soon as they are applied on the
road surface. Similar to de-icer chemicals, the mass
concentration of liquid anti-icer products varies within the
range of 20 to 32%.
8190 Int. J. Phys. Sci.
CONCRETE DAMAGES CAUSED BY DE-ICER AND
ANTI-ICER CHEMICALS
Damage mechanisms
De-icer or anti-icer chemicals can cause the physical
damage (surface scaling, spalling, internal frost damage,
etc.) and/or chemical damage (dissolution of hardened
cement paste, corrosion of steel reinforcement, etc.) of
concrete. The physical effects of de-icers with respect to
surface scaling and internal frost damage are well-
documented (Darwin et al., 2007, 2008; Hooton and
Julio-Betancourt, 2005; Verbeck and Klieger, 1957).
Hooton and Julio-Betancourt (2005), and Sutter et al.
(2008) reported that NaCl brine is more harmful than
CaCl2 and MgCl2 brines with regard to physical attack,
since it has the highest rate of penetration into hardened
concrete. Hooton and Julio-Betancourt (2005) observed
that 3% NaCl solution causes more scaling than 3%
MgCl2 solution. They recorded the lowest mass loss due
to surface scaling in the cases of CaCl2 and MgCl2
brines. In contrast, NaCl-based de-icer solution is much
less harmful to concrete than CaCl2 and MgCl2 de-icer
solutions with respect to chemical attack (Cody et al.,
1996; Sutter et al., 2006). NaCl may lead the formation of
chloroaluminate (Friedel’s salt), which does not cause
any significant expansion in concrete (Julio-Betancourt,
2009). However, the leaching of Ca(OH)2 can occur when
concrete is exposed to a concentrated NaCl de-icer
solution, and thus can slightly affect the properties of
concrete (Lea, 1998).
Chloride-based de-icer and anti-icer chemicals are a
common source of chloride ions that can penetrate
concrete surface. Numerous studies reported that the
ingress of chlorides accelerates the corrosion process in
reinforced concrete structures by damaging the protective
oxide (passive) film of the embedded steel reinforcement
(Melchers and Li, 2009; Pruckner and Gjørv, 2004;
Saremi and Mahallati, 2002). In addition, recent research
reports showed that CaCl2 and MgCl2 chemically interact
with hydration products and cause dissolution of the
hardened cement paste in concrete, thus forming expan-
sive oxychlorides (Sutter et al., 2008; Julio-Betancourt,
2009). The formation of oxychlorides results in cracking,
increased permeability, and a substantial loss of
compressive strength. Kozikowski et al. (2007) reported
that the presence of MgCl2 solution results in the
formation of magnesium silicate hydrate (M-S-H) and
brucite [Mg(OH)2], which cause concrete deterioration
due to physico-chemical changes. M-S-H lessens the
concrete strength at the expense of calcium silicate
hydrates (C-S-H), and Mg(OH)2 accelerates the
reinforcement corrosion by reducing the pH of pore
solution of the cement paste. Moreover, Darwin et al.
(2007, 2008) found that CaCl2 and MgCl2 cause concrete
damage due to both physical and chemical attacks. They
also found that the use of CaCl2 and MgCl2 had a
relatively high negative impact on concrete durability as
compared to NaCl. However, limited studies have been
conducted to examine the physical and chemical effects
of de-icer and anti-icer chemicals when applied onto
sealed or coated concrete surface.
Influence of salt concentration
The nature and extent of concrete deterioration depend
on the concentration of de-icer and anti-icer chemicals
(salt solutions). At a low concentration of salt solution, the
surface scaling of concrete is possible due to the physical
attack driven by freezing and thawing of the salt-ice
mixture (Hooton and Julio-Betancourt, 2005). The
pessimum concentration of de-icer salt solutions for the
maximum damage due to physical attack is 3 to 4% by
mass (Verbeck and Klieger, 1957; Çopuroğlu and
Schlangen, 2008). At lower concentrations ( 3 to 4%),
the salt solution can be frozen, and the formation of ice
and subsequent ice cracking intensify the physical
damage on the concrete surface. In contrast, the salt-ice
mixture can remain in liquid condition at higher
concentrations ( 3 to 4%), and therefore the surface
scaling of concrete due to freezing and thawing is not
expected. However, concrete deterioration can still
happen due to chemical attack (Julio-Betancourt, 2009;
Sutter, 2008).
The commercially available de-icer and anti-icer
products are highly concentrated solutions with a
concentration in the range of 16 to 32% by mass. In field
applications, some dilution occurs during de-icing and
anti-acing actions; yet the concentrations of de-icer or
anti-icer solutions remain high to avoid the refreezing of
salt-ice mixture. At high concentrations, the de-icer and
anti-icer solutions are expected to cause chemical attack
on concrete surface. Limited research has been carried
out to explore the chemical attack phenomenon of de-icer
and anti-icer solutions. The current knowledge on the
effects of de-icer and anti-icer chemicals are mostly
based on low concentrations ( 3 to 4% by mass) of
chloride solutions. Sutter et al. (2006) reported that a
concentrated solution of MgCl2 (15% by mass) results in
Mg(OH)2 (brucite) formation in the outer layer of concrete.
