7'hc iiiaiii fimtion of tar used for t h silrfncing of roiids, whctlicr for siirfiicc drcssiiig or for tlic iiiniiiifncturc of cnrpcts, is that of nil ncllicsivc. In nll foriiis of rond surfacing tlic w i g h t of tlic trnffic is cnrricd by thc miiicriil nggrcgntc \vliich is boiidctl togctlicr niid iiindc ndlicrciit to tlic iinilcrlyiiig roiitl siirfnce by tlic tiir. In gciicrnl, ndlicsivcs nrc fluids whicli wct tlic siirfnccs to mliicli t h y arc npplicd niid thcn linrtlcii t o n tctiticioiis iiintcrinl citlicr I)y cooling, chcmiciil cliii~igc, loss of volntilc iiigrcdiciits, or by i i coiiibiiintioii of tlicsc factors. 13ituminoiis binders, with tlic csccptioii of ciiiiilsioiis nnd certiiiii ciit-biick prodiich, arc used Iicntcd nbovc iittiiosplicric tciiipcriitiire i i i d t h y Iitirdcii partially or collipletcly by cooling. 111 tlic ciise of ttlr,'furtllcr liiirtlciiiiig occiirs by tlic cviiportitioii of voliitilc oils.It is iiot proposcetl to dctil \vith tlic nspccts of iidlicsioii ilssociiitcd with tlic \vetting of stonc sllrfitccs. l'iipcrs oii this siibjcct liitvc nlrcndy bccii given to tlic Group Ly A. C. JIuglicsl iiiitl A. R. TJcc.2 If wcttiiig is tidcqiiiitc tlic I)iiidiiig prop~rt~ics of tlic tiir, which ciiii bc coiisitlcrcd to l)c tlic rcsistiiiicc of tlic biiitlcr t o iiiovciticiit of tlic :iggrcg:itc, will be 1)roportionnl to tlic viscosity. I t is tlic pi1rposc of this 1)iil)Cr to cliicitltitc ns fiir iis possiblc tlic significiincc of tlic viscosity of tlic tiir.Ttir is iisctl iii it nuiiibcr of iiictliotls of road coiistriictioii tiiitl sorfi~cing, tilid for ciicli of tlicsc pro-ct~sscs n diflcrciit grndc of t n r is cniploycd. 111 iitldition, variittioiis iirc niiidc in tlic tiir for niiy oiic ~~roccss iiccordiiig t o tlic conditions of use. Tlic tlitlhrciit grtitlcs of tar litivc I)ccii iirri\wl a t tis tlic result of thc coiiibiiicd cspcrieiicc of tlic iii:iniiftictiircrs niid iiscrs. !l'lic cssciitiiil tlilYerciicc bct;\vccn tlic! viirioiis grndcs is iii tlic viscosity, wliicli is n t prcsctit, tlr~liiictl iis tlic timc of flow of iL fiscd qiiiiiitity through t l i~ sttiiitlnrtl orilicc of tlic l3,lX.!l'.A. viscoiiicter 111, ii clcfiiiit-c t.etiipcriit,iirt~ wrying with t,lic griitlc. Otlicr 1)ropcrtics si~cli iis tlic boiliiig riiiigt! of the oils, ciirl)oil cotitelit ctc., IIISO wry, l~i b iiiiiiiily iis the result of tlic viiriiitioiis iii tlic viscosity. 'L'lic foiir cliicf iiictliotls of r o d trciitiiieiit irsiiig tiir togcthcr witli tlic viscosity riiiigcs of tlic tiirs usctl i i t u g i m i bclo\v.( I ) SwJirce ~Zre~s~~~ti~~.-'l'lic tiir is iipplicd to tlic roiitl Jurfiicc i i i 11 t l i i i i film wliicli is tlicii co\wctl with II Iiiycr of I)rokaii stoiic. IL'lit! viscosity ol' tlic tiir niiiy w r y froiii 10 see. (inciisiircti i i t 30' C.) iii the winter LO 100 scc. or tiiorc i i i tlic siiiiiiiicr.(3) 7irr ~titrcrrtler~~i-cold proccss.-CIriiilctl stonc, is coiitcrl wlicn hot with ti lilni of tm. 'l'hc iiiiiciitliiiii is gciicrnlly stored for n tiiiic nyd is npplicd t o tlic r...

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