A NEW TESTING METHOD FOR CREEP BEHAVIOR OF SELF-COMPACTING CONCRETE AT EARLY AGE

Transcription

1 A NEW TESTING METHOD FOR CREEP BEHAVIOR OF SELF-COMPACTING CONCRETE AT EARLY AGE Krittiya Kawman A dissrtation submittd to Kochi Univrsity of Tchnology in partial fulfillmnt of th rquirmnts for Th Dgr of Mastr of Enginring Suprvisor Profssor Hajim Okamura Dpartmnt of Infrastructur Systm Enginring Kochi Univrsity of Tchnology Kochi, Japan January 2001

2 Abstract Crp and shrinkag of concrt ar known to hav significant ffcts at arly ag of concrt. To b abl to simulat th bhavior of crp and shrinkag during this stag, accurat and actual proprtis of concrt should b obtaind from th tst. Howvr, by prforming normal crp tsting, applying constant dad load to spcimn, som important and ncssary paramtrs cannot b obtaind. Furthrmor, crp also has significant ffcts on loss of prstrss. Such normal tst cannot clarly xplain this kind of bhavior wll. Thrfor, a nw tsting mthod for crp tst is proposd. From this tsting mthod, th modulus of lasticity of concrt (as a function of tim) that is a usful paramtr in stimating crp and rliabl strain valu can b achivd. Concrt crp and shrinkag ar affctd by many paramtrs. Th factors invstigatd in this rsarch wr typ of cmnt, cmnt contnt and w/c ratio, ag at loading/drying, and strss/strngth ratio. Th tsts wr prformd on mortar of slfcompacting concrt. It was found that typ of cmnt has slight ffct on crp du to its diffrnc in chmical compositions. For th sam day of loading and sam strss/strngth ratio of applid load, th highr th w/c ratio th largr crp. Ag at loading also has ffct on crp such that th latr ag at loading, th smallr crp is. Strss/strngth ratio has significant ffct on crp. A nw crp factor is proposd and it is found to giv good agrmnt with th convntional trms, which ar spcific crp and crp cofficint.

3 Acknowldgmnts I would lik to xprss my dpst gratitud to my advisor Profssor Hajim Okamura for his kind ncouragmnt and valuabl advic throughout th cours of this study. I xprss my profound gratitud to Assistant Profssor Masahiro Ouchi for his guidanc spcially on slfcompacting concrt and his ncouragmnt during th cours of this study. My gratful apprciation is xtndd to Profssor Hiroshi Shima for his suggstions. It has bn an honor and a privilg to work with thm for thir outstanding xampls of scintific ddication in thir fild. Gratful acknowldgmnts ar also xtndd to Associat Profssor Chiyo Myojin and Associat Profssor Masataka Takagi for thir intrst and srving as mmbrs of xamination committ. Sincr words of gratitud ar xprssd to Mr. Masaru Uno for his usful advic and support in xprimntal work. I also would lik to thank Mr. Supakit Swatkititham and Mr. Thammanoon Dnpongpan, and Thai juniors for thir hlp, support and patinc towards many of my problms during th cours of th xprimntal work.

4 Contnts Abstract Acknowldgmnts Contnts List of Figurs and Tabls i ii iii iv 1. INTRODUCTION 1.1 Objctiv and scop of study 1 2. LITERATURE REVIEW 2.1 Dfinition of trms usd Convntional crp tst Factors affcting crp 4 3. EXPERIMENTAL OUTLINE 3.1 Mix proportions of mortar Gomtry of spcimns Stup mthod Masuring mthod for strain 8 4. ANALYSIS AND VERIFICATIONS 4.1 Analytical mthods Comprssiv strngth and Young s modulus Effct of typ of cmnt Effct of w/c ratio Effct of ag at loading Effct of strss/strngth ratio CONCLUSIONS RECOMMENDATIONS OF FURTHER STUDY 18 REFERENCES Appndix A Appndix B Appndix C Appndix D Appndix E Appndix F Total strain, shrinkag strain, and lastic strain of all spcimns Crp strain of all spcimns Young s modulus of all spcimns Spcific crp of all spcimns Crp cofficint of all spcimns Crp factor of all spcimns

