method for determining the parameters of surface
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to find the surface roughness of the substrateTRANSCRIPT
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Method for determining the parameters of surfaceroughness by usage of a 3D scanner
M. Siewczynska
Poznan University of Technology, Piotrowo 5, 61-138 Poznan, Poland
a r t i c l e i n f o
Available online 23 March 2012
Keywords:
Surface roughness
3D scanner
Sandblasted concrete surface
RS
RL
nt matter & 2012 Politec.1016/j.acme.2012.03.007
Monika.Siewczynska@Pu
a b s t r a c t
Appropriate methods and parameters best describing the surface roughness are searched for.
Concrete is a heterogeneous material and various types of damage and surface cleaning cause
an increase of the roughness. Surface roughness depends i.a. on the quality and method of
cleaning used. Mapping the shape of the profile is usually performed using profilografs.
Description of surface roughness is usually expressed via standards parameters or fractografic
parameters that must be determined using the cycloid grid imposed on selected images of
surface profiles. This method is approximate. Described in this article is a new method for
measuring shapes which can be applied for any area (not just concrete), and most importantly,
gives information about the roughness of the entire surface in an accurate manner. The
calculations are made directly from geometric measurements of the whole surface, and not
based on averaging the results of the selected profiles. The method uses a 3D scanner and CAD
capabilities available in research centers or freeware programs.
& 2012 Politechnika Wrocławska. Published by Elsevier Urban & Partner Sp. z.o.o. All rights
reserved.
1. Introduction
Due to the increasing aggressiveness of the environment which
causes ageing of concrete and reinforced concrete—repair and
protection of these structures are more often needed. In order to
repair the surface, adhesion to the ground is most important and
the relationship between surface degree of development and
coating adhesion must be determined and so appropriate
methods for determining parameters of surface roughness are
searched for. Concrete is a heterogeneous material and various
types of damage or cleaning of its surface (before the application
of the repair materials) increase roughness [1,2]. Surface rough-
ness depends i.a. on the concrete grade and method of cleaning.
2. Concrete surface roughness
Roughness is a characteristic of the surface that identifies its
inequality (elevations and depressions) which is nothing less
hnika Wrocławska. Publis
t.Poznan.Pl
than the order of magnitude smaller than the size of the
element. There are two ways to describe the topography of
the surface: profile (flat—2D) and surface (spatial—3D) [3].
Mapping the shape of the profile is usually performed using
profilografs (mechanical or laser). Among the surface methods
used one can distinguish sand testing (quickest but approximate
which works only on horizontal surfaces) or analyzing the
surface topography of the spatial image, which is done in the
form of contour maps, gray or multicolor maps, isometric (3D)
performed by comparing the consecutive profile images.
Description of surface roughness is usually expressed through:
–
hed
standard parameters [4] designed for metal surfaces or
–
fractografic parameters, calculated on data obtained fromsurfaces geometrical measurements of selected profiles [5].
Profile images are usually created by touch method (profilograf)
or by laser light which yields the roughness of the test profile. By
analyzing profile measurements an estimation of the roughness
by Elsevier Urban & Partner Sp. z.o.o. All rights reserved.
a r c h i v e s o f c i v i l a n d m e c h a n i c a l e n g i n e e r i n g 1 2 ( 2 0 1 2 ) 8 3 – 8 984
parameter, describing the entire surface is made. Furthermore
calculations of the surface roughness values (standards para-
meters) taken from the standards on metal surfaces are not
relevant to the concrete surfaces and have restrictions of use
[6,7]. Values of fractografic parameters are usually determined by
using a cycloid grid imposed on selected images of surface
profiles [8]. However this method is approximate and implies
that concrete surfaces can have fractal characteristics. Because of
this, determination of surface roughness by fractal theory is
burdened by three kinds of errors. The first approximation lies in
mapping of surface profiles, as any method e.g. mechanical or
laser profilometer is related to the accuracy of this device. The
second approximation results from methods of determining
factors to develop a profile of RL and RS to the surface of randomly
selected profiles. Third approximation stems from the applica-
tion of fractal theory to the concrete surface, for which the fractal
dimension D, according to information available, is located in
between 2 and 3. To qualify as a fractal shape, this value should
be between 1 and 2.
