const handbook pcc pavement rehabilitation 014728

7/30/2019 Const Handbook PCC Pavement Rehabilitation 014728

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0 Construction HandbookUS,Decxrrtment on PCC Pavementof ran sport at ionFederalHi~hwaY Rehabilitation~dminist6tion

January 1984

Prepared byConstruct on andMaintenance Division


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PREFACE

This handbook i s pr im a r i l y in tended to a ss is t the Federal H ighwayAdmini s t r a t i o n (FHWA) a rea en gin ee rs when th ey make highwayconst ruc t ion inspec t ions . It can also be used when reviewingsp eci f ica t ion s, supplemental spe ci f ic at io ns , and spec ia l pro vis io nsdur ing the PSLE stage of a project . It s a companion to the des igno ri e n te d FHUA notebook e n ti t l e d , "Techniques For Pavement Rehabili a t i on."I n fo rm a t i on con ta ined he re in i s a gu ide and i s no t i n tended as astandard. St ate highway agencies should use o r develop t h e i r ownspec i f i ca t i ons . The in form at io n i n t h i s handbook was sele cte d f romcurrent repor ts prepared by the Transportat ion Research Board underthe National Cooperative Highway Research Program, Michael I. ar tero f th e U ni ve r si ty o f I 1 n o i s, th e Por t1and Cement Association, theAmerican Concrete Pavement As so cia tion , and se ve ral State highwayagenc ies. Most o f the tab les and f igure s conta ined i n th i s handbookwere du pl ic ate d f rom the reference repor ts. The number o f d i f f e r e n tre ha b i l i t a t i o n t echniques covered i n t h i s handbook a re 1 im i e d a t t h i st ime. However, t he handbook w i l l be expanded t o inc l ud e ad di t io na lc o n s t ru c t i o n t e ch n iq ue s f o r r e h a b i l i t a t i n g r i g i d and f l e x i b l e pavements.The technical guidel ines and recomnendations have been prepared tor e f l e c t the v iews and opin ions o f th e FHWA Cons truct ion and MaintenanceD i v i s i o n( HHO-30).


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TABLE OF CONTENTS

PageCHAPTER 1 Ful 1-Depth Patc hi ng o f Jo in te d Concrete Pavement 1-1CHAPTER 2 Fu l 1-Depth Re pa ir o f Co ntin uo usly Re in fo rc edCo nc re te Pavement (CRCP) 2- 1

CHAPTER 3 Par t i a l -D ept h Patch ing o f Concre te Pavements 3-1CHAPTER 4 Subsea1i g and Sl ab ja ck i ng o f Concrete Pavements 4-1CHAPTER 5 Diamond G r i nd i ng o f J o in te d Concrete Pavements 5-1

CHAPTER 6 Bonded PCC R esu rf a ci ng Over E x i s t i ng ConcretePavements 6-1REFERENCE R-1


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1. Break up and Clean out (Acceptable - w i t h c a u t i o n )a. Advantages - Pavement breakers can e f f i c ien tA f r on t -end l oader o r backhoe w i t h a bucket

remove the broken concrete and load i t n t oopera t ion shou ld proceed f rom the center o fsaw cu ts a t the ends t o e l im ina te damage to the ad jo in ing s labs .b. Disadvantages - This method usual ly d is turbs the subbaselsubgrader e q u i r i n g e i t h e r re p1acement of subbase mater ia l or f i l l i g wi th concrete.It can a lso damage the ad jacent s labs, p a r t i c u la r l y a t the bottom.

2. L i f t Out ( Pr ef er re d )a. Advantages - This method general ly does not dSsturb the subbase anddoes not damage the adjacent slabs. It ge ner a l l y p rov ides a m orera pi d removal than th e break up and c lean o u t method.b. Disadvantages - Disposing o f la rg e pieces o f con crete may cause a problem.L i f t i n g p i n s and heavy 1 f t i n g eq uip me nt u s u a l l y a r e r e q u i r e d f o r t h e

l i f t out . Otherwise the s la b should be sawed i n t o small p iece s so th a tt hey can be 1 f t e d ou t by a f r o n t end loader.The t ransverse boundaries o f the patch shou ld be sawed t o f u l l depth w i th d iamondsaw blades. A wheel saw (hav ing carb ide s te el t i p s ) c+n be used t o make widecu ts on each ' s ide o f t he pa tch so t he cen te r po r t i on can be l i f t e d ou t.When using t h i s process, fu l l - de pt h d iamond saw cu ts s u l d be made j u s t outs ideth e wheel saw cu ts because th e wheel saw produces a r a g e d edge t h a t promotesexcess ive spa1 1 n g a long the jo in t .P rocedures used fo r removal shou ld no t sp a l l o r c rack d jac ent concre te andshou ld no t d i s t ur b the subbase or subgrade. Th is requfres th a t the fo l low ingaspects be considered. !1. Heavy drop hammers should not be allowed on the jdisturb the base and damage adjacent sound concre2. Hydro hammers (l a r g e automated jackhammers) shoul n o t be all ow ednear a p a r t i a l depth saw j o i n t because i n most i n tances t hey cancause under break ing i n the a d jacent s lab . P3 . Saw cuts can be placed t o r e l i e v e pressure whenever th e temperature i ssuch th a t t he sawn c u t has c l osed and spa l l n g w i l l r e s u l t when the

e x i s t i n g s la b i s b ro ke n o r l i f t e d o ut. A r e l i e f c u t t h a t s ho uldprov ide adequate resu l t s i s shown i Figure 1-1.4. Concrete between narrow ly spaced saw cu ts a t th e end o f a patc hshoul d be removed w it h a i r hammers (3 0 t o 40 pounds) and hand tools.A f t e r th e e x is t i n g concre te has been removed, the basejsubgrade shou ldbe examined t o determ ine i t s cond i t ion . I f water o r excess ive mois turee x i s t s i n t h e p a t ch a rea, i t shou ld be removed o r dr ie d before t he patchc o n c re t e i s p la ce d. I f a d ra inage p rob lem ex i s t s a t t he pa tch s i t e , i tshoul d be co rre cte d ( i e., out1e t d ra in , t ransverse dra in , edge dra in ,e tc . 1. I f a se r i ou s d ra inage prob lem ex i s t s , t he con s t ruc t i on eng inee rshoul d requ est a d ra i nage anal y s i s. The fo un da tio n shoul d be recompactedus ing mechanica l equ ipment t o th e s a t i s fa c t io n o f the eng ineer.


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An a l t er na t i ve method t o compacting d is turbe d base ma ter ia l i s t o removethe l oose base ma te r i a l and back f i l l w i th the PCC patch. However, t h i smethod w i l l produce pavement s labs wi th d i f f e r e n t i a l th icknesses which may ormay not cause differential frost heave problems and may also create drainagep ro b l ems.The tim e in t e rv a ls between sawing, concre te removal , and patching shouldbe c lose ly spaced t o reduce o r e l im ina te any po te n t ia l f o r s la b creep . Slabcreep causes many problems such as red uc tio n o f lo ad tr a n s fe r developed byaggregate in ter lock and 1 oseni ng o f seals i c o n t r a c t i o n j o i n t s .

/ 3 IN I ,-FULL DEPTH CUT )

SAW CUTS FOR LIFT OUT METHODFigure 1-1

Where trans verse j o i n t s are staggered, bond breaker ma ter ial should be placeda long th e long i tud ina l j o i n t ( see F igure 1 -2 ). Fa i lu re t o use a bond b reakeri n t h i s s i t u a t i o n w i l l u s u a ll y cause a c o rn e r cra ck a t t h e l o n g i t u d i n a l andt ransverse jo in ts .

Figure 1-2

1 = Transverse Jo int

Transverse Joint-Y ' -

Patch +- Fixed End


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Dowel and Rebar PlacementWhen sp ec ifi ed , h oles should be dr il le d in to the fa ce iof t he ex ist in g sla ba t the sp ec ifi ed diameter. The diameters of the holela rg er than t he dowels or reb ar t o provide proper a1 ilocated a t mid-depth of the s lab and spaced as in dicaDowels should be carefully aligned (within 114 inch)pavement and para lle l t o the plain of the sur face inmovement. The ho les can be d r i l l e d ra pi dl y by pl ac inth a t holds i t in the proper pos i t ion and provides thebi t into the concrete by 1ever actio n. Tractor-mounted equipment i s avail ab let o d r i l l mu1 tip 1 e h oles a t the same time.A quick setting, non-shrinking mortar or a high-viscosity epoxy can be usedt o permanently anchor th e dowel o r reb ar in th e hole. The hole s should becomplete ly fi l led around the dowels and rebars to insure that they arepermanently fasten ed to the ex ist in g concrete. The bars should be dipped inthe epoxy or grout and worked back into the holes for complete coveragearound the bar so th at i t will be secur ely fixe d in to place. The end of thedowel bar t h a t extends i nt o th e patch area should be greased t o provide fr eemovement. Other suitable bond breaking materials can be used besides grease.Corrosion of dowel b ar s has become a common problem in a re as where dei cingchemicals ar e used. For th a t reason, the use of coated dowel bar s o rcorro sion r e s is ta n t dowel b ars i s recommended.Concrete Placement and FinishingSome of the c r i t i c a l aspe cts of con crete placement and fini sh ing include(1) adequate consol ida t ion , (2 ) avoiding a mix th a t i s e i th e r too s t i f f orhas too high a slump, and (3 ) ensuring a leve l str ik e- of f fi ni sh .1. Each patch should be cast in one continuous full-depth operation.The concrete should be consolidated in place by use of an internaltype vi br at or . The con crete should be con solid ated around the edgesof the patch and inte rna l ly. Internal vi bra tors for conso l idat ingthe concrete should be of an approved mechanical spud typ e. Thevibrators should be capable of vis ibly affect ing the concrete for adistance of 12 inches from the vibrator head.2. The concrete mixture should have a slump of approximately 2 to 4inches a t the patch s i t e fo r bes t p lacement. However, t h i s may vary

depending on additives and construction conditions. A mix too st i ffor too f l u i d could provide s er io us placement problems. The use of asuperpl a s t i c i zer as discussed previously can he1 p i n providing aworkable mix ture. Workmen should no t add exc ess ive water j u s t t oget a highly flowable mix as this will weaken the concrete and causehigh er shrin kage. Workmen shou ld al so not add water to th e sur fa cewhen f inis hin g the concrete because t h is too wil l adversely aff ec t thedurabl i ty of the concrete surface.3. Short patches that are general ly less than 12 feet can be screedede i the r t r a nsve rse ly o r l ong itud ina l ly . If a pavement i s ru t te d,scr eed i ng i n the longitudinal d irec t ion ( pl acing th e scree d para1 l e lt o th e c en ter l in e) may be pref erab le because th e patch will match th eex ist in g cross sectio n of th e pavement. For patches over 12 fe et i nlength, the screed should be placed perpendicular t o th e c ent erl ine .


