DEPARTMENT OF CIVIL ENGINEERING,

THE NATIONAL INSTITUTE OF ENGINNERING,

MYSORE-08

AFFILIATED TO VISVESVARAYA TECHNOLOGICAL UNIVERSITY,

BELGAUM, KARNATAKA.

SEMINAR REPORT

ON

NON – DESTRUCTIVE TESTING OF CONCRETE

STRUCTURES

PRESENTED BY: JEEVITHA.N

USN: 4NI05CV020

UNDER THE GUIDANCE

OF

Dr. N.SURESH

VISVESVARAYA TECHNOLOGICAL UNIVERSITY,BELGAUM.

DEPARTMENT OF CIVIL ENGINEERING,THE NATIONAL INSTITUTE OF ENGINEERING,

MYSORE-570008

CERTIFICATE

This is to certify that Mr. K.VINAY RAJ with USN 4NI06CV014 of B.E 8th semester has successfully completed the seminar entitled “FLY ASH-BASED

GEOPOLYMER CONCRETE” for the partial fulfillment of bachelors degree in Civil Engineering as prescribed by Visvesvaraya Technological University, Belgaum during the academic year 2009-2010.

GUIDE HEAD OF DEPARTMENT

Dr. N. SURESH Professor

DEPARTMENT OF CIVIL ENGINEERING,N.I.E COLLEGE, MYSORE.

ASSESMENT SHEET

NAME: JEEVITHA.NUNIVERSITY SEAT NUMBER: 4NI05CV020 SEMINAR TITLE: NON – DESTRUCTIVE TESTING OF CONCRETE STRUCTURES

DIVISION WRITE UP PRESENTATION TOTALMAX MARKS 20 30 50MARKS OBTAINED

EXAMINARS

NAME SIGNATURE GUIDE EXAMINAR-1 EXAMINAR-2

HEAD OF THE DEPARTMENT Dr. G.RAVI

ACKNOWLEDGEMENT

The satisfaction that accompanies the successful completion of any

task would be incomplete without mentioning of the people who made it

possible. Many are responsible for the knowledge and experience gained

during the work course.

I would like to express a deep sense of gratitude to Sri Dr.

N.SURESH, Professor, Civil Engineering Department, NIE MYSORE, for

his constant encouragement, guidance and inspiration, which enabled me to

complete this seminar work.

I would also like to express my gratefulness towards all the faculty

members, Department of Civil Engineering, NIE MYSORE for their timely

suggestions.

I am thankful to Dr. G. RAVI, Professor and Head, Department of

Civil Engineering, for bringing excellent academic climate to finish my

work successfully.

NON DESTRUCTIVE TESTING OF CONCRETE STRUCTURES

Abstract:

Non destructive testing methods have been in use for last about 40 to 50 years.Non destructive testing methods are a powerful means for evaluating the strength, durability and quality control of the existing concrete structures.In addition to above, the depth of cracks, micro cracks and progressive deterioration can also be studied by this method.Some properties of concrete such as hardness, resistance to penetration of projectiles, resonant frequency and its ability to allow ultrasonic pulse velocity to propagate through it can be estimated.With the help of the electrical properties of concrete and its ability to absorb, scatter and transmit x-rays and gamma rays etc. moisture content, density, thickness and cement content of concrete can be estimated.

Introduction:

The Usual way of testing concrete is by means of casting cubes and then crushing them.

The quality of product in the field is checked by non-destructive methods.

The main advantage is determination of concrete properties without damage.

NEED FOR TESTING:

Monitoring long-term changes in material properties and structural performance.

To check for workmanship.

For remedial schemes and repairs.

To check for design specification.

Applications:

Measurement of concrete uniformity

Detection of cracking and honeycombing

Strength estimation

Assessment of concrete deterioration

Measurement of layer thickness

Measurement of elastic modulus

Strength development monitoring.

Different testing methods are: -

1. Penetration Tests2. Rebound Tests3. Pull-Out Tests4. Test for corrosion rate measurement5. Ultrasonic Pulse Velocity Test

1. Penetration Tests:

Testing can be done in both laboratory as well as insitu. Commercially this test is called as Windsor probe test. Equipment consists of a powder-actuated gun or driver, hardened alloy probes, loaded cartridges, a depth gauge for measuring penetration of probes and other related equipment. A probe, diameter 0.25 in. (6.5 mm) and length 3.125 in. (8.0 cm), is driven into the concrete by means of a precision powder charge. Depth of penetration provides an indication of the compressive strength of the concrete. Although calibration charts are provided by the manufacturer, the instrument should be calibrated for type of concrete and type and size of aggregate used.

Limitations and Advantages:

The probe test produces quite variable results and should not be expected to give accurate values of concrete strength.

It has, however, the potential for providing a quick means of checking quality and maturity of in situ concrete.

It also provides a means of assessing strength development with curing.

The test is essentially non-destructive, since concrete and structural members can be tested in situ, with only minor patching of holes on exposed faces.

2. Rebound Tests:

It is suitable for both laboratory and field work.

It is a quick method for assessing the quality of concrete based on surface hardness indicated by the Rebound number.

A higher rebound value indicates the higher strength / surface hardness of concrete.

The instrument used is the Schmidt hammer, which weighs about 4 lb (1.8 kg).

