International Journal of Application or Innovation in Engineering & Management (IJAIEM)
Web Site: www.ijaiem.org Email: editor@ijaiem.org
Volume 3, Issue 9, September 2014
ISSN 2319 – 4847
Non Destructive Testing Techniques – Efficient
Tool for Diagnosis of Aging Effects in Concrete
Structures Exposed to Aggressive Environment
SL Gupta1, Pankaj Sharma2, N.V.Mahure3, Sameer Vyas4, R.P.Pathak5
1-5
Central Soil and Materials Research Station, Hauz Khas, New Delhi - 110016
ABSTRACT
Reinforced concrete structures have the potential to be very durable and capable of withstanding a variety of adverse
environmental conditions. The hydro power projects comprises various concrete structure viz. dam body, foundation galleries,
inspection galleries, power house complex, headrace tunnel, tail race tunnel etc. which are constructed using concrete linings of
different grades. Its durability is determined by various factors viz. aggressivity of surrounding water, temperatures fluctuations,
leaching etc. If the water happens to be soft, it is injurious to the useful life of concrete as it leads to leaching of lime and
corrosion of reinforcement leading to weakening of structure. Once such phenomenon is detected in any such structures a
vigilant periodic monitoring approach becomes mandatory. The suitable remedial measure to be adopted will depend on the
observed degree of deterioration. In this paper effort has been made to diagnose possible deterioration of mass concrete structures
of the hydro projects using non destructive techniques.
Keywords: Non destructive techniques, Durability, Reinforcement, Corrosion, Ultra sonic pulse wave
1. INTRODUCTION
Post construction leaching damages and corrosion of reinforcement are enormous economic liability in any hydro
structure, especially in Himalayan region where water in Rivers is generally soft. The underground inspection galleries
and drainage galleries of dams and power houses are constructed using concrete linings of different grades. Soft water has
a tendency to seep in, cause corrosion of reinforcement [1] and leach out the binding materials from concrete (Fig. 1).
Leaching of binding materials
Corrosion of reinforcement
Fig. 1 Common deteriorations in concrete exposed to soft water
Aging of concrete structures is another factor that will alter the material properties and cause deteriorations (Fig. 2).
Status 2008
Status 2013
a) Developmentof Cracks
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Status 2008
Status 2013
b) Exposure of Reinforcement
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International Journal of Application or Innovation in Engineering & Management (IJAIEM)
Web Site: www.ijaiem.org Email: editor@ijaiem.org
Volume 3, Issue 9, September 2014
ISSN 2319 – 4847
Status 2008
Status 2013
c) Appearance of Brown Patches
Status 2008
Status 2013
d) Enhancement of Leaching Phenomenon
Fig. 2 Aging deteriorations in concrete
In such situations instant diagnosis of problem in insitu conditions becomes mandatory. Diagnosis of the residual
strength of concrete and its constant monitoring will provide useful information for adopting suitable preventive measures
[2, 3, 4]. Using non-destructive tests (NDT) in diagnosis of defects in concrete is an efficient and versatile monitoring
technique which can be safely applied in any field conditions [5, 6]. For assessment of the durability of reinforced
concrete ultrasonic pulse velocity (UPV) technique can be effectively deployed as UPV is influenced by status of concrete
[7, 8]. Diagnosis of the intensity of corrosion and its constant monitoring will provide useful information for adopting
suitable preventive measures [9]. While diagnosis of reinforcement corrosion can be done using Half Cell Potential (HCP)
Testing method which involves measuring the potential of an embedded reinforcing bar relative to a reference half cell
placed on the concrete surface. Both UPV and HCP are NDT method of testing [10]. To monitor the residual strength of
concrete and effect of aging on post construction performance of concrete periodic investigations were carried out at
various locations in different elements of hydroelectric projects. Based on visual status of concrete different test locations
were identified and test points were en-marked for conducting UPV and HCP tests. To assess aging deteriorations UPV
tests were observed initially in year 2008 and subsequently in year 2013. Diagnosis of the intensity of corrosion and its
constant monitoring using Non Destructive Test (NDT) will provide useful information for adopting suitable preventive
measures.
2. METHOD ADOPTED
 Ultrasound Non destructive Test
 Half – Cell Electrical Potential Method to Measure Corrosion of Reinforcement in Concrete [11, 12] (ASTM C 87691)
3. EQUIPMENT USED
3.1 UPV Test
Portable Ultrasound Non destructive Digital Indicator Tester (PUNDIT)
PUNDIT (Fig. 3) was used to observe the time of travel of ultrasonic wave between two fixed points at a specified
distance. Waves are generated through one transducer and received by another transducer.
Fig.3. Portable Ultrasound Non destructive Digital Indicator Tester Equipment (PUNDIT)
3.2 HCP Test
Following equipments were deployed for HCP tests (Fig. 4)
 Micro cover meter- R Meter MKIII
 Half Cell Surveyor- CORMAP II
Volume 3, Issue 9, September 2014
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International Journal of Application or Innovation in Engineering & Management (IJAIEM)
Web Site: www.ijaiem.org Email: editor@ijaiem.org
Volume 3, Issue 9, September 2014
ISSN 2319 – 4847
Micro Cover Meter
Half Cell Surveyor
Fig. 4. Equipments Deployed for Investigation
The micro cover meter has been used to locate the rebar [13]. The concrete surface was examined for the exposed
rebars/or got exposed to get a reference point. Surface was made wet and observation locations were marked on the
surface [14]. The pre -activated Cu-CuSO4 Half Cell was used to take observation. The potential risks of corrosion based
on potential difference readings are presented in Table 1.
