Life cycle assessment (LCA) of benchmark concrete

Int J Life Cycle Assess DOI 10.1007/s11367-017-1266-2

REGIONAL TOPICS FROM AUSTRALIA, NEW ZEALAND

Life cycle assessment (LCA) of benchmark concrete products in Australia James Mohammadi 1 & Warren South 1

Received: 29 June 2016 / Accepted: 16 January 2017 # Springer-Verlag Berlin Heidelberg 2017

Abstract Purpose A comprehensive Life Cycle Assessment (LCA) study was performed to investigate the environmental impacts associated with the manufacture of fourteen benchmark concrete products in Australia including concrete, mortar, grout and render. This study provides datasets for the reference cementitious construction materials which aid the construction industry to evaluate the environmental impact of construction more consistently. In addition, an appropriate formulation for the manual calculation of the environmental impacts of customised concrete mix-designs was investigated. Methods Benchmark products were defined based on the average mix-design currently applied by the concrete industry and in compliance with the Australian cement and concrete standards. Normal and special grade concretes with strength in the range of 20 MPa to 100 MPa, mortars type M1 to M4, as well as grout and render were defined. The cradle-to-gate LCA model for each product was defined based on the ISO Standards 14040 and 14044 frameworks and in conjunction with modules A1 to A4 of European Standard EN 15804. GaBi software program version 7.2.2 was applied to ensure

Responsible editor: Barbara Nebel Electronic supplementary material The online version of this article (doi:10.1007/s11367-017-1266-2) contains supplementary material, which is available to authorized users. * James Mohammadi [email protected]

1

Cement Concrete & Aggregates Australia (CCAA), PO Box 124, Mascot, NSW 1460, Australia

consistency and reproducibility of the environmental impacts for each product. The major impact classes were determined and discussed using Life Cycle Impact Assessment (LCIA) CML 2001 classification. Results and discussion Results showed that in all cases cement had the highest contribution to the impacts of concrete products. Using less cement in concrete products either by substitution of it with supplementary cementitious products or manufacturing cement with increased mineral additions has the potential to reduce environmental impacts. It was found that the Global Warming Potential (kg CO2-Eq per cubic metre) of the products ranged from 209 to 521 kg. Other regional environmental impacts, such as acidification, ozone layer depletion, and eutrophication, were also investigated and reported for each product. It was found that acidification was in the range of 0.670 to 1.609 kg SO2-Eq, and eutrophication was in the range of 0.108 to 0.259 kg Phosphate-Eq per cubic metre of concrete products in Australia. Conclusions Establishing the industry reference point for cementitious products supports sustainability in production and enables tracking of future changes in the emissions of cementitious construction materials to ensure that concrete products are the responsible choice for construction. The decrease of cement clinker content through increasing mineral (limestone) addition is strongly suggested. In addition, the reported method for approximating environmental impacts of other concretes with customised mix-designs was found accurate and applicable. Keywords Acidification . Cement . Concrete . Eutrophication . Global warming . Grout . Life cycle assessment (LCA) . Life cycle impact assessment (LCIA) . Mortar . Ozone layer depletion . Render

Int J Life Cycle Assess

1 Introduction Cementitious material including concrete, mortar, grout and render are the most widely used materials in the building construction industry (Habert et al. 2011). Previous studies have discussed methods for the calculation of the primary energy and associated emissions in concrete and other cementitious products (Prusinski et al. 2004; Sjunnesson 2005; Flower and Sanjayan 2007). However, due to lack of transparency, unavailability of local inventory data, differences in scope, assumptions and system boundaries there has been an inconsistency in the outputs presented by these studies. They are therefore not easily applied by decision makers and design engineers to compare the primary energy requirement and the environmental impacts of different construction options. The majority of variations observed in comparative studies have been shown to arise from differences in assumptions, system boundaries of assessment and lack of accurate input data (Hobday 2006). The initial step of this study is to define a range of benchmark cementitious products that represent the current commercial construction products in the market. This study has been completed in 2016 and provides a transparent framework for the environmental calculations of different concrete products based on the most recent available local industry data, collected from the industries involved in production of concrete, to overcome the scepticism and uncertainty associated with the application of the current LCA. The outcomes of this study can be primarily used by the construction industry. This includes engineers, designers and the academic community who can use the provided information regarding the environmental impact of benchmark concrete products in Australia, as reliable and consistent datasets for investigating the Life Cycle Assessment (LCA) of whole buildings. Although the life cycle assessment has been widely applied to construction materials (Prusinski et al. 2004; Sjunnesson 2005; Flower and Sanjayan 2007; Grant 2015), lack of such assessment for the benchmark construction materials, and specifically concrete products with standard mix designs for different applications, has led us to perform this research. This study does not make any comparative claims against other product types; however it can help the construction industry in different ways such as providing a clearer picture regarding the possibility of eco-improvements in the existing concrete products. Over time, various improvements in the manufacturing of benchmark products can also be tracked through the regular LCA dataset updating of the discussed concrete and mortar products.

2 Methodology and definitions of benchmark products This research has applied the ISO 14040 (2006) and ISO 14044 (2006) assessment frameworks, in conjunction with

the European Standard EN 15804 (The European Committee for Standardization (CEN) 2012), to provide a holistic cradleto-gate insight into the relevant environmental impacts from the production of benchmark concrete grades and other standard concrete products. The cradle-to-gate life cycle stage provided in this report complies with the BS EN 15804 (The European Committee for Standardization (CEN) 2012) and the EPD UN CPC 375 Concrete report published by (UN CPC 375 2013). It consists of four stages as follows: & & & &

Module A1: Extraction and processing of raw materials and processing of secondary materials; Module A2: Transport to the manufacturer; Module A3: Manufacturing, including impacts from direct energy generation and waste disposal related to the manufacturing process; Module A4: The transport to construction site stage;

The main environmental impact categories relevant to the production of concrete, such as global warming, acidification, and eutrophication are addressed by Section 6.5 of Standard EN 15804 (The European Committee for Standardization (CEN) 2012). These impact categories are affected by one or more of the main emissions such as CO2, SO2, and NOx and therefore, it is very important to consider a proper effective scale for the impact categories of different emissions. Classification is assignment of LCI-results where the impact categories (e.g. global warming, acidification) are defined and the connections from the inventory are assigned to impact categories for different problem areas. The Life Cycle Impact Assessment (LCIA) discusses the environmental impact of manufacturing different grades of benchmark concrete and other cementitious products in regional and global impact areas. It should be considered that LCIA results are relative expressions and do not predict impacts on category endpoints, the exceeding of thresholds, safety margins or risks. Life cycle impact assessment indicators have been chosen and discussed by Annex C of EN 15804 (The European Committee for Standardization (CEN) 2012). This Annex provides the practitioner with the sources of recommended LCIA methods. The EN 15804 standard states that the impact assessment should be carried out for certain impact categories as shown in Table 1. There is a need to specify the reference such as scientific articles or the software program used for the calculation of each impact category, as the LCA can be conducted using several methods and characterisation factors within one impact category. The major impact classes were calculated using LCIA CML 2001 classification (GaBi - CML 2001 2013) provided by GaBi software program (PE International (thinkstep) 2016). The references for impact classes are shown in Table 1. Concrete is batched, ordered and supplied based on volumetric units. In some countries such as Australia or the European countries, concrete is specified using the unit of

Int J Life Cycle Assess Table 1

The impact categories sourced from GaBi software program (PE International (thinkstep) 2016)

Impact category In EN 15804

Indicator parameter in EN 15804

Unit of LCIA indicator

Sources of LCIA method

Global Warming

Global warming potential, GWP

kg CO2 Equiv

CML2001 - Apr. 2013, Global Warming Potential (GWP 100 years) [CML 2001 - Apr. 2013] 1

Acidification

Acidification potential of soil and water, AP;

kg SO2 Equiv

CML2001 - Apr. 2013, Acidification Potential (AP) [CML 2001 - Apr. 2013]

Eutrophication

Eutrophication potential, EP

kg Phosphate Equiv

CML2001 - Apr. 2013, Eutrophication Potential (EP) [CML 2001 - Apr. 2013]

Ozone depletion

Depletion potential of the stratospheric ozone layer, ODP

kg CFC 11 Equiv

CML2001 - Apr. 2013, Ozone Layer Depletion Potential (ODP, steady state) [CML 2001 - Apr. 2013]

Photochemical ozone creation

Formation potential of tropospheric ozone, POCP;

kg Ethene Equiv

CML2001 - Apr. 2013, Abiotic Depletion (ADP fossil) [CML 2001 - Apr. 2013]

Depletion of abiotic resources: elements

Abiotic depletion potential (ADP-elements) for non-fossil resources Abiotic depletion potential (ADP-fossil fuels) for fossil resources

kg Sb Equiv

CML2001 - Apr. 2013, Abiotic Depletion (ADP elements) [CML 2001 - Apr. 2013]

