1. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308
(Print), ISSN 0976 – 6316(Online) Volume 4, Issue 4, July-August (2013), © IAEME
21
NON- DESTRUCTIVE EVALUATION OF IN-SITU STRENGTH OF
HIGH STRENGTH CONCRETE STRUCTURES
Dr. K.V.Ramana Reddy
Professor in Civil Engineering,
Mahatma Gandhi Institute of Technology, Hyderabad- 500075, India
ABSTRACT
This paper deals with the evaluation of in-situ strength of high strength concrete (HSC)
structures using Non Destructive Evaluation (NDE) techniques like Ultrasonic Pulse Velocity (UPV)
Rebound Hammer test and combined methods. An experimental research was carried out, involving
both destructive and non destructive methods applied to different concrete mixes, with compressive
strength varying from 50 up to 130 MPa. Both cubic and cylindrical standard specimens and bigger
blocks were cast with water cement ratio of 0.30. Just before conducting destructive test, UPV and
Rebound Hammer tests were conducted on the same cubes as per IS 13311 (Part-1&2). The results
of all the tests were utilized to obtain correlation curves between destructive and non-destructive
parameters. For all the experimental values, design curves were drawn for correlating the
compressive strength with the UPV and Rebound Number. Regression analysis was performed for
assessment of in-situ strength of high strength concrete structures. Cores were also taken from the
columns of the buildings for compressive strength. The results shows NDE techniques like pulse
velocity, surface hardness and combined methods are suitable for evaluation of compressive strength
of high strength concrete structures up to compressive strength of 130 MPa.
Keywords: Concrete, HSC, Non-Destructive Evaluation Techniques, Combined methods.
I. INTRODUCTION
Non-Destructive Testing (NDT) is defined as one that does not damage or impair the
intended performance of the structural element or member being tested. NDT methods offer simple,
quick and reliable results if proper procedure and appropriate test programme are defined and
implemented. NDT is a good tool to survey uniformity in quality of concrete, for damage
assessment, to estimate current engineering properties of concrete-usually the compressive strength
(Chandrakant B.Shah, 2002). It has been defined as comprising those test methods used to examine
object, material or system without impairing its future usefulness (N.J.Carino, 1994). Strictly
speaking, this definition of nondestructive testing does include noninvasive medical diagnostics.
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2. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308
(Print), ISSN 0976 – 6316(Online) Volume 4, Issue 4, July-August (2013), © IAEME
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Ultrasound, X-rays and endoscopes are used for both medical testing and industrial testing. The term
is generally applied to non-medical investigations of material integrity. A number of other
technologies - for instance, radio astronomy, voltage and amperage measurement and rheometry
(flow measurement) - are nondestructive but are not used to evaluate material properties specifically.
Of the various NDT, surface hardness method-Rebound hammer (RH) and ultrasonic pulse
velocity (UPV) method are truly non-destructive and the others such as pull out test may cause some
damage to the concrete. The demands on integrity assessment and life management of ageing
infrastructure such as old buildings, bridges and dams are providing continuous impetus for
development of reliable testing methods. These methods not only provide information on the
necessity for repairs, but also frequency of future inspections/repairs as they sense damages at micro
level (Francois Buyle-Bodin, 2003). However, while assessing the capabilities and limitations of
various non-destructive testing (NDT) and evaluation techniques that can be applied to concrete
structures, it has been fount that, in many cases, the data obtained are qualitative rather than
quantitative and hence efforts are being made to overcome this limitation.
The evaluation by non destructive methods of the actual compressive strength of concrete in
existing structures is based on empirical relations between strength and non destructive parameters
(K.V.Ramana Reddy, 2008). . The most commonly used testing methods are rebound hammer, pulse
velocity, microcoring and combined methods. The validity of the above mentioned relations is
actually limited to normal strength concrete, up to 50 MPa. HSC has been employed in recent years,
with compressive strength up to 130 MPa and over. The relations used to evaluate the compressive
strength of normal concrete by non destructive tests may be no longer valid for HSC. This
experimental research is aimed to verify the possibility of applying the known NDT methods to
HSC, to state the limits of the testing equipment available and to extend the existing relations, or
determine new ones between no destructive parameters and compressive strength of high strength
concrete.
