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Service Life Prediction for Concrete Pavements and Bridge Decks Exposed to

Sulfate Attack and Freeze-!a" Deterioration# $olume %%& ec!nical Basis for

C'(CL%FE& Sorptivit) esting and Computer *odels

Dale P+ Bentz

C!iara F+ Ferraris

,o!n inpigler

Building and Fire .esearc! La/orator)

(ational %nstitute of Standards and ec!nolog)

0ait!ers/urg# *D 12344

ABS.AC

This report provides the technical background for the CONCLIFE software package developed atthe National Institute of Standards and Technology CONCLIFE esti!ates the service life ofconcrete pave!ents and bridge decks e"posed to sulfate attack and free#e$thaw deterioration%

where the !a&or transport !echanis! for water and sulfate ion ingress is sorption by partiallysaturated concrete This report supple!ents the CONCLIFE 'ser(s )uide by providing detailson the laboratory testing to evaluate the sorptivity of concrete cylindrical cores obtained fro!field speci!ens and the three underlying co!puter !odels used by CONCLIFE in obtainingservice life esti!ates This report is volu!e II of a two*part series +olu!e I is the user(s!anual for the developed CONCLIFE software package

,eywords- building technology% concrete bridge decks% concrete pave!ents% environ!entalconditions% free#e*thaw deterioration% service life% sorptivity% sulfate attack

i


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L%S 'F F%0#igure 3$ Comparison of sorption measured 'y capillary and 'y ponding. - The /ater content

per surface area versus linear time as measured) the /ater content per surface area vs.suare root of time for the first * hours. 2@

#igure 4$ Schematic of the capillary sorption test. 22#igure "$ Schematic of the ponding sorption test. 22#igure +$ ictures of o'served leas /ith the incorrect tape. - the /ater is leaing 'et/een the

t/o layer of tape) the /ater has leaed in 'et/een the tape and the specimen sides and is/etting the 'ottom non tested surface. 24

#igure *$ Calculation of the sorption coefficient. 26#igure 8. asic configuratins of one&dimensional heat transfer models for concrete pavements

and 'ridge decs. 27ST.

*%@ 5

7F8A-?39

3ate 6$4$>>*ixture Proportions

Ce!ent kg$!6Alb$yd6B 4


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Ta'le 3$ 9i; design and concrete properties for the specimens from the 9issouri =:T. -ll thedata /ere provided 'y the =:T and /ere not remeasured at >7ST.

.oute ?>

7F8A-5>1;5>=9

.oute 56

7F8A-5>69

3ate cast @$@@ @$@@3ate Core taken @8$4@ A9??B 4:2 A946BFly /sh kg$!6Alb$yd6B :2 A?>4 A2??B 84> A2@6?B;ater kg$!6Alb$yd6B 246 A4@8B ?? A29?B

;$c! @6< @6:/d!i"tures /E/ A86 L$!6BConcrete Properties

Slu!p !! AinB 6@: A24B A99:B 28:/ir content AHB :@ 94

Concrete te!perature C AFB 48 A?@B 4? A?4B

Curing In situS!ipped and furt!er curing Shipped in plastic bagsD received by

NIST on ?$4$@@D /t NIST% thespeci!ens were stored in li!ewater

until testing


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Ta'le 4$ 9i; design and concrete properties for the specimens from the Rhode 7sland =:T. -llthe data /ere provided 'y the =:T and /ere not remeasured at >7ST.

*%@ 5

7F8A-5>29

3ate cast


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1+1 *et!odolog) Development

2.2.1 Conditioning of the Specimens

To develop a laboratory test to !easure sorptivity% two !ain hurdles needed to be overco!e-

2B the conditioning of the speci!enD and 4B the test itself/s the sorptivity depends strongly on the water saturation of the concrete% the conditioning of

the speci!en is para!ount Therefore% the reuire!ents for a good conditioning procedure forthe speci!ens should include-

Euilibriu! with the sa!e relative hu!idity should be achieved with any concreteD The relative hu!idity A1.B in euilibriu! with the speci!en should be around


