Moisture Sensitivity Evaluation of Binder-Aggregate Mixtures

Transcription

1 TRANSPORTATION RESEARCH RECORD Moistur Snsitivity Evaluation of Bindr-Aggrgat Mixturs SHAKIR SHATNAWI, MAHESH NAGARAJAIAH AND JOHN HARVEY This study assssd th moistur snsitivity of svral bindr-aggrgat mixturs. This assssmnt inludd an valuation of th fft of hydratd lim on th moistur snsitivity of asphalt-onrt mixturs, th fft of variations from th optimum bindr ontnt on th moistur snsitivity of asphalt-onrt mixturs, th moistur snsitivity of asphalt-rubbr mixturs, and th potntial us of ontrolld-strain fatigu bam tsting to valuat th moistur snsitivity of asphaltonrt mixturs. Four aggrgats, thr asphalt ontnts, and two hydratd lim ontnts wr usd for th asphalt-onrt mixturs. Th asphalt-rubbr mixturs inludd asphalt-rubbr gap-gradd and dnsgradd hot mix. Tsts prformd inludd AASHTO T283 and th ontrolld-strain fatigu bam tst (Stratgi Highway Rsarh Program A-3A). It was found that hydratd lim in a slurry form ould b fftiv in rduing moistur snsitivity of asphalt-onrt mixturs. Th dgr of its fftivnss was found to dpnd on asphalt ontnt, lim ontnt, and aggrgat sour. Also, it was found that a rdution in th bindr ontnt by.5 prnt from th optimum ould advrsly afft th rsistan to moistur damag. AASHTO T283 rsults showd that th asphalt-rubbr mixturs may b mor snsitiv to moistur than onvntional dns-gradd asphalt-onrt mixturs. Th fatigu bam tst rsults indiatd that th tst had a potntial us in moistur-snsitivity valuation. Th potntial paramtrs wr th flxural stiffnss ratio and th fatigu lif ratio. Moistur sns1t1v1ty is on of th major problms in asphaltonrt pavmnts, potntially lading to prmatur pavmnt distrss. Rntly, moistur snsitivity (stripping) was idntifid to b th major aus of distrss in a numbr of pavmnts in northrn California. Th distrss manifstd in th form of raking (alligator, longitudinal, and transvrs) with varying dgrs of svrity (J). Rutting, ravling, blding, and pothols also ourrd at various loations. As a rsult of an invstigation ondutd by th California Dpartmnt of Transportation (Caltrans), it was rommndd that moistur snsitivity of asphalt onrt mixturs b valuatd using AASHTO T283 and that moistur-snsitiv aggrgats b tratd with hydratd lim in a slurry form bfor mixing with asphalt to inras th moistur rsistan of asphalt-onrt mixturs (2). This study valuatd (a) th fftivnss of hydratd lim in a slurry form in minimizing th moistur snsitivity of asphaltonrt mixturs, (b) th us of AASHTO T283 in assssing th moistur snsitivity of asphalt-onrt mixturs, () th fft of variations from th optimum bindr ontnt (OBC) on th moistur snsitivity of asphalt-onrt mixturs, (d) th moistur snsitivity of asphalt-rubbr mixturs, and () th potntial us of th ontrolld-strain fatigu bam tst, Stratgi Highway Rsarh S. Shatnawi, California Dpartmnt of Transportation, 59 Folsom Boulvard, Saramnto, Calif M. Nagarajaiah, 6 J Strt, Saramnto, Calif J. Harvy, Rihmond Fild Station, Bldg. 48, 131 South 46th Strt, Rihmond, Calif Program (SHRP) A-3A, in valuating th moistur snsitivity of asphalt-onrt mixturs. EXPERIMENTAL PROGRAM Th xprimntal program onsistd of th following tsts and variabls. AASHTOT Four aggrgat sours: two non-moistur-snsitiv and two moistur-snsitiv aggrgats basd on fild prforman; 2. Thr asphalt ontnts: th OBC as dtrmind by Caltrans Tst (CT) 367, and::!:::.5 prnt variations from it (OBC -.5 and OBC +.5); 3. Two hydratd lim ontnts: 1.5 and 2. prnt masurd by dry wight of aggrgat addd in a slurry form (on part lim, thr parts watr); 4. Variabl air-void lvls, on at 95 prnt rlativ ompation; and 5. Two asphalt-rubbr mixturs idntifid as asphalt-rubbr dns-gradd hot mix (ARHM-DG) and asphalt-rubbr gap-gradd hot mix (ARHM-GG). Controlld-Strain Fatigu Bam Tst 1. Two aggrgat sours (on non-moistur-snsitiv and on moistur-snsitiv aggrgat), and 2. Two asphalt ontnts (OBC and OBC -.5) Th moistur-snsitiv aggrgat was lim tratd with 1.5 prnt lim ontnt at OBC. Th spimns wr ompatd to 95 prnt rlativ ompation. MATERIALS Th four aggrgat sours usd in this study ar idntifid as Kiddr Crk, Clar Crk, Edsll, and Banhart. On th basis of thir fild prforman, th Kiddr Crk and Clar Crk aggrgats ar onsidrd non-moistur-snsitiv and th Edsll and Banhart aggrgats ar onsidrd moistur-snsitiv. A ptrographi xamination of th aggrgats rvald th following: 1. Kiddr Crk is omposd of 75 prnt mtamorphi and 25 prnt plutoni roks;