II. EXPERIMENTAL PROGRAMME
Materials: The materials used in the present investigations are summarized below. Throughout the
investigation, the materials have been procured from the same respective sources for maintaining
uniformity in all the cubes cast.
Cement: Ordinary Portland Cement of 43 grade has been procured confirming to IS:8112 and is
used in the present investigation.
Fine Aggregate: The locally available sand is used as fine aggregate. The local sand free from clay,
silt and organic impurities and confirming to IS:383-1970 is used as fine aggregate.
Coarse Aggregate: Machine crushed well graded angular granite aggregate of maximum size 20
mm free from impurities such as dust, clay particles and organic matter confirming to IS:383-1970 is
used as coarse aggregate.
Water: The locally available potable water, which is free from concentration of acids and organic
substances, is used for mixing the concrete and curing the specimens.
Admixture: A new superplasticiser based on carboxylic ether polymer with long side chains
(Glenium 51 of M/s. MAC S.p.A., Treviso, Italy) was used.
Flyash: Class F flyash from thermal power plants
Mix Design: In the present work, mix design is carried out by Indian Standard recommended method
IS 10262:1982 and also as per the procedure laid down in IS: 456: 2000. The quantities of dry
materials used for the grades to obtain one cum of compacted concrete have shown in the Table.1.

3. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308
(Print), ISSN 0976 – 6316(Online) Volume 4, Issue 4, July-August (2013), © IAEME
23
Table. 1 Quantities of materials
S.
No
Grade of
Concrete
Proportion of
Mix
Cement
(kg)
Fine
Aggregate
(kg)
Coarse
Aggregate
(kg)
Flyash
(kg)
Super
Plasticizer
(cc)
1 M 40 1:1.22: 2.14 410 613 1135 - 1200
2 M 50 1:1.12: 2.09 430 642 1176 121 1350
3 M 60 1:1.02: 2.02 480 633 1186 164 1560
4 M 70 1:0.90: 1.82 510 426 1242 198 1852
5 M 80 1:0.78: 1.65 530 385 1341 209 1964
6 M 90 1:0.72: 1.45 540 346 1369 245 2052
7 M 100 1:1.65: 1.42 550 315 1405 269 2126
One hundred and ten cubes were cast and results obtained at ages of 7, 14, 28, and 56 days. Non-
destructive tests were conducted viz rebound hammer, ultrasonic pulse velocity techniques and
combined method. On the same specimens compression test was conducted on digital compression
testing machine of 3000 kN capacity.
III. CORRELATION CURVES
The experimental work is carried out on plain concrete of various grades form 50 MPa to
130MPa. Concrete cubes of size 150x150x150mm were cast with W/C ratio of 0.3 and cured and
tested for 7,14,28,56 days compressive strength. Before testing for compressive strength, Ultrasonic
Pulse Velocity (UPV) Rebound Hammer and combined methods for assessment of strength of
concrete. All these results used to obtain correlation curves between destructive and non-destructive
parameters. For all the experimental values, correlation curves were drawn between compressive
strength and NDE techniques and were presented in Figures.1, 2 and 3. Some of the photographs
were also presented from plate numbers1 to 4. Regression analysis was also made to correlate the
values from one another.
