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A surface engineering approach applicable to concrete repair engineering

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In this paper, the effect of substrate roughness and superficial microcraking upon adhesion of repair systems using concrete surface engineering approach is analyzed. And the results obtained confirm also that Concrete Surface Engineering, as a scientific concept, will definitely contribute to shed more light on how to optimize repair bond, taking into account interactions between the materials at different observation scales.
Abstract
The objective of the paper is to analyze the effect of substrate roughness and superficial microcraking upon adhesion of repair systems using concrete surface engineering approach. The results presented in this paper have been obtained within the framework of research projects performed to develop a better understanding of the factors affecting the adhesion of repair materials through a surface engineering approach. Based on the results of investigations, the authors showed that the durability and quality of concrete repairs depend to a large degree on the characteristics of the substrate. Mechanical preparation and profiling of the concrete surface to be repaired has to be balanced with potential co-lateral effects such as superficial cracking, too often induced as a result of inappropriate concrete removal method selection, and the loss of benefits due to better mechanical anchorage. The results obtained confirm also that Concrete Surface Engineering, as a scientific concept, will definitely contribute to shed more light on how to optimize repair bond, taking into account interactions between the materials at different observation scales.

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BULLETIN OF THE POLISH ACADEMY OF SCIENCES
TECHNICAL SCIENCES, Vol. 61, No. 1, 2013
DOI: 10.2478/bpasts-2013-0006
CIVIL ENGINEERING
A surface engineering approach applicable
to con crete repair engineerin g
A. GARBACZ
1
, L. COURARD
2
, and B. BISSONNETTE
3
1
Department of Building Materials Engineering, Institute of Building Engineering, Warsaw Universi ty of Technology,
16 Armii Ludowej Ave., 00-637 Warsaw, Poland
2
ArGEnCO Department, University of Liege, Chemin des Chevreuils, 1 (Bat. B.52), 4000 Liege, Bel gium
3
Research Center on Concrete Infrastructure, Civil Engineering Department, Laval Universit y, Qu
´
ebec, Canada, G1K 7P4
Abstract. The objective of the paper i s to analyze the effect of substrate roughness and superficial microcraking upon adhesion of repair
systems using concrete surface engineering approach. The results presented in this paper have been obtained within the framework of
research projects performed to develop a better understanding of the factors affecting the adhesion of repair materials through a surface
engineering approach. Based on the results of investigations, the authors showed that the durability and quality of concrete repairs depend
to a large degree on the characteristics of the substrate. Mechanical preparation and profiling of the concrete surface to be repaired has to be
balanced with potential co-lateral effects such as superficial cracking, too often induced as a result of inappropriate concrete removal method
selection, and the loss of benefits due to better mechanical anchorage. The results obtained confirm also that Concrete Surface Engineering,
as a scientific concept, will definitely contribute to shed more light on how to optimize repair bond, taking into account interactions between
the materials at different observation scales.
Key words: durability of concrete structure, repair, adhesion, surface roughness, microcracking, surface engineering.
1. Introduction
The deterioration of concrete structures is a major problem
in many cou ntries througho ut the world. Durability of the
structures, maintenance and conservation, repairs and mod-
ernization are also important research area s for sustainable
develo pment in constru c tion [1–3]. To reach a desired dura-
bility of new concrete structures a s well a s existing str uc-
tures (repair), three main types of surface concrete quality
improvem ent are considered (formalize d also in the European
Standard EN 1504) [4]:
improvement of near- to-surface layer quality by hydropho-
bic treatment or impregnation;
removal of d e te riorated concrete and repair with fresh mor-
tar;
application of adhe sive coating to improve ba rrie r proper-
ties.
Therefore mentioned approach emphasises that the prop-
erties of th e near-surface layer influence bar rier properties of
concrete and in consequence its durability [5, 6]. Such ap-
proach shares characteristics with surface engineering com-
monly applied to many construction materials like metal al-
loys, includ ing nanomaterials, eg. [7, 8]. Surface engineering
is defined [7] as a scientific and technological app roach relat-
ed to the design, the production and the application of surface
layers to improve some properties o f the substrate, particularly
the resistance to corrosion and abrasion, as well as aesthetic
properties. Surface engineering covers all phenomena involv-
ing a modification of the near-to-surface layer and/or applica-
tion of a coating suitable for a given application. In all cases,
suitable scientific tools are necessary to characterize proper-
ties of layer, quality of substrate and adhesion o f coating to
substrate.
The surface engineerin g approach is still rarely applied
in civil engineerin g, especially for concrete-like composites
in concrete re pair engineering (Fig. 1) . However, according
to the authors, this scientific approach allows to explain phe-
nomena underlying durability of repair an d anticorrosion pro-
tection of concrete structures [9, 10], which directly depend
on the adhesion quality. Favorable con ditions d uring the phase
of cr e ation of the bond between the substrate and the new lay-
er will g uarantee the longevity of adhe sio n and, consequently,
of the repair. The high adhesion level creates higher tolera nce
to some inc ompatibility between the bonded materials, partic-
ularly in the case of concrete-po lymer co mposite repairs on
concrete substrate [11, 12].
Fig. 1. Number of papers related to “surface engineering” for differ-
ent categories in the ScienceDirect database of all Elsevier journals
e-mail: a.garbacz@il.pw.edu.pl
73

