Seminar on Hydro Sector - Proceedings

8/17/2019 Seminar on Hydro Sector - Proceedings

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National Seminar cum

Business Meet on Use of Fly

Ash in

HYDRO SECTOR

March 4 –5, 2005

Ramada Plaza, Juhu Beach

Mumbai

Organised byFly Ash Utilisation Programme, TIFAC, DST

in association withMinistry of Power, Ministry of Environment & Forests,

Ministry of Water Resources and Irrigation DepartmentGovernment of Maharashtra


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PROGRAMMENational Seminar cum Business Meet on Use of Fly Ash in Hydro Sector

March 4-5, 2005, Venue : Ramada Plaza, Juhu Beach, Mumbai

MORNING SESSIONMarch 4, 2005

09:00 – 10.00 REGISTRATION

10:00 – 11:00 INAUGURAL SESSION

10:00 – 10:05 • Welcome by Dr. Vimal Kumar, Adviser, FAUP, TIFAC

10:05 – 10:10•

About the Seminar by Professor, Anand Patwardhan, ED, TIFAC

10:10 – 10:20 • Address by Shri Jayant Kawale, CMD, MSEB, Guest of Honour

10:20 – 10:35• Keynote Address by Shri S.V. Sodal, Secretary, Irrigation (CAD),

Government of Maharashtra

10:35 – 10:45 • Presiding Address by Shri Yogendra Prasad, CMD, NHPC

10:45 – 10:55 • Inaugural Address by Shri Jeyaseelan, Chaiman, CWC

10:55 – 11:00 • Vote of Thanks by Shri V.V. Gaikwad, CE, Ghatghar Project

11:00 – 11:30 TEA / COFFEE BREAK

11:30 – 13:30 TECHNICAL SESSION 1: CONCEPTS

11:30 – 11:45 • Fly Ash in Hydro Sector – An Overview by Dr. Vimal Kumar

11:45 – 12:15 • RCC Dams – World Wide Experiences by Dr. Malcolm Dunstan

12:15 – 12:30 • RCC Design Aspects by Shri G.C. Vyas, CWC

12:30 - 12:40• Instrumentation in RCC Dams by Dr. V.M. Sharma, Former Director,

CSMRS

12:40 – 12:55• Quality Control aspects of RCC Dams by Shri S.B. Suri, Former

Director, CSMRS

12:55 – 13:15 • Discussions

13:15 – 14:15 LUNCH

National Seminar cumBusiness Meets


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AFTERNOON SESSIONMarch 4, 2005

14:15 – 15:45 TECHNICAL SESSION 2 : GHATGHAR CASE STUDY

14:15 – 14:25

• Introduction of RCC to Ghatghar project by Shri Jan. A. Struble,

Consultant , Patel Engineering

14:25 – 14:35• Suitability of Fly Ash for RCC by Shri D.M. More, Director General,

MERI, Nasik

14:35 – 14:45• Design & Layout consideration for Lower Dam by Shri P.R. Bhamare,

S.E., CDO, Nasik

14:45 – 14:55• Phoenixes from fly ash – 3 RCC dams for Ghatghar project by

Shri V.V. Gaikwad, C.E. Ghatghar Project

14:55 – 15:05• Ghatghar RCC dams mix design by Shri. V.V. Gaikwad, C.E.

Ghatghar Project

15:05 – 15:15• Quality Control at Ghatghar RCC Dams by Shri. V.V. Gaikwad, C.E.

Ghatghar Project

15:15 - 15:25 • Instrumentation in RCC: Ghatghar by Shri A.D. Solankurkar, TCE

15:25 – 15:35 • Importance of Thermal Study in deciding optimal utilisation of Fly Ashat Ghatghar Project by Smt. V M Bendre, Director CWPRS, Pune

15:35-16:00 • Discussions

16:00 – 16:30 TEA / COFFEE BREAK

16:30 – 17:30 TECHNICAL SESSION 3 : EXPERIENCES

16:30 – 16:40• Experience of APGENCO by Professor V.S. Raju, Former Director,

IIT, Delhi

16:40 – 16:45 • Experience of NPCIL by Shri S.G. Bapat, CE, NPCIL

16:45 – 17:15• Design and Construction of RCC dams – World Experiences by

Dr. Malcolm Dunstan

17:15 - 17:30 • Discussions

17:30 – 18:00 PANEL DISCUSSIONS

18:00 HIGH TEA

18:30 DEPARTURE FOR SITE VISIT

March 4-5, 2005

Site visit to Ghatghar Pumped Storage Scheme, Near Nasik


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FAUP4\Desktop\PapersPage:1

AS:VK

FLY ASH AND HYDRO SECTOR : INDIAN SCENARIO Vimal Kumar1, S.B Suri2, G.C Vyas3, K.S. Nagaraja4

S YNOPSIS

Fly Ash a residue of coal combustion in Thermal Power Station earlier considered as a

“industrial waste” is in fact a “resource material”. The concerted efforts in Mission Mode

over last decade have proved beyond doubt the versatility of fly ash for a large number of

gainful applications. It’s use in cement/ concrete, building components, mining sector,

agriculture, road construction and manufacture of high value added products have been

amply demonstrated and large scale utilization started.

The potential of fly ash to replace 25 to 50% cement in conventional concrete/ mortars and

upto 70% in roller compacted concrete, makes it an ideal material for hydro sector

constructions. The fly ash concretes are denser, durable, economical and eco-friendly.

The paper presents a birds eye view of (i) development of fly ash utilization scenario in the

country and (ii) the vast opportunities that exist in hydro-sector to drive benefits by use of fly

ash including its use in office/residential complexes and in construction of roads as well as

development of landscapes.

The views expressed are of the Authors and not necessarily of the organisations to which they haveaffiliation.

1. Dr. Vimal Kumar, Adviser (Flyash), TIFAC, DST, Government of India, New Delhi -110 016

2. Shri S.B. Suri, Ex-Director, Central Soil Material Research Station, Govt. of India, New Delhi - 110 016

3. Shri G.C. Vyas, Chief Engineer-Design (NWNS), Central Water Commission, Govt. of India, NewDelhi - 11016

4. Shri K.S. Nagaraja, General Manager, National Hydroelectric Power Corporation, Govt. of India,Faridabad – 121 003


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1.0 INTRODUCTION

India’s 85 utility and more than 25 captive Coal/ lignite based thermal power plants contribute

more than 70% of country’s total electric power generation. Due to vast coal reserves (about

211 billion tonnes), coal is being used as the largest source of energy. As a result of that India

is presently (2005) producing about 110 million tonne of ash every year. This figure is likely to

go up in view of developing nature of Indian economy, which involves large number of energy

intensive infrastructure projects. It is estimated that fly ash generation would increase to around

170 million tonne by 2012.

Fly ash is finely divided residue resulting from combustion of pulverised bituminous coal or sub

bituminous coal (lignite) in thermal power plants. It consists of inorganic mineral constituents of

coal and organic matter which is not fully burnt. It is generally grey in colour, alkaline and

refractory in nature and has a fineness 3000 to 6000 sq.cm. per gram and possess pozzolanic

characteristics. It has found wide acceptance for many applications across the globe including

in cement and concrete as well as for manufacturer of building materials, construction of road/

embankments and in agriculture/ horticulture.

The utilisation of fly ash in India was around 3 % of 40 million tonne annual generation during

1994, the year of formulation of Fly Ash Mission (FAM) of Government of India. As a result of

focused efforts alongwith various organizations, the utilisation has increased to 32 percent of

108 million tonne generation (2004) Hydro-Sector holds vast potential not only for use of fly ash

but to device technical, economical & economical advantages by it’s use.

The paper provides a birds eye view view of (i) development of fly ash utilization scenario in the

country and (ii) the vast opportunities that exist in hydro-sector to drive benefits by use of flyash.


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2.0 FLY ASH UTILISATION SCENARIO

2.1. Earlier Effects

Prior to 1994, large number of efforts have been made to develop and commercialise

technologies for use of fly ash. Academia, national research institutes, private R&D as well as

industry have been doing some work in this field even prior to 1960s. It was only around 1970s

that fly ash utilisation started getting attention may be due to increase in its generation volume.

Fly ash properties were researched for vide range of applications, inter alia, pozzolanic,

geotechnical, metallurgy, ceramic and agriculture applications. Scientific results were

published, laboratory trials and even a few field demonstrations were undertaken to

demonstrate the beneficial applications of fly ash. However, most of the work remained

confined within the academia / research arena. A few utilisations of fly ash were made

primarily in mass concrete, brick / block manufacturing and reclamation of low lying areas.

Ministry of Environment & Forests (MoEF), Ministry of Power (MoP) and a few other agencies

took initiatives. National Waste Management Council (NWMC) and a few other

groups/committees consisting of senior officials of various Ministries/Departments, State

Governments, Research and Development Institutions, Social Workers etc. were formed.

Thermal Power Plants were directed to take actions to enhance ash utilisations and a few fiscal

incentives such as concessional excise duty and sales tax were declared.