5 List of Figurs and Tabls Figur No. pag Dfinition of trms Diffrnt kinds of load systms for crp tst Mixing procdur of mortar in slf-compacting concrt Gomtry of spcimns for crp and drying shrinkag tst Point gaugs and thir positions on th tst spcimn Stup mthod for crp tst Stags of crp tst Shrinkag strain vrsus tim (log scal) Crp strain vrsus tim (log scal) Modulus of lasticity vrsus tim (log scal) Elastic strain vrsus tim (log scal) Spcific crp vrsus tim (log scal) Crp cofficint vrsus tim (log scal) Crp strain and modulus of lasticity vrsus tim (log scal) Crp factor vrsus tim (log scal) Comprssiv Young s modulus Rlationship btwn comprssiv strngth and Young s modulus Effct of typ of cmnt Effct of w/c ratio Effct of ag at loading Effct of strss/strngth ratio Tabl No Spcific gravity of matrial Proprtis of mortar Mix proportion and nvironmntal condition for th ffct of typ of 13 cmnt analysis Mix proportion and nvironmntal condition for th ffct of w/c ratio 13 analysis Mix proportion and nvironmntal condition for th ffct of ag at 14 loading analysis Mix proportion and nvironmntal condition for th ffct of 15 strss/strngth ratio analysis

6 Chaptr 1 INTRODUCTION 1.1 Objctiv and scop of study Th arly ag of concrt is known to hav a significant control on th ovrall prformanc of concrt structurs. During this stag, concrt may b subjctd to svr intrnal actions du to thrmal and hygric gradints within concrt itslf and at th sam tim it may b affctd by th xtrnal conditions of nvironmnt and loading. All ths actions may lad to diffrnt dformations within th concrt that is just building its rsistanc and stiffnss. Important xampls of harmful ffcts of crp ar prstrssd concrt mmbr, whr crp causs loss of prstrss, and mass concrt structurs which undrgo a hating-cooling cycl du to th dvlopmnt of th hat of hydration and thn th tmpratur drop to th ambint tmpratur. During this cycl of tmpratur chang, crp rlivs th strss du to comprssion inducd by th initial rapid ris in tmpratur. Thus, on cooling, tnsil strss asily dvlop and cracking may asily occur. Crp and shrinkag of concrt ar known to hav significant ffct at arly ag of concrt. Thus, discussing th prformanc of this young ag concrt with spcial attntion to th shrinkag and crp and tim dpndnt dformations is of intrst by many rsarchrs. Slf-compacting concrt is a kind of concrt that can b compactd into vry cornr of a formwork, purly by mans of its own wight and without th nd for vibrating compacting. Nowadays, this typ of concrt is widly usd. Normally, in ordr to obtain high slfcompactability, th aggrgat contnt is limitd and th powdr contnt is high. Du to this high powdr contnt, crp and shrinkag of slf-compacting concrt ar significant. Th accurat and rliabl information on proprtis of concrt at arly ag is vry difficult to obtain. To b abl to simulat th bhavior of crp and shrinkag during this stag, accurat and actual proprtis of concrt should b obtaind from th tst. Howvr, by prforming normal crp tsting, applying constant dad load to spcimn, som important and ncssary paramtrs cannot b obtaind. Furthrmor, crp also has significant ffcts on loss of prstrss. Such normal tst cannot clarly xplain this kind of bhavior wll. Thrfor, a nw tsting mthod for crp tst is proposd. Th study focuss on crp of slfcompacting concrt at arly ag whr crp is thought to b significant.

7 Chaptr 2 LITERATURE REVIEW 2.1 Dfinition of trms usd Crp is dfind as a dformation occurring undr, and inducd by, a constant sustaind strss whil shrinkag is trmd changs in strain du to movmnt of watr from or to th ambint mdium whn no xtrnal strss is acting [1]. Th common practic ovr many yars has bn considr th two phnomna to b additiv. Th ovrall incras in strain of a strssd and drying mmbr is thus assumd to consist of shrinkag (qual in magnitud to that of a similar unstrssd mmbr) and of a chang in strain du to strss, i.. crp. This approach has a mrit of simplicity and is suitabl for th many practical applications whr crp and shrinkag occur togthr. Th dfinition is, howvr, not corrct bcaus crp and shrinkag ar not indpndnt phnomna to which th principl of suprposition can b applid. In fact, w know that th ffct of shrinkag on crp is to incras th magnitud of crp. Howvr, it is possibl to dfin crp as th dformation in xcss of shrinkag. Such a dfinition maks it possibl to analyz th data of prvious invstigators who blivd crp and shrinkag to b additiv. Figur shows th trms and dfinitions involvd. Figur Dfinition of trms