Fig. 1 Correlation between compressive strength and UPV Values
y = 83.57x - 299.3
R² = 0.990
40
50
60
70
80
90
100
110
120
130
140
4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 5 5.1 5.2
ComprtessiveStrengthinMpa
UPV Values in km/s

4. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308
(Print), ISSN 0976 – 6316(Online) Volume 4, Issue 4, July-August (2013), © IAEME
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Fig. 2 Correlation between compressive strength and rebound number
Fig. 3 Equal strengthg lines based on linear regression analysis of data obtained from combined
method of rebound hammer and ultrsonic pulse velocity
y = 4.443x - 114.4
R² = 0.997
35
45
55
65
75
85
95
105
115
125
135
30 35 40 45 50 55 60
CompressivestrengthinMpa
Rebound number
y = 6.492x + 7.935
R² = 0.935
20
24
28
32
36
40
44
48
52
2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1
ReboundNumber
Pulse Velocity (km/s)
Fig. 3 Equal strengthg lines based on linear regression analysis of data obtained
from combined method of rebound hammer and ultrsonic pulse velocity
15-24.9 MPa
25-34.9 MPa
35-44.9 MPa
45-54.9 MPa
55-64.9 MPa
65-70 MPa
Linear (65-70 MPa)

5. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308
(Print), ISSN 0976 – 6316(Online) Volume 4, Issue 4, July-August (2013), © IAEME
25
From the Design curves, mathematical equations are formulated and is shown in Table:2.
Table:2 Mathematical Equations for compressive strength from NDE techniques
Sl.
No
NDE technique Equation Regression
co-efficient
1 Ultrasonic Pulse Velocity fc = 83.57V-299.3 R2
=0.990
2. Rebound Hammer fc = 4.443R-114.4 R2
=0.997
3. Combined Method fc =1.24R+0.058V4
-24.1 R2
=0.935
Note: units of V is km/s
Plate 1: Rebound Hammer Test on a
Bridge pier
Plate 2: UPV Test on a RCC slab
Plate 3: Core Extraction from
Bridge PierPlate 4 : Rebound Hammer test on slabs

6. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308
(Print), ISSN 0976 – 6316(Online) Volume 4, Issue 4, July-August (2013), © IAEME
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IV. DISCUSSION OF TEST RESULTS
To validate the above obtained mathematical equations from the Design curves, ultrasonic
pulse velocity and rebound hammer tests were conducted as per the procedures laid down in IS-
13311 (Part1&2),on various bridges and flyovers in and around Hyderabad and also on the gas
turbine foundations of Gautami Power Project, Samarlakota, India. Ten concrete cores of 55 mm
diameter were extracted from hardened concrete (beams, columns) on which UPV and RH tests have
been conducted for evaluating the actual in -situ strength of the structures. These concrete core
samples were used to determine the density also. The parameters which influence the measured
compressive strength are size of the specimen i.e diameter as well as length to diameter ratio,
direction of drilling, method of capping, the effect of drilling operations, moisture conditions of the
core at the time of testing as per IS:516. The equivalent cube strength of concrete are presented in the
Table:3 for comparison. A curve was drawn between predicted strength by mathematical equations
and experimental strength from cores taken in the field and is shown in Fig.4. On comparison, it is
found that there is about 10% variation in these values.
Table: 3 Statistically analyzed data of UPV and RH tests
Item
Pair
of
UPV
spots
Ultrasonic Pulse
Velocity
No.
of
Rebo-
-und
Num-
bers
Rebound Number
(RN)
Qualityofconc.
Est.strengthfromUPV(Mpa)
Est.strengthfromRH(Mpa)
Avg.Est.strength
(Mpa)
Exp.Strengthfromcores(Mpa)
Mean
Velo-
city
(km/s)
Std.
Devi
-
ation
(km/
s)
Co-
eff
of
vari--
ation
Mean
RN
Std.