3. New method
The new method of shape measurement described in this article
not only gives accurate information about surface roughness but
also can be applied at surfaces different from concrete. The
calculations are made directly from geometric measurements of
the whole surface and not based on averaged results of selected
profiles. This is a non-invasive method, well suited in the trend of
diagnostic development that focuses on features other than
strength of elements and structures of concrete or reinforced
concrete [9].
During development an assumption was made that the
proposed method must be compatible with freeware pro-
grams or CAD software available in research centers. Further-
more the method would have to work on standard computer
configurations and not require any prior knowledge of
programming just program-specific one.
The new method consist of creating a virtual three-
dimensional image of the test surface by scanning it with a
3D optical scanner (using Moire’s effect of bend fringes)
(Fig. 1). The resulting image is a cloud of points with known
positions (named coordinates x, y, z in the adopted coordinate
system) on which (in a program that supports the scanner)
Fig. 1 – Comparison of images obtain
smallest possible triangles are drawn to create a dimensional
approximation of the scanned surface. This image approx-
imation accuracy is determined by the resolution of the
scanner and in this study it was 20 mm. Additionally separa-
tion of profiles was carried out in two perpendicular direc-
tions (x, z) and (y, z) at an interval of 1 mm.
Three-dimensional, virtual images and separate sections
are then imported into a CAD program. Calculations of
surface area and length are carried out to determine the
coefficients of the surface development:
–
ed
RS parameter Eq.:
RS ¼ S=A0 ð1Þ
where S is the specific surface area, and A0 is the area of
the orthogonal projection on the plane,
–
RL parameter Eq.:RL ¼ L=L0 ð2Þ
where L is the length of the profile line, and L0 the length of
projection line profiling on a plane.
During method development the only measurement error
made was due to accuracy of the 3D scanner (0.20 mm); any
additional software was used only to change file formats and to
calculate parameter values needed to coordinate points located
on the analyzed surface and obtained during the scan. A detailed
statistical analysis was performed [6] during which an average
error of parameter RS was recorded at 8% of the parameter value
and RL at 10% of the parameter value. All the measurements
discussed in this study were carried out by a scanner of 1,400,000
dots points of measurement (ATOS II) but now, more sophisti-
cated equipment is available including scanners with over
4,000,000 points of measurement (ATOS SO 4M) [10,11]. Never-
theless the accuracy of the scanner used was assessed as
satisfactory due to the expected values but usage of scanners
with higher resolution would give a lower value of measurement
error resulting from the calculation of parameters.
4. Parameter calculation schedule
The result of a three-dimensional surface scan is a spatial
image, consisting of triangles with known coordinates of the
by 3D scanning with real ones.
a r c h i v e s o f c i v i l a n d m e c h a n i c a l e n g i n e e r i n g 1 2 ( 2 0 1 2 ) 8 3 – 8 9 85
vertices. For each surface file a �.stl export was created with
3D scanning software. Furthermore a set of coordinates can
be exported into a n.txt file. This data set contains consecutive
coordinates of points separated by space, for example:
2:088029 �32:265826 0:294061
23:653204 �59:483296 0:036868
19:770278 �18:440480 0:258670
2:277080 �31:906161 0:310550
One can also extract cross sections in a given distance from
each other, then the text file with the coordinates looks as
Fig. 2 – 3D view (Blender) of a sand
Fig. 3 – 3D view (Blender) of not sandblasted concrete surface
imperfections.
follows:
4:594258 0:013154 0:013154
4:697288 �66:000000 0:024115
4:893628 �66:000000 0:015943
4:973358 �66:000000 0:011526
The files were then imported into Blender, a freeware 3D
editing program, which allowed for editing of the images
spatial surface (Fig. 2). To ensure a more faithful representa-
tion of the concrete, a small area, located at the edges of the
cubes, was removed along with the markers stuck to stabilize
blasted concrete surface C8/10.