This equipment works based on the spring controlled hammer slides on a plunger within a tubular housing.

The hammer is forced against the surface of the concrete by the spring and the distance of rebound is measured on a scale.

The test surface can be horizontal, vertical or at any angle but the instrument must be calibrated in this position.

Calibration can be done with cylinders (6 by 12 in., 15 by 30 cm) of the same cement and aggregate as will be used on the job.

The cylinders are capped and firmly held in a compression machine.

Several readings are taken, well distributed and reproducible, the average representing the rebound number for the cylinder.

This procedure is repeated with several cylinders, after which compressive strengths are obtained.

Method of Calculation:

Average rebound number will be calculated after exclusion of freak values and applying necessary correction factor for position of Rebound Hammer.

To evaluate the strength of concrete based on Rebound numbers, an appropriate calibration chart shall be established based on laboratory tests.

Limitations and Advantages:

The Schmidt hammer provides an inexpensive, simple and quick method of obtaining an indication of concrete strength.

The results are affected by factors such as smoothness of surface, size and shape of specimen, moisture condition of the concrete, type of cement and coarse aggregate, and extent of carbonation of surface.

Factors affecting the rebound hammer test results:

Mix characteristics

(a) Cement type

(b) Cement content

(c) Coarse aggregate type.

Member characteristics

(a) Mass

(b) Compaction

(c) Surface type

(d) Rate of hardening and curing type

3. Pull-Out Tests:

A pull-out test measures, with a special ram, the force required to pull from the concrete a specially shaped steel rod whose enlarged end has been cast into the concrete to a depth of 3 in. (7.6 cm). The concrete is simultaneously in tension and in shear, but the force required to pull the concrete out can be related to its compressive strength. The pull-out technique can thus measure quantitatively the in-situ strength of concrete when proper correlations have been made.

Limitations and Advantages:

1. Although pullout tests do not measure the interior strength of mass concrete, they do give information on the maturity and development of strength of a representative part of it.

2. Such tests have the advantage of measuring quantitatively the strength of concrete in place.

3. The pull-out, of course, creates some minor damage.

4. The test can be non-destructive, however, if a minimum pull-out force is applied that stops short of failure but makes certain that a minimum strength has been reached.

6. Test for corrosion rate measurement:

The instruments in this field are Gecor Systems.

Purpose of this test is to measure the reinforcement corrosion for Service life estimation Evaluating the efficiency of corrosion arresting measures

such as application of inhibitors, membranes or electrochemical removal of chlorides

Condition surveys of suspect reinforced structures, especially structures in wet environment where the classic potential mapping may provide misleading and/or insufficient information

Monitoring RC structures for corrosion activity Testing the corrosion activity in repaired areas

The reinforcement corrosion is evaluated by the corrosion rate stating how much steel is being dissolved in µm/year (10‾³ mm/year). In addition, half – cell potentials and the electrical resistance of the cover layer is measured.

Instruments used for corrosion testing are:

6. Ultrasonic Pulse Velocity Test:

Testing is done using instruments that use sound or stress waves in order to determine the properties of concrete and other materials non-destructively.

Used to assess the quality and strength of in-situ concrete in structural members.

Used to check the compaction of concrete, uniformity of concrete, determination of cracks, presence of honeycombs, level of deterioration and also strength estimation.

The PIES (Portable Impact-Echo System), is an advanced instrument for non-destructive detection of flaws and defects in a variety of civil infrastructures ranging from bridges, parking structures and buildings to dams, piles, tunnels, tanks and marine structures.

Method of calculation of pulse velocity:

Velocity = (Distance traveled / Path length)

Time taken

Pulse Velocity in concrete will be represented in Km/sec.

Appropriate correction factors to be applied depending on site condition & factors influencing velocity of pulse

Instruments used for Ultrasonic testing are:

Disadvantages of NDT: -

Though testing methods are simple to perform, analysis and interpretation of these tests is tedious.

Thus special knowledge is required to analyse the properties of hardened concrete.

Specimens are not loaded up to failure and the strength estimated cannot be expected to yield absolute values of strength.

Conclusion:

There are number of tests as Non-Destructive, Semi/Partial Destructive and Destructive tests that in practice to evaluate structural members.

Depending on data required, site conditions, Structural member conditions, etc., any one of them or combination of above can be used to ascertain the status of member.

Although tests are not difficult to perform, test data are not always easy to interpret because concrete is a most complex material.

Relative strengths of concrete in different parts of the same structure can be determined

References:

Malhotra, V.M. Testing hardened concrete: non-destructive methods. Amer. Concrete Inst., Monograph No. 9, 1976.

Malhotra, V.M. and G. Carette. Comparison of pull-out strength of concrete with compressive strength of cylinders and cores, pulse velocity and rebound hammer. Canmet Report 76-8, Nov. 1975.

Jones, R. and I. Facaoaru. Testing of concrete by the ultrasonic pulse method. Materials and Structures, Vol. 2, No. 10, July-August 1969, p. 253-661.

Leslie, J.R. and W.J. Cheeseman. An ultrasonic method for studying deterioration and cracking in concrete structures. Amer. Concrete Inst., Proceedings, Vol. 46, Sept. 1949, p. 17-36.