04. 20210706 Fecon - Thermal Control Plan For Wind Turbine Foundation.pdf

“THERMAL CONTROL PLAN FOR WIND TURBINE FOUNDATIONS” Mr Quoc Tuan TRINH Deputy Manager, Technical Dept FECON  (+84) 904 487 486  tuantq1@fecon com vn Hanoi, 31st July 2021 VIETNAM CONCRETE ASSOCIATIO[.]

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“THERMAL CONTROL PLAN FOR WIND

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1 Introduction

2 Main concerns of Mass Concrete

3 Thermal Control Plan

4 Application to Wind Turbine Foundations

5 Conclusions

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HCM cityMyanmar

YANGOON, MYANMAR

• FECON Rainbow Co.,

• FECON Trung Chinh JSC

Founded in 2004, FECON has become one of the most

prestigious contractor in Foundation and Underground.

FROM THE START POINT

+800 COMPLETED PROJECTS

FECON is striving to become a leading EPC

in Infrastructure and Industrial ConstructionTOWARD THE VISION 2025

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Worker

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RENEWABLE ENERGY INFRASTRUCTURE

• CONSTRUCTION

• INVESTMENT

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Onshore Wind Power Plant Near-shore Wind Power Plant

Offshore Wind Power Plant (in development)

FECON - B.O.P CONTRACTOR (ENGINEERING AND CONSTRUCTION)

1 ONSHORE WF THAI HOA – BINH THUAN –90 MW

2 ONSHORE WF BT QUANG BINH –250 MW

3 ONSHORE WF LAC HOA & HOA DONG – SOC TRANG –60 MW

4 ONSHORE WF QUOC VINH – SOC TRANG –30 MW

5 NEARSHORE V1-3 – TRA VINH –50 MW

 TOTAL OF 112 WIND TURBINE FOUNDATIONS - 480 MW

FECON’S EXPERIENCES IN WIND ENERGY (period 2020-2021)

8

Note: BOP = Balance of Plant

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• Vietnam: least dimension > 2m

• Japan / Korea: least dimension > 0.8-1.0 m

• ACI: any concrete volume with dimensions large enough to require that measures to be taken …

 WTG Foundations must all be treated as mass concrete!

9

WIND TURBINE FOUNDATIONS – MASS CONCRETE STRUCTURE ?

• Bigger and bigger wind turbine

generators (WTG) are being used

• Huge overturning moment is applied

to the Foundation

 Foundations are made bigger, heavier

to withstand the increasing loads

A typical shallow WTG Foundation

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1 Introduction

5 Conclusions

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 Temperature Difference

(can result in thermal cracking)

 Maximum Temperature

(can reduce strength & durability)

ACI 207.1R states that the only characteristic that distinguishes mass

concrete from other concrete work is thermal behavior that may

cause a loss of structural integrity and monolithic action.

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 Temperature Difference

• Hydration process leads to the temperature rise in

mass concrete

• Low ambient temperature induces temperature

gradient between the exterior concrete & interior concrete

• The interior concrete tends to expand

• The exterior concrete tends to shrink and resist

interior concrete to expand, causing thermal stress

 If thermal Stress > Tensile Strength

→ Thermal Cracking occurs

 Free surfaces need to be insulated!

Selecting correct Insulation & Choosing correct

removal time is crucial for Mass Concreting

Temperature difference → Strain

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 Temperature Difference (Cont.)

• Not enough Insulation → Big ΔT → Thermal

Cracking

• Sufficient insulation but Early Removal can

cause Thermal shock → Thermal Cracking

Insufficient insulation

Early formwork removal

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 Temperature Difference (Cont.)