C12/15, doubling and flattening of the image, removal of
a r c h i v e s o f c i v i l a n d m e c h a n i c a l e n g i n e e r i n g 1 2 ( 2 0 1 2 ) 8 3 – 8 986
the image during the scan. Each surface was doubled and
flattened (Fig. 3) and then the spartial forms where exported
to a n.dxf file which is supported by CAD software (Figs. 4
and 5). Additionally, a program written in AutoLISP [12] was
used to calculate the area of all triangles. The specific surface
area and area of the orthogonal projection on the plane was
calculated for the whole surface of the scanned sample.
Moreover the calculation of the coefficient of the surface of
developing RS was performed.
In order to calculate the coefficient of the line profile—the
RL parameter in the editing program 3D rectangles perpendi-
cular to the plane of the mean were added. The lines of
Fig. 4 – 3D view (CAD) of not sandblasted concrete surfac
Fig. 5 – 3D view (CAD) of a sandblasted concrete surfac
Fig. 6 – 3D view (Blender) of selected profiles of not sandblasted
direction.
intersection of the planes profile were identified. Due to the
inability to import the CAD set of points and lines of zero
thickness profiling was performed to extend the line in a
perpendicular direction (Fig. 6), and then was made the export
to n.dxf format. Next the import of files n.dxf to CAD (Fig. 7)
program was done. The unnecessary points profile banner
stretched before were removed. In order to count the length of
all sections making up the surface profile a script written in
AutoLISP was used, which counts a total length of all selected
lines. The horizontal distance between the beginning and the
end of the profile was measured. Performed the calculation
factor to develop a profile RL.
e in C12/15 as a grid of triangles (a) and rendering (b).
e C8/10 as a grid of triangles (a) and rendering (b).
concrete surface C12/15, line extension in a perpendicular
a r c h i v e s o f c i v i l a n d m e c h a n i c a l e n g i n e e r i n g 1 2 ( 2 0 1 2 ) 8 3 – 8 9 87
5. Scope of research
Measurements of five different concrete surface classes
(before and after sandblasting) were performed using a 3D
scanner, after which the surface area and the profile
development rates (fractografic parameters) were calculated.
Measurement of surface shapes were made by a non-invasive
method in accordance with increased interest in these
studies which involve characteristics of construction materi-
als. Sample images of the surface are shown in Fig. 8.
Fig. 9 – Graph RS(fcm) for sandblasted (s) and not sandblasted
(n) surface.
6. Test results
Calculated values for RS and RL parameters are presented in
graphical form (Figs. 9 and 10). A trend of reducing the values
of RS and RL for sandblasted surface with increase of the
compressive strength of concrete was observed. The course of
the regression line falls within the error range of all points
and the points are located in the 95% confidence level. When
it comes to not sandblasted surfaces changes in the value of
the roughness parameters when changing the class of
concrete were not observed.
7. Test results analysis
Coefficients of surface and profile development are easy to fix
by the proposed method, and the RS parameter gives
information about the entire surface. Selected advantages
and disadvantages for the new method of calculating the
parameters RS, RL are discussed:
–
Fig
sur
Fig
Attention must be paid during the 3D surface scan, a beam
of light must reach the large cavities, otherwise there will
. 7 – 2D selected profile view (CAD) of sandblasted concrete
face C8/10.
. 8 – Exemplary view of scanned surfaces: concrete C12/15, not san
Fig
san
be a gap in the image area. The presence of such gaps will
not affect the methodology for determining the para-
meters, but their value can be reduced due to omission of
surface by a large cavity.
dblasted surface (a), concrete C8/10, sandblasted surface (b).
. 10 – Graph RL(fcm) for sandblasted (s) and not
dblasted (n) surface.
a r c h i v e s o f c i v i l a n d m e c h a n i c a l e n g i n e e r i n g 1 2 ( 2 0 1 2 ) 8 3 – 8 988
–
Fig
sa
In order to determine the fractografic parameters, knowl-
edge of complex norm methods to determine roughness is
not needed. One only needs basic competence with
software discussed in this study.
–
Calculation time is very short.–
At any stage of determining the parameters, there is noneed to reduce the accuracy of calculations. None of the
programs reduce the accuracy and there is no danger in
confusion of reading by the person who carries out the
calculation.
