METHOD OF ASCERTAINING THE HOMOGENEITY OF … · METHOD OF ASCERTAINING THE HOMOGENEITY OF CONCRETE IN CAST-IN-DRILLED-HOLE (CIDH) PILES USING THE GAMMA-GAMMA TEST METHOD CAUTION:

- 1 -

California Test 233STATE OF CALIFORNIA-BUSINESS, TRANSPORTATION AND HOUSING AGENCY November 2005

DEPARTMENT OF TRANSPORTATIONDIVISION OF ENGINEERING SERVICESTransportation Laboratory5900 Folsom Boulevard MS#5Sacramento, California 95819

METHOD OF ASCERTAINING THE HOMOGENEITY OF CONCRETE INCAST-IN-DRILLED-HOLE (CIDH) PILES USING THE GAMMA-GAMMA TEST METHOD

CAUTION: Prior to handling test materials, performing equipment setups, and/or conducting thismethod, testers are required to read “SAFETY AND HEALTH” in Part 6 of this method. It isthe responsibility of the user of this method to consult and use departmental safety and healthpractices and determine the applicability of regulatory limitations before any testing isperformed.

OVERVIEW

This procedure ascertains the homogeneity ofconcrete density for the evaluation of constructionof Cast-In-Drilled-Hole (CIDH) piles. Concreteused in CIDH piles is required to be dense andhomogeneous throughout the length and crosssection of the pile.

This test method is divided into the followingsections:

1. Gamma-Gamma Logging SystemRequirements

2. Instrument Calibrations and FunctionalityLimit Determination

3. Requirements for Inspection TubeConstruction

4. Field Testing Procedures

5. Data Analysis and Reporting

6. Safety and Health

PART 1. GAMMA-GAMMA LOGGINGSYSTEM REQUIREMENTS

A. APPARATUS

1. Gamma-Gamma Probe. The probe shallconsist of a rigid cylinder containing a

gamma particle-emitting source and agamma particle detector. The probe shallbe suspended by a cable of sufficientdesign and length that is safely capable ofraising and lowering the gamma-gammaprobe within a nominal 2-inch polyvinylchloride (PVC) inspection pipe to desiredtest depths.

a) The gamma particle-emitting sourceshall be Cesium-137 in sealed sourceform.

b) The gamma-gamma probe detectorshall consist of a proven method ofgamma detection, such asGeiger-Mueller or scintillation-basedcounters.

2. Readout Device. The detector shall beconnected to a readout device that iscapable of displaying and/or recordingcounts, densities and sampling duration orprobe speed.

3. Cable and Winch. The cables affixed to theprobe shall be of sufficient strength anddurability to raise and lower the probesafely and at a controlled rate of speed.Any winch mechanism utilized shall notdamage the cables or compromise datacollected in the test. A means ofdetermining and recording probe depthshall be provided.

California Test 233November 2005

- 2 -

B. DENSITY PRECISION

1. The gamma-gamma probe shall possess aminimum density precision of 1.0 lb/ft3.Density precision shall be defined as thestandard deviation from the mean valueof gamma count rate at a particularsample time.

2. For gamma-gamma logging, only sampletimes exceeding the minimum required toobtain the density precision of 1.0 lb/ft3shall be used for logging CIDH piles.Probes that are unable to achieve a densityprecision of 1.0 lb/ft3 shall not be utilizedfor gamma-gamma logging.

3. Determination of density precision andminimum sample time shall be inconformance with Appendix A of this testmethod.

C. RADIUS OF DETECTION

1. The radius of detection (Rd) of thegamma-gamma probe shall be a minimumof 3.0-inches but less than 4.5-inches inconcrete with density between 140 and160 lb/ft3 . Radius of Detection shall bedefined as the distance from the center ofthe probe cylinder to the maximumdistance where a change in materialdensity has a discernable affect upon thecollected data.

2. The radius of detection shall bedetermined by means of an InfluenceDetermination Unit according to therequ6irements detailed in Appendix B ofthis test method.

D. QUALIFICATION REPORT

1. Each gamma-gamma probe shall have areport signed and stamped by a CivilEngineer licensed in the State ofCalifornia certifying and providingsupporting documentation of compliancewith the above provisions for gamma-gamma logging system requirements.

PART 2. INSTRUMENT CALIBRATION ANDFUNCTIONALITY LIMITDETERMINATION

A. INSTRUMENT CALIBRATION

1. Prior to use for gamma-gamma loggingand at time intervals not to exceed oneyear, the gamma-gamma probe andreadout device shall be calibrated tocorrelate count rate to concrete density.

