ROLLER COMPACTED CONCRETE FOR DAMS

7/25/2019 ROLLER COMPACTED CONCRETE FOR DAMS

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ROLLER COMPACTED CONCRETE FOR DAMS

1.0 INTRODUCTION

Roller Compacted Concrete (RCC) is defined as a concrete of stiff consistency, compacted byvibratory rollers in thin lifts most commonly not exceeding 300 to 600 mm. It is gainingorldide acceptance for !se in constr!ction of gravity dams.

RCC constr!ction has considerable appeal in areas here the constr!ction season is short, and ingeneral, has an economic advantage in the time factor or cost. "ith this bac#gro!nd, RCCgravity dams become the primary alternative for potential dam sites ith s!itable roc#fo!ndations and ade$!ate aggregate so!rces. %eca!se of its lo ater and cement content, RCCis less s!sceptible to shrin#age or crac#ing. Its !se eliminates the need for constr!ction &oints andthe str!ct!re can be b!ilt in a contin!o!s operation into a monolith hich o!ld not createthermal problems associated ith mass concrete.

' great diversity of practice and opinion exists on the adoption of this ne technology d!e todifferences in methods of placement, consistency and mix proportions of RCC ith respect toconventional concrete, based on site specific conditions. %eca!se of this diversity, RCCtechnology has been split !p into three distinct gro!pings depending on the type and design ofconcrete !sed, namely

Rollcrete Concrete containing *as d!g+ gravel stabilied ith lo cementcontent e.g. concrete !sed in the repairs to the stilling basin at-arbela am (/a#istan). -he cement content in rollcrete is of theorder of 600 #g1m3.

Lean Concrete Concrete containing aggregates of nearly normal $!ality and locement content e.g. concrete !sed in 2h#aa and hima&igaaams (4apan) and "illo Cree# am (5'). -he cementitio!smaterial content in the case of lean RCC is generally less than 00#g1m3, o!t of hich flyash content is abo!t 708.

In 4apan, the RCC is #non by the name of RC (Roller Compacted am)9 s!ch a concretecontains cementitio!s content beteen :0 and 30 #g1m3. -he method involves placingconcrete in lifts !pto ;00 mm thic#, green c!tting of lift s!rfaces and c!tting of contraction &oints!sing a vibratory &oint c!tter.

High Pate Content Concrete containing aggregates of nearly normal $!ality andConcrete in hich the paste content is :0 percent or more of the total

vol!me of concrete e.g. concrete !sed in


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Cement, 33 Arade (Bo!rth Revision)@ or /ortland /oolana Cement conforming to I7??;6 @pecification for /ortland /oolana Cement (econd Revision)@ can normally be !sed.-he selection of cement type is based on str!ct!ral re$!irement and not on the method of

placement or consolidation of concrete.

!.! Fl#ah

Blyash sho!ld conform to Arade I of I3:? @pecification for Blyash for 5se as/oolana and 'dmixt!re (Birst Revision)@9 it sho!ld have percentage of ater e$!al to or lessthan >8.

!.$ Aggregate

Coarse and fine aggregates conforming to I33?;0 @pecification for Coarse and Bine'ggregates from at!ral o!rces for Concrete (econd Revision)@ may be !sed depending onenvironmental expos!re and strength re$!irements. 'ggregate variability affects cement and

ater re$!irements of the mix hich in t!rn affect strength and yield. -he maxim!m sie ofaggregate ( micron I sieve sho!ld be limited to less than >8 of total aggregate (coarse Dfine) by eight.

!.% &ater

"ater to be !sed for mixing and c!ring sho!ld conform to cla!se 7.3 of I7>6?; @Code of/ractice for /lain and Reinforced Concrete (-hird Revision)@. /otable ater is generallyconsidered satisfactory.

!.' A("i)t*re

'dmixt!res normally !sed in RCC are for set retardation and1or red!ction of ater content,hich sho!ld conform to I?03?;? @Indian tandard pecification for 'dmixt!res forConcrete@.

$.0 MI+ PROPORTIONIN, ASPECTS


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(ii) Eean RCC mixes.(iii) micron fines content re$!ired Febe time

of approximately 0 seconds to compact.


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metre ide layer beteen the !pstream face of the dam and the edge of the compacted RCC./lacement of conventional concrete sho!ld precede closely that of the RCC so that theconventional concrete can be blended into the edges of the !nconsolidated RCC.

Bor the above type of constr!ction, the cementitio!s material content of the RCC generally

ranges beteen 0 and 00 #g1m3

and of the bedding mix above the prepared fo!ndation beteen>0 and :00 #g1m3. Bor the base layer of roller compacted concrete, the cementitio!s materialcontent varies beteen :0 to 70 #g1m3. -he flyash content generally ranges beteen 70 to 60#g1m3.

