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CHAPTER 7PAVEMENT J ONTS

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7-1 . J oi nt types and usages . J oi nts are requi red i n ri gi d pavementsto permt expansi on and contracti on of concrete due to temperature andmoi sture changes, to rel i eve warpi ng and curl i ng stresses whi ch resul tf romtemperature and moi sture gradi ents wthi n the sl ab, to mnimzeuncontrol l ed cracki ng caused by frost acti on, and as a constructi onexpedi ent to separate the areas of concrete pl aced at di f ferent times .There are three general types of j oi nts used i n ri gi d pavements : (a)contracti on, ( b) constructi on, and (c) expansi on . Guidance rel ati ve tothe requi rements for these j oi nts i s gi ven i n the fol l owngsubparagraphs .a . Contracti on j oi nts . Contracti on j oi nts are provided to controlcontracti on cracki ng fromtemperature changes and fromthe i ni ti alshri nkage of the concrete . The mnimumdepth of the groove forcontracti on j oi nts general l y shoul d be one-si xth of the pavementthi ckness, but not l ess than the maximumnomnal si ze of the aggregateused . However, where thi s depth has been found to be i nsuf f i ci ent t oproduce the desi red cracki ng at the groove, the depth of the grooveshoul d be i ncreased t o one-fourth of the pavement thi ckness . The si ze

of the groove shoul d conformto the dimensi ons shown on StandardMobi l i zati on Drawng No . XEC-006 .(1) For transverse contracti on j oi nts i n nonrei nforced ri gi dpavements, suf f i ci ent l oad transfer can be devel oped fromthe aggregatei nterl ock al ong the f ractured face of the j oi nt so that no otherprovi si on for l oad transfer i s requi red i n C asses D and E pavements .For rei nforced ri gi d pavements, the l onger slab l engths wll resul t i nl arger openi ngs at the transverse contracti on j oi nts and for al l suchpavements the transverse contracti on j oi nts shoul d be dowel ed . Dowel sare al so requi red for C ass B nonrei nforced pavements .(2) Longi tudi nal contracti on j oi nts are requi red al ong thecenterl i ne of nonrei nforced ri gi d pavement l anes havi ng a wdth equalto or greater than the maximumspaci ng i ndi cated i n paragraph 7-3, fortransverse contracti on j oi nts for vari ous pavement thi cknesses . Wheresuch l ongi tudi nal j oi nts are requi red, ti e bars shoul d be used toprevent cumul ati ve openi ng of the j oi nt and excessi ve separati on of the

adj acent l anes . The ti e bars shoul d be No . 5 deformed steel bars, 30i nches i n l ength . Spacing of the tie bars shoul d be 30 i nches, centerto center .(3) For rei nforced ri gi d pavements where two traf f i c l anes arepl aced as a singl e paving l ane, a l ongi tudi nal dummy groove j oi ntshoul d be provided at the centerl i ne of the paving l ane to controlcracki ng duri ng concrete placement . I n these j oi nts, the rei nforci ng

steel i s carri ed through the joint, and tie bars are not requi red .

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(4) Longi tudi nal contracti on j oi nts at the centerl i ne ofrei nforced ri gi d pavements are requi red onl y when the wdth of thepavement exceeds the al l owabl e l ength of sl ab, L, for the percentage ofsteel rei nforcement being used . Wen such j oi nts are requi red, thesteel rei nforcement shoul d be broken at the j oi nt, and ti e bars siml arto those descri bed above shoul d be used .

b . Constructi on j oi nts . Constructi on j oi nts are provi ded toseparate the areas of concrete pl aced at di f ferent ti ms, and may beei ther l ongi tudi nal or transverse, as requi red .(1) The spacing of l ongi tudi nal constructi on j oi nts wl l dependl argel y on the paving equi pment . Wth most present-day equi pment,paving l anes 24 feet or more i n wdth are possi bl e and may be used .

Determnati on of the wdth of paving l ane to be used, that i s, whethera 24-foot-wde road or street shoul d be paved i n a singl e l ane or i ntwo 12-foot-wde l anes, i s l ef t to the j udgment of the desi gner .