2 72 TRANSPORTATION RESEARCH RECORD Clar Crk is omposd of 2 prnt volani, 65 prnt mta volani, and I prnt plutoni roks; and 3. Edsl! and Banhart ar mainly omposd of andsit volani rok. Th gradations usd for th dns-gradd and th gap-gradd mixs ar shown in Tabl I. Th asphalt usd in this study was AR- 4. Th asphalt-rubbr bindr ontaind 17. prnt tir rubbr and 2. prnt natural rubbr (by total wight of bindr). SPECIMEN FABRICATION Th I 2-mm-diamtr AASHTO T283 spimns wr ompatd to a hight of 64 mm using th California knading ompator. Th air-void lvls sltd for th moistur-damag spimns orrspondd to 95 prnt rlativ ompation (in-pla dnsity rlativ to th laboratory dnsity) whih is th minimum in-pla ompation lvl onsidrd satisfatory by Caltrans. Othr tsts wr prformd at diffrnt air-void lvls. Th air-void lvls for th TABLE 1 Mix Proprtis Dsription Bulk Coars Spifi Gravity Apparnt Fin Spifi Gravity Combind Spifi Gravity Ri Spifi Gravity (DGAC)( Untratd) Ri Spifi Gravity (DGAC}(1.5% Lim) Ri Spifi Gravtty (DGAC)(2.% Lim) Ri Spifi Gravity (ARHM - DG)(Untratd) Ri Spifi Gravity (ARHM - GG)(Untratd) Prnt Watr Absorption (Untratd) Prnt Asphalt Absorption (Untratd) Prnt Asphalt Absorption (1.5% Lim) Prnt Asphalt Absorption (2.% Lim) Crushd Partils Sand Equivalny Prnt Air Voids(Untratd) Prnt Air Voids(1.5% Lim) Prnt Air Voids (2.% Lim) Prnt Air Voids (SSD)(Untratd) Prnt Air Voids (SSD)(1 5% Lim) Prnt Air Voids (SSD)(2.% Lim) Prnt Air Voids (SSD)(ARHM - DG ) Prnt Air Voids (SSD)(ARHM - GG) Optimum Bitumin Contnt (OBC)(Untratd) Optimum Bitumin Contnt (OBC)(1.5% Lim) Optimum Bitumin Contnt (OBC)(2.% Lim) Optimum Bindr Contnt (ARHM - DG) Optimum Bindr Contnt (ARHM - GG) Gradation. Aaargat Sour Tst Mthod Kiddr Banhart Clar Edsll CT CT AASHTOT AASHTOT AASHTOT29 - b AASHTOT ,. AASHTOT AASHTOT * CT AASHTOT AASHTOT AASHTOT CT25 95% 1% 97% 1% CT CT % 4.21% 5.6% 4.73% CT % % CT367-4.% - 4.8% AASHTOT % 6.24% 6.76% 7.47% AASHTOT % % AASHTOT % % -- a 2.5% 2.5% - * - 2.% 2.% - * CT % 4.7% 5.% 5.5% CT % - 5.% CT % - 5.% - 6.9% 7.6% - * - 7.4% 8.% - * Prnt Passin9 Gap Gradd Dns Gradd Siv Siz (mm) Kiddr Banhart Kiddr Ban hart Clar Ed sll Lim Bulk Spifi Gravity= 53 kg/m 3, Asphalt Grad AR-4 Absolut Visosity=396.4 Pasals, Kinmati Visosity=439 mm 2 /s, Pntration=32 dmm aaltrans prati for asphalt rubbr mix dsign. bkiddr Crk and Clar Crk aggrgats wr not tstd with lim. Edsll was not tstd with rubbr.

3 Shatnawi t al. 73 moistur-damag spimns wr omputd basd on AASHTO T269, whih uss th Ri mthod for maximum thortial spifi gravity (AASHTO T29) and th saturatd-surfa dry-bulk spifi gravity (AASHTO Tl 66). Compation of th bam spimns was prformd using th rolling whl ompator, whih was dvlopd at th Univrsity of California at Brkly (UCB) during th SHRP fforts (3). Aftr ompation, th bams wr ut to 5 mm X 63 mm X 38 mm. This portion of th study was aomplishd through a ooprativ ffort btwn Caltrans and UCB in whih staff mmbrs from Caltrans prformd th tsting at th rsarh laboratory of UCB with th partiipation and assistan of th staff from UCB. MIX DESIGN CONSIDERATIONS Convntional Dns-Gradd Asphalt-Conrt Mixs Without lim tratmnt, th OBCs for th onvntional mixs 'ontaining th 19.-mm gradations wr 4.3, 5., 5.5, and 4.7 prnt by dry wight of aggrgat for Kiddr Crk, Clar Crk, Edsll, and Banhart, rsptivly. Edsll and Banhart wr thn lim tratd with 1.5 prnt and 2. prnt lim. Aftr lim tratmnt, th OBC for Edsll drasd to 5. prnt for both th 1.5 prnt and 2. prnt lim. Th OBC for Banhart aftr lim tratmnt was th sam as bfor lim tratmnt. Th sltion of th OBCs was basd on CT 367, whih rquirs a minimum Hvm stability of 35, slight flushing, and a minimum of 4. prnt air voids. This tst mthod uss th alulatd air voids basd on th assumption of zro asphalt absorption. Th bulk spifi gravity is dtrmind aording to CT 38-C, whih uss th wight of th spimn in air and in watr. Th air voids for Kiddr Crk, Clar Crk, Edsll and Banhart at OBC wr 4.3, 5.6, 4.73, and 4.21 prnt using CT 367, and 6.3, 6.76, 7.47, and 6.24 prnt using AASHTO T269, rsptivly. Th air voids aording to CT 367 wr 2., 1.7, 2.74, and 2.3 prnt lowr than thos aording to AASHTO T269 for th Kiddr Crk, Clar Crk, Edsll, and Banhart aggrgats, rsptivly. From this omparison it is obvious that th urrnt Caltrans dsign prati rsults in high air voids (aording to AASHTO T269), an issu that is addrssd in this papr. Asphalt-Rubbr Mixs Th mix dsigns for th asphalt-rubbr mixs wr dtrmind aording to urrnt Caltrans pratis (i.., 2.5 prnt and 2. prnt air-void ritria for ARHM-DG and ARHM-GG, rsptivly, and no stability rquirmnt). Th bulk spifi gravity was dtrmind using CT 38-A. Th OBCs for th ARHM-DG and ARHM- - GG mixs wr 6.9 prnt and 7.4 prnt, rsptivly, for Kiddr Crk and 7.6 prnt and 8. prnt rsptivly, for Banhart. MOISTURE CONDITIONING AASHTOT283 Th onditioning of th spimns was ondutd aording to AASHTO T283. In th onditioning pross, th ompatd spimns wr stord at room tmpratur for a priod of 72 to 96 hr. Half of th spimns wr partially vauum-saturatd with watr to 6 to 8 prnt saturation. Th onditiond spimns wr put in a frzr at - l8 C ( F) for 16 hr, and thn soakd in a 6 C (14 F) watr bath for 24 hr. Finally, th spimns wr oold in a 25 C (77 F) watr bath for 2 hr bfor tsting. Controlld-Strain Fatigu Bam Tst Th onditioning of bam spimns was ondutd in a produr similar to that dvlopd as part of Projt SHRP A-3A (4), whih was dvlopd for th Moistur Conditioning Systm. In th onditioning pross, half of th bams wr vauum-saturatd with watr to 6 to 8 prnt. Ths onditiond bams wr thn submrgd and subjtd to thr yls of 5 hr at 6 C followd by 4 hr at 25 C and thn on 5-hr yl at - l 8 C. Th saturation of th bams was maintaind by wrapping thm with parafilm. PROPERTIES ANALYZED Th proprtis analyzd wr indirt tnsil strngth, tnsil strngth ratio (TSR), flxural stiffnss, flxural stiffnss ratio, fatigu lif, and fatigu ratio. Indirt Tnsil Strngth Th indirt tnsil strngth, rfrrd to hrinaftr as th tnsil strngth, is dfind as th maximum strss from a diamtral vrtial for that a spimn an withstand. It an b omputd using th following formula: at = 2Pl(Ilt D) whr at = tnsil strngth (kpa), P = maximum load arrid by th spimn (N), t = thiknss of spimn (mm), and D = diamtr of spimn (mm). TSR Th TSR, whih was first suggstd by Lottman (5), is usd as a paramtr to idntify moistur-snsitiv mixturs. Th TSR is dfind as th ratio of th strngth of onditiond (wt) spimns to th strngth of unonditiond (dry) spimns and an b xprssd mathmatially as whr TSR = tnsil strngth ratio, UT wt = tnsil Strngth Of onditiond Spimns, and ITTtry = tnsil strngth of unonditiond spimns. Flxural Stiffnss Th flxural stiffnss is a funtion of th rpatd flxural strss and th strain. Rnt rsarh has suggstd that for ontrolld-strain

