final year batch 4
TRANSCRIPT
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BATCH MEMBERS :
BINITHA.B (10610103004)POOJA RAMDAS (10610103017)PREETHI.P (10610103019)RADHA.S (10610103305)
GUIDED BY :
Mrs. F. DEVAIRAKKAM RENU M.E.,Assistant Professor
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NON-DESTRUCTIVE TESTING (NDT):
Non destructive testing is a technique for checking
structural integrity after concrete hardening
without or partial damage to the concrete.
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OBJECTIVE:
To Study the use, methodology & applicability of
non destructive testing methods to monitor the
structural health.
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SCOPE:
Suggest the methodology to be followed &
applicability of non destructive testing.
Automatic interpretation of data from NDT, with the
goal of detecting flaws accurately and efficiently.
To propose retrofitting techniques for structures
failing in this kind of testing.
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Why NDT? Strength on concrete depends on material, proper mixing
& also workmanship at the time of placing
Conventional methods of testing of concrete does provide
solution to assess actual strength or internal structure after
hardening of concrete
In some cases, it required to assess of concrete damaged
due to fire or any other natural calamity due judge the
condition of structure
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Where to use NDT? Quality control of Construction , in situ
Confirming Workmanship
determining the position, quantity or condition ofreinforcement
Location of Cracks/Joints/Honeycombing
Confirming or locating suspected deterioration ofconcrete resulting from such factors as overloading,fatigue, external or internal chemical attack or change,fire, explosion, environmental effect.
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Various methods of NDT : Schmidt Rebound Hammer Test.
Ultrasonic Pulse Velocity- UPV Test.
Core Extraction for Compressive Strength Test.
Carbonation depth measurement Test.
Concrete Cover Measurement Test.
Half-cell potentiometer Test.
Chloride content Test.
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1) REBOUND HAMMER TEST
This test is performed by a Schmidt hammer,
also known as a Swiss hammer or a rebound
hammer.
It was invented by Ernst Schmidt, a Swiss
engineer in 1948.
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Rebound Hammer Test
StrengthSurface
Hardness
• Reference code: IS 13311 (Part 2) – 1992.
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Mechanism of Rebound Hammer
It Consist of a spring control hammer that slides on a plunger within a tubular housing. When the plunger is pressed against the surface of the concrete, the mass rebound from the plunger. It reacts against the force of spring. The Distance travelled by the mass, is called rebound number.
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Principle : The rebound of an elastic mass depends on the hardness of the surface against which mass strikes.
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The test is performed on a column of size 350mmx290mm to determine its hardness. The rebound numbers are obtained as below:
Point Rebound
number
Average rebound
number
1. 36
40
32
34
36
40
36.33
2. 42
42
36
38
38
42
39.66
3. 38
48
30
42
40
42
40
4. 44
36
46
36
40
40
40.33
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5. 40
44
44
46
44
42
43.33
6. 44
46
38
44
42
42
42.66
7. 42
36
44
44
32
36
39
8. 42
42
40
38
40
42
40.66
9. 30
32
34
30
32
30
31.33
10. 34
32
38
40
32
32
34.66
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11. 30
36
30
30
30
32
31.33
12. 32
34
32
32
44
30
34
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The test is performed on a cube of size 150mmx150mmx150mm to determine its hardness. The rebound numbers are obtained as below:
Cube
grade
M25
Point 1 2 3 4 5 6
Rebound
number
32
30
24
28
24
26
30
32
26
30
26
28
32
26
30
26
28
30
30
28
24
32
28
28
24
30
32
26
24
28
28
28
30
26
32
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Average
rebound
number27.3
3
28.
66
28.6
6
28.33 27.33 29
Cube
grade
M40
Point 1 2 3 4 5 6
Rebound
number
38
40
44
36
40
38
42
40
44
38
36
38
44
36
42
38
40
42
40
38
42
36
44
40
44
38
40
36
38
40
42
36
38
44
40
40
Average
rebound
number39.
33
39.
66
40.3
3
40 39.33 40
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Average Rebound Number:
Average Rebound Number Quality of Concrete
>40 Very good hard layer
30 to 40 Good layer
20 to 30 Fair
< 20 Poor concrete
0 Delaminated
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Tested M40 cube
Good layer
Results:
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FACTORS AFFECTING THE TEST RESULTS:
Type of Cement
Type of Aggregate
Surface Condition and Moisture Content of Concrete
Curing and Age of Concrete
Carbonation of Concrete Surface
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2) ULTRASONIC PULSE VELOCITY-UPV TEST
This test is used for determination of the uniformity of
concrete in and between members and Detection of the
presence & approximate extent of cracks, voids & other
imperfection in concrete.
