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BS 1881 :

Part

209 : 1990

UDC 666 972 691 32

620 1

British

Standard

Testing

concrete

Part209

ecommendations o r

t h

measurement

of dynamic modulus

of elasticity

Essais des betons

Partie

206

ecommandations relativesau rnesurage du module dynamique d blasticitb

Priifung von Beton

Teil 206.

Empfehtungen

fur die Messung

des

dynamischen

E

lastizitatsmoduls

ljl

I I ^_.+. ^-.. ,

YO

COPYING

WITHOUT

B SI PERMISSION EXCEPT

S

PERMITTED Y COPYRIGW

L W

. . ~ . . ., .;...

y :

'

.

8/9/2019 BS 1881-part 209-90

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..-

S

188

: Part

2 9 : 199

Foreword

Committee responsible

Page

Inside

front cover

Back cover

Rsecrmmsndationr

Scope

2

2

Definitions 2

3

Applications

4 Principle

5

Summary of the test method

2

6

Apparatus

2

7 Methods

of testing laboratory made specimens

3

8

Calculations 4

9

Report

4

Test

configuration

for determination

of

dynamic

modulus

of

el sticity

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BS 1881 Part 209

:

1990

Recommendations

1

Scope

5 Summary ofthe

est

method

This Part of BS

1881

gives recommendations for the

determination of dynamic modulus of elasticity of plain

concrete in t h e laboratory using resonance of vibration

in the longitudinal mode.

NOTE. The titles of the publications

referred

to in this standard

sra lis td on the inside

back

comr.

2 Definitions

For the purposes of this Part of

BS

1881 the definitions

given in BS 3683

:

art 4

and BS 6100

:

Part 6 apply,

together with the following.

2.1 resonance. Condition in which the frequency of a

vibration applied to a body

s

equal to one of the natural

frequencies of vibration of that body

NOTE. This concurrence of frequencies maximizes the amplitude

of vibration

in

the body.

2.2 longitudinal

made

of vibration. Mode in which

compression waves travel through

a

prismatic specimen

in the direction parallel to its length.

NOTE 1 The W a M S are

partially reflected by the

end

faces of

the spe imen

and

thus travel to and fro within

it.

NOTE

2.

Other

modes

exist such

as

transverse nd torsional.

2.3

fundamsntal frequency. Lowest resonant frequency

a t

which a body wil l vibrate in

a

particular mode.

2.4 dynamic modulus of elasticity of concrete ED

.

Ratio of the stress to that part of the strain corresponding

to elastic deformation only.

NOTE. The modulus obtained

refers to

tho initial tangent

to

the

non-linear stresdstrain relationship far concrete which does not

obey Hooke s Law. It is normally appreciably larger than the

statically rneasurod value obtained by the method described

in BS

1881 P a n 121.

Applications

Measurement of dynamic modulus is most commonly used

for comparative testing of concretes in the laboratory and

for assessing degradation in durability

tests,

e.g. in freezing

and thawing

tests.

4

Principle

An elastic or partially elastic body will vibrate i f struck a

blow. Each body possesses many modes

of

vibration and

in geometrical bodies well defined modes may be identified.

This method

i s

concerned only with identifying the funda-

mental longitudinal mode of vibration

in

concrete prisms.

The frequency a t which this vibration occurs depends

largely on the dynamic modulus of elasticity, density,

and length of the specimen.

A-variable frequency oscillator

imparts

an alternating force

to the specimen

and

the response i s sensed by an accelero-

meter or vibration pick-up. The amplitude of vibrations is

monitored by an indicator and when

a

resonant frequency

i s reached, the indicator shows he amplitude to

be

at

a

well defined maximum.

If his resonant frequency s the fundamental frequency

it is

related to the modulus of elasticity

of

the concrete

through the equation in clause 8.

6

Apparatus

6 1

Variable frequency oscillator providing

a

variable

narrow- band sinusoidal output from

500

Hz o 20

kHz

with power adjustable from zero to

a t

feast 2 W.