They also observed the formation of calcium oxychloride
in the presence of CaCl2. The formation of such products
is maximized at the pessimum concentration of de-icer
solutions. Sutter (2008) reported that the pessimum
concentration of MgCl2 is 20% and that of CaCl2 is 22%
with respect to chemical attack; these concentrations
cause the maximum damage in concrete. Also, Darwin et
al. (2008) reported that higher concentrations ( 15% by
mass) of de-icer chemicals cause concrete deterioration
more rapidly than lower concentrations under wetting and
drying conditions. Nevertheless, limited studies have
been conducted to investigate the effects of both low and
high concentrations of de-icer or anti-icer chemicals on
sealed or coated concrete surface.
Influence of exposure temperature
The ambient and concrete temperatures can influence
the effects of de-icer and anti-icer chemicals on concrete
damage. The minimum temperatures for applying NaCl,
MgCl2, and CaCl2 chemicals are -10, -15 and -25°C,
respectively (Mussato et al., 2004; Yehia and Tuan,
1998). No physical damage due to scaling occurs when
the temperature is maintained above -10°C in the case of
NaCl; the degree of damage increases with decreasing
temperature below -10°C (Valenza II and Scherer, 2007).
MgCl2 and CaCl2 can show similar effects based on their
minimum effective application temperatures as
mentioned earlier. However, it should be noted that these
temperatures will most likely vary depending on the
concentration of the chemical used. An increased
concentration can lower the minimum effective applica-
tion temperature, since the freezing point decreases as
the concentration increases (Sutter et al., 2008).
The damage of concrete due to chemical attack is also
affected by the ambient temperature. Julio-Betancourt
(2009) showed that the extent of chemical attack in the
presence of de-icer chemicals depends on the exposure
temperature; the lower the temperature, the higher the
rate of deterioration. In fact, he observed that a lower
temperature favours the formation of calcium and
magnesium oxychlorides, which are responsible for
damage in concrete. The lower temperature also reduces
the pessimum concentration of de-icer solutions (Julio-
Betancourt, 2009). However, limited studies have
investigated the role of temperature on the physical and
chemical attack phenomena of corrosive chemicals,
particularly when they are used on sealed or coated
concrete surface.
Influence of ice-layer thickness
The deterioration of concrete is significantly influenced by
the thickness of ice-layer on the concrete surface. An
increased thickness generates more force, and therefore
more damage occurs for the same number of freezing
and thawing cycles. Çopuroğlu and Schlangen (2008)
showed that a 9 mm increase in ice-layer thickness
resulted in 40% more mass scaling than a 1 mm
thickness after only 3 freezing and thawing cycles. Their
study also revealed that the rate of increase in mass
scaling per unit depth of de-icer solution lessens beyond
3 mm initial thickness of ice-layer. However, very few
studies have investigated the influence of ice-layer thick-
ness in the case of sealed or coated concrete surface.
SEALERS AND COATINGS
Sealers or coatings are applied as a surface treatment to
Safiuddin and Soudki 8191
protect the underlying concrete. They reduce the
penetration of water, de-icer or anti-icer chemicals, and
deleterious gases into concrete. To improve concrete
durability, sealers/coatings should possess the following
properties (Filice and Wong, 2001):
1. Ability to seal or coat new, old or previously
sealed/coated surfaces;
2. Ability to reduce or eliminate the ingress of moisture;
3. Excellent ability to transmit moisture vapour from
concrete;
4. Good salt scaling resistance;
5. Good chemical resistance;
6. Good resistance to ultra-violate rays;
7. Excellent adhesion to concrete surface.
Types of sealer and coating
Sealers and coatings are generally categorized as
follows:
1. Penetrating sealers: low viscosity materials, such as
silane or siloxane, which are “flood coated” to achieve a
nominal penetration (typically 1 to 3 mm) into the
prepared concrete substrates. By lining, but not blocking
capillary pores, they produce hydrophobic reactions,
which repel water and provide a high degree of “breath-
ability”.
2. Surface sealers: medium viscosity/low solids materials,
such as low solids epoxy and urethane and reacted
methyl methacrylate, which form films on the surface; the
films are not measurable and they do not penetrate within
the capillary pores to any degree. They typically have a
moderate degree of “breathability”.
3. Barrier or surface coatings: high viscosity/high solids
materials, such as acrylic, epoxy and urethane, which
form measurable coatings that do not penetrate capillary
pores. The applied coatings typically have degrees of
“breathability”, which vary from low to none.
4. Impregnating polymers: ultra-low viscosity monomer
materials, such as high molecular weight methacrylate,
styrene and acrylonitrile, which are applied using special
drying and vacuum techniques to ensure deep pene-
tration; when reacted, the polymers block the capillary
pores. They typically have a “breathability” varying from
low to none.
In Canada, the Alberta Transportation and Utilities
(ATU) department categorizes concrete sealers/coatings
as follows (ATU, 2009):
1. Type 1: Penetrating sealers. These products are
intended for use on traffic bearing surfaces subjected to
abrasion, and therefore must not affect skid resistance.