2. Calibration parameters shall bedetermined by monitoring count ratesperformed in the concrete calibrationsamples described in Appendix C. Aminimum of three concrete calibrationsamples, as described in Appendix C,shall be utilized for the calibrationprocedure. The following procedure shallbe used:

a) Place the probe in one of thecalibration concrete samples. Verifythat the source is a minimum of6-inches above the bottom of thesample and that the detector is aminimum of 6-inches below the top ofthe sample.

b) With the probe at a constant depth,record a minimum of 50 countreadings within each concretecalibration sample.

c) Calculate the arithmetic mean of thecount readings using the followingequation for each concrete calibrationsample:

nC...C n1 meanC

Where,

C mean = Mean of countsCn = nth countn = total number of counts


- 3 -

d) Compute the natural logarithm of themean count (CMLC) for each of theconcrete calibration samples as shownbelow:

)ln( meanMLC CC

e) Plot the CMLC obtained in Step (c) foreach concrete calibration sample. Plotthe known concrete densities on thex-axis and the corresponding CMLC

values on the y-axis.

f) Using the least squares method,establish the best-fit linearrepresentation to the points plotted inStep (d). This linear fit should take onthe form of:

baCMLC

which may be rewritten as:

abCMLC

where,

= concrete densitya = slope of best-fit lineb = y-intercept of best-fit line

3. Current calibration records shall bedocumented in the form of a graph, withsupporting tabular data, date calibrationwas performed, and equation coefficients.

B. DETERMINATION OF STANDARDREFERENCE FUNCTIONALITY LIMITS

1. Using the standard reference describedand qualified in accordance withAppendix D, the standard referencefunctionality limits shall be determinedat time intervals not to exceed one year.The functionality limits shall also bere-established after any maintenanceoperations are performed on said gamma-gamma probe. Functionality limits shall

be unique for each probe and sourcecombination and shall only be determinedfor those probe and source combinationspreviously qualified in accordance withAppendix D.

2. The procedure for determination offunctionality limits shall not be performedwhere the influence of any otherradioactive source can be detected abovebackground levels.

3. Place the standard reference in thelocation where it will typically be locatedat the beginning of the workday.

4. Place the probe in the standard reference.Ensure that the source is a minimum of4.5-inches from the exterior base of thestandard reference and that the detector isa minimum of 4.5-inches from the top ofthe standard reference.

5. Take a minimum of 200 independentconsecutive readings. Calculate the meangamma count rate and standard deviationof gamma count rate using the followingequations:

Nref , mean Nref ,1 ... N ref ,i

i

1

1

2,,

i

NNi

nmeanrefnref

ref

where,

Nref, mean = mean gamma count rateref = standard deviation of gamma

count ratei = number of independent

consecutive readings

6. Determine Lower Functionality Limit(LFL) and Upper Functionality Limit(UFL) in accordance with the followingequations:


- 4 -

LFL = 0.947 * Nref, mean - 1.95 *ref

UFL = 1.03 * Nref, mean + 1.95 *ref

7. Each standard reference and gamma-gamma probe combination shall have areport signed and stamped by a CivilEngineer licensed in the State of Californiacertifying compliance with the aboveprovisions and documenting the LFL andUFL values.

8. The independent readings from both thevertical and horizontal conditions shall bedocumented in tabular form and retainedfor a minimum of five years.

PART 3. REQUIREMENTS FOR INSPECTIONPIPE CONSTRUCTION

A. INSPECTION PIPES

1. Prior to concrete placement and gamma-gamma testing, CIDH piles shall beprepared with the installation ofinspection pipes to allow for the passageof the gamma-gamma probe.

2. Inspection pipes shall be Schedule 40 PVCpipes with a nominal diameter of 2-inches.PVC couplers are permitted to facilitatepipe lengths in excess of that which iscommercially available.

3. Each inspection pipe shall be securelycapped on bottom and shall havewatertight couplers to provide a clean andunobstructed 2-inches diameter clearopening from 3-feet above the pile cutoffdown to the bottom of the reinforcingcage. If pile cutoff is below the groundsurface or working platform, inspectionpipes shall be extended to 3 feet above theground surface or working platform.Approved covers or railings shall beprovided and inspection pipes shall belocated as necessary to minimize exposureof testing personnel to potential fallinghazards.

4. Inspection pipes shall be placed aroundthe pile inside the outermost spiralor hoop reinforcement at a spacingno greater than 1.5-inches clearof the outermost spiral or hoopreinforcement.

