IRC t 34~I9~O

RECOMMENDATIONSFOR

ROAD CONSTRUCTIONIN

WATERLOGGED AREAS

THE INDIAN ROADS CONGRESS1996

IRC :34-1970

RECOMMENDATIONSFOR

ROAD CONSTRUCTIONiN

WATERLOGGED AREAS

Publishedby

THE INDIAN ROADS CONGERSSJamnagar House, ShahjahanRoad,

New Dethi-IlOOli1996

Price Rs,24,00(PlusPacking& Postage)

IRC : 34-1970

First PublishedReprintedReprintedReprinted

January,1970May, 1914May, 1980August,1996

[Rights ofPublicationandofTranslation are reservedj

Printedat SagarPrintersandPublishers,New Delhi-I 10003(1000copies)

IRC: 34-1970

RECOMMENDATIONS FOR ROAD CONSTRUCTIONIN WATERLOGGED AREAS

1. INTRODUCTION

A Panel.Discussion* on the subjectof constructionof roads inwaterlogged areas was held during the Hyderabadsessionof theIndian Roads(Congressin January 1959. As a resultof this discussion,the Soil ResearchCommitee (personnelgiven below) took uponitself thetask of framing recommendationsfor road constructionintheseareas:

B.D Mathur ConrenorDr. HI. Uppal Member-Secretary

MEMBERS

N. Amanullah J.S, MaryaK. Basanna Prof. S.R. MehraIt. Col, Ularish Chandra H,V, MirchandaniS.N. Gupta A. MuthukumaraswamyDr. R.K. KoHl A. R. SatyanarayanaRaoKewal Krishan S,N. SinhaMahabir Prasad J.M. TrehanSIC. Malhotra Dr. IS. UppalM.R. Malya

Director General(RoadDevelopment)&AddI. Secy.to the Governmentof india.

(Ex-Officlo)

The recomendationsdrafted by theCommitteeweresubsequ-ently reviewedby the Specificationsand StandardsCommittee(per-sonnelgiven on inside front cover)andafter approvalof the Councilat their 72ndmeetingheld on the4th October, 1969 arenow sugges-ted for generaladoptionin the country.

2. SCOPE

‘the recommendationsdealwith the problemof roadconstruc-tion in waterlogged areas, including those subject in additiontoflooding and/orinfestedwith detrimentalsaltslike the sulphatesandcarbonates.The recommendationsrelate both to the constructionofnew roadsand to the remedial measuresto be adoptedin the caseof’ existingconstructions.

*The backgroundnotefor the PanelDiscussion is publishedin the Journalof theIndian Roads Congress,Volume XXIII-part 2 and discussionin theVolume XXIH-part4,

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IRC 34-1970

For the purposeof theserecommendations,waterloggedareasare consideredto be thosewhere thelevelof subsoilor standingwater is such that for prolongedperiodsthe subgradeimmediatelybelow the pavementis well within the capillaryfringe of the water-table, i.e., within about 1.5 metres.

3. THE PROBLEM

3.1. Due to WaterloggingAs a result of migration of water by ca1illarity from the high

water-table,the soilimmediatelybelow the pavementgets moreandmorewet andthis leadsto a gradualloss in its bearingvalue.

3.2. Due to FloodingWhere flooding for continuouslylong periodsalso takesplace

side by side with waterlogging, the progressivedeformationof thesubgrade,as well asof the pavement, is accentuatedby ingressofwater from the top of the wearingsurfacecomprisingusuallyof athin bituminous treatment. The already inadequatewaterproofnessof the surface is impaired further by strippingof the binder duetoprolonged contact with water. Infiltration of flood watersthroughthe shouldersis anotherfactor aggravatingthe situation.

3.3. Due to Presenceof Detrimental SaltsThe problemis made still more complicatedif in additionto

waterlogging,and/orflooding, injurioussaltslike sulphatesof sodium,calcium or magnesium and sodiumcarbonatearepresenteitherinthe subgradesoil or in the ground water. Damageto crust frominjurious salts can be in two ways—due to physical effect orchemical.