MJ, net calorific value

CML2001 - Apr. 2013, Photochem. Ozone Creation Potential (POCP) [CML 2001 - Apr. 2013]

Depletion of abiotic resources: fossil fuel

1

more information regarding CML 2001 can be found in GaBi - CML 2001 (2013)

cubic metres, while in the United States cubic feet (35.31 cu ft. = 1 m3) is the common unit used for batching, ordering and suppling concrete. The primary purpose of the LCA carried out on cementitious products is to provide a comprehensive up-to-date environmental data catalogue for each benchmark concrete product at a functional unit of 1 m3 for fresh concrete that can be used by design engineers and decision makers to compare the environmental impacts of construction building materials. The inventory analysis involves data collection and calculation procedures to quantify relevant inputs and outputs of a benchmark product within systems of boundary as shown in Fig. 1. The current status of the concrete production in

Product A: Cement (Cradle-to-gate) ∑energy Ai

∑raw materials Ai

General Purpose Cement

Product C: Building Lime Product Bi: Supplementary Cementitious Materials (Gate-to-gate) (Cradle-to-gate) ∑raw ∑upstream energy and emissions ∑energy Ci materials C i (allocated by price) Bi b1: Fly ash b2: GGBFS

∑emissions Ai

∑transport A

b3: Amorphous Silica

∑preparation energy Bi

Product D: Water (Cradle-to-gate) ∑raw ∑energy Di materials D i Water

Admixtures

∑emissions Ci

∑emissions Di

∑emissions Ei

∑transport C

∑transport D

H: Production of a Benchmark Product (Gate-to-gate) ∑transport G

Product F: Fine aggregates (Cradle-to-gate) ∑raw ∑energy Fi materials Fi

Product G: Coarse aggregates (Cradle-to-gate) ∑raw materials Gi ∑energy Gi ∑emissions Fi

Coarse aggregates

Product E: Admixtures (Cradle-to-gate) ∑energy Ei

Building Lime

∑transport B=∑transport b1+∑transport b2+∑transport b3

∑transport F

Fine aggregates

Australia is estimated to be 26 million cubic metres. This report covers concrete production data from the main Australian concrete producers such as Boral, Hanson, and Holcim which covers 90% of the total premixed concrete production in Australia. This study does not make any comparative claims against other product types. Following the discussed comparability criteria in Section 5.3 of EN 15804, only environmental data of other construction products can be compared with the results of the current study if the system of boundary for those products includes: (a) production stages for modules A1 to A4, (b) all types of energy usage in the system, including allocated primary and secondary

∑emissions Gi

Fig. 1 System of boundary for the production processes for concrete products

∑ Production emissions Hi Transport to construction sites

∑Production energy Hi


(electricity) energy usage and associated emissions for the production of supplementary cementitious products, primary energy usage and emissions for the production of electricity or landfill of clinker dust, and (c) all types of materials usage in the system, including upstream materials such as water usage for the production of electricity and quarrying of raw materials. Cementitious products are defined in compliance with the requirements of product category rules discussed in the World Business Council for Sustainable Development (WBCSD) document (UN CPC 375 2013). Cementitious products are materials formed by mixing cement, coarse and fine aggregate and water, with or without the incorporation of admixtures or additions, which develops its properties by the hardening of the cement paste (UN CPC 375 2013). Australian Standard AS 3600 classifies cementitious materials into four main classes: Concrete, mortar, grout, and render. Based on the properties, performance requirements, and applications, some of the main class products such as concrete are sub-classified by the Australian Standard AS 1379 into normal and special grades. Table 2 presents the properties and performance requirements of benchmark mixes for different grades of concrete and other cementitious materials. The provided classification from AS 3600 is congruent with the provided product categories mentioned in UN CPC 375 (2013). Accordingly, the relevant product categories for each benchmark product have been indicated based on both (AS 3600 & WBCSD) systems in Table 2. In addition, other properties of each benchmark product including compressive strength, slump, product application, and the exposure conditions are provided in Tables 2 and 3. The selected benchmark products represent the average properties products supplied by major concrete suppliers in Australia that are widely used for construction applications. The selected benchmark mix designs comply with the requirements of the relevant Australian Standards as shown in Table 2. Table 3 specifies the construction applications of the benchmark products. On the one hand, specifying benchmark products based on their applications can be helpful to compare the eco-performance of different benchmark products for a construction application. On the other hand, it can assist the proper selection of cementitious products to perform LCAs for a whole building construction analysis in the future. One outcome of this study is to establish a baseline for the required primary energy and associated emissions of cementitious construction materials in Australia. The effect of future changes and improvements to production processes for construction cementitious materials can then be tracked by regularly updating the required primary energy, raw materials consumption, and associated emissions data. The regular assessment of the benchmark products assists sustainability of production of cementitious materials in Australia. It also

facilitates the recognition of the level of effectiveness for different policies and strategies that are applied over time, with a significant potential in theoretical study as well as industrial applications. The source of materials, including technology of production processes, transport distances, and source and quality of raw materials, used for the production of the benchmark products influence the primary energy and associated emissions of the final products. A comprehensive study of all industries contributing to the production of concrete was undertaken to provide a complete set of Australian data regarding the required primary energy intensity and associated emissions for the different materials that are involved in the production of concrete, mortar, grout and render. The information was provided by the cement, aggregates and concrete industries in confidence, but the aggregated results are presented for each of the benchmark products. The procedure of aggregating cement and aggregates data from different resources leads to approximations and estimations. Industry datasets have various quality levels and it is required to assign appropriate weights to each industry dataset before aggregating them. Moreover, the variation in input data and its effect on the results of the LCA analysis have been discussed in Section 5 BData Quality, Limitations, Variation of Results and Sensitivity Analysis^. A complementary literature review was also undertaken with the results of the current study crosschecked against the data from the literature review. The comprehensive literature review provided information to fill the gaps for some inputs, such as inventory data and emissions for concrete admixtures, for which limited local data are available. The primary energy requirement and associated emissions for some of the upstream activities (primary activities), such as electricity production, fuel production, transportation, quarrying of raw materials, and land filling of waste products were considered in the GaBi model using the available GaBi software pre-defined process datasets (see notes of Table 4). Although Australian datasets from GaBi software program were used for the primary Australian energy and material resources, such as electricity, fuel and coal, in some cases where the Australian datasets were not available (i.e. quarrying of bauxite), datasets from other regions were used (see Table 4). Another limitation of this research was the use of average Australian data for items such as electricity, coal and petrol, etc. As an example the Australian mix grid electricity is generated from coal (49.4%), lignite (34.2%), and natural gas (14.2%). However, in different regions the variation in the proportion of primary resources of electricity production may lead to a variation in the range of 2 to 4% in the final results of this study. The current study calculated the impact classes using LCIA CML 2001 factors. Although LCIA CML 2001 GWP factors have been specified by EN 15084, they are not aligned with current values of The Intergovernmental Panel on Climate Change (IPCC). Another limitation of this

8

7

6

5

4

3

2

1

1.6 2373

2.0 2373

4.0 2391

6.0 2410

80 20 20 680 970 174

460 0

AS1379

2.0% 0.30

80 MPa 160 mm

C80/95 12,000 Psi

S80

8.0 2427

80 40 20 724 920 165

470 0

AS1379

2.0% 0.27

100 MPa 200 mm

C100/115 15,000 Psi

S100

no 1808

0 0 0 1322 0 216

0 270

AS3700

6.0% 0.80

NA NA

Mortar Mortar

M1 Mortar Standard Mortar

no 1967

0 0 0 1362 0 215

220 170

AS3700

6.0% 0.55

NA NA

M2

The addition of admixture is optional but was included in calculations

Fine aggregates in normal grade concretes include mix of 50/50 natural/manufactured sand; other cementitious materials include only natural sand

Specified based on the regional NSW/Victoria States standards

According to American Concrete Institute code ACI 318(2014)

There is no equivalent grade in the European code for the Australian grade S65, it stands between European grades C60/75 and C70/85

According to the Eurocode2 EN1992–1-1(2008) and BS EN 206(2013)

According to the classification mentioned by UN CPC 375 (2013)

According to the classification provided by Australian Standard AS 3600 (2009) and AS 1379 (2007)

