GUIDELINES FORSOIL AND GRANULAR MATERIAI,-

STABILIZATION USING|IEMENI L|ME & FLY ASH

pubtished byINDIA^N ROADS CONGRESS

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?():SP:B:l-20' l 0

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Personnel of

CHAPTER 1:

1 . 1

1 . 2

1 . 3

1 .4

CHAPTIiR 2:

2 .1

2.2

CHAPTT]R 3:

3.2

3.3

3.4

3.5

ckRpren c:

3.1

CONTENTSi:

the Highways Specificatjons and Slandards Cr:nrmittee

INTHODUCTION

Purpose

Scope

Definitions

Effective ness of Stabilization

MECHANICAL STABILIZATION

Mechanical StabilizationDesign of Mechanicaily Stabitized Mixes2.2.1 Stabilization using so-ft aggregaies

(Mehra's method of stabilization)2.2.2 Design of mechanically stabilized nti;<es: Conrbining

two rnaterials based on plasticity2.2.3 Rothfutch rnethod for design of soil_ar;glegate mixes

cENERAL GUTDELTNES FOR SOtTJ,cRA|NULARMATERIALS STABILIZAfloN

Factors to be considered3.1.'l Ume stabilization3.1.2 Cementstabilization3.1 .3 Lime-fly ash (LF) and lime-cernent_fly ash

(LCF) srabittzationDesirable properlies of Lime, Cementand FlyArsh forStabilization

Selection of StabilizerTwo Stage Stabilization Using Lime lollcrwed by CerneinlM.odifi r;alion and Cemenlalion

SPECIFICATIONS AND TEST REQU|FIEMEN,IS FORSTI\BIUZED MATEBIALS

General Requirement

IFC:SP:89-20 10Ii

Page No_

t r /

1

J

3

3A

tf

D

B

1 1

1 11 1i l

121 2

1 3

1 6

1 6

1 7

1 B

1 B4.1

RC;SP;89-'2010

4.2 Slabilization with Cemenl

4.2.1 Requirernentforsoil nrodification/subgradclimprovernent

4.2.2 Requirement for bound sub-basesrbases'4.3 Stabilization with Lime

4.3. 1 Requi rement f or soil nrodif ication/sub graderrmpf ovement

- ,1.4 Stabilization with Lime and FtyAsfi (LF),1.5 Stabilization with Lime, Cenrentand FlyAsh

4.6 Cement Stabilized FlyAshtl.7 Test Requirements

4;,7 1 Unconfined cornpressive strength test4.',7.2 Durability of stabilized materials

IHAPTER 5: CONSTRUCflON OPERATIONS

€;.1 Procedure of Stabilization

|:i.2 Mix-in-PlaceStabilization

5;.3 Plant-MixStabiti;:ation

5;.4 Compaction

IHAPTER 6: QITALITY ASSURAT{CE

6.1 Ge,neral

6.2 PrelirninaryTrial

6.3 Sampling and Te:;ling Frequency6.4 Stcrrage and Handling o{ ttre Stabilizer6.5 Control of the Moisture Content6 6 Control of the Stabitizer Conlent6.7 RoutineStrengthDeterminations

;hapter 7:

1 B

1 B

1 8

1 9

1 9

2 1

2222232324

26

26

26

29

30

31

3'tJ I

313233

-3334

35

35

353637

3738

1 1t , l

t . z

7.37.4

t . c

7.6

PRECAUI1IONS T'O BE TAKEN WHILE USINGST/\BILIZED MAT'ERIALS

GeneralCracking in Stabilized LayersPrirnary CrackingTralfic Associated CracksDurability of Stabilized Malerialscontrol of Feflective cracking in cement Stabilized pav()rnernts

lECl:r3P:89-21010

PERSoNNEL oF THE H|GHWAY$ SPEc|F|cATloNS A$|DSTANDARDS COMMTMEE

(As on lst MaY, 2010)

.t. sinha, A.V. Director General (RD) & Spl. secrelary, Ministry of f]rriad(Cmvenor) Transport & l-lighways, New Delhi

2. Puri, s.K. Adcll. Director General, Ministry of Road Transport &

(CoConvenor) Highways, New Delhi

3. Kanrtasamy c. chief Eryineer (R) s&Fl, Ministry of Road Transport &(Member-Secretaryt) Highways,NewDelhi

Mentbers

4. Datta, P.K. Executive Director, Cc'rsulting Engg. Services (l)Pvt. Ltd-, New Delhi

5. Gupta K.K. Chief Engineer (Retd'), llaryana PWD

€. Sinfra, S. Adcll. Chief Transportatron Engineer, CIDCO,Navi Mumbai

7. Kadiyali, Dr. L.R. chief Execuitve, L.R. Kadiyali & Associates, New le,lhi

B. Katare, P.K. Director(Projects-lll), NationalRuralRoadq DevelopnrenlAgency, {Minislry of Rural Development), New Delhi

9. Jain, Dr. S.S. Professor & Coordinatcrr, Centre of Trarsportation EnEg.,llT Roorf,,ae

10. Reddy, K. Siva E-in-C (Fi&B)Andhra Pradesh, Hyderabad

11. Basu, S.B. Chief Engineer (Reld.), MoRT&l'i, New Delhi

12. Bordoloi, A.C. Chief Engineef (NFl) /rss?m, Guwahati

13. Raihore, S.S. Principal Secrelary to tlte Govt. of Gujarat, l1&B Deptl.Gandhinagar

14. Pradhan, B.C. Chief Engineer (NH), 'Govt. ol Otissa, Bhubaneshwar

15. Prasad, D.N. Chiel Engineer (N]-{), lFlCD, Patna

I6. Kumar, Ashok Chie{ Engineei, Ministry ol Road Transport & Highway:s,New Delhi

17. Kumar, Kamlesh Chief Engineer, Ministry ol Road Transport & Highways,New Delhi

18. Krishna, Prabhat Chief Engineer (Betd), Ministry of Road Transport & l-lighurays,New Delhi

19. Patankar, V.L. Chief Engineer, Ministrl, ot Road Transport & Ftigfrwavs,New Deliri

20. Kumar, Mahesh Engineer.-in-Chiel, Haryana, PWD

21. Bongin*,ar, P.L. Advisor, L&T, Mumbai

22. Sinha,A.K. Chil.i Engineer (NH), UP PWD, Lucknow

(i)

IRC:SP:89-2010

.23- Shamra, S.C. Director Generirl {Rll) li AS riRc,t<,.), Ministry of Road Transport &. Highways, New Delhi

24. Shamta, 0r. V.M. Consultant,AlVllt- Nevv Cielhi

25- Gupta, D.P. Direclor Geneml (RD) 8, AS 1Rr.rtcl.), Ministry of Road Transport &Highways, New Delhi

26. Mornin, S.S. Former Menrber. Mehareshtra F'ublicl Servir:e Commission,Mumbai

27. Reddy, Dr. T.S. Ex-Scienlisl, Grnlral Fiicard Research Insfitute, New Delhi

28. Shukla, F.S. Ex-scientist, Central Fl;oad Research Instilute, New Delhi

?-9. Jain, R.K. Chief Engineer (Retd.) tlaryarna FVr/D, Sonrrpat

30. Chandrasekhar, []r. B.P. Direclor (-lech.), NatiorrLl Rural lRoad Development Agency(Minislry of Rur;al Developmenl) New Dethi

31. Singh, B.N. Chiei Engineer, Ministry' of lloarj Transport ,l Highways,New Ddhi

'

32. Nashkar, S.S. Chiel Engineer (NH), F\! '(R), Kolkata

33. Haju, Dr. GV.S. Ghief Engineer (B&El), Andhra F1'radesh, Hy,Jerabad

34. Alarn, Parvez Vice President, Hinduslern C,onstn. Co. Ltd., Mumbai

35- . Gangopadhyay, Dr. S. Director, Centrerl Road Flesearclr Instilute, l,lew Delhi

36- Sinha, V.K. Director General'(F[)) & SS riRr:rtd.), Ministry of Road Transport &Highways, New Delhi

37. Singh, Nirmal Jit Direclor GeneraLl (RD) & .SiS (lFetd.), Ministry of Foad Transporl &Highways, New Delhi

38. Jain, N.S. Chief Enginner (Retcl.), ldinistry of Road Trernsporl &Highways, New Delhi

39. chiel Engineer (Plg.) Ministry of Roacl rrarrsport & Hitlhways, Nerv Delhi

40. Representalive DGBR, Director,ate Gerreiral Elorder Roads, New Delhi

Ex-Offici<t Memlxtrs

1. President, lRc (Liansanga), Engineer-in-chief and secretary, pwD Mizoram,Aizawl

2. I Director General (RD) & (Sinha, A.V.) Ministry of Ficrad Transpnrt & Highways,, Spl- Secretary New Dethi

3" Secretary General, IRC (lndoria, R.P.), Indian Roarls Oongress, Nerrv Delhi

C o r re s po n dii ng M em.be r:s

1. Justo, Dr. C.E.G Emeritus Fellow, i3angalon: Univ, Bangalorer

2. fftaftar, M.D. Consultant, Run,,,r,al Cientfre, Mlunrbai

3. hgarwal, M.K. E-in_C (Retd), H,aryana, F)WD

4- tlorge, V.B. Secrelary (Roads) (Feic.l, Maharashtra pWD, Mumbai

( i i )

IRC:SP:89-2010

CHAPTER 1

INTRODUCTIOI.I

It was discussediin the first meeting 07'032009 o{ newly ':onstiluted 'E:mbankrnenl' Ground

lmprovement and Drainage Committee' (H-4) that lollowing IRC; guirJelirre:'; which deals with soil

stabiiization need revision in the lighl of current practices and latest lech,nological dev'elopments

in the field. The identified guidelines vrere:

1) IRC:28-1967: "Tentative {ipecifications for the Construction of Stabilized Soil Roads

withSoftAggregatesinareasofModerateandl l ighFl i l infal | ,

2) IRC:33-1969: "standard Procedure lor Evaluation arto Condition Survey cf Stabilized

Soil Roads'

3) IRC:49-1973: "Recommended Practice for the Pulverisation o1'Blacl< Cotlon Soils lor

Lime Stabilization"

4\ lFlC:SO-1973: "Recommended Design Oriterrorrior llre use of rllement Modified Soils

in Boad Construction

5) IRC:51-1992: 'Guidelines tor the use of Soil-Ume Mixetsr in Road Conslruction'

6 ) IRC:BB-19B4: "Recommended Prac t ice f ' ' l r L ime-F l ) ' l \ sh S tab i l i zed So i ls

Base/Sub-base in Pavement Construclion"

Allthese guidelines were reviewecl and it was found thal. lFlL--3:3, {$, SCl, ti1 and BB are relaled to

soil stabilization with admixtures llowever, IRC-2€| derals with soil and soft ,aggregales

stabilizaLtion, fhe revised guidelines;presented through this;docunt,etlt er(lompass tlre review of

soil stahilizalion which is the process whereby soils and related nratr:rii,tls are made slronger

and more durable by nrixiqg with a stabilizing agent. Althcugtr milny :;terbilizing agents can be

used, cement and lime are by farlhe rnost important and tlre guidelines ilnainly concentrate on

use of L.ime, Cement, Lime-lly ash/Lime-cement fly ash as stabilrzrrr T lre guidelirtes inclurle,

generalfeatures of slabilization, guidelines {or soit/granular malerial stabilization, speci{ications

and tesl requirements for stabilized materials, conslru,;tion pro<rcclur,r:, quality conlrol and

limitations on the use of stabilized materials. These guirielines ha.ve b€:ren rnade considering

prevailing I ndian and International practices.

The drerft of the gr.ridelines was prepared by Shri Sudhrr Malhui, lr'lermber-Secretarey, l-l-4

Committee and his collegues namely S/Shri R.K. Swami, Mrs Umet Arun ancl U.K. Guru Vittal.

The guidelines were linalised by H-z' Committee undertlre Oonvenorship of Shri Maltesh Kumar,

Engineer-in-Chief, Haryana, Public Works (Building and Fl:ads) Deprarlnlent.

lFtC:SP:89-2010

During the seventh Meeting of Enrbankment, Ground lmprovemeni 8r Drairtit'ge cornittee (H4)

(penonnel given belowjnrr-1.: on 09'04,2010, the draft document was approverd lor crrtrculation to

il;'gil+ SpeciRcairions & Stetndards Cornmittee (HSS)'

Kumar, Mahesh

Sharma,Arun Kttma:'

Mathur, Sudhir

Chahd, Faquir

DhodaPkar,A.N-

Gairia, Maj. Gen- K.T',

GuPta, SanjaY

Gupta, Dr. PradeeP

Jain, Naresh Chi:rrd

Jain, M.K.

Jalota, Di- A.V'

Kansal, R.K.

Korulla, Nlinimol

Koul, R.L.

Kumar, Saterrder

Pradhan, B.C.

Presidenl. lRC

Director Gen,eral(RD) & SS, IvloR-IH

Secrelary General, IRC

- Convenor- Co-Convenor

- Member Secretary

Menbers

Rao, Prof' CiV

Rao, Prof' F.J.

Sangal, M.M

Singh, R-B.

Saha, D.C.

Sen, Samiren

Thomas, Dr. JitnmY'

Verma Maj. V'0.

Chitra, R.

(ReP. Dir. CSI\4RS)

Tlwari, Dr.A.Fl'

(ReP. of DGBR)

C.E., PWD, lrt:ghalaY;a

Conesponding Members

Verma, M.S.

Ex-Ofticio Memturs

(Liansanga)

(Sinha, A.\/.)

(lndoria, R.P.I

l . h e d r a f t d o c r l m e n t w a s s u b s e q u e n t | y a p p r o v e d w i t h s o r n e r e m a r k s b l r t h e H i g h w a y sspecifications and slandards commiltee in its meeting held on r11.05.2010.

