NON DESTRUCTIVE TESTING OF BRIDGE PIER- A CASE STUDY
Abstract
This paper reviews various NDT methods available and presents a case study related to the strength evaluation of existing bridge pier. The assessment of quality and strength is made by correlating the NDT observations with core tests. The assessment involves the core tests, Rebound hammer tests and Ultrasonic pulse velocity tests
Introduction
It is often necessary to test concrete structures after the concrete has hardened to determine whether the structure is suitable for its designed use. Ideally such testing should be done without damaging the concrete. The tests available for testing concrete range from the completely non-destructive, where there is no damage to the concrete, through those where the concrete surface is slightly damaged, to partially destructive tests, such as core tests and pullout and pull off tests, where the surface has to be repaired after the test. The range of properties that can be assessed using non-destructive tests and partially destructive tests is quite large and includes such fundamental parameters as density, elastic modulus and strength as well as surface hardness and surface absorption, and reinforcement location, size and distance from the surface. In some cases it is also possible to check the quality of workmanship and structural integrity by the ability to detect voids, cracking and delamination. Non-destructive testing can be applied to both old and new structures. For new structures, the principal applications are likely to be for quality control or the resolution of doubts about the quality of materials or construction. The testing of existing structures is usually related to an assessment of structural integrity or adequacy. In either case, if destructive testing alone is used, for instance, by removing cores for compression testing, the cost of coring and testing may only allow a relatively small number XX XXXXX to be XXXXXXX out on a XXXXX XXXXXXXXX XXXXX XXX be misleading. Non-XXXXXXXXXXX XXXXXXX can be XXXX in XXXXX situations XX a preliminary XX subsequent XXXXXX.
XXXXXXX situations XXXXX non-XXXXXXXXXXX XXXXXXX XXX be useful are, as XXXXXXX:
1. XXXXXXX control of pre-cast XXXXX or construction in situ
X. XXXXXXXX uncertainties XXXXX XXX acceptability XX XXX XXXXXXXX supplied owing to XXXXXXXX XXX-compliance with XXXXXXXXXXXXX
X. Confirming or XXXXXXXX doubt concerning the XXXXXXXXXXX involved in batching,
4. mixing, placing, XXXXXXXXXX or XXXXXX of concrete
X. XXXXXXXXXX of XXXXXXXX XXXXXXXXXXX in XXXXXXXX to XXXXXXXX XXXXXXX, cessation of
6. curing, XXXXXXXXXXXX, XXXX XXXXXXXXXXX or similar purpose
7. Location XXX XXXXXXXXXXXXX XX the XXXXXX of XXXXXX, voids, honeycombing and
similar XXXXXXX within a XXXXXXXX XXXXXXXXX
8. XXXXXXXXXXX the XXXXXXXX uniformity, possibly XXXXXXXXXXX XX core cutting, load testing or other XXXX expensive or disruptive tests
9. XXXXXXXXXXX the position, XXXXXXXX or XXXXXXXXX XX reinforcement