Type 1a is a sub-classification for use on concrete
surfaces where the relative moisture content is less than
8192 Int. J. Phys. Sci.
or equal to 55%. Type 1b is a sub-classification where
such relative moisture content is less than or equal to
70%. Type 1c is a sub-classification for high perform-
ance, low volatile organic compounds (VOC) penetrating
sealers for new bridges and overlays with low water/ce-
ment ratios where the relative moisture content is less
than or equal to 80%.
2. Type 2: Clear film forming sealers. These sealers form
a film on concrete surfaces and are intended for use on
non-traffic bearing surfaces. They are also known as
surface sealers. Type 2a is a sub-classification for one-
component clear products that are suitable for use on
concrete surfaces where the relative moisture content is
less than or equal to 70%. Type 2b is a sub-classification
for two-component clear products where such relative
moisture content is less than or equal to 70%.
3. Type 3: coloured film forming sealers. These sealers
are intended for use on concrete surfaces aesthetically
important and highly exposed to public view. These are
typically pigmented materials with a high solid content.
They are also known as surface coatings.
Effects of sealers and coatings
Sealers and coatings improve the durability of concrete
and thus extend the service life of concrete structures.
Porter (1975) showed that the use of sealers/coatings
greatly decreased surface scaling due to freezing and
thawing in the presence of water, although they had poor
resistance when exposed to the sun and outdoor
weathering. The Kentucky Transportation Center
reported that an appropriate sealer/coating system can
protect concrete from corrosion and de-icing salt
damages by inhibiting the chloride penetration (Palle and
Hopwood II, 2006). In contrast, it has been shown that
penetrating sealers are not as effective as surface
coatings in improving the scaling and corrosion
resistances of concrete (Ibrahim et al., 1999; Wenzlick,
2007). However, the performance of penetrating sealers
can be improved by an over-coat application of a surface
sealer or coating (Ibrahim et al., 1999).
The application of sealer or coating can significantly
impede the transport of water (with or without harmful
agents) into concrete by either rendering the surface
region hydrophobic or forming a physical barrier. Some
systems combine these two effects by the application of
dual-component products. A reduction in water uptake
can improve freeze-thaw durability (Litvan, 1992) and the
resistance to alkali-aggregate reactions (Filice and Wong,
2001). Al-Dulaijan et al. (2000), Ibrahim et al. (1999), and
Oshiro and Tanigawa (1988) reported that surface
coatings significantly reduce the chloride permeability
and reinforcement corrosion in concrete. Ho and Harrison
(1990) reported that surface coatings substantially inhibit
the ingress of carbon dioxide that leads to carbonation in
concrete. McCarter (1996) showed that surface coatings
restrict the passage of water into concrete but transmit
moisture vapour from concrete, and thus facilitate drying
of concrete elements. He also showed that some surface
coatings can significantly increase the resistivity of
concrete and improve the resistance to scaling due to
chemical attack. The scaling resistance of concrete was
also reported to greatly depend on the adhesion strength
of a surface coating (Al-Dulaijan et al., 2000; Oshiro and
Tanigawa, 1988). However, none of the aforementioned
studies focused the effect of high concentration of de-icer
and anti-icer chemicals, while investigating the perfor-
mance of sealers or coatings.
Selection of sealers and coatings
The performance of a sealer or coating depends not only
on its quality, type and/or properties, but also on the
exposure conditions both during application and in
service, condition of the underlying concrete surface
(smoothness, roughness, moisture level, etc.), substrate
preparation techniques, and how it is applied. Therefore,
the selection of a sealer or coating must be made after
full consideration of many factors (Table 1), which can
influence the achievement of its adequate performance.
Surface preparation for sealers and coatings
Surface preparation is typically required before the
application of sealers or coatings onto concrete surface.
Most manufacturers require that new concrete should be
at least 28 days old, and any contamination that may
interfere with adhesion or penetration, such as form oils
and curing compounds, should be removed (Attanayaka
et al., 2003). For similar reasons, oil, grease, rubber and
other contaminants should be removed from old
concrete. Additionally, the carbonated surface layer of old
concrete should be removed so that chemical reactions
requiring high alkalinity may be improved (Cady, 1994).
The most common surface preparation techniques
include abrasive-blasting (sand or grit-blasting), blast-
track (shot-blasting), and high pressure water-blasting. A
damp, saturated surface-dry or dry conditioned substrate
is required prior to the application of sealers and coatings
depending on the specific type of surface treatment.
Application of sealers and coatings
Sealers and coatings are typically applied on concrete
surface by roller, airless spray, and squeegee or
brush/broom (Filice and Wong, 2001). Attanayaka et al.
(2003) reported that the proper application of a
penetrating sealer increases its efficiency, and surface
flooding is the preferred method. Ho and Harrison (1990)
reported that the effectiveness of surface coatings
improves with increasing thickness. They found that the
Safiuddin and Soudki 8193
Table 1. Factors to be considered in sealer/coating selection (adapted from Basheer et al., 1997; Shields et al., 1992).
Feature Consideration
Type and condition of concrete substrate New or old concrete
Surface condition (prior treatment, roughness, contamination, etc.)
Exposure environment
Atmospheric, buried, marine, etc.