5. Inspection pipes shall be placed aroundthe pile, inside the outermost spiral orhoop reinforcement, and a minimumof 3-inches clear of the verticalreinforcement, at a uniform spacing notexceeding 2-foot 9-inches measured alongthe circle passing through the centers ofthe inspection pipes. A minimum of twoinspection pipes per pile shall be used.When the vertical reinforcement is notbundled and each bar is not more than1-inch in diameter, inspection pipes maybe placed 2-inches clear of the verticalreinforcement.

6. The inspection pipes shall be placed so toprovide the maximum diameter circle thatpasses through the centers of theinspection pipes while maintaining theclear spacing required herein.

7. The inspection pipes shall be installed instraight alignment and securely fastenedin place to prevent displacement ormisalignment during installation of thereinforcement and placement of concretein the hole. The CIDH piles shall beconstructed so that the relative distance ofinspection tubes to steel shall remainconstant.

8. Where the dimensions of the CIDH pile donot permit inspection pipes to be placedadequately to meet the design and testingrequirements, the Engineer experiencedwith gamma-gamma logging may permitinspection pipes to be placed closer thanthe required clearance of Section 3-A-5.Inspection tube placement must be inparallel alignment to the verticalreinforcing steel and maximize distance tovertical steel and proximity to the interiorof the outermost steel reinforcement cagespiral or hoop.


- 5 -

9. Inspection pipes shall be completely dry atthe time of testing, although water may beplaced inside the inspection pipes tofacilitate construction provided it iscompletely purged before testing.

10. In cases where a gamma-gamma probehas been calibrated in concrete calibrationsamples with inspection tubes filled withwater and radius of detection and densityprecision have been performed underwater and determined to be within theprescribed limits, gamma-gamma loggingmay be performed in an inspection tubecompletely filled with water. Testing shallonly be conducted under water at thediscretion of the Engineer experiencedwith gamma-gamma logging. Where priorapproval for testing under water has notbeen given for a particular pile, allgamma-gamma logging shall beconducted in dry inspection pipes.

B. INSPECTION PIPE VERIFICATION ANDREPORTING REQUIREMENTS

1. After placing concrete and beforeperforming the gamma-gamma tests, eachinspection pipe shall be tested by passinga rigid cylinder of the same or greaterdimension and geometry as the gammaprobe through the complete length ofpipe. In addition, all standing waterpresent within the inspection pipe shall beremoved.

2. A log shall be kept to identify the depths,with respect to the plane of pile cutoff, ofany PVC couplers used in the inspectionpipes and provided to the Engineer.

PART 4. FIELD TESTING PROCEDURES

A. FUNCTIONALITY EVALUATION USING THESTANDARD REFERENCE

1. A functionality evaluation shall beperformed at the start of each workday foreach gamma-gamma probe used. Afunctionality evaluation should also be

utilized anytime the performance of thegamma-gamma probe is in question.

2. The functionality evaluation procedureshall not be performed where theinfluence of any other radioactive sourcecan be detected above background levels.

3. Place the probe in the standard reference.Ensure that the source is a minimum of Rd

from the bottom of the standard referenceand that the detector is a minimum of Rd

from the top of the standard reference,where,

Rd = Radius of Detection, asdetermined in Appendix B

4. Take four independent consecutivereadings and calculate the daily meancount rate.

N daily,mean N1 N2 N3 N 4

4

where,

Ndaily,mean = daily mean count rateN1 , N2 , N3 , N4 = individual count rate

readings

Record the four individual count ratereadings (N1, N2, N3, N4) and the dailymean (Ndaily,mean) in the FunctionalityVerification Log form. An example of thisform is included in Appendix E. TheFunctionality Verification Log shall beretained as a permanent record for aminimum of five years.

5. Verify that the daily mean (Ndaily,mean) isgreater than the LFL and less than the UFLas determined in Part 2-B-6. If the abovecondition is not satisfied, the gamma-gamma probe shall not be used to performthe acceptance testing.

6. If the gamma-gamma probe has failed thefunctionality evaluation, the probe shall beserviced by qualified personnel, any


- 6 -

malfunction remedied, and a new LFL andUFL shall be determined in accordancewith Part 2-B prior to the performance offurther acceptance testing.

B. PREPARATION OF THE PILE

1. Verify that the inspection pipes are free ofany standing water, debris or obstructions.

2. Complete the form titled Gamma-GammaTest Set-Up Sheet.

a) Complete the general informationsection at the top of the form.

b) Complete the plan view drawing withthe appropriate number andinspection pipe locations.

c) If the distance between inspectiontubes is not uniform, measure thedistance between each inspection pipepair and record the information in the“Spacing Dist.” column.

d) Using a measuring tape or equivalent,measure the total length of eachinspection pipe and record the lengthsin the “Taped Depth” column. Recordinspection pipe stick up in the “Stick-up” column.

e) If any kinks, obstructions or water arepresent in any of the inspection pipes,enter the appropriate information inthe lower section of the form. Anexample of the Gamma-Gamma TestSet-Up Sheet is included in AppendixE.