-[he diratt docum€lnt

was approved by the Executive comrnittee in its meeting held c,n 111.05.,2010. l[h':i council in its

meeting held at Munnaq Kerala on 22.05.2010 approved the documeml wifl 'h sorrlre commenls'

The document iafter incorporaiing comments of council Members rrrrzts aptlrorr€rcl b),r the converpr

of Highways Qrociflcations & litandards Committee for printin0'

1 .3

lFtC:Sf):89-21]10

1.1 PurPose

These guidelines suggest the criteria for irnproving the engineering pioperties ol srrils arrcl granuli;rr

ntaterials used for pavem(lnt base courses, sub-base courses and subgrade's by ttrer USe r;rf

additives/stabilizers, whiclh are rnixed into the soil/granular materials to elilect tlte: desir€rd

improvement. A number c,f additives are irvailable to improve the physical end engineerirrlJ

properties of these materierls; however, this cJocument restricts itself to stabilize rs sur:tl as lim's,

cement, fly ash or a mixturr: o{ the above additives.

1.2 Scope

These guidelines prescribe the appropriate type or types of additives to ber u:sed wilh tlifferent

soil types, procedures tor deterrnining a design treatment level for each type oi atJclijiive and

recommended constructic,n practices for incorporating the additive into lhe s'cil. Thers;er criteila

are applicable to alltype of roads and airfielcis having a slabilized pavement l,ayer.

Definitions

a) Sol'ls; Naturally occurring nraterials that are used lor lhe c;{instruciiL:tt of z;tll

except the surface layers of pavernents (i.e., concrete arrd aspha.lt) and ttrirt

are subjrect to classificalion tests {lS 1498) to provide a gr;neral's)ncept (rf

their eng ineering r;haracteristics,

b) Additive,s: ManufacturerJ comrrrercial products that, when added to llre soil in

lhe proper quantilies, improve some enginearirrg i'l ;a;':iclolislics rrl ther soil

such as strerrglh, texture, workabilily, and ptasticity. Additirre.s; .rddrerx;r:d in thismanual are limited to ccnrt:nt, Lime altd Fly ash.

c) gabilization: Stiabilization is the process of blending and rnixirrg mstoiials wilih

a soil to improve certain properties of the soil. The process may includtl lheblending of soils to aclrirsve a desired gradation orthe rnixirtg ol corrnerr.:iallyavailabler addilives lhal may alter the gradation, texlure or plilr;ticity, ()r acl as abinder fc,r cernenlation of the soil.

o) Mechanical Stabilization: Mechanical stabilization is accom[,lishe,J iry mixingor blending soils of two or more gradations or mixing soil vr,ith agrlregatras toobtain a material meeting the required specification. The srril blernding milytake place atthe conshuclion site, a central plant, or a bonc'w iarea. Tlr': blsrdcdmaterial is then spread and compacted to required densities by <nnl'entiorralmeans.

e) Additive.lChemiqal Stabilizalion: Addilive stabilization is achie'v'ed b;' lr'19addition of proper percenlages of cement, lime, fly ash orr -tnt,1t"u116ps 'ofthese materials to the soil. The selecJi.Jn of type and quantity c,r lhe trxn centai:le

IRC:[ iP:89-2010

ol additive to be used is depentjerrt upon 1:he soil Olassification and the degree

of improvement in soilquality desired' Generally, $maller amounts of addilives

a r e r e q u i r e d w h e n i t i s s i m p l y c e s i r e r j t o n r o : l i f y s o i | p r o p e r t i e s s u c h a sgradation,workabi|ityandplasticitl.Whetlitisdex;iredtoimp,rovelhestrengthand durabitity significanily, largerr quantities ol iadcJitive 3rr3 usad. After the

additive has been mixed with tre soil, spreading, sprinkling water and

compactionatoMCareachietredbycon.renli.onia|means.

I Modificafion: Modification reft:rs to the r;tabiliziltion process that results in

improvement insomeproper t .yc , f theso i lbu tdoesnot ,byrJes ign , resu | t inasignificanl increase in soil strength and dttrability'

t.4 EtfectivenessofStabilization

ravemenl desigrr is based on the premise that nrinimu.rn spe,cifi,:d structural strength will be

achieved for each layer of material in the pavemernt syslent' Eiar:h layer must resist shearing'

avoid excessive deflections that cause faligue crackjng withirn the l:ryer or in overlying layers and

prevent excessive permanent deformalion through densiiicirtic'n' '{s the quality of a soil layer is

irrcreased, the abrlity o{ that layer to distribute thra loird over a greatr3r area is generally increased

so that a reduclion in the required thickness ol lhe pavernent layerrs may be prermitted' Some ol

the attributes ol soil modificatioir/stabilization are indicalecl belovr'

a) eualily improvemenf The nost comm()rl irnp'rovements achieved through

stabitization include better s;oil gradation, rer:lluction of plasticity index or

swelling polential and increarse, in dunabili\ 'and strength' ln wet wealher,

stabilization may also be useC lc provicler a vror:1<ing platform for construction

operations. These types of soil ,qualitry intprovrr)menl are relerred to as soil

modification- Stabilization can errhancelhe pr<perlies of toad materials and

give pavement layers the following atlributes:

A substantial proportion of lherfu l;lrength is retained even after they

become saturated with water.

: ;:'J::"*,::ffi;::;:,,,. Materials in the supp,crting ftrrrer cannot contaminate tire stabilized

layer.

r The elastic moduliof grranrrlar layers; crlns;trucled abrlve stabilized layer

. ffiiffi::, materiial is suitetblt;' for use as cappitrg tayer or workingplatform when the in-silur maleriaf il; excessively wel or weak and

removal is not econonrica .

IRC:SP:€19-2010

b , ) T h i c k n e s s r e d u c t i o n : T h e s t r e n g t h a n d s l i f f n e l s i s o | a s o i | l a y e r c a n b eimprove rJ tn roug r r theuseo |add i t i ves tope tn r i l a re lduc t i on indes ignthicknessofthestabi|izedmateria|compareclwilhanun-st;'tbi|izedorunboundmaterial.

c )Poss ib |ep rob lems :The inc rease in thes t r cn$h t l | pavemen t laye rs i sa l soassociaterl wilh the {ollowing possible problems: .

r T r a f f i c , t h e r m a l a n d s h r i n k a g e c r a c l . s c a n G a u s e : s t a b i l i z e d l a y e r s t ocrack.

.Crackscanre f lec t th roughthesr . r r fac ingar t ,da l |owwater toenter thepavement structure-

o ll carbon dioxicJe has access to the nlaterial, the sli'tbilization reactions

arereversibleandthestrengthoflher|ayerscandr=lcrease.

r l-he conslruction operations recluir:e more s;kilis ilnd controi than lor

eouivalent u n-stabilized materials'

These issues have been further highlighted in Ohapter '/'

IHC:SP:89-20lCl

CHAPTER 2

MECHANICAL STAB ILIZATION

2.'t lt|echanical Stabilization

Mochanical stabilizatron is a process in which materials are propc,rtionrxl to obtain desiredgradation and plzrsticity of lhe mlx. Correctly proportioned material (aggregzrte arrd soil) can be

adequalely compacted to form a mechanically stable pavemenl la1'sr.'t'"1r method is calledrner;hanical slatril ization. Thus; the basic principles in this rnett^od of stabiliziation are :a) Proportioning ilnd b) Compaaion. lf a granular soil containing neglligible fines i:s rnixecJ with acertain proportion of binder soil, il Ls possible lo increase the stabilit,l. Similariy the r:;tability of afirn grained soil can be considerably improved by mixing a suitatrle prol)rsrtion lrf granularrrnterial to get a desired gradation.

Mechanical stabilization has been successfully applied for sub-baser and biirse courseconslruclion. ll has ak;o been used as a surface course for low cost roads l;uc:h as village ioaGwhen the traffic ernd rainfall are low. The desirable properties of soil aggrol;ates; nrixturgs aresirength; incompressibility; fewer changes in volume and stability vrith vilr,atiorrs iin moisturecontent; good drarinage; less frost susceptibility and ease of compaclion. lt is glenererlly believedihat the stability of a soil aggregale mix can be increased by increasing its rjry den:sity. Henceprolrcrtioning of rnixes is done to altain maximum dry density.

The factors to be considered in ttre design of mix are gradation, density, irrcl'cx p,roperties andstability. Of these, the gradation is the most inrpodant factor, The parlicle s;i;url dislnbution thatgives maximum density is genorally aimed at. Fuller's formula nrzry be u$ed lo obtain thetheorelicalgradalion formaxirnum density and is given by:

wtnre

p= 100 (d/D) 'z

P - per cent liner ttran diameter 'd' (mm) in the materriarl

D = diameler of lhe largest particle, mm'l-he

following are the recommended values ol the liquid limil and plar;tic irrde:< for tihe materialpassing 425 micnrn sieve, to be used for mechanical stabilization

Base Course Surface Course for Cira'uel Roads

Liquid limit

Plasticity lnclex

25 per cenl max.

6 per cent mex.

3i5 per cent rnax

l5 to .10 p{3r cent

IRC:S;F' : ,89-11O10

2.2 Design of Mechanically Stabilized Mixes

When a few materials are available in the near vicinity of site, it is necessan/ tcr mix the n in ,sur::lta proportion, which would produce a mix v,tith highest density- As an exampl,e if coar:;;eaggregate, sand and fine soilare availablefrom three deposits orborrow pits, it is tirsl r:sserntialto decide the proportion of these cornponenl malerials. The most cornmonly tr,Jopted graphhalrnethod {or proportioning i:; the Rothfutch's rnethod. Details of Rothfutch methocj are irrc:sented inSection 2.2.3. The design based on combining two materials (soiland aggregates)on lhe tlasisof lheir sieve analysis to a,chieve specified gradation is given below:

o Column 2 and 6 in the Table give the parlicle size distribution of mate rrialA a rtdB which do not satisfy the gradalion requirement of lhe specificatirrn.

o Column 3 shows the standard sieve sizes, colurnn 4 shorars th e recornrmendedlimits for a particular pavernent course and column 5 shovvs the avenlge valucof corra;ponding limits shown in colui'nn 4.

. ThG invt>rse ratio of lhe totals in columns 1 and 7 gives ther proporlirrn c'f thematerials to tp mixed to obtain the desired mix.

A : B = z l 5 : 1 3 9 ( 1 : 3 ) .

r Mixing 25 percent of lhe nraterialA and 75 percent of malerial B woul,clgive lhedesired gradation as sholn in the Table.

Table I Mixing of Aggregates for Desired Gradation

NumericalDifferencebetween

rnaterial Aand

averagepercentpassing

Material Apercentpassing

Sieve size Recomm-endedLimils

percentpassing

Averagepercentpassing

Materiall I Nurneric:B percerrt I oinierencpassin'g I betfwerer

I materialI B anrJII averageI perrcerrt

I pasising

Col 1 Col 2 Col 3 C o l 4 Col 5 Col 6 | (. i l l7

100 40 mm 100 100 1 0 0

t1 98 20 mm 80-100 90 7i) l 7

26 94 10 rnm 55-80 68 5r; t 3

33 B3 4.75 mm 40-60 411 8

32 72 2.36 mni 30-50 ' 4 0 3ft 5

33 55 600 pm 15-30 22 21 1

7 1 7 75 pm 5-15 1 0 I 1

Total = 139 Tot;l l =,4

N;ffi;lldifiierence Ibelfweren Imaterial IEl anrJ Iaverage I

perrcent Ipasisrng I-i-iil- -l

---:-*-l-ir--

I-;__ I*--r- I-*----*"-1

5 l-------*-"-t

. 1__ _i1 l

g,l--,gl

IRC:SP:89-2010

22.'l Stabilization using soft aggregates (lt.le*-a's,nethod of .stabitization)

When hard variety of aggregates is nol locally availabler, lhe local soft aggregates may have tobe used lor conslruclion in order to keep the ccxtstrur:tion cost as low as possible. The softaggregate have low crushing strength and lo,w ar3gregette imparct value. Still they have beenadopted in the construction of mechanically stallilizerJ sub-lca:,;e, base course and even inwearing course layers. Commonly used soft aggregates {rx ncad cc}nstruclion are kankar, moorum,latedte and broken brick aggregates. Because rlf ll'ie lou,s;lrength, these aggrcgates are likely tobreak down at their points of conlact. lf these zrggregatr..r; ;are milled with surtable proportion ofsoil so that eacir particle of sotl aggregate is ervek>ped by soil, there would not be any problemof crushing of these aggregates during compaotion or unCrertrafl'ric load.

Mehra's rnethocl of construclion can be adopted forcons':ruction ol lowvolume rural roads. ln thismethod, base course rnaterial consisis of conrpa,c;ted soil with s;,and content (of size less than0.425 mm and greater than 0.075 mm) being not l,sss than 150 p'ert.:ent and plasticig index 5 to 7.Wearing course materialmnsists of brick aE;reglates andsoil mixed in the ratio of 1:2. Thesand content in the soil should be less lhan 3il p€rrcenl: ilnd ptas;ticily index 9 to 12. However,when biluminous surface treatment is required/de:;ired, !ne pl:rsticity index s;hould be limited to8 lo 10. This method, proposed by Prof.S.R.Mehra, is br:iefly giivern below:

1) Soilis collected from approved borrovv pits aLrxl slacked orr roadside.

2) Water is added upto OMC and soil is rrrixec| a.rrd spread to desired camberand grade.

3) 11,5 cm thick loose base coursermateriai (sandy soil) is spread and rolled by8 tonnes roller to a compacterJ ilrickness of 7.S t;m.

4) Surface course malerial (briclk aglgregatc' anrJ s,cil in the ralio 't:2) mixed withadequale water is spread to 11.{i cm lcos,a lhiickness and tl"re layer is rolled byI tonnes roller to a compacterJ thickness of 7.5 r::m.