A. Garbacz, L. Courard, and B. Bissonnette
2. Definitions of adhesion
The ab ility o f two bodies to associate in order to form an
assembly or a composite material, is due to the creation of an
interface between th ese two materia ls [13]: from a thermody-
namic point of view, this means that the work of adhesion is
grea te r than the work of c ohesion. In order to find the link
between cause and effect, one has to define and to me asure
exactly the electr ic al, molecular and atomic forces existing
between the materials (Fig. 2) and to evaluate the topogra-
phy of the surface. The measured adhesion, eg. by pull-off
test, is a quantitative interpretation of the force or the energy
necessary to separate the bodies [13 ]. This lead Sasse [14] to
formulate two interpretations of adhe sio n definitions:
Definition 1. “Forces in the boundary surface, which result
in the mutual a dhesion of two materials in contac t”. This is a
qualitative equilibrium problem, w hich lea ds to the question:
“What is the reason for the attraction between the two ma-
terials in contact?” The objective under consider ation is the
formation of the adhesive bond.
Definition 2. “The fracture stress or another quantified me-
chanical characteristic for the resistance against separation
of two materials in contact”. T his is a quantitative, not
equilibrium-relate d problem, which leads to the question:
“Which magnitude has the resistance against separation?” The
objective und e r consideration is the separatio n of the adhesive
bond.
Most theoretical considerations are based upon definition
1 and most experimenta l investigations use definition 2. Be-
sides th e “mechanical adhesion” theory (interlocking mechan-
ical effects) there are three main “specific adhesion” theories
(Fig. 2).
Fig. 2. Principles of adhesion after Ref. 14
In the case of a system created through repair, adhesion
depends on many phenomena taking place in the interfacial
zone [ 15, 16]: presence of bond-detrimental layers or in clu-
sions (including bleeding), wettability of the substrate by re-
pair materials, secondary physical attraction forces (van der
Waal forces) ind uced in the system, surface roughness (in-
terlocking mechanism), respective moisture contents in the
concrete substrate and repair system (e.g. cement concrete or
polymer composite), microcracks left or in duced by the sur-
face treatment. This implies that there can be very significant
differences between theoretical a nd experimental strengths ev-
idencing about the limits of the classical theorie s if defini-
tion 2 is considered (Table 1).
Table 1
Theoretical and experimental adhesion strength values compiled from
different authors [14]
van der Waal forces
Adhesion strength (N/mm
2
)
Theoretical technical, experimental
permanent dipoles 200–1800
5–20
induced dipoles 40–300
dispersion forces 60–360
hydrogen bonds about 500
According to Silfwerbrand (Table 2), the creation and
durability of bond depend on seve ral factors having different
deg rees of influence, which can be d ivided into three main
groups [17].
Table 2
Factors affecting bond between concrete substrate and repair m aterial
(acc. [17])
Factors
Importance
1 2 3
Substrate characteristics
Substrate properties X
Microcracking X
Laitance X
Roughness X
Cleanliness X
Overlay characteristics & application technique
Pre-wetting X
Bonding agents X
Overlay proper ties X
Placement X
Compaction X
Curing X
Environmental conditions
Time X
Early traffic X
Fatigue X
Environment X
The objective of this paper is to analyze the effect of sub-
strate roug hness and superficial microcraking u pon adhesion
of repair systems. The results presented in this paper were
obtained in the framework of research projects performed at
University of Li
`
ege in Belgium, Laval University in Canada
and Warsaw University of Technology in Poland in tending
to develop a better understanding of the factors affecting the
adhesion of repair materials through a surface engineering
approa ch.
3. Surface roughness
3.1. Roughness characterization. The surface treatment of
a concrete substrate is important in order to promote me-
chanical adhesion [18]. The methods for measuring rough-
ness and surface texture can be classified into three types
74 Bull. Pol. Ac.: Tech. 61(1) 2013

