Non Destructive techniques.pptx

Non Destructive techniques

Non Destructive techniquesBYDhairyashil ShindeOmkar TidkeChetan ButleVinit PatilPravinkumar A.K.Vikram ChoudharyJennifer Rajkumari.NDT for Concrete: IntroductionPowerful Technique for evaluating with regard to their strength and durability apart from assessment and quality of hardened concrete without or partial damage to concrete.

Concrete is not loaded to failure, therefore, the strength inferred or estimated cannot be expected to yield actual value of strength.Cost EffectivenessDestructive Testing : Huge Cost is initially required for taking the sample and then to test it.

NDT : It is very easy and simple and a lot many tests can be performed on concrete less than single amount required for sampling of concrete.

4Assessment using NDT Investigation.Rebound Hammer Test: To estimate the strength and hardness of Concrete in the Cover region. (IS 13311 Part 2).UPV Test: To measure uniformity, homogeneity, compactibility and presence of cracks or voids, thus representing durability of Concrete. (IS 13311 Part 1).Core Test: To evaluate in-situ compressive strength of Concrete. (IS 156 & ASTM C42/41)Corrosion Potential: Half Cell Potential (ASTM C876-9), Resistivity and RCPT (ASTM C1202), to know about extent and rate of on going corrosion.Bar Locater and Cover Meter: To know the structural strength and protection to reinforcement by cover concrete.Carbonation: To evaluate extent of Carbonation for strength and corrosion estimation.Rebound Hammer testObjectives:To assess the quality of concrete in relation to standard requirements.To estimate the Compressive Strength of Concrete with the help of suitable corrections between rebound index & compressive strength. To delineate regions of Poor Quality or deteriorated Concrete in a structure.To access quality of one element of the concrete to other.

Rebound Hammer Apparatus

FACTORS AFFECTING THE TEST RESULTSType of CementsType of AggregateSurface Condition & Moisture Content of ConcreteCuring and Age of ConcreteCarbonation of Concrete SurfaceMechanism of Rebound Hammer

INTERPRETATION OF THE TEST RESULTSAverage Rebound NumberQuality of ConcreteMore than 40Very Good Hard Layer30 to 40

Good Layer20 to 30Fair LayerLess than 20Poor Concrete0DelaminatedULTRASONIC PULSE VELOCITYOBJECTIVESTo access uniformity and homogeneity of ConcreteTo access the quality of Concrete in relation to standard requirementsDetection of the presence and approximate extent of Cracks, Voids & other imperfection in concrete.Measurement of changes occurring with time in the properties of the concrete.Correlation of Pulse velocity & strength as a measure of Concrete quality.Ultrasonic pulses: with a frequency of 20 khz or more. Beyond the range of sound perceptible to human ear.11FACTORS AFFECTING TEST RESULTSSmoothness of Contact SurfaceInfluence of path length on pulse velocityTemperature of Concrete 5 - 30 Ideal 30 - 60 (Reduction in UPV upto 5%) Below 5 (Increase upto 7.5%)Moisture condition of concrete (pulse velocity is proportional to moisture Content)Presence of reinforcing steel (UPV of R/f is 1.2 to 1.9 times than normal concrete)Stress level in Concrete. Ultrasonic Pulse Velocity Meter

Techniques measuring Pulse Velocity

Interpretation of Test ResultsVelocity criteria for concrete quality grading.

Pullout TestThe fundamental principle behind pull out testing is that the test equipment designed to a specific geometry will produce results (pull-out forces) that closely correlate to the compressive strength of concrete.

UsesDetermine in-situ compressive strength of the concrete Ascertain the strength of concrete for carrying out post tensioning operations. Determine the time of removal of forms and shores based on actual in-situ strength of the structure. Terminate curing based on in-situ strength of the structure.

Half Cell PotentialOBJECTIVES To evaluate potential of concrete in promoting corrosion activity of reinforcement by half cell potential testTo evaluate reinforcing steel in concrete that has carbonated to the level of the embedded steelTo compare corrosion activity in outdoor reinforced concretes of highly variable moisture or oxygen content, or both, at the embedded steel.FACTORS AFFECTING TEST RESULTSMoistureTemperatureConcrete ThicknessOxygen content of the reinforcementimplicitHalf cell Potentiometer

Half cell Potentiometer

INTERPRETATION OF TEST RESULTSMore positive than -0.20 V CSE

-0.20 to -0.35 V CSE

More negative than -0.35 V CSE90% probability that no reinforcing steel is corroded(at the time of test)

Corrosion activity of the reinforcing steel

90% probability that reinforcing steel is corrodedPotential over an areaMost likely outcomeCarbonation TestOBJECTIVESTo assess1. pH of the concrete2. Corrosion

Chemicals used: Phenolphthelein solution (colourless below a pH of 8.2 and is pink/purple at a pH greater than 10)Commercially available indicator measures pH from 1 to 14 with a rainbow spectrumFactors affecting test resultsDark concreteSaturationExtent of drillingCarbonated concrete

Cover meter testOBJECTIVES:To assessDiameter.Location of the R/F.Cover.

Factors affecting test resultsCover measurement may be affected by neighbouring bars parallel to the bar being measured.Magnetic effects from the aggregate or matrix of the concrete.Variations in the properties of steel.Cross-sectional shape of bars.Roughness of the surface.Thank You