5) After rolling, the surface is wraterred anrj left ol'ernight. The surface is againrolled and finished.

6) The road is closed to traffic lor 4-15 days :urd kepr: sprinkled urith water. For nextfew days, only rubber-tyred traflic is allolvr:d and after about 2 weeks, the roadis opened to alltraffic. Mehra's; nrelhod ol construction can carry S0 tonnes oftraffic per day in places of liglrt rainfalrl. With biluminous sirrfacing, the roadgives satisfactory service upto 2{)0 tonnes per cl,ay even in places with hearryrainfall.

tL2-2 DesiEn of mechanically stabilized mi.res: c'ombining two materials based onplasticity

L-et there be two soils A and B which are to be nrirerrJ to gert a soil cf required plasticity index p.

fitep-l Deterrnine the plasticity index ol lhe lwo soiis. Lell lhesr.- be Po anri p, for soil A andSoil B respectivety.

IRC:SP:89-2010

Step2 Determine from sieve analysis for each soil' th'e p']rcentttlle of nlaterial pa:;sing 425

micron sieve. Lei lhese be So and S, for the Soil A and SOil B rerspectively. Then lhe

percentage of SoilA to be miied witn Soit B to gel the desiired prlasticity inclex i.e" P,

is given by the relation:

e / p - . p '

Materiat A % = ss(p;hqi=il

2.2.3 Rothfutch method for design of soil-aggregale rrixes;:

Rothfutcfr rnethod is adopted when a number of materials ,are lo be mblerJ together lo obtain a

combined material conforming 1o a desired gradalion. lt is to b€r nolied that nonei of 'these

individual consliluents of combined materialwould be abrle to satisl/ the d'r'sired gradation' The

ratio of mixing these individual constituents is determined biased on methodology pnrposed by

Rothfutcl"r. In this process, the first slep would be to detenninerthe de::ireclgradation. Tlris maybe

based on the specification limits or as per theoretical erquatiorr gi'uen by Fuller or other

research,ers. The procedure involves drawing the gradaiion curve:i on graph paper and then

{inding orrt optimurn mix proportion as described below:

. On a graph sheet percent passing is rnarlrecl on Y iaxis in a suir;able linearscale. X axis represents lhe particle size Cistribuilpn, nrrhich is to tre rnarked,

based on desired gradation.

" The comer O and O' are joined by straigiit l ine.

. OO'represents required gradation linet'

. Sieve sizes are marked corresponding lo percent ;:assing of required

gradation. This can be done by locating the average percentage specified lor

any particular sieve, locating that point ,cn tlre Y axir; and tlnen proceeding to cut

the line OO'. Atthe point of intersection of iltis horizcrntalline and OCI, a vertical

line is drawn to cut X axis. This intersalion poitrt orr ,l.i axis represents thesieve size selected for.the desired grachlrion. In this manner, all the .sieve sizes

-are marlced one by one on the X axis.

o Gradatkrn distribution of matorials A, B and C arer thren drawn, by using the. sieve sizes marked on the X axis and llher oercenl,age finer rnarked on Y axis.

. Balancing line for rnaterials A, B and C a,re drrawrr in such a way that area on

either sitje of balancing line and gradation curve ale a1ui,tl, Balancing lines are

straight lines which represent the paniicle rsizer distri.rution of respective

. material in a best possible manner.'[his; can be acccmplished by using a, lransparenl plaslic scale, moving it on either sider of tf re material gradation

curve and counting the number of square's enclo,sed between balancing line

. and material gradation curve. The balarrr;ing line :;houlrJ be drawn in such amanner lhat number of squares (area) on either sicle of balancing line and lheselectect aradation curve should be equat.

l|:lC:SP:89-2010

" T h € o p p o s i t e e n d s o r t h e t w o a d j o i n i n g b a | a n c i r r g | i t r e s a r e l t r e r r j c i n e d . :cThepo i in tsvyhere these jo in ing | inescutoo ' represent theper ( ;en tageof tha t

materialin the mix'

The m'ethod is illuslrated in Fig' 1 below:

B A S 8 F E G O

O H G OORICINAL C1JRVE

OASHED CURVE

,olN UoTIOM oF l',c

NTERSECTING C'T

G

; wlTH TOP OF Dl-t: BOT-IOM OF OH wlTH IOPGO:

A T M & L : P R O J E C T F R o M M . 8 L c ) \ Y - A x l S

Cnx;hedStff€

2 3 5 4 .l1m

SIEVE SIZE

g)

ttI

I

IuzG

F2ud,U

l 0

O H 7 5 6 0 0Mict6 Micrc.

mh

Frig- 1 Rothfutch Method ol Designing soil-Aggregate ltilixers

1 0

IRC:Sit) :BSl-2t l ) ]0

CHAPTER 3

GENERAL .CUIOT'IIruES

FOR SOIUGRANULAR MATERIALS STITBILIZANON

3.1 Factors to be Considered

ln the selection of a stabiliz{lr, the taclors thal must be considered arer thr: type 'lf Soil tr: be

stabilized, the purpose lior which the statlilized layer is used, the soil imSrrovement cesirecl the

required Strength ancl durabillty of the stabilized layer and the cost and en"rirg'rmenlal conditions'

The following parameters are required tO be considered while selecting the type r:f S;labiliz'ilr'

soit types and additive.s: There may be more than orne candidale slabilizer

applicable for particular soiltype. However, there are sorn(| gener(rl gui&riines

thal rnake specific stabilizers more effeclive baseld tln soil grarrularity,

plastbity, ortexture. Portland cement forexample can tie used witlr a varir*yof

soil types; ho,wever, since il is imperative that the cement be nrrxed intinrately

with the Jines; fraction (less than 0.075 mm size), the mcre plastiic nrattrrials

should be avoidetj. Generally, well-graded granular malerials ti^ral pollsess

sulticient {ines to produce a floating aggregate matrix (h,cmogen':,us rni:rlure)

are best suited for cemenf stabilization. Lime will reacl, with soils of mediurn to

high plasricity to produce decreased plasticity, increasocl',vorlr:abrlity, reduced

swell and increased strength. Lime is used to stabilize a variety rof matilrials

inclurling weak subgrade soils, transforming thenr into il "working tah"e" or

suFtrase; and wirh rnaroinal granular base materials, i'e', clay'gravelrs' ''61t1t'

gravt:ls, to {orm a strong, high quality base course. Fly' otn is a po:zzr::rlanic

material, i.e- it react$ with lime in powdered form in prcs€nce of ruaier a:rrrd is,

therefore, alrnostalways use.d in combination wilh lime in soils tiral ltave lillJe or

no plastic fines. lt has often been found desirable to us;r: a s;rnall arnottnt of

Portlnnd cement with lime and {ly ash for added slrent3th This corttbirra lron of

Lime-cernerrt-Fly Ash (LcF) has been used successlfully in suhrbaso cr:)urse

slabiization.

GeneralGuidetines.The following are general guide lines when consirJering

stabilization with different additives.

3 .1 .1 Lime stabihization

Clay,ey soils including heavy clays, moorum and other so ls met vvithin erlluvial

plains can be effectively treated wilh lime. For effectiver stabili:lation, a soil

muSl, have a fraction passing 425 micron Sieve not lerss :han | 5 ;len-rerrt and

Plasticity lndex (Pl) should be al least '10 percent.

For effective stabilization, it b desirable that the percentage retained cttl425

micr,ln sievet shquld be well graded with uniforrnity coeflir:ienl rtol. lesr; than 5'

a)

b)

11

IRC:SP:89-2O10

" Organic matter in the soil selecled foi'src,ilstirbilization should not be more than2 percent and sulphate conten t shoulcl not exc eed 0.2 percent.

" pH value ol 10 or 11 is desirecl ior po:zolanic, reaclion to take place betweenclay minerals and lime fortfrel'ormation oJ cenrentitious compounds.

o Soils having organic malter and s;oh.rble carbonate/sr.rlphate contenls inexcess of 2.0 percent and 0.2 percenl respecltively require special studies.

" Some materials contain amorphous r;ilir:,a wihich although has low plasticity butreacts with lime to lorm the rnecesszriry (:iemr3nilation products and should thusbe considered for stabilization with linre,.

o Materials containing high Kaclrnite al; the lba*;ic clay mirreral usually have afair ly lour Pl with a high l iqrr id l inr i t and ir such cas;es l i rne should beconsidered for stabilization.

n In case of highly plastic soils, h,vo slage stabiiization is adopted. In this casesoil is first trealed with a sm;rllq lantity of linre. Later on lhr: soil may be treatedwith remaining quantity of lime orwilh cem()nt to achievo the desired strengihand stabitity.

3.12 Cetment stabilization

c Generally granular soils freer of frigh conct:nlralion of organic matter ordeleterious salts are suitable for r;t:nrent stabilizaliorr. For checking thesuilability of soils, it would be ;ldvanlageous lo keep the following crilerioninview:

a) Plasticity Product (PF'r, exprr.ssed as product of Pl of soil andpercentage fraction p,as,siing 7ti nnicrr:n sieve should not exceed 60.

b) Uniformity coefficienl of soil shr:uld bet greater th;an 5 and prelerabtygrealerlhan 10.

c) Highly micaceous soils are notsuitatlle for cement stabilization.

d) Soils that are having or$anic <:onlerrt lrigher than 2 percenl and alsothose soils having sulphate anJ r:arbonale concerrtralion greater than0.2 percent are nol suitat,le for cerment r:;tabilization.

e) Silty or fine sandy marterials may exhib it a high liquid limit because ofthe high surface area ol'the partrcles. -l'his

rnaterial generally will notreact with lime because of lar:h: of clery particles arrd can be stabilizedwilh cement. However, c€rmenl s;tabiliiz:rtion with hi,3h doses of cementmay tend to make stabilization unecono n'ical.

3.1.3 umelly ash (LF) and lime-cement-lty,ash (LC'F) sta',ricilization

Stabilization o1'coarse-grained soils having little cr no lirrers ciln often be accomplished by theuse of i-F or LCF combinations. Fly ash, also tenned r:oail as,h, is a mineral residual {rom the

IRC:SP:89-20.10

combustionofpulverisetlcoal. l tcontainsreactivesi| icaancalurriniunr<lrrmpoundsthat,whenmixedwi th l imeancjwarer , formahardenedcement i t ic r t tsm; ] | ;Sc€lpatb|eofobta in inghighcornpres;sive ,rrung,n".'t-ime and fty ash in combination can cflen bel t,**6 sucrlesslully in

stabilizing granular t"i"ti"it "in..

tn. fly ash acts as an aiQ€fit"ryith wfrich the lirne can react'

Thus LF or LCF stabilization is often appropriate for base and sub-base course nuterials'

3 .2Des i rab leProper t i eso fL ime ,Cemen tand |F |yAs t r | o rS tab | l i za t i on

3 .2 (a )ume:L ime ls i ; b road te rmwh ich i sused todesc r ib re { l a l c r i u r0ox ide (cao ) -Qu ickrime; catciunr rrydroxidJ 6"'to*1, - tr"k"o or hydrated line an'J calcium carbonate CaCot -

carbontrte of lime. rne retation n6tween these t'hree typ,es of lirne ciln be represented by the

following equations:

1) CaCO. r- heat

2) CaO'r-H.O

3) Ca (tlP11, * QO,

= CaO + CO,

= Ca (oH). + heat

= CaCO. + HrO

The| i f f i t react ionwhichisreversibledoesnotoccurmucl. tbelcr ' , r ,5009C)andisthebasis|or lhemanufacture of quicklinte from chalk or limestone. HyCmted lim': is prrc'duced as a resutt of the

reaction ol quicklime wfth water (equation 2). Quicklimer (by tl're reversal of equation 1) anc

hydratod linre (by equation 3) will both revert to calciunr cai'bonattl whicl'r is nol usecllor stabiliza-

tion' atthough it is used in agriculture as a soil additir];e tc ;adjus;t i:H.

ln dolc,mitic lime, some of the calcium is substituted by ntagnes;iurn' These types ol limes car

also br; used for stabilization. Hydraulic lime also l<nown as gre / lim,e i:r producecl lrom impure

forms of calcium carbonate whi*r abo contain clay. Tfrey, thereJc're, conl.ain less 'available lime'

i" i^iti.t* rtf*15 on ftasticity and strengith. Howev'sr, to con'penrsat'e for this, they contair

reactir,re silicales and aluminates similar to those found rn Porlletnd cerment' Thus, whilst their

immediate effect may be less than that <-ri high calciurn lirnes in lhe lonp term they may develog

higher strengths. Generally, use of dolomitic lime is nr:t ctlnsidet'ed suitirble'

Consequenly in the context ol lhis guidelines, lime slabilization rcfers 1:o the addition of calcitit

Jry linre, commercially available, stareo at site, or pre-:slaked lirne rlellvered at sile in suitablt

pa&inSi. Hydrated/Slaked lime comes in the form of a fiine dry powder

euicklime rs available either in granular form or as a prrwcler- It rc:t,tcls vir:lently with 32.p^ercent o

its own weight of water to prJduce considerable an'lotlnts r-rf heat (i:rpprox 17 x 10s Joule:

per kglof quicklime are released).

Hydrarted lime and quicklime are both usually added b scil in the ":olitl lrrrffI'l butthey may also bt

mixeclwitrr waler and added to the soil as sluny. The adveintar;es; and dir:;advantagr:s o{ the threr

methods of applicatiolt are summarised below:

n Dry ltydrated lime .h

a) Advantages:Can be applied two to thrr:,rr tirne:iitasterlhan slurry and ir

very effective in drYing out soils;.