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T8- the speci!en was kept in the environ!ental cha!ber until it achieved constant !ass butthe te!perature of the cha!ber was changed to 4@ C

Figure 2shows the results obtained Each result represented on the bar chart is the averageof two speci!ens The bars show the influence of the !i"ture design on the final 1. achieved%

while the line plot shows the average for all speci!ens in any !i"ture design for a givenconditioning The goal is to obtain the conditioning that results in the s!allest variation betweenthe speci!ens It is clear that the conditioning fro! T6 and higher are acceptable% with theune"plained e"ception of T9 Therefore% we suggest that the speci!ens should be kept in theenviron!ental cha!ber for at least 9? h prior to place!ent in the container to euilibrate the 1.Of course the s!allest variation between speci!ens is obtained when constant !ass is achievedAconditions T< and T8B% but the duration of the conditioning is not acceptable for a standard test

30

40

50

60

70

80

90

100

T1 T2 T3 T4 T5 T6 T7

Type of Conditioning

RHachieved[%]

0

10

20

30

40

50

6070

80

90

RHachievedforaverage

[%]

72-A/B72-C72-D/E72-F

68Overall average

#igure 1$ Relative %umidity achieved after the various pre&conditionings. The main difference is

the duration spent in the environmental cham'er at "0 C and 80( R%. T1$ no time) T2$ 24h)T3$ 48 h) T4$ 3 d) T"$ *d) T+$ until constant mass) T*$ until constant mass at 20 C and 80( R%.

The right scale is not identical to the left scale for 'etter visualiation of the average curve.

The second step that needs to be addressed is the duration of the conditioning of thespeci!en in a closed container to obtain a unifor! 1. throughout the speci!en To deter!inethe shortest duration needed% speci!ens were placed in special containers These containerswere wide !outh &ars with a !etal lid The !outh of the &ars was wide enough to acco!!odate

the place!ent of the speci!en inside the &ar Two valves were attached to the lid These valvesopen only when a !ale connection is attached to the! / dew point hygro!eter was used to!easure the 1. inside the &ars It was connected regularly to each &ar through the one wayvalves in the lids of the &ars The 1. was !onitored once a day for at least two weeks Figure 4shows the evolution of the 1. versus ti!e It can be deduced that after about 2@ days the 1.does not changes significantly Therefore% the duration adopted was 2: days to guarantee aunifor! 1. throughout the speci!en

>


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30

40

50

60

70

80

0 10 20 30

Time [days]

RH

[%

#igure 2$ R% of the air inside the conditioning ,ars versus time.

2.2.2 Sorptivity Test

;ater ingress into a non*saturated concrete structure is due to sorption% driven bycapillary forcesA6B If the water is on top of the concrete surface% gravity also will play a role inthe water penetration Figure 6shows the different results obtained with the two !ethods-capillary Aagainst gravityB or ponding Awith gravityB It is clear that the speci!ens have a higherwater intake by ponding than by capillary transport alone Therefore% it is necessary to use the!ethod !ore appropriate for the application of the concrete structure to be evaluated Thedeter!ined sorptivity coefficients are @9>2@*6!$s for the capillary sorption and @:>2@*6!$sfor the ponding sorption for the data presented in figure 6

To !easure the sorption coefficient of concrete% a new test proposed by NIST to /ST7 forstandardi#ation was usedA4B The !ethod is si!ilar to that recently published as a 1ILE7reco!!endationA


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0.00

0.10

0.20

0.30

0.40

0.50

0.60

0 1 2 3 4 5

Time [days]

Mass/surfa

ce[m]

Capillary

Ponding

A

0.00

0.04

0.08

0.12

0.16

0.20

0 50 100 150

Time [s/!]

Mass/surface[m]

Capillary

ponding B

#igure 3$ Comparison of sorption measured 'y capillary and 'y ponding. - The /ater content

per surface area versus linear time as measured) the /ater content per surface area vs.

suare root of time for the first * hours.

