Cement & concrete solutions for underground structure

MOUSSA BAALBAKI

Head of Products & Solutions Portfolio

Siam City Cement (Lanka) Ltd

AGENDA

• Degradation mechanism

• Key durability indicators

Key challenges to cope with increasing society’s need for construction materials

• From prescriptive to performance based specification

Sustainable performing concrete

• What really matters to us

Durability of underground concrete

Conclusion

In theory – What really matters to usGlobal population growth over the last 2,000 years, with the doubling times marked

Source: Michael F. Ashby, Materials and the Environment

World population development [bn inhabitants]

In practice – What really matters to usWorld population grow & Ongoing trend towards urbanization, particularly in emerging countries

47% urban

60% urban

3.2 3.32.9

5.0

1970 2000 2030

36% urban

1.32.4

urbanrural

70% urban

2.8

6.4

2050

Both trends will significantly increase society’s need for construction materials

Source: United Nations, World Urbanization Prospects: The 2007 Revision (www.un.org)

Next to water concrete (~ 7 billion m3) is by far the most widely used material in the world (economic, availability, versatility, durability and adaptability)

Construction sector has an important ecological footprint…Unfortunately we use these natural resources at a rate that cannot be sustained indefinitely

Source: World Green Building Council, The ecological footprint

30 – 40% 40 – 50%17% 25% 33%

Wood harvest CO2 emissions Energy use Raw material use

Fresh water consumption

Important to highlight that Portland cement and concrete

• Use large volume of raw materials quarried from the earth

• Their production requires a large amount of energy

• And manufacture of OPC emits a large amount of CO2

The real matter – in practiceGlobal climate change from the so-called greenhouse gas emissions (mainly CO2, methane & nitrous oxide)

The real matter – in practiceSand has become a scarce resource with increasing public attention…

Therefore the construction sector must promote sustainable and performing solutions which:

• Emit less CO2 (Green House Gas)

• Offer extended service life of concrete structures with reduced maintenance cost

• Is economically viable

• Support the overall commitment to sustainable development

CO2 - emissions in clinker production (electricity neglected)

• Three main levers to reduce CO2

• Modern plants

• Reduction of clinker content

• Usage of alternative fuels

Blended cements for high sustainable performing concrete…emitting very low CO2 emission during production

Is ordinary portland cement (OPC) still needed in modern construction?Can we meet customer demands?

European domestic deliveries by cement type (2000 -2010) - Data : Cembureau

75% are blended cements

(CEM II / CEM III, CEM IV and CEM V)

25% is CEM I = OPC : mainly used for high end prefabricated reinforced elements (pre-stressed/post-tensioned and winter concreting (< 10°C)

What do all these strategic infrastructures have in common?

Confederation bridge

Canada - 1997

V. de Gama bridge

Portugal - 1998

Öresund tunnel

Sweden - 2000

Medway bridge

UK - 2001

Monaco floating dyke

France - 2002

Rion Antirion bridge

Greece - 2005

Millau bridge

France - 2004

100 – 120 years specified service life design

Performance based specifications including durability indicators

Designed with blended cements (Slag, FA, SF)

Today the tallest, deepest, heaviest structures and also the longest sea

infrastructures in the world are concrete structures produced with SPC

Burj Khalifa - + 800m Nord sea offshore platform-350 m / ~1 Mio t

Jiaozhou bay bridge - 40 km

AGENDA

• Degradation mechanism

• Key durability indicators

Key challenges to cope with increasing society’s need for construction materials

• From prescriptive to performance based specification

Sustainable performing concrete

• What really matters to us

Durability of underground concrete

Conclusion

• Today most concrete standards follow a prescriptive approach for durability, establishing minimum cement contents, maximum w/c ratios etc., leading to commoditization

• This prescriptive approach has shown to be insufficient to reach the durability performance goals

• There is a noticeable trend towards Performance Based Specifications (PBS), where a minimum performance has to be achieved, based on standard tests

• Some countries have already put in place performance tests and specifications for certain exposure classes

• Performance based specification of concrete are already an essential selection criterion in large construction projects

Concrete standards - Current situation

• The classical prescriptive approach specifies a durability Indicator based on w/c ratio that:

• is increasingly questionable (syndrome of concrete cube strength!)