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W hile t h e co nc re te i s s t i l l p l a s t i c , t h e c o n t r a c t o r s h o ul d t e s t th e p at chs u r f a c e f o r t r ue n es s and f o r b e i n g f l u s h w i t h t h e edges o f t h e a d j ac e n ts l a bs b y us e o f a s t r a i g h t e d g e a nd i n ac co rd an ce w i t h t h e f o l l o w i n g .1 . For pa tches 10 f e e t o r l e s s i n l e ng t h, t h e s t r a i g h te d g i n g s ho ul d b edone by p l ac i ng t he s t r a i gh t ed ge pa ra1 e l t o t h e pavem ent cen te r 1 new i t h t he ends r es t i ng on t he e x i s t i n g pavem ent and d r aw i ng t he s t r a i g h t -edge ac ross t he pa tch . The s t r a i gh t e dge shou l d be i n con t a c t w i t h t h ee x is t in g pavement whi 1e draw ing i t ac r oss t he pa t ch and any h i gh o r 1owspots exceea ing 118 i n c h sh ou l d be co rr ec t ed . I f a n y c o r r e c t i o n s a r emade, th e s urfa ce sh ou ld be rechecked.2. A l l t ra n s v e rs e a nd l o n g i t u d i n a l j o i n t s s h o u ld be edged ( e i t h e r b yt o o l i n g w h i l e t h e c o n c re te i s p l a s t i c o r b y sa win g) t o p r e v e n t c h i p pi n gand subsequent spa1 1 n g o f th e edges.3. The su r f ace o f t h e conc r e t e shou l d be t ex t u r e d t o m atch t h e su r r ound i ngpavement, except when a gr in di ng op era t io n fo l lo ws .Cu r i ng and Opening t o T r a f f i cAMBIENT TEMPERATURE AND THE TEMPERATURE OF THE CONCRETE AT THE TIME OFPLACEMENT HAVE BEEN FOUND TO BE THE MOST CRITICAL FACTOR I N THE STRENGTHDEVELOPMENT OF CONCRETE PATCHES. The tem pe ra tur e i n th e pa tc h co nc re tew i l l be h i ghe r t han am b ien t o r c y l nde r lbeam tem pera tu res. T h i s d i f f e r e n c eranges f rom 10' t o 30F a t 4 hou rs a f t e r p l acemen t f o r non - i nsu l a t ed pa tches .Concrete cur ing compound should be added as soon as the concrete sur facehas se t su f f i c i e n t l y t o app l y t he cu r i n g agen t w i t h ou t damage. The cu r i ngcompound s h ou ld b e a p p l i e d i m me d ia te ly a f t e r t e x t u r i n g a t t h e r a t e o f1 g a l l o n p e r 150 square fee t .Po r t l and cem en t conc r e te pa t ches shou l d no t be p l aced when t he a i r o r basem a t e r i a1 t em per a tu r e i s be1ow 40F un les s th e pa tc h i adequate l y i nsu la ted .I n su l a t i o n b l anke t s hav i ng a minim um t h ickness o f 2 inches should be used.Edges and seams i n th e b la nk et sh ould be secured to p r ev e nt p e n e t r a t i o n o fwind. Tes t beams o r cy l i n d e rs s hou ld be cure d the same as th e patc h on th ej o b s i t e . I n s u l a t i o n may be u se d t o i mp ro ve t h e r a t e o f c u ri n g . I f ani n s u l a t i o n b l a n k e t i s p la c ed o v e r t h e p atc h, t h e t em p er at ur e d i f f e r e n t i a l a t4 ho urs may be as h i g h as 40F. Thus, f o r r a p i d c u r i n g ( p a r t i c u l a r l y i n c o l dweather ) , i t s s t r o n g l y recomnended t h a t i n s u l a t i o n b l a n k e t s b e p l a c e d o v erth e patch. Class E (ASTM C-208) in s u la t i o n board works w el l and i s mores t a t i o n a r y t h a n b la n k e ts .Po lye thy len e sheet i ng shou ld be p lac ed on th e concre te sur face be forep l a c i n g t h e i n s u l a t i o n . The w/c r a t i o and r a p i d s e t t i n g a d d i t i v e s s uch asc a l ci u m c h l o r i d e a l s o have a s i g n i f i c a n t e f f e c t on r a p i d s t re n g t h d e ve lo pm en td u r i n g t h e f i r s t few h o u rs a f t e r p la ce me nt. The shor tes t cur i ng t ime can beob t a i ned by us i ng a com b ina t ion o f ca l c i um c l o r i d e , s u pe rp l a s t i c i z e r andi n s u l a t i o n b la n k e ts , Type I 1I ement, and se t - r e ta r der ( i f needed). Tab le 1-1prov ides recommendations on e a r l y opening o f con cre te pa tches.P le as e n o t e t h a t t h e d a t a i n T ab le 1-1 i n d i c a t e s t h e s t r e n g t h v er su s t i m e f o ra 7 bag mix . The more commonly used 8 and 9 b a g m i x e s p r o d u c e s i g n i f i c a n t l yh i g h e r e a r l y s t r e n g t h c on c re te .


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There a r e ge ne ral ly two c r i t e r i a t h a t may be used t o sp ec ify when patches canbe opened t o t r a f f i c .Most often, SHA's specify the minimum strength of,beams or cylinders.The minimum str en gt h befo re a patch can be openedi'to t r a f f i c va ri eswidely between agen cie s (e.g., 300 t o 650 ps i modA modulus of rup ture of 300 psi f o r cen ter po intfo r t h i rd po in t 1oadi ng, or 2500 psi f o r compresscured si mi lar t o the patch are bel ieved t o be adetr af f i c . The actual strength of th e patch wil l bor cyl inders because the temperature i n the patchthe heat of hydration.An SHA could sp ec ify th e mixture and curin g procedures and the n, basedon tes t i n g re su l t s , s e t the minimum time to opening t o t r a ff ic . I ft h i s i s done, th e time t o opening should be dependent upon th e ambienttemp erature a t time of placement. The recommendations i n Table 1-1 arebased on lab orat ory and f ie ld t e s t s conducted by th e Department of C ivilEngineering a t th e Unive rsity of I1 li n o is . These recommendations shouldbe carefully considered by an agency before adopting and should bead jus t ed to loca l con ditio ns where needed. This data i s under eva luat ion 'and may be modified in the future.

Tab le 1-1. Example Minimum Opening Times f o r Concre te Pa tch esAmbient Minimum Opening Times (Hours)***Temperature Regular Patch with Addition ofA t Pl acement Regul ar* Super Fi berg1 ass** Super P la st ic iz er

( O F ) Patch P l a s t i c i z e r Insulat io n and Insulat io n

Note: *Regular patch - 7 bags/cu.yd., 2 percent calcium chloride, Type I cement,w/c - 0.4**In sula tion should not be used when th e ambient temperature i s gre ate r.

***Opening times (hou rs) a re given f o r a modulus of 250 psi ( t h ir d poin tloading) , or 300 psi (center point 1oadi ng) fo r th e patch concrete.


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Method o f PaymentBased on the d i f fe ren ce i n u n i t cos t between small a rea pa tch ing and la rg ersla b requirement, two o r more pay i tems should be inclu ded i n the pay schedule.For example, one agency has th e fo l lo w in g th re e size s: Type I l ess t han5 square yards , Type I 5 t o 15 square yards, and Type I 1 - greater than15 square yards.


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CHAPTER 2FULL DEPTH REPAIROFCONTINUOUSLY REINFORCED CONCRETE PAVEMENT (CRCP)

I n t r o d u c t i o nCe r ta i n types o f d is t r es s a r e un ique t o CRCP and conven t iona l methods o fr e h a b i l i t a t i o n u se d f o r j o i n te d c o n c re te p ave me nts may n o t a p p l y t o CRCP.The most common d is t r e s s i n CRCP i s an edge punchout which i s s im plya s e c t i o n o f c o n c re te b etw ee n t r a n s v e rs e c ra c k s t h a t i s d e pres se d (p un ch eddown) b e lo w th e s u r f a c e o f t h e s u r ro u n d in g s l ab .Patch Boundar iesI n mo st c as es t h e b as e ma te r i a l b e ne a th a n edge p u nc ho ut i s d i s i n t e g r a te don a1 1 s i de s o f t h e d i s t r e s s ( t y p i c a l l y 2-3 f e e t ) . T h er e fo r e, t h e o v e r a l la r ea o f t h e p a t c h s h o u ld i n c l u d e t h e d e t e r i o r a t e d base m a t e r i a1.T ie d S te e l P a t c hThe d is t res sed po r t io ns o f t he CRCP and base shou ld be inco rpo ra te dw i t h i n t h e c e n te r s e c t i o n o f t h e pa tch . The end sect ion s and th e cent ers e c t i o n o f t h e p a t c h s h o u ld b e a m inimum o f 2 f e e t l o n g ( s e e F i g u r e 2-1).

6 FT. MIN. 12 FT, MIN. 2 FT. MIN, _L 2 FT, RIN,r

LPARTIALEPTHSAW CUT

ENDSECTION

\'FULL DEPTHSAW CUTF ig u re 2-1

CENTER _SECTION . END aSECTION


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Welded Steel PatchThe dis tre ss ed p or t i o n o f the CRCP and base should be inco rpo rate d w it h int h e c e n t e r s e c t i o n o f t h e p a t c h . The end sect ion of the patch should be aminimum o f 8 i nches long (see F igure 2-2).

I- 4 f t. min. 4

Figure 2-2

Minimum Distanc e t o CrackThe ou ter p atch boundaries should be loca ted a t l e a st 18 inches fromth e nearest t ransverse crack (see F igure 2-3).

ST

F i g u r e 2-3

Sometimes the crack spac ing i s sm al l and i t i s n e ce ss ary t o p l a c eth e boundary c lo se r than 18 inches; however, i t shou ld no t be c loserthan 6 inches. The outer patch boundar ies should not c ross a t ransversecrack because i t may lead t o spa1 in g and breakup i n the s lab.Width o f PatchI n m ost i n s ta n c es t h e w i d t h o f t h e p a t c h w i l l be eq ua l t o a f u l l l a ne w id th .D is tr es s type s such as wide cracks, la rg e edge punchouts, blowups and ot he rd is t res ses occu r r ing over more than h a l f o f th e lane shou ld be patchedo ve r a f u l l l a n e w i d t h ( 12 f e e t ) .


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I n some cases, such as a small edge punchout, t h e wid th o f th e pa tch needno t be a f u l l 12 fee t . I n these cases, a lon g i tu d in a l boundary can bees tab l i shed . A minimum patch wid th o f 6 feet should be used. Patch widthsbeween 6 and 1 2 fe e t can be used as lon g as th e lo ng i tu d in a l boundary i sp laced be tween the re in fo rcement and the jo in t does no t fa1 1 i n t h e c en te rof the wheel path.F ai lu re Across Two or More Tr a f f i c LanesWhenever a f a i l u r e occurs acro ss two o r more lanes, it i s b e l ie v ed t h a t t h ef o l l owing simp1e procedures w i 1 p r o v id e a d d i t i o n a l performance.1. P a t c h t h e p a s s i n g l a n e f i r s t .2. Next patc h th e heavy tr u c k lane.The above sequence i s recomnended because th e f i r s t patch w i l l c rack morethan th e second pa tch because th e f i r s t pa tch has t o w i ths tand most o fthe stresses caused by slab movement. P l a c in g t h e p a tc h a t t h e e nd o f i t se xp an sio n c y c l e ( g e n e r a ll y i n t h e 1a te a f ternoon) can reduce cru sh i ngcaused by expansion. A1 so, s i g n i f i ca n t co nt ra ct io n can cause crack ing.S ince th e t ruck lane rece ives the g rea tes t l oad ings , i t i s t h a t p atc h th a ts h ou ld b e g i n i t s s e r v i c e 1 f e w i t h t h e f ew es t c r ac ks . Cracks formed i n th epass ing lane patch should not readi ly break down because of the reducedh e a v y t r a f f i c .Sawing Patch AreaS aw ing a l l t h e o u t e r b ou nd ar ie s o f a p a t c h i s r e c m e n d e d . Experiencehas shown th a t th e ou te r boundaries o f a pa tch w i l l spa11 i f c u t b yjackhammers o r oth er brea kout equipment, o r i f t h e y f o l l o w a n e x i s t i n gcrack. Consequently, th e proper sawing equi p e n t should be u t i 1 i zed and1 g h t hammers (30-40 Ibs.) sho uld be used t o remove t h e end sectio ns.The outer boundary o f the end sect ions should be a par t ia l depth saw cut 1-112t o 2 (see F igure 2-4) i nches deep tha t does no t cu t th e re i n f o r c i ng s tee l .The boundary between th e cente r sec t ion and the end se ct io n should be a f u l ldep th saw cu t th rough the re in fo rce ing s tee l .I f t h e w id th o f a p atc h i s l e s s th a n a f u l l l ane , the long i tud ina l boundarys h ou ld be sawed t o a p a r t i a l d e pt h i n o r d e r t o p r o v i d e an i r r e g u l a r f a c efo r be t te r bond and aggrega te in te r lock .