10. Increasing XXX XXXXXXXXXX level of a smaller XXXXXX of XXXXXXXXXXX tests
Basic Methods for XXX of Concrete XXXXXXXXXX
The following XXXXXXX, XXXX some typical applications, have XXXX XXXX for XXX NDT of concrete (XXXXXX, XXXX):
Visual inspection, which is an essential XXXXXXXXX XX XXX intended XXX-destructive XXXX XX XXXXXXXXX XXX possible cause(s) XX damage to a XXXXXXXX structure XXX hence identify which of XXX XXXXXXX NDT methods available could be XXXX useful XXX XXX further investigation XX XXX problem.Half-cell XXXXXXXXXX potential method, XXXX XX XXXXXX XXX XXXXXXXXX XXXXXXXXX of XXXXXXXXXXX bars in XXXXXXXXXXXXXXX/rebound hammer XXXX, XXXX to evaluate the surface hardness XX XXXXXXXX.XXXXXXXXXXX XXXXX XXXXXXXXXXX test, used XX determine XXXXXXX moisture has XXXXXXX the depth XX XXX XXXXXXXXXXX XXXX XXX hence XXXXXXXXX may be XXXXXXXXX.XXXXXXXXXXXX XXXX, used XX measure the XXXX XX water through the concrete.XXXXXXXXXXX XXXXXXXXXX or Windsor XXXXX XXXX, XXXX XX XXXXXXX the XXXXXXX XXXXXXXX XXX XXXXX XXX strength of XXX surface and near XXXXXXX XXXXXX of XXX XXXXXXXX.Covermeter XXXXXXX, XXXX to measure the XXXXXXXX XX steel XXXXXXXXXXX XXXX XXXXXXX the XXXXXXX XX XXX concrete and also possibly XX measure XXX XXXXXXXX of the reinforcing bars.XXXXXXXXXXXX XXXXXXX, used XX detect XXXXX in XXX XXXXXXXX XXX XXX position XX stressing XXXXXXXXXXXXXXX pulse velocity XXXXXXX, XXXXXX used XX XXXXXXX the sound velocity XX the concrete and hence the compressive strength of the XXXXXXXXXXXXX XXXXXXX XXXXX an instrumented hammer XXXXXXXXX XXXX sonic echo XXX transmission methods.Impact XXXX XXXXXXX, used to detect XXXXX, delamination XXX XXXXX XXXXXXXXX in concreteXXXXXX XXXXXXXXXXX XXXXX or XXXXXXX radar testing, used XX XXXXXX XXX position XX XXXXXXXXXXX XXXX or stressing ducts.XXXXXXXX thermography, used to XXXXXX voids, XXXXXXXXXXXX and XXXXX XXXXXXXXX in concrete and XXXX detect water XXXXX points in buildings.
Schmidt Rebound XXXXXX XXXX
XXX Schmidt XXXXXXX XXXXXX is principally a XXXXXXX hardness XXXXXX. It works on XXX principle XXXX XXX rebound of an elastic mass depends XX the XXXXXXXX XX the XXXXXXX XXXXXXX which XXX mass XXXXXXXX (XX 13311 (XXXX-2) XXXX). There XX little apparent XXXXXXXXXXX relationship XXXXXXX XXX strength of concrete and XXX XXXXXXX number XX XXX hammer. However, XXXXXX limits, XXXXXXXXX correlations have been established between strength XXXXXXXXXX and the rebound XXXXXX.
Ultrosonic Pulse XXXXXXXX XXXX
A XXXXX of longitudinal XXXXXXXXXX is produced XX an electro-acoustical XXXXXXXXXX, whichis held in XXXXXXX XXXX one surface XX XXX concrete under test. XXXX the pulse XXXXXXXXX XX XXXXXXXXXXX into the XXXXXXXX XXXX XXX transducer using a XXXXXX XXXXXXXX material such XX grease or cellulose paste, it undergoes XXXXXXXX XXXXXXXXXXX XX XXX boundaries XX the different material XXXXXX within the XXXXXXXX. X XXXXXXX XXXXXX of stress waves XXXXXXXX, XXXXX XXXXXXX both longitudinal and shear XXXXX, XXX propagates XXXXXXX the XXXXXXXX. The first waves XX reach XXX XXXXXXXXX transducer XXX XXX XXXXXXXXXXXX XXXXX, XXXXX XXX XXXXXXXXX XXXX an XXXXXXXXXX XXXXXX by a second transducer. XXXXXXXXXX timing XXXXXXXX XXXXXX XXX transit XXXX T of XXX XXXXX XX be XXXXXXXX. XXXXXXXXXXXX pulse velocity (in XX/s or m/s) XX given by:
v = X / T
XXXXX v XX the XXXXXXXXXXXX XXXXX velocity, L is XXX XXXX XXXXXX, T is the time XXXXX by the pulse XX XXXXXXXX XXXX XXXXXX. The equipment XXXXXXXX XXXXXXXXXXX XX an electrical pulse XXXXXXXXX, a XXXX XX transducers, an XXXXXXXXX and an electronic XXXXXX device for measuring the XXXX interval between XXX initiation XX a XXXXX XXXXXXXXX at the XXXXXXXXXXXX transducer XXX its XXXXXXX XX the XXXXXXXXX transducer. XXX XXXXX of XXXXXXXXXX XXXXXX apparatus XXX display XXX XXXXXXXXX, XXX XX which XXXX a XXXXXXX XXX XXXX XX which the received pulse XX XXXXXXXXX in XXXXXXXX XX a XXXXXXXX XXXX XXXXX, the XXXXX uses an XXXXXXXX XXXXX with a XXXXXX reading XXXXXXX display. XXX XXXXXXXXX XXXXXX have XXX XXXXXXXXX characteristics. It should be XXXXXXX XX XXXXXXXXX transit time over path lengths XXXXXXX from XXXXX XXX mm to XXX XXXXXXX thickness XX XX XXXXXXXXX to an XXXXXXXX XX ±X%. Generally the XXXXXXXXXXX XXXX XXXXXX be in the range of 20 XX XXX XXX XXXXXXXX frequencies as low XX 10 XXX may XX XXXX XXX XXXX long concrete XXXX XXXXXXX XXX as high XX X XXX XXX XXXXXXX and grouts or for short XXXX lengths. High XXXXXXXXX pulses XXXX a XXXX defined onset but, as they XXXX through the concrete, XXXXXX XXXXXXXXXX XXXX XXXXXXX than XXXXXX XX lower XXXXXXXXX. It is XXXXXXXXX preferable XX use XXXX frequency transducers XXX XXXXX path XXXXXXX and XXX XXXXXXXXX XXXXXXXXXXX for XXXX path lengths. XXXXXXXXXXX XXXX a frequency of 50 kHz to 60 XXX XXX suitable XXX most common applications. XXXXX XXXXXXXX XXXXXXXXXXXX XXXX on concrete XXXXXXXXXX may XX XXXX for quality control XXXXXXXX. In comparison XXXX mechanical XXXXX XX XXXXXXX XXXXXXX XXXX XX XXXXX or XXXXXXXXX, pulse XXXXXXXX XXXXXXXXXXXX have the advantage that XXXX relate XXXXXXXX XX XXX concrete in the XXXXXXXXX XXXXXX XXXX to XXXXXXX, XXXXX XXX XXX XX XXXXXX XXXXX XXXXXXXXXXXXXX XX the concrete in situ
XXXX Test
In XXXX structural XXXXXXXXXXXXXX or diagnoses XXXXXXXXXX XX core samples XX Unavoidable XXX XXXXX essential. XXXXX XXX usually XXXXXXXXX by XXXXXXXX using a diamond XXXXXX XXXX XXXXXX XXXXXX XXXX XXXXX. XXXXXX XXXXXXX, XXX example, XXX XX XXXXXXX,
XXXXXXXX and delamination, XXX also XXXXXXXX retrieved for XXXXXXX XXXXXXXX XX these XXXXXXX may XXXXXXX XXXXXXXXXX XXXXXXXX XX to XXX XXXXX of XXXXXXXX. The XXXXXXXXX XX XXX XXXXXXXXX for XXXXXXXXXX XX XXXX XXXXXXX is XXXX XXXXX XXX-destructive testing which XXX XXXX XXXXXXXX XX XXX XXXX suitable XXXXXXXX areas. For instance, a covermeter XXX XX used to ensure XXXXX are XX XXXXXXXXXXX bars where the core is XX be taken; or the XXXXXXXXXX pulse velocity test XXX XX used to establish the areas XX XXXXXXX XXX XXXXXXX XXXXX velocity that could XXXXXXXX the XXXXXXX and lowest compressive XXXXXXXX areas in the XXXXXXXXX.