8 It should b notd that, sinc th modulus of lasticity of concrt incrass with tim, th lastic strain dcrass with tim. Thus, crp should b rckond as strain in xcss of th lastic strain at th tim considrd and not in xcss of th lastic strain at th tim of application of load. Howvr, this paramtr cannot b obtaind from convntional crp tsting mthod. 2.2 Convntional crp tst Th majority of crp tsts ar prformd on comprssion spcimns prisms and cylindrs subjctd to a uniaxial strss. Gnral spaking, thr ar four loading mthods: dad load, spring-loadd, hydraulic, and stabilizd hydraulic. Figur show diffrnt typs of load systms for crp tst as mntiond abov. (a) (b) (c) a) a spring-loadd crp fram b) a hydraulic load crp fram c) a stabilizd hydraulic load systm Figur Diffrnt kinds of load systms for crp tst Th dad load systm is hardly vr usd bcaus for th usual siz of spcimns it rquirs larg dad wight and is, thrfor, cumbrsom and oftn impractical. Th spring-loadd systm, on or mor havy coil springs ar hld in a comprssd position against a suitabl fram. This procdur improvs th constancy of th applid load. Th main difficultis li in th application of th propr load sufficintly rapidly so that no crp taks plac. In th hydraulic systm [2], high loads can b applid mor asily and can b maintaind to a high dgr of accuracy. This systm is compact and flxibl. Th application of th dsird load is simpl and rliabl. Howvr, th maintnanc of a sustaind load is snsitiv and oftn thr is an unavoidabl small lakag of th hydraulic fluid. Th stabilizd hydraulic loading systm [3,4,5] can b usd for a numbr of spcimns at th sam tim. This systm solvs th difficultis ncountrd in th hydraulic systm.

9 Howvr, th modulus of lasticity as a function of tim couldn t b obtaind from th abov kinds of crp tst. To b satisfactory, a loading systm for crp tsts should b abl to maintain a constant strss with a minimum of maintnanc and manual adjustmnt, and should nsur a uniform strss distribution ovr th cross-sction of th spcimn. It is also dsirabl that th loading systm b compact to mak possibl opration in a room with controlld tmpratur and humidity. 2.3 Factors affcting crp Cmnt is th most important factor in crp bcaus th hydratd cmnt past is th sourc of th phnomnon. Th influnc of cmnt is twofold: that arising from th physical and chmical proprtis of th cmnt, and that du to th variation in th amount of th hydratd cmnt past [6]. Crp sms to b invrsly proportional to th rapidly of hardning of th cmnt usd. Th mor hardnd th past th mor rigid it is and th lowr its crp potntial at a givn applid strss. Th invstigation [7] of th influnc of th typ of cmnt on crp lad to th stablishmnt of an approximat strss/strngth ratio rul, which stats simply that, for constant mix proportions and sam typ of aggrgat, crp is proportional to th applid strss and invrsly proportional to th strngth at th tim of application of th load. From a wid rag of xprimntal rsults thr xists a linar rlationship btwn crp and th applid strss, xcpt in spcimns loadd a vry arly ag: 1 to 3 days. Iriya, K., Hattori, T., and Umhara, H., [8] studid comprssiv crp at arly ag of mortar with w/c ratio of 55% by using 10x20 cm cylindrical spcimn. Th tsts wr carrid out at control tmpratur of 30 C and rlativ humidity of 100%. Th spcimns wr loadd 3 days aftr casting and kpt applying load for 5 days and thn unloadd for 3 days. Strss/strngth ratio was varid by 4.4%, 20%, 29%, 49% and 60%. From th tst, it can b concludd that final crp strain and strss/strngth ratio has linar rlationship up to strss/strngth ratio of 20%. For th strss/strngth ratio mor than 20%, th rlationship bcoms xponntial. Th quation to stimat final crp strain as a function of strss/strngth ratio is shown in Eqn. (2.3.1) ( S / S ) ε cr = ( 20 / S 60) ε = cr 11.95( S / S) ( / 20) S (2.3.1) whr ε cr is final crp strain (µ) and S/S is strss/strngth ratio (%), rspctivly. Washa and Fluck s [9] discussd th applicability of th strss/strngth ratio rul such that th chang in strngth whil th concrt is undr load, and hnc a chang in th valu of th strss/strngth ratio is a factor in crp. Lorman [10] studid th ffct of w/c ratio on crp and found that crp is approximatly proportional to th squar of th w/c ratio. Iriya, K., Hiramoto, M., Hattori, T., and Umhara, H., [11] studid comprssiv crp in concrt at arly ag. Th important factors on this crp bhavior in concrt at arly ag ar loadd ag, loadd strss lvl, and tmpratur ffcts. A crp modl which is a function of strss/strngth ratio, w/c ratio, quantity of cmnt past, loadd ag was proposd as shown in Eqn. (2.3.2). ε ( t, S / S, W / C, P, τ ) = F cr S / S ( S / S) F W / C t { (1 ) (1 ) t } ( W / C) F ( P) F ( τ ) P L (2.3.2)

10 F ( S / S, τ ) = C( ) S S ( 0 S / S 20) (2.3.3) S / S τ / D 0.035S / S ) C τ ), D( τ ) : loading ag cofficints ( (τ ( 20 S / S) C( τ ) 0.007( τ 1) ( 1 τ 3) = C( τ ) 0.001( τ 3) ( 3 τ 5) = C( τ ) = τ ) ( D( τ ) 0.069( τ 1) ( 1 τ 3) = D( τ ) 0.014( τ 3) ( 3 τ 5) = D( τ ) = τ ) ( F W C = W C 2.43 W / C ( / ) 1.69( / ) (2.3.4) F P ( P) = 1.58ln( P) 7.85 (2.3.5) 0.86τ F ( τ ) = 1.082(1 ) (2.3.6) L whr ε cr is final crp strain (x10-6 ), S/S is strss/strngth ratio (%), τ is loading ag (days), t is tim duration of loading (days), W/C is watr to cmnt ratio (%), and P is quantity of cmnt past (cm 3 / m 3 ), rspctivly. Morovr, crp is also affctd by rlativ humidity and th tmpratur of th surrounding nvironmnt, th aggrgat contnt, and th us of admixtur.

