Non destructive test on concrete (ndt)

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Non destructive test on concrete (ndt)

  1. 1. Abhishek gupta Vikas Dubey
  2. 2. NDT • Powerful technique for evaluating exiting concrete structures with regard to their strength and durability apart from assessment and control of quality of hardened concrete without or partial damage to the concrete. • Concrete is not loaded to the failure, therefore, the strength inferred or estimated can not be expected to yield absolute value of strength.
  3. 3. • Destructive testing – Huge Cost initially has to put in for taking sample and then to test it. • NDT – Its very easy and simple process and a lot many tests can be performed on concrete less than single amount require for sampling of concrete Cost Effectiveness
  4. 4. Deliverables of NDT
  5. 5. • Rebound Hammer Test: To estimate strength and hardness of the concrete in the cover region (IS: 13311 Part II) • UPV Test: To measure homogeneity, uniformity, compactibility and presence of crack or void, thus representing durability of concrete (IS: 13311 Part I). • Core Test: To evaluate in situ compressive strength of concrete (IS 516 & ASTM C42/41) • Corrosion Assessment: Half Cell Potential (ASTM C876-9), Resistivity and RCPT (ASTM C1202), to know about extent and rate of ongoing corrosion activity. • Bar Locater and Cover Meter: To know the structural strength and protection to the reinforcement by cover concrete. • Carbonation: To evaluate extent of carbonation for strength and corrosion estimation. HOW NDT INVESTIGATION HELPS IN ASSESSMENT?
  6. 6. OBJECTIVES • To assess quality of the concrete in relation to the standard requirements • To estimate compressive strength of concrete with the help of suitable correlations between rebound index & compressive strength • To delineate regions of poor quality or deteriorated concrete in a structure • To assess quality of one element of the concrete in relation to another REBOUND HAMMER
  7. 7. Rebound hammer
  8. 8. FACTORS AFFECTING THE TEST RESULTS
  9. 9. Mechanism of Rebound Hammer
  10. 10. Average Rebound Number Quality of Concrete more than 40 Very good hard layer 30 to 40 Good layer 20 to 30 Fair less than 20 Poor concrete 0 Delaminated INTERPRETATION OF THE TEST RESULTS
  11. 11. OBJECTIVES • To assess uniformity and homogeneity of concrete • To assess quality of concrete in relation to standard requirements • Detection of the presence & 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 PULSE VELOCITY
  12. 12. 1. Smoothness of contact surface under test 2. Influence of path length on pulse velocity 3. Temperature of concrete 50 – 300 Ideal 300 – 600 (Reduction in UPV up to 5%) Below 50 (Increase up to 7.5%) 4. Moisture condition of concrete (pulse velocity is proportional to moisture content) 5. Presence of reinforcing steel (UPV of R/f is 1.2 to 1.9 times than normal concrete) 6. Stress Level in concrete FACTORS AFFECTING TEST RESULTS
  13. 13. • Ultra sonic pulse velocity meter
  14. 14. Techniques measuring for pulse Velocity Test
  15. 15. Velocity criteria for concrete quality grading INTERPRETATION OF THE TEST RESULTS
  16. 16. OBJECTIVES • To evaluate potential of concrete in promoting corrosion activity of reinforcement by Half Cell Potential test • To evaluate reinforcing steel in concrete that has carbonated to the level of the embedded steel • To compare corrosion activity in outdoor reinforced concretes of highly variable moisture or oxygen content, or both, at the embedded steel Half Cell Potential
  17. 17. • Moisture • Temperature • Concrete Cover Thickness • Oxygen content of the reinforcement Half cell potentiometer FACTORS AFFECTING TEST RESULTS
  18. 18. Potential over an area Most likely outcome more positive than -0.20 V CSE 90% probability that no reinforcing steel is corroded (at the time of test) -0.20 to -0.35 V CSE corrosion activity of the reinforcing steel more negative than -0.35 V CSE 90 % probability that reinforcing steel is corroded Interpretation of Test results
  19. 19. OBJECTIVES: To assess 1. pH of the concrete 2. corrosion Chemical used: Phenolthalein solution (colour less below a pH of 8.2 and is pink/purple at a pH greater than 10.0) commercially available indicator measures pH from 1 to 14 with a rainbow spectrum Carbonation Test
  20. 20. • Dark concrete • Saturation • Extent of drilling Factors affecting test results
  21. 21. Carbonated concrete
  22. 22. OBJECTIVES To assess 1. diameter 2. location of the R/F 3. cover profometer Cover meter test
  23. 23. • cover measurement maybe 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 the steel • cross-sectional shape of bars • roughness of the surface Factors affecting test results
  24. 24. THANK YOU!

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