4. Inspection pipes shall be marked prior totesting using a permanent marking pen orsuitable permanent marking device withthe support location number, pile numberand tube number. An inspection tube tobe tested may contain the marking:

B3R-P5-T4

which would indicate:

Bent 3 Right, Pile No. 5, Inspection Tube No.

The orientation of the inspection tubenumbering shall be recorded relative tomagnetic North or fixed reference pointsand be recorded on the Setup Sheet.Inspection pipe numbering shall bepreserved until a Cast-In-Drilled Hole pileis accepted.

C. TESTING

1. Lower the probe into the inspection pipe.

2. When extracting the probe, acquirereadings at a depth interval not to exceed1.5-inches at the minimum sampling timeperiod as determined in Part 1-A-1 toobtain the required density precision.Record data on the form titled Gamma-Gamma Test Set-Up Sheet. An example ofthis form is included in the attachments.

3. The tube and the pile top shall be spraypainted with orange paint uponcompletion of gamma-gamma logging.

PART 5. DATA ANALYSIS AND REPORTING

A. ANALYSIS OF DATA

1. Apply the calibration parametersdetermined in Part 1-B from the concretecalibration samples to the raw countreadings and obtain bulk concretedensities. Verify that the data set containsno logging errors, duplicated data orskipped data points.

2. Determine the mean, mean, of a set ofbulk densities. A set will consist of datacollected from a single inspection pipe,using the same instrument, within thesame time period.

where,

mean = the mean of the group of bulkdensities, as calculated by:


- 7 -

mean 1 ... n

n

3. Data that shall not be included in thecalculation of the mean include:

a) Repetitive data points collected at asingle depth.

b) Data affected by the presence of waterwithin the inspection tube.

c) Data collected at the top of the CIDHpile where the reading(s) wereinfluenced by the gamma detectorcomponent of the probe exiting thepile concrete.

d) Data collected in inspection tubesabove the top of the concrete in aCIDH pile.

e) Data affected by the presence ofanomalous zones of concrete.

f) Data that cause the populationdistribution to be statistically non-normal.

4. In the event that a known difference in thesteel reinforcement schedule exists in asegment of a CIDH pile that affects theapparent mean, a separate mean shall begenerated and utilized as the mean forthat portion of the data.

5. Subtract the mean from each data point inthe set to obtain a data set that reflects thevariation from the mean.

6. Plot the data obtained in Step (3) with thedepth on the y-axis and the variation frommean bulk density on the x-axis.

7. Repeat Step (1) through Step (4) for allinspection tubes contained within anindividual pile and plot that data as asingle plot.

B. STANDARD DEVIATION ANALYSIS

1. Determine the standard deviation, , ofa compilation of bulk densities. Acompilation will consist of data collectedfrom all CIDH piles, of the same diameterand type of construction, using the sameinstrument, within the same time period.If the test is a comparative retest, use thepreviously calculated standard deviation.

2. Standard deviation in a compilation ofpiles is determined by evaluating the datarelative to the following criteria:

1

1

2,

i

Ni

nn

where,

N, n = difference of density of a datapoint from the mean asdetermined by Section 5-A-4

= standard deviation of density ofthe data compilation

i = number of data points

Data that shall not be included in thecalculation of the include:

a) Repetitive data points collected at asingle depth.

b) Data affected by the presence of waterwithin the inspection tube.

c) Data collected at the top of theCIDH pile where the reading(s) wereinfluenced by the gamma detectorcomponent of the probe exiting thepile concrete.

d) Data collected in inspection tubesabove the top of the concrete in aCIDH pile.

e) Data affected by the presence ofanomalous zones of concrete.


- 8 -

f) Data that cause the populationdistribution to be statistically non-normal.

3. If the value calculated in Section 5-B-2is less than 2.5 lb/ft3, use a standarddeviation of 2.5 lb/ft3. If the valuecalculated in Step 5-B-2 exceeds3.75 lb/ft3, use a standard deviation of3.75 lb/ft3.

4. Multiply the value obtained for standarddeviation by –2.0 to obtain a “MinusTwo Standard Deviations” (-2SD) value.Multiply the value obtained for standarddeviation by –3.0 to obtain a “Minus ThreeStandard Deviations” (-3SD) value.

5. Plot at all depths and on all plots ofindividual piles developed in Part 5-A, thevalues for –2SD and –3SD. Utilize symbolsor formatting that permits the linescorresponding to –2SD and –3SD to bedistinguished from data points.