CENTER SECTIONBREAK OUT

Figure 2-4


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Concrete RemovalThere ar e ba sic al ly four c on stru ctio n methods used t o remove concrete fromthe center section of a patch area.1. One procedure i s t o break up the concrete with jackhammers and shoveli t out with hand too ls. The advantages of this method are that aminimum of equipment i s needed and i f th e work i s done c a re fu l ly ,damage t o the base and the adjacent sla b i s avoided. Unfortunately,t h i s i s th e most time consuming, labor in te ns iv e, and the most expensivemethod.2. The removal process can be shortened by using a pavement breaker and abackhoe. Breaking th e con cre te by dropping a wrecking bal l or using adrop hammer should not be permitted because the shock waves can damage

the adjacent concrete and disturb the base material.3. The th ir d method th at has been used successfully i s t o l i f t theconcrete using a front-end loader. The common p rocedure i s t o breakthe concrete with jackhammers on al l s id es of th e ce nt er secti on . Thefront-end load er i s used t o 1 f t one end of the slab. Chains areconnected t o the exposed s te el a t the o ther end of th e sl ab and securedt o the bucket. The sla b i s then li ft e d out and placed in a truck.This method can be accomplished in a shorter period of time and doesnot damage the base or the adjacent CRCP. Also, this method does notwork very we1 1 in bad ly "DM cracked material or where bituminouspatches are being removed. Disposal of the slabs can also be aproblem.4. The fourth method uses 1 fting pins. This procedure requires at leasttwo drilled holes, lifting pins, and equipment capable of liftingthe concrete slabs. A 5-inch wide st r i p of the CRCP center sectionshould be removed t o avoid binding (s e e Figure 2-5).

CENTER SECTION0Figure 2-5


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F igure 2-6 shows a t yp ic a l reusab le p in th a t has been used e f fe c t i ve ly .The ho les shou ld be pos i t i one d t o d i s t r i b u t e th e load as even ly as poss ib le .The number o f p ins used w i l l depend on th e s i ze and con di t io n o f th e s la band on the capac i t y o f the cha in . This method can be accomplished quicklyand norm ally le aves th e base m at er ia l and adja cen t CRCP undis turbe d.Swivil

F igu re 2-6End SectionRemoval o f t he concrete f rom the end sect ion s should be per formed i n thefol lowing manner (see Figure 2-7).1 . The concrete i n th e two end sect ions should be ca re fu l l y removed so asn o t t o damage t h e r e in f o rc e m e n t i n t h e l a p a re a, and t o a v o i d s p a l l i n ga t t h e b o tto m o f t h e j o i n t b en ea th t h e p a r t i a l d e p th saw c u t. Thistask should be acompl ished by using l i g h t jackhammers (20 t o 40 l b.range) and hand tools.2. The re in forcement should not be bent dur ing removal o f the concretes ince th e bars cannot be pro per ly s t ra ightened af terward. Bentre in fo rc em en t i n t h e p a tc h are a w i l l r e s u l t e v e n tu a ll y i n t h e s p a l l i n gand f a i l u r e o f t h e p a tc h because o f t h e l a r g e e c c e n t r i c s t re s s e sc a r r i e d by t h e r e i nforcement. Removi ng th e conc rete around th e r e i n f o r c -

i n g s t e e l w i t ho u t b e n di ng o r dam aging t h e s t e e l i s d i f f i c u l t .3. The use o f a drop hammer o r hydrahammer sho uld n ot be used i n th eend sect io ns because th i s equipment w i l l usual ly damage the re in force-ment and/or cause ser ious undercut t ing beneath the par t ia l depth sawedjo in t. As note d above, i t i s n ecessary t o l i m i t t h e s i z e o f t h ejackhammer opera t ing a t t he j o in t t o m in im ize unde rcu t t i ng benea th thereinforcement.


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4. I f a r e i n f o r c i n g r o d i s m i st a ke n ly o r a c c i d e n t a l l y b en t, i t shouldbe ca re f u l l y and accu ra te ly r ea l i gned a f t e r t he b reakou t o f t heconcrete.

Figure 2-7Eva lua te th e Cond iton o f the BaseThe base should be undisturbed, sound and fre e o f mo isture. I f the basei s d is turbed, the loose ma ter ia l should be compacted. I f a dra inageprob lem ex is ts , i t shou ld be cor rec ted ( i e., ou t l e t d ra in , t ransversedr ain , edge dra in, etc.). I f a ser ious dra inage prob lem ex is ts , thecon stru ct on engineer should request a dra inage analy s i s.Tied ReinforcementThe same s i ze r e in fo rc in g rods should be p laced i n the patch and spl i ce dt o th e re inforcement a t the ends of t he patch by lappling. The re qu i re dlength o f embedment o f t he ex is t in g re in fo rcement in to t he pa tch depends onth e s iz e and type o f th e re inforcemen t. The minimum embedment leng ths a re 18inches for a No. 5 deformed bar and 21 inches f o r a No. 6 ba r (see Figu re2-8). A minimum 2-in ch clea ran ce shou ld be prov ided between the ends o f th enew rebars and the ex is t ing CRCP face t o a1 low f o r po b$ ib le expansion. Thenumber and spacing o f th e new reinforcement should match th e e x is t i n gre inforcem ent i n the pavement. I

I

i18" for No. 5 bar21" for No. 6 bar

END SECTION

2' CLEARANCE

F igu re 2-8


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We1 ded ReinforcementAn a l t e r n a t i v e t o t i e i n g t h e r en fo rc em en t i s t o w e ld t h e r e in f or c em e n tus ing e i th e r a double 4 - inch we ld o r a s in g l e 8 - inch we ld (see F igu re 2 -9 ).1. The welds should be 114 inches and should be continuous.2. We lding r a i l s t e e l (ASTM A616 and AASHTO M42) shou ld not be permi t tedbecause the inhe ren t b r i t t le ne ss o f the s te e l can cause the we ld t of a i l .3. AWS A5.1 E70xx electrodes should be used.4. Arc s t r ik e s outs id e o f t he weld area and tac k weld ing shou ld be p ro h ib i t e d .5. To avo id pote nt i a l buckl ing , th e re in forcement shou ld be lapped and t i e d a tthe cen ter o f the patch. The minimum l a p len gt h should be 16 inches f o r aNo. 5 bar and 19 inc hes f o r a No. 6 ba r ( see Fi gu re 2-10).6. Re in fo rc in g bars should be dr y when welded.

NEW REINFORCING BAR4" WELD

EXISTING REINFORCING BAR

8" WELD NEW REINFORCING BAR

EXISTING REINFORCING BAR

Figu re 2-9


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L16"-No.5 Bar 719"-No.6 Bar

F ig ure 2 -10 IP l acementThe new r e i n f o r c i n g s t e e l s h o u l d b e p l a c e d a s f o l l o w s1. R e i n f o r c i n g s t e e l s h o u l d be p la c e d w i t h a m i ni m um / of 2 -1 /2 i n c he sof cover . I f t h e e x i s t i n g c o v e r i s l e s s t h a n 2-1A2 in ch es , p l a c e t h es p l i c e d b a r u n d e r t h e e x i s t i n g b a r .2. R e i n f o r c i n g s t e e l s h o u l d be s u p p or te d and t i e d t o c h a i r s when t h e p a t c hlen gt h exceeds 4 fee t . T h e c h a i r s p a c i n g s h o u l d b e s u c h t h a t u n i f o r m

unsuppor ted lengths do not exceed 4 feet .

r EXISTING STEEL REPLACEMENT STE ELREINFORCEMENT REINFORCEMENT

\L SUPPORTING CHAIRS

F i g u r e 2 - 11

Bond ingA n e a t cem ent g r o u t (c em en t p l u s w a t er ) s h o u l d he a p p l i e d t o t h e j o i n t f a c e simmed ia te ly be fo re concre te p lacement. The j o i n t f aces shou ld be d r y whent h e g r o u t i s a p pl ie d .


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Ma te r i a l s a nd C u r i n g and Ope nin g t o T r a f f i cSee Chapter 1. The ma te r ia ls , cur in g, and min imum opening t ime a re th esame f o r patches i n j o i n t e d co ncr ete pavement and CRCP (se e Table 1-1).Time o f PlacementThe change i n am bie nt t e m p er at ur e i n t h e i n i t i a l 2 4-h our p e r i o d f o l l o w i n gt h e placem ent o f t h e p at ch i s t h e most c r i t i c a l e x t e rn a l f a c t o r a f f e c t i n gth e success o f a CRCP f u l l d epth re pa i r . The f u l l d e pt h r e p a i r s h o u l d b escheduled, t o th e maximum ex te nt pos s ib le , when th e change i n th e ambienttemperature i a t a mi nimum.I n a d d i t i o n , c a s t i n g o f a p a t c h b e fo re noon i s n o t r ecommended, e s p e c i a l l ydu r in g th e summer months, because the expans ion t h a t g enera l y occurs i nt h e a f t e r n o o n w i l l c ru s h t h e p a tc h.Method o f PaymentF u l l dep th re pa i r o f CRCP can be pa id by th e square ya rd i n p lace.