 Required Temperature Difference

• TCVN:ΔT ≤ 20⁰C, gradient T ≤ 50⁰C /m

• ACI:ΔT ≤ 20⁰C (35 ⁰ F)

 FECON’s practices for Insulation

• 5 (cm) of Styrofoam is generally sufficient

• Styrofoam inside the Formwork to enable early formwork removal

• Insulation removal time:

+ 07 days if cooling system is used + 21 days if no cooling system is used

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 Maximum Temperature

DELAYED ETTRINGITE FORMATION (DEF)

 Ettringite is one the the first new crystal that forms instantly

when water is added to Porland cement Ettringite formed at early

ages is often refered to as ‘Primary Ettringite’ It is a necessary and

beneficial component:

C3A + CSH2 + H2O → Ettringite (C6AS3H32)

C3S + H2O → C3S2H3 (glue) + CH

C2S + H2O → C3S2H3 (glue) + CH

Ettringite + C3A + H2O → Monosulfates (3C4ASH18)

C4AF + H2O → Hydrogarnets

However,

 Concrete cured at excessively high temperature, i.e > 70 ⁰C,

may develop (DEF) because ettringite decomposes – or does not

form at high temperature

 Later it forms / reforms after the concrete has hardened and

may cause expansion & micro-cracking

Mechanism of micro-cracking in the paste and aggregate interface due to DEF

DEF leads to a decrease of mechanical performance and durability of the structure !

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 Maximum Temperature (Cont.)

 Required T max for Wind Farm

• Tmax ≤ 70 ⁰C (SGRE, VESTAS, GE …)

 FECON’s practices for Thermal Control

• Many factors to be considered

• Many measures that range from simple to complex

• Depending on actual site conditions, one or

multiple measures can be applied

 Proposed T max for Wind Farm

• Tmax ≤ 80 ⁰C

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1 Introduction

5 Conclusions

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To reduce thermal stresses and control cracking, the general measures should be:

Material Selection: cementitious material content control

Pre-cooling and / or Post-cooling of concrete

Construction Management: concrete handling, construction

scheduling and construction procedure

→ Depending on the actual site conditions, one or multiple solutions shall be applied!

References:

• ACI 301-20 “Specifications for Concrete Construction”

• ACI 207.1R-05 “Guide to Mass Concrete”, 207.2R-07 “Report on Thermal and Volume Change Effects on Cracking of Mass Concrete”

• ACI 224R-01 “Control of Cracking of Concrete Structures”

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Material Selection: cementitious material content control

Mix design with lower heat hydration:

• GGBF

• Fly Ash

• Low-Heat Hydration Cement

Lower peak temperature when pozzolans are introduced in the mix design

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Pre-cooling and / or Post-cooling of concrete

• Shelters

• Spray coarse aggregates

• Chiller / Ice for mix water

• Liquid Nitrogen (not feasible)

 Each 6 ⁰C lowering of the placing temperature will result in a lowering by about 3 ⁰C of the peak temperature (ACI)

 Above pre-cooling measures can reduce the placing temperature by 5-10 ⁰C

 Applied in most of Fecon’s Wind Projects

as they are relatively simple & not costly

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Pre-cooling and / or Post-cooling of concrete

• Remove internal heat after concrete has been placed

• Reduce maximum temperature

• Reduce cooling time

• Specified peak temperature is 70 ⁰C

• Demand of quick construction of hardstand

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Construction Management: concrete handling, construction

scheduling and construction procedure

Lift 1 Lift 2

• Cast during night time

(one of the simplest measure)

• Coordination of construction schedules with seasonal changes

(try to avoid summer time or hot weathers)

• Cast the structure in multiple lifts

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1 Introduction

5 Conclusions

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Assessment of Inputs

Thermal Control Plan

Trial & Error

Full-scale Mockup

Implementation

Repeat if NOT OK

• What is the mix design ?

• Cast in one time or multiple times ?

• Using pre-cooling or not ?

• Using cooling pipe or not ?

• What is the curing method ?