• is very difficult to control in practice

• does not encourage innovation and is an obstacle for sustainable concrete mix designs

• does not guarantee durability, as reality has confirmed

• By checking the end product, a performance-oriented mindset is created in all players:

• contractors: deliver the end product to be tested

• producers: develop most efficient design, produce and deliver the concrete with the required performance

• raw material suppliers (cement, additions, admixtures): produce and deliver their products to achieve the target performance in concrete application

Pitfalls of Prescriptive Design

• Degradation mechanisms different between mechanical instability and chemical instability

• Application of concrete technology knowledge limited – it is more important what are the mix proportions than what are the obtained properties

• Most of the limiting values cannot be checked during construction

• Ensured service life of 50 years

Pitfalls of Prescriptive Design

Maslenica Bridge, 1997Gubasevo Bridge, 1990

Source: Bjegović, D.; Stipanović Oslaković, I.; Serdar, M. From Prescriptive Towards Performance-based

Durability Design of Concrete // Workshop - Cement and Concrete for Africa. Berlin : BAM Federal Institute

for Materials Research and Testing, 2011. 50-58

Mix design, type of materials

Cover depth

Construction procedures

(Eventual protective measures)

PRESCRIPTIVE DESIGN

STANDARD (e.g. EN 206-1)

IDENTIFY the exposure environment

CONSTRUCTION and QUALITY

CONTROL TESTS on moulded

specimens (cured under standard

conditions)

COMPLIANCE?

PREQUALIFICATION TEST

(usually base only on

compressive strength)

NO

YES

ACCEPTANCE

Repair and

maintenance

measures

(protection)

YES

NO

?

Mix design, type of materials

Cover depth

Construction procedures

PERFORMANCE BASED DESIGN

DETERIORATION MODE

(e.g. transport mechanism)

IDENTIFY the exposure

ENVIRONMENT

(quantify environmental load)

CONSTRUCTION

QUALITY CONTROL ON SITE

Moulded specimens + concrete

cover depth + In situ concrete

assessment

COMPLIANCE?

SLM check

PREQUALIFICATION

TEST

+

Determination of durability indicator

in lab test simulating

deterioration mode

NO

YES

ACCEPTANCEBirth Certifcate

PROTECTION

REPAIR &

MAINTENANCE

MEASURES

MONITORING

YES

NO

DURABILITY INDICATORS Testing methods (simulation of

environment and deterioration mode)

Service life model

Criteria for the evaluation

PR

ES

CR

IPT

IVE

SERVICE LIFE MODEL

(input parameters: environment,

durability indicators)

YES

NO

Service Life Prediction Models

FIB Model

Code

Duracrete

Life-365

Stadium

Duracon

Fédération internationale du béton

Jacques Marchand, SIMCO

AGENDA

• Degradation mechanism

• Key durability indicators

Key challenges to cope with increasing society’s need for construction materials

• From prescriptive to performance based specification

Sustainable performing concrete

• What really matters to us

Durability of underground concrete

Conclusion

Porosity and permeability – key drivers for concrete durability

Muller, A.C.A. et al., J . Phys. Chem. C 117 (1), 2013

• Permeability of concrete is paramount to assure water-tightness and durability of underground

structures

• Capillary pores start to be connected when w/c > 0.40

• When w/c > 0.65 most capillary pores are connected

1 mm

C-S-H

Why blended cements promote refinement of pore structure of matured concrete (chemical and microstructural effects)

+FA

+Ca(OH)2 or ` Portlandite

+OPC/silicates

Water

OPC

Hydration

reaction

C-S-H Slag

Pozzolanic

reaction

Blended Cement

Blended cements promote refinement of pore structure of matured concrete (chemical and microstructural effects)

C-S-H gel pores

Capillaries pores

Ca(OH)2

Deterioration processes that may affect the service life of concrete constructions

• Electrochemical (steel corrosion induced by CO2 or Cl-)

• Chemical attack (sulphate, acid, pure water, DEF, AAR)

• Physical attack (frost, frost + salt, abrasion, cracks)

