Global Manager, Dams & Hydropower - ESI- .Mark Cordell Global Manager, Dams & Hydropower High quality

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  • Mark Cordell

    Global Manager, Dams & Hydropower

    High quality consulting and development solutions

    worldwide

  • Major Dams ≥60m Under Construction in 2009

    Source: 2009 World Atlas & Industry Guide

  • Major Dams ≥60m Under Construction in 2009 - Worldwide- Africa

    Source: 2009 World Atlas & Industry Guide

  • RCC Mix Design An Introduction and Case Study

    • Introduction • RCC and Dam Construction Today • RCC Mix Constituents • RCC Design Philosophies • Options Using Various ‘Quality’ Aggregates

    ­ A Case Study

  • RCC Mix Constituents

    Roller Compacted Concrete – RCC – is a Concrete

    • Dry enough to support vibratory

    roller

    • Wet enough to permit adequate

    distribution of

    paste

  • RCC Design Philosophies

    “High Paste”

    • High cementitious content (typ. 180­240kg/m3) • Relatively large quantities of Pozzolan as

    substitute for natural fines

    • Workable material • Low permeability • “Premium” concrete

  • RCC Design Philosophies

    “Low Paste”

    • Low cementitious content (typ. 70­90kg/m3) • Relies on continuous dense grading envelope to

    fine fraction for its density

    • Lower workability • Higher permeability • Need for Upstream Membrane?

  • Location • Dak Nong

    Province, Vietnam

    Services • Technical Appraisal • RCC Mix Lab Tests/Trial Embankment • Construction Assistance

    Main Features • 108m RCC dam • 180MW Power house • 607GWh/annum

    Dong Nai 3 Hydroelectric Project, Vietnam

    DONG NAI 3 HEP

  • Project Status

    • Feasibility Studies completed in March 2000 • Design further developed by Power Engineering

    Consulting Company No.2 (PECC2) with

    assistance from an International Consultant Firm

    • SMEC engaged to undertake Independent Technical Appraisal of Dong Nai 3 and Dong Nai

    4 RCC Dam Designs in January 2006

    • SMEC’s appointment in accordance with GoV policy for technical oversight on large RCC Dams

  • Project Status

    Following the Independent Technical Appraisal,

    SMEC were engaged to:

    •Supervise the RCC Trial Mix Programme, including the Trial Embankment

    •Supervise the establishment of the Aggregate Quarry

    •Provide ongoing Construction Assistance for Dong Nai 3 and Dong Nai 4 RCC Dams

  • Principal Objectives of Technical Appraisal

    • Review the proposed design concept of the RCC dams

    • Review the proposed RCC dam construction methodology

    • Assess geological conditions of the dam sites and proposed quarries

    • Inspect and comment on concrete laboratory and hydraulic modelling facilities used for design

    development of the Projects

  • Original Design Concept for RCC Dam

    • RCC mix design based on high cementitious content 170kg/m³

    (60kg/m³ cement; 110kg/m³ pozzolan)

    • Metasediment aggregate source • Central Vietnam commercial pozzolan source

    ­ relatively high transportation cost

  • Locally Available Aggregate Options - Metasediment Aggregate Source

  • Locally Available Aggregate Options - Basalt Aggregate Source

  • Characteristics of Basalt Quarry - Solid Basalt

  • Characteristics of Basalt Quarry - Vesicular Basalt

  • Characteristics of Basalt Quarry - Dirt Seams

  • Thermal Expansion and Thermal Stress

    • Critical property of concrete for dams • If stiffness (Modulus of Elasticity) and creep

    similar, thermal stress and related potential for

    cracking essentially proportional to coefficient of

    thermal expansion

    • This property of RCC dependent of aggregate properties

  • Thermal Expansion and Thermal Stress

    At Dong Nai 3:

    • Metasediment 10.7 x 10­6/°C • Basalt 4.6 x 10­6/°C The Basalt aggregate offered much more

    favourable thermal properties – low thermal

    stresses

  • Unit Weight, Density and Air Voids

    • Initial concern with vesicular nature was effect the basalt aggregate would have on RCC density

    • When crushed to less than 13mm, specific gravity of the two aggregates essentially same

    (≈2.72)

    • Coarser aggregates had a lower specific gravity for 25­50mm particles (2.64 vs 2.76)

