PSI - Issue 52

Rakesh Katam et al. / Procedia Structural Integrity 52 (2024) 72–88 Rakesh Katam/ Structural Integrity Procedia 00 (2019) 000 – 000

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3.3. Non-destructive testing The extent of the building's damage and the regions that require NDT testing can be determined with the help of conditional mapping. RH, UPV, profo-meter, crack width measurement, carbonation test, and half-cell potential are the recommended NDT for the present investigation. For reinforcement, a half-cell potential and profo-meter are used, and the specifications and standard references are presented in Table 2. To assess the quality of the concrete, RH, UPV, and carbonation tests are employed. This NDT was carried out in a direct, semi-direct, and indirect manner at particular locations on each structural element and tested the concrete's surface hardness and integrity using RH (Shaik et al. (2020)) and UPV with a minimum spacing of 25 mm at each point. Profo-meter and half Cell Potential were used to measure the location and percentage of corrosion. Visual inspection was used to select the locations and the number of test points.

Table 2. NDT test standards and measured parameters. Name of the test

Standard reference IS: 13311-part 2 IS: 13311-part 1

Measured

Rebound Hammer

Surface hardness Integrity of concrete Width of the crack Re-bar & cover depth Probability of corrosion Depth of carbonation

UPV

Crack width Profo-meter

- -

Half-cell potential Carbonation test

ASTM C876-15 IS: 516-part 5

Each structural member had a specific number of locations (decided by the area) where the rebound hammer test was performed. Ensuring the test surface is dry and the concrete has been completely dried before performing the test. A grinding tool or stone must chip away and smooth the plaster at the test location. Using a standard stencil, 9 sub points must be marked at each point, with a minimum spacing of 20 mm from the edges and others. The rebound index "Q" at these sub-points will be calculated using the Schmidt hammer. = 7.38440 × ( ×0.03540) (1) According to the data gathered, M20 concrete is the grade used in building construction. After thirty years, the grade of the concrete has degraded in most of the columns and beams, as shown in Table 3. The surface hardness of the columns and the beam is demonstrated by the rebound values of these elements, which range from 21.41 to 58.6, and the concrete's compressive strength, which ranges from 10 N/mm 2 to 58 N/mm 2 . For structural components like columns, it ranges from 10 N/mm 2 to 37 N/mm 2 , and for beams, it ranges from 31 N/mm 2 to 58 N/mm 2 . Each result is measured in terms of Equation (1). To create the numerical model, the above results are used.

Table 3. Rebound hammer values for different columns and beams. Element no. Rebound value (Q)

Compressive strength (fck) N/mm 2

A1 A3 B1

23.5

12 10 37 44 24 58 31 37

21.41

46

b1 b2 b3 b5 b6

50.6 33.3 58.6 41.3 48.1