4 74 TRANSPORTATION RESEARCH RECORD 1492 tsting, th fft of stiffnss on fatigu lif would vary ( 6). Taybali t al. found that an inras in stiffnss du to a hang in asphalt typ rsultd in a dras in fatigu lif, whras an inras in stiffnss du to low air voids rsultd in an inras in fatigu lif. For ontrolld-strss tsting, an inras in stiffnss rsultd in an inras in fatigu lif rgardlss of whthr it was ausd by lowr air voids or a hang in asphalt typ. Th flxural stiffnss ratio (FSR) was introdud as a paramtr in this study. It is dfind as th ratio of onditiond to unonditiond stiffnss valus. whr FSR = flxural stiffnss ratio, Swt = stiffnss of onditiond spimns, and Sdry = stiffnss of unonditiond spimns. Fatigu Lif Fatigu lif is dfind as th numbr of yls to rah 5 prnt of th initial flxural stiffnss of th bam spimn. Th fatigu lif ratio was introdud as a paramtr in this study: FLR = FLwJFLdry whr FLR = fatigu lif ratio, FLwt = fatigu lif of onditiond spimns, and FLtry = fatigu lif of unonditiond spimns. OBC to OBC +.5. For Edsll, Clar Crk and Banhart, th tnsil strngth gnrally inrasd with th hang in asphalt ontnt from OBC -.5 to OBC and from OBC to OBC +.5. Tabl 4 shows th t-tst rsults for all aggrgats. Th tabl shows that variations from th OBC gnrally produd signifiant diffrns in tnsil strngth valus. For xampl, for Edsll at 1.5 prnt and 2. prnt lim ontnts, thr wr signifiant diffrns btwn th onditiond strngth valus at OBC -.5 and OBC, and btwn th strngth valus at OBC -.5 and OBC +.5. Howvr, thr wr fwr signifiant diffrns btwn th valus at OBC and OBC +.5. Efft of Variations from th OBC on TSR TSRs gnrally inrasd with inras in asphalt ontnt (Tabl 2 and Figur 2). For xampl, Kiddr Crk, a non-moistursnsitiv mixtur, xhibitd a low TSR (.67) at th OBC -.5 lvl and highr TSRs at OBC and OBC +.5 (.81 and.83, rsptivly). Edsll, a moistur-snsitiv mixtur, xhibitd low TSRs at OBC -.5 and OBC (.52 and.55, rsptivly), and a highr TSR (.81) at OBC +.5. Sin th TSR is a ratio btwn onditiond and unonditiond strngth, a statistial analysis using t-tst groupings was ondutd to analyz th fft of onditioning on strngth (Tabl 4). Although th rsults showd som signifiant diffrns btwn th onditiond and th unonditiond spimns, fwr signifiant diffrns ourrd among th lim-tratd spimns. This is xplaind by th fat that th TSR valus ar high for th lim-tratd spimns whih mans that th onditiond and unonditiond strngths ar losr in valus. EVALUATION OF RESULTS Th AASHTO T283 moistur-damag tst rsults for th 95 prnt rlativ ompation data ar summarizd in Tabl 2. To valuat ths rsults, two typs of analysis wr usd: analysis of varian and t-tst groupings. Th data wr first valuatd using analysis of varian to s if thr wr ffts on tnsil strngth ausd by variations from th OBC and hangs in aggrgat sour, lim ontnt, or ondition (onditiond vrsus unonditiond strngth). - Tabl 3 shows th rsults of this analysis. Probabilitis lss than.5 wr onsidrd to hav signifiant ffts. Tnsil strngth was found to b signifiantly afftd by variations from th OBC and hangs in lim ontnt, aggrgat sour and ondition. Aftr th analysis of varian, t-tst groupings wr usd to show th lvls at whih th diffrns in strngth ourrd. Th ontrolld-strain fatigu bam tst data wr valuatd by xamining th flxural stiffnss and th strain-fatigu rlations bfor and aftr onditioning. Th FSR and FLR ar two paramtrs that an b usd in moistur-snsitivity valuation. Th valuation of th rsults is dsribd in th following stion. Efft of Variations from th OBC on Tnsil Strngth Variations from th OBC afftd th strngth valus signifiantly (Tabl 4 and Figur 1). As an xampl, for Kiddr Crk, th tnsil strngth inrasd with th hang in asphalt ontnt from OBC -.5 to OBC, and drasd as th asphalt ontnt hangd from Efft of Aggrgat Sour on Tnsil Strngth and TSR Tnsil strngth valus wr afftd by aggrgat sour (Figur l ). For xampl, for onditiond spimns without lim tratmnt, Clar Crk showd th highst strngth valus at OBC-.5 and OBC +.5, and Kiddr Crk had th highst strngth valus at OBC. Thr wr no signifiant diffrns btwn Clar Crk and Kiddr Crk at OBC -.5 (Tabl 5). Thrfor, Kiddr Crk ranks highst, followd by Clar Crk, in trms of tnsil strngth valus. Edsll had th lowst strngth valus at OBC -.5 and OBC and ranks blow Banhart. Banhart had th lowst strngth valus at OBC +.5. Thr wr no signifiant diffrns btwn Banhart and Edsll at all asphalt ontnts for th onditiond spimns (Tabl 5). Thrfor, both Banhart and Edsll ar xptd to prform poorly. Ths findings agr with th rportd fild prforman for all aggrgats. Th TSRs at OBC for th diffrnt aggrgats wr.81,.72,.55 and.54, for Kiddr Crk, Clar Crk, Edsll, and Banhart, rsptivly. This shows that Kiddr Crk will prform bst in trms of its rsistan to moistur damag, followd by Clar Crk. Edsll and Banhart will prform poorly. At OBC -.5, th TSRs ar.67,.67,.52 and.43, for Kiddr Crk, Clar Crk, Edsll, and Banhart, rsptivly. Ths ratios ar lowr than thos at OBC. This shows that rduing th asphalt ontnt rsults in inrasing th potntial for moistur damag of othrwis non-moistursnsiti v aggrgats. At OBC +.5, th TSRs wr.83,.81,.81