2.2 Commissioning of Fly Ash Mission

A well researched comprehensive techno-market survey report was prepared by Technology

Information, Forecasting and Assessment Council (TIFAC) of the Department of Science &

Technology, Government of India, during early 1990s for safe disposal and gainful utilisation of

fly ash. The report was widely distributed and discussed among concerned agencies. It

highlighted that only a meager percentage (less than 3 per cent) of ash was being utilised in

the country and the balance was being stored in ash ponds through slurry discharge system.

The report brought to fore that the fly ash that is being considered as a waste material, is in fact

a useful material and can be put to gainful economic applications.


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Appreciating the overall concern for environment and the need for safe disposal and gainful

utilisation of fly ash, the Government of India commissioned Fly Ash Mission during 1994 with

Department of Science & Technology (DST) as the Nodal Agency and Technology Information,

Forecasting and Assessment Council (TIFAC) as the Implementing Agency. The Mission

Mode Project is implemented in close association with Ministry of Power & Ministry of

Environment & Forests. The focus is on Technology Demonstration Projects for developing

confidence in fly ash technologies towards large scale adaptation.

The overall complexity of technology transfer, infrastructure support, inter-institutional linkages,

development of market, orientation of Government policies to promote and support fly ash

utilisation, are addressed. Further, as no single utilisation holds the potential to provide a

solution to this mammoth task of safe disposal and gainful utilisation of fly ash, a judicious mix

of a number of applications is evolved (considering impact timeframe, investment requirement,

technical and infrastructure inputs requirements by fly ash utilisation, potential and expected

returns, etc.). A number of disposal and utilisation technologies / applications have been

simultaneously demonstrated. Optimum technologies are facilitated to catelatize projects on a

wider / larger scale. The Fly Ash Mission has also created critical size of engineering teams for

each of the application / disposal areas to provide help for mass replication. The formulation ofnational standards and code of practices / guidelines is also addressed to for wider acceptance

and development on self sustaining principle.

The above said has been addressed through 55 Technology Demonstration Projects (TDPs)

indifferent areas of application of fly ash and spread through out the country. The projects are

taken with industry in close association of user agencies technology suppliers, fly ash producer

and experts from academia / R&D in ten THURST AREAS, viz, Utilisation of fly ashes: Roads

& Embankments, Building components, Hydraulic Structures, Agriculture Related Studies &

Applications, Application mining sector. Safe management of unutilized fly ashes: Ash

Ponds & Dams, Reclamation of Ash Ponds for Human Settlement Facilitation of further

work/utilization: Characterisation of Fly ash, Handling & Transportation, Research &

Development


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2.3 Impact Mode

2.3.1 The Paradigm Shift

The efforts over the last decade have made significant impact. The perception of fly ash has

turned around from a “waste material” to that of “resource material”. Its quite evident from the

fact that a meagre 3% utilistion of 40 million tonne of Fly ash generation in 1994 has risen to

32% of 108 million tonne generated in 2004.

The intrinsic worth of fly ash for various gainful applications is now being understood. It is

slowly being taken as a friendly and resource material than a liability. Further, good number of

entrepreneurs, scientists, engineers and user agencies have started coming forwards to work

in the area of fly ash utilisation / safe disposal. R&D institutions have started groups exclusively

working on fly ash.

The spread of ash utilisation over various applicants as it existed during 1994 and as its

development upto 2004 are presented below:

Utilisation Area – 2004(Total Utilisation – 32 MnT/Year)

1

2

3

4

56 7

8

1

2

3

4

5

6

7

8

Cement Manufacture / Substitution - 49%

Low Lying Area Fill - 17%

Roads & Embankments - 22%

Brick Manufacturing - 2%

Dyke Raising - 4%

Minefills - 2%

Agriculture - 1%

Others - 3%


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2.3.2 Networking

In addition to working with a large number of project execution agencies across the country for

technology demonstration projects, a network of 25 laboratories has been developed to provide

facilitation and guidance towards safe management / utilisation of fly ashes.

2.3.3 Training/ Experience Sharing Meets

Training & experience sharing meets including seminars, workshops & conferences are

organized / participated on a regular basis.

2.3.4 Standards

With an objective of wider acceptance and intitutionalisation of demonstrated technologies,

FAUP works very closely with Bureau of Indian Standards (BIS) & other agencies for therevision of the existing standards and preparation of standards for new products / utilisations of

fly ash. The end results include:

(a) Design guidelines for “Use of Fly ash in Road Embankments” have been approved and

issued by Indian Roads Congress.

1

2 3

1

2

3

Cement Manufacture / - 89% Substitution

Low Lying Area Fill - 10%

Brick Manufacturing - 1%

Utilisation Areas- 1994

Total utilisation∼

1MnT / year


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(b) Revision of IS 3812 – the standards for specification of fly ash for its use in cement / mortar

/ concrete & fine aggregate have been revised & issued by BIS in view of the

improvements in quality of fly ash over the years. These standards are now numbered asIS:3812 (Part-1):2003, IS:3812 (Part-2) : 2003 respectively.

(c) Revision of IS:456 – code of practice for plain and reinforced concrete has been revised

with use of fly ash.

(d) Minimum and maximum percentages of fly ash in PPC have been enhanced from 10% to

15% and from 25% to 35% respectively.

(e) Review of 45 standards of BIS and guide lines of CWC for hydro sector construction have

been recommended.

The following are a few examples of other policy directives / decisions in this area:

• CPWD has issued orders to all the zones to have atleast one construction using fly ash

bricks/ blocks etc.

• Notification has been issued by Ministry of Environment & Forests banning the use of top

soil for manufacture of bricks and construction of roads and embankments with in a radius

of 100 kms from a thermal power station.

• Use of fly ash based building materials has been made mandatory by MOEF with a time

schedule for achieving a given percentage usage in building construction.

• State Governments have commissioned “High Power Groups” to review & facilitate usage

of fly ash.

• A number of states (Orissa, Tamilnadu, Karnataka) have also announced fiscal and policy

incentives for fly ash based products.

• Central Government has granted excise & custom duty exemptions/ reliefs.

• Use of fly ash is to be explored and incorporated in DPR’s of hydro-Power Projects as

decided by Ministry of Power.

2.3.5 Multiplier Effects

The confidence building and awareness created by Fly Ash Mission through its technology

demonstration projects, workshops, seminars as well as association and support of other


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agencies has lead to a beginning towards acceptance of fly ash and its products. The

facilitation for large scale adaptation fly ash in various field projects is being provided in terms

of removal of mindset and other bottlenecks, availability of fly ash and up-dating / formulatingstandards codes, etc. More than 50 number of field projects have already been facilitated by

FAM/FAUP.

2.3.6 Industry Projects in Consultancy Mode

FAM / FAUP also provides expertise / technical support towards management/ resolving of

specific issues regarding safe management and utilization of fly ash. More than 35 consultancy

assignments from the industry have already been completed.

This part of the paper can be summarized that "As a result of recent concerted Mission Mode

effort over last decade, the fly ash utilisation scenario in India, has turned around and is set on

a path of faster growth".

3.0 USE OF FLY ASH IN HYDRO SECTOR : INDIAN SCENARIO

Fly ash and other pozzolana have been used in mass concreting since immemorial, primarily

to address the heat of hydration. However, of late, it has been realized that use of fly ash

provides many more advantages. It makes concrete denser, durable, economical & eco-

friendly; as well as faster construction, if Roller Compact Concrete (RCC) is used. The

economies comes through lower consumption of cement, saving in chilling cost & faster

construction.

3.1 Recent Initiatives

3.1.1 The use of fly ash in cement and concrete has got well established in the country over

last 10 years, especially, as a result of focused thrust imparted by many agencies

along with Fly Ash Mission (FAM) / Fly Ash Utilisation Programme (FAUP), TIFAC,

DST. The permissible percentage of fly ash content in PPC has been increased from

25 per cent to 35 per cent, minimum content of fly ash in PPC has also been increased


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from 10 per cent to 15 per cent; use of fly ash in concrete is now accepted as a quality

improvement measure and the fly ash content is accounted in the concrete

composition with respect to the cement content.

3.1.2 The first ever Roller Compacted Concrete (RCC) dams (2 numbers) have been

constructed at Bhandardara near Nashik in the state of Maharashtra under Ghatghar

Pumped Storage Scheme of Irrigation Department, Government of Maharashtra. The

2 dams that have been constructed with RCC replacing 65% of cement with fly ash are

Saddle Dam and Upper Dam. The decision to construct these dams with RCC was

taken by Government of Maharashtra during 1994 at the instance of Fly Ash Mission,

TIFAC, DST to make these dams as the Technology Demonstration Projects

supported by Fly Ash Mission, TIFAC, DST to the extent of adaptation of RCC

technology. The Upper Dam which is 14.5 meter high, 451 meter long and has been

constructed with 35576 m3 of concrete. The corresponding figures for Saddle Dam are

11.50 meter, .288 meter, 14210 m3. The above said two dams have been constructed

with RCC technology with large doses of fly ash with association of a number of

agencies, like, Government of Maharashtra, Fly Ash Mission / FAUP, TIFAC,DST;

Central Water Commission; CSMRS, New Delhi; University of Roorkee (now known as

IIT-Roorkee); MERI-Nashik; CDO, Nashik; CWPRS-Pune; Tata Consulting engineers-

EPDC (Japan), ASI (USA), Malcolm Dungstan & Associates (UK) and M/s. Patel

Engineering Limited, Mumbai, etc. This has given a good amount of confidence to the

engineers and the decision makers in the country. As a result, Irrigation Department,

Government of Maharashtra is undertaking construction of lower dam 86 meter high,

415 meter long with 6,00,000m3 concrete construction adapting the same RCC

technology and mix design has developed and used in the construction of Upper Dam

and Saddle Dam, the Technology Demonstration Projects of RCC technology under

Fly Ash Mission, TIFAC, DST.

