Cracking and Seating of Concrete Pavement on 1-74

TRANSPORTATION RESEARCH RECORD 1268 25

Cracking and Seating of Concrete Pavement on 1-74

MAGDY EL-SHEIKH, JosEPH J. SuDoL, AND REBECCA S. McDANIEL

Crncki11g and seating is hccoming a popular technique for reducing reflective cracks in a phalt overlays over dct riorated concrete pilven1cn1s. lndi;rna initial cl an c .~perirnental project on J-74 in the ·pring of 1984 10 study rhc potential o r cracking and ~ea ting. Th1.: J erformancc of 1he a plml1 overlay is describ cl 5 years after irnpl mcn1i 11g 1hc technique. racking and sealing prevented at least 75 percent >f the reflective crach 1hai normally ccu r at yei1 rs of ervice life. Adding fibe rs to the a pha lt overlay mixture over cracked and s :ued secrions re ·u11.ecl in further pr vemion of rc llective era k .. maint ai ned the tructural trengths bmh o the pavement and of it up1 o rt. and may ha e reduced the ror· matio11 of bl()wups. · urth rmorc. the number o blowu ps pe r mile in the cracked and . eated . ccti 11s was recl ucecl b 50 percent over the control ectlons, which were not cracked and seated .

Many of the nation 's highways are constructed with concrete pavements. These concrete pavements deteriorate with age, and resurfacing becomes necessary to restore rideability , structural strength, and skid resistance. Asphalt overlays have been a popular and practical choice for most resurfacing . However, experience has shown that an asphalt overlay usually deve lops a cracking pa tlern that reflects the one existing in the old concrete . Such cracks are referred to as "reflective cracks."

Reflective cracks are mainly initiated and propagated by thermally induced and traffic-induced stresses (1). Thermal contraction of the underlying concrete causes tensile strains in the a phalt overlay; cracks form when ver the tensile capacity is exceeded. The diffe rential enica l deflectio n of the concrete pavement at cracks and joints under traffic loads also help propagate refl ective cracks.

Preventing, or at least reducing , reflective cracks he lps to prolong the service life of an asphalt overlay and reduces maintenance costs. Over the years, many techniques have been deve loped to try to control reflective cracks . One technique currently used by many states involves cracking and seating the old concrete pavement before overlaying it with asphalt. This technique has potential for reducing reflective cracks. The process of cracking and seating consists of breaking the old concrete slabs into small pieces and pressing these pieces down by rolling with heavy rollers.

The effectiveness of the cracking results from having smaller concrete slabs that undergo reduced thermal length changes and th erefore induce smaller thermal strains in the asphalt overlay. Seating the cracked pieces also reduces the differential vertical defl ections at cracks.

As a supplementary treatment to further reduce reflective cracks, part of this experiment contains polypropylene fibers

Indiana Department of Transportation, Division of Research , 1205 Montgomery Street, P.O. Box 2279, West Lafayette, Ind . 47906.

in the asphalt overlay. This addition of fibers to th e overlay is intended to increase its tensile strength.

A description of roadway conditions following 5 years of service follows. Past experience indicates that deve lopment of reflective cracking in overlays, at this point in the pavement's life , has sufficiently stabilized so that the data obtained can be used to evaluate the merit of most crack reduction techniques . However , the previous five winters in Indiana were not severe and reflection cracking in general was slow to develop (2-4).

The original condition of the concrete pavement in this study was quite good between joints and cracks, but e lsewhere it was in an advanced stage of deterioration because of D cracking. Pavement drainage did not appear to be a general problem, but localized areas with poor drainage did exist. Drainage was upgraded during construction of this contract and can be considered at this time to be good .