5 TABLE2 AASHTO T283 Moistur Damag Tst Rsults 95% Rlativ Comation Diffrnt Air Void Lvls Unonditiond Conditiond Unonditiond Conditiond Asphalt Aggrgat Air Voids TS a Air Voids TS Air Voids TS Air Voids TS Contnt Sour (%} kpa)b %) kpa) TSRC (%} kpa} %) kpa} TSR OBC-.5 Kiddr Crk OBC OBC OBC-.5 Clar Crk OBC OBC OBC-.5 Ed sll OBC OBC OBC -.5 Edsll(1.5%) ; OBC OBC OBC-.5 Edsll(2.%) OBC OBC OBC.5 Banhart OBC OBC OBC-.5 Banhart(1.5%) OBC OBC OBC-.5 Banhart(2.%) OBC OBC ats =Tnsil Strngth. b1 psi= 6.89 kpa (kilo Pasals). TSR =Tnsil Strngth Ratio.

6 76 TRANSPORTATION RESEARCH RECORD 1492 TABLE3 Rsults of Analysis of Varian for Diffrnt Aggrgats With and Without Lim Sour of Dgr of Variation Frdom Sum Sguars Man Sguars F Ratio Probabilit All Aggrgats (without Lim) A <.1 AC < <.1 A*AC <.1 A*C AC*C A*AC*C Error Edsll Aggrgat (with and without Lim) LC <.1 AC < <.1 LC*AC LC*C AC*C LC*AC*C Error Banhart Aggrgat (with and without Lim) LC AC LC*AC LC*C AC*C LC*AC*C Error A = Aggrgat Sour (Kiddr Crk, Clar Crk, Edsll and Banhart) LC =Lim ontnt (%, 1.5%, 2.%) AC = Asphalt ontnt (OBC -.5, OBC, OBC +.5) C = Condition (unonditiond and onditiond) Th lvl of signifian is indiatd by th probability of gratr F. Probabilitis lss than.5 ar nsidrd signifiant. <.1 <.1 < < and.55 for Kiddr Crk, Clar Crk, Edsll, and Banhart, rsptivly. Ths rsults show that th TSRs for Kiddr Crk and Banhart did not hang signifiantly, and TSRs inrasd for both Clar Crk and Edsll. This indiats that inrasing asphalt ontnt may rsult in inrasing rsistan to potntial damag only in som aggrgats. Efft of Hydratd Lim on Tnsil Strngth and TSR Lim tratmnt afftd th strngth valus and tnsil strngth ratio (Tabl 2, Figurs 1 and 2). Gnrally, th addition of lim inrasd th strngth and TSR. Th strngth improvmnt in onditiond spimns ausd by th addition of lim is shown in Tabl 6. Th strngth improvmnt was omputd aording to th following formula: SI= [(<rtl - <JTNd/a-rCNd X 1% whr SI = strngth improvmnt (% ),. <JTL = tnsil strngth of onditiond lim tratd spimns, and <JTNL = tnsil strngth of onditiond spimns without lim tratmnt. Th SI paramtr givs a masur of th fft of lim tratmnt on th strngth of onditiond spimns. Tabl 6 shows that thr wr strngth improvmnts du to th addition of lim at both th 1.5 prnt and 2. prnt lim ontnts. For Edsll, th improvmnts wr spially high at OBC -.5, at whih thy wr 171 prnt and 243 prnt for th 1.5 prnt and 2. prnt lim ontnts, rsptivly. At OBC th improvmnts wr 116 prnt and 142 prnt for th 1.5 prnt and 2. prnt lim ontnts, rsptivly. For Banhart, th improvmnts wr also high at OBC -.5 whr thy wr 12 prnt and 84 prnt for th 1.5 pr-