3.3.1. Physical effect of the injurious salts: In waterloggedareasinfested with detrimental salts, the saltskeepon moving upwith capillary moisture. During subsequentevaporation of thesalt-ladenwater the saltsare left behindand they get concentratedin the surface layers.The saltsincreasemany times in volume uponhydration under suitable humidity and temperatureconditions*.Alternate hydration anddehydrationresults in repeatedformationof salt crystals occupying much morevolume than the amorphoussaltslodged in the voids, In due course theserepeated volumechanges break up the structure ofthe pavement,working from thetop downwards.

*As a result of researchcarried out in India, it hasbeendemonstratedthat crystallisationof sodiumsulphatetakes placewhen temperatureis beton32 C and relative humidity above 80 per cent. In northen parts of thecountry theseconditionsexist generally duringthe periodof winter rains,

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IRC: 34-1970

3.3.2. Chemical effect of the injurious salts: The damagedueto chemical action is mainly on account af sulphatesof calcium,magnesiumandsodium. Constructionsspecially vulnerableto thistype of attackare thosecontainingcementlike the cementconcretepavementsand soil-cementbasesub-basecourse.

Cement concrete

The sulphatespresentin the subsoilwhich migrateto the topby capillarity react with the free lime liberatedfrom cementresult-ing in the formation of gypsum. This reaction is accompaniedby aconsiderableincrease in thevolume of the solidswhich is known tolead to the destructionof the hydratedcementmatrix. After gyp-sum has been formed,or if calciumsulphateitself is found in thesoil or ground water, tricalcium aluminatein the hydratedcementcombineswith gypsumto form needle-shapedcrystalsof double saltslike calcium sulpho-aluminatewhich give rise to further expansionof volume and damage. Apart from the formationof gypsumandcalciumsulpho-alurninate,the decompositionof hydratedcalciumsilicate by sulphate solution is an additional factor affectingthedurability of concrete. However, this would occur normallyonly inthe caseof magnesiumsulphatesolution which is found generally inwaterloggedareasnearthe sea.

Dissolved carbon dioxide and bicarbonatesalts presentincertain marshyand rice growing areasalso takepartin the leachingof lime liberatedfrom cementandslowly attackingthe cementitiouscalcium silicate hydratesformed. Such solutionsare characterisedby pH valuein the acidic range.usuallybelow 5.

Concrete is not directly attackedby solidsulphatesalts,butonly by their solutionsin water, so that it is the amountof saltsdissolvedin the ground waterthat determinesthe rateof attack. Asa result of chemicalaction of sulphates,the cementconcretepave-ments suffer internaldisintegration andgradual spalling from theunderside. The processdescribedis, however,slow.

Soil cement

Presenceof sulphates in waterloggedareashasa detrimentaleffect on soil cementmixtures akin to that in the caseof cementconcretepavements.

Bituminous constructions

It does not appearthat thesesalts, in the concentrationtheynormally occur in soil, groundwateror sea-water,haveanydetri-mental chemicaleffect on bituminousconstructions.

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IRC 34-1970

Water-bound macadam

Saltsdo not directly affect unsurfaced water-boundmacadamconstructions providedthe filler materialusedin them is inert andfree of injurious constituents.

4. RECOMMENDATIONS ON ME1’I-IODS OF ROAI)CONSTRUCTION IN WAThRLOGGED AREAS

4.1. The recommendationsare ‘iivided into the followingthreegroups:

(a) Road construction in areaswhere theproblem is one ofwaterloggingaloneandis not tied up with flooding or saltinfestation.

(b) Road construction in areas wherein addition to water-lagging floodingfor prolongedperiods is also expected.

(c) Road constructionin areaswhere in addition to water-logging injurious saltsare presentin the suboilor groundwater.

4.2. Different treatments are suggestedunder each group.Someof thesecan be made useof only on newconstructions,andotherson old, while somehold good for both. Broad guidance abouttheseis providedat the beginning of eachsection.

5. RECOMMENDATIONS FOR ROAD CONSTRUCTIONIN AREAS WED RE THE PROBLFM IS ONI OFWATERLOGGING ALONE AND IS NOT TIEDUP WITH FLOODING OR SALT INFESTATION

The remedialmeasuresrecommendedunderparas5.1, 5.2 and5.4 could be utilised both on new constructionsandexisting roads.However,the capillarycutofftechniquedescribedunderpara 5.3 willbe found economicalonly on new roads.