The proposed standard test allows either the top surface to be in contact Asi!ulation ofwater on a pave!ent or bridge deckB or the botto! surface Asubstrate in contact with waterB Thefirst case is referred to as ponding sorption and the second as capillary sorption

The concrete speci!ens were :@ !! A4 inB thick disks sliced fro! the receivedspeci!ens The sides were covered with duct tape prior to the pre*conditioning% in order to treat

all speci!ens eually prior to the initial vacuu! saturation procedure used in this study ycontrast% in the draft /ST7 standard provided in the /ppendi"% the speci!ens are sealed AtapedBafter the pre*conditioning and &ust prior to actual testing This should so!ewhat reduce the ti!enecessary to reach !oisture euilibriu! within the speci!en

In both cases% the surface not tested was covered with a plastic wrap secured with arubber band or an euivalent syste! In the case of capillary sorption AFigure 9B the speci!enswere then ready for testing For ponding sorption% so!e duct tape was used to for! a pool AdikeB

22


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as shown in Figure : / two*co!ponent epo"y caulk was used to seal the space between the tapeand the concrete

The !ass of the speci!en was then regularly !easured after the tested surface was patteddry Of course% in the case of ponding% the water inside the dike needed to be poured out before

patting dry the surface

#igure 4$ Schematic of the capillary sorption test.

#igure "$ Schematic of the ponding sorption test.

It should be !entioned that the tape used in these tests needs to be evaluated to avoidleaks These leaks will be deleterious to obtaining correct results% especially in the pondingconfiguration Figure


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In general% if the tape is not adeuate% the leaks will appear in less than 49 h It would have been!ore scientific to develop a clear criteria for deter!ining the stickinessG of the tape% but it wasbeyond the scope of this pro&ect So!e valuable infor!ation on selecting an appropriate tape canbe found in a guide to tapes for use in backpackingA8B

A

B

#igure +$ ictures of o'served leas /ith the incorrect tape. - the /ater is leaing 'et/een the

t/o layer of tape) the /ater has leaed in 'et/een the tape and the specimen sides and is/etting the 'ottom non tested surface.

To deter!ine the sorption coefficient% the !ass gain divided by the surface area of the topsurface is plotted versus the e"posure ti!e The sorption coefficients are defined as shown in thefollowing euation-

@7tS-

@+=

A2B

where; J !ass gain AkgB/J surface are tested K!4

t J ti!e variable K!inS J early age sorption coefficient K!!$!in2$4 if 2 !in M t M 8 hlater age sorption coefficient K!!$!in2$4 if t 2 d

I@J initial sorption A!!B J density of water Akg$!6B

Figure 8shows these two slopes or sorption coefficients Two slopes have been observed for theresults obtained fro! a wide variety of concretes and !ortarsA?B The later age sorption

26


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2.2.4 Standardiation !fforts

ased on previous drafts prepared by 0rof 3oug .ooton of the 'niversity of Toronto% thesorption coefficient test was updated and presented to /ST7 Co!!ittee C@>A4B The first ballothas been co!pleted and the co!!ents fro! the co!!ittee !e!bers have been introduced into arevised draft This revised draft Aprovided in /ppendi" /B was sent for discussion to the!e!bers% prior to the Pune 4@@2 !eeting / precision and bias state!ent is currently beingdeveloped and will be presented at the 3ece!ber 4@@2 /ST7 C@> !eeting for balloting

2:


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2


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C8APE. 6& C'*P


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#igure 8. asic configuratins of one&dimensional heat transfer models for concrete pavements

and 'ridge decs.

Ta'le *. ?eneric mterial properties for the heat transfer model.

*aterial 8eat Capacit)

7,;7kg oC99

!ermal Conductivit)

7;7moC99

Densit)

7kg;m69

Concrete 2@@@ 2: 46:@Soil ?@@ @6 2


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where vwindis the !easured wind speed in !$s For radiation absorbed fro! the inco!ingsunlight% the heat flow contribution is given by-

inca'ssun AA Q= A:B

where incis the incident solar radiation fro! the T754 datafile A;$!4B and absis the solar

absorptivity of the concrete Adefault value of @


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the year% vs 99? for ,ansas CityB These wetting and free#ing event files are then used in theconcrete service life !odels to be described ne"t

#igure 5. Temperature predictions for a concrete pavement in rovidence6 Rhode 7sland in the

spring. Time indicates cumulative hours from 'eginning of year.