Presence of moisture
Presence of pollutants
Aggressive chemicals
Nature of concrete protection needed
Abrasion
Acid/chemical attack
Alkali-aggregate reaction
Carbonation
Chloride permeability
Freezing and thawing
Salt scaling
Sulphate attack
Water absorption
Wetting and drying
Sealer/coating durability
Abrasion resistance
Adhesion strength
Chemical resistance
Colour retention
Elasticity
Film hardness
Impact resistance
Moisture vapour transmission
Toxicity
UV resistance
Water resistance
Service condition Skid resistance
Application of sealer/coating
Methods of application
Surface preparation
Temperature dependence
Tolerance to substrate moisture
Site access
8194 Int. J. Phys. Sci.
Table 1. Contd.
Overall cost
Coverage rate or number of coats required
Film thickness
Labour cost
Material cost
Maintenance cost
thicker coating layer enhances protection against
carbonation by reducing the diffusion of carbon dioxide.
They also found that a coating applied to a sand-blasted
formed concrete substrate is less effective than when it is
applied at a similar coverage rate to a non-prepared
surface. This is because the sand-blasting typically
produces a roughened profile, requiring an increased
coverage rate to achieve a uniform film formation
thickness that is free from defects, such as holidays or
pin-holes. However, the sand-blasting is still required to
achieve effective adhesion of the coating and an
increased coverage rate is therefore typically recom-
mended.
Evaluation of sealers and coatings
American Society for Testing and Materials (ASTM) has
several test methods to evaluate the performance of
coatings. ATU has developed several test methods for
evaluating the performance of sealers and coatings when
applied onto concrete surface (ATU, 2000a, 2000b,
2000c). Cady (1993) used a two-pin mode soil resistance
meter to evaluate the effectiveness of concrete sealer or
coating with respect to electrical resistance. Also, ASTM,
American Association of State Highway and
Transportation Officials (AASHTO), and Canadian
Standards Association (CSA) have a number of test
methods for concrete that can be used with necessary
modifications to evaluate the performance of sealers and
coatings. The lists of AASHTO, ASTM, ATU, and CSA
test methods/practices/specifications are appended
(Appendix).
Performance criteria for sealers and coatings
The performance criteria for the durability and durability-
related properties of concrete sealers and coatings are
listed in Tables 2 to 4. These performance criteria deal
with physical (adhesion, resistance to freeze-thaw/salt
scaling, and resistance to weathering), transport (water
absorption, waterproofing, chloride permeability/
penetration, crack sealing ability and moisture vapour
transmission), and electrical (electrical resistance)
properties of concrete treated with sealer or coating.
None of these criteria considers the chemical attack
mechanisms of de-icer or anti-icer chemicals to evaluate
the performance of sealers and coatings when applied on
concrete surface.
RESEARCH NEEDS
More research is needed in the following areas:
1. Performance of concrete sealers and coatings under
different aggressive environments, such as freezing and
thawing, wetting and drying, and extreme temperature
changes with different chemical exposures.
2. The chemical attack of de-icer and anti-icer solutions,
and their damage mechanisms on concrete surface
treated with sealers or coatings.
3. The influence of high concentration of de-icers or anti-
icers on the protective performance of concrete sealers
and coatings.
4. The influences of temperature and ice-layer thickness
on the protective performance of concrete sealers and
coatings.
5. Identification of proper surface preparation techniques
for concrete substrate for applying sealers and coatings.
6. Detection of appropriate application methods for
applying sealers and coatings onto concrete surface.
7. Standardization of test methods and development of
performance criteria for concrete sealers and coatings.
CONCLUDING REMARKS
1. Environmental factors such as freezing and thawing,
wetting and drying, etc., can result in concrete
deterioration in bridge structures; the damage can be
accelerated by de-icer and anti-icer chemicals commonly
used for highway maintenance during winter.
2. The most common forms of deterioration are surface
scaling, spalling, and corrosion induced cracking and/or
delamination of concrete. The degree of damage greatly
depends on the type and concentration of de-icer or anti-
icer solution, exposure temperature, ice-layer thickness,
as well as on the severity of the mechanisms of attack.
3. The application of sealers or coatings can protect the
concrete from damages caused by the aggressive
Safiuddin and Soudki 8195
Table 2. Various perf ormance criteria for concrete sealers/coatings (Cady, 1993; Wenzlick, 2007).
Method Property Performance criteria
Salt scaling
(ASTM C 672/C 672M)
Scaling resistance to salt exposure under
freezing and thawing Rating “0”, no scaling after 100 cycles
Crack sealing
(Modified AASHTO T 259) Ability of crack sealing Water leaking time ratio of sealed and
unsealed concrete 2
Absorption by water saturation technique
(ASTM C 642) Water absorption as an indicator of durability Maximum 1% after 48 hours;
maximum 2% after 50 days
Chloride ion penetration
(AASHTO T 259)
Penetrated chloride value as an indicator of
corrosion resistance
Maximum 0.76 - 1.0 pcy at 0.50 - 1.0
in (0.451 - 0.593 kg/m3 at 12.7 - 25.4
mm) depth after 90 days of ponding
Accelerated weathering
(ASTM D 822) Weathering resistance Slight colour change
Salt spray resistance
(ASTM B 117) Adhesion No loss of adhesion after 300 cycles
Two-pin mode soil resistance meter Electrical resistance > 200 - 400 k
Table 3. Waterproofing performance criteria for concrete sealers/coatings (ATU, 2009).