  • Unit Weight, Density and Air Voids

    • However, the coarse aggregates only represented 20% of total aggregate – impact on

    the overall density not significant

    • The vesicular basalt exhibited greater absorption, but the mix proportions were based

    on saturated aggregates, so essentially no effect

  • Gradation

    • Initial gradation of aggregates adjusted to be consistent with efficient RCC mixes (greater

    strength per kg of cementitious material)

    • Better mixability • Less segregation for mixes of same cementitious

    content

    • Less void space in compacted aggregates • Less need for cement and pozzolan to fill void

    space

    0

    1 0

    2 0

    3 0

    4 0

    5 0

    6 0

    7 0

    8 0

    9 0

    1 0 0

    0 .0 1 0 .1 0 1 .0 0 1 0 .0 0 1 0 0 .0 0

    S ize (m m )

    % P

    as si

    ng

    In it ia l M e ts S a nd s ton e La b M ix G r ad a t io n

    S M E C M ix e d B as a lt La b M ix G r ad a tio n

    S M E C B as a lt A t In ita l La b M ix G r ad a tio n

  • Comprehensive Mix Design Studies

    • Many mixes assessed ­ varying cement and pozzolan contents, including mixes with no

    pozzolan

    • Control mixes – ‘initial’ gradation • Most mixes used improved gradation • Base mixes used ‘mixed basalt’ – 70% solid

    basalt; 25% vesicular basalt; 5% dirty material

    • 100% crushed vesicular basalt mix made for comparison

  • Compressive Strength Development [MPa]

    0

    5

    10

    15

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    1 10 100 1000

    C o

    m p

    re s

    s iv

    e S

    tr e

    n g

    th (M

    P a

    )

    Age (Days)

    170-65-4.2 (7) 1x (SMEC Gradation - Metasediment) VB1=11 Sec 170-65-4.2 (4) 1x (Initial Gradation-Metasediment) VB1= 23 Sec 170-65-4.2 (8) 1x (SMEC Mixed Basalt) VB1=15 Sec

    Cementitious Content (kg/m3)-% Pozzolan-% Moisture Content (% Fines) Admix Dose

    Accelerated Cure

    Accelerated Cure

  • Basalt vs Metasediment – No Pozzolan

    0

    5

    10

    15

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    25

    30

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    1 10 100 1000

    C o

    m p

    re s

    s iv

    e S

    tr e

    n g

    th (M

    P a

    )

    Age (Days)

    90-0-4.2 (8) 1x : VB1=15 Sec, Mixed Basalt

    90-0-4.2 (7) 1x : VB1=15 Sec, Metasediment

    Cementitious Content (kg/m3)-% Pozzolan-% Moisture Content (% Fines) Admix Dose

    SMEC Gradation

  • Effectiveness of Pozzolan vs Aggregate Fines

    0

    5

    10

    15

    20

    25

    30

    35

    40

    1 10 100 1000

    C o

    m p

    re ss

    iv e

    S tr

    en g

    th (M

    P a)

    Age (Days)

    60-0-4.2 (8) 1x : VB1=12 Sec

    120-0-4.2 (8) 1x : VB1=18 Sec

    120-50-4.2 (8) 1x : VB1=13 Sec

    170-65-4.2 (8) 1x: VB1=15 Sec

    Cementitious Content (kg/m3)-% Pozzolan-% Moisture Content (% Fines) Admix Dose

    60 kg Cement + 60 kg Cement

    60 kg Cement + 60 kg Pozz

    60 kg Cement + 00 kg Pozz

    60 kg Cement + 110 kg Pozz

    SMEC Mixed Basalt SIKA TM 25 Admix

    Accelerated Cure

  • Effect of Dirty Material on Strength

    0

    5

    10

    15

    20

    25

    30

    35

    40

    1 10 100 1000

    C o

    m p

    re ss

    iv e

    S tr

    en g

    th (M

    P a)

    Age (Days)

    90-0-4.2 (8) 1x : VB1=15 Sec, 5% Dirty Basalt 90-0-4.2 (8) 1x : VB1=15 Sec, No Dirty Basalt

    Cementitious Content (kg/m3)-% Pozzolan-% Moisture Content (% Fines) Admix Dose

  • RCC Trial Embankment

  • RCC Trial Embankment

  • Mix 110 + 60 (Basalt)

  • Mix 75 + 00 (Basalt) Mix 90 + 00 (Basalt)

  • Dong Nai 3 RCC Dam - Nearing Completion

  • Thank You

    Mark Cordell Global Manager, Dams & Hydropower mark.cordell@smec.com

    High quality consulting and development

    solutions worldwide www.smec.com

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