- Email: [email protected]
Method for determining the parameters of surface roughness by usage of a 3D scanner
archives of civil and mechanical engineering 12 (2012) 83–89
Available online at www.sciencedirect.com
journal homepage: www.elsevier.com/locate/acme
Method for determining the parameters of surface roughness by usage of a 3D scanner M. Siewczyn´ska Poznan University of Technology, Piotrowo 5, 61-138 Poznan, Poland
art i cle info Available online 23 March 2012
ab st rac t Appropriate methods and parameters best describing the surface roughness are searched for.
Keywords:
Concrete is a heterogeneous material and various types of damage and surface cleaning cause
Surface roughness
an increase of the roughness. Surface roughness depends i.a. on the quality and method of
3D scanner
cleaning used. Mapping the shape of the profile is usually performed using profilografs.
Sandblasted concrete surface
Description of surface roughness is usually expressed via standards parameters or fractografic
RS
parameters that must be determined using the cycloid grid imposed on selected images of
RL
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 roughness depends i.a. on the concrete grade and method of cleaning.
2.
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: – standard parameters [4] designed for metal surfaces or – fractografic parameters, calculated on data obtained from surfaces geometrical measurements of selected profiles [5].
Concrete surface roughness
Roughness is a characteristic of the surface that identifies its inequality (elevations and depressions) which is nothing less
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
E-mail address: [email protected] 1644-9665/$ - see front matter & 2012 Politechnika Wrocławska. Published by Elsevier Urban & Partner Sp. z.o.o. All rights reserved. http://dx.doi.org/10.1016/j.acme.2012.03.007
84
archives of civil and mechanical engineering 12 (2012) 83–89
parameter, describing the entire surface is made. Furthermore calculations of the surface roughness values (standards parameters) 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 application 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 programs or CAD software available in research centers. Furthermore 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 threedimensional 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)
smallest possible triangles are drawn to create a dimensional approximation of the scanned surface. This image approximation accuracy is determined by the resolution of the scanner and in this study it was 20 mm. Additionally separation of profiles was carried out in two perpendicular directions (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: – RS parameter Eq.: RS ¼ S=A0
ð1Þ 0
where S is the specific surface area, and A 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 sophisticated equipment is available including scanners with over 4,000,000 points of measurement (ATOS SO 4M) [10,11]. Nevertheless 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
Fig. 1 – Comparison of images obtained by 3D scanning with real ones.
archives of civil and mechanical engineering 12 (2012) 83–89
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:
follows:
2:088029
4:973358 66:000000 0:011526
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
4:594258 0:013154
85
0:013154
4:697288 66:000000 0:024115 4:893628 66:000000 0:015943
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 representation of the concrete, a small area, located at the edges of the cubes, was removed along with the markers stuck to stabilize
Fig. 2 – 3D view (Blender) of a sandblasted concrete surface C8/10.
Fig. 3 – 3D view (Blender) of not sandblasted concrete surface C12/15, doubling and flattening of the image, removal of imperfections.
86
archives of civil and mechanical engineering 12 (2012) 83–89
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 perpendicular to the plane of the mean were added. The lines of
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.
Fig. 4 – 3D view (CAD) of not sandblasted concrete surface in C12/15 as a grid of triangles (a) and rendering (b).
Fig. 5 – 3D view (CAD) of a sandblasted concrete surface C8/10 as a grid of triangles (a) and rendering (b).
Fig. 6 – 3D view (Blender) of selected profiles of not sandblasted concrete surface C12/15, line extension in a perpendicular direction.
archives of civil and mechanical engineering 12 (2012) 83–89
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 materials. Sample images of the surface are shown in Fig. 8.
6.
be a gap in the image area. The presence of such gaps will not affect the methodology for determining the parameters, but their value can be reduced due to omission of surface by a large cavity.
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.
87
Fig. 9 – Graph RS(fcm) for sandblasted (s) and not sandblasted (n) surface.
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: – Attention must be paid during the 3D surface scan, a beam of light must reach the large cavities, otherwise there will
Fig. 7 – 2D selected profile view (CAD) of sandblasted concrete surface C8/10.