$.$ High Pate Content Concrete

-he above RCC envisages a lo cement content concrete ith lo or#ability, to red!ce thecost of concrete and the potential for heat generation in the str!ct!re. -otal

cementitio!s content (defined as the content of cementsied strength imparting particles i.e.

/ortland cement H poolana) is in excess of abo!t >0 #g1m3

. In s!ch mixes, in order achieve adensity near to the theoretical airfree density, a relatively high content of paste is re$!ired. Borthis p!rpose, flyash as poolana has proved to be the best ith ratio of poolana to /ortlandcement as high as 7 by vol!me having been !sed. -he high paste content has been fo!nd toimprove the bond beteen s!ccessive lifts and no treatment of the s!rface of the previo!s layer

before placement of next lift is necessary if the time interval beteen placement of lifts is 7 ho!rsor less. -he RCC is designed to have a minim!m of air voids and insit! density sho!ld therefore

be as high a percentage of the airfree density as possible.

Bor air voids to be minim!m, a minim!m vol!me of paste is re$!ired ithin the RCC. -he pastefraction is the absol!te vol!me of cement, flyash and free ater. -he mortar fraction is the

absol!te vol!me of the paste and fine aggregate passing 7.;> mm sieve. %elo a paste1mortarratio of 0.3>, the voids in the fine aggregate ill not be filled by paste and a high relative densitycannot be achieved and to have a high density, it sho!ld be 0.3 or above and for good bond, theratio sho!ld not be less than 0.7.

$.% Other Pro-ortioning Metho(

2ther proportioning methods have eval!ated RCC !sing soil compaction proced!res. -hese mixdesign methods have not been !sed for concrete gravity dam sections9 hoever, they have been!sed on a n!mber of placements, incl!ding emergency repairs. -hese methods concentrate onvarying the moist!re content for a mix ith a fixed aggregate grading and cementitio!s materials

content to prod!ce the maxim!m dry density of the RCC. pecimens are compacted !singmodified soil compaction e$!ipment to facilitate !se of a larger


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aggregates, fines content, cementitio!s material content and compactive effort applied.


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Bolloing methods have been adopted for forming faces of RCC dams

(i) Conventional concrete against formor# (ii) RCC s!pported by fill sho!lders(iii) RCC against precast concrete panels

(iv) 5nformed face of RCC(v) RCC against formor# (vi) Conventional concrete against precast concrete panels ith membrane(vii) /recast concrete panels bac#ed by asphaltic mortar (placed hot)(viii) /recast concrete bloc#s(ix) lip formed1extr!ded facing elements(x) 0 m3of RCC placed.

-he moist!re content of RCC mixes is critical to achieving compaction. -his sho!ld becontrolled at the batch plant by recording the eights of the materials as they enter the mixer and#noing the moist!re content and absorption of the aggregates.

Consistency testing sho!ld be performed on a reg!lar basis as a means of eval!ating theor#ability and relative compactibility of the RCC. -he RCC sho!ld be sampled for testing at

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the batch plant. -he Febe time to compact the sample sho!ld be correlated to the compactibilityof the mix ith a vibratory roller thro!gh n!clear ga!ge density tests and confirmed ith drillcores.

Eayerise monitoring of placement temperat!re of RCC sho!ld be done reg!larly.

9.0 CONSTRUCTION TECHNI7UE

9.1 ,eneral

' 7.> m ide vibratory roller of appropriate design ma#ing fo!r passes and travelling at a speedof 317#m1hr can compact more than :60 c!.m per hr of no sl!mp concrete in :> cm layers. 'conventional batch plant o!ld re$!ire approximately fo!r 3 c!.m mixers or one large ? c!.mmixer to match the compaction capabilities of one large roller on a contin!o!s placementoperation.

9.! Mi)ing


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-he type of transportation e$!ipment !sed to move RCC from the mixing plant to the placementarea ill be infl!enced by the largest aggregate sie specified in the mix. 3 mm tonnes !s!ally cannot operate closer than > to :3 cm to form or# or

obstacles, so that rollers smaller than to : tonnes are !s!ally needed to consolidate the concretein these areas.

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-he minim!m n!mber of passes for a given vibrating roller to achieve f!ll consolidation(maxim!m attainable density) depends primarily on the concrete mix and layer thic#ness. Eayerthic#ness ill be governed more by spreading efficiency than by compaction re$!irements. -estssho!ld be performed in @test fills@ prior to or d!ring the early stages of constr!ction to determinethe minim!m n!mber of passes for f!ll consolidation, !sing the correct mix and the planned layer

thic#ness. -he consolidated mass of a mix ith ade$!ate paste vol!me ill respond to or#ingof the s!rface li#e stiff mo!lding clay or &elly.