7 TABLE 4 AASHTO T283 Rsults fort-tst Groupings at 95 prnt Rlativ Compation Asphalt Spimn Kiddr Crk Clar Crk Ed sll Edsll1.5%) Edslf 2. %) Banhart Banhart( 1. 5% Banha rt2.% Contnt Condition Mana T-srb Man T-gr Man T-sr Man T-9r Man T-gr Man T-9r Man T-ar Man T-ar Comparision btwn Spimn onditions OBC-.5 Unond. 783 A 969 A 54 A 12 A 118 A 756 A 864 A 756 A Cond. 526 B 648 B 283 A 765 B 857 A 324 B 714 A 597 B OBC Unond A 944 A 834 A 136 A 1251 A 967 A 857 A 864 A Cond. 184 A 678 B 455 B 981 A 11 A 521 B 847 A 898 A OBC +.5 Unond. 926 A 118 A 891 A 1387 A 191 A 1132 A 17 A 93 A Cond. 77 A 955 B 721 A 157 B 134 B 62 B 969 B 838 A Comparision btwn diffrnt asphalt ontnts OBC-.5 Unond. 783 A 969 A 54 A 12 A 118 A 756 A 864 A 756 A OBC Unond B 944 A A 1251 A 967 B 857 A 864 B OBC +.5 Unond B 891 B 1387 B 191 A 1132 B 17 BA 93 AB OBC-.5 Cond. 526 A 648 A 283 A 765 A 857 A 324 A 714 A 597 A OBC Cond. 184 B 678 A 455 B 981 B 11 B 521 B 847 A 898 B OBC +.5 Cond B B 134 B 62 B 969 B 838 B 8 Valus ar in kilopasals (1 psi= 6.89 kpa) bgroups having diffrnt dsignations indiat signifiant diffrns. Prntag in parnthss indiats th lim ontnt.

8 78 TRANSPORTATION RESEARCH RECORD Ci 12 ll. 1.&:. 'Si 8 w 6.!! u; 4 QI t- 2 Ci 1 ll. s 8 Cl 6 w.!! 4 u; QI t- 2 ElllOBC-.5 mos aos +.5 K Crk Edsll Clar Crk Ban hart Aggrgat Sour (a) Unonditiond Spimns (without Lim) llobc-.5 filjobc (b) Conditiond Spimns (without Lim) Ci 12 ll. 1.&:. 'Si 8 w 6.!! u; 4 QI... 2 llobc-.5 mos E!IOBC +.5 g = = w g t:'ll 1:. CI>. ns. v N Cl> t: Cl>.s:.s: - =ijj f;i f;i m.,.: m<'i Aggrgat Sour () Unonditiond Spimns (with Lim) Ci ll. 1.&:. 8 'Si Ci) 6.!! 4 u; 2 llobc -.5 l!llobc EIOBC +.5 = = w N Cl> = E $= "Cl w Aggrgat Sour (d) Conditiond Spimns (with Lim) FIGURE 1 Tnsil strngth as a funtion of aggrgat sour and bindr ontnt. nt and 2. prnt lim ontnts, rsptivly. At OBC th improvmnts wr 63 prnt and 72 prnt for lim ontnts of 1.5 prnt and 2. prnt, rsptivly. At OBC +.5 thr wr improvmnts for both Banhart and Edsll but thy wr not as grat as thy wr at th othr asphalt ontnts. This shows that lim is most fftiv in inrasing strngth, spially at th lowr asphalt ontnts whr th potntial for moistur snsitivity is highr. Tabl 5 shows th rsults of th t-tst omparing strngth valus at diffrnt lim ontnts. Th tabl ompars th strngth valus for Edsll and Banhart bfor and aftr lim tratmnt. Ths rsults show that thr ar signifiant diffrns btwn th strngths bfor and aftr lim tratmnt for both lvls of lim ontnt. Howvr, thr ar no signifiant diffrns btwn strngth valus at 1.5 prnt lim ontnt and 2. prnt lim ontnt, vn though th Sis for th 2. prnt lim ontnt wr gnrally highr than thos for th 1.5 prnt lim ontnt. Edsll xhibitd lowr strngth valus than Banhart at OBC -.5 and OBC, but highr strngth at OBC +.5 for th onditiond spimns. Aftr lim tratmnt, Edsll xhibitd highr strngth valus at all asphalt ontnts. Tabl 6 shows th fft of lim tratmnt on th TSR valus in trms of tnsil strngth ratio improvmnts (TSRis), whih wr omputd aording to th following formula: TSRI = [(TSRAL - TSR 8 d!tsr 8 d X 1% whr TSRI = tnsil strngth ratio improvmnt (% ), TSRsL = tnsil strngth ratio bfor lim tratmnt, and TSRAL = tnsil strngth ratio aftr lim_ tratmnt. Both Edsll and Banhart showd improvmnts. Banhart showd highr TSRI than Edsll. Th TSRis at OBC -.5 and OBC wr 44 prnt and 73 prnt for Edsll, and 98 prnt and 83 prnt for Banhart at 1.5 prnt lim ontnt, rsptivly. At ths asphalt ontnts th addition of lim ausd improvmnts in TSR. Similar pattrns, with highr TSRis, ar xhibitd for th 2. prnt lim ontnt. At OBC +.5 th improvmnts wr not onsistnt. At this asphalt ontnt, th TSRis for Edsll wr -6 prnt (no improvmnt) and 17 prnt for th 1.5 prnt and 2. prnt lim ontnts, rsptivly, and th TSRI for th Banhart wr 65 prnt and 69 prnt for th 1.5 prnt and 2. prnt lim ontnts, rsptivly. This supports th prvious onlusion that lim tratmnt was most fftiv at lowr asphalt ontnts. This analysis maks it lar that trating aggrgats with lim bfor mixing with asphalt inrass th strngth and th TSR. Also, baus th SI and TSRI paramtrs giv a masur of th fft of tratmnts suh as lim, thy should b usd along with th TSR in moistur-snsitivity valuation. Efft of Air Voids on Tnsil Strngth and TSR Th analysis prsntd abov was ondutd at 95 prnt rlativ ompation, at whih lvl ah mixtur had a uniqu OBC with a