A surface engineering approach applicable to concrete repair engineering
[19]: contact methods, non-co ntact (optical) methods, an d the
taper sectioning method. Among the contact methods there
are mechanical profilometers (extensometer-mounted), tactile
tests, kinetic f ric tion measuring device, static friction m e a-
surement, rolling -ball measu rements, and measureme nt of the
complianc e of a metal sphere with a rough sur face. Opti-
cal (non-c ontact) m e thods include optical reflecting instru-
ments, light microscopy, e le ctron microscopy, spe ckle metrol-
ogy, opto-morphology (interferometry) and laser profilo metry.
Taper sectioning is used in metallurgy and basically consists in
cutting across a surface at a low angle α to physically amplify
the height of asperities (ctg α). In this paper, the effective-
ness, accuracy and field applicability of selected techniques
[20–32], which are listed in Table 3, are analyzed.
3.2. Profile description. After treatment, concrete surfaces
present fractal topogra phy. As for any fractal object, it is pos-
sible to brea k up this surface or pr ofile into a sum of sub-
profiles [9]. Each sub-profile can be differentiated in terms
of wavelengths; there is however no limit or precise criteri-
on to validate the decomposition process (Fig. 3). It is al-
so possible to filter the result mathematically [23]. Using
methods with differen t resolutions, complem entary topogra-
phy scales can be characterized. The mechanical pr ofilometry
method, which has high resolution, reaches surface roughness
scales referred to as roughness (R) and waviness (W). The
opto-m orphological method, with a resolution of 0.2 µm, al-
lows characterization of roughness scales referred to as meso-
wav iness (M) and form (F). In mechanical profilometry a dif-
ferentiation filtering process based upon the stylus diameter
is often used. Then, the vertical and horizontal amplitude de-
composition parameters the most common according to EN
ISO 4287 (Table 4) are calc ulated. Another useful parameter
Table 3
General characteristics of techniques of roughness evaluation
Technique/reference data Example General characteristics
ICRI Concrete
Surface Profiles
[20–22]
Visual evaluation of concrete surface morphology
with concrete surface profiles (CSP plaques 03732)
Sand patch test
EN 13036-1
(ASTM E965)
EN 1766
Calculation of surface roughness ratio using diame-
ter of sand circle spreading on the surface: SRI =
V
SRI
d
2
SRI
· 1272 [mm]
Mechanical
profilometry
[22–24]
A high-precision extensometer is moved all over the
surface to obtain a 3-D mapping (x, y, z coordinates);
morphological parameters are computed for selected
profiles in accordance with EN ISO 4287
Laser
profilometry
[25–27]
The elevation (distance from the laser beam source)
of each sampling point is calculated on the basis of
the laser beam transit time; morphological parame-
ters are computed for selected profiles in accordance
with E N ISO 4287
Opto-morphometry
technique
[28–30]
The observation and analysis of the shadow produced
by the superficial roughness of the surface (Moir´es
fringe pattern principle); morphological parameters
are computed for selected profiles in accordance with
EN ISO 4287
Microscopic
metod
[29-32]
The profile parameters are determined with vertical
sectioning methods for the profile images registered
with a light microscope at given magnification
Bull. Pol. Ac.: Tech. 61(1) 2013 75