C. ANOMALY IDENTIFICATION

1. Anomalies in a pile are determined byevaluating the data points developed inPart 5-A to the minus three standarddeviation criteria developed in Part 5-B.Piles are determined to be anomalous if:

a) In a single inspection pipe over any0.5-foot or greater depth interval, allof the density readings have a valueless than the determined value forminus three standard deviations.

b) In the same inspection pipe identifiedanomalous by Step 5-C-1-a, within1-foot vertical extent of the previouslyidentified anomaly, any data pointthat falls below the value for minusthree standard deviations shall beconsidered a contiguous anomalousregion.

c) In all inspection pipes adjacent toinspection pipes already identified asanomalous, if at least one data point

within 2-feet vertically of the adjacentpipe anomaly falls below the value forminus three standard deviations, thatpipe is also anomalous.

D. ANOMALY EXTENT

1. Where anomalies have been identified byGamma-Gamma Logging in Part 5-C, themaximum longitudinal and cross-sectionalextent of the anomaly shall be delineated.

2. When an isolated anomaly has beenidentified in a single inspection pipe solelyby Part 5-C-a, the vertical extent of ananomaly shall be from the minimumdepth where a data point is less than threestandard deviations from the mean to themaximum depth where a point is less thanthree standard deviations. Where multipletubes are identified as anomalous at thesame depth, or the same inspection pipeor adjacent inspection pipe is identified asanomalous by Section 5-1-b or 5-1-c, thevertical extent of an anomaly shall befrom the minimum depth where a datapoint in any of the associated pipes is lessthan three standard deviations to themaximum depth where a point in any ofthe associated pipes is less than threestandard deviations. Where multipleanomalies are detected in a single pileand are identified by the Engineer

experienced in gamma-gamma logging tobe independent of each other, theanomalies shall be delineated and sizedseparately.

3. For evaluation of cross-sectional areabased upon Gamma-Gamma Logging, arepresentative sample method shall beutilized to approximate maximum crosssection affected. When additionalinformation is provided that permits theEngineer experienced with gamma-gamma logging to alter the representativesample assessment, engineering judgmentshall be utilized to determine the newprobable maximum extent.


- 9 -

E. REPORTS

1. The report of the gamma-gamma logging,data analysis and results shall include thefollowing information when applicable,and shall be signed and stamped by aCivil Engineer registered in the State ofCalifornia:

a) General.Project identification,Project location,Owner,Pile Designer,*Foundation Designer,*Pile contractor,*Location of pile(s),Designation and location of nearest

test boring with reference to thepile or group of piles beingtested,*

Log of nearest test boring,*

b) Pile Installation.Pile Diameter,Pile length,Pile cutoff elevation,Pile tip elevation,Type and size of drilling equipment,*Type of slurry used,*Description of concrete mix,*Reinforcement details,*Inspection pipe placement,*Concrete placement method,*Date of construction,*Pile layout with pile numbers,*

c) Gamma-Gamma Logging.Date of logging,Brief description of testing equipment,Number of piles logged,Location of inspection tube

obstructions,Log of PVC coupler locations,*Calibration date, data, and plot,*Plots showing variation from mean

bulk density (x-axis) versus depthor elevation (y-axis),

Description and explanation ofadjustments made toinstrumentation or data (if any),

Summary of any unusual occurrencesduring testing,

d) Conclusions.Identification of anomalies.Delineation of Affected TubesVertical Location and Extent of

AnomaliesEstimated Percentage of Cross-

Sectional AreaRecommendations

* Information delineated by an asteriskshall be available on request, but may notbe required for individual gamma-gammalogging reports.

2. The following reports shall be completedand signed and stamped by a CivilEngineer registered in the State ofCalifornia prior to the performance of anyacceptance testing using CTM 233.

a) Gamma-Gamma Probe QualificationReport (see Part 1-D-1).

b) Instrument Calibration Report (seePart 2-A-2).

c) Standard Reference QualificationReport (see Part 2-B-7)

PART 6. SAFETY AND HEALTH

Prior to handling, testing or disposing of anywaste materials, testers are required to read: PartA, Section 5.0, Part B, Sections 5.0, 6.0 and 10.0 andPart C, Section 1.0 of Caltrans Laboratory SafetyManual.

All personnel shall be licensed by all applicableregulatory agencies and shall strictly adhere to allsafety and health requirements includingapplicable Code of Safe Work Practices and site-specific restrictions. Users of this method do so attheir own risk.