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CHAPTER 3

PARTIAL DEPTH PATCHING OF CONCRETE PAVEMENTSI n t r o d u c t i o nThis chapter covers permanent par t ia l depth p atch ing o f p or t lan d cementconcrete (PCC) pavements. T h i s t y p e o f p a t c h i n g i n v o l v e s t h e r e p a i r o fsp a l l s a t j o i n t s and/or c racks and o the r d i s t resses w h ich can be repa i redby par t ia l depth patches .Spa1 1s t h a t ex tend be low th e m idpo in t o f t he s l ab canno t e f f e c t i v e l y bepart ia l depth patched (e.g. , pavement w i t h 'D " c r a c k i n g t h a t has d e t e r i o r a t e dthe bo tt om o f t he j o i n t s and c racks) . A f u l l dep th pa tch shou ld be p lacedi n t hese cases .The performance o f p a r t i a l depth patches has been excel l e n t on many pr oj ec ts ;however, t he performance has been u n sa ti sf ac to ry on some pr oj ec ts . Thefa i l u re s are caused by lack o f bond, compress ion fa i l u re s o f pa tches a tjo in ts , incompa t ib le patch ma ter ia l , improper use o f pa tch mater i a1 , i n s u f f i c i e n tconso l i da t i on , d i f f e rences i n t he co e f f i c i en t o f t he rm a l expans ion be tw eenth e conc rete slab and patch ma te ria l , and improper cure. The workin gt o le r a nc e s o f some o f t h e p r o p r i e t a r y p a tc h m a t e ri a l s a r e t o o t i g h t f o rnormal co ns tru ct io n prac t ices. When pro pe r ly p laced w i t h a dura ble patc hm a t e r i a l , t h e r e p a i r s h o ul d l a s t t h e r em a in in g l i f e o f t h e pavement.Ma teri a1 sThe t ype o f pa t ch m a te r i a l t ha t shou ld be used w i l l depend upon such fa ct or sas t h e amount o f t im e ava i l ab le be fo re opening t o t r a f f i c , a th i en t t em perature,cost , s ize, and depth o f patches.Po rt la nd cement concrete can be form ulated t o produce ac celera ted st ren gthgain by using Type I r Type I 11 p or t lan d cement and ca lc ium ch lo r id e (o ro the r acce le ra to r ) t o o b ta i n a minim um s t reng th o f 3000 ps i i n 24 hours,The p la s t i c conc rete shou ld have an a i r con ten t o f 6 2 2 percent. The slumpshould be 1 t o 2 i nches a t the t ime of p lac ing. Type I1 1 cement, w it h andwi th ou t admixtures, has been used f o r patc h mixtu res lon ge r and more w id elythan most o ther mater ia ls . It i s l ow cos t , ea s i l y ava i l ab le , and s im p le t ouse. The s t reng th ga in o f r i c h m ix tu res (u p t o 8 bags) i s r ap id d u r i ng warmweather and can be used when ea r ly o pening (4 t o 6 hours) t o t r a f f i c i srequi red. One d isadvantage i s th a t i n coo l o r c o l d weather the r a t e o fs t reng th ga in m a y be t o o s lo w t o p e r m it q u ic k o pe nin g t o t r a f f i c . P o r t l andcement grout can develop an adequate bond f o r pa tches opened t o t r a f f i c i n 4t o 6 hours, however, i t i s ques t ionab le i n coo l t o co ld weather. An epoxybonding agent can be used t o produce h igh e a r l y bond s t reng th i n both hot andco ld weather. The engineer should be assured th a t th e epoxy bonding agent i sc o mp a tib le w i t h t h e p a t ch m ix and t h e e x i s t i n g c o n c re t e p r i o r t o i t s o p e r a t i o n a luse.


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Normal s e t (3000 psi in 3 days) po rtland cement co nc re te patch ma ter ial smay be used where the patch i s prote cted from t r a f f i c f o r 24 hours o r more.A cement grout (disc usse d l a t e r in more d e t a i l ) may be used as a bondingagent. The patch mixture should be placed and con solida ted t o elim ina tees se nt ia l ly a l l voids a t the inte rfa ce between the patch and adjacentconcrete. All patches should be f inis hed t o the cross-sec t ion of theexisting pavements.A high percentage of re pa ir p roje cts r equ ires patches t o be opened t ot r a f f i c w i t h i n 4 t o 6 hours. To meet t h i s sche dule , a wide va ri et y ofrap id se t t i ng and/or h igh ear ly s t reng th patch ing mater ia l s ar e avai lab le .When using a proprie tary patching material , i t i s important th at them an ufa ctu rer 's recommendations be followed cl os el y. Handling, mixing,placement , onsol id at io n, scr ee di ng, and curin g of th e patc hing m ateri a1should be in accordance with the manufacturer's written instructions.The SHA should review and/or t e s t th e various patch m ate rials t o determinet h e i r compati bi 1 ty and performance with the ex ist in g concre te.Detailed information on patch material perforyance can be obtained fromt h e FHWA Report No. FHWA-RD-74-55, e n t i t l e d , C oncre te Pa tchi ng Materi a1 s. "Av ailab le epoxy re si ns have a wide range of se tt in g times. Epoxy concretemixes should be compatible w i t h the con cre te in th e pavement. Differenc esin the co ef fic ie nt of thermal expansion can cause a patch t o fa i l .Preparation of Patch AreaThe success of partial depth patching depends upon developing an adequatebond to sound ex is t in g con crete so i t i s important tha t proper surfacepre par atio n be done. This involves sounding th e ex ist ing co ncr ete with ast ee l rod, c ar pe nte r's hammer, chain or other device to determine th e patch1 mits. Frequently, a1 1 th e delaminated con crete i s not removed. The refo re,the patch limits should be extended beyond the detected delaminated orspal led area by 3 t o 4 inches to assu re removal of a l l unsound concrete.A 2-inch deep saw cut should be made around the perimeter of the patcharea to provide a ver t i ca l face a t the edge. When hard ag gr eg ate ex i s t s , a1-inch depth saw cut i s adequate. Vertical faces are necessary when usingPCC as the patch material . Ve rtica l f ac es may not be necessary f o r ce rt ai ntyp es of patch ing mate ri a1 s such a s polymer con cre te and epoxy co nc re te.Manufacturers of these types of materials make claims that the bondingstr en gt h of t h e i r material i s stron g enough t o be used on tapered edges.St at es should assu re themselves th a t such claims ar e valid. Manufacturersof proprietary patching material such as polymer and epoxy concretes, tryt o off se t the genera l ly higher cos t of th e patching material by el iminat ingth e ne& f o r a sawed ver t ica l join t .Concrete within the patch area should be removed with pneumatic toolsun ti l sound con crete i s reached. I f the unsound con crete extends below th edowels , s t rong co nsidera t ion should be given t o fu l l depth rep ai r of thej o i n t .


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Where spalling has been caused by a metal in s e r t such as a un i tube, thes p a l l s u s u a l l y s t a r t a t t h e b ot to m f i n o f t h e i n s e r t a bo ut 2 -1/2 in ch esbelow the surface. When rep a i r i n g th i s t ype o f s pa l l , i t i s recommendedt h a t t h e i n s e r t b e sawed ou t a l on g t h e e n t i r e l e n g t h o f t h e j o i n t t o a v o idf u r t h e r s p a l l s . The joints can then be resealed.Small spa l 1 a reas a long jo in ts gene ra l l y do no t need re pa i r and the 1 m i t son t h e s i z e o f t h e s p a l l s b e f o r e re p a i r, i f required, can be set. Forins tance, areas le ss than 6 i nches i n l eng th and 1-1 /2 inches i n w id th a tt h e w i d es t p o i n t need n o t be r e p a i r e d b u t f i l l e d w i t h a s e a l a nt ( u n le s s apreformed compression seal i s t o be used, then even smal l s p a l l s must berepaired.When removing th e co ncre te w it h in th e p atch area, it i s i m p o rt an t t h a tproper equipment be used i n order t o prevent f r a c t ur in g t he concrete be lowth e patch. Fra ctu red concrete causes debonding o f the patch. Pneumatic andhyd rau l ic hamners should gen era l ly range f rom 15 t o 30 pounds. Heavy hamnersc an r e s u l t i n f r a c t u r i n g t h e c o n cr e te b e lo w t h e r e q u i r e d d epth.Cold m i l l i n g equipment can and i s be ing used t o remove de ter ior at ed concrete.The p r imary app l i ca t ion o f t h i s equ ipment has been t o remove la rge qu an t i t i e so f de te r io ra ted concre te usua l l y caused by TI " c rack ing o r reac t i ve aggrega te .It shou ld be no ted th a t the c o l d m i l i n g p rocess can produce f ra c tu red aggre -ga te i n the rema in ing laye r o f conc re te . For th a t reason it i s recommendedth a t the co ld m i l i n g p rocess be expanded t o remove a1 1 f rac tu red mate r ia l i no rder t o p rov ide a su r face o f sound concre te on wh ich t o bond th e p a tch ingmater ia l . It has not been determined at th is t ime whether sandblast ing canremove a l l t h e f r a c t u r e d m a t e r i al l e f t i n p la c e b y t h e c o l d m i l l i n g pro ce ss.Diamond saw ing, e i t h e r used a lo n e o r i n c o n j u n c t i o n w i t h c o l d m i l l i n gequ ipment, i s a rap id l y evo lv ing p rocess th a t may be an economical ands a t i s f a c t o r y t e c h n i qu e f o r re mo vin g s p al l e d o r d e t e r i o r a t e d c on cr ete .Af ter removal of t h e concre te , the su r face o f th e pa tch a rea shpuld be sandb l a s te d f ol lo w e d b y a i r b l a s t i n g i n o rd e r t o remove a l l l oo se p a r t i c l e s andd us t. T h i s g e n e r a l l y r e q u i r e s s h i e l d i n g from t r a f f i c i n a d ja c en t la n e s a n d/ orsome method of e f f e c t i v e dus t cont ro l .The St ate highway agency should s pe ci f y o r approve a removal process th a thas been f ie1d tested.Compression f a i l u r e a t j o in ts i s a ma jo r cause o f pa tch fa i l u res . Compressionfa i l u re s occur s im ply because the proper spac ing between the two faces o f th ej o i n t i s n o t pro vid ed . I f t h e f a c e o f t h e p a tc h ( a t t h e j o i n t ) e xt en ds beyondt h e f a c e o f t h e e x i s t i n g s la b, t h e f a c e o f t h e p a t ch w i l l become a p o i n tloa din g when the sla bs expand and th e jo i n t goes i n t o compression. Du ringce r t a i n per iods o f t he yea r when n ig hts a re cool and daytime temperatures areh igh , the expans ion and con t rac t ion cyc les become more c r i t i c a l i n pa r t i a ldepth patches.