1.5 2356

3.3 2373

1.3 2335

30 70 10 669 1000 178

Admixture Unit weight

35 65 0 700 1060 181

40 80 0 620 1065 185

0 55 0 831 1045 165

0 40 0 938 1000 156

GGBFS Fly ash Amorphous Silica Fine aggregates 7 Coarse aggregates Water

0 50 0 907 1015 162

430 0

65 MPa 120 mm

380 0

50 MPa 80 mm

NA 4 10,000 Psi

AS1379

40 MPa 80 mm

C50/60 7000 Psi

AS1379

32 MPa 80 mm

C40/50 6000 Psi

2.0% 0.33

25 MPa 80 mm

20 MPa 80 mm

C35/45 5000 Psi

Special

S65

2.0% 0.37

C25/30 4000 Psi

C20/25 3000 Psi

N50

Air Content 4.0% 3.0% 2.5% 2.0% Water to Cement 0.65 0.60 0.50 0.42 Other requirements of final products (compliance with standards) Standard Code AS1379 AS1379 AS1379 AS1379 Mix design constituents (kg/m3) GP cement 200 220 275 330 Building lime 0 0 0 0

f’c28day Slump/Flow

Equivalent American Performance requirements

5

Equivalent European 3

EPD product category 2

Identities Main Class 1 Grade class

N20 N25 N32 N40 Concrete Normal Ready mixed concrete (unreinforced concrete)

Properties and performance requirements of the Australian benchmark cementitious products

Product definitions

Table 2

0 0 0 1458 0 225 1.5 8 2183

1.0 8 2090

420 80

AS3700

2.5% 0.45

NA NA

M4

0 0 0 1422 0 223

320 125

AS3700

3.5% 0.50

NA NA

M3

1.5 2310

0 0 0 1538 0 220

1.5 2267

0 0 0 1625 0 240

400 0

NA 6

NA 6 550 0

2.0% 0.60

NA NA

render render

2.5% 0.40

40 MPa 30 Sec

grout grout

GR RN grout render Industrial



Applications of the Australian benchmark cementitious products

Cementitious products

Label

Applications

Normal grade concrete 20 MPa

N20


N25

Footpaths, residential parking area and driveways, pavements for local streets (max vehicle mass < 3 t), foundation and concrete dams House slabs (slabs on ground), residential beams and columns, rigid pavements (3 t < max vehicle mass < 10 t), and concrete dams


N32


N40


N50

Special grade concrete 65 MPa

S65

Special grade concrete 80 MPa Special grade concrete 100 MPa

S80 S100

Columns of high-rise buildings, bridge beams Columns of high-rise buildings, bridge beams

Standard grade mortar type I

M1

With unreinforced fired clay masonry, and exposure condition specified in AS 3700

Standard grade mortar type II

M2

Standard grade mortar type III

M3

Standard grade mortar type IV

M4

Highways pavements, residential beams and columns, suspended slabs, bridge decks, shear walls, and concrete walls Residential beams and columns, suspended slabs of high-rise buildings, and high detailed walls with fine finishes Precast and in situ bridge girder, bridge pillars, prestresses slabs, concrete arches, and suspended precast beams Precast and in situ bridge girder, bridge pillars, prestresses slabs, concrete arches, and suspended precast beams

Grout

GR

With unreinforced fired clay masonry strength range 5 to 30 MPa or concrete masonry density < 1800 kg/m3, and exposure condition as specified in AS 3700 All applications with masonry produced by fired, concrete masonry, calcium silicate, strength range > 30 MPa or concrete masonry density > 1800 kg/m3, and exposure condition as specified in AS 3700 All applications with masonry produced by fired, concrete masonry, calcium silicate, strength range > 30 MPa or concrete masonry density > 1800 kg/m3, and exposure condition as specified in AS 3700 Levelling, joint fillings, and filling prestressed ducts

Render

RN

Surface of walls, decoration and durability of exposed concrete surfaces

study was the selection of the best LCIA method for the calculation of environmental impacts. Whilst CML method has been confirmed as a general practice method that complies with EPD requirements and can be considered as best practice for many of the impact classes in Australia (Renouf et al. 2015), there still is no consensus on the best method for weighting and normalisation of results in Australia.

3 Inventory analysis 3.1 General Purpose (GP) cement Literature showed that LCAs of cement production may vary based on: the differences in processing technologies of cement plants, the defined system boundaries and the geographical variations within their scopes. However, the production processes for General Purpose (GP) cement commonly include, extraction and preparation of raw materials, pyroprocessing and grinding of clinker with gypsum (Petek Gursel et al. 2014). Different types of integrated cement plant technology can be classified based on the kiln operation. Boesch et al. (2009) discusses the thermal energy efficiencies of the different kiln technology processes. Kilns employ either wet or dry processes, with the dry procedure estimated to be up to 50% more

efficient (Treloar et al. 2001). Data relating to cement manufacturing materials flow and emissions have been collected annually from different sources in the period of 2011 to 2014 and were cross checked with other available published resources. During this period the applied manufacturing technology used for the production of cement and clinker has not changed noticeably. Data from major cement producers across Australia were included, which represents almost 95% of actual cement supply in Australia (see Table S1 of Supplementary Materials NO 1 ). A summary of the Australian inventory data relating to years 2010 to 2015 is shown in Table 5. The consumption of raw materials for the production of cement were investigated thoroughly, and quantified for the production of a kilogramme of cement. Limestone and other carbonate sources, sand and shale are the most used materials in the production of cement. The primary energy required for quarrying and transportation of raw materials was modelled using GaBi software program. Josa et al. (2004) reported that quarrying and transportation of raw materials consumed 1– 3% of primary energy consumption for cement production (Josa et al. 2004), which was confirmed by this study to be 2.85%. In addition, 2.6% of primary energy consumption for cement production was due to the preparation (drying and grinding) of raw materials in cement plants which should be added to this figure.


The process/flow information used for modelling cement in GaBi software program

Inventory Materials

Production process (energy and emissions) Production Process of Object 1 Self-defined Clinker (CCAA)

Name Clinker

Category Intermediate-inventory material

Limestone

Raw materials

AU: Limestone CCAA 2

Limestone (calcium carbonate) [Non-renewable resources]

Bauxite

Raw materials

AU: Bauxite CCAA 3

Iron Oxides Sand Gypsum Shale (clay based) Potable Water Raw Water Recycled Water

Raw materials Raw materials Raw materials Raw materials Raw materials Raw materials Raw materials

AU: Iron Oxides CCAA 4 AU: Silica sand CCAA 5 AU: Gypsum stone CCAA 6 AU: Shale CCAA 7 AU: Tap water CCAA 8 -

Bauxite [Non-renewable resources] Iron ore (65%) [Non-renewable resources] Sand [Non-renewable resources] Gypsum [Minerals] Clay [Non-renewable resources] Water (fresh water) [Water]

Slags Fly Ash

Waste/input Waste/input

Considered by product Considered by product

Clinker Dust Electricity Coal

Waste/output Conventional fuels Conventional fuels

AU: Landfill of Clinker Dust CCAA 9 AU: Electricity grid mix AU: Hard coal mix PE

Blast furnace slag [Waste for recovery] Fly ash (unspecified) [Waste for recovery] Inert chemical waste [consumer waste] Electricity: consumption mix, at consumer [Electric power] Hard coal Australia [Hard coal (resource)]

Natural gas Coke Diesel Oil Gasoline Alternative fuels 10

Conventional fuels Conventional fuels Conventional fuels Conventional fuels Alternative fuels

AU: Natural gas mix PE EU-27 Petrol coke at refinery PE AU: Diesel mix at filling station PE AU: Gasoline mix at filling station PE AU: Kiln Alternative Fuels CCAA

Natural gas Australia [Natural gas (resource)] Petrol coke [Refinery products] Light fuel oil [Refinery products] Gasoline (regular) [Refinery products] Alternative fossil fuels [Resources]

Inventory Flow Object

Water (ground water) [Water] Internal recycled or reused water [Operating materials]

1

The primary energy requirements for the quarrying of raw are reported in Table 6

2

Quarrying process of (AU: Limestone CCAA) is defined based on GaBi dataset (DE: Limestone (CaCO3) PE)

3

Quarrying process of (AU: Bauxite CCAA) is defined based on GaBi dataset (EU-27: Bauxite PE)

4

Quarrying process of iron oxide materials is assumed to generate same emissions and require same energy to Bauxite (due to similar hardness)

5

Quarrying process of (Silica sand CCAA) is defined based on GaBi dataset (DE: Silica sand PE)

6

Excavation (AU: Gypsum stone CCAA) is defined based on GaBi dataset (DE: Gypsum stone (CaSO4-Dihydrate) PE)

7

Quarrying process of Shale materials is assumed to generate same emissions and require same energy to Gypsum, due to similar hardness

8

Production process (AU: Tap water CCAA) is defined based on GaBi dataset (EU-27: Tap water PE)

9

Landfilling (AU: Landfill of Clinker Dust CCAA) was defined based on GaBi dataset (data EU-27 Landfill of glass/inert waste PE)

10

Alternative fuels energy was 19.954 MJ/kg; Alternative fuels emissions are shown in Table S3 Supplementary Material NO 1