4@

-10-5

0

5

10

15

20

25

30

35

2900 2950 3000 3050 3100

Time %h&

Temperature%C&

Ambie!

"#r$a%e

De&'(i!


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#igure 10. lots of /etting events in top ansas City6 9: and 'ottom rovidence6 R76 'othfor concrete pavements.

6+1 Sulfate Attack

The service life !odel for sulfate attack is based on the !odel developed by /tkinson and.earneA2


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whereCEJ concentration of reacted sulfate as ettringite A!ol$!6BE J 5oung(s !odulus A)0aB=spallJ concrete spalling depth A!BW J roughness factor for fracture path Adefault value of oneB

X J linear strain caused by reaction of sulfate ions to for! one !ole of ettringite A!6

$!ol% defaultvalue of 2?Q2@*


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subseuent cracking developed due to cyclic free#ing and thawing is not considered Criticalpara!eters are the porosity and air void content of the concrete and its sorption characteristicsTo i!ple!ent this !odel in the CONCLIFE progra!% each wetting event is e"a!ined in turn Ifthe duration of the wetting event e"ceeds the nick*point ti!e% the penetration depth is co!putedbased on the sorption coefficients and the concrete porosity The sorption occurring after the

nick*point ti!e is used to update the saturation of the air voids within this penetration depth Ifthe saturation at so!e depth is greater than the user*specified critical saturation% spalling occursOnce again% when the cu!ulative spalling e"ceeds the user*specified failure criteria% an esti!ateof the concrete service life is achieved This !odel co!prises the second !ain user screenwithin the CONCLIFE progra!A2B

46


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49


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C8APE. =& S


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AC('LED0E*E(S

The authors would like to thank the four state 3epart!ents of Transportation for providingconcrete core sa!ples for this study They would also like to thank 7ark Felag of the 1hodeIsland 3epart!ent of Transportation for useful discussions% 3r )eorge ;alton of F1L for

useful discussions concerning the concrete heat transfer !odel% and 0rof 3oug .ooton of the'niversity of Toronto for providing an advanced draft of the proposed sorptivity test standardwhich greatly e"pedited the process of preparing a test for balloting by /ST7 C@>

4


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.EFE.E(CES

A2B Ehlen% 7/% and ent#% 30% Service Life 0rediction for Concrete 0ave!ents andridge 3ecks E"posed to Sulfate /ttack and Free#e*Thaw 3eterioration +olu!e I-CONCLIFE 'ser(s 7anual%G F.;/ report% 4@@2

A4B /ST7 draft sorptivity testA6B ent#% 30% Clifton% P1% Ferraris% CF% and )arboc#i% EP% Transport 0roperties and3urability of Concrete- Literature 1eview and 1esearch 0lan%G NISTI1 ?64>% 'S3epart!ent of Co!!erce% Septe!ber 2>>>

A9B /ST7 C42:% Standard Test 7ethod for Funda!ental Transverse% Longitudinal% andTorsional 1esonant Freuencies of Concrete Speci!ens%G /ST7 C42:*>8% +ol @9@4%2>>>

A:B /ST7 C24@4% /ST7 C24@4* % +ol @9@4% 2>>>A>>

A8B .owe% S% The )reat Tape Off%G ackpacker% +ol 4> A2>@*?B% :>% 4@@@A?B 7artys% N% and Ferraris% CF% Capillary Transport in 7ortars and Concretes%G Ce!entand Concrete 1esearch% +ol 48 A:B% 898*8>8

A>B ent#% 30% / Co!puter 7odel to 0redict the Surface Te!perature and Ti!e*of*;etnessof Concrete 0ave!ents and ridge 3ecks% NISTI1 ?>>5% 'S 3epart!ent of Co!!erce%/ugust 4@@@