11 Chaptr 3 EXPERIMENTAL OUTLINE 3.1 Mix proportions of mortar In this rsarch, normal Portland cmnt and low hat cmnt wr usd. Fin aggrgats wr rivr sand and crushd sand. Tabl shows spcific gravity of matrials usd in this rsarch. Proprtis of mortar ar shown in Tabl Mix dsign and mixing procdur of mortar in slf-compacting concrt wr don as suggstd by Ouchi, M., Hibino, M., Ozawa, K. and Okamura, H. [12] and Ouchi, M. and Edamatsu, Y. [13], rspctivly. Figur shows th mixing procdur of mortar in slf-compacting concrt. Firstly, trial mixs of slfcompacting concrt wr prformd. From th proprtis of fin and coars aggrgats, th amount of coars aggrgat was slctd to b 53% of solid volum and th amount of fin aggrgat was chosn as 45% of mortar volum. Fin aggrgat consistd of rivr sand and crushd sand and th ratio was slctd as 50% by volum. At th fixd aggrgats contnt, th suprplasticizr dosag and watr to powdr ratio by volum ar to b varid in ordr to achiv propr dformability and viscosity of mortar. From th trial mixs, th appropriat watr to powdr ratio was Th mix proportion of mortar was thn dtrmind from th mix proportion of concrt by taking out th amount of coars aggrgat. This is aimd to furthr study th ffct of coars aggrgat on crp of slf-compacting concrt. Th watr to cmnt ratio was varid by varying th prcnt rplacmnt of limston powdr. Tabl Spcific gravity of matrials Matrial Spcific Gravity Ordinary Portland Cmnt 3.15 Low Hat Cmnt 3.27 Limston 2.70 Sa Sand 2.60 Crushd Sand 2.58 Typ of W/P (by W/C (by No. cmnt volum) wight) Tabl Proprtis of mortar % Rplacmnt of limstion Cmnt (kg/m 3 ) Watr (kg/m 3 ) Sand (kg/m 3 ) SP (% by wight of powdr) 1-day f'c (kgf/cm 2 ) 3-day f'c (kgf/cm 2 ) 1 LH OPC OPC OPC **(OPC = Ordinary Portland Cmnt and LC = Low Hat Cmnt) *Two typs of sands wr usd: sa sand and crushd sand, with ratio 50:50 by volum Powdr + Sand Watr (1) Watr (2) + Suprplasticizr nd mixing 30 sconds mixing 120 sconds mixing 120 sconds Figur Mixing procdur of mortar in slf-compacting concrt

12 Th spcimns wr cast in control room at tmpratur of 20 C and wr dmoldd 16 hours latr aftr th stting tim. Spcimns wr kpt sald until th day of loading or drying, i.. 24 and 72 hrs aftr casting in this rsarch. Thr 10x20cm cylindrical spcimns wr tstd at th loading ag to obtain comprssiv strngth. Crp spcimns wr loadd at strss/strngth ratio of 20%, 30%, 40% and 60%. 3.2 Gomtry of spcimns This rsarch is mainly concrnd with young ag concrt whr th ffct of shrinkag and crp is significant. Thrfor, two typs of spcimns wr analyzd. Th first group is subjctd to drying only to study th factors affcting th shrinkag bhavior and th othr is subjctd to simultanous drying and loading to study th drying crp bhavior. Figur shows th spcimn usd for crp and drying shrinkag tst. Th tst spcimn was chosn as prism-shapd spcimn of siz 10x10x40cm. Th crp spcimn will b subjctd to loading by applying pr-strss mthod. In ordr to do so, stl sht was insrtd at th cntr of th spcimn bfor casting for both crp and drying shrinkag spcimn so that thy ar subjctd to th sam condition xcpt that crp spcimn will b subjctd to loading whil drying shrinkag spcimn will not. Figur shows gaug point and th position of th gaug points on th spcimn. Th gaug points ar put at th cntrlin of all four surfacs at 10 cm qual intrval. Gaug point typ was slctd instad of strain gaug bcaus at arly ag strain gaugs ar not attachd wll to th spcimn and as a rsult th valus of strain obtaind ar not rliabl. 10 cm 40 cm 10 cm Cross sction Stl sht Figur Gomtry of spcimns for crp and drying shrinkag tst Plan 5 cm 10 cm 10 cm 10 cm 5 cm 5 cm 5 cm Point gaugs φ2 mm 3 mm 10 mm 10 mm Figur Point gaugs and thir positions on th tst spcimn