I J

IRC:SP:89-2010

b) Disadvantages-. produces a dust problenr lhat make{,; it undesirable for

use in urban areas and the tast drying action of tl"rer lime requires an

excess amount of water during hot, dry weather

. Quicklime

a ) A d v a n t a g e s . . M o r e e c o n o m i c a | t h a n | r y c | r a t e c | | i n r e a s t c o n t i r i n sapproximalely 25 percent-more availatrle lime' Fir:;ler drying action

' than hydrated lime on wet suils'

b )D isadvantages :F ie |dhydra l ion is |esse f fe r : t i ve ,p r t :duc i r r rJacoarserrnateria.l with poorer distribution in soil nus;s, quir:klime requires nrore

water than does hydrated lime for stabilization, v'rhiich may present el

problem in dry area and greater vulnerabilily of sit': persorrnel to skirr

and eye bums.

. Slurry lime

a ) A d v a n t a g e s ; D u s t f r e e a p p | i c a t i o n i s | n o r e i { : , S i r a h r | e f r o n r a r tenvironmental standpoint; betterdistribution is achk;ved wilh the slurry;

spreading and sprinkling operation aLre combined, thurs redr;cinq

. p r o c e s s i n g c o s t s a n d d u r i n g h o t a n d r J r y w e a t h e r s | u r r y a p p l i c i a t i o n

pre-wets the soil and minimizes drying acilon'

b) Disadvantages;Application rales are sbw'er. High r:apacil'/ pumprs are

required to achieve acceptable applicatior rates; extril equipmernt is

requ i redandcos t is there foreh igher ;e ) t ran . lan ipu |a t ionmayberequired for drying purposes during cool, wel, humi<j vieather; nc't

practical for use wih very wet soils ai'rd if preparc! f;srrTl quiclilim':

any benefits arising f rom the heat ol. hyrlra,tion of quicklirnrl are largely

lost-

The purity of linre affects the strength of lime-soil stabilization. llte effectiveness of lirne in

reaction wilh its clay minerals is dependent to a good extenl orr its chemicral composition i'e''

amount of calcium oxide present in the lime. The purity of lime is exprressed a s lhrl prr:tcentage of

avatlable calciurn oxide present in the lime. lt is generally recomrn,snded thirt the lime used for

soilstabilization should have purity of 50 percent or above. The addition of lime should be

coneSprondingly increased whonever the field tests show a lesserr pruri$' Caiciurn oxide content

in lime should bt; delemtined as specified in lS 1514 or lS 712. Slerked lime suprplied in airtigltt

bags should nol be stored for more than three months. Since lime d{}teriorales wiliri storage lhe

purity nrust be checked at site before use.

For effective stabilization witfi l ime, unilorm mixing is a pre-requis'te and the: degree ol nrixing

depencls on the fineness of lime. When using line powdered lime, there 'nrill lce a quicli and

1 4

' IFIC:SF:89-2010

eftective reaction with glsry minerals to forrn cementitious compounds. Limel.fc,r stabilizittiorrshallconform to the fineness rr:quirement of class C hydrated lime as specified in lS 1 51 4 r:r lSi 7:l 2,

which is as underr flable 2):

Table 2 Requirement ol Fineness for Lime Stabilization

P'assingS.No Sieve Size (Micron) Percentage

1 ) 850 1 0 0

2) 300 99 (Minintt

3) 2 1 2 95 (Mini(Mininrum)

3.2 (b) Cement: Cement for cement ,slabilization should comply with tfre requireme,nb of

lS 269. 455 or 1489.

3.2 (c) FIy a:;h: Fly ash may be from anthracitic coal or lignitic coal. Fly aslh to be trsed for Lhepurpose.of soil-1lime-lly ash stabilizalion should conform to the requirement; given in Terbtr::3and 4.

tm)

Tlable 3 Ghemical Requirements for Fly Ash as a Pozzoll;rna

Sl . No. Characteristics RequirerFly

nents lor I ttllethoclAsh I of Tr:st

Anthraciticfly ash

Llgniricfly as;h

1 ) SiO.-r- AlrO., f:erO. in percent bymass, Min

I U 50 I l :S '1 i2 ,

2l SiO, in percenl by rnass, Min 35 25 | l:311'2-,7

e \ MgO in percerf by mass, Max 25 5.0 | t:3 t;'z;t

4) SO. in percent by mass, Max 2.75 3.5 | ilS 17'27

5) Available alkalies as NarO/KrOin percent by mass, Max

1 .5 1.5 I lts 4cl3i1

6) Total,chloridesi in percent by mass,Max

0.05 cr.0l5 . l i l i1 i '27

7) Loss on ignition in percenl by nass,Max

5.0 5.rl I lS 1i'27

1 6

IRC:SP:89-20'10

Table 4 Physicat Recluirement for Fly ltsh a$ a Pozzolona

prernrei:rbilitY

Requirement

250

, Max 40

3.5

ol spr:cimern in 0.8

in mrn, lVlax 1 0

3.3 Selection of Stabilizer .

The selection of the stabilizer is based on plasticily and piirlic,le :size distribution of the material

to be trealed.'rhe appropriate stabilizer can be selectr;cJacccrding to ther criterion shown in

Table 5. Some conlrot over the grading can be a:hievercl by lirniting ihe coetficient of uniformity

to a minimum value of 5; however, it should pnrierably be rnore than 10' ll the coefficient o{

uniforrnity lies below 5, the cost ol stabilization will be hrgfr and ll^re rnaintenarnce of cracks in the

finished road would be expensive. li the plasticitl of scil ir; high fiere are usually sutficient clay

minerals which can be readily stabilized with lime,. Cerrent is more ditficult to mix intimately with

plastic material buf this problem can be alleviat,ed by pn;'treraling:the soil with approximately

2 percent lime.

Soiil Properrties

More lhan 25olo Passing tl"re Lel;s

0.075 mm sieve

F l > : 2 0 P l < $ ,pp < rcO

than 25!/o passing the0-075 mrn sieve

Pl . : 10

Yes;

Ygs;

Two Stage Stabitization Using Lime {ollorred by Cement

Cernent can lre used to stabilize most ol thi3 s;oils. -t1te principal sx,3gptions are those that

contain ort;anic malter in a torm which retards 1.he lrydration 'cf cament and soils which are

1 a

NbYex;

Nln

3.4

Particles retained on 45 micron lS sieve:

Ljme reaclivitY in NVrnm'z, Min

Soundness by autoclave test expansicrtpercent, Max

Soundness by Lechatelier method-elxpanslol

Tabte 5 Guide to the Type of titahilization likely to be Effective

Type ofSlabilization

1o <Pl<20P t < 1 0

lF lC:SP:89-2O10

difficult to rnix with cement on account of their high clay contertrt' In competri:*on with cement' ihe

potential use {or lime in soil stabilization is more restricled; us'ed in equrivalerlt amotlnt il gendrally

produces lower slrenglhs than does cement and its main applicatiorr is for urse witlr cleryey soils

which are rjifficult to stabilize with cement. For these reasons lhe usr: rlf a two slager lime/cement

slabilization process appears attraclive as it otfers the possibility of externding the ran'ge of soil

which can be effectivety slabilized. To achieve the maxirrrurn effecl ilhe limr: and cement would

not be blended but would be added ssparately. Lime w,culd trrst ber added t'o modify the

properties of soil and this; would be followecl by the addition 'cf centr:rnt to hring out a long term

increase irr strength, when lime treated soil is slabilized *'15 1;s6€rrtl

3.5 Modification and Cementation

-l.here is a dislinction between a stabilized soil "modifierJ'' {or s'Libgracle impr'cvemenl and

,1:emented. (a cementerJ soil in this context can be ontl stiebilized with lime as the clay{ime

p,ozzolanic reaction products can be regarded as a cement) 'ior use' ;ls a' srlb-base or base' The

term "moditicaUon'. and cernenlation are used in speciticatitlns to oerscribe the degree and type

of lrealmelnt.

1-he rapicl action of lime on soil, which brings about a rerjrlctiotr irr plasticity and er marginal

increase in CBR is re{erred to as Modification. lf conditions; are fttvourable for the pozzolanic

,,"1ion to proceed, tire lime stabilized soil will develop significa rrt conrPt essivr: and ternsile strengths

and it is tlren regarded as a "cemented" material.

li a very S;rnall quantity of cement is added lo a soil, the propertiei rnay also be modified without

much hadenilg or the development of significantcomprerssi'te or le rttsil€r strength. ln such cases

lhe degr€re of r:ementalion is relatively poor, but the propertie,s of a trraleriar can nelvertheless be

r:onsiderirbly improved in this way. This trealmenl is arlstl refern:d to as modificalion in the

specifications.

rdy'hen a rnaterialhas developed sufficienttensile strength, il is reganlecj as a cemented matenal

5ut there is no cleady defined boundary between modificatron and tl'le clivision beniveen the lwo

is arbitrirry. However, it has been suggested (NAAtiR4 198€;) thal a7 day unconfined

r;ompressive strength of 0.8 N/mmz could be set as the bourrdary bertweler the two.

1 ' l

IRC:SP:B9-201(t

CHAPTER 4

SPECIFICATIONS AND TEST BEQUIREMENTS FOH SIAI]ILIZED MATERIALS

4.1 General Requirement

Tfrc pavement perrforntance of a stiabilized road will be largely govemed by ihe gradattion and thetype of s;oiligranular nraterial used for the purpose ot stabilizalion. 1-he quality of milterial to bestabiliz€rd should meet the minimum standard set out in specificatiorrs. Stabilized layersconstrur:ted from such malerial is likely to perform satisfactorilyr even il', it is affected bycafionalion during its life time. Materials which do not complywitlr lh€r requirements given in thespeciliciltions can be stabilized but more additive will be required ianrl the risk f ront cracking andcadronalion will increase. The strength of slabilized materials can lbe eryaluaterJ in ma,ny ways, olwhich the most popular are lhe Unconfined Compressive Strength (tj,3S) tr:sl ancl tlre CaliforniaBearing Ratio (Cl3R) test.

4.2 Stabllization with Cement

4.2.1 Requircmantforsoil modificatiordsuDgqadeimprovemerll

Cement stabilize(l materials can be used for soil modification or improven:ent of subgrade soil.It is recommenderd from economic consideration that mix in-place rnethorJs rlf construclion beused {or subgracie improvement and only granular materials and s lty cofrrlsivrl rnaterials beused. (The assurnption being that more clayey malerials would be rnore eff,ectirrely stabilizedwith limer). The main requirements for cement modilication or stabilization of subgrilde soil aresummarised in Table 6.

Table 6 Soil Characteristics for Cement Modified SilliUlmprroved

In case bettat m€ohanical oquipment lor spreading ot cemenl, tor breaking otods aod tfenclinr; is usod, themlnimum percanlage olcenlent for $tabilization could be 0.5 percenl. However extensivo lab tesling must bedone to atrive at this minimum prercentage. Sample at site of blended loose sol be collected arrd r"emoulded inlab to contirm lhal lhe desired CBR can be achieved.

IL!

Subgrade/Capping Layer

Properties-S"*ifEJ

Grtu;Liquid Limit (%) _ ---Plasticity lndex

--si--:---<2tJ

Organric conlent(/") <2:

TotalSiO. conlent 0.2 % Ma:rMinimum Laborratory CBR at specified density (%) 1 5Minimum cement content (%) tz"Degree of pulverisation ("/") >60Ternperrature fo r mixing l\ilorethan 1ffCllme for completing compaction 2 hrs lilax

1 8

lF;0:SP:89-20'10

4.22 Re,guireme,nt for bound sub-baseVbases

Granular materials, gravel, sand, lateritic soils, sandy silty material, crushed sllag' crrushed

concrete, brir:k metal and kankar, etc. stabilized with either cement or linre-fly ztsh-cr3rtent or

lime-fly ash, etc. may be allowed for use as capping layer over weak subgrade, as s,ub-lcase and

base layer of pavenrent. The main requirements of stabilized layers fcr differerrrt layets ol a

pavement structure as indicated above are sumnrarised in TableT and Il. The grtrdations indi-

cated in Tatrle I arr: inlended as tentative specilications. Gradarticrn fof cernent bound

materials as per MoFtTH specifications can also be adopted. Flowever, i:hickness ol different

slabilized layers, seler:tion/choice for acJoption of a padicular grading arrd strength requirements

of lhese layers are to lbe decided on the basis of pavement design and wilfl specific aSprtcval of

the Engineer-in-Char1;e.

Table 7 Matcrial Characteristics for Cement Modified Gr:rnular Matelrials

Speciliecl Value

<i!

4-3 Stabilization with Lime

4.3-1 Requirementforsoilmfiification/subgradeimprovement

The properlies of soil-lime mixes is usually assessed on the basis; of strength testr; made

on the materials al'ter the stabilizer has been allowed sutficient time to har,len. The

strength of stabilized soils can be evaluated in many ways, o, which the most popular is

Califomia Bearing Flatio (CBR) lest for lime stabilized soils. Lime stalrilization is generallyrecornmentJed to irnprove the subgrade soils which are cohersiv€, in nalure. l.irne isrecommended for such soils because ol rts beneficial effects on plarsticity', workability andstrength gain. The mrain requirernents for lime stabilized improved subgrirCe are sLrrnrnarised inthe Table 9-

sr"n:i"*:-]_:.--]<4,5 I- 3i -_-:-l<i!

._-_ -l

rt--_--__--4% (X the is vaiue is >296 the I

soundness te:;t slrall t:'tr Icarried oul r)n the materials I

1"*"*59i:ryi::'::L-J> 50ldl t

I___--J

Total SO" content ("1')

Water absc'rption of ':oarse aggregates

10 percent fines value when tested asper 8S812(l l l )

1 9

Grading lll Grading lVSieve size Grading I Gradiing ll

100 10075.0 mm

tlrl-l00 10053.0 mm 100

,{.5.0 mm s5-100

s5-90

95-10037.5 mm

l'0-100 55-7526.5 mm

ry4940€0

2.4 mm

11.2 mm3{i-65 3tg

4G659.5 mm 1 0-304.75 mnt 254Cr 25"55

15-3(l 2t::t-40 30-502.36 mnl

0.600 P1r:)-35 1*25

0.4251t B-22

0 3 0 0 u.&10. . Q:..10-.