Most physical-chemical deterioration processes are strongly influenced by the degree of saturation of

the concrete pores

• Carbonation occurs only at intermediate degrees of saturation

• Frost damage happens only when concrete is near saturation

• Alkali-silica gel can expand only in the presence of moisture

• Chemical attack can only happen through aqueous solutions of the aggressive components

• Corrosion reactions need a conductive electrolyte to progress (moist concrete)

Classification of Concrete Deterioration Processes

Performance Testing of Concrete

indirect

performance tests

direct

performance testsExposure classes (EN 206)

XD – Corrosion induced by chlorides other than from sea water

XS – Corrosion induced by chlorides from sea water

XC – Corrosion induced by carbonation

XF – Freeze-thaw attack

XA – Chemical attack

cause of

deterioration

chloride pitting

corrosion

carbonation/

corrosion

freeze thaw

sulfate attack

chemical attack

(pH, NH+,Mg2+,..)

chloride diffusion ASTM C 1556

chloride permeability ASTM C 1202

chloride migration SIA 262/1-B,

NT Build 492

electrical resistivity RILEM TC 154

AASHTO TP 95

Penetrability Tests

water penetration EN 12390-8

capillary water absorption / porosity

SIA 262-1/A

O2-permeability RILEM 116-PCD

on-site permeability SIA 262-1/E(Torrent)

O2-Diffusion EMPA

critical chloride content

RILEM TC

CTC

acc. carbonation

SIA 262-1/I,

CEN/TS

12390-12

nat. carbonation

RILEM CPC 18

General Tests

compressive strength EN 12390-3

sulfate resistance

SIA 262-1/DASTM C1012

freeze-thawresistance

SIA 262-1/C

Chloride resistance – Degradation mechanism

Na Cl+Ca (OH)2

Hydrated calcium aluminates

From C3A, C4AF, slag, FA

+

Calcium Chloroaluminates

« Friedels salt »

= Soluble CaCl2

RCPT - Chloride Permeability (ASTM C 1202)

60V DC during 6h

-> Charge Passed in Coulomb

…

…

Specific Resistivity [Wm] (RILEM TC 154, AASHTO TP 95)

Chloride Ion

Penetrability

Surface Resistivity Test

100-mm X 200-mm

(4 in. X 8 in.)

Cylinder

(KOhm-cm)

a=1.5

150-mm X 300-mm

(6 in. X 12 in.)

Cylinder

(KOhm-cm)

a=1.5

High < 12 < 9.5

Moderate 12 - 21 9.5 - 16.5

Low 21 - 37 16.5 – 29

Very Low 37 - 254 29 – 199

Negligible > 254 > 199

Chloride Migration or Resistivity (SIA 262/1-B, NT Build 492)

Sketch of test

Xd

measurementTest in progress

Correlation between W/C and maximum chloride migration coefficient DRCM*10-12

m2/s @ 28 days

0

5

10

15

20

25

0.35 0.4 0.45 0.5

Ch

lori

de

mig

rati

on

co

effi

cien

t D

RC

M*1

0-1

2m

2/s

W/C

CEM I

CEM III>50% slag

CEM I + 18-30% FA

2.5

8

11

Maximum chloride migration coefficient DRCM for various cover depths as function of binder type and exposure class for a design service life 100 years

Mean concrete cover depth over steel [mm]

Maximum value DRCM*[10-12 m2/s]

CEM I / OPCCEM III-A

36 - 65% slagCEM III-B

66 - 80% slagCEM II-B/V

20 – 30% FA

Reinforcing steel Pre-stressing steel XS2 / XS3 XS2 / XS3 XS2 / XS3 XS2 / XS3

35 45 1.5 1.0 1.0 5.5

40 50 2.0 1.5 1.5 10

45 55 3.5 2.5 2.5 15

50 60 5.0 3.5 3.5 22

55 65 7.0 5.0 5.0 30

60 70 9.0 6.5 6.5 39

Boldface values are practically achievable by present day concrete technology with currently used w/b Italic values are not achievable (lower values) or not recommended (higher values)

Slag / FA

OPC

The major features of the immersed tunnel solution includes

• 120 years Service life

• Over 18 km long with four tunnel tubes comprising

• Two double-lane motorway tubes

• Two rail tubes

• 79 standard elements every 217 m and 10 special elements for technical installations

• Construction time: 6.5 years

• Construction budget (2008 prices): 6 Billion US$

• Owner: the Danish state

The Fehmarnbelt Fixed Link will connect Scandinavia and continental Europe with a combined rail and road connection between Denmark and Germany.