13 3.3 Stup mthod Figur shows th stup mthod of th crp tst. Th tnsion stl attachd with two strain gaugs was insrtd into th crp spcimn through a providd stl sht. Ths strain gaugs wr usd to monitor if th applid strss was constant or not. Th load cannot b usd to assurd constant strss bcaus for a whil spcimn undrgo crp and incras in strain. Load applid should b also incrasd to kp applying constant strss but w cannot dtrmin th magnitud. Two stl plats and nuts wr placd on both sids of th spcimn and th jack and load cll placd on on sid of th spcimn. Plan 10 cm 40 cm Jack 10 cm Cross Sction Stl Plat Load Cll Hand Pump Data Loggr Figur Stup mthod for crp tst Load was applid to th spcimn by using a hand pump. Th valu of applid load and strain of stl wr transfrrd from data loggr to computr. Load should b applid vry rapid bcaus if th load is applid slowly som crp taks plac. As a rsult of rapid loading, th lastic strain can b dtrmind from masurmnt of th chang in strain undr a fluctuating strss of small magnitud. [14] Th crp and drying shrinkag spcimns wr tstd at control tmpratur of 20 C and 50% rlativ humidity. 3.4 Masuring mthod for strain In this rsarch, th shrinkag and crp strains wr rcordd for 7 days from th starting of th tst. From th fact that, th chang of shrinkag and crp strains is significant at arly day of tst, strains wr masurd vry 6 hours for th first 3 days and vry 12 hours for th latr 4 days. To dtrmin th shrinkag strain, th lngth chang was masurd using a contact gaug. Figur 4 shows th stags of crp tst. Th applid strss in this rsarch was slctd as 30% of its comprssiv strngth at th tsting day. P.C

14 Strss b load rload c E a d Total strain unload Strain Figur Stags of crp tst Th initial lngth was masurd (point a). Th spcimn was first loadd from zro strss to a crtain comprssiv strss lvl (a-b) and th applid strss was maintaind. Nxt tim of strain rcord (point c in Figur 3.4.1), th spcimn was unloadd to zro strss (c-d). Again th spcimn was rloadd (d-). Th procsss of unload and rload was prformd altrnatly and th lngth chang at ach stag was masurd (point b, c, d,,...). Th strain at ach point is dtrmind as ratio of lngth changs ovr initial lngth. Th strain of crp spcimn at ach laps tim is dtrmind from th diffrnc of strain at zro strss stag. Sinc th applid strss is only 30% of th strngth, th modulus of lasticity is simply calculatd as th diffrnc of strss dividd by diffrnc of strain on th rloading path.

15 Chaptr 4 ANALYSIS AND VERIFICATIONS 4.1 Analytical mthods From th tst, w can calculat crp strain by subtracting shrinkag strain and lastic strain from th total strain of crp spcimn masurd at zro strss as shown in Eqn. (4.1.1). ε = ε ε c t sh ε (4.1.1) whr ε c is crp strain, ε t is total strain, ε sh is shrinkag strain, and ε is lastic strain, rspctivly. By plotting shrinkag strain and crp strain against log (t+1), whr t is th tim whn drying and loading start, a linar rlationship can b obtaind as illustratd in Figur and 4.1.2, rspctivly. $ %&'"!" #" Figur Shrinkag strain vrsus tim (log scal) * %&'" ()!" #" Figur Crp strain vrsus tim (log scal) Morovr, from this kind of tst th modulus of lasticity and lastic strain as a function of tim can b obtaind. Figur and shows th modulus of lasticity and lastic strain plottd against log (t+1), whr t is th tim whn loading starts. + $( " ()!" #" Figur Modulus of lasticity vrsus tim (log scal) %&'" ()!" #" Figur Elastic strain vrsus tim (log scal) To compar crp, it is common to xprss as spcific crp or crp cofficint. Spcific crp is dfind by crp strain pr applid strss Eqn. (4.1.2) and crp cofficint is dfind as crp strain pr initial lastic strain Eqn. (4.1.3).