Sealer/coating type Minimum waterproofing performance (as compared to control specimens
1
) (%)
Before abrasion After abrasion
Type 1a 82.5 75.0
Type 1b - 86.0
Type 1c - 85.0
Type 2a 82.5 N/A
Type 2b 90.0 N/A
Type 3 75.0 N/A
1Unsealed/uncoated concrete specimens
Table 4. Moisture vapour transmission performance criteria for concrete sealers/coatings (ATU, 2009).
Sealer/coating type Minimum vapour transmission (as compared to control specimens
1
) (%)
Type 1a -
Type 1b 70.0
Type 1c 85.0
Type 2a 35.0
Type 2b 20.0
Type 3 35.0
1Unsealed/uncoated concrete specimens
environmental and chemical exposures. The performance
of sealers and coatings depends on the type and
properties of the selected product, and on the
effectiveness of the surface preparation and application
8196 Int. J. Phys. Sci.
techniques.
4. More research is needed to evaluate the performance
of concrete sealers and coatings under different
aggressive environments and chemical exposures;
standardization of test methods and development of
performance criteria are also required for the successful
application of these products.
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8198 Int. J. Phys. Sci.
APPENDIX
Test methods, practices and specifications for concrete, sealers, and coatings
AASHTO test methods
1. AASHTO T 22: Standard method of test for compressive strength of cylindrical concrete specimens.
2. AASHTO T 161: Standard method of test for resistance of concrete to rapid freezing and thawing.
3. AASHTO T 259: Standard method of test for resistance of concrete to chloride ion penetration.
4. AASHTO T 260: Sampling and testing for chloride ion in concrete and concrete raw materials.
5. AASHTO T 277: Standard method of test for electrical indication of concrete’s ability to resist chloride ion penetration.
ASTM standard practices and test methods
1. ASTM B 117: Standard practice for operating salt spray (fog) apparatus.
2. ASTM C 39/C 39M: Standard test method for compressive strength of cylindrical concrete specimens.
3. ASTM C 215: Standard test method for fundamental transverse, longitudinal, and torsional frequencies of concrete
specimens.
4. ASTM C 642: Standard test method for density, absorption, and voids in hardened concrete.
5. ASTM C 666/C 666M: Standard test method for resistance of concrete to rapid freezing and thawing.
6. ASTM C 672/C 672M: Standard test method for scaling resistance of concrete surfaces exposed to deicing
chemicals.
7. ASTM C 793: Standard test method for effects of accelerated weathering on elastomeric joint sealants.
8. ASTM C 1152/C 1152M: Standard test method for acid-soluble chloride in mortar and concrete.
9. ASTM C 1202: Standard test method for electrical indication of concrete’s ability to resist chloride ion penetration.
10. ASTM C 1543: Standard test method for determining the penetration of chloride ion into concrete by ponding.
11. ASTM C 1645/C 1645M: Standard test method for freeze-thaw and de-icing salt durability of solid concrete
interlocking paving units.
12. ASTM D 522: Standard test methods for mandrel bend test of attached organic coatings.
13. ASTM D 822: Standard practice for filtered open-flame carbon-arc exposures of paint and related coatings.
14. ASTM D 1653: Standard test methods for water vapour transmission of organic coating films.
15. ASTM D 1654: Standard test method for evaluation of painted or coated specimens subjected to corrosive
environments.
16. ASTM D 2243: Standard test method for freeze-thaw resistance of water-borne coatings.
17. ASTM D 2794-93: Standard test method for resistance of coatings to the effects of rapid deformation (impact).
18. ASTM D 3273: Standard test method for resistance to growth of mold on the surface of interior coating in an
environmental chamber.
19. ASTM D 3274: Standard test method for evaluating degree of surface disfigurement of paint films by microbial
(fungal and algal) growth or soil and dirt accumulation.
20. ASTM D 4541: Standard test method for pull-off strength of coatings using portable adhesion testers.
21. ASTM D 4585: Standard practice for testing water resistance of coatings using controlled condensation.
22. ASTM D 4587: Standard practice for fluorescent UV-condensation exposures of paint and related coatings.
23. ASTM D 5894: Standard practice for cyclic salt fog/UV exposure of painted metal (alternating exposures in a fog/dry
cabinet and a UV/condensation cabinet).
24. ASTM D 6489: Standard test method for determining the water absorption of hardened concrete treated with a water
repellent coating.
25. ASTM E 96/E 96M: Standard test methods for water vapour transmission of materials.
Alberta Transportation and Utilities (ATU) specifications and test methods
1. B388: Specification for concrete sealers.
2. BT001: Test procedure for measuring the vapour transmission, waterproofing, and hiding power of concrete sealers.
3. BT005: Test procedure for measuring the waterproofing performance of core samples taken from sealed concrete
surfaces.
