Lab Report 1 _ce13b014_ce13b015

7/24/2019 Lab Report 1 _ce13b014_ce13b015

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1. REBOUND HA##ER AND PULSE

VELOCITY ON CONCRETE CUBESRebound Hammer:INTRODUCTION: Rebound Hammer Test is performed on concrete tubes to nd

out their compressive strength using the Schmidt Rebound Hammer as per IS :

!! "#art $% & ''$ and "(ST) C *+,-.'%/ 0/ This device is universa112 used

because of a hardened stee1 hammer impacted on the concrete b2 a spring/The

under12ing princip1e of rebound test is that the hammer measures the rebound of

a spring-1oaded mass impacting against the surface of the samp1e/The rebound

of an e1astic mass depends on the hardness of the surface against 3hich its mass

stri4es/5hen the p1unger of the rebound hammer is pressed against the surface

of the concrete6 the spring-contro11ed mass rebounds and the e7tent of such arebound depends upon the surface hardness of the concrete/ The surface

hardness and therefore the rebound is ta4en to be re1ated to the compressive

strength of the concrete/ The rebound va1ue is read from a graduated sca1e and

is designated as the rebound number or rebound inde7/ The compressive

strength can be read direct12 from the graph provided on the bod2 of the

hammer/ Schmidt rebound hammer is that it is usefu1 in assessing concrete

uniformit2 and in comparing one concrete against another6 but can on12 be used

as a rough indication of concrete strength in abso1ute terms

#ROC8DUR8:

/ 9efore commencement of the test ca1ibrate the hammer on an anvi1 given b2the manufacturer/

$/ Set the instrument into mode "that is in strain energ2 mode% before thestart/

!/ (pp12 1ight pressure on the p1unger so that it gets re1eased from the 1oc4edposition and a11o3 it to e7tend to the read2 position for the test/

;/ #1ace the p1unger perpendicu1ar to the surface of the concrete and gradua112app12 pressure unti1 the hammer impacts/

,/ Ta4e ! readings at di8?(NT ST(ND(RDS:Impact 8nerg2 for Rebound Hammer for di


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impact sensitive concrete

! )ass concrete 1i4e roads6air e1dsetc

!+

PULSE VELOCITY ON CONCRETE CUBES with varin! "oad:

INTRODUCTION: (n u1trasonic pu1se ve1ocit2 test is an in situ6 non destructivetest6 to determine the @ua1it2 of concrete or masonr2 or roc4s/ the strength of

an2 materia1 is determined b2 measuring the ve1ocit2 of the u1trasonic pu1se

3ave passed through it/ This e@uipment gives the time e1apsed for the pu1se to

pass through it and higher ve1ocities gives us an pre1iminar2 idea of the

homogeneit2 of the obAect/

P$%&'()$':

1. U1trasonic test e@uipment consists of e1ectronic circuit 3hich generates

pu1se and a transducer converts e1ectrica1 signa1 into mechanica1 signa1

having osci11ating fre@uenc2 in the range of ;+ 4HB to ,+ 4HB/. Set reference: ( reference bar is provided to chec4 the instrument Bero/

The pu1se time for the bar is engraved on it/ (pp12 a smear of grease to

the transducer faces before p1acing it on the opposite ends of the bar/

(dAust the S8T R8E contro1 unti1 the reference bar transit time is obtained

on the instrument read-out/3. Range se1ection: or ma7imum accurac26 it is recommended that the +/

microsecond range be se1ected for path 1ength upto ;++mm/4. #u1se ve1ocit2: (pp12 coup1ant to the surfaces of the transducers and press

it hard onto the surface of the materia1/ Do not move the transducers

3hi1e a reading is being ta4en6 as this can generate noise signa1s anderrors in measurements/ Continue ho1ding the transducers onto the


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surface of the materia1 unti1 a consistent reading appears on the disp1a26

3hich is the time in microsecond for the u1trasonic pu1se to trave1 the

distance >E/ The mean va1ue of the disp1a2 readings shou1d be ta4en 3hen

the units digit hunts bet3een t3o va1ues/5. Separation of transducer 1eads: It is advisab1e to prevent the t3o

transducer 1eads from coming into c1ose contact 3ith each other 3hen thetransit time measurements are being ta4en/ If this is not done6 the

receiver 1ead might pic4-up un3anted signa1s from the transmitter 1ead

and this 3ou1d resu1t in an incorrect disp1a2 of the transit time/". R'*'+, the e7periment 3ith var2ing the 1oad on cubes unti1 fai1ure/

ST(ND(RDS:

EPERI#ENTAL SETUP:

The concrete cube of $, cm 7 $, cm 7 $, cm 3ere casted specia112 for the testand the cubes 3ere tested in a compression machine/


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Schmidt Rebound Hammer U1trasonic #u1se ?e1ocit2apparatus