A2@B ent#% 30% Ehlen% 7/% Ferraris% CF% and )arboc#i% EP% Sorptivity*ased Service Life0redictions for Concrete 0ave!ents% 8thInternational Conference on Concrete 0ave!ents%Orlando% FL% Septe!ber 4@@2

A22B ;alton% )N% Ther!al /nalysis 1esearch 0rogra!* 1eference 7anual% NSI136-1?>>%'S 3epart!ent of Co!!erce% 7arch 2>?6% 'pdate 2>?:

A24B 7cCullough% F% and 1as!ussen% 1O% Fast*Track 0aving- Concrete Te!peratureControl and Traffic Opening Criteria for onded Concrete Overlays% +olu!e 2- Final1eport% F8A-.D-43-5?:% Federal .ighway /d!inistration% 2>>8

A26B 7arion% ;% and 'rban% ,% 'ser(s 7anual for T754s* Typical 7eteorological 5ears%National 1enewable Energy Laboratory% Pune 2>>:

A29B Schlangen% E% Online .elp$7anual !odule .E/T of FE77/SSE% 2>>@*4@@@%FE77/SSE bv% The Netherlands% 4@@@

A2:B .ol!an% P0% .eat Transfer A7c)raw*.ill ook Co!pany% New 5ork% 2>?2BA2


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4?


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large e"tent of the penetrability of the pore syste! In unsaturated concrete% the rate of ingress of

water or other liuids is largely controlled by capillary rise absorption This !ethod is based on

that developed by .all A6B who called the pheno!enon water sorptivityG

64 The water absorption of the concrete or !ortar surface varies with AaB concrete !i"ture

proportions including the addition of che!ical ad!i"tures and supple!entary ce!entitious

!aterials% AbB surface finishing% AcB entrained air content% AdB type and duration of curing% AeB age%

AfB degree of hydration% and AgB surface treat!ents such as sealers% for! oil% etc /lso% the water

absorption is strongly affected by the !oisture condition of the concrete tested

66 In general% the e"posed surface of concrete !ay be different in absorption fro! theinterior The surface is the area e"posed to the !ost potentially adverse conditions This test

!ethod can !easure the water absorption rate both of the concrete surface and of the interior

The speci!en can be a section of a core taken at different depths fro! the surface

69 This !ethod is different fro! the test described in /ST7 C?>% pp :2*


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94 Support 3evice * 1ods% pins% or other devices% !ade of !aterials resistant to corrosion

by water or alkaline solutions% which allow free access of water to the test surface of the test

speci!en during the test /lternately% the sa!ple can be supported on several layers of blotting

paper or filter papers with a total thickness of at least 2 !!

96 Top*pan alance * with sufficient capacity for the test speci!ens and accurate to at

least @2 g The balance should co!ply with /ST7 C2@@:

99 Ti!ing 3evice* Stop watch or other suitable ti!ing device accurate to 2 s

9: Tissue 0aper or Cloths * for wiping e"cess water fro! speci!en surfaces

9< Environ!ental Cha!ber * the cha!ber should have a fan and should be able to

!aintain a te!perature of :@ [ 4C and a relative hu!idity at ?@H 6 H /lternatively% an oven

able to !aintain a te!perature of :@ [ 4C and a dessicator can be used The relative hu!idity

A1.B is controlled in the dessicator with a salt solution of potassiu! bro!ide The dessicator

needs to be large enough to contain the speci!ens to be tested

98 0olyethylene Storage Container * with sealable lid% which is large enough to contain a

test speci!en The container should not have a volu!e larger than : ti!es the speci!en volu!e

/n option for the container could be to have lock valves in the lid that could be connected to a

syste! to !easure the 1. inside the container

>+ .eagents and *aterials

:2 0otassiu! bro!ide% reagent grade ANote 2B

Note 2- Only reuired if the oven$dessicator described in 9< is used

62


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?+ est Specimens


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relative hu!idities of :@ to 8@H This is si!ilar to the relative hu!idities found in field

structures A9%:B

89 Store the speci!en in the desiccator &ar or a sealable polyethylene container until test

3+ Procedure

?2 Conduct the absorption procedure in ?< to ?> at 46 [ 4C with tap water conditioned

to the sa!e te!perature If the e"peri!ent is continued for !ore than 6 days% saturated li!ewater

shall be used instead of tap water The li!ewater shall be prepared by dissolving sufficient

calciu! hydro"ide ACaAO.B4B in distilled water to e"ceed the saturation concentration A2% No 4%3ec 2>>8% pp :>*>?% pp ::2*::


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?