(2) Wen a l ongi tudi nal constructi on j oi nt i s used at the centerof two-l ane pavements, a keyed j oi nt wth t i e bars siml ar to thoserequi red for l ongi tudi nal contracti on j oi nts, or threaded spl i t5/8-i nch ti e bol t, shoul d be used . Wen a l ongi tudi nal constructi onj oi nt i s used at the center of pavements having four or more pavi ngl anes, a dowel ed j oi nt shoul d be used .

(3) Transverse constructi on j oi nts shoul d be i nstal l ed at theend of each day' s pavi ng operati on, and at other poi nts wthi n a pavingl ane where the pl aci ng of concrete i s di sconti nued a suf f i ci ent l engthof ti m for the concrete t o start to set . Al l transverse constructi onj oi nts i n nonrei nforced ri gi d pavements shoul d be of the dowel ed type,and shoul d be l ocated i n pl ace of other regul arl y spaced transversej oi nts . Wen paving i s resumed, the regul ar transverse j oi ntconstructi on shoul d be used, begi nni ng wth the first regul arl yschedul ed transverse j oi nt . Wen a transverse constructi on j oi nt i srequi red wthi n a slab i n a rei nforced ri gi d pavement, the rei nforci ngsteel shoul d be carri ed through the j oi nt and tie bars added .

c . Expansi on j oi nts . Expansi on j oi nts are provi ded for the rel i efof forces resul ti ng f romthermal expansi on of the pavement, and topermt unrestrai ned di f ferenti al hori zontal movement of adj oi ni ngpavements and/or structures . There are two types of expansi on j oi nts,dowel ed and thickened-edge, both of whi ch shoul d be provi ded wth anonextrudi ng type f i l l er metal . Usual l y a preformed f i l l er 3/4-i nchthi ck wl l be adequate . The expansi on j oi nt shoul d be so desi gned asto provi de a complete and uni formseparati on between the ri gi dpavements or between the ri gi d pavement and the structure concerned .

(1) Doweled expansi on j oi nts shoul d be used for al l transverseexpansi on j oi nts wthi n ri gi d pavements except at the i ntersecti ons ofri gi d pavements wth structures or wth other ri gi d pavements . The

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desi gner i s cauti oned that expansi on j oi nts wthi n ri gi d pavements aredi ff i cul t to construct and maintain, and often contri bute to pavementfai l ures . For these reasons, thei r use shoul d be kept t o the absol utemnimumnecessary to prevent excessi ve stresses or di storti on i n thepavement . I nternal expansi on j oi nts shoul d be omtted i n al l ri gi dpavements 8 i nches or more i n thi ckness, and al so i n pavements l essthan 8 i nches thi ck when the concrete i s pl aced duri ng warmweather .

(2) At the i ntersecti on of two ri gi d pavements i t i s necessaryto provi de for some di fferenti al hori zontal movement i n j oi nts of thi stype to prevent the expansi on of one pavement fromdi storti ng the otherpavement . I n such cases, the transverse expansi on j oi nts shoul d bedesi gned as thi ckened-edge, sl i p-type j oi nts . Siml arl y, thethi ckened-edge, sl i p-type expansion j oi nt normal l y wl l be the mostsui tabl e for use where expansi on j oi nts are i nstal l ed to surround or toseparate fromthe pavement any structure that proj ects through, i nto,or against the pavement . Typi cal exampl es i nclude the approaches tobui l di ngs or around drai nage i nl ets .(3) Shoul d i t be necessary to construct a l ongi tudi nal expansi onj oi nt wthi n a ri gi d pavement, agai n a thi ckened-edge, sl i p-typeexpansi on j oi nt shoul d be used . Expansi on j oi nts are not requi redbetween new and exi sti ng ri gi d pavements when the exi sti ng pavement i sbei ng wdened or extended wth paving l anes paral l el t o thel ongi tudi nal axi s of the exi sti ng pavement .