0.075 Y 0-8 " -3-10,.- , .

7",14.5" 1.5'/0.75"7 days lJnconfined ComPressive

Strength (MPa) lor cement bound

materials or 28 days strength for lime-fly

ash & lirnecment-tly ash bound materials

12'16 J - l I , 3

IRC:SP:89-2010

Table B Gradation Requirernenl for Cemernt Bsund Materials for

Base/SuFbas€'s'/Capping LaYer

.. fi"ffi;:1[il1f":,xtilffi:mbe wilhirr rhe barch F,c,r Grirctins lv rhe unconfined compressive strensth

and CBR requirernent are equally acceptable alt'a natives

Table 9 Material Characte'ristic-q' lor li-inne/Moditied Soils

Value1m%

15 - 100%

2 1 0< 204

< 0.2o/"

Passinq 26.5 mm sieve -

c,onlirnt that the desired CBFI can be achieved'

,n

l l lC:SP:89-2010

Therquality ol linre shall be the same as given in Section 3'i2'

4,4 Slabitization with Llme Fly Ash (LF)

pulverised f uel ash (pFA) or fly ash has been recognised for rnany yeaus as ia valuable rnalerial

tor modifying anclenhancing lhe properties of soils. Stabili::aiion of collrse grained soils; having

liltlg or no fines can be accomplished by the use of LF or LCI: Combinartion. F:ly ash also termec

as r:oalash is a mineral res dual oblained from the cr:mbusliorr of thel prulverris;ed coal' lt contains

silir:on and aluminium compound which, after mixing with lirre and water lorms a hardenec

cementitious mass capable of obtaining high compressiiv(; strenglhs- Lime and fly' ash ir

cornbination can often be used successlully irr stabilizing granttlar materials since the ily asl'

provides an agent with which the lime can react. Thus LF or l-CF stabilization is ofter

appropriateforbaseandsrrb-basecoursematerials.Ftyas;hfti 'r i lr3eitherfromanthraciticcoa

or lignitic coal. Fly ash to be used in lime and tly asfr stabiliz:ation shall confomr to the

re<;uirements given in Table 3 and 4. Lime shall confornt to ttto requirement as given ir

Section 3.2.

-PS,qi.g-n-9f llng:fly glh 9!?9!!i199 Ti* i" somew_hat lifetenljSm :stabili:zation with lime o

cement. Fc,r.a given combination of malerials (aggregaie,lty riSfraiiit lim,a) li-nuintiei c,f faCtbircan be varir:d in the mix design process such as percentage of lime-fly ash, rnoisture content an(

th<l ratjo ol lime-tly ash. lt is generally recognised that enginerering cfiara,cterislics such as strengll

and durability are directly related to the quality ol the matri:x nr,aterial. -fhe

m,atrix rnaterial is tha

part, which consists of fly ash, lime and passing 1 0 mm aggrqgites firres. Bztsioally, higher strengtl

and improved clurability is achieved, when the matrix malerial is able to f ill the coarse a$gregat(

pa rticles. For each coarse aggregate material, there is a quanlity of rnatrix required to ellectivel'

fillthe available void spaces' The quantity of matrix require'c frlr malimum dry densityol the tote

mixture is rcferred to as the optimum {ines content. In LF mi}lure{i it is rracommended that'tht

- qr"rantity oi matrix be approximalely 2 percenl above the optintum fines conteni:. At tht

reoommended fines content, the strengh development's alsc' influr:ncrld by the ratio of ilme to f I'

as;h. Adjustment of the lime{ly ash ratio will yield ditferernt'ralues; of sttength and clurabilit '

properties. The mix design process is described below:

Step 1: ' 'fhe

lirst step is to determine lhe optimum fines ccntent that will give the rnaximun

dernsity. This is done by conducting a series of moirsture-density tests using rlifferen

perrcentaEes ot tly ash and dplermining the mix level that yields maxinnunr density. The initial fl'

as;h conterrt should be about 10 percent based on dry weight of the rrrix. lt is recommerrded tha

material larger than 20 mm be removed and the test conducl:ed on tlre. rninus 20 mm fraclion

Tersts are rr:n at increasing increments of ily ash, e.g. 2 peir,ce,rt, upto a'tot;al r:f about 20 percenl

Moisture rlensity tests should be conducted follouring pnlcedures irndicated in lS 2720

21

IBC:SP:8$'2010

part 7 or flart B. Tne design fly ash contenl is then 3elected at 2 percent al:rrve lhat yielding

maximum densitY.

Step 2: Determine the ratio of lirne to fly ash that lvil| yield highest slrengttr and j,,^:l']L.y.

Using the design fly aslr content and the optinum water content deterntined in step 1 ' prepare

triplicate slpecimen atlrrree different lime fly ash ratio' Llse LF ratios of 1:3' 1:4 and 1:5' ll desired

aboul 1 per cenl ol Portland cemenl may be added at this time'

Step 3: Conduct durab,ilitytest als perASTM D 559 and compare |he tesultt; o| the unconlined

r:ornpress1ve strent3th and dlrability tests with the requiremenls shorun irr Tablie i8' Tlhe lowest LF

ratio cont,enl, i.e., ratio with the lo.west lime content which rneets the required urrconfined

compressive sverrgth requirement and demonslrates the requirecldurability' is tlre rlesiEn LF

contenl. ll the mixliure meet the Ourafiitity requirements but not the stft)ngth requirement5' it is

considered to be il modified soil. lf the results o{ the specimens teslled do nol meet both the

strength and durerbilitv ,"qrit"."nts, a dilferent LF contenl ma'y tn selertled rcr additional

poriland r:ement ne used ano steps 2 to 4 repeated to ascertain strength arnd durability

requirements as per stipulated specilicalions'

Gradatio. Requirements for LF or LCF stabilization for stabilized sulr-bas'e 'trase:s rnay be as

indicated in Table 8.

4-5 Stabili::ation with Linre, Cement and Fly Ash

portland oemenr nray atso be used in combination with LF lor improverJ strengtlr and clurability' lf

it is desirerd lo incorporale cement into the mixture, the same pro@durers in'JiCnted for LF design

should be followed except lhar, beginning at step 2, the cement:;h:rll be include'd' Generally'

about 1 to 2 perc,ent cement is used. cement may be used in placr: of ttt ;n 26llJilirln to lime'

however, the totalfines content should be maintained' Strength and durability lesls must be

conducted on sampl; at various LCF ratios to delermine the r:ombinatiorr lhat gives best

results. G radation requirernents for LF or LcF stabilization {or stabilizeij sub-base/ba:ses should

be as indicated in Table B'

4.6 Cement Stabilized FIY Ash

This work shallconsist of laying and compacting a sub- base/basrl course of tly ash as treated

with cement on prepared subgrade/sub-base, in accordancei with requirements of the

specificalions. This technique ".n

o" adopted {or improvement of po<r subgrade ak;o' Fly Ash

to be used lor cernenl fly ash stabilization shall conform to Table i3 and 4 Pond ilsft or bottom

ash, which do notmeet t"he requirernents of Table 3 and 4 can also be use'l for cenrent stabiliza-

tion work. However, in all cases the cemeht stabilized lry ash/bottorn ash/pond ash mix should

develop zrdequater slrength'

The objectives of the mix design procedures, is to provide a pavemr:nt'nraterrial having the re'

quireO proportions of lly ash and cemenl to meet the following requirerrnetrls:

1) Provrde adequate strengrth and durability

zz.

IFC:{ l [ ' :89-2010

2\ Be easilv Placed ancl cornpacted

3) Be economical

Amount of cement less than 2 percenl is not gerierally amenable to proper mixing artd lrenr;e not

recommended.Af te rderc id ingcementandf ly " 'n "on tu t ' t fo r t r ia ln l i x rno is tu r 'edr :ns i tyrelationship has to ne dr:termined in accordance witfr lS 27?-0 (Part-7 or tl)' Tht: unconfined

compressive strength tes,t is clone on sarnples compacied at nraximumdrl'derrsity all'C optirnum

mois tu reconten t 'Themixpropor t ionshou|dbedes ignec | toobta inmin imur r ru r rconf inedcompressivestrengthoflT'5kg/cmzafterTdaysmoistcuringinahumidi\'chrrnberf<lrsamp|eswi tha |engrh tod iame| r : r ra t ioo f2 : l .Cur ingmaybecan ied ,ou t in l | re t r - 'mpera turerange30eC to 3BeC. The rJesigrt mix should not only inOicaie tne proportions ol fly ash anrJ '}0ment' bul

also mention quantity oi warerro be mixedand a specifiedcompacted densit'/ hat is; sequired to

satisty sPecif ied strength.

cement:cement con{orming to ts 269 or ls 8112 can be used' Portland pozzobra c:enlenl

shouldnotbeusedforstabi | izat ion,whenf|yashisusedasarr inetredienl.

waten water used ficr mixing and curing for stabilized mixes shall be clean arxl frere l'rom

. injurious amounts of oits, satt and acid etc. lt shall meet the reqr'tiremc:nt as lls 456'

Potable water is generally considered to be acceptable for stabilizatron r'vorks' The

permissib|e| imitsforso| idsinwatershou|dbeasgiveninTalr |er10.

Tablel0Permissib|eLimit forSol idinWaterforSoi|Stabl l izauort

Permissible Limit (Maxi rnum)

200 mg/litre

3000 mgllitre

400 mg/litre

2000 mg/litre,

Suspended maller 2000 mgilitrer

4.7 Test Requirements

4.7.1 lJnconfined compressive strength tesl

This test is carried oul on cylindrical or cubical specimens prepared by mr>ling the soil at il pre-

determined noisture content and stabilizer conient and compacting the nrixed matenial into a

rhould at either a pre-determined density or al a given cornpactive efforl" l-he choice of

specimen size and shape depends on lhe grading of tne soit; it is clearly desinilcte to keep

as smallas p,ossible the ratio of the nraximum paricles size to the snrallgst dinternsion of lhe

mould. The lfollowing sizes of Specimen for diflerenl group of matL'riiil are r8lsrnmended

fiable 11].

Sulphales (as SO)

a.)

Fine grained material

Medium grained maleria

Coarsegrained material

lFlC:SP:89-2010

Tabltt 11 Suggested Size of Mouldls fot Ca:sting Materials Samples

CyfinCti""r speci;ntens 100 mm frigh qnd 50 mm'diameter'

or 150 mm cubic rspecimens

Cylindricalspr:cinten3 100 mm high and 50 mm diameter'

or 150 mm cubic;sPecimcrns

1t;0 mm cubic sPr=cimeru;

Oompressive strength results on identical materials frcnr strrgngth tests on cubical specimens

wr:uld be higfrer than those obtained from cylindrir;al specrimens; and cylindricalspecimenswith

a FreighVdiarneter ratio of 2'.1; have lower stiength than cylincJrica.l specirnens with a heighU

diameter ratio of 1:'1. Allowance therefore f,aslt be miade forthiewherr comparing results

obtained with specimens of different shapes. For the relatil'el1t low Strengths encorlntered in

cement-stabilized soils the resulls on differerrt srzed lesl' spr-'cimens may be multipliect by the

conection factors given in Table 12 to calculiate lhe approximatelequirralent strength of a

150 mm cube. However, lhere is no unique rela'tion betw,3en lhrs strengths of sppcimens of lhe

two shapes as the ratio depends primarily on the levelof :;trength of the material'

4.72 Durability of stabi\zed materials

In ordertocheckthe durability of the slabilizeclni:x forsub'batse/base, the following two methods

are recommended. Method 1 is recommraflced, for nrocJerate temperature and climatic

*"j'i.^r,il;; method 2 is recommenced l,orthoser regioits where tl^ere is large variation

in ternperature and climatic condi[ons. The decision reganlingt the adoplion of a particular melhod

should be as directed by the Engineer-in-Charget'I

Mefrlod 1: Prepare two identical set (contiining 3 specimens each) of tJCs specimen which

are cured in a normalmanner a1c\-)tritantmoisture content forT days. Atthe end of

7 days period one set is immersecl in waterr rvhile lhe other s€rt is continued to cure

at constant moisture content. lVhe n both s'ets arr-' 14 days olcJ ihey are tesled for

ucs. The strength oJ the set imrnr:rsed in urlter as a percentage of the strength ot

Correction Factors for Varlor:s Sia: s nd Shape of Ter;t Specimens

150 mm'cube

100 mm cube

200 mm x 100 mm diameter rylirnd'ar'115.5 mm x 105 mm diamelercylincler

127 mmx 152 rnm diametercYlind'er

24

IRC:SP:89-2010

s€|tcuredatconstantmoisturecontentiscalculated. T'hisindex isa measureof theresistance to the effect of water on strenglh. tf this value is lovver than B0 percerl itis cpnsidered that lhe stabilizer content is low and its value shourld be increasr:d.

Method 2: Tlris test is done as perASTM sbndard No. ASTM D 559, lt is; generallyrknown asWetting and Drying test for dete'rmining durability ol stabili:zed soil mixes, wtrichdetermines the weight losses, moisture changes anclvolurne changes (swell andstrrinkage) produced by repeated wetting and dryinr; of l'rardened stabilized soilspecimens. The other is a freezing and thawing test wtrich follows: a sirrrilarprocedure except that wetting and drying is replaced by cy'cles of lreezing andthawing.

In the wetting and drying test, the test specimens are subjected lo 111r;ycles of wetting irnddrying,consist irrgofimmersioninwaterfor5hoursfol lowedbyrJry' ingatl ' ' l0Cfor42hours'Aftereach cycle lhe s;pecimens are brushed in a standardised manner vrith a tryine screttch brush (18-

20 strokes on the sides and 4 strokes at each end). The loss in weir;ht of ttro brushed specimelns,after each cyck; are determined. In a parallel tesl the volume ilnd moisturtl changes of thespecimens after each cycle is recorded.