The frequency of the oscillator output should be indicated

within

n

accuracy of

f 0.5 96

The output of a good quality oscillator tuned to

a

given

frequency should not contain more than 2 of i t s ampli-

tude in the second and third harmonics of the frequency

and should have a stability within

+

5 of the operating

voltage.

6.2 Exciter,

of which the part in contact with the specimen

should have

a

mass

of

not more than

0.2

of the mass of

the specimen.

6.3

Pick-up, of which any part in contact wi th the

specimen should have amass of not more than

0.2

of

the mass of the specimen. The vibration pick-up should

have no resonances at frequencies

below 20

kHz.

6.4 Amplitude indicator,

consisting of

a

voltmeter or

cathode ray oscilloscope incorporating appropriate

amplification facilities.

6.5

Support

consisting of

a

pair of horizontal steel bars

between which the specimen can be

clamped.

The width

of

the contact area of the clamping bars should not exceed

one twentieth o f the length of the specimen. The ban

can be positioned by threaded vertical rods attached to

a

rigid baseboard

which

also carries the exciter and pick-up

mounting posts as shown in figure 1. The baseboard stands

an soft elastomeric pads on

a

rigid workbench to reduce

the effects of extranzous vibrations transmitted through

the laboratory floor.

Alternatively, the specimen may

l i e

on a block of foam

rubber provided that the exciter and pick-up centrelines

re

normal

to

the specimen s end faces.

6.6

Balance

of appropriate capacity to

weigh

the specimen

to the accuracy required by 7.2.

6.7 Vernier calliper complying with BS

887,

capable

o

measuring the lateral dimensions of the specimen to the

accuracy required

by

7.2.

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7

Methodrs f testing

laboratary

made

specimens

The laboratory made specimens should be prisms of circular

or square section with a length not less than three nor

more than five times the maximum transverse dimension.

Specimens should preferably

be

beams made in accordance

with BS I881 Part 109 and then cured in accordance

with BS l t Part 1.

7.2

Preliminary

mmrremm*

Immediately before testing, the length and density of each

specimen should

e

obtained rom

t h e

fol lowing procedures.

(a)

Lengrh.

Calculate the mean length,

L

(in mm) from

at least four symmetrically placed measurements read

to an accuracy of 1 mm.

b) Density. Weigh the specimen in air and record i t s

mass. MA. (in kg) to an accuracy of * 0.25 .

Determine the volume, V, (in m3 of the specimen

either from i t s dimensions or by water displacement

as follows.

1 Dimension For a beam, calculate the mean

width,

a,

and depth. 6 in mrn) from

at

least six

measurements of each dimension spaced equally

along i t s length read to an accuracy of 0.25 mm.

Then

V L b a x

lW9

For a cylindrical specimen, calculate the mean

diameter,

d,

(in

mm

from

a t

least

six

measurements

spaced equally along i t s length read to an accuracy

of 0.25 mm. Then

(2)

Water

displacement.

Weigh the specimen in water

and record its apparent loss in mass, ML, in kg) to

an accuracy of 0.25

96

Then

V =

ML/

pw

where

p is

the density of water which may

be

taken as

1

kg/m3

at ambient temperature.

Method 2 should not be used for unsaturated

specimens.

Calculate the density, p, {in kg/m3)of the specimen

from the equation

p =

MAIV.

BS

1881

Part 2 9 1990

Specimens should ss ld in a condition appropriate to

the

purpose of the investigation.

Where specimens have

been

stored in water they should

be

tested immediately on removal from the water, whilst they

are s t i l l satwand.

Surface

water and grit should be wiped

off the specimen.

The specimen should e clamped or balanced at

i t s

centre

on

the

fixed support.

Contact should be made between the vibrating part of the

exciter and the centre of one end face of the specimen by

means of a weak adhesive or y Qentle spring loading.