7-2 . J oi nt desi gn . Typi cal detai l s for the desi gn of expansi on,contracti on, and constructi on j oi nts are shown on Standard Mobi l i zati onDrawng No . XEC-006 for nonrei nforced and rei nforced ri gi d pavements .a . Doweled j oi nts . The primary functi on of dowels i n ri gi dpavements i s that of a l oad-transfer devi ce . As such, the dowelseffect a reducti on i n the cri ti cal edge stress that i s di rectl y

proporti onal to the degree of l oad transfer achi eved at the j oi nt . Asecondary functi on of the dowels i s to mai ntai n the verti cal al i nementof adj acent sl abs, thereby preventi ng faul ti ng at the j oi nt . Dowel sshoul d be requi red for the fol l owng types of j oi nts : (a) transversecontracti on j oi nts i n C ass B nonrei nforced ri gi d pavements, ( b)transverse contracti on j oi nts i n al l rei nforced ri gi d pavements, (c)transverse constructi on j oi nts i n al l nonrei nforced ri gi d pavements,(d) center l ongi tudi nal constructi on j oi nts i n ri gi d pavements four ormore l anes i n wdth, and (e) transverse expansion j oi nts i n al l ri gi dpavements . Dowel di ameter, l ength, and spaci ng shoul d be in accordancewth the cri teri a presented i n tabl e 7-1 . Were dowels l arger than1-i nch di ameter are requi red, extra-strength pi pe may be used as anal ternate for sol i d bars . Wen extra-strength steel pi pe i s used fordowels, however, the pi pe shoul d be fi l l ed wth a sti ff mxture ofei ther sand-asphal t or cement mortar, or plugged at the ends of thepi pe . I f the ends of the pi pe are plugged, the pl ug shoul d f i t i nsi dethe pi pe and be cut off f l ush wth the end of the pi pe so that there

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wl l be no protrudi ng materi al to bond wth the concrete and preventf ree movement of the pavement . Normal l y, dowel s shoul d be l ocated atthe mddepth of the pavement sl ab . However, a tol erance of one-hal f ofthe dowel di ameter, above or bel ow the mddepth of the sl ab, may beal l owed i n l ocati ng the dowel s i n contracti on or constructi on j oi ntswhere the al l owance of such a tol erance wl l expedi te constructi on .For dowel ed expansi on j oi nts, the dowel s shoul d be pl aced at themddepth of the slab wth no tol erance al l owed i n posi ti oni ng thedowel s . Al l dowel s shoul d be strai ght, smooth, and free fromburrs atthe ends . One-hal f of each dowel shoul d be pai nted and oi l ed orgreased thoroughl y to prevent bondi ng wth the concrete . Dowel s usedat expansi on j oi nts shoul d be capped at one end to permt unrestrai nedmovement of the dowel s when the expansi on j oi nts cl ose .

Tabl e 7-1 . Dowel ed J oi nt Desi gn Requi rements

b . Keyed j oi nts . As wth dowel s, keyed j oi nts are constructed toprovi de l oad transfer at the j oi nt . The structural adequacy of keyedconstructi on j oi nts i n ri gi d pavements, however, can be impai redseri ously by such factors as : (a) smal l changes i n the dimensi ons ofthe key, and (b) posi ti oni ng the key other than at the mddepth of theslab . Exceedi ng the desi gn val ues f or the key dimensi ons produces anoversi ze key whi ch can resul t i n fai l ure of ei ther the top or bottomedge of the femal e side of the j oi nt . Siml arl y, constructi on of anundersi ze key can resul t i n sheari ng off the key . Keyed j oi nts shoul dnot be used i n ri gi d pavements 8 i nches or l ess i n thi ckness exceptwhere ti e bars are used . Detai l s of the requi red dimensi ons for keyedj oi nts are shown on Standard Mobi l i zati on Drawng No . XEC-006 . I tshoul d be noted that the verti cal and hori zontal dimensi ons of the keyare expressed as a functi on of the slab thi ckness . Consequentl y, the

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Pavement Thi ckness (i nches)Dowel Dameter and TypeMaximumDowel Spaci ng(i nches) :

Less than 83/4-i nch bar

8 to 111-i nch bar

12 t o 151-1/4-i nch bar

Expansi on J oi nts 9 10 12Contracti on J oi ntsRei nforced Pavement 11 12 14Nonrei nforced Pavement 18 20 24

