Arsalaan Thesis Paper

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3rd World Conference on Applied Sciences,

Engineering and Technology

27-29 September 2!"

The application of imaging technique to study

segregation and aggregate orientation in cement concrete

ARSALAAN K HAN1, RAWID K HAN2

#ac$lty member, %epartment of Ci&il Engineering, 'ni&ersity of Engineering ( Technology )esha*ar )a+istan

Email !engrarsalaan.gmailcom, 2ra*id/0.gmailcom

Abstract: Segregation and orientation of aggregate affects the performance of cement concrete. Image analysistechnique was applied to study orientation and segregation of aggregates in hardened concrete. Samples prepared from 1½ inch and 1 inch down aggregate both in laboratory and in situ were scanned for images.Samples with steel bars were also scanned to understand the effect of reinforcement. From image analysis of thedata, it was found that the value of segregation is not similar for laboratory, and site prepared samples. Thevalues are varying through the height of the samples and there is high segregation near the edges compared to

the midpoint of sample.

Keywords: 1mage analysis, 1mage, threshold, segregation, regional orientation

1 Introduction & Literature Review

The orientation and distribution of aggregates have asignificant effect on the performance of concretemitures. The internal structure of asphalt concrete pavements plays a vital role in its resistance todistress, which include rutting and crac!ing due to

fatigue, low temperature and thermal changes "#.$asad %. $., 1&&&'.(ifferent mechanical properties of asphalt andconcrete mitures are obtained with specimenshaving the same air voids content and mi design.This difference is due to aggregate orientation and

segregation as function of particle si)e and shape, position in the sample, and mode of compaction, thathave significant influence on asphalt miture performance "*listair #. +unter, --'. The methodof compaction has a direct impact on the aggregateorientation and internal structure of an asphalt

miture "*.#. +unter, --'. The quantification of the aggregate matri of an asphalt miture specimenis an important and difficult tas! because of itscomposite structure and three/dimensional form. Theasphalt matri is a composite of three phases0 air,mastic and aggregate, each of which may be

described by their distribution, shape properties andsegregation within any given specimen "*listair #.+unter, --'. Image analysis has made it possible toquantitatively define and study the aggregate matriand asphalt and concrete specimens. (ifferent image

processing procedures can be applied to distinguishthe aggregate particles from the bac!ground for image analysis. ircumferential particle orientationoccurs mostly in gyratory and vibratory compactedspecimens, and to a lesser etent in slab, compactedspecimens "*listair #. +unter, --'. $astic is a

combination of asphalt binder and fines, which are particles passing sieve 2 -- "i.e. si)es finer than 34microns'. The proportions, distribution, andinteractions of these three phases define the micromechanical behavior of asphalt concrete pavements"+.$. 5elelew, --6'.

7ecent studies show that the microstructure of asphalt mitures can be quantified using imageanalysis techniques. This approach allows theaggregate structure to be accurately and non/destructively visuali)ed at the microstructure level.

8ast wor! shows that the gradation curves obtainedafter image analysis on different specimenscompacted via different methods give almost sameresults as coarse particles are mostly concentrated atthe bottom compared to the top of the specimen, theoverall average orientation angles for the whole

specimen is around 4-, showing random orientationin the specimens, and the aggregates in the outer section of the specimen tend to form circumferentialalignment whereas randomly aligned in the inner section "9orhidayah , -1'.The ob:ective of this research is to develop, and

apply the image analysis technique for studying thesegregation and orientation of coarse aggregates incement concrete in laboratory and in situ, and withand without reinforcement.

! "ethodology

The methodology consists of eperimental wor! involving preparation of samples and thedevelopment of the image analysis program inImage; software.

2.1 Mix design and aggregate gradation

*ll the coarse and fine aggregates used in the

preparation of concrete samples were used after ma!ing sure they follow *ST$ << requirements for si)e and gradation "Figure 1, '.

opyright = -1 %*S+* 7#S#*7+ #9T7#. *ll rights reserved



*7S*>**9 ?+*9, 7*@I( ?+*9

#ig$re ! radation c$r&e for !45 lab samples

6coarse aggregate

#ig$re 2 radation c$r&e for !45 and !8 lab

samples 6fine aggregate

2.2 Preparation of lab and field representative

concreteSample of 1 ½ inch and 1 inch down aggregate were prepared in laboratory. *dditionally, samples withreinforcement bars were also prepared to study theeffect of reinforcement on aggregate segregation and

orientation "Figure <. '.>aboratory concrete samples in controlledenvironment were prepared <--- psi. $i design and proportioning was done using *bsolute Aolumemethod of the *I code. Two cylinders out of fivefor each concrete type were tested for crushing

strength via universal testing machine whereas therests were cut at bottom, middle and top levels for

acquiring the images.