Contact should

be

made between a piezo-electric vibration

pick-up and the opposite end of the specimen in

a

similar

way,

s

indicated in figure

1.

Alternativety, an electro-

magnetic non-contactingpick-up can be used in accordance

with the manufacturer s recommendations. Ensure that the

axes of

the

transducers are in the centre of and normal to

the end faces of the specimen.

The exciter should be driven by the variable frequency

oscillator and the oscillations received from the pick-up

should be fed to the amplitude indicator to show the

changes in amplitude received.

The frequency of excitation shouid

be

varied until

a

resonance

i s

obtained and the frequency noted. Resonance

will be recognized when the amplitude indicator shows a

peak response.

As

the frequency i s further varied,

the indicator may show the existence of several resonant

frequencies, some of these relating to modes of vibration

other than longitudinal.

The identification of the fundamental frequency in the

longitudinal mode requires care. Generally the required

frequency produces the greatest response on the indicator

for given settings of the output and gain controls. As a

check, with the specimen

set

up as shown in figure 1,

resonance should also be obtainable at a frequency three

times that of the fundamental frequency.

Ifdifficulties are s t i l t encountered, an approximate value

for the dynamic modulus of elasticity of the concrete

may

be

obtained from a pulse transit time measurement

(see BS 1861 Part

203).

This value may then be

substituted into the equation in clause

8

to yield

n

approximate value for the desired resonant frequency.

The search for the exact frequency may then be confined

to a narrow range about the value so calculated.

Instrument manufacturer s li terature sometimes provides

very useful instructions for identifying the fundamental

frequency. Once identified, this value should be recorded,

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BS 1881 Part 2 9 1990

The

dynamic modulus of elasticity

of

concrete.

E D

in G N / ~ ' ) or each specimen should becalculated to the

nearest0.5 G N / ~rom the formula

ED =

4 n Z ~ 2 p 1 0 1 5

where

L

i s the length of the specimen

{inrnrn);

n

is

the fundamental frequency in the longitudinal

mode of vibration

of

the specimen in

Hz);

p

s

the density

of

the specimen in kg/rn3 .

NOTE. This formula appli

to

all uniform specimens

of

constant

crossmion

9

Report

9.1 General

The report should affirm t h a t

t h e

dynamic modulus of

elasticity of concrete

was

determined

in

accordance with

th recommendations given in S

1881

Part 209

:

1990.

9 1 Information to be included

in

the

tmt

mport

9.2.1 Obl ory

informarion.

The following information

should

be

included

in

the test report:

a)

date of

test;

(b)

description and nominal size

of

the specimenwith

any

identifying mark;

c)

age

of the specimen when tested;

d) conditions in which t he specimen had been stored

between manufacture and testing;

el the calculated dynamic rnodulus,of elasticity

of

the concrete.

9.2.2

dditional

information.

When requested,

t h e following information should also be included in

t he

test

report:

a)

the fundamental frequency;

bj the measured dimensions of the specimen;

c) the density

of the

specimen

a t

the time of testing.

From oscillator

I I

Figure

1

Tart configuration for determination

of dynamic

modulus

of

elasticity

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Publications rehrrd

to

BS

887

Specifmion

or

procision vernier callipers

BS

1881

Testing concrete

Part 10B Method for rnakiw tret

bkuns

from fresh conerste

art

11

1 Method of normal curingof trct rpseimsnr mC method

art 121 Method for determination of M i c

modulw of

elasticity in compression

PM 2 t

Guide m the

u

of non dsrtructivs

methodsof

test for

hardened

concrete

Part 2 3 Raommendrtionr

for

mssruromant of wlocity

of

ultrasonic pulses in

conente

BS

68

Glosmry

of terms

used in

non destructive testing

Part 4 Uttnronic flmdetaction

BS

6100

Giorsary

of buildingand civil snginssrinp terms

Part6

Cbncrete

and alartsr

Referred

to in the

foreword

onlv.