The confidence built has developed interest of many agencies for construction of dams

with RCC technology to harness the benefits such as: denser and durable concrete,

faster construction, economical and eco-friendly construction etc.


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3.1.3 APGENCO is undertaking construction of Srisailam Dam with RCC technology and is

considering adaptation of the same technology for construction of Tail Pond Dam for

Nagarjuna Sagar Pumped Storage Hydroelectric Scheme. NHPC, TATA Power andGreater Mumbai Corporation are also planning dams with RCC technology.

Government of Gujarat is considering use of RCC technology for rehabilitation of

dams.

3.1.4 Shri R.V. Shahi, Secretary, Ministry of Power, Government of India appreciating the

vast potential that hydro sector has for utilisation of fly ash as was presented by FAUP

in a meeting convened by him on the subject, constituted a Technical Group for gainful

utilisation of fly ash in the hydro power and hydro resources sector. The TechnicalGroup has reviewed 45 Standards of BIS and CWC Guidelines relevant to construction

in these two sectors for appropriate incorporation of fly ash and its products towards

large scale utilisation in these sectors.

As recommended by the Technical Group to the Ministry Power, it has been decided

by the Ministry of Power that all hydro-power project DPRs, henceforth, would include

a chapter on Use of Fly Ash. The utilisation of fly ash is to be explored and

incorporated from the initial stages of material investigations. As far as possible, fly

ash is to be used in all projects to harness its benefits.. The impediments, if any

whether technical or logistics are to be addressed and if required the assistance and

guidance / help of Fly Ash Utilisation Programme, TIFAC, DST may be taken. Central

Electricity Authority (CEA) is implementing the decision. CWC is also proposing to

take a similar decision for water resources projects.

3.1.5 The large scale utilisation of fly ash in hydro sector especially in remote areas needs to

be facilitated with logistics and the supply chain. Regular supply of consistent quality

fly ash needs to be ensured. The ash producing agencies and Fly Ash Utilisation

Programme have already started working on this aspect. Ministry of Power has

directed all thermal power plants to install facilities to ensure availability of dry fly ash

on regular basis and of consistent quality. About 50% of power stations have already


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established the dry fly ash collection and supply system. Most of the balance power

stations have made temporary arrangements for making available the dry fly ash till

regular systems are put in place.

3.1.6 IS:3812 of BIS regarding specifications of fly ash for use in cement / concrete has also

been revised by FAUP and issued by BIS after due processing / approvals. The

revised standard IS:3812, Part-1 : 2003 provides for supply of IS marked fly ash.

3.1.7 The Government has drawn up an ambitious plan to add 50,000 MW of hydro-power

as well as a large number of water resources sector projects to be implemented by the

end of next 5 year plan. DPRs have been prepared for most of the projects. CEA,

CWC, NHPC, NEEPCO and other agencies including state agencies have drawn up

the implementation plans.

3.1.8 With the above said developments the industry looks ahead to the vast potential of use

of fly ash in hydro sector. To facilitate the regular supply of fly ash of required quality,

more than 20 agencies have come up at different power stations for collection and

supply of fly ash to end users. This segment of fly ash industry is fast developing, the

latest example being, conversion of wet ash collection system of Dahanu Thermal

Power Station (DTPS) into 100% dry collection system with a classifier and bagging

unit. The system has been set up under technical design advise of FAUP, TIFAC and

is under commissioning.

3.2 Hydro-Sector Areas for Fly Ash Utilisation

Hydro sector projects have a large number of construction activities. An attempt is made in the

following paragraphs to highlight the vast opportunities that exists in hydro sector for use of fly

ash.

3.2.1 Mass Concrete

Mass concrete is one of the first types of concrete in which fly ash was used in India.

Today, there are few mass concrete dams built in any part of the world that do not

contain fly ash or some other type of pozzolana in the concrete.


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3.2.1.1 Partial Re-placement of Cement

Generally the replacement of cement by fly ash at site has been to the extent of about

15 to 20 percent by mass in cement mortar and concrete, the typical examples of such

applications being as follows:

S.No. Structure State CementReplacement

(%)

Source ofFly Ash

1. Gurgoan Canal Haryana 15 Delhi 'C'

2. Jawahar Sagar Dam Rajasthan 20 Delhi 'C'

3. Kakki Dam Kerala 20 Neyveli

4. Narora Barrage U.P. 15 Harduaganj

5. Rihand Dam U.P. 15 Bokaro

6. Sone Barrage Bihar 15 Bokaro

7. Umium Project Assam Not available Durgapur

8. Chandil Dam Bihar 25 Talcher

Adoption of fly ash for part replacement of cement (one to one basis) suits only situations

such as mass concrete in river valley projects where long term strength governs the designof the concrete mix. Fly ash concretes can also be designed to give strengths equal to that

of neat cement concretes at early ages by overdosing the fly ash content suitably.

Preliminary Draft Indian Standard IS:457 (1) provides that fly ash normally may be used in

mass concrete upto 35% of the total cementing materials by absolute volume. By using fly

ash in concrete in massive dam construction, it is possible to achieve a reduction of the

temperature rise without incurring the undesirable effects associated with very lean mixes

viz. harshness, bleeding, tendency to segregation and increased permeability. In addition,

use of fly ash can reduce the thermal stresses by the reduction of the heat of hydration in

mass concrete structures. Improved sulphate resistance & alkali-aggregate reaction

resistance provided by proper incorporation of fly ash into concrete mixes are other

important considerations for incorporation of fly ash in concrete in the construction of

massive concrete dams. FIP (Federation Internationale De la Precontrainte) (2) has

proposed that for the prevention of alkali-aggregate reaction in concrete, not less than 25%


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of Portland cement must be replaced by fly ash. Also, as per BS 3892:Part 1:1982 (3),

where there are circumstances in which alkali-silica reactivity needs to be considered, the

use of pulverised fuel ash (at least 30%) may be beneficial. According to Malvar, L.J. et al.(4), to prevent ASR, it is recommended to include a cement replacement of 25 to 40%

class F fly ash (or class N pozzolana). The class F fly ash should have a maximum 1.5%

available alkali, a maximum 6% loss on ignition(3% would be better), and a maximum 8%

CaO (upto 10% CaO if a minimum replacement of 30% is used). Use of fly ash for

combating alkali-silica reaction is helpful both in the case of mass concrete as well as

structural grade concrete.

3.2.1.2 Tunnel Lining

In Nathpa Jhakri Project (5), when excavation of head race tunnel had proceeded about 1

Km downstream of Wadhal adit, sudden inflow of hot water was encountered on 15th

January, 1995. Temperature of seepage water was about 52 deg.C & total seepage water

was around 100 Litres/sec. Extensive study on seepage water was carried out by CSMRS,

New Delhi both at site and in the laboratory and it was found that not only the hot water but

also the normal (cold) water in the adjoining reaches contained chemicals aggressive to

concrete lining. Cementitious content of 420 Kg/m3 with 30% of fly ash by mass was used

in M 20 A 40 concrete mix for ensuring durability of the tunnel lining concrete.

Fly ash can also be used in concrete for tunnel lining and cement grout for backfill

grouting, pressure (consolidation) grouting and contact grouting.

3.2.1.3 Predominantly Fly Ash Mortars and Concretes

G. Ramakrishna et al. (6) from Andhra Pradesh Engineering Research Laboratories,

Hyderabad indicated that the addition of fly ash to a degree of 180 & 150 percent in leanand rich mortars may result in saving of cement content to the extent of about 44 and 21

percent, with a reduction in material cost per cubic metre of about 22 and 24 percent,

respectively.


