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INTRODUCTION

Non{estructive

testing

(NDT)

is an

effective

method

for

quickly

testing

and

evaluating

the

properties

of

materials,

which

does not

destroy

the

physical,

mechanical,

even

chemical

properties

of

materials and

has

no

influence

on

future

performance.

This

method

of

NDT

is

preferred

because

of

its

distinct

advantage

over

the

physical

properties

test.

Portable

Ultrasonic

Nondestructive

Digital

lndicating

Tester

(PUNDIT)

is

one

of

the

NDT

equipment

specially

designed

for

nondestructive

assessment

of

massive

material.

The

exploitation

and application

of

this

technology

have been

quickly

developed

in concrete

fields for

its

evident

advantages.

ln

civil

engineering

application,

this

equipment

has

advantaged

to

solve

the

problem

when

the

structural

elements

cpnstructed

are

questionable

by the

client.

Basically

the equipment

give

real

time

modulus

of elasticity

(MOE)

reading

of

material

tested.

However,

for

more convenient

with

the

result

produced

by the

equipment

when

utilising

it

in

specific

structural

concrete

material,

it should

be

validated.

Figure

1

shows example

application

of the

equipment

on beam

structural

element

of

Mataram

Mall

Car

Park.

By the

contractor

request,

the

equipment

was applied for assessment

of the

car

park

building element

due to construction

doubted

as

the

material used

to

perform

the

element

did not compliance

with

specification

of

the

concrete

strength

determined. Before

utilising

the

equipment,

it

has

been

done

testing on

laboratory

prior

to

test

existing of

beam

specimens.

Volume

9

No 2, Desember 2008

ln

this

paper

however,

the

primary

objective

of

this

study

is to

investigate

the

dynamic

MOE of

normal weight concrete

(NWC)

and

lightweight concrete

(LWC)

beam

obtained

from Pundit aparatus

in

laboratory

only.

ln the

present

study,

the difference

and

relationship

between dynamic

MOE

and

static

MOE

were analyzed and

the

accurateness

and

reliability

of MOE

evaluated by

the

NDT

techniques

were

discussed.

The

findings

of

this study

can

provide

scientific

references

for

quickly

testing

concrete

structure.

LITERATURE

REVIEW

Physical

propertles

of

concrete

can

be

detected

by,

for

example

the

speed

of

an

ultrasonic

pulse propagation

through

the

concrete.

The

application of

ultrasonic

pulse

velocity

(UPV)

to the

nondestructive

evaluation

of

concrete

quality

has been

widely

investigated.

However,

their

effects

on the

ultrasound

and the

relationship

between

compressive

strength

and UPV

have

received

little attention

(Tanyildizi

and

Coskun,

2007).

The

pulse

velocity can

be determined

from

the

following

equation

(BS

1881-203,

1986)

tr/

=

Sr/f

.

. .. .... .....(1)

where I/

is

pulse

velocity

In

km/s,

S

is

path

length and t

represent transit time

(ps).

The

MOE,

one

of

primary

indexes

in

evaluating

mechanical

properties

of concrete,

indicates

the degree of

concrete

resisting

distortion.

A higher

value of MOE

indicates

that the

material

is

not

easy

to

be distorted

and

has

a

high

rigidity.

A

prediction

model of

MOE

using

NDT technique

has been

developed

(Neville

and Brokes,

1987). The

MOE

increases

more

rapidty than

strength.

The

MOE

of

lightweight aggregate concrete

is

usually

between

40 and 80

per

cent

of the

MOE of normal

weight

concrete

of the

same

strength,

and,

in

fact,

is

similar

to

that

of the

cement

paste.

The MOE obtained

destructively

using

standard

test in laboratory namely static

MOE,

8", whilst dynamic

MOE, Ed,

obtained

from

non-destructive

test.

The

PUNDlTplus

equipment

is

developed

with

consider

to some

parameters

such as

path

length, density and

poisson's

ratio and

dynamic

MOD, Ed, is given

by equation

below

(BS

1BB1-203,

1986;

CNS

Farnel Ltd,

2006).

Figure

1. Application

of

Pundit

on

concrete

beam

g4

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Volume

9

No

2,

Desember

2008

i,

=

','t'L-

6)(L

-2o.tli.l

-

6)

(2)

where,i

=

density,

v

=

velocitY

and

o

=

poisson's

ratio.

The

relationship

between

static

and

dynamic

modulus

of

elasticity

is

given in

the

equation

below

(Nevile and

Brokes,

1987)

i:

=

1.15E:

-

1S

.

...

'...

(3)

where

E,

and

E1

?ra

expressed

in

GPa.

The

relation

does

not apply

to

concrete

containing

more

than

500

kg

of

cement

per

cubic

metre

of concrete.

When

it

is

required

to

relate

the

dynamic

modulus

to

strength,

the

static

modulus

may

be

estimated

using

equation

(3)

and

substituted

into

either

equation

(4a) for

normal

weight

concrete

or equation

(4b)

for

lightweight

concrete where

applicable.

i,

=.1i00.?