#ig$re 3 ab representati&e samples

Field representative concrete was prepared followingthe same mi design ratio for 1½B and 1B downconcrete, used for lab prepared samples. This was

done to study the effect of cylinderCs wall onhardened concrete properties.

#ig$re " !25 deep field concrete slabs, !48 do*n on

right and !8 do*n on left

Two slabs of 1 ½ inch and 1 inch down concrete were prepared. These slabs were 4B long, 1B wide and1B deep. The length and depth were decided so that

to etract five cores from each slab, and its depth wasdecided to be as of laboratory cylinder samples, for depth/wise similarity.

2.3 Preparation of reinforced concrete samples

*s the effect of reinforcement on aggregatesC

orientation and segregation was the desired ob:ectivethis study, concrete samples having steel bars were prepared for the purpose and then to cut along thecross/section at the required levels. * problem facedin preparing these samples was that the samplescould not be cut along the cross section with the

available cutter that was only capable of cutting

concrete, and not the steel bars. This was resolved byusing straight rubber pipes of the same outer diameter as of the steel bars. These pipes were !ept straightduring pouring of concrete in the cylinder byinserting a straight steel rod in the rubber pipes that

were removed from the pipes after the concrete hadgot hardened. * total of three 9o "1D inch' si)esteel bars were placed with plastic pipes in cylinder

2.4 Cores extraction ! "ield representative

samples

Two cores out of the five etracted cores "Figure 4'were tested for compressive strength.

#ig$re : Cores; e<traction from slabs in progress

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2.# C$tting process of samples

The locations of cutting were mar!ed on the samplesonce they were ready. The samples were cut at ½B

from the bottom and top level, and also at the mid/level, so as to acquire images at these locations for further study. The top and bottom covers were

important to be removed so that the aggregate particles become visible for image acquisition.8roviding proper nomenclature to the samples was

very important because it becomes impossible todistinguish once the sample is cut. Similarly, itcannot be identified whether the surface is the upper,middle or lower one unless not mentioned on thesamples before cutting.

#ig$re 0 =ie* of reinforced cylinders and field core

samples after being c$t at re>$ired le&els

2.% &mages ac'$isition process

*fter the process of cutting all samples at requiredlevels, images were then acquired with flatbedscanner.

#ig$re 7 1mage ac>$ired sho*ing air &oids, mastic

and aggregate

2.( )ata ac'$isition * &mage analysis

( images were processed to study the effect of concrete preparation in controlled and uncontrolled

environments on aggregatesC orientation andsegregation.Image analysis was performed on these images with

Image ; the image analysis software "*bramoff,--'. *nalyses was done based on piels anddegrees of the input image. For eample, the area,

perimeters, etc. are calculated in units of square piels, and feret angle, etc. in decimal degrees. Thesoftware was also used to crop the images acquired

so that the concrete cross sections could bemagnified, for further analysis. Figure 3 shows asample output image generated by Image;. The

aggregates are labeled, and the data is eported tospreadsheet. $acro was developed in Image; thatwas run on each image loaded in the software. This

macro applied the necessary filters and converts theimage into binary image and then detects the boundary of all aggregates and then labels them andcalculates the required data and displays inspreadsheet for further manipulation.

2.+ Concrete samples wit, reinforcements

Three steel bars were used in each cylinder sample inthe vertical direction. The images acquired of thesesamples were enhanced such that a blac!/colored

circle was mar!ed on the reinforcement, as shown inFigure 6. The actual image of the steel bar is also

shown. *fter ma!ing the necessary enhancement,these images were further analy)ed in Image;, thereinforcement bars were also detected as aggregatesin the analysis. The reinforcementHs I( is theidentification number of boundary of reinforcementin concrete cross section. These I(s were deleted

from the obtained set of data of aggregate boundariesas it is not representing the aggregate. This data wasdeleted from the data set of the rest of aggregates, sothat the effect of reinforcement on the aggregatesavailable in the sample at a specific level could be

studied.