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The work reported by Mather (7) on the use of pozzolana in large quantities has also

revealed that considerable reduction in cement can be achieved in lean mass concrete. A

typical mix studied by him contained 55.8 Kg/m3

of cement and 118.7 Kg/m3

of fly ash andhad developed a compressive strength of about 215.8Kg/cm2 at an age of 90 days,

whereas the control mix with 112.1 Kg/m3 cement and no fly ash had developed a

compressive strength of only 149.8 Kg/cm2 at the same age. It was further reported that a

very lean mass concrete containing 42.1 Kg/m3 of cement & 76.6 Kg/m3 of calcined shale

(Pozzolana) with a one year field strength of 187kg/cm2 was used in the construction of

John Day Lock and Dam of the U.S. Army Corps of Engineers. From the investigations and

examples quoted above, it may be seen that substantial economies in cement, particularly

in lean mass concrete, where high strengths are not required and the design strengths areto be achieved only at the age of one year or later, can be realised by using large

quantities of pozzolana as admixture instead of the usual practice of replacing only 20 to

30 percent of cement by pozzolana. Studies conducted by Central Soil and Materials

Research Station (CSMRS), New Delhi have confirmed the findings of Mather. The

experiments carried out by CSMRS (8) indicated that a fly ash mortar with 100Kg/m 3 of

cement and 200Kg/m3 of fly ash can develop a compressive strength of about 120 Kg/cm2

at an age of 120 days, & a strength of about 170 Kg/cm2 at an age of one year. This mortar

mix had a water content of about 250Kg/m3. In lean mass concretes, it was found feasible

to economise in cement content substantially (upto about 60 to 70 percent) by using large

quantities of fly ash when strengths are matched at 90 days and beyond.

Available procedures for proportioning concrete with large fly ash contents tend to be

rather elaborate. Iqbal Ali (9) has, therefore, proposed a more generalised and simpler

approach for design of predominantly fly ash mortars, corresponding to a flow of 100%

since it simulates the consistency of mortar normally used for masonry construction, as

well as the consistency of the mortar component of concrete with medium workability.

3.2.1.4

Use of Fly Ash in Portland Pozzolane Cement

Portland pozzolana cement produces less heat of hydration and offers greater resistance

to the attack of aggressive waters than normal Portland cement. Moreover, it reduces the


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leaching of calcium hydroxide liberated during the setting and hydration of cement. It is

particularly useful in marine and hydraulic construction and other mass concrete

structures. Portland pozzolana cement can generally be used wherever 33 grades ordinaryPortland cement is usable under normal conditions. The use of fly ash for manufacture of

Portland pozzolana cement (PPC) is an accepted practice. Keeping in view the special

needs of the water resources sector, the Bureau of Indian Standards brought out a

separate Code IS: 14 89 (Part-1) :1991 (10) for Portland pozzolana cement incorporating

fly ash only, on the lines of the British Standard Specification for pozzolanic cement with

pulverised fuel ash as pozzolana viz. BS 6610: 1985 (11). In this Code, the proportion of

pulverised fuel ash is not more than 50% nor less than 35% by mass of total quantity,

against the present provision in IS:1489 (Part-1): 1991 that fly ash conforming to IS:3812(part-1)-2003 ranging from 15 to 35% by weight of cement can be used in the

manufacture of PPC.

For construction of structures using rapid construction methods like slip form construction,

Portland pozzolana cement should be used with caution since 4 to 6 hours strength of

concrete is considered significant in such construction.

3.2.1.5

Use of Fly Ash in RCC Works

As per clause 5.2.1.1 of IS:456-2000 (13), fly ash conforming to IS: 3812(part-1)- 2003

may be used as part replacement of ordinary Portland cement in RCC works provided

uniform blending with cement is ensured. Central Water Commission now also permits the

use of either Portland pozzolana cement (fly ash based) or part replacement of ordinary

Portland cement by fly ash in structural grade concrete for all hydraulic structures. Massive

columns in the case of surface power houses are a typical example of mass reinforced

concrete work. Central Public Works Department, New Delhi (14) has also recently

permitted the use of fly ash as part replacement of cement in RCC works where concrete

is obtained from RMC manufacturers for large projects as per guidelines given below:

(i) RCC in Foundation: Part substitution of ordinary Portland cement by dry fly ash may be

allowed in structural concrete obtained from ready mixed plants (IS: 4926-2003) of all

grades in pile foundations and other foundations e.g. raft etc.


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(ii) RCC superstructures: The part replacement of ordinary Portland cement by dry fly ash

may be allowed in structural concrete obtained from ready mixed concrete plants (IS:

4926-2003) for structures above ground including structures within 30 cms of groundlevel having cement concrete of M30 & higher grade.

(iii) Pre-stressed Concrete Structures: The part replacement of ordinary Portland cement

by dry fly ash may be allowed in pre-stressed concrete structures except for bridges

and flyovers.

The cement quantity to be reduced can be limited to 60% of the quantity of fly ash

being added. However, the substitution is not allowed in concrete subjected to severe,

very severe and extreme exposure conditions.

In view of the above notification issued by CPWD, appropriate amendment is required

in IS:1343-1980 (15) for use of Portland pozzolana cement conforming to IS: 1489

(Part-1)-1991 (fly ash based) in prestressed concrete.

3.2.2 Earth Dams

Based on assessment of geo-technical parameters and techno-economic

considerations, fly ash conforming to IS:3812(part-1)-2003 can be utilised in selected

zones in the downstream casing, especially downstream of filter zone.

The upstream slope protection of earth dams can be ensured by the use of fly ash

based concrete blocks.

3.2.3 Shotcrete/ Gunite

In shotcreting, either Portland pozzolana cement conforming to IS: 1489 (Part-1) -1991

or fly ash conforming to Grade-1 of IS: 3812(part-1)-2003 for part replacement of

ordinary Portland Cement can be used in the pneumatically applied concrete /mortar.

This material can be beneficially used for guniting the upstream face of masonry dams

and for stabilizing rock slopes. Fly ash can also be used in shotcrete for underground


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structural support by ensuring compatibility between admixtures and cement-fly ash

combinations.

3.2.4 Diaphragm Walls for Under-Seepage Control

Either Portland pozzolana cement conforming to IS: 1489 (Part-1)-1991 (Fly ash

based) or fly ash conforming to Grade-1 of IS:3812(part-1)-2003 can be used in the

concrete mix for rigid type of diaphragm walls and in plastic concrete for flexible type of

diaphragm walls for dams, weirs and barrages.

3.2.5 Canals

Either Portland pozzolana cement conforming to IS: 1489 (Part-1)- 1991 (Fly ash

based) or fly ash conforming to Grade-1 of IS: 3812(part-1)-2003 can be used in canal

works in the following situations/materials/structures:

(i)

Burnt Clay Tiles Lining

Cement mortar for subgrade, mortar for tile masurry, Sandwitch cement sand

plaster, cement sand plaster over the layer of tiles in single tile lining in bed,

cement concrete at the junction of bed lining & slope lining, cement concretecoping, etc.

(ii) Insitu concrete lining, cement mortar/ concrete in brick/concrete sleepers

under the joints.

(iii) Precast concrete tiles, masonry mortar for laying of precast concrete tiles /

stone slab/masonry stone lining.

(iv) Brick Lining for water courses and field channels

Use of burnt clay fly ash building bricks or pulverised fuel ash-lime bricks in

place of common burnt clay building bricks.Masorry mortar, cement plaster,

M10 Grade concrete lining in bed over 100 microns LDPE film, M 10 Grade

concrete lining in walls.

(v) CLC Tiles for canal lining : Cellular lightweight concrete (CLC) tiles are

manufactured in nominal standard size of 500X500X 75/50 mm in fly ash


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based CLC of density 1,650 Kg/m3. This density ensures 28 days compressive

strength of around 200Kg/cm2. The CLC mix used for precasting is reinforced

with optimum quantity of quality polypropylene fibres to enhance the variousperformance characteristics of the finished tiles. The design of the tile is such

that it has plain surface on the top side and a depressed waffle conctruction on

the backside. The tiles have an inbuilt tongue and groove provision on edges,

which would enable dry joining of tiles feasible. The joints between tiles on

water face are sealed with an acrylic based sealant applied with a gun. Fly ahs

content is to an extent of over 25% of total dry ingredients (16).

(vi) Prestressed concrete, RCC or masonry or a combination of these materials for

construction of syphon barrels.(vii)

Top cover of precast concrete tiles, insitu cement concrete, stone slabs or

bricks over polyethylene film lining.

(viii) Superpassages, Aqueducts and Outlets

(ix) Soil-cement- fly ash lining in place of soil-cement lining.

(x)

Syphon Aqueducts

(xi) Canal structures(xii) Lime concrete lining using all classes of lime from A to E and fly ash(xiii) Based on assessment of geo-technical parameters and techno-economic

considerations, fly ash conforming to IS:3812-1981 can be used for the repairs

of unlined canal embankments and for the maintenance of canal banks, roads

and ramps in the case of lined canals.

3.2.6 Construction and Maintenance of River Embankments (Levees)

In case of zoned embankments, after assessment of the geotechnical parameters of

fly ash and based on techno-economic considerations, fly ash conforming to IS:3812-

1981 can be used in selected zones of the embankments on the country side beyond

downstream filters.

Pond ash conforming to IS: 3812-1981 can be used as backfill material.


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Fly ash concrete blocks can be used for rip rap of the embankment. Fly ash to the

extent of 35 % by weight of cementitious material can be used for casting insitu,

colcreting or precasting of concrete blocks.