In Japan, kiln systems consist of suspension preheater kilns (SP kiln) or suspension preheater kilns with a precalciner (NSP kiln) with production proportioning of 15% and 85%, respectively (Japan Cement Association (JCA) 2015). Thermal energy requirement of the cement industry in Japan was reported to be 3300–3400 MJ/ t clinker, whilst 17.2% of that energy was driven from alternative fuels (Japan Cement Association (JCA) 2015). Moreover, electricity usage was reported to be 108 kWh per tonne of cement production in Japan (Japan Cement Association (JCA) 2015). China is by far the largest cement producer with 46% of world cement production (International Energy Agency 2007). Li et al. (2014) discussed clinker production in China including thermal energy usage of 3751 MJ/ t clinker, COs2 emissions of 807 kg/ t clinker (Li et al. 2014). More details about cement and clinker production

in China are demonstrated in Tables S6 and S7 of Electronic Supplementary Material NO 1. In Europe, electricity consumption per tonne of cement was reported between 90 to 120 kWh of which about 30–35% was used for cement grinding (Boesch and Hellweg 2010). In the U.S., electricity consumption per tonne of cement is 142 kWh, of which 40% was used for grinding in cement milling (Worrell et al. 2000). This is in the same range as that of the European cement industry (90–120 kWh) (Boesch and Hellweg 2010), slightly higher than Japan (108 kWh) (Japan Cement Association (JCA) 2015). The cement kiln process is efficient and effective when using alternative fuel resources (AFRs) (secondary fuels as discussed European Standard EN 15804 (The European Committee for Standardization (CEN) 2012)). Nitrogen oxide (NO x ) emissions are reduced through the use of


Summary of the Australian inventory data and environmental effect of cement manufacturing process

The General Purpose (GP) cement composition: Clinker 87.5% - Minerals 7.5% - Gypsum 5% AS 3972 (2010) Total manufactured cement in Australia: 9.1 million tonne (Cement Industry Federation (CIF) 2014) Domestic clinker production: 5,941,500 tonne (66.3%) - Imported clinker: 3,025,750 tonne (33.7%) (The current study industry data) Main clinker importing countries: Japan 65% - China 30% - Indonesia and other countries 5% (Cement Industry Federation (CIF) 2013) Kilns operating systems: Suspension preheater precalciner 90% - Long wet kiln technology 8% - Short dry grate preheater 2% (Cement Industry Federation (CIF) 2014) Electricity consumption 115 kWh per kg of cement: Materials preparation 16% - Clinker production 31% - Cement milling 48% - Other activities 6% (The current study industry data) Alternative fuels resources (AFRs) ratio of total thermal energy: 9.3-10% in 2014 (Cement Industry Federation (CIF) 2014) Cement production Stages in Australia Environment related activities associated with each stage Production of clinker 1: Raw materials extraction 2: Crushing 3: Prehomogenisation 4: Grinding 5: Preheating 6: Rotary kiln 7: Cooler 8: Clinker storage Production of cement using either imported or domestic clinker 9: Minerals addition (7.5%), gypsum addition (5%) 10: Cement grindings and finishing 11: Cement storage silo These materials are primarily obtained from mines and in some cases from sources such as shell sand. The main emissions from the extraction of raw materials are dust emissions to air and emissions to water due to quarrying. Emissions mainly from the use of electricity for crushing industrial by2 Crushing: The use of industrial by-products (waste) is common products. The alternative materials include alumina by-products and pig-iron practice within the Australian cement industry. slags from the industry. 3 Prehomogenisation: Raw materials are transported to the cement The potential for fugitive dust emissions is minimised through careful design plant using conveyors, road, rail or sea transport. of the transportation systems. Emissions mainly from the use of electricity for crushing. Additional 4 Grinding: Raw materials are homogenised on arrival at the cement emissions from the use of natural gas and coal are also included. Baghouse plant in preparation for raw milling. After precise proportioning, raw filters or electrostatic precipitators remove particles from kiln and mill exhaust materials are finely ground, dried and further blended in the raw mill. gases. 5 Preheating: Raw materials are heated to around 900°C in counter- Various emissions to air from clinker manufacture include NOx, SO₂, and flow heat exchange resulting in the de-carbonation of calcium particulate emissions. The majority of CO₂ emissions arise from the clinker carbonate in the raw mix. production process. 6 Rotary kilns: Clinker production requires further heating of raw NOx, SO₂, and CO₂ emissions arise. Alternative fuels, such as waste tyres, materials to 1450°C in the rotary kiln. At this temperature, raw waste oil and spent solvent, can be used in the kiln, reducing the consumption materials are transformed into clinker. of fossil fuels and often reducing emissions. 7 & 8 Clinker cooling and storing: Clinker is rapidly cooled to ensure the desired mineralogy is formed in the final product. Then, clinker is Emissions mainly from the use of electricity for cooling systems. stored on site until required for grinding into cement. 9 & 10: Cement grindings with minerals addition: Clinker is ground Emissions from the use of electricity for grinding mineral additions and SCMs with gypsum and supplementary cementitious materials and mineral including limestone, GGBFS and power station fly ash. additions (including limestone) to form the final cement product. 1 Raw materials extraction: The main raw material for cement manufacture is limestone. Other raw materials include shale, clay, bauxite, iron ore and sand.

alternative fuels, while utilising bag filters on kilns ensures that there is no increase in particulate emissions (Cement Australia 2015). It is reported that the current fuel substitution rate is 18% in Europe and 11% in the USA (Boesch and Hellweg 2010), whilst the calculated usage of alternative fuels in the Australian cement industry was 9.3% per net calorific value. CO2 emissions from cement production are classified into three categories: process, non-process and other emissions. Non-process CO2 emissions, includes CO2 emissions from

the combustion of fuels or usage of electricity and is determined in Tables S3 and S4 of Electronic Supplementary Material NO 1. Details about the thermal energy and electricity requirements for different stages of cement production are reported in Table S6 of Electronic Supplementary Material NO 1. The primary emissions from electricity usage and quarrying of raw materials and production of fuels were considered in the model using the available pre-defined process datasets in GaBi software as presented in Table 4. Process CO2 emissions arise from the chemical reaction (calcination)


Major inventory data associated with the production of 1 kg of different aggregates

Resources

Aggregates in Cement production (raw materials)

Item

Limestone Bauxite

Energy (MJ)3

7.83E-02

Emissions (kg)4 CO2eq CO NOx SO2 Dust ≤ PM10 Water (kg)5 Source of data

Iron Oxides

Silica Sand

Shale

Aggregates in Concrete Production Gypsum Coarse Fine natural Aggregates 1 aggregates

6.75E-02 6.75E-02 6.29E-01 3.58E-02 3.58E-02 4.54E-02

2.95E-02

Manufactured Recycled sand 2 aggregates 4.54E-02

5.58E-02

4.90E-03

4.33E-03 4.33E-03 3.80E-02 2.18E-03 2.18E-03 5.02E-03

3.26E-03

5.02E-03

6.20E-03

1.32E-05 4.28E-05 2.79E-06 1.61E-02 5.241

2.54E-06 9.62E-06 1.18E-05 4.90E-03 4.307

1.34E-05 2.56E-05 5.01E-06 4.75E-05

2.07E-05 7.70E-06 3.94E-05 7.31E-05

2.54E-05 4.84E-05 9.47E-06 8.96E-04 4.370

2.54E-06 9.62E-06 1.18E-05 4.33E-03 4.307

3.60E-02 4.30E-09 1.39E-05 4.33E-03 21.713

6.85E-06 1.82E-05 1.33E-06 3.80E-02 2.407

(PE International (thinkstep) 2016)

6.85E-06 1.82E-05 1.33E-06 2.18E-03 2.407

2.07E-05 7.70E-06 3.94E-05 7.31E-05 3.642

CCAA & (PE International (thinkstep) 2016)

CCAA

1

Result based on the weighted average per total production of producers A to D in Table S1 of Supplementary material NO 2

2

Result based on the weighted average per total production of producers A to D in Table S1 of Supplementary material NO 2

3

Various sources of energy including different types of conventional, alternative fuels and renewable energy

4

Other emissions were included in calculations as provided by PE International in GaBi software program datasets for each product

5

Water includes ground water, lake water, rain water, and river water, as provided water distribution by PE International in GaBi software dataset

associated with the heating of limestone (CaCO3) to produce lime (CaO). The calcination process liberates CO2 as byproduct as shown in Eq. (1). CaCO3 þ heat→CaOþCO2