OBSERVATIONS:

group .:

Rebound Hammer"%

>oad"in 4N% U#?"Fs% ?e1ocit2 "mGs% Side Side$

$/. !+/' ;*,; $=/, $'/, $; $*/, $* $*

100 31.4 4777

200 30.9 4854 23 27.5 20.5 20.5 29.5 26


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300 31.1 4823

400 31.4 4777 24.5 30.5 29.5 24.5 30 23

500 33.4 4491

600 35.9 4178 35 32 29.5 23.5 32.5 27

#ISCUSSIONS:

The va1ues from U#? sho3 that the ve1ocit2 reduces as the 1oad increases6theve1ocities for a11 e7cept one are greater than ;/,4mGs 3hich means concrete@ua1it2 is e7ce11ent/

The rebound hammer va1ues range from 1o3est of $+/, 3hich corresponds to$+++psi and to ma7imum of !, 3hich corresponds to ;,++psi/The huge variation

ma2 be due ta4ing readings at same point repeated126improper hand1ing of theinstrument/The va1ues of rebound hammer did not c1ear fo11o3 an2 pattern but itcan seen there is an increase in the na1 va1ues 3hich sho3s that the reboundhammer test is not comp1ete12 re1iab1e/

;/)8(SUR8)8NT O D8#TH 9 I)#(CT

8CHOI,$%()&,/%:

Impact-echo is an acoustic method for non-destructive eva1uation of concrete

and masonr2/

5e have used erman made setup containing H# 1aptop insta11ed 3ith ?i4ingsoft3areIt Aust identies and @uanties prob1ems 3ith in a structure but is not a ++Jsure shot b1ac4 bo7 3hich testies an issue inside/ItEs based on the use of impact-generated stress "sound% 3aves that propagate

through concrete and masonr2 and are reKected b2 interna1 Ka3s and e7terna1

surfaces/Impact-echo can be used to determine the 1ocation and e7tent of Ka3s

such as crac4s6 de-1aminations6 voids6 hone2combing6 and de-bonding in p1ain6

reinforced6 and post-tensioned concrete structures/It can provide thic4ness

measurements of concrete s1abs 3ith an accurac2 better than three percent6 and

it can 1ocate voids in the subgrade direct12 beneath s1abs and pavements/ The

method can be used to determine thic4ness or to 1ocate crac4s6 voids6 and other

defects in masonr2 structures 3here the bric4 or b1oc4 units are bonded together

3ith mortar/

P$/&/*':

It 3or4s on the basis of reKection of 3aves on interaction 3ith a di


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and reKected/ This reKected 3ave is caught bac4 again in receiver and the time

gap is measured 3hich gives the distance of Ka3Gother materia1 from the

transmitter based on pre-dened ca1ibrated ve1ocities in that medium/

E*'$/2',+ D'&$/*,/%:

(11 the necessar2 connections for using the ?i4ing soft3are 3as done initia112 andthen 3ith the he1p of Hammer of medium siBe is used as impact generator or

Transmitter/ On pre-mar4ed measuring points6 transducer is p1aced vertica112 to

receive the signa1 3hich is ana12sed b2 ?i4ingEs soft3are/ (fter ana12sing the

graph sho3n on the soft3are screen6 3e measure pea4s that correspond to

depths of change in medium 3hich are supposed to be crac4s6 Ka3s or

boundaries of testing specimen/

E*'$/2',+ (+,+:

S'$/+ N% $')'&6/ KH89 D/,+&'/ 229

1 .7! 31 .!3 "!43 4.3! 4"34 .7! 315 .7! 31" .7! 317 7.1 "0 ".4 !7! 7.33 7

10 .30 4511 .7! 311 .7! 31

#1ease refer to the attached image that contains the origina1 observation

data ta4en on the date of e7periment/


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R'),:

The average of a11 the depths ca1cu1ated from the observed va1ues as

!+/'mmbut the actua1 depth of beam is $,+mm/

Ho3ever6 I 3anted to discard va1ues corresponding to $/'! LHB and ;/!'

LHB as their depth measures =';mm and ;=!mm 3hich are no 3a2 near

to the practica1 rea1it2 of $,+mm/

87c1uding these $ e7perimenta1 va1ues from the observed data6


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The above sho3n gure on12 contains the summation of s@uares of

deviation of va1ues from their mean and hence the va1ue is again divided

b2 +"tota1 no of va1ues% to get the variance/

Standard deviation is obtained b2 ta4ing a s@uare root of varianceM

A;'$+ &+&)+,'( / 4"."22 ?>/&> / ;'$6 '+$ ,%

,>' +&,)+ ;+)' %= 5022.

E$$%$ @ 50-4"."950 100 1.3"@

V+$/+&' 51".4

S,+(+$( D';/+,/% .734 22

3.