4. BT002: Test procedure for alkaline resistance of penetrating sealers for bridge concrete.
Safiuddin and Soudki 8199
CSA test methods
1. CSA A23.2-24A: Test method for the resistance of unconfined coarse aggregate to freezing and thawing.
2. CSA A23.2-4B: Sampling and determination of water-soluble chloride ion content in hardened grout or concrete.
3. CSA A23.2-9C: Compressive strength of cylindrical concrete specimens.
4. CSA A23.2-11C: Water content, density, absorption, and voids in hardened concrete, grout or mortar.
5. CSA A23.2-21C: Test method for length change of hardened concrete.
... Currently there are over half a million bridges and decent number of subsutural systems in need of evaluations for repair and rehabilitation in the United States. The severity of crack in concrete piles could vary from minor concrete spalls to complete fracture (Safiuddin & Soudki, 2011). Knowing that concrete piles replacement is a non-conservative, costly, time consuming and complex operation, it is necessary for federal and state agencies to develop a safe and appropriate method of assessment and repair. ...
... Static cracks can be repaired through epoxy injection, grouting, routing and sealing, drilling and plugging, stitching, adding reinforcement, and overlays and surface treatments. Live cracks can be repaired using flexible sealants ( (Safiuddin & Soudki, 2011). Determining the best approach for crack repair can be a difficult course of action. ...
... Extremely Importance (7,8,9) (1/9,1/8,1/7) 9 ...
Article
The effectiveness of any structural repair or rehabilitation process depends on the proper evaluation of its deterioration state, appropriate repair technology selection from alternatives, and consideration of implementation strategies. Pile repair technologies ranges from replacement and installation of supplemental piles to a wide range of pile wraps and jackets to restore strength and provide added protection from further deterioration. These projects, more often than not, involve significant agency resources of manpower and monetary cost due to possible instances of inaccessibility of these substructures under water and adaptability of repair approach, therefore many agencies continue to seek effective assessment measure that result in longer-lasting and more effective repair strategy that considers site-specific conditions. Since the integrity of these concrete pile structures invariably has an effect on its structural life, underwater cracks must be well assessed for appropriate remediation considering both short and long-term consequences. Although there are sundry of repair and protection techniques adopted by many agencies, decision on appropriate repair solution must consider accessibility of repair and adaptability of the structural repair bearing in mind site-specific conditions. To assist in a rational repair decision-making process for moderate to severe crack damage conditions, this study aims to (1) gather information regarding crack assessment and common repair technology in order to make effective comparisons between rehabilitation methods 2) Utilize Fuzzy AHP method, a multi-criteria decision making model in ranking underwater concrete pile repair technologies based on cost and effectiveness criteria.
... Proceeding from this, for the development of the method, it is necessary to determine the scientific provisions that make it possible to transform the real processes of repeated loading and ultraviolet irradiation into equivalent laboratory modes corresponding to the operational ones in terms of damageability. At the same time, laboratory modes should contain factors that accelerate the process of assessing durability in comparison with full-scale tests, because only in this case the effectiveness of the method is manifested [1][2][3][4][5]. ...
Article
Full-text available
The article discusses the hypotheses for determining the equivalent laboratory modes for assessing the durability of sealing and awning materials, and evaluates the accuracy of the proposed method. Qualitative research of operational factors influence (UV, temperature) on sealing and awning materials durability was conducted. Purpose of the study: a method for predicting the durability of sealing and awning materials. Methods: Methods for fast assessment of durability and methods of equivalent factors. Results: Based on the obtained regularities of the behavior of sealing and awning materials under conditions of repeated loading and ultraviolet radiation, as well as the accepted hypotheses about the summation of damage and irreversibility of the destruction process, a laboratory test mode was determined that was equivalent in terms of the level of introduced destruction to the operating mode, including the action of multiple loads and ultraviolet radiation. Based on the equivalent accelerated test mode and the characteristics of the operating mode of loading and irradiation, a method for assessing the durability of sealing and awning materials is proposed.
... In this study, to prevent the fly ash concrete from the harsh environments, acrylic resin and epoxy resin have been planned for external coating of fly ash concrete (Seneviratne et al. 2000). It has been reported that to prevent the concrete structure from the deterioration, coating of concrete reduces the water penetration and chlorides and sulfate ions (Barbucci et al. 1997;Safiuddin and Soudki 2011;Shi et al. 2012). It has been recommended that acrylicmodified cementitious coating is efficient in resolving the corrosion issues of roadside structures (Guo et al. 2017). ...