-he only s!re ay to determine f!ll compaction in the field is by meas!rement of the compacteddensity and comparison ith the same mix f!lly compacted in the laboratory by extendedvibration. -he n!clear meas!ring devices no !sed in soil density meas!rements are applicablefor density meas!rements of compacted layers.

Hori:ontal contr*ction ;oint oriontal constr!ction &oints may either be of the planned or!nplanned variety. 'ny time a placement layer is not covered by the time it reaches initial set, itill no longer be or#able and becomes a cold &oint, or !nplanned constr!ction &oint. -his time

element is very sensitive to temperat!re, the amo!nt of portland cement in the mix, and the typeand set retarding characteristics of the admixt!res, if any. 2n the basis of time element, thereappears to be a definite advantage in !tiliing setretarding admixt!res, thereby extending thesetting and or#ing time, providing flexibility against !nsched!led delays, and alloingenlargement of the or#ing s!rface of the lift.

If the constr!ction &oint has been #ept clean and moist thro!gho!t its expos!re, no &oint treatmentis re$!ired. If the s!rface has been contaminated by dirt, m!d etc., the prescribed treatment isthat hich is necessary to remove the foreign matter. If the s!rface has been alloed to dry o!tcompletely, then it sho!ld be thoro!ghly cleaned by et sand blasting or other acceptable meansof cleaning and preparation of hardened constr!ction &oints.

atisfactory bond at horiontal constr!ction &oints can be ass!red by !tiliation of a bedding mixith 3 mm, or smaller maxim!m sie aggregate provided the mix has a paste vol!me at least:08 greater than the maxim!m vol!me of paste hich prod!ces maxim!m density. -he mostessential re$!irements of the bedding mix appear to be excess paste, excess etness, and excessstrength over that of the mass mix. "hen the mass mix consists of 3 mm


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layers of stra, > cm of soil, or some other form of ins!lativematerial.

-he s!rface of compacted layers sho!ld be protected against damage ca!sed by constr!ctionmachinery and e$!ipment.

In order to ens!re immediate drainage in case of a s!dden donpo!r, the top s!rface of RCCsho!ld have an incline of :8 directed !pstream. RCC placement sho!ld be s!spended henheavy rain starts, and all placed RCC sho!ld be compacted as $!ic#ly as possible. RCC, hichcannot be f!lly compacted $!ic#ly eno!gh to prevent contamination from rain ater, shall beremoved.

10.0 RCC IN PRACTICE

In practice, Roller Compacted Concrete has been !sed1proposed for !se in atleast 00 damsorldide either in original constr!ction or for repairs1rehabilitation or#s. RCC Da" Contr*cte(? Un(er Contr*ction or Planne(

ame of am Co!ntry eight (m) Eength (m)

Fol!me

RCC(m3 x 03)

-otal(m3x 03)

hima&igaa 4apan ? :70 6> 3;

olbeam "ood 5= : 0 7 >

"ilo Cree# 5' >: >73 33 33

Copperfield River '!stralia 70 370 70 >; :7 :;

Aalesville 5' > :? 6 ;

Castilblanco de los 'rrayas pain :> :3 7 :0

=eng#o! China >; :3 73 60

Craigbo!rne '!stralia :> :7; :: ::

Arindstone Canyon 5' 7: 3?6 ?6

e 6 :30 3: 73

'rabie (no > 0 >

-amagaa 4apan 00 73: ;>0 >7

/iri#a 4apan 70 ?0 :0 360Gl# Cree# 5' > 36> :70 1'

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'in al =oreima :7?

3:0 > 1'

tagecoach 5' 76 > 37 3?

Eongmentan China > >; ;3 0=nellpoort . 'frica >0 :00 7> >?

5r!g!a 'rgentina ;6 6; >?0 6:6

-ianshen$!iao o. : China >? 7?? 60 3:

Lito! China 7; ? : 3:

'sahiogaa 4apan 7 :60 ;7 3>0

C!esta %lanca 'rgentina 3 ;?3 ;30 30

"oledans . 'frica ;0 :6 >0 6?

hangban China >0 :: 1' 1'

"rigglesade . 'frica 37 ;0 7

Ea /!ebla de Caalla pain ;0 1' 7 ?-ag!angba China >> 1' 1' ?:

M'o!lo! > 36; 1' 3>

/latanovryssi Areece ?> :;0 1' 700

/etit a!t Brench A!yana 36 ;70 :30 70

1' 1'