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7/8

BS 1881 :

art 209

: 1990

This Brit* Ston&rd. having baenprepad

under

?he d i m i o n of

the Canmt Gypsum, Agpngrnr and Quarry ProductrStandirds

Policy Committss, war publish& under ths authority of the B o d

o fM and come inta

ffw

on 3 Apri l

1800

British Sttindads Institution,

1990

ISBN 680 17926

The following BSI rsfsrances relate t o he work on this standard:

Committee &rsncs CAB14

Oreft

for

comment

88110608

BritishStmdvds Institution . Incoroorated by Royal Charter, BSI is

the i nd mn de nt national body for the prepamtion of British

Standards.

It s

the UK member of the International Organization

for Standardiration and

UK

sponsor of the British National

Committee of the International Electrotechnical Commission.

n addition t o the preparation and promulgation o f standards, BSI

offers specialist services including

the

provision of information

through the BSI Library and Standardline Database; Technical Help

to Exporters; and other services. Advice can be obtained from the

Enquiry Section, 3S1. Milton Keynes MK14 6LE telephone

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166 telex 825777.

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subsists

in

all BSI ~ublications.No part of this publication may

be

reproduced in any form without the pr ior permission in writ ing of

BSI. This doer no t preclude the free use. in the course of

implementing

the

standard, of mecss~arydetsils such as

symbols

and

size type or grade designations. Enquiries should

be

addressed to

tho Publications Manager. BSI, L infordWood Milto n Keynes

MK14

6LE.

The number

for

telephone enquiries is 0908 220022

and for telex 825777.

bntrm

equirainen .

A

British Standard d a s not purport to

include a11 the nscesrary provisions of a cantract. Users of British

Standards are rewonsible for their correct applicat ion.

Revision

of

British

Stanbrdr.

British Standards are revised, when

necessary. by the issue either

of

amendments or o f revised edirions.

t

s important

that

umm

of

Brit*

Strndwdn

should ua r t a i n

t mt

they are in polfs aion of the lasest amendments or uiitions

Autommtic updating sonice. BSI provides an economic, individua l

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the m atter may be investigated and appropr iate action taken.

Committees responsiblefor this BritishStandard

The

prepention of this British Standardwar entrusted by the

Cement Gypsum, Aggrsgates and Quarry Products Standards

Policy Committee (CAB/-)

to Technicel

Committee CA /4,

upon which the following bodies were repnrentsd:

Association o f Lightwsi& t ggregate Manufscturers

Aslociation of Metropolitan Authorities

Association of Quality P u l m r i d

Fuel

Ash

Supplism

British Ag~rsgste onstruction Materials Industrias

Br it ih Csmant Association

British Civil EngineeringTart Equipment Manufacturers'

A m i a t i o n

British

P m t

oncrete F&ration

British Ready Mixad Concrete Association

Building Ernploysrr' Confaderation

Csmsnt Admixtures Association

Camentitiour Slag Makers' Association

Concrete Society

County Surwyors' Society

Department of th e Environment (Building Research

EstaMishmmtl

Amendments

issued

since publication

Department o f the Environment

(Property

Services

Agency)

Department of Transport

Department o f Transport (Transport and Road Research

Laboratory)

Elec trici ty S uvply Industry i n England and Walas

Federation o f Civ il Engineering Contractors

lnst ituta o f Concrete Technology

Institution

of

Civil Engineers

Inst itu tion o f H i p hw s and Transportation

Insti tutio n of Structural Enginem

Institution

of

Water and Environmental Manwement tlWEM l

Royal lnstitution

of

Charterad Surveyors

Sand and Gram Associstion

Soc i e t y o f Chemical Industry

The fo llowing bodiesware

aim

represented in

tha

drafting of tho

standard,

through sub-cornmitrees

and

panels:

British Nuclear Fuels i i m i n d

United Kingdom Atomic E m rw Authority

.

Amd. No.

Date

of issue Text affected

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Standards Insti tut ion

2

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Street

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BS

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