Quantities• Concrete for elements 2.5 million m3• Reinforcement 0.3 million tons• Ballast concrete 0.4 million m3• Structural concrete 0.2 million m3• Cement 0.8 million tons

Solution for the precast elements - 24,10m length

SCC 50/60 –self compacting concrete for rank 2 elements

• Cement III A 42,5 N-LH with 50% GBFS

• w/c = 0,39

• Fly ash – 40 kg

• Ground limestone – 40 kg

• Fine sand (0-0,5mm) – 430 kg

• Sand (0,5-4mm) – 422 kg

• Crushed stones (4-8mm) – 337kg

• Crushed stones (8-16mm) – 454 kg

• SPL – 1,9%

• Air entertainer – 3%

Requirements – elements for 120 years Service life

• High resistance to Chloride attack

• Rc 6h – min. 10 MPa

• Rc 28d – min. 60 Mpa

• Very low permeability

Reasons of slag cement choice

Carbonation- Degradation mechanism

CSH

Poorly soluble Salts

CaCO3

DENSIFICATION, PROTECTION

CSH

Water

CO2

CALCITE

Ca(OH)2

Ca(OH)2 + CO2 + H2O CaCO3 + 2H2O

Drop in pH

13.0-12.5 < 9

Carbonation – effects

pH CH

External effect

EFFLORESCENCESE Steel corrosion (depasivation)

Internal effect

CO2

Spalling of concrete

Accelerated Carbonation (SIA 262-1/I,CEN/TS 12390-12)

Splitting of a slice Cleaning and spraying of indicator solution

Freezing color change Measuring carbonation depth

Photographic

documentation

Testing procedure according to SIA 262-1/Appendix

Design Live

Resistance to Carbonation

KN (mm/a)

50 years

XC3 & XC4 < 5.0

100 years

XC3 < 4.0

XC4 < 4.5

Sulphate resistance – Degradation mechanism

CaSO4 2H2O

Secondary gypsum

(causing internal

pressures)=

Hydrated

calcium

aluminates

+

C3A 3CaSO4 32H2O

Na2 SO4Ca (OH)2

+

Originating from ground water,

industrial environments, air

pollution, …and set regulator

0.1

1

10

100

(I) CEM I 52.5N

(II) CEM III/B42,5 L-

LH/HS/NA

(III) CEM III/A42.5N

(IV) CEMII/A-D

(V) CEM II/A-S 42-5R

(VI) CEM I52,5 R

(VII) CEMII/B-LL 32.5R

(VIII) CEMIV/A 32,5 R

(IX) CEM IV/B32,5 R

(Xa) BOS-Rheolith

(Xb) Durolith

rel.

len

gth

ch

ange

[‰

]

Sulphate Resistance

SIA 262-1/D, wz=0.40 SIA 262-1/D, wz=0.65 SIA 262-1 Limit

Sulphate Resistance of Concrete (SIA 262-1/A)

measured sulphate expansion of Dls [‰]

Sulfate Resistance

> 1.2 low

< 1.2 high

AGENDA

• Degradation mechanism

• Key durability indicators

Key challenges to cope with increasing society’s need for construction materials

• From prescriptive to performance based specification

Sustainable performing concrete

• What really matters to us

Durability of underground concrete

Conclusion

• Performance based specified sustainable concrete will be specified more often for its increased durability than for its strength

• Extended service life

• Better use of natural ressourses

• Lowest CO2 footprint / concrete m3

• There is a noticeable trend towards Performance Based Specifications (PBS)

• Specifiers and suppliers face a challenge in translating the long-term durability requirements into specifications for laboratory testing

• The efficiency of concrete as a sustainable construction material should be considered in a wider perspective than simply its unit price

• Concrete produced with blended cements have higher resistance to aggressive conditions (low permeability and chemical resistance)

Conclusion

THANK YOU