Rebound hammer & UPV- Non destructive test. Concrete NDT. Civil engineering. Concrete Testing
- 1. Non-Destructive Tests of concrete (REBOUND HAMMER AND ULTRA PULSE VELOCITY TEST)
- 2. Source of Defects in concrete Construction Phase : Improper detailing disregard for quality control Cost control at expense of durability Post construction Phase : Enviromental changes due to increased pollution Industrialization Vehicular traffic And so on..
- 3. Preliminary Knowledge of Building building drawings layout plan construction specifications (type of structure, material used, interconnection elements) Building age, purpose previous investigation reports previous repair work details adjacent structure nearby locations like industries, presence of saline enviroment, sea etc. climatic conditions
- 4. Properties from test reults Strength Density Elastic modulus Homogeneity Absorption and permeability Resistivity De laminations Chemical composition Crack width measurement Surface pressure Steel corrosion Reinforcement Location/cover
- 5. Resistance Factor Should be always greater than ONE.
- 6. Assessment flow diagram - Concrete Technology – A.R.Santhakumar
- 9. Uses Assessing the…. ……likely probable compressive strength of concrete ……uniformity of concrete. ……quality of the concrete in relation to standard requirements ……quality of one element of concrete in relation to another.
- 11. •Calibration against steel anvil having Brinell hardness number of about 5000 N/mm2. •Even and smooth surface •Dry & free of moisture •Perpendicular to surface •Test point at least 20mm away from the edge •At least 9 to 12 readings generally taken Types of Hammers Preparation for test Type M heavy structures and mass concrete N impact energy of 2.2 N-m and is suitable for grades of concrete from M-15 to M-45 L lightweight concrete or small and impact sensitive part of the structure P below M15 grade
- 12. ‘Global’ graph
- 13. Factors affecting the Rebound Number Aggregates Age of concrete Surface smoothness Type of curing Moisture Surface carbonation Stiffness of member Compaction
- 14. BENEFITS Portable Ease of use Instantaneous results No particular skill required Inexpensice
- 15. Discussions Surface properties reflected up to around 30mm Graph not accurate Correlation between rebound number & strength to be done. Structure large as possible at least 150mm thick. Dissipation of impact energy Wet surface gives a lower rebound number Variation in reading about +/-25% Specimen to be rigid Variation is values from person to person
- 16. Rebound Number vs. Strength Paper by - Dr. Andrzej Moczko, Dept of Civil Engineering, Weoclaw Technical University Poland Compressive test results from cores, capo-test and schimdt hammer Structur e No. CTM -Core from structure Rebound hammer on structure Rebound hammer on core 1 19.6 36.9 28.4 2 24.7 37.4 28.4 3 29.7 49.5 38.2 4 34.2 56.8 43.1 5 33.3 61.6 49.3 6 34.2 56.5 36.5 7 35.4 66.3 57 8 37.1 56.9 46.1 9 37.5 70.9 61 10 42 68.4 57.4 Avg - 32.77 56.12 44.54 0 20 40 60 80 0 10 20 30 40 50 CTM Rebound Number Core specimen - Rebound number vs. CTM
- 17. Experiment conduction in SEMT lab on 30.08.16 Grade of concrete : M30 OPC 53 : 375 kg/m3 Correction for water : 20mm passing =0.84% ; 10mm passing=1.62% ; sand=2.88% Coarse : Fine Aggregate = 60:40 Sp gravity: 20mm=2.75 ; 10mm = 2.74 ; sand=2.75 Coarse- 20mm passing:10mm passing= 70:30 Temperature - 28.2 degree celcius Relative Humidity – 79 Age of samples- 7 days and 14 days. Rebound hammer vs. CTM NDT (MPa) CTM (MPa) % diff. 10.5 21.9 52.05 14 33.54 58.26 21 33.92 38.09 22 35.11 37.34 25 35.51 29.60 0 10 20 30 40 0 5 10 15 20 25 30 CTM(MPa) Rebound Hammer (MPa) Compressive strength- Rebound hammer vs. CTM
- 19. ULTRASONIC PULSE VELOCITY TEST Homogeneity Presence of voids, cracks, honeycombs and other deformation Changes in the structure of the concrete with time Quality of the concrete in relation to standard requirements Elastic modulus of concrete Quality comparison between specimen
- 20. • Transducer--one emitting and other receiving • Electrical pulse generator • Amplifier • Electronic timing device
- 21. Based on the propagation of Ultrasonic Pulse waves through the concrete Pulse produced by one trasducer Pulse propagates through path length (L) Other transducer receives the pulse of vibrations and converts into electronic signal Electronic timing circuit gives the transit Time (T) Wave Velocity --- V = L/T
- 22. longitudinal waves Transverse waves love waves Rayleigh waves Travel fastest Near the surface
- 23. Propagation of waves Path Length (mm) Natural Frequency of transducer (kHz) Minimum Transverse Dimensions of Members (mm) Upto 500 150 25 500-70 >60 70 700-1500 >40 150 Above 1500 >20 300 As per IS-13311.1.1992 • Denser the medium higher the velocity and vice versa • Independent of geometry of material. • Depends on the elastic property of the material • Transducer operating with frequency range of 20 kHz to 150 kHz generally used
- 24. Methods of probing Good quality concrete has a difference less than 0.5km/sec between direct and indirect methods.