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#igure 12. Schematic of rocedure .

4+ Calculations

>2 The initial rate of absorption% I% is the change in !ass AgB divided by both the cross*

sectional area of the test speci!en A!!4B and the density of water at the te!perature recorded

ANote 8B

Note 8 The density of water depends on its te!perature .owever% the effect of this

variation with the te!perature is not significant in this procedure% so the te!perature

!easure!ent is not reuired The density of the water could be assu!ed to be 2@@ g$!L

A@@@2 g$!!6B

>4 The initial water absorption A!!$!in\B is defined as the slope of the line of I plotted

against the suare root of ti!e A!in\B Obtain this slope after using least*suares% linear

regression to establish the plot of I vs ti!e\ 3o not include the origin A!easure!ent at 2 !inB

as a datu! point ANote 8B 'se all the points in the regression until the plot shows a clear change

of slope If no portion of the curve I vs ti!e\data is linear Aa regression coefficient of less than

@>?B and the data show so!e syste!atic curvature% absorption cannot be deter!ined /n

e"a!ple is given in the /ppendi"

Note ? % The initial change in !ass up to one !inute is often higher than for subseuent

ti!e intervals in part because it corresponds to water absorbed on the outer surface in

contact with the water and not absorbed inside the speci!en Ain the poresB

6


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>6 Obtain the water absorption at later age Aafter the line plotted in >4 shows a change

in slopeB using least*suares% linear regression to deter!ine the slope of the second portion of the

plotted points for I vs ti!e\ Include only points for ti!es fro! 2 day to 8 days If no portion of

the curve I vs ti!e\data is linear Aa regression coefficient of less than @>?B and shows so!e

syste!atic curvature in the region% absorption at later age cannot be deter!ined

52+ .eport

2@2 /n e"a!ple report is given in the /ppendi" 2

2@4 1eport the following-

2@42 3ate sa!pled or date castD

2@44 Source of sa!pleD

2@46 1elevant background infor!ation on sa!ple such as !i"ture proportions% curing

history% type of finishing% and age% if availableD

2@49 3i!ensions and dry !ass of the test speci!enD

2@4: / plot of the absorption vs suare root of ti!eD

2@4< The average initial water absorption calculated to @2 !!$!in\ and the

individual absorption rates for the two speci!ens

2@48 If the initial water absorption could not be derived fro! all the data points as

discussed in >4% indicate which data points are o!itted

2@4? 1eport the ti!e AhoursB at which the slope of the linechanges

2@4> The average later age water absorption calculated to @2 !!$!in\and the

individual absorption rates of the two speci!ens tested

2@42@ If the later age water absorption could not be derived fro! all the data points

as discussed in >6% indicate which data points were o!itted

68


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55+ Precision and Bias

222 0recision * The precision of this procedure has not yet been deter!ined

224 ias * Since there is no accepted reference !aterial suitable for deter!ining the bias of

this procedure% no state!ent on bias is !ade

,eywords- rate of absorption% initial water absorption% concrete% !ortar% per!eability

6?


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APPE(D%@ 5&Example .ate of A/sorption est

Cast 3ate- 6$4$>> Test 3ate- 6$29$@@

Sa!ple No F*


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0.00

0.05

0.10

0.15

0.20

0.25

0.30

0 20 40 60 80 100 120

Time [min/!]

Mass/are

a[mm]

day

E'/TION OF LINE-

Initial /bsorptionI J S t ] b Apoints !easured during the first day are used% e"cluding the point at originB

S J 4?

Later age /bsorptionI J S t ] b Apoints !easured after the first day are usedB

S J @?88 " 2@

*6

!!$

!in b J @22 " 2@

*4

r J @>?

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