9 Shatnawi t al 'St.4 Ci).3.!!! ;;;.2 u I t: ti)!::. 1.2 &!.8. 'St.6! Ci).4.!!! ;;.2 Kiddr Crk Edsl! Clarrk Banhart Aggrgat Sour a S imns without Lim _I I _I 11 li ;B tl Aggrgat sour () Spimns With and Without Lim.9.8 :;.7 ::.,.6 Ci).5.!!.4 {!! "* _.ilr---a t Air Voids (%) (b) Spimns Without Lim :;.8 ::.,.6 (i).4.!!.2 {!! : KC no lim OBC KC no Dm OBC - +- KC no Dm OBC ED no llm OBC ED no lim OBC - - ED no lim OBC +.5 CC no 61n OBC CC no lim OBC - - CC no Um OBC BN no llm o" BN no llm OBC - - BN no lim OBC +.5 KC = Kiddr Crk ED= Edsl! CC = Clar Crk BN = Banhart Air Voids (%) (d) Spimns With and Without Lim + ED no llm OBC Ir-ED no llm OBC - - ED no llm OBC ED 2.% lim OBC ED 2.% lim OBC..,_ED 2.% flm OBC BN no llm OBC BN no Um OBC - - BN no Um OBC BN 2.% Orn OBC BN 2.% Um OBC - - BN 2.% lim OBC +.5 FIGURE 2 TSR as a funtion of aggrgat sour, lim ontnt, bindr ontnt, and air voids. uniqu air-void lvl. Th variations from th OBCs also produd diffrnt lvls of air voids. Thrfor, th valuatd data showd a ombind fft of air voids and asphalt ontnt. Ths variations rflt what happns in prati in California. Othr tsts wr ondutd at diffrnt air-void lvls (Tabl 2). Figurs 2 and 3 show th fft of air voids on TSR and tnsil strngth. Th figurs show that air voids hav a signifiant fft on tnsil strngth. As air voids inras, tnsil strngth drass signifiantly. Thr wr som drass in th TSRs orrsponding to th inrass in air voids. Efft of Using Asphalt-Rubbr Bindr on Tnsil Strngth and TSR Tabl 7 ontains a summary of AASHTO T283 rsults for th asphalt-rubbr mixturs along with th onvntional dns-gradd asphalt-onrt (DGAC) mixturs at 95 prnt rlativ ompation. Ths mixturs wr ompard at thir OBCs. Th tabl shows that tnsil strngth valus for th ARHM-DG wr almost qual to th DGAC mixtur for Kiddr Crk, and highr than th DGAC for Banhart. Th strngth valus for ARHM-GG wr signifiantly lowr than thos. for DGAC and ARHM-DG mixturs. Th tabl also shows low TSR valus for th asphalt-rubbr mixturs vn for th non-moistur-snsitiv Kiddr Crk aggrgat. Ths rsults indiat that thr ould b moistur-damag problms assoiatd with th asphalt-rubbr mixturs. Howvr, othr typs of tsts should b ondutd to vrify ths findings. Tsts that nd to b onsidrd inlud th simpl shar and ontrolld-strain fatigu bam tst (SHRP A-3A). Ths tsts, along with fild xprin, will show th appliability of th AASHTO T283 tst in th valuation of th moistur snsitivity of asphalt-rubbr mixs. Evaluation of th Controlld-Strain Fatigu Bam Tst Tabl 8 shows th normalizd rsults of th ontrolld-strain flxural bam tst for diffrnt strain lvls. Th tabl shows that for th spimns that wr not tratd with lim,. onditioning rdud both flxural stiffnss and fatigu lif and gnrally inrasd th phas angl. On th othr hand, th lim-tratd spimns showd no signifiant rdutions in stiffnss, had rmarkabl inrass in fatigu lif and xhibitd rdutions in phas angl as a rsult of onditioning. Ths hangs indiat that whn lim was prsnt, a ration ourrd during onditioning that rsultd in strngthning th bindr-aggrgat bond. Thrfor, onditioning of th limtratd spimns rsultd in a strongr bond, instad of th wakr bond xprind with th untratd spimns. Mor rsarh is ndd to onfirm this finding. Tabl 9 shows th fft of lim on th FSR and th FLR. Th tabl shows that for Banhart, th avrag FSR inrasd from.61 to.97 and th avrag FLR inrasd from.49 to 3.6 as a rsult