Table 1 The potential risks of corrosion based on potential difference readings
Potential difference levels (mv)
less than -500mv
Chance of re-bar being corroded
Visible evidence of Corrosion
-350 to -500 mv
-200 to -350 mv
More than -200 mv
95%
50%
5%
4. OBSERVATIONS
Investigations were carried out at 3 locations selected on the basis of various visual defects (Table 2).
Table 2 Details of Test locations
UPV Test
Location
Site 1
Face
Upstream and Downstream
Site 2
Site 3
Upstream and Downstream
Upstream and Downstream
HCP Test
Site 4
Upstream
Site 5
Downstream
Site 6
Upstream
Site 7
Downstream
Site 8
Upstream
5. RESULT AND DISCUSSION
a. Ultrasonic Pulse Velocity Test
The results of UPV recorded in year 2008 and year 2013 for scanned area of site 1 on upstream face of gallery is
resented in Fig. 5. Similar scanning was performed for downstream face also. For site 2 and site 3 also scanning was
Volume 3, Issue 9, September 2014
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International Journal of Application or Innovation in Engineering & Management (IJAIEM)
Web Site: www.ijaiem.org Email: editor@ijaiem.org
Volume 3, Issue 9, September 2014
ISSN 2319 – 4847
carried out for both faces. Based on the observed UPV the overall status of concrete in year 2008 and year 2013 is
presented in figure 6 for site 1, 2 and 3 respectively.
Fig.5 UPV on Site 1 - Upstream Face
In Year 2008
In Year 2013
Upstream Face
In Year 2008
In Year 2013
Downstream Face
Site 1
In Year 2008
In Year 2013
Upstream Face
In Year 2008
In Year 2013
Downstream Face
Site 2
In Year 2008
In Year 2013
Upstream Face
In Year 2008
In Year 2013
Downstream Face
Site 3
Fig. 6 Status of Concrete on Upstream and Downstream Face of Location A, B and C
Volume 3, Issue 9, September 2014
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International Journal of Application or Innovation in Engineering & Management (IJAIEM)
Web Site: www.ijaiem.org Email: editor@ijaiem.org
Volume 3, Issue 9, September 2014
ISSN 2319 – 4847
On visualising Fig. 6 it is clearly evident that in the scanned area on the upstream as well as downstream face concrete
has undergone deterioration.
5.2 Half – Cell Electrical Potential
Investigation were carried out at certain fixed locations selected on the basis of heavy leaching patches (Table 2).
Categories of corrosion activity are depicted in Table 3.The observed values for the tests done at location site 4 to 8 are
presented in fig. 7 and 8 in the form of contour map for site 4 and pie chart [13, 15, 16] for site 4-8.
Table 3 Showing the categories of Corrosion activity
A&B
90% chance corrosion is occurring in this area
C&D
E –G
Corrosion activity over this area is uncertain
90% chance that no corrosion activity is present over this area
Fig. 7 Contour Map Showing Corrosion Status of Scanned Area
Site 4
Site 7
Site 5
Site 6
Site 8
Fig. 8 Pie Chart Showing Degree of Corrosion in Scanned Areas of Site 4-8
6. CONCLUSION
Interactions of concrete with persistent prevailing environmental conditions and aging will alter its material properties
and cause deteriorations. Imaging the status of concrete using ultrasonic pulse velocity technique clearly reveal the effect
of aggressive hydro-environment causing aging deteriorations of concrete in a period of almost 5 years. The test
Volume 3, Issue 9, September 2014
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International Journal of Application or Innovation in Engineering & Management (IJAIEM)
Web Site: www.ijaiem.org Email: editor@ijaiem.org
Volume 3, Issue 9, September 2014
ISSN 2319 – 4847
observations using Half Cell Potential Test method of corrosion monitoring test conducted at five locations shows signs of
initiation of corrosion activity. Diagnosis of the residual strength of aging concrete necessitates the periodic health
monitoring.
7. ACKNOWLEDGEMENT
The authors extend their sincere thanks to Director CSMRS for his constant inspiration. We also extend our sincere
gratitude to Sh. AK.Rustagi and Sh. Devender Singh of CSMRS for their valuable efforts. We also extend our sincere
gratitude to all the authors whose publications provided us directional information from time to time.
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[14] Stratfull, R. F., Jurkovich, and W. J., Spellman, D. L., “Corrosion Testing of Bridge Decks,” Highway Research
Record 539, Washington, D. C., Transportation Research Board (1975).
[15] Clemena, G. G., “Benefits of Measuring Half-cell Potentials and Rebar Corrosion Rates in Condition Surveys of
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AUTHOR
SL Gupta received the B.E in Civil Engineering from Thapar Institute of Engg. & Technology in 1982 and
M.Tech in Rock Mechanics from IIT, New Delhi in 1988. He is working in Central Soil & Materials Research
Station, Ministry of Water Resources, RD and GR, New Delhi, India for last 29 years in the field of
Geotechnical and Concrete Technology. He had been involved in field and Laboratory investigations of river
valley projects in hydropower sector and published number of Research papers.
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