5. 1. Depressingthe Level of Subsoil Water by DrainageMeasures

Satisfactoryresults couldbe achievedby providing 5 to 6 ft deepdrainage channelsas close to theroadbank as possibleandconnect-ing these by su~tableoutfalls to either channelsof irrigation systemor naturaldrainage. Alternatively, burieddrainsof suitabledesignsuchas French drains could be providedat the edgesof the pave-ment forthe loweringofwater-table. Eitherof thesemeasureswill help

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it(( :3..L I 970

in keepingthe top of the suhgradeahove the c tprlla ry li~inn

The methodof drainage is applicable ta all t~pe~~construction(whether rigid or fiexibleb aol ~hoild h.’ p c1 crrcJwherevereconomicallyfeasible.

5.2. Raisingof the Embankment

Where it is too expensiveto provide deepdram.tte 1: a •

specified in para 5.1, it is~recommendedthat subject t~ chdexamination of the economicsof the case,an etnhanK mea.. suchheight may be provided that the bottom of the poemen rent.t iris atleast 1.5 metresabove the highestwater-table,

5.3. Capillary Cutoff

As an alternativeto the recommendationscontainedin p:i ras5.1 and5.2. a capillarycutoff could be provided to arrest the capiI-lary rise of water. Provision of capillarycatoff\ cauld, ltowe~er,proveto he expensise and maybe jtistifi ed only in speciaF c rcitirt-stances.

The cutoff shouldhe placedat least 1 5 cm abve the groandlevel or the standingwater level, whicheverhe higher, a~iF Itistratedin figure on page6. But in no easeshould it be p liii ineJ higherthan 60 cm below the top of the suhgrane. Wit en pr~vLIC .1 thecutoff mediumshouldextend underthe bermsas ~elI.

Suitabletypesof capillary cutoffs are listed under Section 8.Whenthe cutoff medium selectedis of the type hitarnin Lts pr in er.tar felt or polytheneenvelope,it will he advisableta civer it with a,10 to 15 cm thick layer of granular rniteri,tl like sand ía— the dualpurposeof acting as a drainagecoursefor water infiltrating from thetop and of protecting the envelopeduring constructiona~�ainstrnp~ttire by sharpparticlesin the fill material.

5.4. Providing Sufficient i’hickness of the Pavementto beAdequatefor SaturatedSubgradeConditions

in. caseneither drains nor sufficiently high embankmentnorcapillary cutoff canheprovidedon an existing road, the thicknessofthe pavementshould he determinedon the basisof strengthof thesuhgradesoil at saturationandstrengtheningcarriedout accordingly.

This measurecanbe adoptedin the cisc of new canstructionaas well, In that event, at least 10 cm thicknessof sub-baseshouldbe made up of such materialas stahiI ised soil, which will be ~table~~henwet, so that it is not possiblefor the soft suhgradesoth in satu-ratedcondition to work up into the voids.

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JRC .34—1970

THt HIGHEST POS1TiO~i

THE

SKETCHES ILLUSTRATING DESIRED POSITION

O~THECAPILLARY GUTOFF FOR PREVENTING

THE HIGHEST POSITION OFTKE CAPIU.ARY CuTOFF

SUBGRAOE

—-. IZONE OF CAP1I.LARY

SATURATION

GROUND WATER TABL,

(a)10-IS Cm THICK SAND/GRANULARMATERIAL CUSHION WHEN THECAPILLARY CUTOFF IS ABITUMINOUS PRIMER. TARFELT OR POLYTHENE SHEET

60 cm ~~~~1~ZONE OF CAPILLARY

SATURATION

(b)

THE RISE OF CAPj~ARY MOISTURE

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IRC: 34-1970

6. RECOMMENDATIONS FOR ROAL) CONSTRUCTION IN AREAS\5 LIE RI IN ADDI I ION [0 W % 1 [RI OGGING FLOODING I ORPROLONGED PERIODS IS ALSO EXPE:CTED

In the case of roads subject to flooding in additionto water—logging, the following measuresmay have to be takenover andabovethoserecommendedin Section 5 against waterlogging. Thethreetrea mentssuggestedcould be appliedequally on new construc-tions as well as old.