3.2.7 Curtain Grouting and Consolidation Grouting of Rock Foundations.

In cement grout for pressure grouting of rock foundations in river valley projects, fly ash

conforming to grade of IS:3812(part-1)-2003 for part replacement of ordinary Portland

cement or as Portland pozzolana cement conforming to IS:1489 (Part1)-1991 in place

of ordinary Portland cement can be used. In case early strength is important in the

grouting job, fly ash may be considered to behave as an inert non-cementing filler.

3.2.8 Surface Hydroelectric Power Stations

Fly ash conforming to grade 1 of IS: 3812(part-1)-2003 for part replacement of cement

or as Portland pozzolana cement can be used in concrete for construction of the

substructure including foundation, intermediate structure including spiral casing and

generator support, superstructure including roof, auxiliary rooms etc.

3.2.9 Relief Wells for Earth Dams on Pervious Soil Foundations

In the masonry for construction of masonry wall with cover around the relief well, burnt

clay fly ash building bricks and pulverized fuel ash-lime bricks can be used in place of

common burnt clay building bricks & stones. For masonry mortar, Portland pozzolana

cement (Fly ash based) can be used.

3.2.10 Grouting of Pervious Soils

For grouting of pervious soils for control of seepage, cement and fly ash or Portlandpozzolana cement in place of ordinary Portland cement can be used, depending upon

grout- ability of the strata based on grain size distribution.


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3.2.11 Grout Curtains for Earth, Rockfill, Masonry and Concrete Gravity Dams

In grout curtains in alluvium and rock when used as principal measure of seepage

control, fly ash may be used both as a filler and as an admixture and in both the

instances, it will produce cementitious properties in the grout mix when the finely

divided siliceous residue reacts chemically with ordinary Portland cement. The

maximum amount of fly ash should not exceed 35% of the ordinary Portland cement by

weight or Portland pozzolana cement can be used in place of ordinary Portland

cement.

3.2.12 Concrete and Masonry Barrages

Part substitution of ordinary Portland cement by fly ash or use of Portland pozzolana

cement can be adopted for all concrete works and masonry mortar.

In case ordinary Portland cement is used for casting insitu, colcreting or precasting of

concrete blocks, it can be replaced by fly ash to the extent of 35% by weight.

Pond ash can be used as backfill material.

3.2.13 Concrete Structures for the Storage of Liquids

Portland pozzolana cement conforming to IS:1489 (Part-1)-1991 can be used for

construction of concrete structures, plain, reinforced or pre stressed concrete, for

storage of water.

3.2.14 Self-Compacting Concrete

Recently self-compacting concrete has been developed in Japan (17). This concrete

requires more fines content as compared to normal concrete. Large volumes of fly ash,

partially to substitute cement and partially as filler, can be used to produce self-

compacting concrete. In Italy, such concrete is being produced in ready mixed

concrete plants. Typical M40 grade concrete with high fly ash content (45-60%)

alongwith super-plasticizer and a modified cellulose-based viscosity modified

admixture (VMA) has been produced. The super-plasticizers used were polycarboxylic


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ether polymer based. Such concretes have high workability, slump in the range of 200-

220 mm, but at the same time cohesive and non-segregating. This concrete can be

used for tunnel lining & concreting of structures at inaccessible locations, especially inthe context of power house concreting.

3.2.15 Roads & Embankments

3.2.15.1 Ash can be used in the following applications:

• Core fill material for road/rail embankment construction

• As reinforced fill material

• Stabilization of soil sub-grade

• Sub-base/base course of flexible pavements

• Construction of semi-rigid/rigid pavements

3.2.15.2 Indian Roads Congress (IRC) had brought out special publication No.58

in March, 2001 for use of ash in road embankments. Ministry of Road

Transport & Highways has directed NHAI & state PWDs to include use

of ash in their specifications of road construction. IRC has also brought

out Rural Road Manual under PM's Gramin Sadak Yojana which

provides for use of ash in road works (18).

3.2.15.3 The design of fly ash embankment is similar to earthen embankment

(18). Salient features of IRC-SP: 58 are mentioned below:

• For embankments of height upto 3m, core of embankment is to be

constructed with pond ash as fill material

• For embankments of height more than 3m, intermediate soil layers

of minimum 200mm thickness are to be provided. The vertical

distance between such layers may vary from 1.5 to 3m.

•

Side cover of 1 to 3m is to be provided as ash is easily erodable.


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3.2.15.4 Advantages of using ash in road construction are listed below (18):

•

Lower density than earth resulting in lower overburden pressure,

advantageous in weak / clayey subsoil.

• Hardly any measurable settlement over time due to low

compressibility of compacted ash.

• Speed of construction is faster as it can be compacted in wide

range of moisture content.

• Work can be taken up even in rainy season due to quick draining

properties of loose ash.

• Assured availability of ash free of cost.

• Eco-friendly since it replaces soil being borrowed from agricultural

lands.

3.2.15.5 Fly Ash Admixed Concrete for Pavements (19)

Fly ash admixed concrete can be used for constructing rigid pavements in

many ways. These include dry lean fly ash concrete/lean cement fly ash

concrete (IRC 74), fly ash cement concrete pavements, fly ash admixed

concrete paving blocks, roller compacted concrete, etc. Judicious use of fly

ash as on admixture goes a long way in construction of durable concrete

roads.

3.2.15.6 Use of Triple Blend Technology (20)

India is now producing concrete of over 80 MPa compressive strength.

Designs are being produced with concretes of grade M 60, M 65, M 70 &

higher. The use of triple blends, Portland cement, fly ash & silica fume, can

give concretes of high strength and very low permeability. Such concretes

are ideal for use in stilling basins, plunge pools etc.


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3.2.15.7 Concrete Masonry Units

Fly ash also be utilised in large quantities in the manufacture of building

blocks for the housing colony of the project. IS: 2185 (Part 1 to 3) (21,22,23)

permit use of fly ash in case of hollow and solid concrete blocks, hollow and

solid light-weight concrete blocks and autoclaved cellular aerated concrete

blocks, respectively.

3.3 Conclusion

The awareness of fly ash applications, especially in cement & concrete area, directly

relevant to hydro-sector projects is fast 'gaining acceptance in India'. In addition to use

of fly ash in mass concrete, Roller Compacted Concrete & other hydro-structures, the

hydro sector holds vast potential to use fly ash & its products in construction /

development of office / residential complexes, roads, land development & horticulture

works etc.

The recent developments including policy initiatives / directives of the Government and

actions by industry signal a positive move toward harnessing the potential of beneficial

use of fly ash in hydro sector. It needs to be pursued & implemented.


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REFERENCES

(1) IS:457 Preliminary Draft Indian Standard 'Code of Practice for Plain & Reinforced Concrete for

Dams & Other Massive Structures' (First Revision of IS:457)

(2) Sudhindra, C., Suri, S.B. & Nair, K.N., "Strained Quartz – A Menace for Durability of Concrete

for Hydraulic Structures", International Symposium New Materials & Techniques in Dam

Construction, 5-7 March, 1987, Central Board of Irrigation & Power, Madras.

(3) BS:3892 - Part-1:1982, "British Standard Pulverized Fuel Ash for Use as a Cementitious

Component in Structural Concrete".

(4) Malvar, L.J., Cline, G.D., Burke, D.F., Rollings, R., Sherman, T.W. & Greene, J.L., "Alkali -

Silica Reaction Mitigation : State of the Art & Recommendations", ACI Materials Journal,

September-October, 2002, pp.480-489.

(5) Singh, Ranjodh, "Use of Fly Ash in Production of Concrete for Tunnel Lining in Nathpa Jhakri

Project – A Case Study", National Seminar on Utilization of Fly Ash in Water Resources Sector,

Proceedings, 11 & 12 April 2001, CSMRS, New Delhi, pp.167-172.

(6) Ramakrishna, G., Oshman Ahmed, M. & Yadav, T., "Utilisation of Large Quantities of Fly Ash in

Concrete & Mortar Mixes", Proceedings, Forty Eighth Research Session of Central Board of

Irrigation & Power, Hyderabad, 11-14 March 1980, Vol.III (Soil & Concrete), pp.69-95.

(7) Mather, B., "Use of Concrete of Low Portland Cement Content in Combination with Pozzolana

& Other Admixtures in Construction of Concrete Dams", Journal of the American Concrete

Institute, Proceedings, Vol.71, No.12, December, 1974, pp.589-599.

(8) Melkote, R.S. & Bhanuprasada Rao, P., "Large Economies through Predominantly Fly Ash

Concretes & Mortars", Proceedings, Forty Fifth Annual Research Session of Central Board of

Irrigation & Power, Hyderabad, June, 1976, Vol.III (Soil & Concrete), pp.81-95.

(9) Iqbal Ali, "Fly Ash Makes Cement Go Farther", All India Seminar on Cement Manufacture,

January 19-21, 1981, Vol.III, organised by Cement Research Institute of India.

(10) IS:1489 (Part-1) – 1991, "Specification for Portland Pozzolana Cement, Part-1, Fly Ash Based",

(Third Revision), (Amendment No.3).

(11) BS :6610 : 1985, "British Standard Specification for Pozzolana Cement with Pulverized – Fuel

Ash as Pozzolana".