10 TABLES Tnsil Strngth Data: t-tst Groupings Showing th Efft of Aggrgat Sour and Lim Contnt for Spifi Bindr Contnts Aggrgat Man(kPat T-Grouping 6 Man(kPa) T-Grouping Man(kPa) T-Grouping OBC-.5 OBC OBC+.5 Unonditiond Spimns without Lim Kiddr Crk 783 A 1341 A 926 A Ed sll 54 B 834 B 891 A Clar Crk CB 118 AB Ban hart 756 D 967 DB 1132 AB Conditiond Spimns without Lim Kiddr Crk 526 A 184 A 77 A Ed sll 283 B 455 B 721 AB Clar Crk 648 A AC Banhart 324 B 521 DB 62 ABC Edsll Spimns with and without Lim (Unonditiond) Edsll no tim 54 A 834 A 891 A Edsll 1.5% lim 12 B 136 B 1387 B Edsll 2.% lim 118 B 1251 AB 191 Edsll Spimns with and without Lim (Conditiond) Edsll no lim 283 A 455 A 721 A Edsll 1.5% tim 765 B 981 B 157 B Edsll 2.% tim 967 B 11 B 134 B Banhart Spimns with and without Lim (Unonditiond) Banhart no tim 756 A 967 A 1132 A Banhart 1.5% lim 864 B 857 A 17 A Banhart 2.% lim 756 AB 864 BA 93 A Banhart Spimns with and without Lim (Conditiond) Banhart no lim 324 A 521 A 62 A Banhart 1.5% lim 714 B 847 B 969 B Banhart 2.% lim 597 B 898 B 838 B 8 1 psi = 6.89 kpa bgroups having diffrnt dsignations indiat signifiant diffrns.

11 Slzatnawi t al. 81 TABLE 6 Tnsil Strngth and TSR Improvmnt du to th Addition of Lim for Conditiond Spimns Asphalt Contnt SI(%) TSRI(%) SI(%) TSRI(%) Edsll with 1.5% Lim Edsll with 2.% Lim OBC OBC OBC OBC-.5 OBC OBC +.5 Banhart with 1.5% Lim Banhart with 2.% lim of lim tratmnt. Th tabl also shows that th FSRs and TS Rs had similar trnds in trms of thir ranking of th various mixs. Th strongst trnds ar assoiatd with th 2-mirostrain rsults. Th FLRs wr signifiantly lowr than th FSRs and TSRs xpt for th lim-tratd spimns. Th avrag FLRs an b onsidrd shift fators for th purposs of pavmnt modling. Th masurmnt of flxural stiffnss bfor and aftr onditioning an b usd in pavmnt analysis. Th strain-fatigu lif rlations wr plottd in Figur 4 for two strain lvls (2 and 3 mirostrains). Th figur indiats that moistur onditioning drass fatigu lif (xpt for th lim tratd spimns) and that th mixturs at OBC -.5 wr mor moistur snsitiv than thos at OBC. Although th data wr limitd, th rsults indiat that th ontrolld-strain fatigu bam tst has a potntial us in moistur-snsitivity valuation of bindr-aggrgat mixturs. This tst ma- 2 + KC no lim OBC Ir--KC no lim OBC Ci - - KC no lim OBC * ED no lim OBC ED no lim OBC -s ED no lim OBC +.5 C> - CC no lim OBC a- no lim OBC Cl) - h - CC no Orn OBC +O.f.!! 1 BN no lim OBC -.5 'iii 8 --<>-BN no lim OBC u B!" n!:jlm OBC +O: t- 6 KC = Kiddr Crk )( ED= Edsll 4 CC = Clar Crk BN = Banhart Ci...s:... C>... Cl).!! 'iii {!! ' 6 ' >< Air Voids (%) (b) Conditiond Spimns (Without Lim) 14 + KC no lim OBC -.5 -lr--kc no lim OBC KC no lim OBC +.5 K ED no lim OBC ED no lim OBC ED no lim OBC +.5 <> CC no lim OBC -.5 -a- no lim OBC - h - CC no lim OBC +.5 Bl- BN no lim OBC <>-BN no lim OBC - :if - BN no lim OBC ED no lim OBC lr--ed no lim OBC Ci 14 - <> - ED no Orn OBC +.5 K ED 2.% Um OBC -.5 s 12 C> ----ED 2.% lim OBC ED 2.% lim OBC Cl) - BN no lim OBC !! -a-bn no Orn OBC 'iii 6 - -/s - BN no lim OBC +.5 u I- D BN 2.% Orn OBC <>-BN 2.% lim OBC BN 2.% lim OBC Air Voids (%) Air Voids (%) () Unonditiond Spimns (With and Without Lim) (a) Unonditiond Spimns (Without Lim) ED no lim OBC ,._ED no Um OBC "'i 14 s 12 C> 1 ii).!! 8 u; ED no lim OBC +.5 K ED 2.'lli lim OBC ED 2.'lli Um OBC ED 2.'lli Orn OBC +.f <> BN no lim OBC -.5 -B-BN no Um OBC ;,_ -/s - BN no lim OBC +.5 D BN 2.'lli lim OBC <>-BN 2.% lim OBC - :if - BN 2.% lim OBC Air Voids (%) (d) Conditiond Spimns (With and Without Lim) FIGURE 3 Tnsil strngth as a funtion of air voids for various aggrgats.

12 82 TRANSPORTATION RESEARCH RECORD 1492 TABLE7 Summary of AASHTO T283 Moistur Damag Tst Rsults for Asphalt-Rubbr Mixs Unonditiond Aggrgat Air Voids TSa Sour %) kpab Kiddr Crk DGAC Man Std. Dv ARHM DG Man Std. Dv ARHM GG Man 6, Std. Dv Ban hart DGAC Man Std. Dv ARHM DG Man Std. Dv ARHM GG Man Std. Dv TS =Tnsil Strngth. Conditiond Air Voids TS Avrag %} kpa TSRC b1 psi = 6.89 kpa (kilopasals). rsr =Tnsil Strngth Ratio. surs nginring proprtis that an b usd in pavmnt analysis. Also, this tst is an appropriat tool for moistur-snsitivity valuation sin th tnsion proprtis that rlat to th bindr-aggrgat bond ar valuatd undr yli loading. Furthr valuation and rfinmnt of this tst for moistur-snsitivity valuation ar nssary. CONCLUSIONS 1. Th modifid Lottman tst (AASHTO T283) appars to diffrntiat non-moistur-snsitiv from moistur-snsitiv asphaltonrt mixturs. 2. Hydratd lim in a slurry form an b fftiv in inrasing th moistur-damag rsistan of moistur-snsitiv asphaltonrt mixturs. 3. A rdution in th bindr ontnt from th optimum by.5 prnt may hav a dtrimntal fft on th moistur-damag rsistan of othrwis non-moistur-snsitiv mixturs, and an b dtrimntal for moistur-snsitiv mixturs. 4. Lim tratmnt may dras th moistur snsitivity of asphalt-onrt mixturs that is ausd by variations from th OBC. 5. Lim tratmnt is most fftiv in inrasing tnsil strngth blow th OBC whr th potntial for moistur snsitivity is gratr.