–
Fig. 12 – Graph RS(RL) for different types of concrete, tests
conducted: 1—own research, 2—Czarnecki, 3—Coster,
Chermant, 4—Underwood, 5—Konkol, Prokopski (basalt
concrete), 6—Konkol, Prokopski (gravel concrete), 7—Wright,
Karlsson, 8—Gokhale, Uderwood.
Parameter values are the characteristics of the entire surface
with such accuracy as the 3D scanner. If necessary, one can
obtain information on the passage surface which, in the short
term performance, is not a labor-intensive calculation.
Developed method of calculating the parameters RS and RL
gives results without loss of measurement accuracy. Calcula-
tion of these values in accordance with the commonly used
theory of fractals is always approximate and depends on the
image magnification and the length of the selection step.
The relationship between RS and RL for the tested concrete
(Fig. 11) has a high correlation coefficient. For the sandblasted
surfaces it is r¼0.89, and for not sandblasted r¼0.83. The
regression lines have the form:
–
.
n
for sandblasted surface Eq.:
RS ¼ 131 � RL2029 ð3Þ
–
for not sandblasted surface Eq.:RS ¼ 031 � RL þ 070 ð4Þ
The relationship RS(RL) for the sandblasted surface can be
compared with results of other tests conducted on concrete
breakthroughs. Fig. 12 presents a comparison of results obtained
according to the described studies done by Czarnecki, Costera,
Chermant, Underwood, Konkol and Prokopski, Wright and
Karlsson and Gokhale and Uderwood [8].
11 – Graph RS(RL) for sandblasted surfaces (p) and not
dblasted (n) obtained in the analysis of research.
The dependence discovered in this study falls within the
limits of Underwood, and Konkol and Prokopski and is almost
parallel to the line designated by Underwood and Czarnecki.
The regression line is consistent with the general trend for
various concretes. Moreover the change in the angle of
inclination is associated with different ways of preparing
concrete surfaces prior to the examination and their compo-
sition. In this research, areas have been sandblasted and
other studies have analyzed the surface concrete break-
throughs of different compositions.
8. Results
Analysis of tests carried out conclude that there is a
correlation between the strength of concrete under-surface
detachment and surface roughness subjected to sandblasting.
The higher the grade of concrete, the smaller the roughness
of sandblasted surfaces. For not sandblasted surfaces
roughness parameters are unaffected by varying grade of
concrete.
Coefficients of the surface and the profile development
reflect the nature of the surface roughness of concrete, this is
seen particularly with the parameter RS (spatial description).
Furthermore the value of using computer software can be
determined as the proposed method is much easier and it is
faster to obtain the results which are more accurate. Mean-
while, the proposed method of calculation using available
software, provides extra capabilities for process control and
analysis of surface roughness. It also gives a tool that can be
modified depending on need of analysis or the result sought.
Currently used values for determining surface roughness by
fractal theory are burdened with three kinds of errors. The new
method is developed only for measurement errors resulting from
the accuracy of the 3D scanner (in this study it was 0.20 mm).
However, further calculations of parameter values are carried out
without loss of accuracy. Additional software was present only to
change file formats and to calculate parameter values used to
coordinate points located on the analyzed surface and obtained
a r c h i v e s o f c i v i l a n d m e c h a n i c a l e n g i n e e r i n g 1 2 ( 2 0 1 2 ) 8 3 – 8 9 89
during the scan. This method does not require any prior
knowledge of programming just program-specific one. Measure-
ment of the reported studies were performed with a resolution of
the scanner of 1,400,000 dots/in., and scanners are now available
with a resolution of 4,000,000 dots/in. The described method can
be further simplified by preparing a computer program that will
calculate the parameters RL and RS directly from text files.
The new method of shape measurement described in this
article not only gives accurate information about surface rough-
ness but also can be applied at surfaces different from concrete.
This is a non-invasive method, well suited in the trend of
diagnostic development that focuses on features other than
strength of elements and structures of concrete or reinforced
concrete.
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[7] M. Siewczynska, New method of calculation of surfaceroughness parameters, in: M. Kaminski, J. Jasiczak, W.Buczkowski, T. Błaszczynski (Eds.), Modern Repair Methodsin Building and Constructions, Dolnoslaskie WydawnictwoEdukacyjne, Wrocław, 2009, pp. 77–86.
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