/amo 5' 0 1' 3; 1'Griama pain 7> 1' : 1'

FareaArande %rail 3 1' 30 1'

-rigmil > 1' :000 1'


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Tale != A--lication o RCC or Re-air &or@

ame of /ro&ect tr!ct!re RCC Fol!me (m3) ched!le

-arbela, /a#istan Repair of t!nnels,spillay etc. :,>:>,000 ?;7?0

Itaip!, %rail %ac#fill :6,000 ?;

%onneville II, 5' Cover for roc# excavation to preventair sla#ing

30,000 ?;

/oer /lant Reclaim/ond, ibley,

Tale $= Roller Co"-acte( Concrete or E"an@"ent Da" Rehailitation in the USA

/ro&ect (NearConstr!cted)

City1tate


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orth Bor# -ostleRiver(?0)Replacementpillay

Castle ale, "ashington

3 ,000

%ronood Co!ntry

Cl!b (?7)

%ronood, -exas? ,700

pring Cree# (?6) A!nnison, Colorado >3 7,70

arris /ar# o. (?6)

%ailey, Colorado :,300

Comanche -rail (?) %ig pring -exas :> 6,>00

'ddic#s D %ar#er(?)

o!ston, -exas7.> D 36.> >6,;00

%ishop Cree# o. :(??) e Gmergencypillay

%ishop, California7 7,000

-ellico addle (??)

e Gmergencypillay

Eenoir City, -ennessee

?,>00

Aoose Ea#e (??) ederland, Colorado 3> 7,:00

%oney Balls (??) Gscanaba, 7,>0

Comanche (??0) Gstes /ar#, Colorado 76 3,>00

=emmerer City (??0) =emmerer, "yoming 3 7,00

ic#a&ac# (??0) eAravity pillay

o. /ittsb!rg, -ennessee6> 0>,000

-hompson /ar# o. 3(??0)

'marillo, -exas30 :,;30

"hite Clo!d (??0) "hite Clo!d, ,000

Rington o. > (??)Combined /rincipal DGmergency pillay

Rington, /ennsylvania60 6,300

altlic# (??) -oGmergency pillay

4onston, /ennsylvania0 ,00

'shton (??) 'shton, Idaho 60 ;,;00

Ea#e Eenape (??) 0

Aoose /ast!re (??) %rec#enridge, Colorado 6> 7,:30

olmes Ea#e am(??)


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Fig*re 1= T#-ical Rehailitation For S-illa# Section

11.0 STATUS OF RCC IN INDIA

-here are : thermal poer stations in the co!ntry, hich are prod!cing more than 00 milliontonnes of fly ash ann!ally. -he effective !se of fly ash as a poolana in the man!fact!re of and for

part replacement of cement in cement mortar and concrete, limepoolana mixt!re and prod!ctss!ch as fly ashlime bric#s, a!toclaved aerated concrete bloc#s etc. has been established in theco!ntry since long. Bly ash has also been !sed in ater reso!rces sector for part replacement ofcement in mass concrete for dams. oever, in the year ??7, a meagre 38 !tiliation o!t of 70million tonnes of fly ash prod!ced in the co!ntry co!ld be achieved. -he Aovernment of India

recogniing the importance1potential of fly ash, established OBly 'sh


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dy#es, s!bstit!tion of sand in mine stoing, as a soil amendment agent in agric!lt!ral applicationsetc. Its gainf!l !tiliation in hydro poer1ater reso!rces sector has, hoever, yet to pic# !p.ydro poer1ater reso!rces sector has immense potential for !se of fly ash and its prod!cts.In concrete dams, fly ash can gainf!lly be !tilied for s!bstit!tion of cement !pto 3>8 inconventional concretes and !p to abo!t ;>8 in the Roller Compacted Concrete (RCC). It

provides not only saving of precio!s cement b!t enables faster constr!ction, re$!ires loercapacity chilling plants (d!e to loer levels of heat of hydration in RCC) and ma#es str!ct!resmore d!rable.

%ased !pon this concept, "ater Reso!rces epartment of Aovt. of


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: Constr!ction of> 00 mlong 5pper am

7)

!ccessf!lly constr!ctedthe dam !sing 3>.>; m3

RCC ith 6>8s!bstit!tion of cement

by fly ash. -otal of 76

tonne of fly ash and3:0 tonne cement as

!sed.

3 Constr!ction of> 0,000 m3RCC ith

6>8 s!bstit!tion ofcement by fly ash. 'total of abo!t ,000tonnes of fly ash and

>,666 tonne of cementis expected to be !sed.

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ROLLER COMPACTED CONCRETE FOR DAMS