OBJECTIVES

The objectives of this experimental study are as follows:

1. Toe aluate th e effectiveness of the cracking and seating technique in reducing reflective cracks,

2. To determine the optimum asphalt overlay thickness for best crack control and pavement strength,

3. To study the effect of adding fibers to the asphalt overlay on reflective crack intensity and any resulting increase in strength , and

4. To investigate any negative aspects associated with these rehabilitation techniques.

SCOPE

The India na DOT initiated this experimental cracking and seating tudy in the spring of 1984. The project is located on I-74 and runs from SR-39 to 2.0 mi west of the MontgomeryBoone county li ne. It involves 12 .2 mi of centerline concrete pavement originally constructed in 1974. The traffic volume is over 10,000 vehicles per day with about 30 percent trucks.

WORK PLAN

Eight different concrete pavement rehabilitation treatments were used in this study. The details of each treatment , as well as the layout of different sections rehabilitated , are shown in Table 1 and Figure 1, respectively. The two basic rehabilitation techniques used were

1. asphalt undersea ling with an asphalt overlay, and 2. cracking and seating the concrete slabs with an asphalt

overlay .

26

TABLE 1 REHABILITATION TREATMENTS

Treatment

A

Al

A2

B

Bl

B2

c

D

Description

asphalt underseal with asphalt overlay

as A with fiber reinfa_rced asphalt base layers

as A with fiber reinforced asphalt base and binder layers

cracked and seated with asphalt overlay

as B with fiber reinforced base layer

as B with fiber reinforced asphalt base and binder layers



An asphalt overlay thickness of 4.r in. was u ed for the control sections. These control sections were also undersealed with asphalt. Overlay thicknesses of 5.0, 6.5, and 8.5 in. were used on the cracked and ea ted sections. Fibers were added both to the base and binder mixtures on one control section and on one cracked and seated section. Fibers were also added to the base layer only for one control and one cracked and seated section.

To determine the performance of these treatments for various sections, the following actions were conducted:

1. Transverse reflective cracks were counted by visual survey each year for each section over a 5-year period (1985 to 1989).

2. Deflections were measured using the Dynaflect each year for all sections.

3. Blowups were counted for each ection by visual survey. 4. R uts in the wheel path were m_ea ·ured for all ections

using a 4.0-ft straightedge.

RESULTS

Reflective Cracks

Reflective crack intensities for different treatments over the 5-year period were plotted in Figure 2. The reflective crack

TRANSPORTA TJON RESEARCH RECORD 1268

Overlay Contents overlay (lb./sq.yd.) Thickness Surface Binder Base

(in.)

4.25 70 150 2::io

4.25 70 150 250

4.25 70 150 250

5.00 70 150 330

5.00 70 150 330

5.00 70 150 330

6.50 70 150 510

8.50 70 150 700

development on the control section. was high in the beginning and increa ed at a fast rate. Mo -1 reflected cracks ·h ' con-iderablc c mpounding and meandering. pr uably be ause of

the D cracking in the o ld pavement. Adding fibers to the mixtmes in th control ·ection did n l h Ip lo c ntrol the occurrenc f high crack rcOcction in the fin 2 year; however. rack development progre ·se l more low I afterwards. R fl ecti ve crack devel pmenr on the cracked and seated sections was low in the fir ·t 3 years and th reafter increased ·J ' ly . racking and seating redu d r · flccliv crack by nt least 75 percent over tho. ccurring in the untracked control sections. A further reduction of reflective cracking on the cracked and seated sections was obtained by the addition of fiber to the asphalt mixture. It was ob ·erved that increasing a phalt overlay thicknes on the cracked ancl se·1ted sectio n. from 5.0 t 6.5 in. reduced the number of reflection crack: by abo ut 25 percent. A ex1 ected , erlaying with . - in . r asphalt reduced reflectiv crack even more. Also. a<.!ding the fibers to the a ·phalt mixture delayed the n ·et of reflective cracks and reduced their rate of development.

Road Structural Strength

Deflections for all the different sections were collected annually u~ng the Dynaflect. In Figure 3 to 6, the maximum and minimum Dynaflect reading taken in 1984 and 1988 (or 19 9

El-Sheikh et al.