Fig. 10 – Graph RL(fcm) for sandblasted (s) and not sandblasted (n) surface.
Fig. 8 – Exemplary view of scanned surfaces: concrete C12/15, not sandblasted surface (a), concrete C8/10, sandblasted surface (b).
88
archives of civil and mechanical engineering 12 (2012) 83–89
– In order to determine the fractografic parameters, knowledge 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 no need 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. – 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. Calculation 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 r¼ 0.89, and for not sandblasted r¼0.83. The regression lines have the form: – for sandblasted surface Eq.: RS ¼ 131 RL 2029
ð3Þ
– for not sandblasted surface Eq.: RS ¼ 031 RL þ 070
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.
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 composition. In this research, areas have been sandblasted and other studies have analyzed the surface concrete breakthroughs of different compositions.
ð4Þ
8. 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].
Fig. 11 – Graph RS(RL) for sandblasted surfaces (p) and not sandblasted (n) obtained in the analysis of research.
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. Meanwhile, 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
archives of civil and mechanical engineering 12 (2012) 83–89
during the scan. This method does not require any prior knowledge of programming just program-specific one. Measurement 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 roughness 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.
r e f e r e n c e s
[1] T. Błaszczyn´ski, J. Jasiczak, B. Ksit, M. Siewczyn´ska, Aspects of bond layer role in concrete repairs, Archives of Civil and Mechanical Engineering 6 (4) (2006) 73–85. [2] Z. Kamaitis, Modelling of corrosion protection for reinforced concrete structures with surface coatings, Journal of Civil Engineering and Management 14 (4) (2008) 241–249 (s.).
89
[3] P. Paczynski, Technical Metrology, Wydawnictwo Politechniki Poznan´skiej, Poznan´, 2003 (in Polish). [4] PN-87/M-04256/02 Geometrical Structure of the Surface, Surface Roughness, General Terminology (in Polish). [5] G. Prokopski, Fracture Mechanics of Concrete Cement, Oficyna Wydawnicza Politechniki Rzeszowskiej, Rzeszo´w, 2007 (in Polish). [6] M. Siewczyn´ska, Influence of selected parameters on the adhesion of concrete coatings, Dissertation, Politechnika Poznan´ska, Poznan´, 2008 (in Polish). [7] M. Siewczyn´ska, New method of calculation of surface roughness parameters, in: M. Kamin´ski, J. Jasiczak, W. Buczkowski, T. Błaszczyn´ski (Eds.), Modern Repair Methods in Building and Constructions, Dolnos´la˛skie Wydawnictwo Edukacyjne, Wrocław, 2009, pp. 77–86. [8] A. Garbacz, Non-Destructive Investigations of Polymer– Concrete Composites with Stress Waves—Repair Efficiency Evaluation, Oficyna Wydawnicza Politechniki Warszawskiej, Warszawa, 2007 (in Polish). [9] J. Hoła, K. Schabowicz, State-of-the-art non-destructive methods for diagnostic testing of building structures— anticipated development trends, Archives of Civil and Mechanical Engineering 10 (3) (2010) 5–18. [10] Materials from webpage: /www.ita-polska.com.plS. [11] Materials from webpage: /www.gom.comS. [12] A. Pikon´, AutoCAD 2002, Helion, Gliwice, 2001 (in Polish).
Available online at www.sciencedirect.com
journal homepage: www.elsevier.com/locate/acme
Method for determining the parameters of surface roughness by usage of a 3D scanner M. Siewczyn´ska Poznan University of Technology, Piotrowo 5, 61-138 Poznan, Poland
art i cle info Available online 23 March 2012
ab st rac t Appropriate methods and parameters best describing the surface roughness are searched for.
Keywords:
Concrete is a heterogeneous material and various types of damage and surface cleaning cause
Surface roughness
an increase of the roughness. Surface roughness depends i.a. on the quality and method of
3D scanner
cleaning used. Mapping the shape of the profile is usually performed using profilografs.
Sandblasted concrete surface
Description of surface roughness is usually expressed via standards parameters or fractografic
RS
parameters that must be determined using the cycloid grid imposed on selected images of
RL
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 roughness depends i.a. on the concrete grade and method of cleaning.
2.