A. Garbacz, L. Courard, and B. Bissonnette
Fig. 3. Scale effect on profile decomposition after Ref. 22
from surface analysis is the bearing ratio (Fig. 4a), defined as
the percentage of profile intercepted by a reference line with
a given length. If the bearing ratio is determined on the total
height of the profile in a number of interception planes as large
as possible, and represented on a graph, the Abbott’s cu rve is
obtained (Fig. 4b). The shape of Abbott’s curve is character-
ized by three parameters: relative height of the peaks (C
r
),
depth of the profile (C
f
), excluding high peaks and holes, and
relative depth of the holes (C
l
).
Fig. 4. Illustration of the Abbots curve parameters after Ref. 9
Table 4
The vertical and horizontal amplitude parameters most often used for
characterization of surface profile acc. to EN ISO 4287 (X = P, W, R for
total, waviness and roughness profiles, respectively)
Symbol Parameter Definition
m
x
mean value and line line whose height (mean val-
ue) is determined by minimal
sum s quare deviation of the pro-
file defined as follows: X =
min
P
y
2
(x)
X
p
max peak height distance between the highest
point of the profile and the mean
line
X
v
max valley depth distance between the lowest point
of the profile and the mean line
X
t
max height maximum distance between the
lowest and the highest point of
the profile and it is equal X
t
=
max (X
p
+ X
v
)
X
a
X
a
arithmetic mean devi-
ation
mean departure of the
profile from the refer-
ence mean line as follows:
X
a
=
1
l
l
Z
0
|y(x)| dx, approxi-
mated by X
a
1
n
n
P
i=1
|y
i
|
S
m
mean period
of profile roughness
mean value of mean line includ-
ing consecutively a peak and a
valley S
mi
, as follows: S
m
=
1
n
n
P
i=1
S
mi
3.3. Mechanical and laser profilometry. The surfaces of
C20/25 concrete slabs were submitted to several surface
treatments and evaluated with mechanical (ULg ) and laser
(WUT) pr ofilometers [33, 34]. The following types o f me-
chanical tr e atments were used to prepare the concre te test
slabs: grinding (GR), sandblasting (SB), shotblasting (SHB35
and SHB45, with treatment time of 35 and 45 s, respective-
ly), hand milling (HMIL) and mechanical (MMIL) milling.
76 Bull. Pol. Ac.: Tech. 61(1) 2013