6. 1. Raising of the Embankment

In areassubjectto frequentfloods’ wherethe highestflood levelis not too much above the natural ground level, it is recommendedthat the embankmentshould be raised so that the top of the sub-grade is at least 30 cm abovethe highestrecordedflood level.

6.2. Provisionof Cement Asphaltic Concrete Surfacing

Wherefor any reasonwhatsoeverit is consideredinevitable tolet flood waters pass over the road, and also traffic is heavy andflooding expected for prolongedperiods,cementasphalticconcretesurfacing of appropriate thickness should be providedfor at leasttwo lanesof traffic. The cementconcretepavement,when provided.shouldhavea cement/Limesoil base15 cm thick underneaththe slaband permanentstakeson the carriagewayedgesfor demarcatingthetravelledway. Whenasphaiticconcreteis selectedas the surfacing,the mix shouldbe densegradedandresistantto flood conditions,

Whereformation level of the road is well abovethe surround-ing ground level, side drop walls andguide uprightsmust also beprovided, in addition, the banks should be protected againsterosion.

6.3. Provision of a Thin BituminousSurfacingwith Seal Coat

Wheretraffic is very light andthe provisionof a cement/asphal-tic concretesurfaceis consideredunjustified on economicgrounds.,atolerablesolution will be to providea thin bituminoussurfacingwithseal coatover at least two lane width, usingsuitableanti-strippingagentsand supplementedby guide uprights andside drop walls asnecessar y.

7, RECOMMENDATIONS FOR ROt]) CONSTRUCTION.IN AREASWHIRL IN ADDI1ION TO W~TFRIOGGING DEFRIMFNrkISALTS ARE PRESENT IN THE SUBSOIL OR GROUND WATER

The following recommendationsapply generallyto construc-tion of new roads.On existingroads,measuresoutlined in paras5.1,5.2 and 5.4 may be adoptedfor relief.

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I 1W .14. t 9’N)

7. I. No specialmeasuresare considerednecessary fromthestandpointof physical chemicalactionof injuriotis saltsexcept thosestatedin Sections5 and6 if the concentrationof sulphatesin thesubgradesotl is below 0.2percent (assulphur trioxide) while alsobelow 0.03 percent (as sulphur trioxide)in groundwater, Similarly,sodium carbonateconcentrationsof upto 0.2 percent in subgradesoil and 0.02 percent in thegroundwaterare consideredunharmful.Salt concentrationsmayhe determinedin accordancewith the pro-cedurelaid down in relevant1.5.1. Standards--——IS 2720,part XX 111

I 96N ‘‘Methods of Test for Soils : Determinationof CalciumCarbonate”, and IS 2720, part XXVII.—.”Methods of Test forSoils:Determinationof Total Sulphate’’.

No damageis expectedfrom dissolvedcarbondioxide or bicar-lionate salt solutions (‘met with in certainmarshyareas)providedthe p11 valueof the solutions is higher than 5.

\\ here the concentrationof thesesaIts is in excessof the safelim its specified above, specialmeasuresas indicated below arerecornmendedas aguide for roadconstruction.Thesemeasuresarein additionto thoserecommendedin Section 5.

7.2. Flexible Pavements

7.2.1. Water-boundmacadamroadswith or without bituminoussurfacing: Even if concentrationof salts in the .subgradeor groundwater is higherthan the safelimits prescribedin para 7. 1, no specialmeasuresother than those set forth in Section5 are considerednecessaryfbr water—boundmacadamroadswith or withoutbituminoussumlitcing except that the filler usedin water-boundmacadamandsoling shouldbe inert and free from injurious salts,

7.2.2. StnbilisedSoil Constructions:

(a) Mechanicalstabilisation

(h) Cement andlime stabilisatioa

(c) Bituminousstabilisation

If the above constructions~’arecontemplatedin waterloggedareasinfested with salts, the soil usedfor stabilisationshould notcontain more than 0.2 per cent of total soluble suiphatesandcarbonates,

Besides this, to preventthe injurious saltsin the subgrade orground waler from coming into contactwith stabilisedsoil courses,asuitable capillarycutoff out of thosedescribedin Section 8 shouldbeprovided underneaththe pavementextendingacross thefull widthof Ihe roadway, treatingit as an essentialmeasure.