C$+& D'*,> #'+)$'2', / +S,'**'( B'+2 - I(/$'&, UPV

#',>%(:I,$%()&,/%:

Surface opening crac4s often occurs in concrete structures/ The2 ma2 appear

as a conse@uence of severa1 degradation mechanisms such as repeated 1oading6

di


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a


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Indirect U#? Techni@ue has been used to measure the depth of the crac4/

(t rst 3e ca1ibrate the U#? setup

>ater the stepped beam member is c1eaned and it is ensured that the

surface on 3hich the probe is p1aced is as Kat as possib1e/

The top surface of the beam is then divided into number of interva1s/

The transmitter is then p1aced on one side of the crac4 on the top surface

and the receiver is p1aced at di


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( (E Time

ta4en"us%

Crac4

depth"cm%

8rrorJ

= . $$ $+/, !/.$/! $/* ;,/= ./;$ '/=$./= */, $.$/= ;,/$ =*/'

=/$ */, =,/; $$/$! !.$/= */, *=/ $./$, ;*/=

,/

I)#(CT 8CHO OR TH8 S>(9 5ITH

>(5SI,$%()&,/%:

Impact-echo is an acoustic method for non-destructive eva1uation of concrete

and masonr2/

5e have used erman made setup containing H# 1aptop insta11ed 3ith ?i4ingsoft3are

It Aust identies and @uanties prob1ems 3ith in a structure but is not a ++Jsure shot b1ac4 bo7 3hich testies an issue inside/ItEs based on the use of impact-generated stress "sound% 3aves that propagate

through concrete and masonr2 and are reKected b2 interna1 Ka3s and e7terna1

surfaces/Impact-echo can be used to determine the 1ocation and e7tent of Ka3s

such as crac4s6 de-1aminations6 voids6 hone2combing6 and de-bonding in p1ain6

reinforced6 and post-tensioned concrete structures/It can provide thic4ness

measurements of concrete s1abs 3ith an accurac2 better than three percent6 and

it can 1ocate voids in the subgrade direct12 beneath s1abs and pavements/ The

method can be used to determine thic4ness or to 1ocate crac4s6 voids6 and other

defects in masonr2 structures 3here the bric4 or b1oc4 units are bonded together

3ith mortar/

P$/&/*':

It 3or4s on the basis of reKection of 3aves on interaction 3ith a di


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Transmitter/ On pre-mar4ed measuring points6 transducer is p1aced vertica112 to

receive the signa1 3hich is ana12sed b2 ?i4ingEs soft3are/ (fter ana12sing the

graph sho3n on the soft3are screen6 3e measure pea4s that correspond to

depths of change in medium 3hich are supposed to be crac4s6 Ka3s or

boundaries of testing specimen/

D+,+:

I2*+&, '&>% =%$ ,>' + ?/,> F+?

D'*,>

A B C D E G H

!$ ,, !$ ;=; !$ !$ ,, !$

$ $'* !.' !$ +$ '' !$ = $.*

! !$ !.' !.' !.' $'* $'* !.' !;*

; !.' '. !$ !.' $.' $'* $'* $'*, !$ '' $'* !.' !$ !$ !.' ''

= $'* $'* $'* $'* !$ '' !.' $.*

. !.' '' !$ '' R) R) R) R)

* R) R) R) R) R) R) R) R)

R) Record)issing (11 va1uesin mm

A+6/:

?e1ocit2 in concrete s1ab is ;+.; mGs 3hich is ca1ibrated using Tomograph2/ It can

a1so be ca1ibrated using Impact 8cho )ethod ho3ever Tomograph2 3as used in

time-constraint situations/

B+'( % ,>' ;+)' %,+/'( % ,>' ?>/&> +$' &+&)+,'( =%$2

&+/$+,'( ;'%&/,6 /, / &'+$6 ';/(', ,>+, *%/, B4 B5 D D7 E

" G H5 +$' (';/+,/< =$%2 ,>' ,$'( /2*6/< ,>+, ,>'6 &%)( '

*%/, %= F+? / ,>' '+2.

?a1ues crossing !,+mm are being considered as erroneous as the beam depth is

$,+mm and this method canEt give such deviation from the actua1 va1ue/

O), %= ,>'' D G E +$' +%< ,>' +2' /' /2*6/< ,>+, ,>' &$+&

/ +%< ,>' /' %//< + ,>'' ,>$'' *%/, +, + +**$%/2+,' ('*,>

%= 10022 =$%2 )$=+&' %= 2'+)$'2',.