The freezing an,d thawing test is similar to the wetting and drying test but lttr: test crlcles consist ofsubjecting the i;pecimens to freezing conditions at -234C for 124 frours followed by thawing at21eC for 23/24 hours. The specimens are brushed, as in the w,etting and clryirrg test, after eachthawing ryde. F:orclimatic conditions prevailing in India, durabilily under welting arrd drying wouldhave to be taken into consideration and durability underfreezelthavrr conditircn cloers not generallyapply.

The principal criterion set by lhe PCA is that the loss in weight ,of ltte specimens afler 1 2 cy,3ls3of both freezing & thawing and wetling and drying should not excesJ certerin limrits, dependinl; onsoil type. Granular soils ol low plasticity are permitted to lose up to 14 percont of their origiinalmass and cohersive clay soils are permitled to lose only 7 percent ol their original mass. Thereason of the difference is thal granular materials abrade morel readily lha,n cr:hrxive soils andthe wire brushing rernoves some material irr addition to that looserred by lhe altemate cycles offreez-ing and thiawing and wetting and dryirrg. However, as per s,rme othbr shtdies, the aboverequirements were found lo be too stringent and lollowing values have ber:rn relcommended:

Base: Less than 20 percenl

Sub-base: Less; than 30 percent

Shoulder: Lessthan 30 percent

25

IRC:SP:89-2010

CHAPTER 5

CONSTRUCTION OPEHATIOI{S

5.1 Frrocedure of Stabilization

The construciion of stabilized road pavement layers follow the siame L'asic procedures whether

the sfabilizirng agent is cernenl, lime or other hydouti. binde r. -f :le pr''x'6ures can be divi'Ced in

to two main groups:

1) $Iix-in-Place slabilization

2) Plant-mix stabilization

5.2 lJlix-in-Place Stabilizltion

The rnain advantage of the mix-in-place procedure is its relative s,irnplicit/ and henc;e- it is

particularly suitablelor work in remote areas where ptant rnixirrg could prrove logistically difflcr:lt'

Its disadvarntages are nol obtaining efficient mixing i.e. good distrfbution ol the stabilizer,

constructing thicknesses ol more than 200 mm and ol poor levr:ls.

In this process the material is stabilized in-silu which requires tne slabilizing agent to be spread

before or during the pulverisation and mixing of the soil an,C st.abilizer. Tltis isi generally r:anied

out with a purpose made machlne althougti for small scale work in rcmc'te areas agricultural

machinery can be adapted for use. In-situ slabilization -r;,:nerzlll '7 inrrohres lhe following

operations:

Initial Preparation

This involvrrs excavating ctown to the in-situ materialto be slabilized or placing imported nrateriaj

on the forrnation. The material to be stabilized then has to lre gracled to approximately lhe

required levels. After which il is usually necessary 1o plougth to looserl the material' one or two

passes is rormallY sufficient.

Spreading the Stabilizer

Spreading rhe stabilizing agent at the required dosage rale can be ci;rnied out manually or by

machine. lVhen manual rnethods are used bags of slabilizer €rre spotl,ed irt at sel spacang, they

are then br,lken open and the stabilizer raked acres the surfatxl as unif rrnnly;s possible. Where

quicklime irs being used, necessary precaution need to be trakr:n to prorcct lher operators' This is

especially,lrue rvhen the stabilizer is being spread by manual rxethod.

Lime has a muCh lowerbulk density than cement and it is p'Cs;rble, lherefore, to achieve a rnor€

uniform dislribution with limewhen stabilizers are spread manually.Tho uniformityof the layerof

slabi izer spread over the surface, before the mixing operaliiorr, delernrines the uniformiiy ol the

mixed mat,3rial OrOduced.

26

lR0:SP:B9-i t0l0

Mechanica| spreaders llutomaticai|y monitor the required amount of stabi|i:zer to belspread on

the surface o| the soi|' rn"i, ,," results in a much rnore uniform spread rrt stabilizer crver the

surface lhan can o" u"'.,,"iui[i n-ono ,pr"uuin!. rne eqrinlelt nged lo tre calilrralecl before

use to ensure that the ,;;;;;i ,,i, oiipitto is alhieved and subsequentlv checfred at rer,ular

intervalsto ensure tnu,in"iuiu of spread remains within specified toleranc;es'

Addition of Water

lf it is necessary t' add waterio bring the moisture \$ntent to the requirecl value this can either be

done as part of rhe mixing operation.orStlg,r tF malerial has been preparecl prior to the addition

of lhe stabiliz"r. to ensrrE airrorougn oistriolriln J'the added water' if is; prerferabkl to a'cd waler

as part of the rnixing operation".Walglid::,J"ing the mixinq process r;hould b9 through a

spray system zucfr tni it is add^ed ln 1

u{orm ,;'unnu,, oveii the required ar€:zr and rnixecl

uniformlytolnerequ|reddepth.Wheretremixingplanldoesnrl ienable\vatertObeaddedorwhere it is not pgssibt,a to add enough

""6r orriii*i"ing it sl,':rrld br: aclded to the prepared

material using a spray system that enables the;oint to bi cotrtrolled r:vt." the wfnle are;a' The

mareriarto be stabirize,d shourd rhen be mixed ;;;;i;il;diti,in ol the s'tabilizer to erlsLrre lhe

Oi"t inution of lhtl waterr throughoul the layer'

Mixing Soil, Water and Stabifizer i

RobustmixingequipnlentO{suilab|epowertorthe|ayerbeingp,rocessedis;requirtx!topulverlsethe soil and blend it vriin ttre stabilizer anO *at"r. ine tnostliticienl ol tlr'a machines available

carry out the operarion-in un"pu*, enanfing th; layer to be compaclexJ quickly and nrinimislng

the loss o{ density arrd slrenglh caused uv unv o"ruv in compaction' Mu'fti pass rnachirres are

satislactory, prrrvided the length of p"u"rnrit u"[ig pr*"ssed is not excessive 'and ear:h

;;;"t ;;vemenl can be pricessed within an acceplable time'

The plasticily of the rnaterial is overriding factor in the ability of mixing plant to rnix the soil with

stabilizer. A review orwoi* snowed that tll pruJi" *ir "outO'ne

satisfact.dly mixed with r:ement

using the plant. For conesiue soils a tu"to,. orinn plasticity index of the soil multiplied by the

percentage of the f rar:tion of the soil wrricn wal tinet ttun +2'5 micron irr p;article dra meler may Lle

used to suggest tne vatues forthe ditferent ifpes of mixing planl avarilatrle' whrch are l]iven In

Table 13.

Table 13 Soil PlasticitYLimits for Srabilization Using Different Types of.l'lant

Type of Plant' PlasticitY Inder x Percentag€

ol fraction finer than425 micron

Nonnal rnaxicapabll€' ot Iin one layerr 20 -1 e'0

1 5 0

200-3$ ( de

fpel and hot

Agricultural Disc harrows'Disc Ploughs' rolavators

Less han 1000

f-ighiOrtY rotiavatons (< 100 hP) Less lhan 2000

Hearry dutY rotavat()rs(> 100 hp)

Less than 3500

selection of the apt)roprhre planl shoutd be lelt lo tre decisiorr o{ the Engineer-irr-charge'

imrunr draPth (mm)beinE Processed

, deperrCiryl on soilhorsernwetr of mixer)

27

IBC:SP:89-2010

Graders have been use<J to mix stabilized rmerlerial br.rt they are inefficient for pulverising

cohesive soil and even wilh granular malerials a large number of passes are needed be{ore

the qua|ity of mixing is acceptaote. For thes;e reasons, th€r use o| gradr:r for mixing is not

suggested.

ComPaction

Compaclion is carried oul in two stages:

An initial rolling and trimming rvhich may be carried out followed by a final

mixing pass of the rotovalor.

Final compaction and levelling in the ca:se of cement stabilized material, must

be completed within two hours of mixirrg. Delay in lime s;labitization are less

critical and for soil modiiicaliort therer'{nay even be beneiits in completing the

final mixing, levelling and compraction bretvl'een one and seven days after the

inilial mixing. This trme gap allows {or th'e reactions between the lime and clay

to take plac.e and lhus provide a nlore workable soil' However' for lime

stabilization as distinct lrom rnodification, llne aim should be to complete

compaction within three hours after rnixing lime with soil. This is particularly

true in hot climates where problerns of evapotalion and carbonation are more

| i k e | y t o o c c u r ' | n c a s e o l c e n r e n t s t a b i | i z : a t i o n , t h i s t i n r e p e r i o d s h o u l d b ereduced to hlro hours.

Curing

Proper curing is very important for three reasons:

a) lt ensures that sufficienl water is rcrtrlinecl in the layer :;o that the hydration

reactionsbetweenthestabi|izelr,wal€lrai"|clthesoi|cancontinue

- b) - ll reduces shrinkage, and

c) 11 reduces the risk of carbonation fronrlhe top layer'

ln temperate clirnate curing presenis few prob'lems' ll is usually carried out by sealing the

compacted surface to prevenl escape of wetter durirrg the r:udng period (usually seven days)

during wh'rch time ail construction tra{fic must ber kept ollthe stabilized material' Before spraying

is starled the surtace should be swept free oi loose material raniJ any damp areas should be free

ol standing water. The following methods olcuring are suggesled:

a ) c o v e r i n g w i t h a n i m p e r m e a b , | e s h e € ) t i n g v u i t h j o i n t s o v e r l a p p i n g a l I e a s t .300 mm and sel to prevent inr3ress 'c{ tvatelr'

b) spraying with a bituminous sea ling contpound'

d t

b)

2ttl

t l lC:SP:89-2010

c)spray ingwi thares inbaseda luminouEcur ingcompounds imi la r to thoseusedtorconJrete. This has particularapplication whtlre it ir; <lesirable to reduce the

increase in temperature immediately underlhe s'urfdcer lvhich'would resultfrorn

ttre use ot a black (bituminous) seal'

ln a hot dry clirrate, ths ngs{ for good curing is most important but the prevenlion of moisture loss

is very diflicult. lf the surface is bnstanily sprayed and kept darnp day ancl night the moisture

content in the main po,-,io,. o| the layer will remain "136tg

brut |he o1:.arrati<ln is |ike|y to leach

stabilizerlromthetoppo,tionofttretayer.l.fthespmyingoperirlionisintr:tmittenltandthesurfacedries frgm tinne to time (a common occurrence I tnis metrgd is r'sed) the curing lvill be

crmpletelY inrrffective.

Curirrg lhrough spraying water can be much more etficient if a riayer of sarrd 30 mm lo zl0 mm

thick is first sp,rearJ on top o{ the layer. ln this case, ills nurnberr Ql spraying cycles per day can be

very murch le:;s and there is a considerab|e saving in the amoui.i o| wa.ielr used.

Whenthesrabi|izedlayerisrobecoveredbyotherpavement|ayrlrsthr:cons;tn:ctionolthetuppersectlons will rprovide a very good curing seal but care has to brtl taken 10 ensure that this work

doe:s not damage the lop of the stabilized layer. During the perrod of time prior to the

coru;truction of thB next layer some system of curing is requinecl.becau:;{9, tl-ris is thg mct critical

peri,rd in terrns of shrinkage in the layer'

Primer can a.lSo Serve as a curing membrane but, results have shown llhat a prime coat breaks

downwhenitpenetralesintothesurface'andcompletelylorse:sanyab' i t i tytoseal i t -Aport ionofany curing rnemDrane must sit on the Surface lo achieve' arr effectir/e :;eill if the top of the

statliliz.ed la,yer is sprayed lightly with water followed by an application of 'a viscous t;utback

bitumen, the loss of moisture is effectively reduced to zero' similarly tre top of the stabiliT]:d layer

can be spnayed with an emursion to achieve the same resurt. r*s esse.ti*r, however, ihat ajltraffa

is kept off the curing mentbrane for several days at which tinre €)xcess lriturnen can be absorbed

by the sudace.

5.3 Plant-Mix Stabilization

Inthisprocerss' themater ia|sareseparate|ybarchedandmixelr latarnixingp:Iant.Theyl l relhentransportecl to the sile where they are laid by a bituminous pav'3r ancl compacted' The

ad,rarrtages; ol lhe process are the gooct conrroion proportiorring of lhe materials' multi-layer

work can bB sxecuted and good compacted levels are readily oblainrablel""lhe disadvantages

are that oUtput is tower fhan in the mix in place process, c'lhesive mar'lerials; cannot usually be

mi;<ed and rn the case of cement stabilization, the mixing plant has to be relatively clo:;e to the

sitr: so that mixing, laying and compaction can all be completed within the stipulated two-hour

tinre limit. -l-he process is nol' lherelore, applicable to srnal;l-scale p'rojercts unless lhere is a

mixing Plart near at hand'

To ensure (:omplete clislribution of the relatively small quantities of st'abilizer' mixing should be

carried out in a lorced action mixer and except lor non-c;ol'resive granular rnaterials, free lall

29

IRC:SP:89'2010

mi*"_. of tn" ryp" r.rsecl ior miiing concrbte sf,ould not be used. tt it is proposed tc' iitie a mii6r

other than one witlr a forced action preliminary trials should be macle 10 ensure that satisfactory

mixing is achievecl.