• Method Statement, Working Drawings, ITP … for Mass Concrete, where Tmax and ΔT are predicted

Foundation dimensions

Weather

Onshore or Offshore

Concrete provider Project

Specifications Project

Schedule

Output

Water / Ice availability

If OK

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Trial & Error

Full-scale Mockup

Implementation

Repeat if NOT OK

Weather

Schedule

Output

If OK

Hot

No water

Onshore D=26m, T = 3.6m

T max < 80 ⁰C

Not tight

Mix design not optimized

PROJECT A

Example 1

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Trial & Error

Full-scale Mockup

Implementation

Repeat if NOT OK

Weather

Schedule

Try #1

Output

If OK

Hot

No water

T max < 80 ⁰C

Not tight

• Mix design: OPC

• Cast: one time

• Pre-cooling: placing temp ≤ 30 ⁰C

• Cooling pipe: No

• Curing compound: Antisol type E

PROJECT A

Example 1

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Trial & Error

Full-scale Mockup

Implementation

Weather

Schedule

Try #1

If OK

Hot

No water

T max < 80 ⁰C

Not tight

• Mix design: OPC

• Cast: one time

• Pre-cooling: placing temp ≤ 30 ⁰C

Repeat as NOT OK

PROJECT A

Example 1

T max > 80 ⁰C

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Trial & Error

Full-scale Mockup

Implementation

Repeat if NOT OK

Weather

Schedule

Try #2

Output

If OK

Hot

No water

T max < 80 ⁰C

Not tight

• Mix: using Fly-ash or GGBF S95

• Cast: one time

• Pre-cooling: placing temp ≤ 30 ⁰ C

PROJECT A

Example 1

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Trial & Error

Full-scale Mockup

Implementation

Weather

Schedule

Try #2

If OK

Hot

No water

T max < 80 ⁰C

Not tight

• Mix: using Fly-ash or GGBF S95

• Cast: one time

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Trial & Error

Full-scale Mockup

Implementation

Weather

Schedule

Output

If OK

• Mix: using Fly-ash

• Cast: one time

PROJECT A

Example 1

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Tmax = 78-79 ⁰C

Flyash 30% replacement – Evolution of Core Temperature

Full scale Mockup 3.6x3.6x3.6 (m)

 Good agreement with prediction!

 T max < 80 ⁰C → pass!

 Little contingency (peak temp so close to T max )

 Recommendation from OE: cast the pedestal later!

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Trial & Error

Full-scale Mockup

Implementation

Weather

Schedule

Output

• Mix: using Fly-ash

• Cast: Slab first, then Pedestal

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Construction of the 1 st WTG Foundation:

+ Max lift height: 2.95 (m) (instead of 3.6 m)

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PROJECT B

 Effectiveness of Cooling Pipes:

w/o cooling pipe

with cooling pipe

 Tougher input conditions:

+ Very tight schedule!

+ Max lift height: 3.4 m (pedestal included)

+ Concrete C35/45 MS (cement ~ 400 kg/m 3 )

+ Allowable Tmax = 70 ⁰C

+ Ambient temperature: ~ 33 ⁰C

 Thermal Control Plan must combine all available pre-cooling

& post-cooling measures:

+ Pre-cooled concrete

+ 4 layers of cooling pipes, D27 @700

+ Icy circulating water, 17 litters/min

 Max temp < 65 ⁰C, foundations can be backfilled after 7 days

Example 2

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1 Introduction

5 Conclusions

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5 Conclusions

 Method of controlling mass concrete

temperature range from relatively simple to

complex, and from inexpensive to costly:

 To reduce ∆T:

 Surface Insulation

 To reduce Tmax:

 Pre-Cooling of Concrete (spray

aggregates, icy water, shelter etc )

 Use lower cement content (mix with

GGBF / Fly-ash) or use Low Generation Cement

Heat- Placing concrete in lifts

 Post-Cooling of Concrete (cooling

pipes)

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 Without proper preparations and correct measures, strength &

durability of the massive concrete structure shall be compromised!

 No unique solution for every mass-concrete project

 Contractors can use one or multiple measures to optimize the cost

5 Conclusions

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Mr Quoc-Tuan TRINH

Deputy Manager, Technical Dept FECON

 (+84) 904.487.486

 tuantq1@fecon.com.vn

Tiêu đề	Thermal Control Plan For Wind Turbine Foundation
Người hướng dẫn	P. Nguyễn Văn A, Instructor
Trường học	Vietnam Concrete Association
Chuyên ngành	Infrastructure and Industrial Construction
Thể loại	Workshop Presentation
Năm xuất bản	2021
Thành phố	Hanoi

Định dạng
Số trang	38
Dung lượng	5,02 MB