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(12) IS:3812(part-1)-2003, "Specification for Fly Ash for Use of Pozzolana & Admixture", (First

Revision).

(13) IS:456-2000, "Code of Practice for Plain & Reinforced Concrete", (Fourth Revision).(14) Circular No.CDO/SE(RR)/Fly Ash (Main)/387 dated May 13, 2004 issued by Central Designs

Organisation, Central Public Works Department.

(15) IS:1343-1980, "Code of Practice for Prestressed Concrete", (First Revision), (Amendment

No.1).

(16) Kadkade, D.G. & Singh, G.B., "Tiles of Fly Ash Based Cellular Lightweight Concrete for Canal

Lining", National Seminar on Utilization of Fly Ash in Water Resources Sector, Proceedings, 11

& 12 April, 2001, CSMRS, New Delhi, pp.265-274.

(17) Maiti, S.C., "Advances in Concrete Materials", NBM & CW, August, 2003, pp.77-82.(18) Mathur, A.K., "Overall Scenario of Fly Ash Production & Government Initiatives", Training

Programme on Use of Fly Ash in Construction Practices, 21-23 April, 2004 organised by

National Council for Cement & Building Materials, Ballabgarh.

(19) Sikdar, P.K., Kumar, Satendar & Guru Vittal, U.K., "Uses of Fly Ash in Plain & Reinforced

Concrete Pavements", National Seminar on Utilizaion of Fly Ash in Water Resources Sector,

Proceedings, 11 & 12 April, 2001, CSMRS, New Delhi, pp.150-156.

(20) Lewis, Robert C., "Improved Performance & Durability Through the Combined Effects of Fly

Ash & Micro-silica", National Seminar on Utilization of Fly ash in Water Resources Sector,

Proceedings, 11 & 12 April, 2001, CSMRS, New Delhi, pp.234-242.

(21) IS:2185 (Part-1)-1979, "Specification for Concrete Masonry Units : Part-1 Hollow & Solid

Concrete Blocks", (Second Revision) (Amendment No.1).

(22) IS:2185 (Part-2) -1983, "Specification for Concrete Masonry Units : Part -2 Hollow & Solid Light

Weight Concrete Blocks", (First Revision).

(23) IS:2185 (Part-3) – 1984, " Specification for Concrete Masonry Units : Part -3 Autoclaved

Cellular Aerated Concrete Blocks", (First Revision).

(24) Vimal Kumar and Chandi Nath Jha "Multifarious Applications of Fly Ash Mission Mode

Approach", Fly Ash Mission, Proceedings of 'Workshop on Utilization of Fly Ash' at University of

Roorkee, April, 1998.

(25) TIFAC "Techno Market Survey on Fly Ash Bricks", 1995

(26) TIFAC "Techno Market Survey on Fly Ash Pre-fabrications technologies and market"


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(27) Vimal Kumar, B.K. Rao & Preeti Sharma "Fly Ash as Raw Material", Fly Ash Mission,

proceedings of International conference at CBIP, New Delhi, January, 1998.(28) Vimal Kumar, B. K. Rao & K.A. Zacharia "Fly Ash : Techno Economic Viability", Fly Ash

Mission, proceedings of International Conference at CBIP, New Delhi, January, 1998.

(29) Vimal Kumar, C N Jha, P Sharma “Fly ash – A Fortune for the Construction Industry”, New

Delhi, 1999.

(30) Vimal Kumar, P Sharma, Mukesh Mathur “Fly Ash Disposal: Mission beyond 2000 A.D.”, Fly

Ash Disposal and Deposition: beyond 2000 A.D. New Delhi, 1999.

(31) “Fly Ash Management – Vision for the New Millennium”, Second International Conference on

Fly Ash Disposal & Utilisation, New Delhi, February 2000.


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DESIGN ASPECTS OF ROLLERCOMPACTED CONCRETE DAMS

Er. G.C. Vyas1 Er. P.K. Saxena2 Er. Darpan Talwar 3

ABSTRACT

The Roller compacted concrete dams (RCC) have gained world wide acceptance in

relatively short time of a few decades due to their low cost and rapid method of

construction. Over 266 RCC dams located in at least 38 countries have been/are

being constructed (up to Dec 2002). RCC dams are broadly classified into four

categories according to percentage of cementitious material content in the concrete

mix. Majority of dams constructed have fly ash as cementitious material. Simplicity

of overall planning and design of appurtenant works will have a significant effect on

desired benefits of a RCC dams. The design philosophy of gravity dam using RCC is

fundamentally similar to concrete dams. However, there are certain aspects of designwhich are peculiar to RCC dams. The number of joints between the relatively thin

layers and related quality control can have a large influence on the over all stability of

a dam in terms of uplift water pressure, tensile and shear (cohesion) strength at the

joints between layers. This paper illustrates design aspects as well as instrumentation

to be adopted for RCC dams.

INTRODUCTION

The roller compacted concrete (RCC) dams have by now emerged as a viable

alternative to concrete gravity dams; they have gained worldwide acceptance in a

relatively short time in a few decades due to their low cost and rapid method of

construction. More than 266 RCC dams located in at least 38 countries including

India have been constructed or are being constructed till date.

While, the majority of the RCC dams built are gravity dams, recently arch and arch

gravity dams using RCC are also coming up.

The design of a gravity dam using the RCC is fundamentally no different from the

design of conventional concrete gravity dam. However there are certain aspects of

design which are peculiar to RCC dams. These and other considerations are discussed

in the subsequent paras.

CURRENT DESIGN CONCEPTS

About 266 RCC dams have been constructed or being constructed so far. In majorityof RCC dams constructed, fly ash has been used as a mineral admixture/ cementitious

material in conjunction with cement to produce concrete which has a lower heat of

hydration. The RCC dams are broadly classified into four categories based on the

cementitious material content (cement and mineral admixture) as shown in table-1.

1 Chief Engineer (Designs), Central Water Commission, New Delhi

2 Director, Hydel Civil Design, Central Water Commission, New Delhi3 Deputy Director, Hydel Civil Design, Central Water Commission, New Delhi


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TABLE 1

Classification Low

cementitious

content RCC

RCD Medium

cementitious

content RCC

High

cementitious

content RCC

cementitious

content (kg/m3)

< 99 120 - 130 100 -149 >150

Mineral

admixtures

content (%)

0 - 40 20 – 35 20 - 60 30 - 80

Lift/Layer

thickness (mm) +300 750 - 1000 +300 +300

Transverse Joint

spacing ( ‘m’)30 - α 15 15 - 50 20 - 75

Typical

examplesWillow Creek

Concepcion,

Jordao

Shimajigawa

Tamagawa

Miyagase

Copperfield

De Mist Kraal

Les Olivettes

Upper Still

Water Santa

Eugenia

Platanovryssi

Although the above classifications are based on the cementitious content, each

category has slightly different philosophy towards the design and construction of

dams.

The low cementitious RCC dam uses upstream watertight membrane to reduce the

seepage through the body of the dam particularly at the joints between the layers.This membrane can either be a concrete facing (up to 500 mm wide) placed at the

same time as the interior concrete and cast against conventional formwork, pre-cast

concrete panels with or without an attached geo-membrane. Bedding mixes (concrete

or mortars with higher cementitious contents) are frequently placed between each lift

near the upstream face to improve and reduce the seepage between the layers of RCC.

The RCD method is used in Japan. The final structure is similar to traditional gravity

dam with 15 m wide monoliths, although these are post-formed by cutting the joints

as opposed being preformed with form work. The method of construction is 10 to 15

percent faster than traditional gravity dams.

The design philosophy of medium/ high paste RCC dams is that the concrete should

be watertight. Thus the RCC has to be designed to bond layer to layer to have an in-situ permeability equivalent to that of traditional concrete dam. In the same way as in

RCD dam, contraction joints are formed through the dam but these are at large

spacing. After observing the performance of RCC dams all over the world, the

present trend is to construct medium/high paste RCC dams for medium/large heights,

REALISING THE FACT THAT DURABILITY IS IMPORTANT IN ACHIEVING LONG TERM

ECONOMY TO OWNER .


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Another category termed as “hard-fill” dam is being advocated where high seismic

loading and relatively weak foundation are involved. This type of dam can be

described as cement stabilized rock-fill dam with flatter upstream slope (same as

downstream slope) than that of traditional gravity dam.

DESIGN CONSIDERATIONS

Gravity Dams: The design criteria/ parameters for RCC dams, though similar to that

of traditional concrete dams, do have their own characteristics that must be taken into

account in the design process. Material properties such as elastic modulus, Poisson’s

ratio, Co-efficient of thermal expansion and unit weight etc. are similar to traditional

concrete dam as these depend mainly on the aggregates used. The use of vibratory

rollers for compaction instead of immersion type vibrators does not change the basic

design concepts for dams. However, it affects construction procedures.

The important design considerations in RCC dams are:

• Shear Strength at lift surfaces

• Temperature studies for RCC

• Seepage control

• Bonding between successive RCC lifts

Generally, shear strength along the horizontal joints between the layers is critical

because of the "layered" method that is used in the construction of RCC dams. The

shear strength of RCC is dependent upon its tensile bond properties (cohesion) and

angle of internal friction. Minimum shear strength occurs at the construction joints

and along the inter-face between two successive lifts of RCC.