-

.-

.(4a)

or

ir

=

0,75

x {700..';,

.'

.

..

(4b)

where

E,andf

,are

expressed

in

MPa.

Modulus

of elasticity

obtained

from

cylinder

standard

test

€n

be

obtained

from

the

following

equation.

r

-

,'s-

-

(.i,i

i-.'"

-

0.00005i -.

.

(5)

-

_

,-:

where

52

is stress

about

40%

of

ultimate

stress

(O

4

f,),

51

is

stress

at

strain value

of

0.00005

and

ez

is a strain

value

at the

level

stress

of

52.

METHODOLOGY

Iest

specimens

Nine

beams

of

150x250x2500

mm

reinforced

with

three

different

reinforcement

ratio

were

prepared to be

measured

their

modulus

of elasticity.

Three

groups

of

cylinder

specimens

of

150

x 300

mm

length

taken

from

the

beam

concrete mixture

were

used

with

three

different

mix

proportions.

Each

group

consisted

of

nine

specimens

from

each

batch

of

the

concrete

mixture.

The

cylinders

were

tested

at

age

28

days

after

water

curing.

Table

1

presents detail

mix

proportion

to

produce

two

normalweight

concrete

of

17

and

30

MPa

and

a

lightweight

concrete

of

17 MPa

as

refers

to

ACI

211.2'98.

Test

procedure

Prior

to

destructive

testing

using

UTM

machine,

specimen

was

scaled

and

tested

nondestructively

using

Pundit

equipment'

Figure

2 shows

the

application

of

the

Pundit

plus

equipment

to

predict MOE of

cylinder

specimen.

The equipment

display

value of

MOE

in GPa.

Table

1.

Mix

Proportions

for

1

m3

concrete

PC

\l

alel

Sand

(irarcl Pttntie<

ID

{lBt

tlgt

(LP)

tkgr r[1't

0.5 8

327

r90

8r0

r 073

NW(

0.45

422

rqo

0.40

507.5

203 467.23

182.3

I-\\',C

ln

addition, compression test were done

using

Standard

Compression

machine

as

shown

in

Figure

3

produced

stress

and

strain

I

073

15

g;nure

Z-ffiamic

Modulus of elasticity, Ei, m€zsUl€meflt

Modulus

of elasticitY,

Ec.

95

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relationship.

From

the relationship

the

MOE

can

be

generated

by

applying equation

(5).

Finally, to asses

strength

of

beam,

the

PUNDIT was

applied by direct transmission

technique to surface

of

the

beam

in

three

places

as

shown

in

Figure

4

below.

Figure

4.

Strength assessment

of

beam using

PUNDIT

aparatus

RESULT AND DISCUSSIONS

Strength test results obtained

from

destructive

test

on

cylinder

specimen

of

normal

weight

and lightweight concrete

are

presented

in Figure 4. From

the

figure it can

be

seen

that

normal weight

concrete

produce

higher strength than lightweight concrete. This

is

caused by coarse aggregate used to

perform

normal

weight

concrete has

specific

gravity

higher

than

pumice

as

lightweight

marse aggregate. From

the stress and

strain

relationship

as

shown in Figure

4

it

can

be

calculated modulus

of elasticity

(MOE)

using

equation

(4).

0

0000

0 0Cj10

0

0020

0

0030

Strsi n

Figure

4.

Typical

relationship

of

Stress-Strain

cylinder

specimen.

Volume

9

No

2,

Desember

2@8

Cylinder

specimens of normal weight

and

lightweight

concrete

were

tested.

Firstly,

non-destructive test method

was

applied

producing

dynamic modulus

of elasticity,

E6

followed

by

destructive

test

producing

static

modulus

of

elasticity E". Both

test

results

are

compared

and

presented

in

Figure

5

below.

Figure 5. Comparasion between

Static and dynamic

Ec

From

the

figure it

can be

seen

that

there

is

a linear relationship

between E.

and

E6. For more

convenient the

relationship is

presented

as Equation

(5).

This equation

produced

results with trend

similar

to

results

produced

by the British Standard as

given

previously

by

Equation

(3).

trc

=

1.038Eci

-

11,'15.

.....

....

..(5)

For more

comprehensive discussion

the

test

results obtained

by

both

test

method is

presented

in

Figure

6.

Figure

6 shows that

two

types

of concrete

specimen

of

lightweight

concrete

(LWC)

and

normal

weight

concrete

(NWC)

were

tested

using static and

dynamic

test method.

45000

{0000

35rOO

30mo

{25ooo

$zoaN

ul15000

1rt00l

5t100

0

Figure 6. Conqete modulus

of

elasticity

against density

30

25

e20

o-

=

15

o

o

o

-._

L

iU

a

0

#N

I

Pundit's

Transducer

Right

End

*,.,,,

la.

a

=1

038 E{-1 1,45

o

96

8/18/2019 Akmaludin

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Volume

9

No 2, Desember

2008

Table

1.