Vehicles transporling the mixed material shor.rtd be of sufficient nr':nrtrer and capacity to meet

bolh the ouput ol the rnixer and spreading and compaciion operations'. lnternational standards

and specificationr;, for plant mixed cement stabilized material require it to ie spread' by a

biluminous paver and spreading by grader is not permitted. lf gra'den; aie ustld frlr spreading'

much oithe advantage of plant-.mix stabilization is lost as it is 6ilficuh to crrntrol levels and

thicknesses of construclion'

5.4 ComP:rctlon

whalevermethod is ursed formixing the soilwith water and stahilizerrnaterial' the rnellhods used

ti "orpu6ton

are thrt same. ln the case of cement stabilized matedals, onc'e the.cemenl has

begun t0 harden, it is; important that the matrix is not disturM; hence'th'a requir'ernent that

compaction musl be completed wilhin two hours o{ mixing' The r:omper:ted rlerrsity ol the

stabilized layer is a measure Of the etfectiYeness of compaction and fience ol its strenglh' The

degree of mmpaclion to be achieved in lhe tield can be specified irr tlvo ways;' ln an ernd product

speciticatior-r, the density of lhe layer'in the field is delermined and. compared with a specified

target density. Prr:vioedihat the measured field density is greater lharn or etlual to tlnis limit the

compaction in therfietrj is deemed to be satisf actory The main disadvilntages o{ an ernd product

specification are lihat a large amount of site testing is required and nt;any ol ljre nretlrods in use

are time conSuming. This means that the results of the tesls may rrot be a'ailabl|a in time to

remedy any deficiencies in compaction'

30

lF lC:SP:8l t -2t110

CI-SAPTER 6

OUAUTY ASSURANCE

6.1 Gen,eral

During the construction process regular checks are lo be made on the' stabilizerj rmaferiirl to

ensure thal all the requiremr:nts of the specificalion are being met' ManV o115e sh6rr;ks carried

out are merely'good housekeeping" i.e. continual supeMsion to ensur's tlnat lho corstruclion

process allows the design ot4ectives to Oe achieved in full' ln addition to tlris tlrere are prorCuction

control'tesls ceuried oui'to nionitor the work in progress to ensure, for examllle, lh;rt lhe comect

thickness of slabilized layer is being laid and tr"t ".on.istent

produci is bei'ng piodur:ed' Firnally

compliance te$ts are to ne carried Jut on rhe finished product to demonstrale, that it nleets all the

requirements of the specification'

This Chapter, theretorer, desbribes the tests that may need to be cani'ad tlut tO u-hecl'l olt the

quality of the material. tt ;rlso discusses the various factors that inlluence the r:hoice of a

particular test thal is used to establish lhe values for paramdterS suctt zr:s moistilre contenl'

compacled density, strenglin, etc., sel oul in the specification'

6.2 Preliminary Trial

As part of ther quality r;onlrol and in order to make a final decision orr nroisture conlent and

stabilizer cont,ent, the infomration gained in the laboratory tests should bet rerlated lo a[prerlirnrinary

field trial. Al krast 10 clays before tne main work begins, a trial area shor'ld be laid using the

materials, mix propol[ionsi, mixing, laying and compaction planl to be used, tr'l chreck the

suitabilitY of the rnethoJs, ertc.

6.3 Sampling ernd Testing Frequency

Samples lor clhecking llhe rnoisture contenl, strenqlh, etc' are most conveniently trl<en from the

laid material hrefore compa,ction. Frequency of tesing depends on the size of the pn{ect "n9

tl:

facilities available on site but regular checks should, al least, be made on llre moislure content;

strength and in-situ density whatever the trequency, sampling should btl sp:iead ourl owr the site

so as to give a representative indication of lhe quality ol the material within a given a rea' ln order

to achieve the sp*ificltion for stabilized sub-bases and road bases, it is suggestecl lhat sarnples

at equally spetced locationb along a diagonal that bisects the area to be leshld may tn k&en' For

satisfactory perlormancec,l soil stabilized road, strictquality control measures am €'Ss€ntial' ltis

prudentto conduct periodir: testing dr:ring Construclion to confirm that tf]le propertie:s of lnaterials

being used are within the range of value anticipated during the design' i:or 'each ctrrsignmenl of

cement, lime and fly ash; tesilng shor:ld be done to check quality. Quality c:onlrol te:sts anrl their

minimum der:irable frequerncy are a:i given in Table 14. Strict control should be erCistf rJuring

31

tRrl:sP:89-2010

thc! mlx inalace operations, with frequent checl(s on mixing efficiency' Tttis can be done by

trenching through the in-place rnaterial and inspet;ting the colour of the mixture' Unmixed streaks

or layers indicate poor mixing and the material in thi a'ea shoul'd be remixed until uniformity ol

colour is achieved.

Table 14 Quality Control Tes'ts {or Cerment-Fly Ash and

Lime-fly Ash Iilabiliailion

6.4 Storage and Handling of the Statrilizer

Llnless cernent and lime are properly stored and used in a fresh condition the quality o{ the

pavgment layer \^/.ill be substantially reduced. cemenl murst lf,e stored in.a sound water-tight

building and the bags stacked as tightly as poss;ible Doors arnd windows sihould anly be opened

il absolutely necessary. The cement which is <Jelivered tirst should be usr:d firsl- According 1o a

Mi;nirn um Drx;ired Frequency -----.--

Orrce inilially for approval ol the source of supply.^.t l,tto, r.rr r,r,ch consiqnmenl cl the matedal

Test Test Method

OualitY of(kntent

As per relevantlS Specifications

Oncer initially f,or approval of the source of su;ply

and l;ater fol (lach consignment of the material

subitnt to nrirtimum 'cf 1 test per 5 tonnes ot ttme

Orce initiatly for selerction'of the source of supply

arrd hter{ort:acfr lot of 10,000 kg

OualitY ol lime l s 1514

QualilY of l=lYAsh

rs 3812

Pr:riorJically a.s considered necessary

One test Per 1150 sq.m

One lest Per li00 sq.rn

A:s rr:quired

1 ter;l Per 30(:10 ciunrof mix

Fegr.lartY

Fegrrlarly througlr procedural c;hecks

Degree olpulverisation

lSn20 (Part-4)

Moisture content lS2720 (Part-2)

DensitY oloompacled layer

|s2720{Part-28 or 29)

Deleteriousconstituents

tS2720 (Part-Z7)

CBR orunconfinedcompressivestrength test onase to f3'specimensi

ts2720(Part-16)ls 4332(Parl-5)

'fhickness oflayer

LimdCementconlent

3i2

;s

study it was tc,und that even if cement isstilloccut:

properly. stored ther following

l f lC:SP:89-2O10

losser; in strength will

Aget Percentage Beduction

After3 months

After6 months

Afterl year

After 2 y,ears

Lime should b,e stored in sealed bags, liglrtly stacked and covered wilh er warter pro0f tarpaulin.

The nraterial vyhich has been stored for more than lhree weerki shorild be lested for availablelime content before use. Lime which is older lhan 6 months should be rjis;carde'd.

6.5 Control of the Moisture Content

Thror-rghoutthe stabilization work, the moisture content should tle merintrainelcl:slightly abcrve its

speciriied valur:. Tlris means that rapid determination of the in-sitr: moisl.ure content is necessary

to all6w adjustments to be made so as to bring the moisture conllnl oi tlre stabilized materialto

the required value.

The cefinitive ovendrying method is, in general, too lime-con:;urring to be of rnuch practic,al usein the lield and more rapid rneans have to be employed- Rapid l";eertirrg rnethods may be used,bul where th$e are inappropriate, the calcium carbide method rnay btl used to give rapid result.

The rnethod rJepends on the reaction belween calcium carbicle an<i'water in the stallilizedmaterial to produce acetylene at the ambienttemperature acr:ording to tlhe elqttation:

CaC. + 2Hp = Q2 (OH), + C.H,

lf the reaction is allowed to occur under standardised conrjitions in a closed containerr, the

pressiure ol the acetylene generated in lhe container is a measun] ol the moisture content of thestabilized malerial

Nuclear density elauges for the determination of the in-situ density ofcompacted materials

usually include a liaciliq, for the in-situ moisture conlent at the siame linre. T'his melhod can beused to delennine, moislure conlent when construction starts ancl alsc during the processing.

6.6 Contrcil of the Slabilizer Corrtent

Whalever mgthod of spreading the stabilizer is employed, it is inrporturrt thttt et uni{orm srpread

rale irs achieved ar: this will affect the uniformity ol the slabilizetl nialeria!. tf ther slabilizer is prlaced

in bags and sprea.d by hand, the accuracy of ihe spolting of tlre bags rrrusl be ,:hecked and the

manual spreading of the stabilizer should be visually assesis€d. lf a mechanical spreader is

used, metal lrays or canvas sheets, one melre square, shoulcJ be placed at regular intr:rvals

along the roa,J to checkthe application rate.

2A

30

40

50

33

IBC:SP:8!)-2010

Detenninalion o{ thra st€tbilizer contenl' afler mixing' is in principle easy hr perfotrn but in practice

is 1me corsuming and needs to be carried out witi care if meaningfrrl rr;sults are' to be 'rbtained'

B d t h t h e m e t h o d s d e s c r i b e d i n l h e c o d e s B s : 1 9 2 4 : P a r t 2 a n d i n l r S T M D S 0 6 i n v o | v e acomparisc n of the calcit.tm conlents of lhe stabilized material' the stabilizer and the material in an

un_stabilized condilion. However, the method given for the determinaticn of c;tlc;ium in BS:1924

is to be preferrecl. Nehher methrrd is applicabre if the calcium cont'3nt of lite un-:stabilized

lnaterials is high orvariable'

6-7 Routiner Strength Delerminations

Continuotts monitrrrinl; o| the strength of processed materia| is required to ens;urr] that the

specified strength is oe,ing achieved. Representative samples of the fr"rlldeplh crl m'ixed material

should lhrlrefore ue tat<en from the site immediately prior to cornpacling the material' As stated

previousl'6 the lrequerLf ol sanrpling should ue rehred to the size of the processed airea and its

structura imporrance. in lrre case of cement stabilized materials, preparation clf the test

.poi*"r,, shouH be r:ompleted within two hours of mixing'

The moisture conlenl ro be used Jor the preparation ol the test speclrrens will clearllr be that of

themixe(Jmater ia|andprecarrt ionsshou|dbetakentoensurel l ia. lnodryingcrulo,f t | remater ialoccurs between tzrking lhe samples and completing the preparaticn ot'the tasl specirmens'

T h e d e n s i t y a t u r h i c h t h e t e s l s p e c i m e n s a r e t o b e c o m p a c t e d d e p e n t l L ; o n t t r e d e n s i t yrequirerr|enls o| the specificatiorr and various methods which are irr use'

.T,r.e test :;pecimens

should be preparr# u,.h" .u** density as lhe compacted materia| in the lk:|,d. l.his has some

logic because it mean:s that there should be no differences in strength' which r>'rn be a'ttributed to

differences of derrsity, between lhe laboratory iest specimens and the strengtfr o{ the material in

the field. The di{ficulty islhat an inrmediate measure of the in-situ den:sity is required and this can

only be erchieved if nuclear density gauges are used'

34

IRC:l l?:139-210l0

CHAPTEB 7

PRECAUNONSTOBETAKENWHILEU$INGSTASTUZEDMA:I 'ERIALS;

7.1 General

The two maior probtems that arise wilh the use ol stabilizecl materials in roacl pavenrr:n1 layers

are cracking anclthe longl -tern durabili\r otthe material' -fhe extent to whicfr eilher ol lhese is a

problem is intirrrately ret,ated to the puryose of the stabilized layer in tlrer tuld pavement as a

whole and it is', rhere{ori,e, c|ifiicull lo divorce the two lactors. l{owever, in this ()hapter the

problems that can arise are rliscussed'

7.2 Cracking in Stabitized LaYers

Many laclors contr ibute to the crackinq and crack -spacing of st:abilized pavement la)'ers some

of them are lisled below:

1) -fensile strength of lhe stabilized material;

2\ Shrlnl<ager characteristics;

3) Volunte changes resulling lrom temperalure or moisture vanaticrn$;

4) The subgrade restraint;

5) Stif(ness rand creep of the stabilized material' and

6) Extemal loadings such as those caused by tra{fic'

As in the s356' ol comp'ressiive strength' the tensile sirengttr of stabilized nraterials tirkes time to

deve|op.ontheotherhanc]l,stabi|izerJmateria|inaroadpavemenllayerwi|lbesubimtklvtl|ume

changes from al least oner of the lactors listed above as soon as it is conrpacted' crack:ing in

stabilized layerrs due tc,changes in terrrpaature or moisture content cannot' therefori)' ber arroided

and must be acceprecl as inevitable although steps can be taken to reclucxr lhe efftrt' rlrcrcking

rnay also ocrlur as a resull ol latigue tailure due 1o tratficking and is an entirely sel)arate

phenomenon, from ther initial cracking due to environmental changes-

Cracks in stabilized letyer:; used at capping and sub'base levelare unXit(ely lo cause significant

oroblems bult at base lev€'l the cracks rnay be rellected through lhe surfac:ing' -ftttl existernce ol

aq

lR0:SP:89'2010

cracks in a road surface may be assumed to incjica'te ner:d lor remedial action' The

coi l ' rsequencesolnotdoingso,mayrangef 'on, ' 'no.otol :nl t - : la l l . to lossof inter lockorto'

eventualfailure when lhe stabilized layer has bee'rl reducerC fo unconnected lrlocks' Cracks may

ak;opermit ingresso|water|eadingtoweathel ingofmater ialsatcrack|aces,de.bondingb€,tween pavement layers, or deterioratiorn oJ moistttre-:3ul;ceptible liryers beneath the

stabilized laYer'

7.,3 Primary Cracking

Cracks appear in cernent-stabilized materials as a n::sult crf shrinkage and temperalure

fluctuations, The ini'alcrack pattern is deperdenl on the,early strength o{ the material and the

properties of the malerial used. Materials which trave low :;trength' normally also contain a higher

proportion ol plastic fines. The stabilized rnateria'ls with lower sl renglh and with high proportion

oi plaslic fines have frequent bul narrow crar:ks' whehr:rr or not these lrequent but line cracks

provetobeaprob lemdependstoa |argeex len ton themechan ica | in le rk rcka t the taceo{ the .

cracks.l'theinter|oc*isgoodthemateriaipr-'r|rrrmssatisfac;totyandthecracksaresuflicient|y

fine{orlhem notto be reflected through the pavetlent leyer abo',re. However, the lowet strengths

o,f these stabilDed materials mean that they are elenerally only suilable for rJse in the lower layers

c,f the road where cracking is less of a problem anywa)r'

on the ofier hand, slabilized materials with hig;h strefl{ilh r:riteria and wltich have little' if any'

prlastic fines have fewer but wide cracks. ttres': cracks; arel oliten wide enough lor them 1o be

reflected through the surface. In order to reslrain the propraryrtion ol lateral rcflective cracks' such

rnaledals theretore have to be covered with a l3reater thicl(ness of construction material than

lvould otherwise be required'

-the temperature ar which the material is lairl also plays:r part in the type i:f crack pattern that is

producod. Layers placed in cooler weather IerL(l to deverlop fewer and narrower cracks as lhere

js less lhermalshr inkage.Thestab i l i zed layermaysubsequent lybe incompress ion 'apar l

perhaps from protongeJcotd spells, so that {:rac;ks remafin closed wilh go.d load transfer' Fewer

r:racks develop when the temperature dilference between day and nighl during construction is

not large, as thermalwarping is reduced'

rd to cracking I'or the same reasons' However' meLjme- stabilized materials are also subiectt

effects are not so pronounced; if the cracks occur before unreacted lime in the,layer h^as been

used up, either in pozzolanic reaclions or by cerrbonatit:n' lhe continuing pozzolanic reaction of

the |ime can result in se|f - healing (autogen,cus lrea|ing ) of thr: cracks.