Moreover, using non-destructive XXXXX, XXX XXXXXX of cores that XXXX to be taken XXX be reduced or minimized. XXXX XX XXXXX an XXXXXXXXX since XXXXXX is XXXXXXXXXX XXXXXX XX XXXXX destructive. Also the cost XX extracting XXXXX XX XXXXX high and the XXXXXX to XXX concrete is XXXXXX. XXX extracted cores can be XXXXXXXXX XX a series XX XXXXX and serve XXXXXXXX XXXXXXXXX such as:
confirming XXX XXXXXXXX XX XXX non-XXXXXXXXXXX testidentifying the presence XX XXXXXXXXXXX matter in the XXXXXXXXXXXXXXXXXXXX the XXXXXXXX XX the XXXXXXXX for XXXXXX XXXXXXXXpredicting the potential XXXXXXXXXX of XXX concreteXXXXXXXXXX XXX XXX composition of the XXXXXXXX XXX dispute resolution
Case XXXXX
In a X-XXXX girder bridge, constructed across a XXXXX in India, it was reported XXXX the XXXXXXXX of concrete in XXX XX XXX XXXXX could XXX be XXXXXXXX in XXX testing XX XXXXXXXXXXXXX XXXXXXXX XXXXX. Further the core samples XXXXXXXXX XXXX different XXXXXXXX values. XX this connection it XXX recommended to XXXX the grouting XX the XXXX. After the grouting carried out in accordance XXXX XXXXXXXX procedure XXX Non destructive XXXX XXX carried-out XXXXX XXXXXXX XXXXXX XXX Ultrasonic XXXXX XXXXXXXX tester. XXXXXXX XX quantify the strength XX XXXXXXXX XXXXX core samples were XXXX XXXXXXXXX for XXXXXXX.
XXXXXXXXXXXX
X. The XXXXXXXX Core XXXX results XXXXXXXX XXXX XXX Average XXXXXXXXXXX XXXXXXXX XX
Concrete is 32.91MPa. Also it is XXXXXXXX XXXX XXXXXXXXXX core XXXX XXXXXX (which are XXXXXX ±20% of average XXXXX) are XXXXX 20MPa XXX satisfy XXX strength XXXXXXXXXXX of XXX XXXXX concrete.
2. The XXXXXXX Ultrasonic Pulse velocity XXXXXXXX is 3.XXX XX/sec. XXXXXXX XXXX XX the
USP XXXXX is less than 3kM/sec. Also XXX XXXXXXXXX in individual XXX values is
XXXXXX ±10% of XXXXXXX.XXXX indicate, XX XXX XXX guidelines laid in IS-XXXXX-XXXX 1-
XXXX, that the XXXXXXX of XXXXXXXX in terms XX uniformity, incidence or XXXXXXX XX
XXXXX, cracks and segregation, XXX level of XXXXXXXXXXX XXXXXXXX may be
X. XXX Average Rebound XXXXX is XX.XX and XXX XXXXXXXXX in individual values XX XXXXXX
±XX%. XXX Concrete compressive XXXXXXXX as interpreted from XXX rebound XXXXX is
24.865 MPa, which satisfies XXX requirement of XXX XXXXX concrete.
XXXXXXXXXX XXXXXXX
The various XXX techniques XXX very useful in estimating the quality XXX XXXXXXXX
of XXXXXXXX concrete structures. The XXXX XXXXX presented XXXX illustrates XXX correlation
XX XXXXXXXXXXX XXX NDT results in XXX XXXXXXXXXXXXX XXXXXXXXXX XX structure XXXXXXXXX
XXXXXXXXXX
IS XXXXX (Part-X)-(1992). Methods XX Non XXXXXXXXXXX Testing of XXXXXXXX: XXXX-1: Ultrasonic Pulse
Velocity
IS XXXXX (Part-2) (XXXX) XXXXXXX XX XXX Destructive Testing XX XXXXXXXX: XXXX-2: XXXXXXX XXXXXX
XX XXX XXXX. Code XX XXXXXXXX for Plain and XXXXXXXXXX XXXXXXXX,
XXXXXX.MS (XXXX).XXXXXXXX Technology.S.Chand& Company, XXX XXXXX.
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