ð1Þ

The CO2 emissions from calcination depend on the quality and type of limestone used for the manufacturing process. Different studies have reported emissions to be in the range of 0.450 to 0.553 kg/ per kg of clinker (Marceau et al. 2006; Huntzinger and Eatmon 2009; Valderrama et al. 2012). The current study industry data showed that process CO2 emissions from limestone calcination were 0.534 kg/ t of clinker (0.467 kg/ t of cement at 87.5% clinker content). These results are consistent with the report from the Commonwealth of Australia Department of the Environment (Department of the Environment - Australia 2014) which showed CO2 emissions of 0.534 kg/ t clinker. Therefore the average process CO2 emission in Australia was determined to be 0.467 kg/ t of cement. The International Energy Agency (IEA) has reported that the country average thermal energy intensity for cement production ranges from 3400 to 5300 MJ/ t of cement (International Energy Agency 2007). The country average CO2 intensity of cement ranges from 0.65 to 0.92 t CO2 / tonne of cement with weighted average of 0.83 t CO2/ t (International Energy Agency 2007). In order to have a clearer picture about the emissions, the range of major emissions for production of cement, such as NOx, and SO2 were investigated from the literature (ATILH 2002; Josa et al. 2004; Sjunnesson 2005; Marceau et al. 2006; Flower and Sanjayan 2007; Josa et al. 2007; Boesch et al. 2009; Boesch and

Hellweg 2010; Chen et al. 2010b; Zabalza Bribián et al. 2011; Valderrama et al. 2012; Li et al. 2014; García-Gusano et al. 2015) and are presented in details in Table S5 of Electronic Supplementary Material NO 1. Considering all the collected information from the Australian industry and previous studies, the inventory materials and emissions inputs for modelling cement in GaBi software program were determined. 3.2 Supplementary cementitious materials Basically, supplementary cementitious materials (SCMs) are waste-products or by-products of other manufacturing processes. The primary energy and emissions associated with the use of SCMs in concrete need to be considered from three areas: (i) allocation from the upstream manufacturing process, (ii) transportation, and (iii) further preparation (drying and grinding). Section 6.4.3.3 of The European Standard EN 15804 requires clarifying the allocation method of input flows (The European Committee for Standardization (CEN) 2012). Different methods are suggested for allocating energy requirements and emissions related to the production of SCMs by previous studies (Heidrich et al. 2005; Flower and Sanjayan 2007; Chen et al. 2010a; Habert et al. 2011; Van Den Heede and De Belie 2012). Allocation can be performed by considering SCMs as either waste products or by-products. In cases where they are considered by-products, the allocation of emissions and primary energy can be performed by mass share or market value share (Crossin 2015). UN CPC 375 (2013) document has discussed the procedure for the selection of the appropriate allocation method. For any waste-product and by-product where the


The manufacturing parameters of benchmark concrete per cubic metre (GaBi balance-sheet output)

Product

N20

Unit weight (kg/m3) Energy (net calorific MJ) Modules A1-A3 Module A4

2335

2356

2373

2373

2373

2391

2410

2427

1808

1967

2090

2183

2310

2267

1456

1575

1884

2289

2613

3139

3733

3842

1402

2201

2593

2971

3356

2524

Non-renewable energy resources (MJ) Modules A1-A3 Module A4 Non-renewable (breakdown MJ) Crude oil (MJ) Coal (MJ)

N25

N32

N40

N50

S65

S80

S100

M1

M2

M3

M4

GR

RN

1395

1513

1822

2227

2551

3076

3670

3778

1354

2149

2538

2914

3295

2464

61.5 1407

62.0 1523

62.4 1824

62.4 2217

62.5 2533

62.9 3010

63.4 3551

63.9 3657

47.6 1309

51.8 2105

55.0 2495

57.4 2871

60.7 3261

59.6 2450

1347

1463

1763

2156

2472

2949

3489

3595

1263

2055

2441

2815

3202

2392

59.9

60.3

60.8

60.8

60.8

61.3

61.8

62.2

46.3

50.4

53.6

55.9

59.1

58.0

1407

1523

1824

2217

2533

3010

3551

3657

1309

2105

2495

2871

3261

2450

303

315

342

372

401

442

481

496

247

325

367

405

447

377

697

764

941

1179

1360

1670

2024

2075

669

1138

1360

1579

1807

1328

Natural gas (MJ) Uranium (MJ)

322 14

352 14

429 15

534 16

621 16

721 25

848 36

884 36

318 75

512 52

613 42

707 32

800 13

593 11

Alternative fuels (MJ) Renewable energy resources (MJ) Modules A1-A3 Module A4 CO2 (kg) Modules A1-A3 Module A4

71 49 47.5

78 52 50.6

97 60 58.6

117 71 69.6

135 80 78.1

152 129 127

163 182 180

166 185 183.3

0 94 92.7

78 96 94.7

113 98 96.8

149 100 98.4

195 95 93.8

142 74 72.2

1.60

1.62

1.63

1.63

1.63

1.65

1.66

1.67

1.25

1.35

1.44

1.50

1.59

1.49

207 203 4.23

225 221 4.26

275 270 4.30

331 326 4.29

378 374 4.30

441 437 4.33

499 494 4.36

511 507 4.39

216 212 3.27

340 337 3.56

399 395 3.75

457 453 3.95

515 511 4.11

381 377 4.1

Methane (kg) Modules A1-A3 Module A4

0.114 0.110 0.004

0.124 0.120 0.004

0.150 0.146 0.004

0.191 0.187 0.004

0.219 0.215 0.004

0.287 0.283 0.004

0.37 0.366 0.004

0.379 0.375 0.004

0.164 0.160 0.003

0.213 0.209 0.004

0.237 0.233 0.004

0.261 0.257 0.004

0.278 0.274 0.004

0.207 0.203 0.004

NOx (kg) Modules A1-A3 Module A4

0.698 0.696 0.002 0.213

0.763 0.760 0.002 0.223

0.934 0.932 0.002 0.246

1.122 1.120 0.002 0.281

1.289 1.287 0.002 0.310

1.502 1.500 0.002 0.392

1.683 1.680 0.002 0.495

1.732 1.730 0.002 0.511

0.170 0.169 0.002 0.109

0.811 0.809 0.002 0.195

1.111 1.110 0.002 0.241

1.407 1.405 0.002 0.284

1.776 1.774 0.002 0.334

1.312 1.310 0.002 0.271

0.211 0.001

0.221 0.002

0.244 0.002

0.279 0.002

0.308 0.002

0.390 0.002

0.493 0.002

0.509 0.002

0.107 0.002

0.194 0.002

0.240 0.002

0.282 0.002

0.332 0.002

0.269 0.002

0.335

0.362

0.432

0.546

0.618

0.691

0.817

0.835

0.092

0.362

0.488

0.612

0.769

0.577

0.328 0.007 0.436 0.4357 0.0005 13.70 13.6 0.112

0.354 0.007 0.458 0.4578 0.0005 14.24 14.1 0.113

0.425 0.007 0.519 0.518 0.005 15.62 15.5 0.113

0.538 0.007 0.576 0.575 0.005 17.23 17.10 0.113

0.611 0.007 0.629 0.628 0.0005 18.59 18.50 0.114

0.684 0.007 0.734 0.733 0.005 44.81 44.70 0.114

0.810 0.007 0.827 0.826 0.005 71.17 71.11 0.115

0.827 0.007 0.838 0.837 0.005 71.70 71.6 0.116

0.086 0.005 0.148 0.147 0.001 52.49 52.4 0.086

0.356 0.006 0.398 0.397 0.004 41.39 41.3 0.094

0.481 0.007 0.513 0.513 0.005 36.69 36.6 0.101

0.605 0.007 0.628 0.627 0.005 31.85 31.74 0.104

0.762 0.007 0.778 0.777 0.005 21.86 21.74 0.111

0.570 0.007 0.611 0.610 0.005 18.10 18.0 0.108

209 205 4.4 0.670 0.651 0.019 0.108 0.103 0.004 5.706 5.704

228 224 4.4 0.719 0.700 0.019 0.117 0.113 0.005 6.203 6.201

278 274 4.5 0.845 0.826 0.019 0.143 0.138 0.005 7.563 7.560

335 331 4.5 0.993 0.974 0.019 0.17 0.165 0.003 26.646 26.646

383 379 4.5 1.124 1.104 0.019 0.195 0.190 0.005 30.019 30.018

448 444 4.5 1.34 1.321 0.019 0.226 0.221 0.005 26.421 26.420

508 504 4.6 1.563 1.543 0.020 0.251 0.247 0.005 52.30 5.229

521 517 4.6 1.609 1.59 0.02 0.259 0.254 0.005 52.501 52.500

219 216 3.4 0.245 0.230 0.015 0.33 0.029 0.003 2.201 2.189

345 341 3.7 0.713 0.713 0.697 0.126 0.122 0.004 6.845 6.843

404 401 4.0 0.939 0.922 0.017 0.169 0.165 0.004 8.970 8.968

463 459 4.2 1.158 1.14 0.018 0.212 0.208 0.004 11.09 11.09

522 518 4.4 1.429 1.41 0.019 0.226 0.261 0.004 13.69 13.69

386 382 4.3 1.087 1.069 0.018 0.197 0.193 0.004 10.02 10.02

SO2 (kg) Modules A1-A3 Module A4 CO (kg) Modules A1-A3 Module A4 Dust PM ≤10 (kg) Modules A1-A3 Module A4 Water (m3) Modules A1-A3 Module A4 GWP (kg CO2eq) Modules A1-A3 Module A4 AP (kg SO2eq) Modules A1-A3 Module A4 EP (kg PO4eq) Modules A1-A3 Module A4 ODP (kg CFC-11 eq) × 10−9 Modules A1-A3