B4 +( B5


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=/

U1trasonic Tomograph2

I,$%()&,/%:

U1trasonic tomograph2 uses u1trasound fre@uenc2 of 3aves that gets attenuated

on interaction 3ith media change 3ith di


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R'),:

The ana12sis is to nd out the ve1ocit2 across various paths and itEs c1ear12

indicated in the tab1es/

(ctua1 ve1ocit2 of sound 3aves in concrete as measured b2 tomograph2 is ;+.;

mGs and no3 this is compared 3ith the data ana12sed from e7periment/

(verage ca1cu1ation is sho3n above in a function on 87ce1 sheet/


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On12 summation of s@uares of deviation of va1ues from their average is

ca1cu1ated here in the above 87ce1 function/ This va1ue is 1ater divided b2 !="no

of observations% to obtain the variance of data observed/ (nd 3e 4no3 the

s@uare root of variance is standard deviation/

Here are the na1 resu1ts6

$%2 ,>' &+&)+,/% ,+,'( +%;'

A;'$+


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. Set reference: ( reference bar is provided to chec4 the instrument Bero/

The pu1se time for the bar is engraved on it/ (pp12 a smear of grease to

the transducer faces before p1acing it on the opposite ends of the bar/

(dAust the S8T R8E contro1 unti1 the reference bar transit time is obtained

on the instrument read-out/

3. Range se1ection: or ma7imum accurac26 it is recommended that the +/microsecond range be se1ected for path 1ength upto ;++mm/

4. #u1se ve1ocit2: (pp12 coup1ant to the surfaces of the transducers and press

it hard onto the surface of the materia1/ Do not move the transducers

3hi1e a reading is being ta4en6 as this can generate noise signa1s and

errors in measurements/ Continue ho1ding the transducers onto the

surface of the materia1 unti1 a consistent reading appears on the disp1a26

3hich is the time in microsecond for the u1trasonic pu1se to trave1 the

distance >E/ The mean va1ue of the disp1a2 readings shou1d be ta4en 3hen

the units digit hunts bet3een t3o va1ues/

5. Separation of transducer 1eads: It is advisab1e to prevent the t3otransducer 1eads from coming into c1ose contact 3ith each other 3hen the

transit time measurements are being ta4en/ If this is not done6 the

receiver 1ead might pic4-up un3anted signa1s from the transmitter 1ead

and this 3ou1d resu1t in an incorrect disp1a2 of the transit time/

P)' ;'%&/,6P+,> 'T$+;' ,/2'9

I,'$*$',+,/% %= R'),:The @ua1it2 of concrete in terms of

uniformit26 incidence or absence of interna1 Ka3s6 crac4s and segregation6

etc6indicative of the 1eve1 of 3or4manship emp1o2ed6 can thus be assessed using

the guide1ines given be1o36 3hich have been evo1ved for characteriBing the

@ua1it2 of concrete in structures in terms of the u1trasonic pu1se ve1ocit2/


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E*'$/2',+ D'&$/*,/% +( %'$;+,/%: this method is done b2 three

methods i/e direct 6indirect6semi direct methods/

U1trasonic pu1se ve1ocit2 e@uipment is used in the stepped beams b2 direct

method/"group %/

U1trasonic pu1se

ve1ocit2 e@uipment is used in the stepped beams b2 direct 6in direct6semi direct

method/"group .%/

DIRECT #ETHOD:

#oint

s

Time"microsecon

d%

5idth of

specimen"cm%

ve1ocit2"LmG

s%

9 +/. ;= ;/,$

9$ +$ ;= ;/,+

9! +$ ;= ;/,+

C !/* = ;/=$

C$ !$/. = ;/,'

C! !$/, = ;/=+

D =, .= ;/=+

D$ =;/! .= ;/=$

D! =,/! .= ;/,'


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Time"micro second% Distance bG3 transducer and receiver ?e1ocit2"LmGs%, !;/$ ;/!*, !!/! ;/,, !!/, ;/;..

S'2/ (/$'&, 2',>%(:

Time"microsecond%

5idth of specimen"cm% ?e1ocit2"LmGs%

=/.; !, ;/.*!$/, =./, ;/*;'/, +=/, ;/=,

N%,': T>' (/,+&' '

+&,)+ (/,+&' ',?'' ,>' ,$+2/,,'$ +( $'&'/;'$ *%/, ,>+, /&+&)+,'( =$%2 ,>' $/, +' ' +(

,>/&' %= ,>' '+2.>'&' /, &+ ' (/$'&,6 )'( =%$ ,>' &+&)+,/%

%= *)' ;'%&/,6.

I (/$'&, 2',>%(:

Time"microsecond% Distance bG3 transducer and receiver ?e1ocit2"LmGs%15 3!.5 3.30 !7. 3.145 151.7 .!7


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R'), +( I='$'&':

rom the observed data6 3e got pu1se ve1ocit2 around ;/, LmGs to ;/. LmGs6

3hich is an indication of good @ua1it2 of concrete on stepped beams/"group %/

This te11s us that the concrete is having good strength/

9ut 3e got di


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Lab Report 1 _ce13b014_ce13b015

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