Article
Full-text available
This study is focused on polymeric coatings on fly ash concrete submerged under seawater. The specimens were casted and coated with acrylic resin and epoxy resin of three layers each. The mechanical, durability, and microstructural properties of coated and uncoated fly ash concrete specimen were studied as pre- and post-exposed in seawater. Fly ash concrete coated with epoxy and acrylic had attained more strength compared to uncoated specimens. An increased strength in coated specimens and a decrease in value were observed in uncoated fly ash concrete specimens during split tensile strength. Coated specimens showed less reduction in pH value as compared to uncoated specimens. Rapid chloride permeability test (RCPT) analysis confirmed that epoxy and acrylic-coated concrete specimens appear to be denser than uncoated specimens leading to more resistance against the penetration of aggressive chemicals. The X-ray diffraction (XRD) comparative analysis of 56 and 90 days acrylic resin and epoxy resin-coated and uncoated specimen showed higher intensity in 90 days coated specimens than the uncoated specimens. Field emission scanning electron microscope (FESEM) investigation of uncoated 56 and 90 days concrete specimens subjected to seawater demonstrated dense appearance of hydrated products, whereas epoxy and acrylic-coated specimens were verified with no visible micro-cracks or holes on the surface, even at higher magnification. The epoxy and acrylic-coated fly ash concrete showed high physical strength and good bonding with concrete and will be appropriate for construction.
... In order to overcome this issue, it was decided to move from sodium silicate coating to epoxy coating, which has been demonstrated to be one of the most effective materials to guarantee high standard of sealing and waterproofing [28,262,264,265]. ...
Thesis
Concrete is the most widely used building material on earth. However, concrete structures present several issues that threaten their durability and consequently the safety of their users. One of the major hindrances to the durability of concrete is its susceptibility to cracking. Cracking leads to the reduction of mechanical properties and contributes to create pathways for the penetration of aggressive agents into the bulk material. In order to avoid major durability problems, concrete structures need to be repaired, but repair works can present several issues such as the individuation and access to the damaged zones, the direct cost to realize them, the indirect cost connected to the loss of serviceability, and the environmental impact in terms of carbon dioxide emissions for the production of new cement. In the last decade, significant advancements have been achieved concerning the enhancement of the longevity of the cementitious structures using preventive repair methods defined as self-healing techniques. These techniques may be implemented based on the autogenous healing mechanisms naturally present in cement-based materials and through strategies aimed to improve it or to built-in new autonomous healing properties. Among these technologies, capsule-based self-healing using macro-encapsulation is being increasingly acknowledged as a promising strategy to improve the durability and resilience of concrete structures. The focus of this dissertation was the development and characterization of an efficient self-healing system using cementitious capsules filled with a suitable healing agent. The system should be able to provide repair directly at the damage location upon crack occurrence and achieve recovery in both durability-related and mechanical properties, also in presence of large cracks. The research activities led to the development of a new manufacturing technique, which allowed to produce cementitious capsules with controlled and customizable dimensions using a polymer-modified cement paste. Moreover, the adopted coating and sealing procedures allowed the encapsulation of highly moisture-reactive healing agents. The capsules were used to successfully encapsulate and release several types of healing agents from the main types commonly used for self-healing applications: namely, sodium silicate solutions and water-repellent agents (minerals), highly moisture-reactive polyurethane precursors (polymers), and ureolytic bacterial strain Bacillus sphaericus able to precipitate calcium carbonate (bacteria). The investigation and comparison of the performances of the different healing agents allowed to select the polyurethane precursors as the most promising to realize the desired self-healing system. Moreover, the cementitious capsules were proven effective in resisting the mixing procedure. This characteristic, combined with their inherent compatibility with the cementitious matrix and the easy customization of the capsules size and shape, makes cementitious capsules equivalent to enhanced aggregates that could be used in the ordinary construction processes. The development of the final system followed several steps, with the aim to progressively improve it through the inputs offered by the characterization of intermediate tentative systems. For what concerns the characterization in terms of recovery of durability-related properties, the sealing efficiency was assessed through the reduction of capillary water absorption and water permeability offered by the autonomous healing system. The tests were conducted using both testing techniques present in the relevant literature and novel techniques developed in the frame of this doctoral study. Specifically, a newly developed water permeability test allowed to characterize the system efficiency using stricter testing conditions. As regards the recovery of the mechanical properties, this was first investigated via three-point bending test in order to apply indirect tensile stresses in static loading conditions, as in most of the scientific literature. Furthermore, the mechanical behavior was also tested in repeated cyclic loading conditions until rupture in order to obtain insights regarding the seldom studied fatigue performance of the self-healing systems. In fact, this is an aspect of paramount importance to develop a reliable autonomous repair system that can be used in real field conditions. The performances of the self-healing system using cementitious capsules were also compared with those of a system using glass capsules, which is an encapsulation technique thoroughly studied by several research groups and that served as a benchmark for the newly developed system. This comparison was obtained through the application of a test protocol developed in the framework of a European inter-laboratory testing. This allowed also to prove the protocol applicability to different self-healing cementitious materials based on the use of macro-capsules. Visual analyses of the crack faces were also carried out to estimate the spreading of the healing agent in order to complement the previous characterizations. In conclusion, the main objective set for this doctoral thesis was achieved, namely the development and characterization of an efficient self-healing system for cementitious materials based on the encapsulation of polyurethane in newly-designed cementitious capsules. The final self-healing system allowed to obtain almost full recovery in both durability-related and mechanical properties after damage occurrence, proving that the system is able to improve the durability of cementitious structures and has a good potential for future scale-up.