EB WB Station Treatment

417 417

A A

474 474

D D

576 576

A A

686 686 c c

716 716

B B

768 768

A A

925 925 B B

956 956 c c

988 988

1018 D D

B Bl

1052 B2 A2

1077 A Al

KEY:

Underseal , 4t in. Overlay Crack & Seat, 5 in. Overlay Crack & Seat, 6~ in. Overlay Crack & Seat, 8~ in. Overlay

FIGURE 1 Treatment locations.

were plotted for all different treatments. The deflection data were adjusted to the standard temperature of 70°F according to Majidzadeh and Kumar (5) . Maximum deflections indicate the relative strength of the pavement section, whereas minimum deflections give an indication of the relative strength of the pavement support. Satisfactory maximum deflection for overlaid concrete pavement is 0.50 mils, whereas the unsatisfactory value starts at 0. 70 mils. Satisfactory minimum deflection is under 0.30 mils . Anything over 0.30 mils represents poor pavement support (5) .

The 4.25-in. overlay on the uncracked control section is similar in strength to the 8.50-in. overlay on the cracked and seated section. Both of these sections have undergone less than 15 percent strength decrease in 5 years. However, the cracked and seated sections with 5.0- and 6.5-in. overlays have

27

Station

North -4

1: Fiber Reinforced Base 2: Fiber Reinforced Base

and Binder

deteriorated in strength as much as 50 percent. As can be seen in Figures 4 and 6, the addition of fibers to the overlay mix improved or at least maintained the total pavement strength and the pavement support strength with time. The addition of fibers to either the base (fb) or binder, or both (fbb), improved or maintained the pavement strength similar to uncracked pavement with 4.25 in. overlay or to the cracked and seated pavement with 8.50-in. overlay.

Ruis and Blowups

Ruts were measured in the wheel path on all pavement sections using a 4.0-ft straightedge in 1989. Ruts for all fiber mix overlay sections were approximately V16 in. and for all other

28 TRANSPORTATION RESEARCH RECORD 1268

12 :>..

1985 +J •.-l -l/J 10 ~ QI +J .-.

1986 ~ •.-l +J

11-1 l/J

8 ...: . u C"

"' l/J "' uo 1987 0 QI 0 :> ..... ·.-l-+J . u +J QI 11-1 .... ~

1988 11-1 QI

"' 4 ~

1989

A c 81 A2 8 D 82 A1

treatment methods

FIGURE 2 Development of reflective cracks with time for several treatments.

sections they were about Ys in. The slight difference in rutting is attributed to the fiber reinforcement of the overlay mix, as expected. In both cases, however, rut depths are lower than one would expect on bituminous pavements after 5 years of service.

Blowups were surveyed visually for different treatments in 1989. The blowup intensities (number of blowups per mile) are shown in Figure 7. Blowup intensities in cracked and seated sections arc less than on the uncracked control sections by about 50 percent. Also, on the sections with added fibers, no blowups have been observed. Blowups, as defined here, are all sharp pavement protrusions that develop over the joints and which grow with time and eventually need to be milled or burned off. Blowups are relatively rare events, so the observed differences may not be significant.

VISUAL OBSERVATIONS

The severity of reflective cracks for the different treatments has been visually surveyed. Cracks in control sections containing fibers were compounded and more severe than those elsewhere , as shown in Figures 2 and 8.

Most blowups were not severe, except one that now is rough and should be milled or ground off to restore rideability. Several other blowups have been milled off during the past 5 years.

Some longitudinal surface cracks were observed in the wheelpath. The reason for the formation of such cracks is not understood. They appear to be related to the surface mixture only.

CONCLUSIONS

Cracking and seating techniques reduced reflective cracks by at least 75 percent over those occurring in the uncracked control sections.

Adding fibers to the asphalt overlay mix over cracked and seated sections reduced reflective cracking by 85 percent over cracks occurring in the control sections. The fibers also improved the pavement strength and support conditions by about 15 percent over sections without fibers . Fiber addition did not significantly reduce reflective cracking for sections that were not cracked and seated.

The 5.0-in. asphalt overlay with fibers gave the best performance among all treatment combinations with respect to reflective cracking and maintaining pavement strength.