Int J Life Cycle Assess Table 7 (continued) Product

N20

N25

N32

N40

N50

S65

S80

S100

M1

M2

M3

M4

GR

RN

Module A4 ADP (kg Sb eq) × 10−3 Modules A1-A3 Module A4

0.002 7.932 7.931

0.002 0.872 0.872

0.002 1.090 1.090

0.001 1.308 1.308

0.001 1.506 1.506

0.001 1.705 1.705

0.001 1.825 1.825

0.001 1.865 1.865

0.002 0.008 0.008

0.002 0.877 0.876

0.002 1.271 1.270

0.001 1.666 1.666

0.001 2.17 2.17

0.001 1.585 1.585

0.001

0.001

0.000

0.000

0.000

0.000

0.000

0.000

0.000

0.001

0.001

0.001

0.001

0.001

ADP fossil (MJ eq) Modules A1-A3 Module A4

1322 1262

1431 1370

1712 1651

2085 2027

2382 2321

2832 2771

3352 3290

3455 3392

1233 1187

1975 1924

2339 2286

2691 2635

3053 2995

2297 2239

59.8 0.031

60.3 0.034

60.8 0.042

60.75 0.052

60.81 0.06

61.2 0.075

61.73 0.093

62.16 0.096

46.3 0.007

50.3 0.036

53.3 0.05

55.9 0.064

59.1 0.08

58.0 0.59

POCP (kg Ethane eq) Modules A1-A3 Module A4 1

0.038 0.041 0.049 0.059 0.067 0.083 0.101 0.103 0.013 0.042 0.056 0.070 0.087 0.066 -0.007 -0.007 -0.007 -0.007 -0.007 -0.007 -0.007 -0.007 -0.006 -0.006 -0.006 -0.006 -0.007 -0.007

1

The reason for the negative PCOP impact of module A4 (transportation) is that GaBi splits NOx emissions of truck transport to NO and NO2. According to CML a negative characterisation factor of −2.3 is associated with NO emissions

concrete producer is only paying for transport, no allocation of its production process is necessary. In such cases, impacts from transport and further material preparation (drying and grinding) at cement or concrete plants need to be allocated to the concrete production. However, for situations like production of concrete in Australia, where the concrete producer is paying for the raw materials used as SCMs, the allocation by mass share or market value should be considered. Table S8 of Electronic Supplementary Material NO 1 presents the results of different allocation systems for different SCMs. This includes no allocation, allocation by mass and allocation by market value. This study has followed the recommended procedure, suggested by EPD product category rules (PCR) for supplementary cementitious materials used in concrete, by applying the allocation by market values for all SCMs used in concrete. The allocation of ground granulated blast-furnace slag (GGBFS) has been carried out by market value of 5.1% from the pig-iron production process. Data from the concrete industry regarding materials transportation and preparation have been collected. The additional transportation, grinding and drying procedure have also been considered for GGBFS, before it can be used in concrete products (see Electronic Supplementary Material NO 1). Fly ash is a by-product from coal fired electricity production and is sold to concrete producers. Fly ash allocation has been performed at 1.6% of market value of the electricity production process. Concrete producers have reported that, except for transportation, no additional activity and preparation process is associated with fly ash (see Electronic Supplementary Material NO 1). The allocation for amorphous silica has been considered by economic value of 16% from ferrosilicon production. Additional transportation has also been considered for amorphous silica as discussed in Electronic Supplementary Material NO 1.

3.3 Building lime Building lime is currently incorporated in the production of standard mortar. The lime industry operates 18 facilities across all the states of Australia, largely in regional areas. The Commonwealth of Australia (Depa rtment of the Environment) provided a reference base number of 0.675 t CO2eq emissions per tonne of commercial building lime production (Department of the Environment - Australia 2014). An additional 5% for CO2 emissions was added to this figure due to the by-production of unwanted lime kiln dust. The calcination factor for lime kiln dust was considered as recommended by Department of the Environment of Australia (Department of the Environment - Australia 2014). The total 0.709 t CO2eq per tonne of building lime, including process and non-process emissions, was added to the emissions from quarrying process of limestone (AU: Limestone CCAA) for the production of building lime. Other main emissions regarding lime production were extracted from the production process of building lime in the GaBi software program. Other main emissions were considered as follows: Sulphur dioxide 9.64E-05 kg/kg, Nitrogen oxides 3.12E-04 kg/kg, Carbon monoxide (CO) 1.09E-04 kg/kg of building lime. On average the process of burning the limestone undergoes a loss of approximately 44% in weight to produce building lime. Therefore, it was assumed that 1.44 kg of limestone is required for the production of 1 kg of building lime. In addition, it was demined that 4.01–4.20 MJ primary energy is required for the production of each kilogramme lime (Carmeuse Lime & Stone 2015; PE International (thinkstep) 2016). 3.4 Aggregates In this study the primary energy requirements and main emissions were determined based on the collected data from major

Int J Life Cycle Assess Fig. 2 The modular breakdown of the environmental impacts of concrete, mortar, grout and render products

Module A1 Module A3

Module A2 Module A4

N20-(GWP) N20-(AP) N20-(EP) N20-(ODP) N20-(ADP e) N20-(ADP f)

100-(GWP) S100-(AP) S100-(EP) S100-(ODP) 00-(ADP e) 100-(ADP f)


M2-(GWP) M2-(AP) M2-(EP) M2-(ODP) M2-(ADP e) M2-(ADP f)


M3-(GWP) M3-(AP) M3-(EP) M3-(EP) M3-(EP) M3-(EP) M4-(GWP) M4-(AP) M4-(EP) M4-(EP) M4-(EP) M4-(EP)

N40 -(GWP) N40 -(AP) N40 -(EP) N40 -(EP) N40 -(EP) N40 -(EP)

GR-(GWP) GR-(AP) GR-(EP) GR-(EP) GR-(EP) GR-(EP)

N50-(GWP) N50-(AP) N50-(EP) N50-(EP) N50-(EP) N50-(EP)

RN-(GWP) RN-(AP) RN-(EP) RN-(EP) RN-(EP) RN-(EP)

S65-(GWP) S65-(AP) S65-(EP) S65-(EP) S65-(EP) S65-(EP)

80%

S80-(GWP) S80-(AP) S80-(EP) S80-(EP) S80-(EP) S80-(EP) 80%

aggregate production facilities with the capacity of 78 million tonne of aggregates per year as shown in details in Table S1 of Electronic Supplementary Material NO 2. Due to the confidentially of data collected from the Australian quarry industry, the data presented in Table S1 of Electronic Supplementary Material NO 2 has been normalised per kilogrammes of aggregate production per different aggregate producers, without Fig. 3 Global Scale: Global warming potential (kg CO2eq) per cubic metre of products (Modules A1-A3)

85%

90%

95%

100%

M1-(GWP) M1-(AP) M1-(EP) M1-(ODP) M1-(ADP e) M1-(ADP f)

85%

90%

95%

100%

40%

60%

80%

100%

labelling actual production volumes and quarry names. Data shows that the CO2eq emissions for the production of fine and coarse aggregates were 3.26E-03 and 5.02E-03 t CO2eq/ t aggregate, respectively. The emissions data in the current study is lower than the previously reported emissions by Flower and Sanjayan (2007) from only two quarries in Australia. In addition, as discussed before, the determined emissions in the