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IRC : 34-1970

7.3. Rigid Pavements

When sulphatesare in excessof the safe limits prescribed inpara 7. I, the following additionalmeasures’are recommendedduringthe constructionof cement concrete pavementsoverand abovetheprovisionsof paras5.1 and 5.2.

7.3.1. Since all typesof concrete,irrespectiveof the type ofcementused, are more vulnerahle to salt attackduring the initialperiod of hardeningthan when fully set, it is of importanceto pre-vent contact hetsseen the ground water and concretein the earlystages. For this purpose, applying a light coat of bitumen to theunderside of precastunits,protectingcast-in-situconcreteby a thinbituminised coatingon the basejust below the slab, or prosision ofoneof the capillary ctitoffs mentioned in Section 8, are someof themeasuresrecommendedfor adoptionunder relatively nil d condi-tions of exposuresto sulphateattack,viz,, when sulphale eoneentra—tion in soil is uptoabout 0.5 percent,

Undermoresevereconditions,i.e. whensulphatesarc in excessof 0.5 per cent, the bituminous coatingsusedshouldbe thickert asthey are known to possesshigher durability.

7.3.2. Furthermore, the follosving measuresare suggestedassuitable for minimising adversechemicaleffect of the sulphatesonconcrete:

(i) Designinga dense,well-compacted,high quality concretewhich will have low permeability aginst ingress ofsulphatesolution. (This is recommendedeven svhenSO~in water is above0.02 percent).

(ii) Use of special sulphate resistant cement, puzzolaniecement or super-sulphatedblast furnace slag cement,depending on availability and economy(when sulphatecontent is more than 0.3 per centin soil and morethan0.03 per centin ground water).

7.3.3. In areaswherethereis dangerof damagefrom dissolvedcarbon dioxide or bicarbonatesaltsas evidencedby p1’1 values ofbelow 5, the provision of a waterproof layer below the concretepavement,such as heavyduty hituminised paperor polythenesheet,and use of a dense,well—compacted,high qtialitv concreteare themeasuresrecommendedfor adoption.

* For thepurposesof this speeifleation, thin coatsareconsideredto be those~shich the rate of application of straight-run bitumen is 12 kg per 10 iis~

and thick coatsare thosein which tin’ rate of :sppiieation is 20 kg per ID nO.

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IRC: 34-1970

8. SUITABLE CAPILLARY CUTOFFS

8. I. Provision of Sand Blanket

Sandblanket of adequatethicknessover the full width ofembankmentis recommendedasan effective capillarycutoff. Thethicknessof the sa.ndblanketneededto interceptcapillarity dependson the particle size of the sandand maybe determinedfrom thefollowing formula*:

(8)°.~2

dwhere = thicknessof sandlayer in cm

2t1~>( (1~d == — —

d1 -~i- d2

meanparticlediameterin mm== aperturesize of sieve(mm) through which

the fraction passesaperture size of sieve (mm) on which thefraction is retained.

The sandshall be compacted after adding sufficient moisture topermit easy rolling. Alternatively, it might be compacteddry ifthe facility of vibratory roller wasavailable.

8.2. Someof the Other Capillary Cutoffs**

8.2.1. Bituminous impregnation using primer treatment: 50 percent straight-run bitumen (80-100) with 50 per cent high speeddiesel oil or its equivalent in two applicationsof 10 kg per 10 meach, allowing the first application to penetratebefore applyingthesecondone.

8.2.2. Heavy duty tar felt: Providing an envelopewith heavyduty tar felt.

8.2,3. Polythene envelope: Providing an envelope withpolythenesheetsof at least400 gauge.

8.2.4. Bituminous stabilised soil: Providing bituminousstabilisedsoil in a thicknessof at least4 cm.

tThis formula was proposedinitially by the Public RoadsAdministrationand is published in l-Iighway ResearchBoard Proceedings,Vol. 21, 1941, page452.

**Experience on the successfulperformanceof capillary cutoffs suggestedin para8.2 is, however,limited.

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