A surface engineering approach applicable to concrete repair engineering
Test slabs without treatment were u sed as a reference. Sur-
face roughness was characterized with the Sand Patch Test
and mechanical profilome try using specimens that were saw
cut from the plate (Table 5).
Table 5
Concrete surface geometry parameters determined after surface treatment
with mechanical and laser profilometers (acc. to [34]) (“s” suffix is
corresponding to laser profilometry and “p” is corresponding to mechanical
profilometry)
Method Parameter
Surface treatment
GR SB SH35 SH45 HMIL MMIL
Laser
profilometer
(parameters
related
to surface)
W
ts
[µm] 933 1 130 2 730 3 110 1 300 3 400
W
as
[µm] 134 156 444 515 127 384
W
vs
[µm] 530 571 1 140 1 680 985 2 340
C
RS
[µm] 234 161 509 960 68 341
C
F S
[µm] 404 505 1590 3330 409 1460
C
LS
[µm] 391 218 175 670 340 1112
D
s
[–] 2.400 2.370 2.420 2.360 2.340 2.380
Mechanical
profilometer
(parameters
related
to profile)
W
tp
[µm] 219 1 036 1 086 2 165 473 867
W
ap
[µm] 32 180 215 386 70 179
W
vp
[µm] 108 317 516 1009 269 419
C
RP
[µm] 57 50 289 698 116 188
C
F P
[µm] 55 77 406 619 107 351
C
LP
[µm] 69 144 291 669 196 248
Sand Patch SRI [mm] 0.72 1.40 1.59 1.85 0.79 1.05
The results of surface geometry characterization [33, 34]
obtained with the two methods ca n be summarized as follows:
the geometrical parameter s determined at microscopic level
generally indicate that the highest roughness was obtained
after shotblasting for 45 s, and the lowest rough ness was
obtained by grinding;
the mean microroughness values are close to each other for
the treatment types and the both mechanical and laser pro-
filometry method s (R
ap
= 17±2 µm and R
as
= 19± 7 µm,
respectively). However, the total he ight of the roughness
profile determined with laser profilome try was 2.8 to 5.5
times longer than the one obtained w ith mechanical pro-
filometry with the same filtering pro cess; this indicate s that
roughness parameters cannot be used alon e to a ppraise sur-
face quality after treatment;
both the total height an d the mean value of the waviness
profile measured w ith the laser profilometer are higher
(1.3–4.3 times) than those deduced from the mechanical
method. In the case of the Abbott’s curve parameters, the
ratio even reached a value of 7 times. Nevertheless, values
of these ratios do not correspond to the waviness level.
The statistical analysis of the results revealed a high correla -
tion coefficient (r > 0.94 ) of the relationship between the cor-
respond ing mean values of waviness profile, W
a
(Fig. 5a) as
well as the Abbott’s parameters C
R
and C
F
determined with
laser and mechanical profilometry (Fig. 5b). A higher scat-
ter in the results for both profilometry methods is observed
in the case of other am plitude parameters. Lower statistical
significance (Fig. 5c) is obtained for the total heights of the
wav iness profile (W
ts
vs. W
tp
) and the maximum dep th of
the valleys (W
vs
vs. W
vp
) as well as the relative d epth of
holes, C
L
(see Fig. 5b). This could be caused by the fact that
different surface areas were scanned with the laser and the
mechanical pro filometer. However, Figs. 5b a nd 5c indicate
that the low co rrelation is due to the low values of ampli-
tude parameters obtained with mechanical profilometry for
the surface after mechanical milling. This surface has h igh ir-
regularities and a sign ifica nt number of deep and wide cracks.
It seems that these cra cks might be more easily detected by
the laser profilometer tha n by the mechanical profilometer
stylus.
a)
b)
c)
Fig. 5. Relationships between waviness parameters: W
a
(a) Abbott’s
(b) and W
t
and W
v
(c) determined with laser and mechanical pro-
filometry; suffixes “p” and “s” for mechanical and laser profilometers
respectively (acc. to Ref. 34)
3.4. Microscopic method. Concrete surface geometry can
be characterized using a scientific approach referred to as
quantitative fracto graphy [35, 36]. Although its use is more
Bull. Pol. Ac.: Tech. 61(1) 2013 77

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References
More filters
Book

Adhesion and adhesives

A. J. Kinloch
Book

Surface Engineering of Metals: Principles, Equipment, Technologies

TL;DR: In this article, the basic definitions of classical and modern surface treatments, addressing mechanisms of formation, microstructure, and properties of surface layers are provided, including wear resistance, anticorrosion, and decorative coatings.
Journal ArticleDOI

Fractals, Fractures, and Size Effects in Concrete

TL;DR: In this article, a weak correlation between fracture properties and the fractal dimensions is reported, as well as the relationship between a fractal analysis and the size effect law, where the fracture surfaces are fractal over the measured range of scales.
Journal ArticleDOI

Characterization of concrete surface roughness and its relation to adhesion in repair systems

TL;DR: In this article, the relationship between surface geometry and adhesion in repair systems is analyzed using four measurement techniques, corresponding to different levels of observation: laser, mechanical profilometry, a microscopic method and a "sand" (macroscopic) method.
Journal ArticleDOI

Effect of concrete surface treatment on adhesion in repair systems

TL;DR: In this paper, different surface treatments (e.g. grinding, sandblasting, shotblasting and hand-and mechanical milling) were performed and the quality of the preparation established on the basis of three main parameters: surface geometry, superficial concrete micro-cracking and adhesion.
Related Papers (5)
Frequently Asked Questions (12)
Q1. What is the important parameter influencing adhesion in repair system?