- 25. Pulse Velocity by cross probing (direct method)- km/s Concrete Quality Grading Above 4.5 Excellent 3.5 to 4.5 Good 3.0 to 3.5 Medium Below 3.0 Doubtful* IS-13311(Part-1) gives a velocity criteria for grading quality of concrete *Incase of doubtfull quality further tests may be required The Young’s modulus of elasticity (E) E= 𝑝(1 + 𝑢)(1 − 2𝑢)𝑉𝑥𝑉 / (1 − 𝑢) Where; E = dynamic Young’s Modulus of elasticity 𝑝= density in kg/ms, 𝑉 = pulse velocity in m/second 𝑢 = Poissons ratio
- 26. Factors affective UPV Age of concrete – Velocity increases with age Moisture of concrete – More moisture leads to higher velocity Amount and type of aggregate- Type and Size Micro cracking- Cracks reduce elastic modulus .Wave velocity reduces Presence of reinforcement- Velocity in RCC is 1.2 to 1.9 times more than that of plain cement comncrete of same mix minimum path length Nominal size of agg. 100 mm </= 20 mm 150 mm 20 to 40 mm
- 27. Strength vs. Ultrasonic pulse velocity No direct correlation exists Self generated equation can be obtained by relating the wave velocity with strength results provided concrete should have -- -Similiar mix -Method of compaction -Exposure conditions -Curing methods etc.,
- 28. In a paper by Cengiz Kurtulus and Ali Bozkurt- “Determination of concrete compressive strength of the structures in Istanbul and Izmit Cities (Turkey) by combination of destructive and non-destructive Methods”, Linear equation was generated by relating the- UPV of different structures Compressive test on the same core drilled A total of 200 readings were taken.
- 29. Combined method using UPV & Rebound hammer Better accuracy Better correlation Compensates limitation of each method Correlation valid for specimen with same mix, exposure etc. However variability of one property may have opposite effect for the other method Eg. – rise in moisture increase the pulse velocity but reduces the rebound number When the UPV gives higher result only then the Rebound value on surface can be assumed to reflect the properties of bulk If very low UPV obtained Rebound value cannot be used to get the properties of concrete as a whole.
- 30. SONREB A very useful tool to determine probable strength of concrete using both UPV & Rebound hammer Developed with help of RILEM technical committee- 7 NDT and TC-43 CND .Originated in Romania and developed further in Australia and Europe IN SONREB the in situ compressive strength of a structure can be found by the following expression ---(I) a, b, c are constants V - Ultrasonic Pulse Velocity R - Rebound Number From microsoft excel Linest Function valus of a,b,c can be obtained from UPV and Rebound number
- 31. Researchpaper- Useofcombineddestructivetestingintheconcretestrengthassessmentfromlaboratoryspecimenandexistingbuilding By-MulikNikhil,BalkiMinal,ChhabriaDeep,GhareVijay,TeleVishal, Mrs.Patil Shweta-Asst.Prof.inCivilEngineering DepartmentOfCivilEngineering,GenbaSopanraoMozeCollegeofEngineering,UniversityOfPune,India 60 cube specimen were prepared using various mixes from M15 to M40 and cured for 28 days The UPV, Rebound hammer and compressive testing of each was done . For above values-- a=1.64111E-09 b=2.293662304 c=1.30768373