Reference code: IS 13311 Part I
Higher is the velocity, better is the quality of concrete
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The apparatus for ultrasonic pulse velocity measurement consists of the following:
(a) Electrical pulse generator(b) Transducer – one pair(c) Amplifier(d) Electronic timing device
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UPV methods
Direct method
Indirect method
Semi direct method
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Velocity criterion for concrete quality grading is given by
IS 13311 (Part-I):1992
Sl. No.Ultrasonic Pulse Velocity by Cross
probing (Km/Sec)Concrete quality grading
1 Above 4.5 Excellent
2 3.5 to 4.5 Good
3 3.0 to 3.5 Medium
4 Below 3.0 Doubtful
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DIRECT METHOD
Path
length
(m)
Point velocity (km/s)
A B
0.290
1 3.75 4.46
2 3.44 4.08
3 3.46 4.10
4 3.45 4.02
5 3.65 4.29
6 3.77 4.13
7 4.13 4.36
The test is performed on a column of size
350mmx290mm and the values are obtained as below:
INDIRECT METHOD
Path
length
(m)
Point velocity (km/s)
A
0.200
1 3.08
2 2.87
3 2.83
4 2.99
5 3.22
6 3.085
7 3.10
SEMIDIRECT METHOD
Path
length
(m)
Point velocity (km/s)
A
0.316
1 3.76
2 3.64
3 3.35
4 3.54
5 3.42
6 3.45
7 3.70
Good
Medium
Good
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Concrete
grade
velocity (km/s)
DIRECT METHOD SEMIDIRECT
METHOD
M25 4.348
4.286
4.644
4.206
4.240
3.926
4.889
M40 4.688
4.836
4.718
4.511
4.711
4.417
4.417
M50 4.868
4.839
4.958
4.936
4.609
4.818
4.992
The test is performed on a cube of size
150mmx150mmx150mm and the values are obtained as
below:
Good
Excellent
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3) CORE EXTRACTION FOR COMPRESSIVE STRENGTH TEST
Reference Standard codes:
IS 516
IS 1199
SP 24
Apparatus for Core Extraction of concrete:
Core drill.
Saw for trimming the ends of the core.
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Results:
M40 GRADE
Mold Load (KN) Area (mm2) Stress (N/mm2)
CUBE 982.5 150x150 43.67
CORE 617.5 π/4 x 138² 41.29
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4) CARBONATION DEPTH MEASUREMENT TEST
Carbonation of concrete occurs when thecarbon dioxide, in the atmosphere in thepresence of moisture, reacts with hydratedcement minerals to produce carbonates.
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The core retained itspurple color after thesolution is poured.Thus, the core stillretains its alkalinecharacteristic and nocarbonation had occur.
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5) CONCRETE COVER MEASUREMENT TEST
Profoscope is specially for detecting the,
Depth of concrete cover,
Rebar location and
Its orientation.
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Application:Profoscope is used to evaluatereinforced concrete structures:•Locate in structures embeddedwith reinforcement.•Locate in structures embeddedwith cable ducts.•Locate rebars upto 160mm.
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6) HALF-CELL POTENTIOMETER TEST
Reference code: ASTM standard C876-91
To assest reinforcement corrosion.
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The test is performed on a beam of size 600mmx300mmx60mm in which one half is casted with salt water and other half is casted with normal water.
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Half-cell potential reading, vs. Cu/CuSO4 Corrosion activity
less negative than -0.200 V 90% probability of no corrosion
between -0.200 V and -0.350 V an increasing probability of corrosion
more negative than -0.350 V 90% probability of corrosion
Probability of corrosion according to half-cell readings :
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Rebars
Half-cell potential reading (V)
Salt water casting Normal water casting
1 - 0.302
-0.288
-0.314
-0.243
-0.241
-0.258
2 -0.529
-0.477
-0.401
-0.296
-0.311
-0.283
3 -0.625
-0.627
-0.631
-0.172
-0.170
-0.159
Both side Increasing probability of
corrosion
Corroded and
increasing probability of corrosion
Corroded and Non-corroded
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FACTORS AFFECTING TEST RESULTS:
o WETTNESS OF SURFACE
o CARBONATION
o ELECTRIC CURRENT
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7) CHLORIDE CONTENT TEST
Reference code: IS:14959 Part – III – 2001
To determine the chloride content from the
powdered sample which is collected from the
concrete by drilling method.
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Sl.
No.
Volume of
pipette
solution
Burette reading Concordant
valueInitial Final
1
.
80ml 0 ml 16.6 ml 16.6 ml
Chloride content = x (equivalent value of chlorine x 250ml)
x (3.545x250)
=3.59 kg/m3
= 0.149%
=0.149 x in kg/m3
Test results Interpretations
Below 0.6 kg/m3 No corrosion.
Above 0.6 kg/m3 High chloride attack.There is high chloride attack on the selected concrete.
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Conclusion : Various NDT methods can be used depending upon
the type & age of structure to check the integrity ofstructure.
USPV, rebound hammer & cover meter can be appliedto newly constructed structures to check the quality ofconcrete adequacy of cover before applying live load tothe structures.
Half cell potentiometer & carbonation test can beapplied to old structure to access to carbonation depth& amount of corrosion occurred.
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Remedial measures: Replacement of cover concrete by microconcrete
Polymer Modified Mortar Treatment
Protective Coating
Jacketing
Water proofing to slab
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