#ig$re / Selection process of the steel bar in the

cross-sectional image #irst 6?s is the act$al

image, *ith steel bar co&ered *ith plastic pipe, 6@?s

is *ith bars filled *ith blac+ color

# Results

From the image analysis the segregation andorientation values were determined for the varioustypes of mied used in this study.

3.1 Perip,eral segregation

The peripheral segregation is the sector/wise percentdistribution of aggregates. The and G coordinatesof each aggregate in the image are ta!en withreference to center of the cross/section "( image' of concrete cylinder. These coordinates are used to

measure the angle subtended by the aggregateCscentroid from -J line. The cross/section is divided

into <K sectors each of 1-J. The number of aggregates lying in each sector are counted andshown on radar plot, in which the sector/wise

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distribution of aggregates at bottom, middle and toplevels could be compared. $aimum value of peripheral segregation is the largest number of

aggregates in any sector of a fied area of cross/sectional image. This value was found KL at bottom,6L at middle and 3L at top. In comparison to this,

the values for 1B down concrete samples were foundas 3L, 4L and KL. In case of 1½B down slabconcrete cores, the maimum values of peripheral

segregation in the bottom, middle and top levels are&L, KL and 4L.For slab concrete of 1B down aggregate at site, thevalues obtained are 4L, KL and 4L. The values incase of 1B down reinforced concrete are 4L, KL and4L.

3.2 -egional segregation

The regional segregation results divide the crosssection in inner and outer regions. The hypotenusal

distance from the centroid of cross/section ismeasured from the coordinates for the centroid of

each aggregate. *ggregates are said to lie in inner region if this distance is less than half of the cross/sectional radius, and vice versa. 7esults obtained for 1½B down laboratory concrete sample one bottom,middle and top )ones were that L, &L and Laggregates lie in the inside region of the sample. The

mean for 1½B down lab samples was found as KLaggregates lying in the inside region of samples.The values for 1B down concrete controlled specimensample 1 were 6L, <L and KL, ma!ing theaverage as &L.

For cores from slab prepared at site, the inner regionsegregation values for 1½B down concrete slab corespecimen 1 were 1<L, KL and <&L.For 1B down field cores from slab, the valuesobtained for first sample are 16L, L and <1L.The regional segregation difference in 1½B down and1B down samples is negligible "1L' in case of

uncontrolled samples, the same was the resultobtained in case of controlled samples.The values of inner side regional segregation of 1½Bdown lab reinforced are 1L, L and -L. Thevalues for 1B down reinforced are 4L, L and6L.

IN OUT0

20

40

60

80

100

30

70

26

74

21

79

Bottom Middle Top

#ig$re 9 @egional segregation res$lts for !5 do*n

lab samples

IN OUT0

10

2030

40

50

60

70

80

90

18

82

22

78

31

69

Bottom Middle Top

#ig$re ! @egional segregation res$lts for !5 do*n

field samples

3.3 /0 orientation

The AS* orientation is calculated by ma!ing groupsof ranges of visible surface area of all aggregates in

each image and then finding the weighted orientationangle for that area group. Since the aggregate area

calculations performed in this pro:ect are in units of square piels, therefore the minimum and maimumlimits for each group are from - to <4,--- for firstgroup, from <4,--1 to 3-,--- for the second group,from 3-,--1 to 1-4,--- for third group and from1-4,--1 to 1-,--- square piels for fourth group

respectively. @eighted orientation angle is calculatedfor all of these four groups by finding out thesummation of aggregates area lying in each group,then finding out the product of summation of areaand orientation angles of all aggregates for that

group, and then calculating the weighted orientationangle by dividing product of summation of area andorientation angles over summation of area. Theseresults are then plotted, giving slope of linear trendline connecting the four values. This slope shows thetrend of increasing or decreasing orientation anglefrom bottom to top of each sample.

The AS* orientation for different concrete types wascompared. In case of 1½B down lab concrete sample,the average orientation angle in case of bottomaggregates is &J, middle aggregates is 3KJ, and topaggregates is 4-J.For 1B down lab concrete, the orientation comes are

KJ, <J and 4J. The orientation in case of 1½Bdown slab cores for bottom, middle and top sampleno. 1 are 4KJ, 6KJ and K&J.For 1B down field cores, the average orientationangles are KJ, 4J and KJ. For the case of usingreinforcement in controlled specimens, the

orientation angle gradients for 1½B down controlledsample at bottom, middle and top are 3&J, 4&J and3-J respectively. The orientation angle for 1B downcore field sample are 3&J, K6J and 33J.

