Performance-based Specifications: the Key to Optimising Concrete s Contribution to the Climate Change Challenge. Dr.

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1 Performance-based Specifications: the Key to Optimising Concrete s Contribution to the Climate Change Challenge Dr. Mark Richardson UCD School of Architecture, Landscape & Civil Engineering g 8 th May 2009 Earth Systems Institute University College Dublin esi.admin@ucd.ie Institiúid na gcóras Domhanda An Coláiste Ollscoile Baile Átha Cliath Web:

2 Concrete is... Concrete is dull grey stuff It has got to be good to be taken for granted

3 Concrete is... Aggregate Cement. just add water

4 Reinforced concrete: backbone of the world s infrastructure

5 Reinforced concrete: backbone of the world s infrastructure High strength Low cost Robustness Local availability Versatility Durability???

6 Key issues: Durability and Sustainability Over 0.25 million deficient concrete bridges in the United States kg CO 2 per tonne of cement kg CO 2 per tonne of concrete

7 Cement 3.8% World Resources Institute

8 Key issues in respect of the energy and climate change challenge: Durability and Sustainability of Concrete Infrastructure Efficiency Sufficiency i (Adrian Campbell, ARUP, 2009)

9 Performance-based Specification of Concrete: the key to Durability and Sustainability Cements and secondary cementitious materials Specification of durable concrete - prescription Specification of durable concrete - performance Addressing the energy and climate change challenge

10 Cements and secondary cementitious materials Portland Cement = Clinker + minor additions Blended cements = Clinker + other major Examples of major components» Limestone component + minor additions» Blastfurnace slag (GGBS)» Fly Ash (PFA)

11 Cement production Finely ground clinker + Gypsum = cement Limestone rock + Shale + Energy (1500 o C) = clinker

12 27 distinct cements are recognised in Europe Significant variety of cement chemistries available to be harnessed in matching the demands of durability with just the right capacity of material properties Efficiency, sufficiency

13 Type Designation Secondary Constituent Embodied CO 2 (kg/tonne) CEM I CEM I 930 CEM II CEM II/A-L, LL Limestone 6-20% CEM II/A-V PFA 6-20% CEM II/B-V PFA 21-35% CEM II/B-S GGBS 21-35% CEM III CEM III/A GGBS 36-65% CEM III/B GGBS 66-80% Same effect can be achieved by adding PFA or GGBS at the mixer British Cement Association

14 Specification of durable concrete - prescription Prior to the 1970 s the priority it was specification of strength From the 1970 s it was recognised that durability should be specified also Both factors are specified by prescription The prescriptive parameters are minimum strength, minimum cement content, and maximum water/cement ratio

15 Chronology

16 Formalised as Durability Grade Concept Strength implies min. cement content and max w/c

17 Weakness in Prescriptive Approach Does not prioritise durability over strength Does not explicity address sustainability and embodied CO 2 issue 2 Likelihood of over-specification, rather than provision of sufficiency high safety factor but potentially wasteful of resources Assumption of constant high standard of site practice in respect of curing

18 Durable and sustainable concrete: buy one, get one free (Prof. Ravindra Dhir, Dublin, 2008) Specify performance: efficiency, sufficiency

19 Specification of durable concrete - performance

20 Explicit Durability Design and Specification of durable concrete by performance Quantify durability threat Define service life Quantify level of acceptable deterioration Determine required material parameters

21 Example of quantifying the threat: Chloride ingress and corrosion of reinforcement Electrochemical process of corrosion is initiated if the chloride level at the reinforcement exceeds a critical level Chlorides migrate into concrete from exposure to seawater or de-icing salts

22 Electrochemical cell Anode Cathode Electrolyte

23 Electrochemical cell in reinforced concrete

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25 Method for Determination of Required Material Parameters Combination of Performance test methods Predictive models of deterioration ti

26 Lifetime Safety Factor Method P R(t) - S(t)< 0 T < P f max T = t mean t d = γ t t g

27 Performance-related design Quantify critical chloride level at reinforcement (C x, t ) State required service life (t) Estimate durability load from chloride source (C sn ) Specify cover to reinforcement (x) Solve for required material parameter of chloride resistance

28 Chloride penetration model based on Fick s Second Law of Diffusion for the non-steady state condition in a Crank s error function solution to Fick s Law C x, t = C sn 1 erf 2 x ( D t ) ca Solve to ascertain minimum value of material parameter (D ca )

29 Specify concrete based on a performance requirement of the required value of D ca Allow producer to use their skill to provide concrete with a sufficient value of D ca Test finished product ( what gets measured gets done ) (ECOserve 2006)

30 Recent developments in Ireland Specifiers practice is heavily influenced by explicit advice in standards documents Typically national standards permit the use of up to 70% GGBS with Portland cement (CEM I) Irish cement producers have responded to the CO 2 issue by replacing dominance of CEM I (930 kg CO 2 / tonne) by Limestone cement CEM II/A-LL or fly ash cement CEM II/A-V (both c.810 kg CO 2 / tonne) The National Standards Authority of Ireland have moved swiftly with the industry to update National Standards for concrete

31 To date the NSAI have modified the national standard to permit combinations of 50% GGBS with CEM II/A-LL and CEM II/A-V Following further research at UCD, using perfomance-based arguments, a proposal is currently being considered by the NSAI to increase this to 70% GGBS with CEM II/A-LL and CEM II/A-V The swift response of the NSAI will assist in meeting the energy and climate change challenge but current practice is potentially limited by being rooted in the prescriptive specification approach More can be achieved with performance-based specifications.

32 Addressing the energy and climate change challenge Golden opportunity for Ireland as we roll out NDP infrastructure Durability Sustainability Efficiency Sufficiency

33 Addressing the energy and climate change challenge UCD Earth Systems Institute Meeting the Challenge of Climate Change Smart technology: we have the basis of the technology, it just needs development Smart policy: we must provide the research data that t will facilitate t an editorial shift in standards documents from prescriptive i to performance-based specifications

34 Key UCD Message The Innovation Imperative: Productivity growth in the Irish economy has slowed to close to zero. The only way to rediscover productivity growth and be able to sustain it is by innovation and the embedding of the knowledge society. The Energy and Climate Change Imperative: We have hugely demanding energy and emission reduction obligations the only way to meet them is through the use of markets and innovation. The Earth Systems Institute response to these imperatives - We will be an engine showing how to use research and innovation smart technology and smart policy - to regain competitiveness and productivity, generate jobs and meet our energy and climate change obligations

35 Addressing the energy and climate change challenge Smart technology: we have the basis of the technology, it just needs development Smart policy: we must provide the research data that t will facilitate t an editorial shift in standards documents from prescriptive i to performance-based specifications

36 UCD Earth Systems Institute Meeting the Challenge of Climate Change Seminar Series In collaboration with Comhar Sustainable Development Council, Environmental Protection Agency, Forfás, Geological Survey of Ireland, Marine Institute, Met Éireann, Sustainable Energy Ireland & Teagasc Further details on the seminar series is available at A paper and podcast of this seminar will be available on the ESI website soon, please join the online ESI mailing list for such notifications ESI esi.admin@ucd.ie

37 UCD Earth Systems Institute Meeting the Challenge of Climate Change Seminar Series Next week...seminar #20 Friday 15 th May 2009 Royal College of Physicians, 12.30pm Dr. Brendan Williams UCD School of Geography, Planning & Environmental Policy Shaping the Dublin of 2020: meeting future challenges for managing the urban environment Further details available at