... However, empirical data are not readily available for robustly calibrating the efficacy of the membrane in terms of its effectiveness of eliminating/reducing moisture in the RC deck over its service life. For instance, Safiuddin and Soudki (2011) showed that limited studies have been conducted to examine the physical and chemical effects of deicing salts when applied to protected concrete. Given the lack of field research on effectiveness of membranes/sealers, more empirical studies are needed to better inform this important module incorporated into RC bridge service life prediction models. ...
Article
Climate change is expected to impact both the operational and structural performance of infrastructure such as buildings, roads, and bridges. However, infrastructure design guides widely rely on historical climate data, if any, for informing design requirements. The goal of this research was to explore a methodology for modeling bridge deck design against corrosion attack in a changing climate. Three deterioration stages were simulated to understand the time to deck failure. Corrosion initiation of reinforcing steel was considered by utilizing a deterministic diffusion-based model predicting the time to reinforcement corrosion initiation. Crack initiation and crack growth were also simulated using mechanistic approaches to illustrate the sensitivity of bridge deck deterioration and design service life to changes in bridge deck design and a changing climate across major cities in Canada. The findings indicate that a changing climate has the potential to significantly alter the service life of a bridge deck, but the effect is strongly dependent on the durability design of the bridge deck. It is recommended that bridge designers strive to utilize mechanistic-empirical models that incorporate high-resolution climate data as inputs for better understanding changes in deterioration as a consequence of a nonstationary climate.
... These materials inhibit chloride penetration through diffusion and absorption of contaminated water. Various types of products have been introduced for concrete surface protection, including coatings, water repellents, and pore blockers [7][8][9][10]. The surface treatment methods for concrete can be classified into three groups [11]: (a) coating (to form a continuous film on the concrete surface); (b) impregnation (to react with certain soluble concrete constituents and form insoluble products); and (c) hydrophobic impregnation (to make the concrete water repellent). ...
Article
Utilizing surface protection materials with high barrier properties and hydrophobicity is a method for concrete protection to extend its lifetime. This paper aims to investigate whether graphene oxide (GO) can be applied as surface protection of concrete to prevent the transmission of water and ingress of chloride ions. The best method for applying GO and the effectiveness of the amount of GO on its performance to reduce the permeability of concrete surface were evaluated as well. Results indicated that at best GO coating on the concrete surface can reduce water absorption and capillary absorption of concrete by about 40 and 57%, respectively. The increase in the GO content leads to more reduction of water absorption and capillary absorption of concrete. GO can be applied to the surface of the existing and casting concrete structures through spraying and submerging methods, respectively. It was demonstrated that at best GO coating reduces the chloride ion penetration of concrete by about 25% while it has no tangible effect on water vapor permeability of concrete. The results of this research could open a window for developing a new generation of concrete surface protection material.
Chapter
Volume 5B addresses the subject of organic protective coatings, the most widely used preventative in the battle with rust and corrosion. It covers the entire spectrum of organic coating materials from acrylics, alkyds, and epoxies to powder coats, waxes, and zinc-rich blends. It compares and contrasts coating properties, describes where and how specific coatings are used, and presents qualification testing and surface preparation procedures. The volume also provides introductory information on chemistry, composition, and the role of pigments, resins, additives, and solvents. For information on the print version of Volume 5B, ISBN: 978-1-62708-081-1, follow this link.
Article
The paper presents the results of the study of underwater repair concrete under the effect of the salt mist. The research was conducted in accordance with the standard PN-EN 14147. Concrete samples for testing the corrosive elements of that test were taken during the first 7 days of insight in the pressure vessel and were subjected to hydrostatic pressure effects from 0,1 to 0,5 MPa. The beneficial effect of hydrostatic pressure on the corrosion resistance of tested concrete repair was. Was observed samples taken from the surface layers of the tested elements showed slightly higher resistance to chlorides which confirmed the characteristics of pore distribution of concrete in the studies.
Article
The combination of continued highway bridge aging and constrained maintenance, repair, and replacement budgets create the pressing need to develop strategies to allocate available management resources most effectively. Strategies for preventative maintenance scheduling and budget projection greatly depend on the ability to predict bridge deterioration. Mechanistic deterioration models, which analyze the physical processes causing deterioration, have the potential to supplement purely statistical deterioration models and to address limitations associated with bridge inspection data and statistical methods. A variety of mechanistic models that consider specific aspects of deterioration processes is available in the literature. This study considered how existing mechanistic models for predicting corrosion-induced cracking of RC bridge decks can be assembled into a comprehensive model that can predict the complete deck service life and be used to propose preventative maintenance schemes for the decks. The construction practices of modern RC bridge decks were investigated and an attempt was made to assemble a mechanistic model, including the effects of epoxy-coated rebar, waterproofing membranes, asphalt overlays, joint deterioration, and deck maintenance. In some cases, new temporary models had to be proposed to fill gaps in existing modeling capabilities. After a complete model was assembled, Monte Carlo simulation with probabilistic model inputs was applied to simulate the inherent randomness associated with deterioration. The results of this effort indicated that mechanistic models are, indeed, promising, and well-timed preventative maintenance may provide longer bridge deck service life with fewer total maintenance actions than current methods do. However, experimental studies of specific deterioration processes and additional bridge data collection are needed to supplement existing models and validate model predictions.
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