Devi-
ation
Co-
eff
of
Vari-
ation
OB1 75 3.58 161 4.6 400 27.42 4.85 17.5 G 31.23 32.2 31.71 33.5
OB2 52 3.75 213 6.7 126 28.4 4.13 14.20 G 35.25 36.5 35.88 38.45
NB1 64 4.25 375 8.10 370 32.45 4.92 17.64 G 41.1 43.2 42.15 45.95
NB2 15 4.34 392 7.90 85 31.52 5.10 16.49 G 38.8 38.2 38.5 41.9
B1 52 4.85 521 6.40 42 145 4.15 18.92 E 78.5 80.2 79.35 86.95
B2 46 4.99 463 6.87 36 151 5.12 17.98 E 86.1 85.6 85.85 93.25
F 36 4.98 502 5.8 24 148 4.86 21.40 E 85.6 87.4 86.5 93.95
GT1 15 5.25 124 5.10 40 39.5 4.90 15.20 E 109.5 110.5 110.0 119.5
GT2 10 5.15 201 8.10 60 43.2 3.70 17.15 E 102.5 100.2 101.4 110.6
OB: Old Building NB: New building GT: Gas Turbine Foundations
B: Bridge F: Flyover G: Good E: Excellent

7. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308
(Print), ISSN 0976 – 6316(Online) Volume 4, Issue 4, July-August (2013), © IAEME
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Fig. 4 Comparison between Experimental and predicted in- situ strengths
V. CONCLUSIONS
1. The in-situ strength of concrete obtained from the destructive testing is about 10% more than
that predicted based on the design curves and mathematical equations presented in this paper.
2. Combined Method of UPV and Rebound Hammer technique is found to be more effective for
validating the in - situ strength of high strength concrete structures.
VI. ACKNOWLEDGEMENTS
Vasavi College of Engineering and Civil-Aid Technoclinic Private Limited, Hyderabad, are
greatly acknowledged for extending the facilities and co- operation for conducting the experiments.
VII. REFERENCES
[1] Chandrakant B.Shah ,2002, “NDT of earthquake-affected structures in Gujarat: Case study”
The Indian Concrete Journal
[2] Francois Buyle-Bodin, 2003,”Contribution of coupling non-destructive methods for diagnosis
of concrete structures”, International symposium (NDTCE-2003),Japan
[3] Konstantin Kovier and Isaak Schamban, 1999, “Mathematical Methods of Experimental
Design in Nondestructive Testing”, International Simposium on NDT Contribution to the
Infrastructure Safety Systems, Brazil
[4] T.Jayakumar 2003, “Integrity assessment of concrete structures using Non Destructive
Evaluatioin Techniques”, INCONTEST- 2003, India
[5] Giovanni Pascale,2000, “ Evaluation of Actual Compressive Strength of High Strength
Concrete by NDT” Rama2000, Italy
[6] K.V.Ramana Reddy, 2007, “ Assessment of Strength of Concrete By Non-Destructive Testing
Techniques” International conference on Fast track construction of Bridges (IIBE),
Hyderabad, India
40
60
80
100
120
140
40 55 70 85 100 115 130 145
Estimatedstrength(Mpa)
Prdicted strength (MPa)
Predicted Strength
(Mpa)
Experimental
Strength(MPa)

8. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308
(Print), ISSN 0976 – 6316(Online) Volume 4, Issue 4, July-August (2013), © IAEME
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[7] Samarin.A.(1984) “Determination of in-situ concrete strength; rapidly and confidently by non-
destructive testing” ACI, Detroit
[8] Malhotra.V.M,(2001): Testing of in-situ concrete: Non-Destructive Methods
[9] K.V.Ramana Reddy, 2008, “ Design curves and mathematical equations for in-situ strength of
concrete structures by NDE Techniques” International conference on Advances in concrete
construction (ICACC- 2008) VCE, Hyderabad, India
[10] Giovanni Pascale ( 2000): “Evaluation of Actual Compressive Strength of High Strength
Concrete by NDT” Roma 2000.
[11] Dr. Debasish Basak and Bubun Das, “In-Situ Nondestructive Assessment of a Winder Rope of
a Coal Mine”, International Journal of Mechanical Engineering & Technology (IJMET),
Volume 3, Issue 2, 2012, pp. 416 - 421, ISSN Print: 0976 – 6340, ISSN Online: 0976 – 6359.
[12] D.B.Mohite and S.B.Shinde, “Experimental Investigation on Effect of Different Shaped Steel
Fibers on Flexural Strength of High Strength Concrete”, International Journal of Civil
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