ASHTRANS Conference 7. September 2015 Claus Pade, Danish Technological Institute – Concrete Centre; cpa@dti.dk; +45 7220 2183

Carbon Footprint of Fly Ash

Hirtshals

Aarhus

Odense

Sønder Stenderup Taastrup

Warsaw

Gothenburg

Stockholm

Stavanger

Danish Technological Institute

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Content

Fly ash used for concrete production – benefits

Carbon Footprint of Fly Ash Concrete

Centre for Green Concrete (1998-2002)

Carbon Footprint of Fly Ash

Environmental Product Declaration of Fly Ash

All experience presented is based on data from Danish fly ash !

Lower cost at equivalent performance

Fly ash is cheaper per unit volume than cement

Better performance – (at equivalent cost or even at lower cost)

Lower heat development

Reduced shrinkage

Better flow properties (incl. stability)

Improved durability, e.g. resistance to chloride ingress

Fly ash in concrete – why?

Exposure class X0: no requirements to composition only strength (low)

50% or more fly ash

Slabs on ground (SCC)

Blinding layers

Etc.

Lower cost

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Vo

lum

en

Vand

Flyveaske

Cement

v/c = 0.50

k-faktor = 0.4

Fly ash concrete PC concrete

Vo

lum

e in

pas

te

cccccccccccccccccccccccc

Exposure class e.g. XS3: requirements to composition (max. fly ash)

Max 25% fly ash in powder (FA/CEM = 1/3) in DS 2426

Highway bridges

Marine structures

Deep foundation

Better performance

Center for Green Concrete 1998-2002

Carbon Footprint of fly ash concrete - DK

Environmental screening of ”Green” concrete highway bridge (in Danish)

Life cycle (50 years) CO2 inventory

http://www.gronbeton.dk/tidligere-projekter/groen-beton-i.aspx

From a concrete composition point of view the carbon footprint of concrete is dominated by the carbon footprint of the cement.

For severe exposure classes 1/3 of the cement may be replaced by fly ash according to DS 2426. From a performance based point of view higher replacement rates could probably be allowed.

For non-severe exposure classes higher replacement rates are allowed; in X0 no limit exist.

Carbon Footprint of fly ash concrete

Significant carbon footprint improvement is achieved from replacing cement by fly ash

In practice fly ash is in competition with other additions/powder (e.g. slag, limestone)

Started to see carbon footprint in concrete specifications

e.g. 400 kg CO2/m3 for the Copenhagen Metro extention ”Cityringen”

(2010)

18-34% fly ash in the concrete – most in deep foundation structures

Carbon footprint in specifications

Environmental Product Declaration

Sustainability in construction works R

EGU

LATE

D

Product level CPR (DoP, CE-marking)

Building level CPR and Eurocodes

VO

LEN

TAR

Y

Product level e.g. Nordic Swan, EEC Flower, EPD …

Building level e.g. DGNB, Bream …

Environmental

Product

Declaration

Declaration of

Performance

Construction

Product

Regulation

Environmental Product Declaration

Sustainability in construction works R

EGU

LATE

D

Product level CPR (DoP, CE-marking)

Building level CPR and Eurocodes

VO

LEN

TAR

Y

Product level e.g. Nordic Swan, EEC Flower, EPD …

Building level e.g. DGNB, Bream …

Environmental Product Declaration

Standards and PCR

Technical standards:

ISO 14044 (LCA)

ISO 14025 (EPD) (2006)

EN 15804 (EPD for construction products)

(2012)

Product Core Rules (PCR)

Product unit

Service life

Allocation procedures

And a lot more …

Environmental Product Declaration

EN 15804:2012

Environmental Product Declaration

EN 15804:2012, Tabel 3 – Impacts

Environmental Product Declaration

LCA (Life Cycle Assessment – ISO 14044)

Production Transport and construction

Use End of use

Extraction and/or production of raw

material Transport Production process + +

Waste management

Environmental Product Declaration

EN 15804:2012

EPD in the Danish Concrete Industry

Cradle to gate approach

Included Excluded

Construction site

Concrete plant

EPD in the Danish Concrete Industry

Published EPD’s

Ready Mix Concrete Industry – average EPD’s for 5 typical concrete mix designs can be seen on the website based on specific data and generic data (GaBI) – ”Cradle to gate” www.danskbeton.dk

Prefab industry – average EPD’s for 6 typical prefabricated walls based on specific data and generic data (GaBI) – ”Cradle to gate” www.danskbeton.dk

The EPD’s for Danish Concrete Products are using a Danish EPD for Fly Ash in the calculations

Higher strength Severe exposure

2/3 from Portland cement

Lower strength Non-Severe exposure

Environmental Product Declaration for Fly Ash - DK

Environmental Product Declaration for Fly Ash – DK – Carbon Footprint

Declared Unit = One tons of Fly Ash

Cement: 800 kg CO2-ækv.

Environmental Product Declaration for Fly Ash – DK

EPD Calculations based on:

Fly Ash is a co-product according to the definition in the waste Directive from 22.11.2008 (2008/98/EC) article 5, which means

The impact from production of fly ash shall be allocated, but can be neglected if processes is generating a very low contribution

Environmental Product Declaration for Fly Ash – Gabi Data

Declared Unit in the table = One kg of Fly Ash

Allocation has been done – makes a huge difference

Carbon Footprint = 201 [kg CO2-Equiv]/[tons Fly Ahs]

Environmental Product Declaration

Standardisation work in CEN TC/350 CENSustainability of construction works — Guidance for the implementation of EN

A guidance to EN 15804 is under development

Allocation rules are discussed

The 1,0 % cutt of rule is probably being changed

DTI – Danish programme operator

If you should be in need of a 3rd party verified EPD !