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: – standard parameters [4] designed for metal surfaces or – fractografic parameters, calculated on data obtained from surfaces geometrical measurements of selected profiles [5].
Concrete surface roughness
Roughness is a characteristic of the surface that identifies its inequality (elevations and depressions) which is nothing less
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
E-mail address: [email protected] 1644-9665/$ - see front matter & 2012 Politechnika Wrocławska. Published by Elsevier Urban & Partner Sp. z.o.o. All rights reserved. http://dx.doi.org/10.1016/j.acme.2012.03.007
84
archives of civil and mechanical engineering 12 (2012) 83–89
parameter, describing the entire surface is made. Furthermore calculations of the surface roughness values (standards parameters) 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 application 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 programs or CAD software available in research centers. Furthermore 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 threedimensional 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)
smallest possible triangles are drawn to create a dimensional approximation of the scanned surface. This image approximation accuracy is determined by the resolution of the scanner and in this study it was 20 mm. Additionally separation of profiles was carried out in two perpendicular directions (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: – RS parameter Eq.: RS ¼ S=A0
ð1Þ 0
where S is the specific surface area, and A 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 sophisticated equipment is available including scanners with over 4,000,000 points of measurement (ATOS SO 4M) [10,11]. Nevertheless 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
Fig. 1 – Comparison of images obtained by 3D scanning with real ones.
archives of civil and mechanical engineering 12 (2012) 83–89
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:
follows:
2:088029
4:973358 66:000000 0:011526
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
4:594258 0:013154
85
0:013154
4:697288 66:000000 0:024115 4:893628 66:000000 0:015943
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 representation of the concrete, a small area, located at the edges of the cubes, was removed along with the markers stuck to stabilize
Fig. 2 – 3D view (Blender) of a sandblasted concrete surface C8/10.
Fig. 3 – 3D view (Blender) of not sandblasted concrete surface C12/15, doubling and flattening of the image, removal of imperfections.
86
archives of civil and mechanical engineering 12 (2012) 83–89
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 perpendicular to the plane of the mean were added. The lines of
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.
Fig. 4 – 3D view (CAD) of not sandblasted concrete surface in C12/15 as a grid of triangles (a) and rendering (b).
Fig. 5 – 3D view (CAD) of a sandblasted concrete surface C8/10 as a grid of triangles (a) and rendering (b).
Fig. 6 – 3D view (Blender) of selected profiles of not sandblasted concrete surface C12/15, line extension in a perpendicular direction.
archives of civil and mechanical engineering 12 (2012) 83–89
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 materials. Sample images of the surface are shown in Fig. 8.
6.
be a gap in the image area. The presence of such gaps will not affect the methodology for determining the parameters, but their value can be reduced due to omission of surface by a large cavity.
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.
87
Fig. 9 – Graph RS(fcm) for sandblasted (s) and not sandblasted (n) surface.
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: – Attention must be paid during the 3D surface scan, a beam of light must reach the large cavities, otherwise there will
Fig. 7 – 2D selected profile view (CAD) of sandblasted concrete surface C8/10.
Fig. 10 – Graph RL(fcm) for sandblasted (s) and not sandblasted (n) surface.
Fig. 8 – Exemplary view of scanned surfaces: concrete C12/15, not sandblasted surface (a), concrete C8/10, sandblasted surface (b).
88
archives of civil and mechanical engineering 12 (2012) 83–89
– In order to determine the fractografic parameters, knowledge 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 no need 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. – 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. Calculation 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 r¼ 0.89, and for not sandblasted r¼0.83. The regression lines have the form: – for sandblasted surface Eq.: RS ¼ 131 RL 2029
ð3Þ
– for not sandblasted surface Eq.: RS ¼ 031 RL þ 070
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.
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 composition. In this research, areas have been sandblasted and other studies have analyzed the surface concrete breakthroughs of different compositions.
ð4Þ
8. 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].
Fig. 11 – Graph RS(RL) for sandblasted surfaces (p) and not sandblasted (n) obtained in the analysis of research.
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. Meanwhile, 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
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during the scan. This method does not require any prior knowledge of programming just program-specific one. Measurement 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 roughness 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.
r e f e r e n c e s
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