16 ε J = c (4.1.2) σ whr J is spcific crp (kgf/cm 2 ) -1, ε c is crp strain and σ is applid strss (kgf/cm 2 ), rspctivly. ε c Φ c = (4.1.3) ε i whr Φ c is crp cofficint, ε c is crp strain and ε i is initial lastic strain, rspctivly. Figur 4.1.5, and show th xprssion of spcific crp, crp cofficint, and crp factor of th tst rsult against log (t+1), whr t is th tim whn loading starts. ** %&'($( " ()!" #" Figur Spcific crp vrsus tim (log scal) * ()!" #" Figur Crp Cofficint vrsus tim (log scal) Howvr, thos xprssions ar not quit corrct sinc concrt undrgos strngth dvlopmnt simultanously. Thrfor, it had bttr xprss crp as crp strain pr lastic strain as a function of tim. This paramtr can only obtain from this nwly introducing simpl tst. Figur shows th graph of crp strain and modulus of lasticity as a function of tim plottd against log (t+1), whr t is th tim whn loading starts. Crp strain ε c Modulus of lasticity t t t+ t log t+1 Figur 4.1.7Crp strain and modulus of lasticity vrsus tim (log scal) Thus, a nw crp factor as a function of tim can b xprssd as Eqn. (4.1.4) ( ) ε c t + t ε c ( t) φ (4.1.4) c ( t) = ε ( t + t) + ε ( t) 2 whr ε c (t+ t) - ε c (t) is diffrnc of crp strain and [ε (t+ t) + ε (t)]/2 is th avrag lastic strain which can b calculatd from modulus of lasticity at tim (t+ t) and t, rspctivly.

17 * ()!" #" Figur Crp factor vrsus tim (log scal) Figur dmonstrats th crp factor as th summation of diffrnc of crp strain pr avrag lastic strain from tst rsult is plottd against log (t+1), whr t is th tim aftr start loading. 4.2 Comprssiv strngth and Young s modulus Figur and show th variation of comprssiv strngth and Young s modulus of mortar mad with diffrnt limston powdr rplacmnt. Th rplacmnt of Ordinary Portland cmnt by limston powdr rducs th strngth both at 1-day and 3-day ag. *. $( ", -* /0 $( " -* Figur Comprssiv strngth Figur Young s modulus It is clar that Young s modulus is dirctly proportional to th comprssiv strngth as shown in Figur /0 $( " ) %"', *. $( " Figur Rlationship btwn comprssiv strngth and Young s modulus

18 From th tst rsults, th rlationship btwn comprssiv strngth and Young s modulus can b xprssd as Eqn. (4.2.1). ' E (64165ln f ) (kgf/cm 2 ) (4.2.1) 4.3 Effct of typ of cmnt = c Tabl Mix proportion and nvironmntal condition for th analysis No. w/c Cmnt typ Ambint conditions cas 1 30 LC RH = 50% aftr 1 day cas 2 30 OPC RH = 50% aftr 1 day (*LC = Low Hat Cmnt, OPC = Ordinary Portland Cmnt) In this obsrvation, only typ of cmnt is diffrnt whil th strss/strngth ratio is 30% in both cass. From th tst rsults, as shown in Figur (a), (b) and (c), mortar mad with low hat cmnt xhibits highr crp than mortar mad with ordinary Portland cmnt. Th diffrncs rsult from thir diffrncs in chmical composition of cmnt. ** %'($( " 12!" #" * 12!" #" (a) Spcific crp (b) Crp cofficint * 12!" #" (c) Crp factor Figur Effct of typ of cmnt 4.4 Effct of w/c ratio Tabl Mix proportion and nvironmntal condition for th analysis No. w/c Cmnt typ Ambint conditions cas 2 30 OPC RH = 50% aftr 1 day cas 3 50 OPC RH = 50% aftr 1 day cas 4 70 OPC RH = 50% aftr 1 day (*OPC = Ordinary Portland Cmnt)

19 In this cas, th w/c ratio is varid by varying prcnt rplacmnt of Ordinary Portland Cmnt by limston powdr. From th tst rsults, it is clar that as w/c ratio incrass, crp also incrass. This du to th fact that, as w/c ratio incrass, th strngth of mortar is rducd thus rsults in highr crp. Figur (a), (b) and (c) show graph plottd btwn crp strain, spcific crp, crp cofficint, and crp factor at 7 days of diffrnt w/c ratio. crp strain at 7 days (x10^-6) y = x y = x x w/c ratio spcific crp at 7 days (x10^- 6/kgf/cm 2 ) crp strain at 7 days (x10^-6) y = 0.173x y = x x w/c ratio crp cofficint (a) Spcific crp crp strain at 7 days (x10^-6) y = x y = x x w/c ratio (b) Crp cofficint crp factor (c) Crp factor Figur Effct of w/c ratio 4.5 Effct of ag at loading Tabl Mix proportion and nvironmntal condition for th analysis No. w/c Cmnt typ Ambint conditions cas 1 30 LC RH = 50% aftr 1 day cas LC RH = 50% aftr 3 day cas 4 70 OPC RH = 50% aftr 1 day cas OPC RH = 50% aftr 3 day (*LC = Low Hat Cmnt, OPC = Ordinary Portland Cmnt) In this analysis, th tstd spcimns ar studid undr sald conditions and th strss/strngth ratio is kpt constant so that just th ffct of ag dvlopmnt can b assssd. Figur (a), (b) and (c) show th analytical rsults for this cas. It can b obsrvd that th smallr crp, th largr th valu of th ag at loading is. This can b xplaind as mortar loadd at diffrnt ags undrgos diffrnt growth in strngth with crp bing smallr th gratr th valu of strngth, which is th cas in oldr ag [15].