13 Shatnawi t al. 83 TABLES Summary of Controlld-Strain Fatigu Bam Tst Rsults at 95 Prnt Rlativ Compation Spimn Strain Aggrat Sour Condition l:,!:-strainl Kiddr Crk OBC-.5 Unonditiond 2 OBC-.5 Conditiond 2 OBC-.5 Unonditiond 3 OBC -.5 Conditiond 3 OBC Unonditiond 2 OBC Conditiond 2 OBC Unonditiond 3 OBC Conditiond 3 Nt Stiffnss Phas Cll kpat Angl 69,288 4,184, ,214 3,13, ,538 3,193, ,242 2,773, ,481 6,791, ,62 5,721, ,664 6,395, ,292 5,37, Ban hart OBC-.5 Unonditiond 2 OBC-.5 Conditiond 2 OBC-.5 Unonditiond 3 OBC-.5 Conditiond 3 OBC Unonditiond 2 OBC Conditiond 2 OBC Unonditiond 3 OBC Conditiond 3 Banhart with 1.5% Lim OBC Unonditiond 2 OBC Conditiond 2 OBC Unonditiond 3 OBC Conditiond 3 a1 psi = 6.89 kpa (kilopasals). 162,846 4,92, ,619 2,679, ,658 4,267, ,13 1,142, ,42 5,554, ,417 2,734, ,845 5;61, ,19 4,12, ,443 7,13; ,636 7,17, ,877 6,885, ,576 6,411, In moistur-snsitivity valuation, tnsil strngth, tnsil SI and TSRI ausd by additivs should b onsidrd as wll as TSR. 7. High air voids an rsult in a rdution in tnsil strngth and TSR. 8. Th ontrolld-strain fatigu bam tst has a potntial us in moistur-snsitivity valuation. Th stiffnss ratio and FLR ar potntial paramtrs. 9. Asphalt-rubbr mixturs (ARHM-GG and ARHM-DG) may b mor moistur-snsitiv than onvntional dns-gradd mix- turs ontaining th sam aggrgat. Othr tsts ar ndd to vrify this finding. ACKNOWLEDGMENTS This projt was fundd by th California Dpartmnt of Transportation in oopration with th U.S. Dpartmnt of Transportation, FHW A. Th authors wish to aknowldg th assistan of TABLE9 Moistur-Damag Paramtrs: TSR, FSR, and FLR Aggrgat Sour. Tnsil Strngth Flxural Stiffnss Fatigu Lif Ratio Ratio Ratio 2 -strain 3 -strain Avra 2 -strain 3 -strain Avrag Kiddr Crk-CBC Kiddr Crk-OBC Banhart-OBC Banhart-OBC Banhart-OBC with Lim

14 84 TRANSPORTATION RESEARCH RECORD ;-- C)... >< -.!! i u,.., l'o " i..:... Kiddr OBC -.5 Unon Kiddr OBC -.5 Con <> Kiddr OBC Unon Kiddr OBC Con Rptitions to 5% Initial Stiffnss (N,).;-- C)... >C -.!!. - u i : "",...,... """"" "" ' - - "r-- "' Rptitions to 5% Initial Stiffnss (N,) FIGURE 4 Strain-fatigu lif rlation at 2 C. Banhart OBC -.5 Unon Banhart OBC -.5 Con <> Banhart OBC Unon Banhart OBC Con "' Banhart OBC Unon/lim _.,_Banhart OBC Con/lim Jff Rush and Rgina Adams. Th valuabl support rivd from Robrt Doty is gratly appriatd. Also, spial thanks ar du Profssor Monismith, who failitatd th us of th UCB laboratory for Caltrans staff. REFERENCES 1. Shatnawi, SR., and J. Van Kirk. Prmatur Asphalt Conrt Pavmnt Distrss Causd by Moistur Indud Damag. In Transportation Rsarh Rord 1417, TRB, National Rsarh Counil, Washington, D.C., 1993, pp Shatnawi, S. R. Prmatur AC Pavmnt Distrss-Distrit 2 Invstigation. Rport FHW A-CA!fL (CALTRANS-F91 TL7). California Dpartmnt of Transportation, Saramnto, Harvy, J., and C. L. Monismith. Effts of Laboratory Asphalt Conrt Spimn Prparation Variabls on Fatigu and Prmannt Dformation Rsults Using Stratgi Highway Rsarh Program A-3A Proposd Tsting Equipmnt. In Transportation Rsarh Rord 1417; TRB, National Rsarh Counil, Washington, D.C., 1993, pp Trrl, R. L., and S. Al-Swailmi. Watr Snsitivity of Asphalt-Aggrgat Mixturs Tst Dvlopmnt. SHRP, National Rsarh Counil, Washington, D.C., Lottman, R. P. Laboratory Tst Mthod for Prditing Moistur Indud Damag to Asphalt Conrt. In Transportation Rsarh Rord 843, TRB, National Rsarh Counil, Washington, D.C., 1982, pp Taybali, A. A., J. A. Daan, J. S. Coplantz, J. T. Harvy, and C. L. Monismith. Mixturs and Mod-of-Loading Effts on Fatigu Rspons of Asphalt-Aggrgat Mixturs. Pro., AAPT Marh Publiation of this papr sponsord by Committ on Charatristis of Bituminous Paving Mixturs to Mt Strutural Rquirmnts.