.to

IRC:SP:89-2010

Givern that cracking is inevitable, the ideal cOndition is {or nral,errials io have low early s'trength

which lead to numerous fine cracks bul high long- term strerrgtihs whir:h merar good mecl'lanical

inlerlock atilre face of the c,nacks. As lime is slower to react than cernent, llris is another reason

for fravouring lime, provided it can achieve high long- term strenl3lhs'

Another pos:sibility is to use secondary addillves to modify tfre h ardening action oi the cernent to

reduce its eerrly s,trength without aflecting its long-term strength.

7-4 Ttaffic Associated Cracks

Quite separ,ately and much more importantly than the printall'lran:;vrgrse cracks, cracks may

spp,ear in stabilized base:; of inadequate strength or inadsluate r:onstruclion thickness in

rela.tion to the tr;r{fic and ther sub-grade strenEh- Such crack.ing takes the fornl of 'map" cracking

which, in exlreme cases, uruses the stabilized materialto cleleriorate into snrall slabs with poor

loa,J transfer. Once started, deterioration is likely to continue until the :3tabilized base b'3comes

tittle more elfective than granular sub-base.

When extensive cracking has developed as a result of the combinerd acltiorr of lree waler and

tralfic, then it often results in the "pumping" to the surface of line merierietl f rom the underlying

pavement hayerc where it is deposited in the cracks' The fines discolour the surface along the

cracks making lhem clearl'/ visible-

Unlike the primarycracking, the appearance of lraffic-associatsj cracks is not inevitable' lt should

not occur if the road paventent has been properly designed lo isks account ol the lraffic likely to

be encountered during the design life of the road'

7.a; Durability of Stabilized Materials

The failure of stiabilized mirterials by disinlegralion into a |lorse mas;s is not common. lt is most

likely to be due to deficaency either in the amount of stabilizerr, delit;ienc;y in the quality ol lhe

st€bilizer, or deificient compaction or curing. These problems s;hould not occu r if a good :;tandard

of preliminary tr:sting for suitability anc of quality control are nnaintainerd'

It is repoded.th6t the most common type of lailure of stabiliz.ecl.layen; rs; tlrc pr:eling-ofl of surfac€

dressings f ronr stabilized liayers. This ir; usually due to failure of top c,f the layers itself ralher than

any of the,sho1coming of the surface dressing. The sudace of ther layer ternds to disintegrate

under traff i,c, the most likely cause of which is considered to b'e as a rt:sult of ,)verstressing of the

surlace lay'er during lhe compaction of the slabilized mdt,srial at the tim{l of construction. This

37

IRC:SP:{}9'2010

inducesaseriesofsnat lowshearplanesinthesur|acelayerandr{}su| l inasl l raq>fa| | ing.otfdensity of the materiat towaros the upper surface. overstressing is mrlst prevarlent wirh unirormry

graded non-cohesiv" ,;;r. tr c'an be avokJed if special care is talren wilh t"le compaction and il

towed vibrating roller:; aie usecl'

A survey ol l(nor,vn (lauses of lack of durability ol stabilized lallersi ccnlirrned th:rt the mosl'

comflron problem was surlace disintegration ol the primed layerr during construction ancl

scabbingofthesea| inserviceduetoaninadequatebondwiththerstabi | iz:e.dmatr;r ia| .Theselproblemsarearesu|tof i rradeq,ratecompacl ionandcuringandaremorel ike|y. |ooccurinhot '

dry climrltes. Ap.rrt trom the problenr of surface disintegration' lonq{erm durrability nnay also bt:

impairerl bY the effecls of sulphates arrd by carbonation'

T .6Cont ro lc l fRef lec t i veCrack ing inCementStab i l i zec lPavent r ;n t : ;

Afthoueth the potental exists lor reflection crac{ting vvhen a cemenli-stabilized baso: is used in a

pavetnr:nlstructure,propercclnslructionanddesigntechniquesca.nrninirni:.lelhelrolentialthlat

the pavement 'ruill be adverserly affected'Proper construction pr€tctices to minimizedrying'

pre-cracking soon after conslructbn, and dasigning {or stress relie{ are all valid rnethods that'\^'ill

rgduceoreliminatelheformailono|re||ectioncracksincemc.nt-sti:biljzecll]as€,s.

There ilre several fitctors as cli:scus-sed in the previous chaptel 'rvhiDh conttjbute tcr lho crackhtg

in a cement-sterbilizr,'d base/slrb-base' wilh r.egard to material characterisl'ics' thr: type o{ soil'

cemenl conlent, degree of cornpaction and curing, and temperirture ancl mrlisl'ure chang':s

direc$r influenoe the degree o1 shrirrkage'

There are a nurnDerr of prcventative measures and riesign cor'cept.; that calt lrc r'rserd to minimize

shrinkiage cracking in the cernent'stabilized base' and to reouce the potential'that base cracks

will rellect throrjgh {he asphalt surface' Methods of controlling rr:flex:tive cracki'g include proper

conslruction and curing of ttre stabilized base, reduction of cra'c|t size thrrrugh the use o{

.0recracking,,, anlJ relief of lstress concentralions throug|r t|re use of |]exib|e |ayers in lhe

pavement slrutltur€)'

A cement_stabilized base provides excellent support for asphalt surfaces. Th'a sbbilized belse

malerial is stronger, more unilorm and more water resistant than im un-stiabilizec base' Loads

are distributed orrer a iarger area and stresses in the $ubgretde are recluced' However'

cement-stabilizedbasescanlalsobethesourceofshrinkagercracl'lsittthr:stabilizedbasela'/er'which cilrr reflect Lnrough th€ asphalt surfacer' Tfte cracks thal develop are rlot the result of a

38

l i lO i iP:Bl)-2:010

structural deficiency, but railrer a natturat characteristic of cement-stabitiz:ecl oases"lhe:iurface

c r a c k s l e n d t o f o l | o w t h e S a m e p a t t € | r n a s t h e c r a c k s i n t h e b a s e , a n c | a r e r e l e r r e l j t . f , a s'rellection" crar;ks.

|nmostcases,ref |ect ioncracksarenarrow(lessthan3mm)andwil l r rotaclverse|ya|{ectthepertormance of ffte pa!,emtrnt. l-lowever, wder cracl<s can resuli in a rough ridirrg surfacer and

deterioration of the pavemelrrt. The wide cracks create an environment for lvaier ittfrltrallion and

subsequent pr'rmping oll the undedying subgrade'

several faciors contribute lo the crack:ing and crack spacing in a cemenl slabiliz:ed bas;e which

include material chara,oteristics, construction procedures, trafflc ancl restrainl itnposed crn the

base by the subgrade. with regard to material characteristics the primaryl cause c'f crilckirrg is

due to drying stuinknge ()[ tlte ce-'nt,arlt stabilized base' The degree of drying 'thrinkage is

affected by thr; type of soit, degree of cornpaction and curing, (€menl contelrtt , ternperatur€ls and

moislure changes.

cementstabi l izeld{rne'grainedsoi lse:.g.claysexlr ibi tgreaiershnnl ' :agetrtat tc( ' 'nt t} t t ls; tal ; i l izecl

granular soils,. Althougtr slabilized clery soils develop higher total shrinkagrl tharr rlranularsoils'

ttre cmcks are typically finer and more closely spaced often ol hairline rrariety spaced 0'6 to

3.0 m apart. The granulitr soilsgenr:rally produce lerss shrinkage brrl develolc largrlr r:racks

typically spar;ed at 3-0 1o 6'0 nl apart'

Fine grain gr;ained soils hilve large :;urface area thirn granular soils ancl typically require higher

moistureconlentforcompact ionpuPoses. lnat idi t iorr .cementcontentforf iner:rraine<ist l i lsaregeneraily 2 to 5 percent irigher than granular soiis in order to achieve arlequate durability and

strength. Both these lractor contribut€r to higher moisture conients fot slatlilized finer graiintd soils

and consoquently higher orying shrinkage'

The effecl of compar:tiorl on shrilll(age characlerislics ol cement ste'bili;led nratrrrial plays irtt

important role. Awell cornpacted mixtureexhibils redttcecl shrinkagr: potential' betaus;e the soiV

aggregates partctes are packed tightly together resulting in red-ced voicls;. 11 fras lreen rtlported

that compacrtng cement r;tabilizecl srril at modified pr<rtor etfort, reduc'es shrinkaqe significanlly

as cornparal t0 stabilizerl soil compacted to standard proctor densi\r Tlre reasorrforlhe same

can be attributed to llre ferct that tl're ,rptimum moislure contenls ol rnodilied proct')r cDmpaction

are typically le$s than at sitandad proctor compar:tion which helps t0 relcjtrce shrinfiage'1he least

amount Of S;hrinKag(| iS oblained lor the stabilized material at the highe'st density and lovrest

moisture contenl.

lR0:SP:89-2t110 , ,L ,^-^ '

cementhydrationcontributeslesstoshrinkagethancloesmanyotherfaclors'ln{act'forsoils

tha.t exhibit volume chanl;e without cement,

-nc,reasing cement will decre;rse total shrinkage' I

However,exc}essiveamountsofcementcanexa'cerbatecrackirrgintwowirys:First,increased

cementcontentscausegreaterconsumptionofwaterduringlhvdration,thusincreasingdrying

shrinkage.Also,highercement|eve|scausehigherrigidityandexcessivestrength(bothtensile

and comPressive)'

Merthods of controlling reflective cracking basicrllly fall irrto tl^re two categories :

. Pre-crercking

Providing lor stress relief at llrrl base-s'urfzrce' inter{ace

Prxrackir lg;Minimizing,]rackwidthwithF,roperconstruct ionandcuringprocedures'as

discussed in lhe previous stlctions, witl e|iminat'a mur:|r rlf rhre polential lor wide cracks. Another

method to reduce crac;k width is a relativelrl new Srrocedure called 'p/e-cracking"' where

hundredso{linymicro-cracksdeve|opinsteadot|singletrans;versecracks'Themethodhasbeen

st.rccessfuIlytriedonsevera|proiectsintheUnitedSates.Theplrocedureirrvolvessevera|passes

of a large vibratory roller wer the cement-sli$itized ba;a one lo iwo days atter {inal compaclion'

rTnis introduces a nerw.rk of crosery spacecr hrairrine crercks; into the cement-slabilized material'

which acts to relieve the shrinkage stresses in the earl'l stages of curing' and provides a crack

pat te rn tha tw i | |m in imize thedeve |opmento ] ,w ideshr in 'kagecracks . lnadd i t ion ,s ince the

;>re'cracking is perlornred shortly after placo,nent, the ..micro. cracking. wil| not impact the

Pavemenl,sovera||structuralcapacityasthecrackswilIhealeindl|recentent-stabilizedmaterial'arillcontinue to gain stren$h wilh time'

slress Betief! Another method of reducirrg the pbtential Jclr reflection cracking is to ielieve

the stress concenlrations that tesult {rorn cracks; in the cement-stabilized base' The

forowing rhree method:; have been successfu*y usedtc,rercruce the srress;es rhat cause reflection

cracks:

1)Ab i t r :m inoussur |ace t rea t r€n t (ch ipsr :a | )be tween l 'hes tab i | i zedbaseand

theaspha|tsurlace,Theadciitionalllexibi|ityofthesurt|acetreatment|ayerwi||

he|ptoreduceStresscorrcelntrations'Tl^ris.surfacetreatmenta|soprovidesan

excel|enltemporarysurfaceduringconstructionlortrafficcontro|'

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2\

a \

IRC:SP:89-2010

.Ageotexhlebetweentnestabi| izedbaseandsiurface'orbelweentheasphaltbindei and wearing courses' Simi|ar to the sL|r'ace ln?atmenl, the gecrtexti|e

provides flexibili$ and €rcts to intercept cracks 'i'rdthoul terttinlg urem pass hrough

the maierial.

A 50 mm to'!Oo mm ;ayer ol unbound gran'ular materieil bertween the starbilized

trase layer and the asiphall surface. This us,a of il 'sandwich' or'in'verted"

pavemeni design add:; additjonalstructure t,c the [tav'ernenl, and will Srrevent

the propaelation ol crar:ks through 1o the surf;rce layr:r'

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