20 ** %'($( " ' '!" #" (a) Spcific crp * 4.6 Effct of strss/strngth ratio * ' '!" #" (b) Crp cofficint ' '!" #" (c) Crp factor Figur Effct of ag at loading Tabl Mix proportion and nvironmntal condition for th analysis No. s/s ratio Cmnt typ Ambint conditions cas LC RH = 50% aftr 1 day cas 1 30 LC RH = 50% aftr 1 day cas LC RH = 50% aftr 1 day cas LC RH = 50% aftr 1 day (*LC = Low Hat Cmnt) In this cas, th strss/strngth ratio is varid from 20%, 30%, 40% and 60%. It is vidnt that crp is significantly affctd by strss/strngth ratio. Th highr strss/strngth ratio, th largr crp. Figur (a), (b) and (c) rprsnt th ffct of strss/strngth ratio on crp. **, %'($( " )%!, ( (a) Spcific crp *, ),%!33, ( (b) Crp cofficint

21 *, )%!3, ( (c) Crp factor Figur Effct of strss/strngth ratio From th xprimntal rsults, crp dpnds on typ of cmnt, w/c ratio, ag at loading, and strss/strngth ratio, or th othr word, th strngth at th tim of th application of load and th applid load. Du to lack of data, it cannot b dfinitly conclud that crp of slfcompacting concrt which contains high volum of cmnt xhibits high crp. Du to th fact that slf-compacting concrt gains high strngth vn at arly ag, crp can b lss. Th ffct of cmnt contnt is found to b mor pronouncd on shrinkag. Howvr, shrinkag and crp ar not indpndnt phnomna. In fact, ffct of shrinkag is to incras th magnitud of crp. In addition, it was found that high rplacmnt of cmnt by limston powdr rsults in lowr comprssiv strngth, thus crp is largr. It is suggstd that limston powdr can act as fillr in concrt. Fillr is dfind as a vry finly-ground matrial, of about th sam finnss as Portland cmnt, which, owing to its physical proprtis, has a bnficial ffct on som proprtis of concrt such as workability, dnsity, prmability, capillarity, and blding or cracking tndncy. Non-ractiv limston fillr is not considrd as an intgral part of cmnt but rathr as a rplacmnt for a crtain proportion of aggrgat. Th fillr ffct is xpctd primarily through th rduction of th past porosity. It is of intrst to study th fillr ffct of small rplacmnt of limston powdr, about 5, 10 and 15%, in slf-compacting concrt. It may b possibl that th strngth of slf-compacting concrt mad with small rplacmnt of limston powdr is not much diffrnt from strngth of slf-compacting concrt mad with no rplacmnt, whil th rduction of th past porosity can b nhancd and thus crp is rducd. Morovr, som difficultis wr ncountrd and rsult in rrors of data. This is vry important bcaus it is an intractiv tst whr on factor affcts th othr. For xampl, for th cas of start drying at 24 hours aftr casting, it is found that th highr th cmnt contnt th gratr th shrinkag strain. Howvr, whn drying starts at 72 hours, ordinary Portland cmnt givs th lowst shrinkag strain. Thr ar two possibl rasons to xplain this rsult. Th first rason is that shrinkag itslf is small. Scond, it is possibl that thr occurs surfac cracking du to th grat diffrnc btwn por watr prssur of th innr cor of spcimn and th outr surfac, which is xposd to drying at 20 C and rlativ humidity of 50%. For th corrsponding crp spcimn, crack may not b obsrvd du to th applying strss. As mntion arlir, if shrinkag strain is wrong, crp strain would b also wrong du to th adoption of suprposition mthod. Morovr, it is vry hard to apply load vry fast and at th sam tim gt th rquird strss. This also rsults in som rrors of th valu of th modulus of lasticity as a function of tim and lastic strain. Errors du to masuring contact gaug ar also found to b significant. It is also important to kp constant strss all th tim. This kind of tst rquirs skill work and good control.

22 Chaptr 5 CONCLUSIONS Basd on th tst rsults of mortar of slf-compacting concrt, it was found that: 1. Crp dpnds on typ of cmnt, w/c ratio, ag at loading, and strss/strngth ratio, or th othr word, th strngth at th tim of th application of load and th applid load. 2. Rplacmnt of cmnt by limston powdr about % rsults in dcras in strngth, and thus incrass crp at arly ag. 3. Th nw tsting mthod proposd is bnficial in dtrmining modulus of lasticity as a function of tim. Howvr, good rsults ar difficult to obtain bcaus it is an intractiv tst and rquirs skill. 4. Th nw crp factor proposd is found to giv good agrmnt with th convntional trms, which ar spcific crp and crp cofficint.