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020406080

100

Bottom Linear (Bottom

Middle Linear (Middle

Top Linear (TopAverage VSA

Weighted Orientation Angle

#ig$re !! =SA orientation res$lts for !45 do*n lab

samples

020

40

60

80

100

120



Top Linear (Top

Average VSA


#ig$re !2 =SA orientation res$lts for !5 do*n lab

samples

!

100"000

200"000

0

20

40

60

80

100

120



Top Linear (Top

Average VSA


#ig$re !3 &erall res$lts of =SA orientation

3.4 -egional orientation

The regional orientation tells how much percent of aggregates tend to form radial or circumferential

orientation. The angle of inclination with respect tothe centroidal origin of the cross/section is calculatedfor every aggregate from its ferret angle, which is theinclination angle of the longest ais of the aggregate.This angle of inclination tells whether the aggregateis radially or circumferentially oriented. *ggregates

are said to be radially oriented if the ferret ais is

parallel to the radius of the cross/section, otherwise,the aggregates will be circumferentially oriented. Theorientation of aggregates will be called as radial if the

angle of inclination is less than 4J, andcircumferential if the angle is greater than 4J. Theaggregates tending to form radial orientation in case

of 1½B down concrete are 4&L at bottom, 4&L atmiddle and 4&L at top.The results achieved for 1B down controlled samples

forming radial orientation are 43L, 4&L and K<L.The regional orientation study is further conducted inuncontrolled field slab core samples. Aalues for

radially aligned aggregates are 36L, K4L, and K<L.

The results obtained for radially oriented aggregatesof 1B down slab core are K1L, K6L and KL.

The effect of reinforcement in lab samples on

regional orientation was studied and was comparedwith those of unreinforced samples. 1½B downreinforced samples radial orientation results are K4L,4<L and K4L. The results for 1B down reinforced lab

are 31L, K4L and KL.

#$%I$L &I#&UM'#NTI$L

0

10

20

30

40

50

60

70 65

35

53

47

65

35

Bottom Middle Top

#ig$re !" @egional orientation res$lts for lab

samples *ith steel bars in !45 do*n concrete

laboratory samples

#$%I$L &I#&UM'#NTI$L0

10

20

30

40

50

60

70 66

34

64

36

60

40

Bottom Middle Top

#ig$re !: @egional orientation res$lts for lab

samples *ith steel bars in !5 do*n concrete

laboratory samples

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Top

Middle

Bottom

#ig$re !0 Typical distrib$tion of aggregate in

concrete 6!4 inch do*n mi< samples at bottom,

middle and top

4 $onclusions From laboratory testing and image analysis, thefollowing are concluded.

• Image analysis technique can reliably be used for

estimating aggregate segregation and orientation.

• 7einforcement in controlled samples affect value

of maimum peripheral segregation in overall

larger si)ed aggregate particles.

• *round 4L aggregates were observed to lie in

inner region in almost all reinforced samples,and samples made with larger si)ed particles

ehibit circumferential orientation and radial

orientation in case of smaller si)ed aggregates.

• *verage orientation angle for 1½B down

concrete was more than that of 1B down in

uncontrolled samples.

• Msing reinforcements in laboratory specimens

ma!e aggregates tend to form circumferentialorientation rather than radial, no matter if larger

or smaller si)ed aggregates are used.• >arger si)ed aggregates get more radially

oriented than smaller si)ed aggregates with theintroduction of reinforcement in concrete.

Ac%nowledgments The authors are duly than!ful to the staff of #arthqua!e #ngineering enter and oncrete>aboratory, Mniversity of #ngineering N Technology8eshawar, for their help in preparing and testing of samples.

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Asphalt )a&ements for So$thern Africa "6'.

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Transportation @esearch Board , 6R14.

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Circ$lar, E-C!0!, pp. /1K.

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Constr$ction and B$ilding Daterials, =ol$me

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O1P8an, T. "--'. #ine Aggregate Characteriation

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Control of Concrete Di<t$res, !3th edition 7etrieved from (epartment of ivil#ngineering0

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Arsalaan Thesis Paper