Generally, blowup intensity on the cracked and seated sections was observed to be less than that in control sections by at least 50 percent. Reinforcing the asphalt overlay with fibers reduced rutting slightly and may have prevented blowups from developing.

TreaLinent: undersea!, 4.25 in. overlay

100

9J

8J .., " " g ] i:'l

-~ ~ j

JO ~ a

20

10

0 .......... . , ......... ,,,,, , ,,,,,,, , , , ... ...... ... .. 520 530 54Q 550 S60 570

525 535 5'5 555 565

slolCns

Treatment: Crack&seat, 6.5 in. overlay

100

90

!Kl .., :II

" 70

J I (I()

-~ !Ill

j 40

I JO

20

10

0 0 I I I I I I 1 I 1 I 1 '

fiCJ 100 710 &!1$ 705

llQlin

FIGURE 3 Dynaflect maximum deflections.

.., " " 5 ] i:'l

~ ~ ] ~ a

Treatxnent:Crack&Seat, 5 in. overlay

1oor-~~~~~~~~~~~~~~~~~~~~~

.ior-~~~~~~~~~~~~~~~~~~-l

20r-~~~~~~~~~~~~~~~~~~~-!

1or-~~~~~~~~~~~~~~~~~~~-l

0 11 I I I I I I I I I I I I I I I I I I I I I I Io o o o o o o. o o I

no 7!/J 725 735

740 745

7f/J 755 765

stott::ns


.., " " I i:'l

J ~

100.--~~~~~~~~~~~~~~~~~~~~-..

001--~~~~~~~~~~~~~~~~~~~~--1

!KJl-~~~~~~~~~~~~~~~~~~~-i

j JO=- -==-! 20

10

o' I I I I I I I I I I I I I I I I I I I 1 1 I I I I I I I Ii I I I I I I I l I I I I I I I 1 1 I I I I I

<5l 490 500 4115 4!15 Sl5

Sto 515

m ~ m

slat in

.., " J;;

g ] ~

~ j ] ~

0

fb:

TreaLn1enl: Underscal-4.25 i11. - fb

100..-------------------------. .ro .---- - ------- -----------1 801--------------------------1

701------------------------4

001----------------------l

!Ol---------------1--'<-------l

°'°~ ;( )' :?' ~ '\ ,1 I JO) ~/ __.,..,.. ><.....,L '\ I \.?"

<T I 201------------------- --l

101------------------ ------1

1(67 1077 1072

sloli::Jns

fibers are added to asphalt base layer

Treatment: Crack&seat - 5.0 in. - fb

.., " J;;

g ] ~

-~ ~ ] ~

0

8()

I

' 60

50 I

.4Q I

.lO

;o

10

I

'

' 1gBS ~ /

~ "'----~ ~

1027 l02B 1029 lOJO \031 lQJ( 10l.J 10J4 10J5

sloli:ns

FIGURE 4 Dynaflect maximum deflections with fibers added.

.., " J;;

6 ] ~

~ ~ ] !

.., " J;;

"' .5 ] ~

~ j ]

!

Treal111enl: Uuderscal-4.25 iu. - fbb

'

9J

BO

'

I &I

50 I

.4Q I

'-!.%5 ~ - /'x" ~ - ~-- ~

.lO

20

10

0

1C60 1(66 1057 1C6J

sloticns

fbb: fibers are added to both asphalt base and binder layers

Treatment: Crack&seat - 5 in.- fbb

100.--------- -------------.., rol----------- - -----------1 BQl--------------------------1

701------------------------;

601----------------------;

501------------------ ------;

'° I > ~, 1......_7L>-........: I :ioj - •"89\0c=: > ...., -=-... === 7 • I 201------------------------;

101------------------- - ----;

)DJS 1045 1050 1040

slolicns

s;;

' j J I

Treatment: undersea!, 4.25 in. overlay

100

90

Ill .e ,. s;; 70

g j ~

J ' ,.