Int J Life Cycle Assess Fig. 4 Regional Scale: Acidification (kg SO2eq) per cubic metre of products (Modules A1-A3)

current study were confirmed by a number of other studies. Marinkovic et al. (2010) reported the manufacturing of recycled aggregates resulted in slightly (almost 20%) higher energy demand and emissions (Marinković et al. 2010). The recycled aggregates process is defined (AU: Recycled aggregates CCAA) based on data presented in Table 6. The production processes of fine and coarse aggregate were defined based on the available data from the industry. However, the main emissions reported for the production of aggregates did not include all ranges of emissions associated with the quarrying and production of aggregates. In order to prepare a robust model in GaBi software program, the unreported data were compiled from the existing GaBi process objects for the production process of fine aggregates (EU-27 Sand 0/2 PE) and coarse aggregates (EU-27 Gravel 2/32 PE). The major emissions to air (CO, SO2, NOx and CO2eq) and primary energy usage were selected based on the Australian data presented in Table S1 of Electronic Supplementary Material NO 2, whereas, other unreported emissions and inventory inputs materials were selected from the pre-defined GaBi processes for fine and coarse aggregates. Accordingly, four new process objects were defined as follows: Manufactured sand (AU: Manufactured sand CCAA), Fine natural aggregates (AU: Fine natural aggregates CCAA), Coarse aggregates (AU Coarse aggregate CCAA), and Recycled aggregates (AU: Recycled aggregates CCAA). The main emissions and primary energy relating to the production process of aggregates including raw materials are listed in Table 6. Further details regarding the aggregates manufacturing and quarrying are provided in Electronic Supplementary Material NO 2. 3.5 Water Water in the production of concrete consists of the primary water from the production of raw materials (extraction and processing) plus the volume of water directly added to the Fig. 5 Regional Scale: Eutrophication (kg PO4eq) per cubic metre of products (Modules A1-A3)

concrete mix. Water is also consumed through other activities, such as washing truck mixers at cement plants. The directly added water is named mix-water and varies based on different concrete mix designs. Mix waters for different types of benchmark cementitious materials are shown in Table 2 In the current study, the primary water used for production of aggregates and cement was included in their production process and no additional water was required to be added to the concrete production due to aggregate or cement. Therefore, the process water for production of concrete consists of mix water, spray and cleaning water, and evaporated water. All water used in premixed concrete is required to meet the relevant provisions of AS 1379. Water consumption at concrete plants varies from plant to plant with monthly production volumes and plant design being major factors. Mix-water for different types of benchmark cementitious materials is shown in Table 2. The required water for truck washing off, truck washing out, and other miscellaneous activities was in the range of 35 to 515 kg per cubic metre of concrete (Nisbet et al. 2002). The current study industry data showed that in most readymix concrete plants water is recycled to concrete as constituent. However, there is some water consumption due to evaporation. According to the industry data, the total sourced water usage per m3 is typically town water (ground water). From the water consumed in a concrete plant, 45.4% was directly added to concrete and delivered off site as a concrete constituent. 54.6% was used on plant site for aggregate sprays and washdown and was recycled into concrete or evaporated. The further breakdown of the water used in sprays and wash-down as above is 13.6% added to and contained in aggregates and therefore delivered off site in concrete. 18.2% is recycled water used as concrete constituent and delivered off site in concrete and 22.7% was evaporated. Considering the average 170 L (77.3%) of water as concrete mix constituent (see Table 2), an additional 49.9 (22.7%) litres of water per cubic metre of concrete was determined to be consumed due to the

Int J Life Cycle Assess Fig. 6 Regional Scale: Ozone Layer Depletion (kg CFC-11 eq) per cubic metre of products (Modules A1-A3)

evaporation in concrete plant in addition to the mix water. Electronic Supplementary Material NO 3 provides a more extended discussion on water requirement of concrete production. 3.6 Other items (admixtures, concrete batching and transportation) Several studies report that chemical admixtures used in concrete production have negligible environmental impacts (Flower and Sanjayan 2007; Habert et al. 2011). In this study similar emissions and thermal and secondary energy requirements reported by Sjunnesson (2005) were accounted for per kg of admixtures used. Additional primary emissions of electricity and fuel production in Australia were calculated by GaBi software program and were added to the figure above. The cradle-to-gate emissions for admixture were determined to be 1.61 kg CO2eq, 1.13E-02 kg SO2, 9.04E-03 kg NOx, and 2.51E-03 CO per kg of admixture. The emissions and primary energy requirements for the mixing of concrete were determined based on data from major concrete producers. Results are similar to that of previous studies. Investigating production data for over 50 million cubic metres of concrete showed 2.679 l fuel/ m3, 2.76 kWh/ m3, and 0.186 MJ natural gas/ m3 of concrete batching in concrete plant. Moreover, major emissions, kg per cubic metre of concrete, were determined to be as follows: CO2eq 7.456 (11.2 indirect and electricity included), NOx 0.0369, SO2 0.0338, CO 0.0256 and Dust 10 μm 0.0742. Module A4 of Standard EN 15804 (The European Committee for Standardization (CEN) 2012) includes

Table 8

transportation of construction product to the construction site. It is stated by Australian Standard AS 1379 that plastic concrete shall be transported in a manner that will prevent segregation, loss of material or premature stiffening. The average transportation time was determined 30 min, equal to an average transport distance of 40 km from ready-mix batching plant to construction site. Electronic Supplementary Material NO 3 provides a more extended discussion on the inventory data of other factors such as admixtures and concrete batching.

4 Results and discussion The results of the cradle-to-grave LCA analysis are tabulated in Table 7. The LCA analysis includes modules A1 to A4 of EN 15804 for the production process of different benchmark products. In all cases, module A1 was responsible for 85–95% of different environmental impacts associated with manufacturing benchmark products (Fig. 2). Josa et al. (2007) discussed the effect of different impact categories such as greenhouse gases, acidification, ozone depletion based on the fundamental emission parameters. As an example, it was shown that greenhouse warming, resulted from CO2, has a global effect, whilst acidification and eutrophication are classified as regional categories, which are mostly affected by SO2 and NOx emissions, and only impact regions where products are manufactured (Huang et al. 2009). LCIA analysis is used to determine the different impacts of emissions on a global and regional scale based on CML 2001 classifications and in conjunction with the requirement of EN 15804 Section 6.5. At a global scale, the most important class

The normalised environmental impacts based on CML2001 - Apr. 2013 (global equivalents)

Impact categories (modules A1-A3)

N20

N25

N32

N40

N50

S65

S80

S100

M1

M2

M3

M4

GR

RN

GWP (kg CO2eq) × 10−12 AP (kg SO2eq) × 10−12 EP (kg PO4eq) × 10−12 ODP (kg CFC-11 eq) × 10−17 ADP (kg Sb eq) × 10−12 ADP fossil (MJ eq) × 10−12 PCOP (kg Ethane eq) × 10−12

5.01 2.80 0.68 2.52 3.79 3.48 0.85

5.46 3.01 0.74 2.74 4.17 3.76 0.93

6.65 3.53 0.90 3.34 5.22 4.50 1.14

8.02 4.15 1.07 11.68 6.26 5.48 1.41

9.17 4.70 1.23 13.32 7.20 6.26 1.63

12.16 6.54 1.59 23.07 8.73 8.82 2.54

10.72 5.61 1.42 11.66 8.16 7.45 2.05

12.46 6.73 1.63 23.17 8.92 9.09 2.60

5.26 1.03 0.21 0.97 0.04 3.25 0.19

8.26 2.98 0.79 3.02 4.19 5.20 0.99

9.68 3.93 1.07 3.96 6.08 6.15 1.36

11.07 4.84 1.34 4.89 7.97 7.08 1.73

12.48 5.97 1.68 6.04 10.42 8.03 2.19

9.23 4.55 1.25 4.42 7.58 6.04 1.61

Int J Life Cycle Assess Fig. 7 Normalised-weighted data based on CML 2013 (thinkstep LCIA Survey 2012 Global, factors)

is global warming potential, presenting by kg CO2eq. The global warming indicator for different grades of concrete, mortar, render and grout are demonstrated in Fig. 3. As can be seen the determined global warming potential had a positive correlation with concrete strength. A higher CO2 emission was driven from the fact that a higher strength is commonly achieved by higher cement content in a mix design, which leads to a higher Global Warming Potential (GWP) for higher strength grade products. Due to the confidentiality of data the effect of different concrete constituents on the final emissions cannot be demonstrated in terms of percentage per constituent, however, the analysis of data showed that for normal grade concretes Global Warming Potential (with the order) was due to cement, batching, SCMs (if used), aggregates, admixtures (if used) and transportation. For special grade concretes the Global Warming Potential (with the order) was due to cement, SCMs, batching, aggregates, admixtures and transportation. In addition, for standard mortar grades Global Warming Potential is mostly due to the use of cement (if used), building lime, batching, aggregates and transportation. Acidification (Fig. 4), Eutrophication (Fig. 5) and Ozone Layer Depletion (Fig. 6) properties of different concrete products were also determined. As can be seen from the data presented, the local and regional environmental impacts of concrete grades were increased by the increase in strength of the benchmark products. The analysis of data showed that the acidification (kg SO2eq) impact for normal grade concretes

was due to the use of cement, batching, aggregates, SCMs (if used), admixtures (if used), and transportation. Special grade concrete impacts were due to the use of cement, SCMs (if used), batching, aggregates, admixtures (if used), and transportation. The Eutrophication (EP) impact for both normal and special grade concretes was due to the use of cement, SCMs (if used), batching, aggregates, admixtures (if used), and transportation. Moreover, for standard mortar grades acidification and eutrophication were due to the use of cement (if used), building lime, batching, aggregates and transportation. The Ozone Layer Depletion (ODP) analysis showed that for both normal and special grade concretes SCMs (if used), cement, and aggregates had the highest impact on the total ODP. Moreover, for standard mortar grades ODP was due to the use of cement, building lime, and aggregates. The determined environmental impacts of each product were normalised and then weighted using GaBi software program. The normalisation factors selected from CML2001 Apr. 2013, (World, year 2000 - global equivalents) and the normalised impacts for modules A1 to A3 for each cubic metre of concrete products are shown in Table 8. In order to provide a better understanding of the effect of different environmental impacts on the final products, the weighting factors from CML 2013, thinkstep LCIA Survey 2012 (global equivalents weighted) were used and the normalised environmental impacts were weighted and shown in Fig. 7. As can been seen, global warming, abiotic depletions, acidification and

Fig. 8 Sensitivity of the Global warming potential impact to the variation of cement, SCMs, aggregates and transportation distance (a) Normal grade 32 MPa, and (b) Special grade 80 MPa


Fig. 9 Sensitivity of the Acidification impact to the variation of cement, SCMs, aggregates and transportation distance (a) Normal grade 32 MPa, and (b) Special grade 80 MPa

eutrophication are the main impact categories associated with each concrete products.