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I n or de r t o e l im i n at e t h i s t y p e o f f a i l u r e , i n s e r t s s ho uld be pla ce d i nth e jo i n t t o ma in ta in the proper space between th e patch and the ad jacentpanel. S tyrofoam has been used f o r t h i s purpose t o separate th e patch f romthe adjacent s lab. I n a d d it io n , t h e j o i n t s ho uld be resawed t o prov id e th ep roper shape f ac to r f o r t he seal an t r ese rvo i r .P la c ing Patch Mate r i a1 sA f t e r th e patch area i s pro per ly cleaned, a bonding agent should be applied.The typ e o f bonding agent w i l l depend upon th e bond development requireme ntsf o r opening t o t r a f f i c . I f e a r l y o pe nin g i s r e q u ir e d ( 4 t o 6 hours), anepoxy agent should be used. A prime coat o f epoxy- res in b inder , th inne dw i t h th r ee pa r ts to luene t o seven pa r ts epoxy b inder , by volume, shou ld beapp l ie d t o the dry , c leaned sur face and s ides o f the r ep a i r a rea except f o rth e ad jacent jo in t face or c rack . The pr ime coat should be ap pl ie d i n at h i n coa t i ng and scrubbed i n t o t he su r face w i t h a s t i f f - b r i s t l e d brush. Apressur ized spray wou ld be j u s t i f i e d fo r la rg e qu an t i t i e s . When spray ing,care must be taken t o apply th e grout evenly. P lacement o f the concre teshould be delayed u n t i l th e epoxy becomes tacky.When pa tches can be c losed t o t r a f f i c f o r a longe r pe r i od o f t im e (24 t o72 hours), a po rt la nd cement gro ut may be used f o r bonding th e patch. Thecement gro ut should be composed o f cement and s u f f i c ie n t water t o produce amortar w i th a th ick , cream consistency. The grout i s scrubbed evenly on th edry sur face o f the patch. Excess grout shou ld not be perm i t ted t o co l l e c t i npockets. The concrete patch ma ter ial should be placed b efo re the bondinggrout beg ins to se t .When u s in g an epoxy pa tch m at er i a1, i t should be used i n accordance w i t h themanufacturer's recommendations. P r i o r t o p l a c in g t h e p atch , t h e c a v i t yi s u s u a l l y p rim ed w i t h a t h i n c o a t in g o f epoxy r e s i n b i n d e r s crub bed i n t othe su rface. The epoxy conc re te o r m or ta r i s then p laced i n t he cav i t y i nlayers genera l l y no t exceed ing 2 inches. The t ime int e rv al between pla c in go f ad d i t io na l lay ers shou ld be such th a t the temperature o f the epoxy concre tedoes not exceed 140F a t any tim e d ur in g hardening.F in i sh ing , C ur ing and Open ing t o T ra f f i cRefer t o these sec t ions i n Chapter 1 and see Table 1-1.Concurrent WorkThe f o l 1owing sequence o f op era tio ns i s recomnended.1. F u l l d e p t h r e p a i r2. Subsea1i g3. P a r t i a l d e p t h r e p a i r4. Diamond g ri n d in g5. Jo in t and c rack resea l ing


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Measurement and PaymentP a r t i a l d ep th p a tc h in g s ho uld be p a i d f o r a t t h e c o n t r a c t u n i t p r i c e p e rsquare fo o t. Such payment sh ou ld be f u l l c om pens ation f o r : a l l r e q u i r e dsawing; removing th e a sp ha lt i c concrete patc hing ma teri a1 o r th e spa1 ed,broken o r damaged por t la nd cement concrete; cle an ing th e su rfac e bysandblas ting; fu rn ish ing , .p lac ing , f in is h in g and cu r ing th e concre te pa tch ,and forming a new t ransverse and l on g i tu d i na l j o i n t in c l ud in g a1 1 equipment,ma ter ia ls , labor , and inc id en ta l s necessary t o complete the work.


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CHAPTER 4SUBS EALIGANDSLAMACKI NG OF CONCRETE PAVEMENTS

Subseal'ing i s a nondest ruc t i ve techn ique t h a t f i l l s voids under thepavement w i thou t r a is in g the s lab, d isp laces pockets o f f re e water tha tco nt r ibu te t o pumping and eros ion, and reduces the c rack ing and fa u l t in gt h a t re s u lt s from poor drainag e and nonu niform slab suppo rt. New methods,m at er ial s, and equipment have been developed t o accomplish t h i s work morer a p i d l y and e f f i c i e n t l y .Subsea ling i s done a f t e r s lab rep lacement and f u l l depth patch ing. P a r t ia ldepth patching , should be done a f t e r subsea1 n g has been completed. Someco ntra cto rs suggest a minimum len gt h o f 2 m ile s o f pavement be madeav a i la b le f p r subsea l ing a t one t ime t o accomnodate the va r ious opera t ionsinvo lv ed and t o ach ieve the gre ates t e f f i c ie n cy f rom lab or and equipment.S in ce t h e purpose o f s ub se alin g i s t o s t a b i l i z e t h e s la b by f i l l i n g t h ev oid s w it ho u t l i f t i n g th e s la b, it i s importa nt t o de tec t upward movemento f t he s l ab d u r i ng t h e subsea li ng ope ra ti on. I f l i f t i n g o cc urs , morevo ids w i l l be c reated under the pavement a long w i th h ighe r s t resses i nthe s labs. Therefore, l i f t i n g should be avoided. Some s l ig h t movementmay be unavoidable; sp ec if ic at io ns usual ly a1 ow no more than 0.05 inches.L i f t can be moni to red by beam dev ices (equ ipped w i th se ns i t i ve d ia lgauges) i n conta ct w i t h the pavement and shoulder .Extrus ion o f gro utf r om c racks, t r ansve rse o r shou lde r edge j o i n t s i s ano the r i n d i c a t i onth at vo ids have been f i l l e d .The s t a b i l i t y o f t h e s la b s s ho u ld be t es ted 24 hours a f t e r t he subsea li ngi s completed. I f s t a b i l i t y i s n o t a ch iev ed , a s la b s h o u ld be r e gr o ut e dand retested 24 hours la t er . New ho les shou ld be d r i l l e d f o r eachregrout ing opera t ion . I f a sl ab i s s t i l l u n s ta b le a f t e r tw o a tte mp ts t ounderseal , t hen cons ide ra t i on should be g i ven to rep lac i ng t he p a r t i c u l a rslab.Voids o f t e n e x is t under the shoulder as we1 1 as under the main1 nepavement. Wi th good grout d is t r ib u t i o n , th e grou t should a1 so f i 11 thesevoids. However, be ing narrower and gen era l y somewhat th in ne r, t h e .shoulde r pavement may be more re a d i ly 1 f t e d by th e gr ou t under pressure.Ra isi ng of t h e sh oulder must be avoided; th e measuring device must bec l o s e l y m o n it or ed t o d e t e c t t h e p o i n t where a l l v o id s have been f i l l e dand 1 f t i n g begins so th a t subsea1 n g can be stopped.


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S la b ja ck in gS lab jack ing i s a techn ique t ha t r a is es the concre te pavement s labs t or e s to r e r i d e a b i l i t y . T hat i s , i t s purpose i s t o r e s t o r e t h e o r i g i n a l ( o ran acceptab le) p ro f i le . To be successfu l , s l ab jac ki ng should be done w it hcare. When i t i done co rr ec t l y, sl ab jac kin g can be more economical thanslab replacement and i t s u su a l l y comple ted i n le ss t ime w i th minimumi n te r fe r e n ce w it h t r a f f i c . I f vo id s e x i s t a l o n g w i t h s l a b se t t l e m e n t ,s l a b ja ck i ng can a1 so re s to re t h e s t r u c tu r a l i n te g r i t y o f t h e pavem ent.General ly , an a rrangement o f s t r i n g 1 nes and b locks i s used t o de term ineth e d e s i re d e le v a t i o n (F ig u re 4-1). The s t r i n g 1 n e i s u s u a l l y p o s i ti o ne dabout 1 inch above the desired grade. Gauge blo ck s pl ac ed on the sla bin d i ca te t h e p rog re ss o f l i f t i n g . As th e b lo cks a pp ro ach th e s t r i n g l i n e ,t h e r a t e o f 1i t i n g i s s l owed and pumping i s stopped compl et e dl y when th eb loc ks touc h th e 1i e.S lab ja ck i ng i s us ua l l y no t poss ib le o r a lways p r ac t i c a l when the temperaturei s h igh because the s labs have expanded and the j o i n t s are i n compression.On the o the r hand, when co r re c t i ng a p r o f i l e de f i c ienc y o f g rea te r leng th ,such as ov er an embankment se ttle me nt, th e work wi 11 more 1i e l y bes uc c es s fu l when t h e s l a b i s i n f u l l compression and the jo in ts t i g h t , soth a t an en t i re run o f dep ressed pavement can be 1 f t e d un i fo rm ly . Th ismust be done a small amount a t a t ime, working pr og re ss ive ly toward th elow p o i n t i n t h e d e press io n o r o utwa rd f r om i t as previously d iscussed.

Nail to secure[String line n

Max depth of ' '&~~!hdepression

F igu re 4-1

When a sec t ion o f pavement i s on a v e r t i c a l cu rve , the o f f s e t d is tancesm ust b e ca l cu la te d and a p p l i e d t o t h e h e ig h t o f t h e gauge b lo cks t o p ro p e r l ys e t t h e p r o f i l e o f t h e s ur fa ce .Pumping and jack ing shou ld no rma l ly s t a r t a t the lowest p o i n t i n a dep ressedarea and work outward i n both d i rec t ion s. Greater amounts o f jack inga re necessary a t the low po i n ts du r ing the ja ck ing sequence.


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L i f t i n g shou ld be done i n i nc remen ts o f app rox ima te l y 114 inches w i thf re q u e nt c hanges i n i n j e c t i o n l o c a t i o n s t o keep s l a b s t r e s s es t o aminimum and avo id c rack ing . The ra te o f g rou t i n je c t i o n shou ld be un i fo rmand as s low as po ss ib le ( co ns is te n t w i th economy), us ua l ly 112 cu. fe e tp e r m in u te t o a t o 2 c u. f e e t p e r m i nu te . I n i t i a l pum ping i s u s u a l ly a tt h e slo wer r a t e a nd i s i n c r e a s e d as l i f t i n g p ro gr es s es . As t h e d e s i r e de l e v a t i o n i s app ro ac hed, t h e l i f t i n g r a t e s h o u ld be re du ce d.Regrout i ng i n new d r i 1 1 h o le s an d f u r t h e r s l ab jac k i ng are necessarywhen g rou t i s ex t ruded f rom jo in t s , c racks , o r t he pavemen t edge be fo ret h e t a r g e t e l e v a t i o n i s reached.P ro pe r c o n t r o l o f g r o u t p r es s u re i s t h e s i n g l e mos t i mp o r t an t f a c t o ra f fe c t i n g s l ab jack i ng. Gauged p ressu res f o r s la b j a c k i ng a re u su al l y i nthe range o f 50 t o 250 p s i , w i t h a n o c c a si on a l n eed f o r a d d i t i o n a lp ressu re o f up to 600 p s i t o i n i t i a t e 1 f t i n g . Gauges sh ou ld be c o n t i n u a l l ymon i to red fo r sudden pressure changes. A ra p i d inc re ase cou l d s ig na l as to pp ag e o f f l o w t h a t c o u l d be f o l l o we d b y a b u i l d up o f p r e s s ur e a nd anexcess ive l i f t and c rack ing i f pumping were t o cont inue. A suddenr e d uc t io n i n p re ss ur e c o u ld i n d i c a t e a l o s s o f 1 f t f rom subsurfaceleakage, escap ing gr ou t a t sl ab edges, and so on.Ho le Pat te rnsGrout ho les shou ld be d r i l l e d i n a pa t te rn determined by the SHA i nc on su l t a t i o n w i t h t h e c o n t r a c t o r.H ole p a tt e rn s f o r e f f e c t i v e d i s t r i b u t i o n o f cem ent g ro u t a re n o t e a s i l yde tenn ined i n advance. Same p re l im ina ry te s t i n g i s o f te n necessa ry t ol o c a t e h o l e s i n a way t h a t w i l l e ns u re good g r o u t d i s t r i b u t i o n . When ah o l e p a t t e r n i s s e l ec te d f o r r e p e t i t i o n i n each p anel , he pa t te rn shoul dp ro v id e s u f f i c i e n t ho le s t o p e r m i t g r o u t t o r ea ch a l l v o id s e x i s t i n gbeneath the pavement.Ho le pa t te rns v ary wi th th e concre te pavement des ign , whether jo in te dp l a i n , j o i n t e d w i t h mesh r e in f or c eme n t , o r c o n t i n u o u s ly r e i n f o r c e d . Eachdes ign va r ie s i n panel l eng th , per fo rmance ch a ra c t e r i s t i c s , and d i s t re sspat te rn s , and subsea l ing techn iques shou ld be ad jus ted acco rd ing ly . Groutsubsea1 ng c on t rac ts shou la have enough f l e x i b i l i t y i n th e s p e c i f ic a t i o n st o a1 o w t h e e n g i ne e r t o t a k e a dv an ta ge o f t h e e x p e r t i s e o f s p e c i a l t yc o n t r a c t o r s who a r e u s u a l l y s k i 1 e d i n d e te r m in in g g r o u t h o l e 1ocat ions .F i g u r e 4-2 shows ty p i c a l ho le pa t te r ns used by Sta tes f o r two des igns ;one p la in pavemen t w i th sh o r t panel s and the o the r con t inuous ly re i n fo rce dc o n c r e t e w i t h o u t j o i n t s .