- 10 -

APPENDIX A

DETERMINATION OF DENSITY PRECISIONFOR A GAMMA-GAMMA PROBE

A. SCOPE

This Appendix provides the procedures for thedetermination of density precision for a gamma-gamma probe.

B. APPARATUS

The determination of density precision requiresthe utilization of concrete calibration samples asdescribed in Appendix C.

C. PROCEDURE

1. The density precision and sample timeshall be determined for all new probe andsource combinations and configurationsand shall be determined at intervals not toexceed four years. Density precision andsample times shall also be recalculatedwhen maintenance operations areperformed on said gamma-gamma probedetectors. The density precision andminimum required sample time shall beunique for each probe and sourcecombination.

2. Place the probe in Concrete CalibrationSample #2. The concrete calibrationsample shall conform to the requirementscontained in Appendix C.

3. Ensure that the source is a minimum of(0.33)Ssd from the bottom of the concretecalibration sample and that the detector isa minimum of (0.33)Ssd from the top of theconcrete calibration sample, where:

Ssd = distance between the probe’ssource and detector

4. Select a trial sample time.

5. Acquire a minimum of 200 independentconsecutive readings at the trial sample

time in Concrete Calibration Sample #2.If any variation exists in the actualmeasured sample times for individualreadings, any point where the actualsample time for data collection was morethan 10 percent higher or lower than thetrial sample time shall be deleted. Aminimum of 200 data points shall remainafter deletion, or the trial sample timereadings shall be completely reacquired.

6. Acquire a minimum of 50 independentconsecutive points in each of theremaining concrete calibration samples.When performing testing within eachconcrete calibration sample, verify that thesource is a minimum of (0.5)S sd above thebottom of the sample and that the detectoris a minimum of (0.5)Ssd below the top ofthe sample, where:

Ssd = distance between the probe’s sourceand detector

7. With the probe at a constant depth, recorda minimum of 50 count readings withineach remaining calibration concretesample.

8. Calculate the arithmetic mean of the countreadings using the following equation foreach concrete calibration sample,including Concrete Calibration Sample #2:

nC...C

N n1mean

where,

Nmean = Average of countsCn = nth countn = total number of individual

count readings

9. Compute the natural logarithm of themean count (CMLC) for each of thecalibration concrete samples as shownbelow:

meanNMLC ln


- 11 -

where,

Nmean = Average of countsCMLC = natural logarithm of mean gamma

count rate

10. Plot the MLC obtained in Step 9 with theknown density of each concrete calibrationsample. Plot the concrete densities on thex-axis and the corresponding MLC valueson the y-axis.

11. Using the least squares method, establishthe best-fit linear representation to thepoints plotted in Step 10. This linear fitshould take on the form of:

baCMLC

which may be rewritten as:

abCMLC

where,

CMLC = natural logarithm of mean gammacount rate

= concrete densitya = slope of best-fit lineb = y-intercept of best-fit line

12. Determine the standard deviation for thenatural logarithm of the gamma count ratereadings obtained in Concrete CalibrationSample #2.

i

NNi

nmeanCCSnCCS

CCS

1

2,2,2

2

where,

CCS2 = Standard Deviation of the naturallogarithm of the Gamma CountRates for Concrete CalibrationSample #2

NCCS2,mean = Arithmetic Mean of thenatural logarithm ofthe Gamma Count Rates forConcrete CalibrationSample #2

NCCS2,n = Value of the natural logarithmof the Gamma Count Rate number“n”

n = total number of count readings(n 200)

13. Calculate the natural logarithm of thegamma count rates corresponding withthe mean minus one standard deviation.

C= NCCS2,mean - CCS2

where,

NCCS2,mean = Arithmetic Mean of thenatural logarithm of theGamma Count Ratesfor Concrete CalibrationSample #2

CCS2 = Standard Deviation of the naturallogarithm of the Gamma CountRates for Concrete CalibrationSample #2

C- = Mean the natural logarithm of theCount Rate minus One StandardDeviation

14. Determine the densities corresponding tothe NCCS2,mean and C-values.

ab

D

meanCCS2,N

a

bCD

a = The slope of the calibration line, asdetermined in Step 11

b = The “y-intercept” of the calibrationline, as determined in Step 11

D= Density at the MeanD- = Density at One Deviation below

MeanNCCS2,mean = Arithmetic Mean of the

natural logarithm of the


- 12 -

Gamma Count Rates forConcrete Calibration Sample#2

C- = Mean the natural logarithm of theCount Rate minus One StandardDeviation

15. Obtain the precision density, Pd, bycalculating the arithmetic differencebetween Dand D-.

Pd = |D– D-|

where,

Pd = Density PrecisionD= Density at the MeanD- = Density at One Deviation below

Mean

16. Verify that Pd is 1.0 lb/ft3 or less. If Pd

exceeds 1.0 lb/ft3, the probe may not beutilized for gamma-gamma logging at theselected trial sample time. If a longersampling time is possible, a new trialsample time may be selected and thisprocess repeated. If no sample time iscapable of generating a Pd of 1.0 lb/ft3 orless, the probe shall not be utilized forgamma-gamma logging.

