Non-Destructive Testing

KHRI has recently incorporated various Non-Destructive Tests (NDT) in its Concrete & Structures Lab and Flexible Pavements Lab. NDT refers to an array of inspection methods that allow inspectors to evaluate and collect data about a material, system, or component without permanently altering it. Durability, strength, and viability of any structure are crucial before occupying it for any use. Therefore, any civil engineering structure, new or old, can be assessed if required to learn and evaluate longevity, resistance, and stability. The conventional method for evaluation of the quality of structural elements is by collecting samples while under construction. However, the test results of such specimens can vary drastically from the erected structure. Non-Destructive Testing methods help overcome this drawback, consequently increasing the reliability. Thus, not only do they give the exact picture of the tenability of the concrete structure, but they also elaborate on factors like hardness of the concrete, resistance, rebound capacity, and the suitability of a structure for any intended use.

      NDT instruments in KHRI

KHRI now has a collection of NDT equipment used regularly for various pilot projects. For instance, we employed non-destructive tests recently for condition assessment of the Kadaloondi Kadavu Bridge. NDT has also been used to assess the strength of two RCC culverts in Alappuzha.

The NDT equipment in KHRI are as given below:

1. Corrosion rate meter/ GALVAPULSE 

                                                                                                                                                             

The GalvaPulse is used to measure the corrosion rate of reinforcement in concrete. It overcomes all the disadvantages of the Half-Cell Potential (HCP) test. It determines precisely the Galvanostatic pulse measurements, the HCP value, the Corrosion Rate and the Resistance, all in one operation.

2.Profometer / Cover Meter

 

                                                                                                      

Profometer or rebar locator or cover meter is a small, portable, and handy NDT instrument mainly used to determine the size, location, cover depth and condition of rebars in an existing structure. The reinforcement must be located before drilling and cutting concrete cores from an existing structure for evaluating various chemical and physical parameters like chloride diffusion, compressive strength, carbonation depth etc. 

3. Half Cell Potential Tester

                                                                                                                                                                 

This instrument measures the half cell potential difference between the reinforcement and the surface concrete to evaluate the corrosion activity at the testing point. 

4. Ground Penetrating Radar (GPR)

                                                                                                                                        

Ground Penetrating Radar (GPR) is a popular instrument owing to its quick approach for non-destructive mapping of rebars, delaminations and defects in reinforced concrete elements using radio waves. It also evaluates the thickness of concrete members and helps in detecting voids.

5. Ultrasonic Pulse Velocity Tester

                                                                                                                                                                  

It is an in-situ, non-destructive tester used to check the quality or integrity of the concrete. The instrument measures the time taken for ultrasonic pulse waves to pass through concrete, which is a measure of the elastic properties and integrity of the concrete.

6. Ultra Sonic Tomography  

                                                                                                                                                                    

It is an NDT technique used to visualise the interior of concrete with the help of ultrasonic pulse waves. The instrument is capable of detecting delamination, internal flaws, voids etc., within concrete.

7. Rebound Hammer

                                                                                                                                                                       

A Schmidt hammer - also known as a Swiss hammer or a rebound hammer, is an NDT device used to measure the surface hardness of concrete. It helps to assess the compressive strength of concrete using standard correlation curves. 

8. Pendulum Friction-Coefficient Testing Machine

                                                                                                                                                                   

It is a dynamic pendulum-type NDT machine that provides Transportation Engineers with a routine method of checking the resistance of wet & dry surfaces to slipping and skidding.

9. Concrete Surface Resistivity Meter (Resipod)

                                                                                                                                                                       

The Resipod is a fully integrated 4-point Wenner probe used to perform surface resistivity measurements on concrete. It predicts the corrosion potential of concrete based on the surface resistance values. Resipod is extremely fast, stable, and packaged in a robust, waterproof housing designed to operate in a demanding site environment.

There are currently six tests in the non-destructive category for Reinforced Concrete Structures accredited with NABL in KHRI. They are as follows: 

• Carbonation Test (BS EN 14630)
• Cover Meter Test (BS 1881 Part 204)
• Half Cell Potential Difference test (ASTM C876)
• Rebound Hammer Test (ASTM C805/C805M)
• Rebound Hammer Test (IS 516: Part 5: Sec 4)
• Ultrasonic Pulse Velocity Tests (IS 516: Part 5/section 1)