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T

b .Truck Lane $

Typical hole pattern used in subsealing underplain pavement.

- r-*, ~ TPassing Lane - .2:hr. TruckLane - -

c l O ' i ShoulderTypical hole pattern in CRC pavement.

.-' F i gu r e 4 -2The use o f a f i x e d h o l e p a t t e r n ca n r e s u l t i n f o r c i n g g r ou t i n t o a re asunder s labs where subsea1i g i n o t r e q u i r e d . P r ede t e r m i n i ng t v o i dl o c a t i o n s a s d is cu ss ed i n t h e f o l l o w i n g s e c t i o n 'Voi d De te c t io n may be amore e f f i c i e n t and economical approach.The Amer ican Conc re te Pavement Assoc ia t io n (ACPA) i s cu r r e n t l y exper im ent ingw i t h a t e c hn i qu e t h a t i n cl u de s d r i l l i n g t wo h o le s a bo ut 2 f e e t f ro m t h ej o i n t o n t h e " le a ve " s i d e o f t h e s la b. E a r l y r e s u l t s show no d i f f e r e n c e i nd e f l e c t i o n o r i n amount o f g r o u t u se d i n t h e s e tw o l o c a t i o n s . Theseexper iments were on p la in pavements w i t h shor t j o i n t spacings. S ince it i sl i k e l y t h a t m ost v o i d s u n de r a pavement w i t h t h i s d e s ig n a r e l o c a t e d a t o rj u s t ahead o f t h e j o i n t , t h i s v a r i a t i o n i n h o le p a t t e r n i s a l o g i c a l one.It g i v es p ro mi se o f b e i n g more e f f e c t i v e w h i l e r e d u c in g t h e c o s t o f b o t hm a t e r i a l s and l abo r . However, t h i s may no t be ap p l i c ab l e i n a l l cases.There can be pumping a c t io n th a t p roduces vo ids on each s ide o f th e jo in t .H o le p a t t e r n s f o r s l a b j a c k i n g a r e n o r m al ly d i f f e r e n t t h an th o se f o rsubsea1 i n g and t h e y s h o u ld b e d et e rm i ne d i n t h e f i e l d t a k i n g i n t o c o ns id e ra -t i o n t h e f o l o w in g: t h e s i z e o r l e n g t h o f t h e pavement a r ea t o b e r a is e d ;t h e e l e v a t i on d i f f e r en c e ; s ubgr ade and d r a inage c ond i t i ons ; and l o c a t i o n o fj o i n t s and c ra ck s. An exam ple o f a j a c k i n g h o l e p a t t e r n and p r o f i l e a r eshown i n F ig ure 4-3.

Hold Pattern

-- ElevationF i g u r e 4-3


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V o id D e te c t i o nS ev eral meth ods o f v o id d e te c t i o n a re i n use. P erha ps t h e s imp le s t i sa v i s u a l i n s p e c t i o n o f t h e p avement t o l o c a t e a re as o f d i s t r e s s . Thef o l 1o wing v i s u a l o b s e rv a ti o n s c a n i n d i c a te t h e p res en ce o f v o id s.1. D ep re ss io ns o r h o le s a t t h e edge o f t h e s h ou lde r .2. E je c te d ba se o r s u bg ra de ma te r i a l d e p o s i te d a t t h e e dge o f t h e s h ou lde r .3. V e r t i c a l movement a t j o i n t s o r c rac k s.4. F a u l t i n g a t j o i n t s o r cvacks.The two most common methods f o r m easuring s1 ab movement ar e t h e ( 1 lo ad edv e h i c l e a nd (2 ) d e f l e c t i o n d e vi ce s.1. LOADED VEHICLE. Two gauges a re needed t h a t can measure sl a b movementt o 0.001 inches. The Benke lman Beam i s o f t en used f o r t h i s type o fmeasurement. A gauge mount shou ld be p os i t io ne d w i t h one gauger ef er e nc e d t o t h e c o rn e r o f e ach s l a b o n b ot h s i d es o f t h e j o i n tnear the shou lde r edge pe rp end icu la r t o the pavement jo in t . Thegauges should then be zeroed with no 1o a d o n t h e s l a b o n e i t h e rs id e o f t h e j o i n t . A l o a d t r u c k s h o ul d t h en b e moved i n t o p o s i t i o nand s to pp ed w i t h t h e c e n te r o f t h e 18 k i p l o a d e d a x l e a b ou t 1 f o o tb e h in d t h e j o i n t a nd th e o u t s i d e t e s t wheel a b o ut 1 f o o t f r om t h epavement edge. Bot h gauges sh ou ld then be read. The lo ad ed t r u c ks ho ul d t he n be moved a cr os s t h e j o i n t t o a s i m i l a r p o s i t i o n a b o ut

1 f o o t pa s t the jo in t . Bo th gauges shou ld aga in be read . Th is p rocedurei s u sed f o r e ach j o i n t t o b e t es te d.

2. DEFLECTION DEVICES. D e f le c ti o n de vi ce s such as t h e Fa ll in g- W ei gh tD e f lec tometer , D y n af l e c t , Road Ra te r, Heavy Load, and Thumpermeasure the d e f l e c t io n response o f a pavement under a dynamic load .The l o a d in g p l a t e s ho u ld b e p l a c e d a s c l o s e as p o s s ib l e t o t h e s l a bco rne r. Load t r an s f e r shou ld be measured w i th sensors th a t a rep la c e d a d ja c e n t t o t h e j o i n t o r c ra c k o n t h e l o a d e d and u n lo ad ed s i de .D e f l e c t i o n t e s t i n g s h o u ld be p er forme d betwe en t h e h o urs o f m id n ig h t a nd10 a.m. t o a v o i d t h e p r ob le ms cau se d b y te m pe ra tu re d i f f e r e n t i a l ( s l a bc u r l ) and s l a b ex pa ns io n ( j o i n t c l osure) .D r i l l i n gH ol es d r i l e d t h r o u gh t h e s l a b s ho ul d b e v e r t i c a l a nd c a r e f u l l y madeso t h a t t h e y a r e c i r c u l a r and t h e p l u g s c an f i t t i g h t l y t o c o mp le te lys top g ro u t ex t ru s io n when ad jacen t a reas a re g rou ted . Grou t ho lesa r e g e n e r a l l y 1-1/4 i n ch e s t o 2 i n c h e s i n d ia me te r . T he re doe s n o tappear t o be an advantage o r 1 f t i n g s u p e r i o r i t y a t t r i b u t a b l e t ol a r g e r h o l e s i ze s . Fewer b re a k o u ts a re p ro du ce d a t t h e b o tt o m o f t h es l a b w i t h s m a ll er -d ia m et er d r i l l s . H o le di a mete rs o f 1 -1 /4 i n c h e s t o1-1/2 inc hes ar e recommended. When sp ec if y i ng t he ho le diam eter, th eSHA shou ld use a range (such as the above) ra th er than one sp ec i f ics i z e i n or d er t o b e s t u t i l i z e t h e c o n t r a c t o r ' s e x i s t i n g e quipment.O th erwi se , a c o n t ra c to r ( o r s u b c o n t ra cto r ) w i l l b e f o r c e d t o pu rc ha senew d r i l l s, p ac ke rs , e tc ., w hi ch w i l l b e r e f l e c t e d i n t h e c o s t o f t h ep r o j e c t .


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Grout ho les can be made w i t h any ty pe o f d r i l l t ha t w i l l p roduce a c l eanho le w i th no sur face s pa l l i ng o r b reakou ts on the unders ide o f the s lab .Mos t d r i 11 n g i s done w i t h p ne um atic al y o pe ra te d r o t a r y p e rc us si on d r i l l sw i t h c a r b i d e t i p s . T y p i c a ll y , t h i s t y p e o f equipm ent c an d r i l l a h o le i nl e s s t h an 1 minute.H igh speed d r i l l s mounted on a l a r g e r u b b e r - t i r e t r a c t o r a r e f r e q u e n t l yused. The d r i l l frame i s sometimes we igh ted t o inc rease d r i l l p ressure.The quest ion has been ra ise d whether d r i l l n g a t h ig h speed under addedp res su r e w i l l b reak t he c onc re t e a t t h e bo tt om o f t he s lab. Studies by theNew York Department o f Tran spo rtat io n found th a t t he s iz e and weight o fro ck d r i l l s were v ery impo r tant fa c t or s i n th e amount o f damage susta inedby th e pavement. U n it s w it h a hammer weight o f 45 pounds were sa t i sf ac to ry ;d r i l l s o f g r ea t e r w e igh t and g r ea te r downward p r ess u re r es u l t ed i n cone -breakou t damage t o th e unde rside of th e sl ab and subsequent r a d ia l cracking.There was a l so a g rea te r f requency o f t ransverse c racks th rough th e d r i l lholes when the heavier machines were used.Some cau t ion shou ld be exerc ised i n de te rmin ing the optimum d r i l l s i zeand we igh t and p roper d r i l l i n g p rocedures i n o rder t o c o r re la te maximumd r i l l n g e f f ic ie n c y and economy wi th minimum damage t o pavement.D ep th o f t he g r ou t ho les w i l l v a ry w i t h unde r l y i ng m a t e r i a l s and c ons tr uc ti on .I n g en era l , d r i 11 n g sho uld be through b ot h th e pavement and th e base.Experience has shown that voids are sometimes found under a stabi l zed base.The bo ttom o f the g rou t i n je c t i o n p ipe shou ld no t be any lower than thebo tt om o f t he c onc r e te s l ab t o a1 l ow g r ou t t o f i l l a l l v o id s b elo w t h econcrete s lab as we1 1 as those th a t may e x i s t below t h e base (Fig ure 4-4).Where g rou t f l o w i s d i f f i c u l t t o ge t s t a r ted , w as hing o r b l ow ing ou t as m all c a v i t y a t t h e b o tt om o f t h e g r o u t h o l e w i l l f u r n i s h a s u pp ly o f g r o u tt o h e lp i n i t i a t e i t s f l o w t o s u rro un din g voids.For sa fe ty and economy, d r i l l i n g shou ld be done jus t p r i o r t o p ressuregrou t ing so tha t bo th crews can be p ro tec ted by th e same t r a f f i c con t ro ldevic es. For th e same reasons, i t i s a ls o wise t o c o nf in e th e d r i l l i n gand g r o u t i n g o pe r at io n s t o a s i n g l e t r a f f i c l an e a t o ne tim e.