17. The sample time utilized shall not begreater than or less than themanufacturer’s recommended sampletime range. For calculated sample timesexceeding the manufacturer’s maximumsample time, the probe shall not beutilized for acceptance testing. Forcalculated sample times less than themanufacturer’s sample time range, thesample time shall be increased to theminimum recommendation by themanufacturer.

18. The smallest sample time that is within therange recommended by the probemanufacturer and possessing a precisiondensity of 1.0 lb/ft3 or less shall bereferred to as the minimum sample time.Gamma-Gamma logging shall not be

performed at a sampling time less than theminimum sample time.

APPENDIX B

DETERMINATION OF RADIUS OF DETECTIONFOR A GAMMA-GAMMA PROBE

A. SCOPE

This Appendix specifies the procedures andequipment required for the determination ofradius of detection for a gamma-gamma probe.

B. APPARATUS

The determination of radius of detection requiresthe utilization of an Influence Determination Unit.

C. PROCEDURE

1. The radius of detection shall bedetermined for all new probe and sourcecombinations and configurations andverified at intervals not to exceed fouryears. Radius of detection shall also berecalculated when maintenance operationsare performed on said gamma-gammaprobe detectors. The radius of detectionshall be unique for each probe and sourcecombination.

2. Radius of Detection shall be determined inan Influence Determination Unit (IDU) asdescribed in Appendix E. The Radius ofDetection shall not be determined in alocation where any other radiation sourcecan be detected above background levelsor any intermittent radiation source ispresent.

3. For all probes less than 1.85-inches inoutside diameter, centralizing devicesshall be used to center the gamma-gammaprobe within the nominal 2-inchSchedule 40 PVC inspection pipe for theIDU. Centralizers shall not be placedaround or between the probe source anddetector or interfere with normal probe


- 13 -

operation. Centralizers shall maintain thegamma-gamma probe within 0.1-inch ofthe longitudinal centerline of theinspection tube.

4. Place the gamma-gamma probe within theIDU. Push the gamma-gamma probethrough the IDU to a point flush with theend of the IDU inspection tube.

5. For each radius of detection datacollection run, pull the gamma-gammaprobe through the IDU, collectingreadings at intervals not to exceed every1.5-inches. The sampling time for intervalsshall be equal to or greater than theminimum sampling time to obtain therequired density precision. Stop datacollection when the source or detectoremerges from the IDU.

6. Perform a minimum of three radius ofdetection data collection runs within theIDU.

7. Plot the gamma count rate for each datapoint collected versus the position alongthe IDU.

8. Determine the Low Density Baseline andHigh Density Baseline. The Low DensityBaseline shall be the relatively consistentvalue for the gamma count rate from1 foot to 3 foot within the IDU, ignoringboundary condition effects. The HighDensity Baseline shall be the relativelyconsistent value for the gamma count ratefrom 15 to 18 feet within the IDU, ignoringboundary condition effects. If the LowDensity Baseline and High DensityBaseline cannot be determined, the probemay not be utilized for acceptance testing.

9. Determine the length of the transitionzone, LTZ. The length of the transition zoneshall be defined as the distance betweenwhere the measured readings begin todeviate from low-density baseline to thepoint where no deviation relative to thehigh density is observable abovebackground scatter.

10. Determine the Radius of Detection,utilizing the following equation:

Rd = (Ltz – Ssd)/12

where,

Rd = The Radius of Detection (in)Ltz = Length of the Transition Zone (in)Ssd = Source to detector spacing (in)

11. For the gamma-gamma probe to beutilized for acceptance testing thefollowing equation must be satisfied:

3-inch Rd 4.5-inch

where,

Rd = Radius of Detection

APPENDIX C

GAMMA-GAMMA PROBE DENSITYCALIBRATION CONCRETE CALIBRATIONSAMPLES

A. SCOPE

This Appendix specifies the requirements for theconcrete calibration samples for use with agamma-gamma probe.