I 20

'

0

1' I o 11111111I11 I 111111II111111I1111111I111111II111 I 1111

520 5JO 540 ~ 560 570 525 535 ~5 555 565

sWICnr


100~~~~~~~~~~~~~~~~~~~--,

sol1~~~~~~~~~~~~~_j

001--~~~~~~~~~~~~~~~~~~-t

1011~~~~~~~~~~~~~~~~~~--1

I I

0 I I I I I I I I I I I I I I I I I I I I I

MO 100 710 - l'm

........ FIGURE 5 Dynaflect minimum deflections.

TreatinentCrack&Seat, 5 in. overlay

100

90

80

s;;

g 70

j 60 .!S

.~ so ·' ,. j

! 20

10

0 .. no 7.JO 740 750 760 ns 735 745 755 765

stali:::ns


100

90

!ll

s;;

·' 70

J 60

.~ so

·' ,.

I 20

10

0 ............ , ...................................... ~ ~ ~ - ~ D ~ ~ ~ ~ ~ -

.c g j c!l

~ .<

" j ~

Q

.c

~ j c!l

.~

.<

" j ~

0

Treallnent: Underseal-4-.25 in. - fb

100

90

80

70

60

!C

'° .JO

20

10

0

1007 1077 1072

sloliais

Treahnent: Crack&seat - 5.0 in. - fb

100

90

80

I

60 J

) ""iO

'° .JO

~ -----:.,/" -20

'""' 10

0

1027 1029 10J1 1033 10.lS 1028 10.JQ IOJ2 103<

slalicns

FIGURE 6 Dynaflect minimum deflections with fibers added.

.c

6 i 0

g < :>

j ~

0

.c

" 6 j .>;

.~ < :>

] J

TrealrnenL: Underseal-4.25 in. - fbb

100

90

8J

)

) 60

~

40

.JO

/ ~

~- -20

10

0

1(J;Q 1oo; 1057 1003

sloli::ns

Treatment: Crack&seat - 5 in.- fbb

100

!IQ

80

70

60

~

'° .JO

20

10

O' I I I I I I I I I r I f I I l I I

10.lS 1045 1040 1050

stoti:ns

V.l N

;:J ~

< "' "ti a ::ti

;;i ::::! a < ::ti t>i

"' ~ ::ti (] ::i: ::ti r,, (] a ::ti 0

'" °' 0::

El-Sheikh et al.

4-0

ci c

'---"

>-, ;-':::::' (j) c Q)

-+-'

-~ (j) Q_ :::J s 0

_.D

4

3

2

0

33

-·

I

A B c D A 1,A2,B1 ,82

treatment

FIGURE 7 Blowup intensities (1989).

FIGURE 8 Typical reflective crack (left) in fiber section and (right) elsewhere.

REFERENCES

1. C. Crawford. Cracking and Sealing of PCC Pavemenls Prior lo Overlaying with Hal Mix Asphalt: S1ate-of-1he-Ar1. Information Series 98/89, National Asphalt Pavement Association, Riverdale, Md. 1989.

2. M. D. Harness. Cracking and Sealing of Concrele Pavemenl on l-74. Report IN84-01A, Indiana Department of Transportation, Division of Research, West Lafayette, Ind., 1987.

3. M. D. Harness. Performance of Biluminous Mixlures wilh Polypropylene Fibers. Report IN84-01B, Indiana Department of Transportation, Division of Research, West Lafayette, Ind., 1987.

4. M. D. Harness and J. J. Sudol. Inilial Construction and Interim Report: Cracking and Seating of Concrete Pavemenl on l-74 and Performance of Bituminous Mixtures with Polypropylene Fiber. Indiana Department of Transportation, Division of Research, West Lafayette, Ind., 1986.

5. K. Majidzadeh and V. Kumar. Manual of Operation and Use of Dynaflect for Pavement Evalualion. Resource International Inc., Ohio Department of Transportation, and FHWA, Department of Transportation, U.S. 1983.

Publication of lhis paper sponsored by Commitlee on Pavemenl Maintenance.

Cracking and Seating of Concrete Pavement on 1-74

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