Ik Grout injection pipePavementSubbase

-possible void locations

Figure 4-4


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Grout Mix ing, Pumping, D is t r ib u t i o nModern gro ut ing con trac tors use h i gh ly mobi le , se l f -con ta ined un i ts t oc ar ry a1 1 equipment and m ate ri a1 components f o r t h e subsea1i g operat on.Dry m ate ria ls ar e norm ally packaged i n unif orm -vol ume bags o r measured byweight i f i n bulk.M ix ing wa ter i s metered f rom a supply t ruck . Dry ma te r ia ls a re no rma l lyp ro po r ti o n ed on a volu m e tr i c b a s is f o r b e t t e r co n t ro l . The mixer should becapab le o f thorough , homogeneous mix ing , and sh ould be t h e p o s i t i v e s heartype f o r tho rough m ix ing. One special ty contractor using cement-pozzol angrout recomnends use o f a h igh-speed co l lo id a l mixer opera t ion i n the rangeo f 800 t o 2 000 r ev 01 u t i o n s p er m i nu te i n o rd e r t o a t t a i n a t r u e c o l l o i d a lm ix t h a t w i l l keep t h e s o l i d s i n su sp en sio n and r e s i s t d i l u t i o n by f r e ewater be ing displa ced fro m under t h i s pavement.The pump shou ld be capab le o f a pp ly in g 50- to' 250-pound psi p ressu re a t theo u t le t end o f th e disc harg e pipe. The pump should be o f t h e p o s i t i v edisplacement type and should be equipped with horizontal mixing paddles.The a g i ta t i on f rom such mix ing main ta ins a un i fo rm consistenc y and ass ist si n feed ing the g rou t t o the pumping un i t .A f t e r th e ho les a re d r i l l e d i n the pavement, pumping p roceeds by lower ingth e g ro u t i n j e c t i o n p ip e i n to su cce ssi ve ho le s. An expanding rubber packeri s used t o sea l th e open space between p ip e and d r i l l ho le . The d ischargeend o f the p ipe shou ld not extend be low the bot tom o f th e pavement so th a tany void s between pavement and base w i l l be f i l l e d w i t h g ro ut. The i n j e c t i o np i pe c a rr y i n g th e g r ou t t o t h e d r i l l h o le s ho uld be equ ipped w i th a re tu rnl i n e t o the pump hopper so tha t the g rou t m ix tu re can be con t inuo us lyc i rc u l a t ed d ur in g per iods when no grout i s be ing p laced.F o r p ro p er d i s t r i b u t i o n o f g rou t, t h e i n j e c t i o n p re ssu re sh ou ld be i nth e range o f 50 t o 250 ps i. The lower pressures should be used where vo idf i l l i n g on ly i s be ing done. Greater pressures may be needed f o r s lab jacking,b u t pr es su re s t h a t a r e t o o h ig h c an c o n t r i b u t e t o r a d i a l c r a c k in g a t d r i l lholes.Grout quanti t ies can be est imated and checked by the hole and by thej o i n t . T y p i c a l q u a n t i ti e s r u n f ro m 2 t o 8 c u bi c f e e t o f d r y m a t e r ia l s p erj o i n t a n d / o r 0.6 t o 1.0 cub ic fe e t pe r ho le . The h ighe r qu an t i t ies a ref o r pavements w i th severe pumping and more voids.Grout Mix RequirementsM a te r i a l s f o r p ressure g ro u t i n g sh ou ld y i e l d a g ro u t m ix t h a t r em ainsinso lub le , incompressib le , and nonerod ib le a f t e r i t i s pumped i n p lace andhas hardened. The s lu r r y shou ld be f lowab le w i t h low in te rn a l f r i c t i o n soi t can move throug h sm all openings and f o l l o w water channels t o f i l le x is t i n g voids. At th e same t ime, th e grout mix shou ld have s u f f ic ie n tbody t o d isp la ce f r e e water f rom under the s lab and shou ld deve lop adequatestr en gth and d urabi 1i y .


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Pozzo lan ic m a t e r ia ls have re ce n t ly come i n t o more genera l u se i n p r e s s ur egr ou t i ng mixes because they produce grea ter s t re ng th and improved work-a b i 1i y . The types o f pozzo l ans i c l ude t ho s e o c c u r r i n g n a t u ra l y( v o l c a n i c ash, d ia to ma ce ou s e a r th ) and t h o s e a r t i f i c a l y prod uc ed i n t h ec om b us ti on o f c o a l ( f l y as h). These mate r i a1 s a re c la s s i f ie d underAmerican Soc ie t y f o r Test ing and Ma te r i a l s (ASTM) Des ign at ion : C618. Thep r e do m i n a nt l y s p h e r i c a l shape o f t h e p o z zo la n p a r t i c l e s a nd t h e i r f i ne n e s sa l l o w t h e g r o u t t o p e n e t r a t e more s t e a d i l y i n t o t h e s h a l l ow v o i ds u n de rthe pavement. P oz zo la ns i n c om b in at io n w i t h t h e f r e e l i m e r e s u l t i n g f r o mcement hy d r a t io n p ro v ide ad d i t io na l cemen ta t ion , enhancing th e poss ib i 1i y .o f g r e a t e r s t a b i l i t y i n t h e ce me nt-p oz zo la n g ro u t. A t y p i c a l m i x d e s i g ni s :1 p a r t cement, Type I r Type I 13 p a r t s po zzo lan, n a t u r a l o r a r t i f i c i a lWater f o r pr op er f l u i d i t y

A one t o t h re e c e men t-po zz olan m ix tu re s h o u ld d ev e lo p s u f f i c i e n t s t r e n g tht o p r e cl u de g r o u t e r o s i o n t h a t c o u l d r e s u l t f ro m h y d r a u l i c a c t i o n u nd er ah e a v i l y t r a f f i c k e d pavement. Cem ent-f ly ash gro ut s have been shown t ol o s e f l u i d i t y w i t h i n a p pr ox im a t el y 20 t o 30 m i nu te s a f t e r p lacem ent.S inc e t h e g ro u t i s n o rm a l l y c o n f i n e d and c a nn o t be d i s p la c e d 1a t e r a l y ,i t i s ca p ab le o f s u p p or t in g t r a f f i c l o a ds l o n g b e f o r e t h e s e t t i m e s shownb y a cc ep te d t e s t methods. R e s u l t s o f l a b o ra to r y t e s t s a nd t h e s u c c e s s fu lr e t u r n o f t r e a t e d s la b s t o f u l l t r a f f i c i mm ed ia te ly f o l l o w in g g ro ut in ghave g i v e n r i s e t o recom mendation t h a t v e h i c u l a r t r a f f i c be p e r m i t t e d onnew ly g rou ted s labs 1 h o u r a f t e r p r e ss u r e g r o u t i n g i s c om ple te d.Use o f admix tu res w i th cem en t - f l y ash g rou t m ixes s hou ld be done w i t hca re . Labora to ry te s ts have shown a va r i e t y o f rea c t io ns between pozzolansa d mixtures . Each a d m ix ture s h o u ld b e t e s te d a nd e v a lu a te d p r i o r t o f i n a lapproval. These adm ixtu res may be wa te r red uce rs, f 1u i d i i r s , expandinga ge nts t o o f f s e t s h ri n ka g e o r c a l ci u m c hl o r id e .I f th e amb ient tempera tu re i s be low 50F, an acce le ra to r cou ld be usedsu bje c t t o approva l by th e SHA. When ca lc i um c h lo r i d e i s added, its h o u ld be t h o ro u g h l y p re m ix ed w i t h t h e wa ter b e fo re t h e d r y i n g r e d i e n t sa r e added. When d r y in g r ed ie n t s a re added t o a m ixed ba tch t o th i ck eni t s co n si st e nc y , t h e y must be i n t h e s p e c i f i e d r a t i o .Subsea1 n g o r s la b ja ck in g sho u ld no t be pe r fo rmed when th e amb ient a i rtemperature i s 35OF o r below, o r when th e subgrade i s f rozen.


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Consistency TesterThe req ui r ed water content i s determined by a f lo w cone. A f l o w cone o fthe typ e and dimensions developed by th e Corps o f Engineers (Fig ure 4-5)i s com nonly used t o p e r i od i ca l l y check t h e cons i s tency o f t he g rout . Thet im e requ i red t o em pty the cone m easures t he f l o w a b i l i t y o f t h e g rou tm ixtu re . Th i s f l ow i n seconds ( t im e o f e f f l u x ) i s de te rm ined by C orps o fEng inee rs Tes t Method No. CRD-C611-80. Flow cone req uir em en ts and i n s t r u c -t i o n s a r e r e a d i l y a v a i l able.Consistency should be checked by the f low cone method twice each day.The f l o w t ime g en era l ly var ies between 10 and 16 seconds f o r sub sea l ingdepending on t he t yp e o f m a te r i a l i n t he g rou t . A t t he beg inn ing o f as l ab jack ing ope ra t i on , t he f l ow t im e o f t he g rou t m i x tu re should bebetween 16 and 25 seconds t o a l lo w a more f l u i d m ix ture t o l i f t th esla b un ifor mly . However, i f t h i s g ro ut c on sis te nc y f a i l s t o l i f t th es lab , t he g rou t m i x tu re should be g radua l l y changed t o a l esse r f l o w( s t i f f e r m ix ) i n or d e r t o i n c re a s e t h e p re s su re and l i f t the s lab .

,+-3IjSR diam point gage.n

t0

tQ, Cast aluminum

As req u i red by t he SHA, t he con t rac to r should subm it m i l l ce r t i f i ca t i on sf o r the cement, phy sical , and chemical ana l ys i s f o r t he pozzo lans, g ra i ns t ru c tu r e ana l ys i s f o r t h e 1 m es tone dus t, and independent 1abora toryt e s t i n g o f t h e g r ou t s l u rr y . T es t r e s u l t s o f t h e s l u r r y s h ou ld i n c lu d e1 day, 3 day, and 7 day stre ng ths , f lo w cone t imes, shrinka ge and expansionobserved, t i m e o f i n i t i a l se t , and w a te r r e te n t i v i t y .