B. APPARATUS

Each concrete sample used to calibrate thegamma-gamma probe to density shall consist of aconcrete mass of fixed shape. Concrete samplesshall cover the range of densities anticipated forthe evaluation of concrete integrity. A minimumof three samples shall be used to establish therelationship between count rate and concretedensity. The concrete samples shall conform to theranges of densities as shown in the following table:


- 14 -

Sample Minimum

lb/ft3Maximum

lb/ft3

1 100 120

2 140 160

3 180 200

PVC Inspection pipes described in Part 3-A-2 shallbe cast into the concrete samples. The minimumdimensions of the calibration concrete samples areprovided in Appendix E.

APPENDIX D

CONSTRUCTION AND QUALIFICATION OF ASTANDARD REFERENCE FOR A GAMMA-GAMMA PROBE

A. SCOPE

This Appendix specifies the construction andqualification of a standard reference for use with agamma-gamma probe.

B. APPARATUS

1. Standard Reference.

a) The dimensions of the standardreference are provided in Appendix E.

b) The standard reference shall beconstructed using portland cementconcrete or a cement grout mixsuch that the block is homogeneouswith a minimum density of 145 lb/ft3.

c) The standard reference shall befabricated such that boundaryconditions around the standardreference do not alter the gammacount rate by more than 3 percent ofthe mean gamma count rate.

2. Gamma-Gamma Probe. The gamma-gammaprobe shall meet the specificationsdescribed in Part 1.

C. PROCEDURE

1. A specific combination of probe, source,and standard reference may be qualifiedfor use by verification that the effect ofboundary conditions does not alter thegamma count rate by more than 3 percentof the mean gamma count rate.

2. The initial qualification shall be unique foreach probe and source combination, andneed only be performed once for eachspecific combination of probe, source andstandard reference proposed for use.

3. The procedure for standard referenceinitial qualification shall not be performedwhere the influence of any otherradioactive source can be detected abovebackground levels.

4. The initial qualification procedure for thestandard reference shall not be performedcloser than 15 feet from any large ormassive object above ground levelelevation including but not limited tostructures, vehicles and trees. Initialqualification shall be performed on asmooth and level portland cement orasphaltic concrete slab of 3-inchesminimum thickness as shown inAppendix E.

5. Place the standard reference in the verticalposition while upon the slab as shown inAppendix E.

6. Place the probe in the standard reference.Ensure that the source is a minimum of Rd

from the bottom of the standard referenceand that the detector is a minimum of Rd

from the top of the standard reference,where,

Rd = Radius of Detection as determinedin Appendix B.

7. Acquire a minimum of 200 independentconsecutive readings at the unit’soperating sample time as determined inAppendix A. Calculate the mean gamma


- 15 -

count rate for vertical position (v) usingthe following equation:

v V1 ... Vn

nwhere,

v = mean gamma count rateVn = nth countn = total number of counts

8. Place the standard reference in thehorizontal position while upon the slab asshown in Appendix E.

9. Acquire a minimum of 200 independentconsecutive readings at the unit’soperating sample time as determined inAppendix A. Calculate the mean gammacount rate for horizontal condition (h)using the following equation:

h H 1 ...H n

nwhere,

h = mean gamma count rateHn = nth countn = total number of counts

10. The following equation shall be satisfiedfor the standard reference to receive initialqualification:

2 *h v

h v

0.03

where,

h = mean gamma count rate forhorizontal condition

v = mean gamma count rate forvertical condition

APPENDIX E

FORMS AND FIGURES

End of Text(California Test 233 contains 21 pages)


- 16 -

Functionality Verification LogStandard Reference Serial Number Probe Make / Model Winch / Probe / Source Serial Numbers

Date Functionality Limits Determined Lower Functionality Limit (LFL) Upper Functionality Limit (UFL)

Date Operator Functionality Determination Readings

N1 N2 N3 N4 Ndaily,mean


- 17 -

Gamma-Gamma Test Set-up Sheet

Structure Name Date TestedBridge No. E.A. OperatorDist./Co./Rte. Dia. Spec. LengthSupport No. Pile No. No. of Inspection Tubes

TubeNo.

TapedDepth

ProbedDepth

SpacingDist.

Stick-Up

Wet/Dryor Water

Depth1

2

3

4

5

6

7

8

Calibration No. Missing Tubes Yes / NoCalibration Date Blocked Tubes Yes / NoDaily Functionality Yes / No Water in Tubes Yes / No

Winch SN Probe SN Source SN

Remarks / Observations

1

N


- 18 -


- 19 -


- 20 -


- 21 -

Documents

METHOD OF ASCERTAINING THE HOMOGENEITY OF … · METHOD OF ASCERTAINING THE HOMOGENEITY OF CONCRETE IN CAST-IN-DRILLED-HOLE (CIDH) PILES USING THE GAMMA-GAMMA TEST METHOD CAUTION: