11

NDT OF CONCRETENDT OF CONCRETE

22

CUBE TESTCUBE TEST

INDICATES ONLY POTENTIAL STRENGTHINDICATES ONLY POTENTIAL STRENGTH SUBJECT TO UNINTENTIONAL DEVIATIONS SUBJECT TO UNINTENTIONAL DEVIATIONS DELIBERATE DEVIATION ?DELIBERATE DEVIATION ? NOT A TRUE REPRESENTATIVE OF THE NOT A TRUE REPRESENTATIVE OF THE

STRUCTURE DUE TO PRESENCE OF STRUCTURE DUE TO PRESENCE OF STEEL, VOIDS, CRACKS & DIFFERENT STEEL, VOIDS, CRACKS & DIFFERENT DIMENSIONSDIMENSIONS

CANNOT BE VERIFIEDCANNOT BE VERIFIED CAN BE ONLY PERFORMED DURING CAN BE ONLY PERFORMED DURING

CONSTRUCTION STAGECONSTRUCTION STAGE

33

N D T - OBJECTIVESN D T - OBJECTIVESTO ESTABLISH HOMOGENEITY OF TO ESTABLISH HOMOGENEITY OF

CONC.CONC.COMPARISON OF CONCRETE COMPARISON OF CONCRETE

QUALITY w.r.t. A STANDARDQUALITY w.r.t. A STANDARDDETECTION OF CRACKS, VOIDS/ DETECTION OF CRACKS, VOIDS/

OTHER IMPERFECTIONSOTHER IMPERFECTIONSMONITORING CHANGES IN MONITORING CHANGES IN

CONCRETE WITH PASSAGE OF TIMECONCRETE WITH PASSAGE OF TIMETO ESTABLISH QUALITY OF ONE TO ESTABLISH QUALITY OF ONE

ELEMENT w.r.t. ANOTHERELEMENT w.r.t. ANOTHER

44

N D T - OBJECTIVESN D T - OBJECTIVES

ASSESSMENT OF EXISTING STRUCTURE ASSESSMENT OF EXISTING STRUCTURE FOR REHABILITATION PLANNINGFOR REHABILITATION PLANNING

AS AN ALTERNATIVE TESTING METHOD AS AN ALTERNATIVE TESTING METHOD IF CUBE RESULTS RAISE DOUBTS IF CUBE RESULTS RAISE DOUBTS ABOUT CONCRETE QUALITY (POST ABOUT CONCRETE QUALITY (POST MORTEM)MORTEM)

55

N D T - METHODSN D T - METHODS

VISUAL INSPECTIONVISUAL INSPECTION REBOUND HAMMERREBOUND HAMMER ULTRASONIC PULSE VELOCITY METERULTRASONIC PULSE VELOCITY METER PENETRATION RESISTANCEPENETRATION RESISTANCE PULL OUT STRENGTHPULL OUT STRENGTH COVER METERCOVER METER CARBONATION DEPTHCARBONATION DEPTH CORROSION MAPPINGCORROSION MAPPING MATURITY METERMATURITY METER PERMEABILITY TESTPERMEABILITY TEST RADIOGRAPHYRADIOGRAPHY

66

REBOUND HAMMERREBOUND HAMMER

MOST COMMON NDT METHODMOST COMMON NDT METHOD DEVELOPED IN 1948DEVELOPED IN 1948 MEASURES REBOUND HARDNESS OF MEASURES REBOUND HARDNESS OF

CONCRETECONCRETE NO THEORETICAL RELATIONSHIP NO THEORETICAL RELATIONSHIP

AVAILABLE FOR ASSESSMENT OF AVAILABLE FOR ASSESSMENT OF STRENGTHSTRENGTH

EMPIRICAL RELATIONSHIP BETWEEN EMPIRICAL RELATIONSHIP BETWEEN REBOUND HARDNESS AND STRENGTH REBOUND HARDNESS AND STRENGTH DEVELOPEDDEVELOPED

77

REBOUND HAMMER - GUIDELINESREBOUND HAMMER - GUIDELINES

CONDUCT ON SMOOTH AND UNIFORM CONDUCT ON SMOOTH AND UNIFORM FACEFACE

AVOID ROUGH SPOTS, HONEY COMBSAVOID ROUGH SPOTS, HONEY COMBS AVOID TROWELLED SURFACESAVOID TROWELLED SURFACES THIN SECTIONS (< 100 mm) SHOULD BE THIN SECTIONS (< 100 mm) SHOULD BE

BACKED UP TO AVOID DEFLECTIONSBACKED UP TO AVOID DEFLECTIONS TAKE ATLEAST 15 REBOUND READINGS TAKE ATLEAST 15 REBOUND READINGS

IN ANY ONE TESTIN ANY ONE TEST

88

REBOUND HAMMER - GUIDELINESREBOUND HAMMER - GUIDELINES

CALCULATE THE MEANCALCULATE THE MEAN COMPARE DEVIATION OF READINGS COMPARE DEVIATION OF READINGS

FROM THE MEANFROM THE MEAN TEST IS CONSIDERED RELIABLE IF THE TEST IS CONSIDERED RELIABLE IF THE

DEVIATION OF TEN READINGS IS NOT DEVIATION OF TEN READINGS IS NOT MORE THAN THE FOLLOWING:MORE THAN THE FOLLOWING:

REBOUND VALUEREBOUND VALUE 1515 3030 4545

DEVIATIONDEVIATION 2.52.5 33 3.53.5

99

REBOUND HAMMER - GUIDELINESREBOUND HAMMER - GUIDELINES

USE BEST 10 READINGS FOR USE BEST 10 READINGS FOR CALCULATING THE MEANCALCULATING THE MEAN

DETERMINE COMPRESSIVE STRENGTH DETERMINE COMPRESSIVE STRENGTH BY REFERRING TO REBOUND NUMBER BY REFERRING TO REBOUND NUMBER Vs STRENGTH CHARTS AGAINST THE Vs STRENGTH CHARTS AGAINST THE MEAN VALUEMEAN VALUE

BEST ACCURACY ACHIEVEABLE IS BEST ACCURACY ACHIEVEABLE IS WITHIN WITHIN ++ 20% 20%

1010

FACTORS AFFECTING REBOUND FACTORS AFFECTING REBOUND VALUEVALUE

TYPE OF AGGREGATESTYPE OF AGGREGATES DEGREE OF COMPACTIONDEGREE OF COMPACTION AGE OF CONCRETEAGE OF CONCRETE DRYNESS/WETNESS OF THE SURFACEDRYNESS/WETNESS OF THE SURFACE RIGIDITY OF THE MEMBERRIGIDITY OF THE MEMBER SURFACE FINISH OF CONCRETE- MOULDED/ SURFACE FINISH OF CONCRETE- MOULDED/

TROWELEDTROWELED MAINTENANCE OF REBOUND HAMMERMAINTENANCE OF REBOUND HAMMER INCLINATION OF THE REBOUND HAMMERINCLINATION OF THE REBOUND HAMMER TYPE OF CEMENTTYPE OF CEMENT CARBONATIONCARBONATION COVERCOVER

1111

PULSE VELOCITY METHODPULSE VELOCITY METHOD

DEVELOPED IN 1940s DEVELOPED IN 1940s BASED UPON PROPOGATION OF BASED UPON PROPOGATION OF

ULTRASONIC WAVES IN ELASTIC ULTRASONIC WAVES IN ELASTIC MEDIUMMEDIUM

MEASURES VELOCITY OF PROPOGATION MEASURES VELOCITY OF PROPOGATION OF ULTRASONIC WAVESOF ULTRASONIC WAVES

VELOCITY RELATED TO THE DENSITY OF VELOCITY RELATED TO THE DENSITY OF THE MEDIUM V=(E/p)THE MEDIUM V=(E/p)1/21/2

STRENGTH IS DEDUCED FROM THE STRENGTH IS DEDUCED FROM THE DENSITY OF THE MEDIUMDENSITY OF THE MEDIUM

FREQUENCY OF WAVES USED - 20 - 150 FREQUENCY OF WAVES USED - 20 - 150 kHzkHz

1212

PULSE VELOCITY METHODPULSE VELOCITY METHOD

TYPES OF TESTING METHODTYPES OF TESTING METHODDIRECT TRANSMISSION DIRECT TRANSMISSION SEMI DIRECT TRANSMISSIONSEMI DIRECT TRANSMISSIONSURFACE TRANSMISSIONSURFACE TRANSMISSION

DIRECT TRANSMISSION METHOD IS THE DIRECT TRANSMISSION METHOD IS THE BEST BUT IT REQUIRES ACCESS TO TWO BEST BUT IT REQUIRES ACCESS TO TWO OPPOSITE SIDES OF CONCRETE OPPOSITE SIDES OF CONCRETE MEMBER MEMBER

1313

DIRECT TRANSMISSIONDIRECT TRANSMISSION

TRANSMITTERTRANSMITTER

RECEIVERRECEIVER

1414

SEMI DIRECT TRANSMISSIONSEMI DIRECT TRANSMISSION

TT

RR

1515

SURFACE TRANSMISSIONSURFACE TRANSMISSION

TT RR

1616

PULSE VELOCITY RATINGSPULSE VELOCITY RATINGS

QUALITY PULSE VELOCITY km/sec

Excellent > 4.6

Good 3.7 to 4.6

Fair 3.0 to 3.7

Poor 2.1 to 3.0

Very poor < 2.1

1717

FACTORS AFFECTING PULSE FACTORS AFFECTING PULSE VELOCITYVELOCITY

DEGREE OF COUPLINGDEGREE OF COUPLING PRESENCE OF REINFORCEMENTPRESENCE OF REINFORCEMENT CONCRETE TEMPERATURECONCRETE TEMPERATURE MOISTURE CONTENTMOISTURE CONTENT MIX PROPORTIONMIX PROPORTION AGE OF CONCRETEAGE OF CONCRETE STRESS LEVEL IN CONCRETESTRESS LEVEL IN CONCRETE CONCRETE STRENGTH CAN BE CONCRETE STRENGTH CAN BE

PREDICTED WITHIN PREDICTED WITHIN ++ 20% PROVIDED 20% PROVIDED CALIBRATION CURVE IS ESTABLISHEDCALIBRATION CURVE IS ESTABLISHED

1818

APPLICATIONS OF PULSE APPLICATIONS OF PULSE VELOCITY METHODVELOCITY METHOD

MAIN APPLICATION FOR ASSESSMENT MAIN APPLICATION FOR ASSESSMENT OF CONCRETE UNIFORMITYOF CONCRETE UNIFORMITY

TO ESTABLISH AREAS OF TO ESTABLISH AREAS OF DETERIORATED CONCRETEDETERIORATED CONCRETE

DETECTION OF CRACKS DETECTION OF CRACKS CALCULATION OF DYNAMIC YOUNG’S CALCULATION OF DYNAMIC YOUNG’S

MODULUSMODULUS

1919

COVER METERCOVER METER

COVER IS A VERY IMPORTANT COVER IS A VERY IMPORTANT PARAMETER DICTATING DURABILITY OF PARAMETER DICTATING DURABILITY OF CONCRETECONCRETE

COVER PROVIDED IS INADEQUATE COVER PROVIDED IS INADEQUATE MORE OFTEN THAN NOTMORE OFTEN THAN NOT

CONVENTIONALLY PROVISION OF CONVENTIONALLY PROVISION OF COVER IS CHECKED PRIOR TO COVER IS CHECKED PRIOR TO CONCRETING CONCRETING

POST FACTO ASSESSMENT OF COVER IS POST FACTO ASSESSMENT OF COVER IS POSSIBLE THROUGH COVER METERSPOSSIBLE THROUGH COVER METERS

2020

COVER METERCOVER METER

BASED ON MAGNETIC PRINCIPLEBASED ON MAGNETIC PRINCIPLE RANGE OF MEASUREMENT POSSIBLE IS RANGE OF MEASUREMENT POSSIBLE IS

0-75 mm0-75 mm ACCURACY WITHIN 6 mmACCURACY WITHIN 6 mm NOT VERY EFFECTIVE IN HEAVILY NOT VERY EFFECTIVE IN HEAVILY

REINFORCED MEMBERS OR MEMBERS REINFORCED MEMBERS OR MEMBERS WITH SPIRAL REINFORCEMENTWITH SPIRAL REINFORCEMENT

SIZE OF THE REINFORCEMENT BAR IS SIZE OF THE REINFORCEMENT BAR IS REQUIRED TO BE KNOWN FOR REQUIRED TO BE KNOWN FOR ACCURATE ASSESSMENT OF COVERACCURATE ASSESSMENT OF COVER

2121

APPLICATION OF COVER METERAPPLICATION OF COVER METER

REHABILITATION PLANNINGREHABILITATION PLANNING ASSESSMENT OF RESIDUAL TIME TILL ASSESSMENT OF RESIDUAL TIME TILL

INITIATION OF CORROSIONINITIATION OF CORROSION TO IMPROVE QUALITY CONTROL DURING TO IMPROVE QUALITY CONTROL DURING

CONSTRUCTIONCONSTRUCTION IDENTIFICATION OF LOCATION OF IDENTIFICATION OF LOCATION OF

REINFORCEMENT BAR WITH THE REINFORCEMENT BAR WITH THE FOLLOWING APPLICATIONSFOLLOWING APPLICATIONSHELPS IN AVOIDING DRILLING INTO THE HELPS IN AVOIDING DRILLING INTO THE

REINFORCEMENTREINFORCEMENTTO AVOID REINFORCEMENT IN PULSE TO AVOID REINFORCEMENT IN PULSE

VELOCITY MEASUREMENTSVELOCITY MEASUREMENTS

2222

CARBONATION DEPTHCARBONATION DEPTH

CARBONATION IS CHEMICAL REACTION CARBONATION IS CHEMICAL REACTION BETWEEN Ca (OH)BETWEEN Ca (OH)22 AND CO AND CO22 OF THE OF THE

ATMOSPHEREATMOSPHERE CARBONATION DESTROYS PASSIVE CARBONATION DESTROYS PASSIVE

PROTECTION PROVIDED BY CONCRETE PROTECTION PROVIDED BY CONCRETE TO THE REINFORCEMENTTO THE REINFORCEMENT

CARBONATION PROCEEDS FROM THE CARBONATION PROCEEDS FROM THE SURFACE INTO THE CONCRETESURFACE INTO THE CONCRETE

WHEN DEPTH OF CARBONATION WHEN DEPTH OF CARBONATION EQUALS CONCRETE COVER EQUALS CONCRETE COVER REINFORCEMENT CORROSION IS REINFORCEMENT CORROSION IS IMMINENTIMMINENT

2323

CARBONATION DEPTHCARBONATION DEPTH

METHOD OF ASSESSMENTMETHOD OF ASSESSMENTDRILL INTO CONCRETEDRILL INTO CONCRETESPRAY PHENOLPHTHALEIN SOLUTION SPRAY PHENOLPHTHALEIN SOLUTION UNCARBONATED CONCRETE WILL SHOW UNCARBONATED CONCRETE WILL SHOW

BRIGTH PINK STAINBRIGTH PINK STAINCARBONATED CONCRETE WILL NOT CARBONATED CONCRETE WILL NOT

CHANGE COLOURCHANGE COLOURWITH THE ABOVE VISUAL INDICATION DEPTH WITH THE ABOVE VISUAL INDICATION DEPTH

OF CARBONATION CAN BE EASILY OF CARBONATION CAN BE EASILY MEASUREDMEASURED

2424

LIMITATIONS OF N D TLIMITATIONS OF N D T

ALL NDT METHODS ARE INDIRECTALL NDT METHODS ARE INDIRECT CORELATION BETWEEN MEASURED CORELATION BETWEEN MEASURED

PARAMETER AND CONCRETE STRENGTH PARAMETER AND CONCRETE STRENGTH IS NEVER EXACT.IS NEVER EXACT.

EFFECTIVENESS OF NDT REDUCES WITH EFFECTIVENESS OF NDT REDUCES WITH HETEROGENEITY OF THE MATERIAL HETEROGENEITY OF THE MATERIAL

RESULTS ARE DEPENDENT ON TOO RESULTS ARE DEPENDENT ON TOO MANY PARAMETERSMANY PARAMETERS

NORMALLY ACHIEVEABLE LEVEL OF NORMALLY ACHIEVEABLE LEVEL OF ACCURACY IS ACCURACY IS + + 25%25%

INTERPRETATION OF RESULTS REQUIRE INTERPRETATION OF RESULTS REQUIRE INTUITIVE JUDGEMENT INTUITIVE JUDGEMENT

2525

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