INTRODUCTON TO NDT

8/4/2019 INTRODUCTON TO NDT

http://slidepdf.com/reader/full/introducton-to-ndt 1/46

Abul Kalam AzadCivil Engineering DepartmentProf.,

King Fahd Univ of Petroleum & Minerals

Presented by

Test Methods :

• Nondestructive

• Semi-destructive

• Destructive

Test methods can be divided into

three categories

(a) methods for estimation of

concrete strength

(b) methods for estimation of properties

other than strength

(c) methods for physical evaluation of structure

Methods for Estimation of Concrete Strength

S.No. Test Equipment Type

1 Core test Mechanical

2 Surface hardness method Mechanical

3 Ultrasonic pulse velocity Electrical

4 Break-off and Pull-off Mechanical

5Penetration Test

(Windsor Prob)Mechanical

6 Pull-out Test Mechanical

7 Lok Test & capo Test Mechanical

Strength Tests- a Comparative Assessment

Methods for Determining Properties Other than Strength

A wide range of test methods for

• composition

• quality

• durability characteristics

What can be done:

(a) Composition:

• Cement content, CA/FA ratio,

• aggregate gradation,

• original W-C ratio, rebar location and cover.

(b) Quality:

Aggregate type, chloride content,

sulphate content, permeability,

delamination/voids,

crack width and depth.

(c) Durability:

Alkali-aggregate reactivity,

corrosion attack and activity,

sulphate attack, carbonation,

salt weathering.

Methods for Physical Evaluation of

Structure :

• delamination, voids, honey-combing

• spalling

• extent of damage

• cracking

• uniformity of concrete

• structural strength/rating

Surface Hardness Method

- Popularity known as Schmidt Hammer

- Widely used ; truly nondestructive

- Easy to use ; not reliable for fc

Testing of Concrete in Structures

Typical rebound hammer

Procedure

• Make surface smooth, if necessary, and dry

• Use grids points over an area to avoid bias

• Hold hammer normal to the surface

• Take as many readings as possible

• Convert readings to comp. strength (calibration)

• Note correction for inclined surfaces

Factors Affecting Readings

- Surface roughness

- Member size (small member may move)

- Moisture condition

- Direction of test

Ultrasonic Pulse Velocity

- Widely used

- Good reliability ; truly NDT

- Portable equipment ; easy to use

Transducers Arrangement

1. Direct

2. Semi-direct

3. Indirect

Type of reading (a) Direct, (b) semi-direct and (c) indirect

Transducer Arrangement

Important Factors Affecting Readings

• Path

• Moisture condition

• Effect of reinforcement

• Cracks/voids in the path

Pull-out Tests

Lok Test (developed in Denmark)

Capo Test

Lok – Test

(Preplanned tests–

new structures)

• Attach the head and shaft to the formwork

• Concrete is cast

• Remove formwork at test location

• All parts except disc is removed

• A pull-rod is treaded to disc

• Pull-rod attached to testing equipment

• Pull rod pulled and the force to pull out is noted

• Calibration provided to convert into strength

Lok Test procedure

Capo-test

(For existing structure)

Similar concept as Lok-test, except hole

is made and disc is inserted

Remarks

- Capo-test has good reliability

for estimation of strength

- Equipment available (Portable)

- Needs some practice

Other Methods

• Penetration Method

• Pull-off Tests

• Break-off Tests

(These are not widely used)

Penetration Method

- Popularly known as ‘Windsor probe’

Pull-off Method

- Arrangement as shown

- Direct pull-off using epoxy is not recommended

- Partial coring recommended

Break-off

Arrangement shown

- Modulus of rupture is estimated

- High degree of variability

Location

- If concrete is in suspect, use weakest area

- For compliance, avoid unrepresentative areas

- Avoid reinforcement

- Avoid critical areas

- Desirable 100 mm dia for strength;

though 70-75 mm dia widely used

- Generally size affects strength

(if small dia, less than 70 mm, use correction factor)

- L/d ratio ~ 2 ; for smaller L/d ratio, use correction factor

- Accuracy decreases as agg/core dia increases

(use at least 3 * maxm. size)

No. of Cores

- Depends on purpose

- For strength verification, use statistically significant numbers

- Minm. 3 to 4 cores for strength

- Compromise between cost, damage and accuracy

Trimming, Capping andMeasurement

- Trim edges with a saw to make ends square

- Cap properly with horizontal face

- Measure length, average diameter

(cross readings at mid-height and at ¼ points)

- Calculate density

Testing

- Test in dry or wet condition as required

(dry cores 10-15% stronger than wet cores)

- Test under a comp. machine, neither tooslow or too fast (15 N/mm2 /min)

- Avoid eccentricity

Correction Factors

- L/d ratio

- Reinforcement (not recommended)

- Small diameter cores

C O R R E

C T I O N

F A C T O R

LENGTH / DIAMETER

BS 1881

CONC. SOC.

1 1.2 1.4 1.6 1.8 2

Effect of length / diameter ratio on core strength

summary

A number of test methods that can be appliedto determine strength of in-situ concrete have beenpresented.

Core test must be included in a test program to lend

confidence in the measured strength. Hammer rebound numbers are least accurate. Only a

notional estimate can be obtained.

High strength does not necessarily mean high qualityconcrete, though it is expected in most cases.

Thank you for your audience(questions & discussions)

INTRODUCTON TO NDT

Documents

A kind and gentle introducton to rac

1.1 INTRODUCTON of IFFCO:The Fertilizer Industry In

2. intro to NDT

INTRODUCTON TO WATER QUALITY IN AQUACULTURE Unit 4.1 Dissolved Oxygen/Aeration

1. introducton (1)

to Machine Learning Support Vector Machines · 2018-03-22 · « IntroducTon to Machine Learning » (A. Cornuéjols) 2 OrganizaTon of the course / 107 1. IntroducTon to Machine Learning

Introducton to Psychology

Intro to Ndt Nde

Introduction to NDT

Introducton to Labanotation

Introducton to Product Ownership - IIBA®

Elevate introducton & overview winter 2014

DMRG Theory and Introducton -Manual for DMRG Code

Introducton to Verification Validation and Accreditation

Salesforce1 World Tour London: Introducton to ExactTarget Marketing Cloud

Introducton Au Droit Civil

Neural Networks: Introducton

1slide Introduction to NDT

CHAPTER 1. INTRODUCTON TO REINFORCED CONCRETE · CHAPTER 1. INTRODUCTON TO REINFORCED CONCRETE 1.1. INTRODUCTION Traditionally, the study of reinforced concrete design begins directly

Ch:1 INTRODUCTON