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Plugging and Clean UpA ft e r g ro ut ing has been completed a t each hole, th e packer should beremoved and the hole plugged imnediately with a tapered wooden plug. Thetape red p l ugs, however, ar e o nl y temporary. When suf f ic ient t ime hase la ps ed t o p e r m it t h e g ro u t t o s e t s u f f i c i e n t l y s o t h a t back p r e ss u re w i l ln o t f o r c e it fro m th e h ole, t h e temporary wooden pl ug s shou ld be removed.Each hole should be permanently sealed f 1ush wi th the pavement sur face wi tha fas t s e t t in g sand/cement o r polymer concrete mix approved by th e engineer.Grout and cement s lurry on the pavement or shoulder sur face should bebroomed and washed o f f t o avo id u ns ig ht l y d i sc o l or a t io n and t o remove theg ro u t o r s l u r r y b e fo re it bonds t o the sur face.A1 1owable Curing TimeS p e c i f i c a t i o n s f o r t h e t i m e a1 low ed t o p e r m i t t r a f f i c on g r ou t ed s l a b s v ar yconsiderably. The cure t i m e ranges from 30 minutes t o 3 hours depending onthe m ix compos i t ion and the degree o f conf inement o f the grout .Method o f PaymentThe f o l l o w i n g a re th re e comnon methods o f payment. An SHA sho uld usew ha te ve r method b es t s u i t s i t s p a r t i c u l a r p r o j e c t .1. Pay qu an t i t y per te s t lo ca t io n (i.e ., j o i n t o r c rack) . Payment perl o c a t i o n s h o u ld i n c l u d e b o t h t h e i n i t i a l t e s t i n g and any s ubse que ntte s t in g (e.g., the con t rac tor shou ld be pa id on ly once f o r th edef lec t ion tes t ing no mat ter how many t imes re tes ted) .2. Pay quan t i t y pe r ho le d r i l l ed . Payment i n c l udes d r i l l ng , p lugging ,and hole seali g.3. Un i t p r i ce by vo l ume o r we ight o f d ry mater i a1 (s ) . Should inc ludemobi 1 za t i o n , water, ad dit ive s, equipment, labo r, and a1 1 oth erma te r ia ls necessary t o m ix and pump the grout .SumnaryWhile i t may appear that subseal ing and s labjacking are s imple processeso f d r i l l i n g and pumping, the procedures descr ibed re qu i re cons iderab leexp er t i se t o succ ess fu l l y co r re c t un sa t i s fa c to ry con d i t i ons w i thou t damaget o th e pavement. I f s lab jack ing i s no t done un i fo rm ly , i t very of ten causescracking.The techn iques app l i ed i n subsea li ng and s l a b jack ing a re no t p re c i s e l ydefin ed; th e process i s as much an a r t as a science. The success o f ap r o j e c t i s l a r g e l y d ep end ent o n t h e s k i 1 1 and e x p e r t i s e o f t h e c o n t r a c t o rand th e crew do ing th e grout in je c t io n . Because it i s a h i g h l y s p e c ia l iz e dopera t i on req u i r i ng t r a i ne d personnel and equ ipment designed f o r a pa r t i c u l a rpurpose, t h i s t y p e o f w ork i s p a r t i c u l a r l y s u i t e d t o s p e c i a l t y c o n tr a ct o rsexperienced i n success f u l y per form ing these re s t or a t o n procedures .


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CHAPTER 5DIAMOND GRINDING OF JOINTED CONCRETE PAVEMENTS

I n t r o d u c t i o nDiamond g r i n d i n g i s used t o r e s t o r e p r o fi e and c ross -sec t i on; e l m i na terough r id e due t o fa u l t i n g , s lab warp ing, and wheel ru ts ; and t o res t o r ea g ood s k i d r e s i s t a n t t e x t u r e t o t h e pavem ent s u rf ac e.The cos t o f g r in d in g i s p r im a r i l y dependent upon th e amount o f m a te r ia lt o be removed and the hardness o f t h e aggregate . On a t y p i c a l p r o j e c t t h ec o st o f g r i n d i n g f o r s o f t a gg re ga te i s i n t h e r an ge o f $2 t o $3 pe r sq.yd., f o r medium ha rd aggregate, $3 t o $5 per sq. yd., and f o r har d aggreg ate$5 t o $8 per sq. yd. (1981). Costs are a1 so a f fe c t ed by th e s iz e o f th ep r o j e c t , t r a f f i c c o n t r o l p ro ce du re s, w ork h ou rs , s l u r r y d i s p o s a l , nd thedegree o f smoothness sp ec i f ie d.The c o s t e f f e c t i v e n e s s o f d iam ond g r i n d i n g i s s i g n i f i c a n t l y c ha ng in gw it h c ur re nt equipment and bla de developments. These developments i cl udelarger and more powerful equipment ( 6 f o o t c u t t i n g w id th ), d i f f e r e n t ty p eso f segmenta l c u t t i n g heads and b lade development t o i nc rease th e 1 f e o fblades.Blade SpacingThe s in g le mos t impo r tan t fa c t o r a f fe c t in g th e pavement r i de ab i 1i y andte x t u r e i s the spacing o f the d iamond saw b lades. B lade spac ing i n thec u t t i n g h ead can be v a ri e d t o im prove t h e l i f e and f r i c t i o n f a c t o r o f t h et e x t u r e .Ba s ica l l y , b lade spac ing i s de te rm ined by the ha rdness o f th e aggrega tei n t he conc re te pavement. The f o l l o w i n g i s ge ne ra l c r i t e r i a f o r b la d es pa ci ng f o r s o f t a g gr eg a te ( s u s c e p t i b l e t o p o l s h i ng) and hard aggregate.For sof t aggregate , th e spac ing shou ld be wider t o prov ide more " lan da re a " b etw ee n t h e b l ad e s f o r a l o n g e r l a s t i n g t e x t u r e . The g r i n d i n g c h i pbetween th e blade s, sho uld be 0.080 in c h minimum and have an averageth ickn ess o f 0.100 inc h (F ig ure 5-1) .


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Grinding ProceduresThe p lans should design ate th e areas o f pavement t o be ground. Water i sused t o cool t he cu t t i n g head o f t he g r i nd ing m achine. The s lu r ryproduced fro m g ri n d in g can be removed by one o f two methods. It can bevacuumed f rom the sur face and pumped i n t o a tank t ru ck w i th b a f f le s whichi s c o st ly , o r i t can be depos i ted d i r e c t l y on the grass shou lders wh ich hasno t p roven t o be de t r im en ta l. A su i t a b le d isposa l s i t e shou ld be prov idedwhen pumping adja cen t t o t he roadway i s not possib le.The gr ind ing l im i ts shou ld be c lear ly shown on the p lans and shou ldi nc l ude the t r an s i t i o n o r s top 1 nes a t b r i dges and ramps. The maximumove r1 ap between passes sh ou ld be 2 inches.G r in d in g p ro d uc ti on i s t y p i c a l l y 50 machine hours per lan e mile , butt h i s w i l l vary cons iderab ly w i th aggregate hardness and the roughness o fthe pavement. The d i r e c t i on o f g r ind ing shou ld be the opt io n o f thecon t rac to r i n o rde r t o m in im i ze cons t ruc t i on cos ts .R ideabi 1i yThere a re s eve ral methods used t o measure th e roughness o f pavements.These in c lude the Ca l i f o r n i a o r Ra inhar t P ro f i ograph, the Mays R ide Meter,PCA o r W isconsin Road Meter, GM Prof i lom eter , and the BPR Roughometer.I t has been demonstrated on numerous projects that diamond grinding canproduce a smoother pavement su rfa ce than new co ns tru cti on . T hi s should bere f le c t ed i n th e SHA's r i d e a b i l i t y sp ec i f i ca t ion . As an example , SHA'su s i n g a p r o f i l o g r a p h s p e c i f y a p r o f i l e i n d e x o f 1 2 i n c h e s p e r m i l e f o rcons t ruc t ion and 7 inches per m i l e fo r d iamond gr inding. The above i s on lyan example and t h e engineer sho uld a1 ways co ns ide r c os t e ffe ct iv en es s whens p e c i f y i n g th e p r o f i l e ind ex.Where ru ts are be ing e l im ina ted by gr ind ing, a s t r in g 1 ne can be usedt o check t he t r ansve rse p ro f i l e .S p e c i f i c a t i o n s s ho u ld p e r m i t f e a t h e r i n g o v e r p o r t i ons o f t h e su r f acewhen ste el i s found near the sur face.When an is ol at ed low spot i s encountered, the sp e ci f i ca t i o n should notr e q u i r e g r i n d i n g t h e l o w sp o t i f i t r e q ui re s l o w e ri n g t h e o v e r a l l p r o f i l eof the pavement. The cos t e f f ec t i veness o f t he e x t ra expend i t u re i sh igh ly ques t ionab le .Transverse j o in ts and random cracks shou ld be inspec ted t o ins ure th a tadjacen t surfaces are i n the same plane. M isa lignment o f th e p lanes o fthe surfaces should not exceed 1/16 inch. I n any 3 f o o t b y 1 0 0 f o o t t e s ta r e a a t l e a s t 95 percent o f the sur face shou ld be tex tured.


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Concurrent WorkS lab s ta b i l i z a t i o n by subseal ing , fu l l - de pt h replacement and spa1 1repa i r shou ld be comple ted before gr ind ing. Exper ience ind ica tes , th a tground pavements wi th ou t subsea1 n g (when needed) can s ig n i f ic a n t l yre du ce t h e l i f e o f t h e r e s t o r e d sm ooth p r o f i l e . R esea l i ng j o i n t s shou ldf o l l o w t h e g r i n d i n g o p e r a t i o n t o i n s u r e p r op e r s e a la n t d ep th .Method o f PaymentGr ind ing can be pa id f o r by th e square yard . The con t rac t p r i c e persquare ya rd f o r gr in di ng con crete pavement should be f u l l com pensationf o r f ur ni sh in g a l l labo r , ma ter ia ls , and equipment i n accordance w i t h th epres cr ibed s ect ion s o f th e SHA's sp ec i f i ca t io ns and as shown on th eplans.


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CHAPTER 6BONDED PCC RESURFACING OVER EX1STING CONCRETE PAVEMENTS

I n t r o d u c t i o nTh is chap te r desc r ibes th e concep t o f ov er l ay i ng ex is t i n g r i g i d pavementwi th bonded por t1and cem ent c o n c r et e t o i m pr ov e t h e s t r u c t u r a l i n t e g r i t y ,improve the r ide , i nc rease the ca r ry i ng capac i t y , improve the sk id res is tance ,and e xte nd t h e u s e f u l l i f e o f t h e o r i g i n a l s t r u c tu r e . C o n st ru c ti ontechniques w i l l be d iscussed as we1 1 as those i tems which re qu i re p a r t ic u la ra t t e n t i o n i n o r d e r t o make an o v e r la y p r o j e c t s u cc e ss fu l. Topics discussedwi 11 be sur face p rep arat ion, bonding grou t appl ic at io n, placement, o i n t i n g ,f i n i s h in g , tex tu r i ng , cu r ing and te s t in g requ irements , and bas is o f payment.Bonded PCC can be con sider ed op era tio na l o r exp erim enta l depending on th eexperience i n a give n State. This tech nique has proven successful on manyp r o j e c t s . L i k e a1 1 o t h e r r eh a bi 1 t a t i on te ch niq ue s, bonded PCC o v e rl aysre qu i r e good qua1i y c o n tr o l.Surface Prep ara t ion The e x i s t in g concre te sur face must be c leaned o f a1 1d e t e r i o r a t e d o r c o nt am in at ed m a t e r i a l i n c l u d i n g ti e rub be r, d i r t , o i ld r i pp i ngs, n d o l d 1ane 1i e ma rki ngs. The development o f h i gh product i n,s e l - p r o p e l 1ed co ld-mi 11i g equipment (CMI Roto-M i 11,Gal i o n Road P l aner,Barber-Green Dynapl ane, e tc.) and improvements i n a i r , wate r, sand, andsho tb la st in g techniques (Gomaco) have re su l te d i n h i gh product ion c lea nin gprocesses . A genera l desc r ip t ion o f su r f ace p re pa ra ti on equipment f 01 1ows.1. M i l l i n g / S c a r i f y i n g E q u i p m e n t - Con sists o f a power-operated, mechanicals c a r i f i e r c a pa ble o f u n i fo r m l y s c a r i f y i n g o r rem oving t h e o l d s u rf ac ei n a s a t i s f a c t o r y m anner t o t h e d e pt hs and c r o ss s e c t i o n r e q u ir e d .Ot

const handbook pcc pavement rehabilitation 014728

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