Results

of

Beams

assessment

PUNDIT

Plus

BEAM

Ed

(MPa)

Ec fc

fc

SPECIMEN

Left

End Middle

ffi(Mpa)

(Mpa)1 (Mpa)2

Ratio

(1)

(2)

(3)

(4)

($

(6) (7)

(8)

(e)=(il(8)

NWC17

2 34000

32000

34000

33300

23100

24,16 28,50

0,85

NWC17

3

32s00

34900

35000

34100

23900

25,86

29,02

0,89

NWC17

5

33000

34000

32000 33000

22800

23,53

29,25

0,80

NWC30 2

34500

38300

35000

35900

25800 30,13

40,69

0,74

NWC30 3

33800

35500

37400

35600

25500

29.44 41,05

0,72

NWC30 5

34400

43400

33000

36900

26900

32,76

36,23

0,90

LWC17

2

25AO0

26400

27400

26300

15800 20,09

17

,83

1,13

LWC17

3

26700

28000

26000

26900

16500

21,91

17,90

1,22

LWC17

5

26800

25200

27200

26400

16000

20,60

18,',|1

1,14

Note:

1.

PUNDIT

assessment

2. Cylinder

test

ln

all

cases

dynamic

test

method

produced

higher

value

of

E

than the static

one.

However,

both

methods

have

similar trend

which

is

increasing

as

concrete

density

increased.

This

result suggested

that

density of

the

concrete

affect the

values of

modulus

of

elasticity.

Therefore

it is

reasonable

to use

PUNDIT

plus

for assessing

concrete

beam.

Three

places

on beam

surface

as shown

in

Figure

4

were

scanned

by the

equipment

producing

results

(E6)

as

given

in column

(2),

(3) and

(4)

for

left

end, middle and right end of

the

beam

respectively.

The average

value

of

the

results

was taken

to

represent

dynamic

MOE of

the beam as

given

in column

(5)

of

Table

1.

ln

addition,

Equation

(5)

was used

to

obtain

E"

values and

results

presented

in

column

(6)

of

Table 1.

Furthermore,

the

strength

of concrete beam

was obtained

by

applying

equation

(4)

and

results shown

in

column

(7).

The

strength

values

were

compared

with the strength obtained

from

cylinder

test

(column

(8)

Table

1)

and

represented

in

ratio

between strength

obtain

using

PUNDIT and the test cylinder

as

given

in

column

(9)

of

Table 1.

From Table

1, it

can be seen that the strength

prediction

of the beam using

PUNDlTplus

for

normal

weight concrete,

gave

value

lower

than

the

strength

value

produce

using

standard

test. However,

for

light

weight

concrete

produce

over estimate

prediction

when

compare

to cylinder

test

results.

The

different

result

showed

in

Table 1

between column (7) and

(8)

is due

to

different

object

tested

ie beams and

cylinder specimens

respectively. Although

the

beams have similar

mix

proportion

to cylinder

specimens,

however

treatment

given

to the

cylinder

and the

beam

was different

especially

in compacting

the

specimens

as a results the

density could

be

different.

Therefore, the

value

of

MOE

obtained

from

the

beam tested

give

more

realistic value

than

the value obtained

from

the

cylinder

test, because

the

value obtained

has

considered

straightfonrvard

the

density

of

the

beam.

CONGLUSIONS

AND RECOMENDATIONS

The

following conclusions are

drawn

from

the

study:

1. The

values

of

MOE rely

on

density of the

specimen

tested.

The more value of the

density the

more

modulus

of

elasticity

produced.

2.

Strength

prediction

of

the

beam studied

varies

trom

0.72 to

0.90

toward

cylinder

strength

for

NWC but

varies 1.13

to

1.22

for

LWC.

3.

Strength

prediction

using

PUNDIT

for

normal

weight

concrete

underestimate

the

strength

given

by

the standard

test.

4. Strength

of

lightweight concrete

evaluated by

PUNDIT

overestimated the

strength

obtained

using

standard

test.

For

more

comprehensive

evaluation

it is

needed to study

more

specimens

to improve

the

model

proposed.

REFERENCES

ACI

Committee

211,

Standard

Practice

for

Selecting Proportions

for

Structural

97

8/18/2019 Akmaludin

6/6

Lightweight

Concrete

(ACt

21

1.2-gS),

American

Concrete

lnstitute,

Farmington

Hiils,

MI,

20

pp.

BS

1881-203,

1986,

Testing

concrete.

Recommendations

for

measurement

of

velocity

of

ultrasonrb

pulses

in

concrete,

British

Standards

lnstitution.

Farnel,

CNS,

2006,

Manual

instruction

of

PUNDtTplus,

CNS

electronic

ttd.

Volume

9

No

2,

Desember

200g

Neville

A.M.,

Brooks,

J.J.,

1997,

Concrete

Technology,

Longman

Tanyildizi,

H.

and

Ahmet

Coskun,

2A07,

Fuzzy

logic

model

for

prediction

of

compressive

strength

of lightweight

concrete

made

with

scoia

aggregate

and

fly

ash,

lnternational

earthquake

symposlum

Kocaeli

98