Superficial cracking, often referred to as “bruising”, is considered as one of the most important parameters influencing adhesion in repair system. 

The objective of the paper is to analyze the effect of substrate roughness and superficial microcraking upon adhesion of repair systems using concrete surface engineering approach. The results presented in this paper have been obtained within the framework of research projects performed to develop a better understanding of the factors affecting the adhesion of repair materials through a surface engineering approach. Based on the results of investigations, the authors showed that the durability and quality of concrete repairs depend to a large degree on the characteristics of the substrate. Mechanical preparation and profiling of the concrete surface to be repaired has to be balanced with potential co-lateral effects such as superficial cracking, too often induced as a result of inappropriate concrete removal method selection, and the loss of benefits due to better mechanical anchorage. 

The optical device used in this study could reach a resolution of 200 µm in Z dimension, for a scanning surface area of 350 × 350 mm. 

Among the contact methods there are mechanical profilometers (extensometer-mounted), tactile tests, kinetic friction measuring device, static friction measurement, rolling-ball measurements, and measurement of the compliance of a metal sphere with a rough surface. 

Three types of surface preparation techniques were investigated: scarifying, high pressure water jetting (1240 bar pressure and 23 l/h water flow) and polishing (obtained with two abrasive and rotative wearing plates). 

The operating principle of the method is based on the comparison between two images having different Moiré’s patterns: the first serves as the reference (image of the pattern with nondeformed parallel fringes), while the second is the projectedpattern deformed in accordance with the surface profile. 

The following types of mechanical treatments were used to prepare the concrete test slabs: grinding (GR), sandblasting (SB), shotblasting (SHB35 and SHB45, with treatment time of 35 and 45 s, respectively), hand milling (HMIL) and mechanical (MMIL) milling.76 Bull. 

The values of fractal dimension, Db determined with the microscopic method were highest for grinding and sandblasting and in general close to values for typical for concrete surfaces: D = 1.03–1.25 [30, 37–40]. 

The investigations reported in the recent years, have shown that the durability and quality of concrete repairs depend to a large degree on the characteristics of the substrate. 

In addition to the profile parameters determined in accordance with EN ISO 4287, the three following stereological parameters could be considered for characterization of concrete profiles after surface treatment [33, 34]:• profile (linear) roughness ratio, RL = L/LO: length of the profile line, L, divided by the projected length of the profile line, LO; • surface roughness ratio, RS = S/SO: true fracture surface area, S, divided by the apparent projected area, SO; • fractal dimension, D: a measure of the self-similarity of rough objects. 

On the basis of the results obtained the following conclusions could be drawn:a) the use of such mechanical technique to evaluate the pro-files of concrete has some important limitations:– stylus (extensometer tip): because of the lenght of thestylus, it is impossible to make measurements on very rough surfaces eg. prepared by hydro-jetting;– air bubbles: some of the entrapped air voids in con-crete are so large that the stylus gets stuck into it and the automatic measuring procedure is suddenly interrupted; the selection of the zone to be mapped is very important;– dimensions: accurate evaluation of roughness para-meters is quite time-consuming and it is the reason why the surface of investigation is limited; moreover, this system is not usable on site.b) with regards to optical profilometry techniques, it can bestated that:– vertical resolution: with the device used in the studyreported by Perez et al., it was impossible to evaluate micro-roughness and waviness; nevertheless, recent developments enable to characterize roughness down to that level;– air bubbles: future version of algorithm, based on im-age analysis, will be able to remove air or water bubble in order to obtain real roughness;– this method presents a lot of practical advantages. 

The relationship between RS and RL for concrete substrates after various treatments can be described by the equation: RS ≈ 1.46RL−0.42, with a high correlation coefficient (r > 0.998).