With the high cementitious content RCC, good cohesion is achievable but low

cementitious RCC can have low cohesion and may lead to higher permeability. The

design values should be chosen based on thorough testing of material or careful

extrapolation from other projects with similar materials. Some of the lean RCC dams

have also-been designed using a value of zero cohesion at lift joints i.e. in Copperfield& Craigbourne dams. However, in such a design a lower factor of safety can be

adopted which is the normal factor of safety multiplied by the ratio of residual

strength to peak strength. Table 2 indicates engineering properties like compressive

strength, shear strength etc. as obtained in some of the select RCC dams.

Table 2 – Engineering properties of select RCC dams

Dam Age

in

days

Comp.

Strength

(MPa)

Shear strength

(MPa)

Other criteria

Shimajigawa 90 19.6 C = 0.77

Willow Creek interior 90 7.6 Φ = 630

Middle Fork 90 13.4 C = 0.69, Φ= 450 Copperfield 90 15.0 C = 0, Φ= 45

0 FS (shear) = 2.0 min.

Craigbourne 90 10.0 C = 0, Φ= 450 FS (shear) = 2.0 min.

Upper Stillwater 365 20.7 C = 2.07 Static Tension = 1.24 MPa

Elk Creek 365 13.8 C = 0.35

Pamo 365 20.7Dynamic tension = 2.41

MPa


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For preliminary designs which require cohesion between lift joints, typically upto 1.5

MPa, particular attention will be required for the RCC mix selection and lift

treatment. For a traditional gravity dam, the dam-foundation interface is usually the

most critical section for stability evaluation. However because for potentially weaker

horizontal joints between the layers, it is also necessary to check stability for other

critical sections.

For final design, values of tensile and shear strength parameters at lift joints shall be

determined by conducting full scale in–situ direct shear test for various confining

pressures or on drilled cores taken from RCC full scale trials and tested in shear and

direct tension etc.

For high and medium height RCC dams, full scale trials are strongly recommended.

These trials must be designed specifically for a particular project.

Important considerations that must be addressed before proceeding with the design

works include the basic purpose of the dam and the requirements in respect of cost,

economy, water-tightness, operation and maintenance etc.

Arch dams:

The potentially weaker horizontal joints between the layers of RCC dams are not as

critical as the gravity dams because of the different mode of load transfer. The

temperature stress caused due to difference in ambient temperature and stabilization

temperature is more complicated in RCC dams and need to be evaluated in details

using FE analysis. The arch gravity dams have a thicker section and are therefore

more prone to trap heat due to heat of hydration of the cementitous material inside the

body. One of the approach has been to provide radially oriented transverse joints at

suitable interval and grouting after allowing the dam to cool down to its final

operating temperature.

Because stress levels in arch dams are normally higher than in gravity dams, it is

usually necessary to design such dams with an RCC having greater strength.

Consequently higher cementitious contents are required which may increase heat ofhydration. The selection of mixture proportion of such an RCC needs careful

consideration and may need additives to keep the temperature to acceptable levels.

Seismic Aspects:

The analysis of RCC dams for seismic loading conditions is identical to that for

traditional concrete dams. In seismic design of concrete dams there are certain good

practices such as eliminating or minimizing geometrical discontinuities in the dams

and reducing dead load at the top of the dam. These practices are equally applicable to

RCC dams. The tensile and shear strength requirements at the horizontal lift joints for

seismic loading can be important in seismic prone areas and proper measures have to

be taken during construction to accommodate these requirements. In such case, high

paste RCC may be desirable.

Thermal Considerations:

Cracks tend to develop in large unreinforced concrete structures if the structure is not

properly designed for temperature and crack control. The principal factors affecting

uncontrolled cracking are the peak internal temperature reached soon after placement,

the average annual ambient temperature to which the mass will eventually cool, creep,

the modulus of elasticity, and the degree of restraint acting at the crack location.


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These cracks usually appear during the first or second winter season and generally

initiate at exposed surfaces adjacent to the foundation (where the restraint is the

greatest). From there, they propagate inwards and upwards with continuing cooling of

the mass. If the change in volume is sufficiently large, the cracking can penetrate the

full thickness of the dam and become a source of leakage.

The most effective method to prevent massive concrete from cracking, apart from

reducing the heat generation within the body of the dam, is to reduce the difference in

temperature between the peak temperature reached after concrete placement, and the

final stabilised temperature, thus limiting the temperature drop of the structure. The

allowable temperature drop is a function of the block size and geometry, relative

location with respect to the foundation, relative stiffness of the concrete and the

foundation rock, tensile strength and creep behaviour of the concrete, rate of

temperature drop, etc. Field studies have indicated that block size plays a major role

in the formation of thermal cracks in mass concrete.

Because of the different construction technique, the temperature distribution and

corresponding thermal stresses in RCC dams are different from those of a traditional

concrete dam and hence these are one of the major design considerations. Studies of

the heat generation and temperature rise of massive RCC placements indicate thatrapid placement of layers can have a beneficial effect on crack reduction due to the

more consistent temperature distribution throughout the mass when compared to more

traditional ways of placing large volumes of concrete.

For the final design of large and medium -sized RCC dams, it is a practice to carry out

finite-element analysis to evaluate the thermal stress and crack potential. The physical

model should give a good representation of the dam body with its foundation,-

including galleries and other internal openings.

Factors, that are recommended by various experts to be modelled and that may have a

significant effect on temperature developments are:-

• Placing temperature of the RCC

• Adiabatic temperature rise and heat of hydration

• The construction programme

• Environmental heat losses & gains including heat gain by solar radiation

• Heat loss by radiation and convection (including wind effects), evaporation of

curing water and conduction to the foundation.

• Heat losses to the reservoir by conduction and convection Heat loss through

the galleries

Temperature Control

Peak temperatures in the RCC dams can be controlled by a combination of the

following measures:

• Optimization of the proportions of cement and mineral admixture to reduce

the heat of hydration to tolerable limits.

• Reducing the peak temperature by lowering the initial placing temperature of

the concrete mixture through cooling the coarse aggregate by chilled water, air

or ice.


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• Scheduling the construction of the thermally critical part of the structure

during winter time or at night to minimize temperature rise due to heat

adsorption.

• Evaporative cooling through curing water.

• Post cooling to accelerate cooling process. Post cooling is often not required in

gravity dams.

Contraction Joints:

The principal function of vertical contraction joints is to control cracking due to

volume change, foundation restrain and foundation irregularities. Majority of the early

dams did not contain the contraction joints but gradually there has been a swing

towards RCC dams in which contraction joints are formed from the upstream to the

downstream face. All RCD dams have joints at 15-m centres but the spacing of joints

if provided in RCC dams has ranged from 20 to 75 m. There are three main methods

by which contraction joints are formed in RCC dams:

i) Post-forming the contraction joints by vibrating steel or plastic crack intruders

into RCC after spreading RCC (in RCD dams & in some RCC dams) or after

compaction (most RCC dams). This method has been adopted in 70% of theRCC dams.

ii) Formed contraction joints against form work in a similar fashion to traditional

concrete dams. This has been used in 15% of RCC dams.

iii) Using various methods of incorporating a plastic sheet in RCC during spreading

occasionally by placing sheet over the steel frame. This has been used in 10% of

the RCC dams.

Galleries and Drainage:

The inclusion of galleries in RCC dams interfere with efficient placement and

compaction of RCC. However, since they provide the only immediate interior access,

release the uplift pressures and the resulting economy in the section, may be inincorporated when justifiable and preferably eliminated in low height dams (upto

30m) which can be economically designed to withstand full uplift pressures.

Winchester Dam is a good example of an RCC dam with no gallery.

In higher dams it is unavoidable, primarily because internal vertical porous drains in

the body of the dam and foundation drainage yield benefits in respect of both

economy and stability. In such case its location should be well conceived and

coordinated with the practical aspects, of construction. As far as possible, it should be

located at a single level, preferably by ditching in foundation. Multiple galleries

should be avoided wherever feasible.

Spillways and Outlets:

The layout of appurtenant structures like spillway, outlet works etc and the methods

that are to be used for the treatment of joints between the layers need to be thoroughly

planned so that the advantages of the rapid method of construction by roller

compacted methodology are not lost. Normally the outlets could be located in

trenches and the intake on the u/s so that the construction of the RCC dam can go on

independently and without any obstruction.


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With ever-increasing hydraulic requirements, the cost of spillways is a major

economic factor in dam design and construction. Spillways must be designed to pass

the design flood and all lesser-capacity flows safely and economically. Indian Code

on Guidelines for fixing Spillway Capacity (BIS No. 11223 - 1985) in general,

recommends an inflow design flood for the safety of the dam based on gross storage

and hydraulic head. Factors like the type of dam are not discussed in the above BIS

code. The layout of spillway would depend upon topography, hydrology, economicsand other such factors.