Constructi on J oi nts 12 13 15MnimumDowel Length(i nches) 15 16 18

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correct dimensi ons for the key must be determned for each thi ckness ofpavement . For al l thi cknesses of pavement where keyed j oi nts may beused, however, the center of the key shoul d be l ocated at the mddepthof the sl ab .

c . Thi ckened-edge j oi nts . Thi ckened-edge type j oi nts may be usedfor al l types of expansi on j oi nts wth the excepti on of transverseexpansi on j oi nts wthi n ri gi d pavements . Wen thi ckened-edge j oi ntsare used, the amount of i ncreased thi ckness at the edge shoul d beapproximatel y one-fourth of the desi gn thi ckness of the mai n porti on ofthe pavement . The thi ckeni ng shoul d start at a di stance of not l essthan 3 feet f romthe j oi nt and taper uni formy to the ful l requi redthi ckness at the j oi nt .7-3 . J oi nt spaci ng . For improved pavement performance and l owermaintenance costs, i t i s desi rabl e to keep the number of j oi nts to amnimumby using the maximumj oi nt spaci ngs that wl l sati sfactori l ycontrol cracki ng . Under certai n condi ti ons where temperature changesare moderate and hi gh humdi ty prevai l s, j oi nt spaci ngs greater thanthose i ndi cated herei n may be sati sfactory .

a . Nonrei nforced pavements . Transverse contracti on j oi nts shoul dbe constructed across each paving l ane, at i nterval s not l ess than12-1/2 feet nor more than 25 feet . The j oi nt pattern shoul d be madeuni formthroughout any maj or paved area . Each j oi nt shoul d be strai ghtand conti nuous f romedge to edge of the paving l ane, and extend acrossal l paving l anes for the ful l wdth of the paved area . The staggeri ngof joints in adj acent paving l anes shoul d not be permtted . Themaximumspaci ng of transverse j oi nts that wl l ef fecti vel y controlcontracti on cracki ng wl l vary appreci abl y dependi ng on pavementthi ckness, cl imati c condi ti ons, ef fecti ve subgrade restrai nt,coef f i ci ents of thermal expansi on of the concrete, and othercharacteri sti cs of the aggregate, cement, etc . The j oi nt spaci ngsshown i n the fol l owng tabul ati on have gi ven sati sfactory control ofcontracti on cracki ng i n most i nstances and shoul d be used as a gui desubj ect to modi f i cati on based on avai l abl e i nformati on regardi ng l ocalcondi ti ons . Experi ence has shown that under traf f i c, obl ong sl abs tendto crack i nto smal l er sl abs of nearl y equal dimensi ons . Thi s i spart i cul arl y true for thin pavements . Therefore, i t i s desi rabl e tokeep the rati o of sl ab l ength to wdth as near uni ty as practi cabl e .I n no case shoul d the sl ab l ength exceed the wdth by more than 25percent .

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PavementThickness, i nchesSpacing of

Cont racti on J oi nts, feetLess than 9 12 . 5 to 159 to 11 15 to 20More than 11 20 to 25

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b . Rei nforced pavements . Transverse contracti on j oi nts i nrei nforced ri gi d pavements shoul d be constructed across each pavi ngl ane, perpendi cul ar to the pavement centerl i ne, and at i nterval s of notl ess than 25 feet nor more than 75 feet . A l owabl e slab wdths orl engths can be determned di rectl y fromfi gure 6-1 for yi el d strengthsof ei ther 56, 000 or 60,000 l b/ i n2 . Each j oi nt shoul d be strai ght andconti nuous fromedge to edge of the paving l ane and shoul d extendacross al l paving l anes f or the ful l wdth of the paved area .7-4 . J oi nt seal i ng . A l j oi nts i n rigi d pavements shoul d be seal edwth a seal i ng compound t o prevent i nf i l trati on of surface water andsol i dmateri al s i nto the j oi nt openi ngs . I n areas of heavy spi l l age ofdi esel fuel or l ubri cants, a j et- fuel -resi stant seal ant wl l be used .I n some cl imates, j oi nt seal i ng may not be requi red . Local sources ofi nformati on, such as state highway departments, shoul d be i nvesti gated .