23 Chaptr 6 RECOMMENDATIONS FOR FURTHER STUDY 1. Improvmnt on th tsting mthod in ordr to rduc rrors and obtain good rsults. 2. To study crp bhavior of slf-compacting concrt with small rplacmnt of limston powdr. 3. To study crp bhavior of slf-compacting concrt blndd with pozzolanic matrials, for xampl, fly ash, slag, and silica fum. 4. To study th ffct of rlativ humidity, tmpratur, suprplasticizr on crp of slf-compacting concrt at arly ag by prforming th nw tsting mthod. 5. To study th diffrncs in bhavior of crp of mortar and concrt of slfcompacting concrt in ordr to simulat a modl which can prdict crp of concrt from mortar tst. 6. To study th diffrncs in bhavior of crp of normal concrt, high strngth concrt, and slf-compacting concrt by prforming th nw tsting mthod. 7. To study tnsil crp of slf-compacting concrt.

24 REFERENCES 1. Nvill, A. M., Crp of Concrt: Plain, Rinforcd, and Prstrssd, North-Holland Publishing Company, Amstrdam, 1970, pp. 11, L Hrmit, R., What do w know about th plastic dformation and crp of concrt?, RILEM Bulltin No. 1, March 1959, pp Ali, I. And Kslr, C.E., Rhology of concrt : a rviw of rsarch, Enginring Exprimnt Station, Univrsity of Illinois, Urbana, Bulltin 476, 1965, pp Myrs, B. L. and Pauw, A., Apparatus and instrumntation for crp and shrinkag studis, Highway Rsarch Rcord No. 34, 1963, pp Bst, C. H., Pirtz, D. and Polivka, M., A loading systm for crp studis of concrt, ASTM Bulltin No. 224, Sptmbr 1957, pp Nvill, A. M., Crp of Concrt: Plain, Rinforcd, and Prstrssd, North-Holland Publishing Company, Amstrdam, 1970, pp Nvill, A. M., Rol of cmnt in th crp of mortar, ACI Journal, Proc. 55, 1959, pp Iriya, K., Hattori, T., and Umhara, H., Study on charactrization of comprssiv and tnsil crp bhavior for arly agd concrt, Journal of Matrials, Concrt Structurs and Pavmnts, JSCE, No. 599/V-40, August 1998, pp Washa, G.W. and Fluck, P.G., Effct of sustaind loading on comprssiv strngth and modulus of lasticity of concrt, ACI Journal, Proc. 46, 1959, pp Lorman, W.R., Th thory of concrt crp, ASTM Proc. 40, 1940, pp Iriya, K., Hiramoto, M., Hattori, T., and Umhara, H., Study on comprssiv crp in concrt at arly ag, Journal of Matrials, Concrt Structurs and Pavmnts, JSCE, No. 599/V-40, August 1998, pp Ouchi, M., Hibino, M., Ozawa, K. and Okamura, H., A Rational Mix-Dsign for Mortar in Slf-Compacting Concrt, Procding of th Sixth East-Asia-Pacific Confrnc on Structural Enginring & Construction, Taipi, Taiwan, 1998, pp Ouchi, M. and Edamatsu, Y., A Simpl Evaluation Mthod for Intraction btwn Coars Aggrgat and Mortar Particls in Slf-Compacting Concrt, th Procdings of th RILEM Symposium on Slf-Compacting Concrt, Stockholm, Swdn, Nvill, A. M., Crp of Concrt: Plain, Rinforcd, and Prstrssd, North-Holland Publishing Company, Amstrdam, 1970, pp Nvill, A. M., Crp of Concrt: Plain, Rinforcd, and Prstrssd, North-Holland Publishing Company, Amstrdam, 1970.

25 Appndix A Total strain, shrinkag strain, and lastic strain of all spcimns

26 !!"##!"$ % $ %!"$ $

27 % % %& &

28 Appndix B Crp strain of all spcimns

29 !!"##!"$ % $ %!"$ $

30 % % %& &

31 Appndix C Young s modulus of all spcimns

32 !!"##!"$ % $ %!"$ $

33 % % %& &

34 Appndix D Spcific crp of all spcimns

35 !!"##!"$ % $ %!"$ $

36 % % %& &

37 Appndix E Crp cofficint of all spcimns

38 !!"##!"$ % $ %!"$ $

39 % % %& &

40 Appndix F Crp factor of all spcimns

41 !!"##!"$ % $ %!"$ $

42 % % %& &