Three types of downstream spillway surfaces have been used for RCC dams. They

are:

• The traditional smooth conventional surface, e.g. Copperfield dam.

• Stepped spillway of conventional concrete, e.g. Upper Stillwater dam.

• An unformed exposed RCC surface e.g. Galesville dam.

With the traditional concrete spillway, the objective is to provide a smooth flow

surface for prevention or minimization of cavitation damage. The stepped spillway

design is more widely used in RCC dams. The rough stepped surface produces a

highly turbulent, well-aerated boundary layer that eliminates negative pressures and prevents cavitation damages.

With the advent of the RCC construction method and the relatively easy incorporation

of conventional concrete steps concurrent with horizontal RCC placement, a renewed

interest in stepped spillways has developed. The steps improve hydraulic behaviour of

the flow and reduce the velocity of the water, leading to less potential for cavitation

and less-expensive stilling basins when compared to smooth spillway chutes.

The steps act as roughness elements to minimize flow acceleration and terminal

velocity. Turbulence induced by the steps helps speed the development of a boundary

layer and induces entrained air to bulk the flow. Cavitation potential is thus, reduced

by both the reduced velocity and the cushioning effect of the entrained air.

It has been seen that the height of spill over stepped spillways is normally restricted toa few meters only (Max 3 m.) and hence this may warrant an excessive length on

ungated spillway where resorted to. Individual cases will determine the best option,

given the topographic and other constraints besides the inflow design flood that has to

be catered for.

Lift Thickness:

The design lift thickness depends primarily on the construction equipment available

and the consistency of RCC mixture. It is defined as the thickness of the RCC that is

compacted at one time. In determining a lift thickness, the purpose is to provide a

thickness that can be compacted to the required density uniformly throughout the lift

with readily available equipment considering the consistency of the RCC mixture.

The most typical RCC lift thickness to date has been 300 mm. This includes nearly all

completed lean RCC dams as well as high paste RCC dams. The horizontal lifts are

generally sloped slightly upstream to allow for drainage.

Seepage Control and Upstream Facing:


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There can be large variations in the co-efficient of permeability of RCC dams

depending upon the method of construction. This co-efficient determines the seepage

through the dam. Large amounts of seepage may be acceptable for flood control dams

as long as the stability is not impaired; but this however may be the cause for serious

concern in a storage dam. Therefore, seepage control is an important consideration in

the design of RCC dams.

The various methods chosen for reducing or controlling seepage have produced a

great variation in the designs of RCC dams. The basic form of seepage reduction can

be divided into two categories:

(1) Those solutions that rely upon the entire interior RCC mass for the dam's

impermeability

(2) Those that rely on an impermeable or relatively impermeable upstream face

or membrane as the primary water barrier.

For secondary seepage control the upstream facing designs may also include partial or

full bedding mixes between lifts and some form of drainage collection system

downstream from the face. Lean RCC dams generally require bedding mixes on lift joints for seepage control. On the other hand, high paste RCC dams do not require any

such treatments.

Various methods used for forming the faces of RCC dams are:

a) Facing concrete against formwork:

It is the most popular method of forming the face of RCC dams. The sequence of

placement recommended is as under:

i) First place facing concrete

ii) Then place RCC

iii) Vibrate the facing concrete

iv)

Then roller compact the RCC including the interface with facingconcrete.

b) RCC against formwork :

This is particularly popular in Spain in which high paste RCC is used. Excellent

finish is obtained provided the RCC has sufficient paste and is sufficiently

workable. Grout - enriched vibratable RCC (GEVR) is a recent development in

this direction. It was primarily developed at the 128 m - high Jiangya dam in

China.

c) Slip forming of facing elements:

This method eliminates the need of formwork and separates the forming of the

face from the placement of RCC. The RCC can usually be compacted against thefacing elements within 4 to 8 hours (depending upon site conditions). It is more

applicable to wide valleys and was used for Upper Stillwater dam.

d) External membrane:

In order to provide an impermeable barrier, an external membrane has been fixed

on the upstream face of some lean RCC dams. The membrane completely covers

the u/s face and it is fixed separately after completion of the dam.


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e) Pre-cast concrete blocks:

Pre-cast blocks have been used for the d/s face and in a few cases for the spillway

of RCC dams. This is equivalent to the use of pre-cast concrete panels on the u/s

face. Usually, the concrete blocks are interlocking so that the support for the new

block is obtained from the previously placed blocks. This method of forming theface is becoming popular in China.

f) Unformed downstream face: A number of RCC dams have unformed

downstream faces. The RCC is allowed to form its natural angle of repose which

is between 0.80: 1 and 1.00: 1. However the last RCC dam to have unformed

downstream face was Zintel Canyon (USA) in 1992. The method is presently not

preferred.

Bonding Successive Lifts: RCC to RCC Bonding:

Because RCC dams are constructed in a series of compacted lifts, bonding of the

successive lifts is important both from the stability and performance standpoint.

Poorly bonded lifts have lower shear resistance due to low or no cohesion at theinterface, have less tensile resistance for seismic loading and offer a path for

horizontal seepage.

The principal factors that affect bonding are:

i) Condition of the lower RCC lift surface

ii) Time delay between placement of RCC lifts

iii) Consistency of the covering RCC

iv) Compaction or consolidation of the covering RCC.

The lower RCC surface must be kept continuously moist but without ponding water to

ensure bond. Excessive surface moisture is detrimental to bond development but

drying of the surface may lead to no bond.

In certain design practices, one specifies joint treatment and use of bedding mixes on

the basis of a maturity factor. In USA this is in degree-Fahrenheit-hour. In the rest of

the world degree-Centigrade-hour is commonly used. There is no consensus of

opinion regarding the limits of the maturity factor. This may be because the

conditions are so specific that each dam has to be considered as unique. The maturity

factor would depend upon many factors:

(i) The mixture (water content, quantity of paste, type of cementitious

material, retarders etc.

(ii) Workability and potential for segregation

(iii) Compaction methods and equipment

(iv) Ability to get back to the same location for placement of the successive lift

(v) Effectiveness of curing etc

Three classes of joint treatment have been designed as follows:

i) A fresh (or hot) joint - This is a joint that occurs when the RCC layers are

being placed in rapid succession and the RCC is still workable when the

next layer is placed.


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ii) An intermediate (or warm or prepared) joint - This is the condition that

occurs between a fresh joint an a true "cold" joint

iii) A cold joint

A general summary of the joints in RCC dams along with treatment etc. in terms

of maturity factor is given in Table -3.

TABLE 3 JOINT TREATMENTS FOR VARIOUS CATEGORIES OF

RCC.

Type of RCC Fresh joint Intermediate joint Cold joint

Lean RCC

Maturity Factor

Treatment

Bedding Mix

< 100oC-hr

Clean with vacuum

truck

None

100-250 o

C -hr.

clean with vacuum

truck

Partial for upstream

section.

250oC-hr

Water clean surface

Full mix over

whole surface.

RCD

Maturity Factor Not used Not used

All joints treated as

cold joints ‘Greencut’ of whole

surface

Full mortar over

whole surface

Medium paste RCC

Maturity Factor

Treatment

Bedding mix

< 200 oC-hr.

Clean with vacuum

truck

None

200-500 oC-hr

Low pressure water

clean

Partial for u/s section.

High paste RCC

Maturity FactorTreatment

Bedding Mix

< 300 o

C-hrClean with vacuum

truck

None

300-800o

C-hrLow pressure water

clean

None

>800o

C-hr ‘Greencut’ of whole

surface

None or full

bedding mix.

INSTRUMENTATION

Instrumentation data is an essential part of safety monitoring and evaluation of the

project and is useful for monitoring the behaviour of the dam during the construction

and operation. Instrumentation needs to be carefully planned so as not to interfere

with RCC construction. Ideally installation should be planned to coincide with the

planned construction breaks e.g. for maintenance etc or should be designed so that

they can be installed as a separate activity to the main construction.

The instrumentation in RCC dams is similar to that in traditional concrete dams.

However more emphasis is usually placed on thermal conditions because of more

rapid method of construction. Thermocouples are preferred for temperature

measurements and long-base strain gauges (at least 1m long) for crack width

measurement. In order to determine a representative profile of these parameters in the

RCC these should not be used sparingly.


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For measurement of deformation of dam, telltale signs can be fixed on the dam faces

soon after compaction of layers of RCC dam is finished. Regular observation shall be

taken by Theodolite/total station instruments and then analyzed.

Installation of extensometers and inverted plumb lines from the gallery also do not

interfere with the RCC placement. This may also be true for the direct plumb-lines

providing the plumb-line well is not formed during the construction but drilled after

construction. In addition 2 or 3 dimensional joint meters can be installed in the

galleries on as many joints as is considered appropriate.

CONCLUSIONS

RCC dams by now have emerged as a viable alternative to concrete gravity dams.

Though the design of a dam using RCC is fundamentally no different from the design

of traditional gravity dams, there are certain aspects of design which are peculiar to

RCC dams and need careful consideration so as to prevent uncontrolled cracking. The

present trend is to construct medium/ high paste RCC dams from the consideration

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