5 Data quality, limitations, variation of results and sensitivity analysis In broad terms, concrete is manufactured from combining three main primary elements: (i) cement, (ii) supplementary cementitious materials, and (iii) aggregates. Each of these elements is manufactured in a separate process and is transported to batching plants. The uncertainty associated with the LCA results of each benchmark concrete product comes from the variation in three major areas (i) variation of impact associated with manufacturing of primary elements, (ii) variation in determination of the appropriate proportion of each primary element in mix designs, and (iii) variation in the transportation distances. Cement data are reproducible as they are modelled in GaBi software program. The variation (uncertainty of the information) associated with cement manufacturing is estimated to be in the range of ±5%, mostly due to the fact that cement manufacturing technology is quite well established and the variation is only associated with collecting and reporting data. Data for the manufacture of aggregates has been collected in year 2014 from major aggregate suppliers across Australia.

The collected data represents over 90% of actual aggregate supply in Australia (see Table S1 of Electronic Supplementary Materials NO 2). Data has also been cross checked with other published data from literature, datasets from GaBi software and previous set of data collected in year 2008 from the industry. The comparison of data with data from year 2008 shows no major alteration in the structure of aggregates quarrying process. Aggregates datasets are reproducible as they are modelled in GaBi software program. The variation (uncertainty of the information) associated with quarrying of aggregates is estimated to be in the range of ±20%, mostly due to the variation in mineralogy, hardness, and size of final aggregate product. The allocation of materials, primary energy and emissions of supplementary cementitious materials (fly ash, GGBFS and amorphous silica) has been discussed thoroughly in Section 3.2 and Electronic Supplementary Materials NO 1. Supplementary cementitious materials (SCMs) data are collected in year 2015 and represent over 90% of actual SCMs supply in the market; however, it varies significantly across the various markets in Australia. The variation associated with SCM is estimated to be in the range of ±30%, mostly due to the variation in market price. The combined variations in impacts of benchmark products due to uncertainty of manufacturing process of major primary

Fig. 10 Sensitivity of the Eutrophication impact to the variation of cement, SCMs, aggregates and transportation distance (a) Normal grade 32 MPa, and (b) Special grade 80 MPa


Fig. 11 Sensitivity of the Ozone layer depletion impact to the variation of cement, SCMs, aggregates and transportation distance (a) Normal grade 32 MPa, and (b) Special grade 80 MPa

elements (cement, aggregates, and supplementary cementitious materials) have been indicated on Figs. 3, 4, 5, 6. Therefore, it is expected the emissions associated with each benchmark product remain in the variation range provided in Figs. 3, 4, 5, 6 for products in different regions of Australia. It should be taken into account that considering the provided variation ranges in Figs. 3, 4, 5, 6 is not enough when products have different mix designs. When products have a different mix design, the discussed method in Eq. (2) should be followed to adjust the associated environmental impacts with each product. Sensitivity of the associated environmental impacts to the alteration of mix-design, including the change of cement, SCMs, and aggregates in the mix proportion, as well as the variation of transport distances for normal grade and special grade benchmark concrete products were investigated. The sensitivity analysis has been carried out by the change of each variable in the range of ±40%. The associated environmental impacts were compared to the environmental impacts of base benchmark products Figs. 8, 9, 10, 11. The main limitations of this research, in terms of quality of input data, were related to the determination of market values for SCMs and transportation distances. This is mostly due to the fact that the products have been defined for a large geography while the market price of SCMs can significantly vary across Australia. In order to address this matter, the combined variation of raw materials, including the variation of supplementary cementitious materials have been indicated on Figs. 3, 4, 5, 6 . As can be seen Ozone Layer Depletion (ODP) had the larger variation due to the variation of SCMs data. This is more Table 9 The correction factors used in eq. (2) for estimating environmental impacts Correction factors

Energy

GWP

AP

EP

ODP

α β γ

0.030 0.020 3.000

0.030 0.200 3.000

0.003 0.200 3.000

0.030 0.020 2.000

0.003 17.000 0.300

influential in particular for the higher strength grades with a relatively higher SCMS content. Moreover, the sensitivity analysis (see Figs. 8, 9, 10, 11) showed that results are not sensitive to the change of transportation distances in the range of ±40%. Therefore, it is recommended that in future studies, SCMs including fly ash, GGBFS, and silica fume, should be investigated locally using state-based datasets to narrow down the range of variation in the results. Results of the sensitivity analysis showed the change of transport distances and content of aggregates did not have a major influence on the associated environmental impacts of the benchmark products. However, the associated environmental impacts had a strong correlation mainly with clinker content in the mix-design of each benchmark product. It can be inferred that although replacement of a portion of concrete aggregates with waste or recycled materials such as recycled concrete, recycled glass (Maier and Durham 2012) or recycled tyre rubber (Mohammadi et al. 2014; Mohammadi and Khabbaz 2015; Mohammadi et al. 2015; Mohammadi et al. 2016) are applicable methods to provide landfill avoidance and decrease the depletion of virgin raw materials. The best strategy to manage emissions associated with the production of concrete is to use less clinker per unit mass of the concrete binder. However, at the same time the quality of the material and its applicability has to be kept in mind. The outcome of this study revealed that in all cases cement and supplementary cementitious materials SCMs had the highest contribution to the emissions of concrete products. Using less cement in concrete products either by substitution of it with SCMs or manufacturing cement with increased mineral additions such as higher limestone content (Mohammadi and South 2015; Mohammadi and South 2016a; Mohammadi and South 2016b; Mohammadi and South 2016c; Mohammadi and South 2016d) could effectively reduce concrete emissions. Moreover, on the basis of this fact, a simple but significantly practical, method to approximate global and regional impacts of other customised types of concrete can be inferred.


(a) Energy

(b) Global warming potential

(c) Acidification

(d) Eutrophication

(e) Ozone Layer Depletion

Fig. 12 The estimated environmental impacts of customised mix designs using the formulation compared with the actual results from GaBi software program (a) Energy MJ, (b) GWP kg CO2eq, (c) AP kg SO2eq, (d) EP kg PO4eq, and (e) ODP 10–9 × kg CFC-11 eq

On construction cases where specific concrete mix-design is prescribed which differs from the tabulated reference mixdesigns in Table 2, the following steps should be taken: (a) strength grade of customised (project) concrete should be decided. If the strength grade is not available, the appropriate strength grade can be decided based on the provided concrete applications as shown in Table 3, (b) The appropriate cement, fly ash, GGBFS and silica fume content for the equivalent benchmark strength grade should be decided from Table 2. (c) Once the equivalent cement, fly ash, GGBFS and silica fume content are determined, the approximate global (Global Warming Potential) or regional (Acidification, Eutrophication

and Ozone Layer Depletion) impacts of the customised mixdesign concrete can be approximated by multiplying the adjustment factor (IC) to the provided impacts of the benchmark products using the formulation provided in Eq. (2): EI c ¼ I c EI b ¼

ð100−G−MAÞ C c þ α F c β S c þ γ SF c 87:5 C b þ α F b þ β S b þ γ SF b EI b ð2Þ


where, EIc is the estimated global or regional environmental impact of customised concrete, IC is the global or regional impact adjustment factor for customised concrete, EIb is the environmental impact of benchmark concrete, G is the gypsum content of cement for a customised mix, MA is the minerals addition content of cement for a customised mix, Cc, Fc, Sc and SFc are cement, fly ash, GGBFS and silica fume contents of a customised mixdesign, Cb, Fb, Sb and SFb are cement, fly ash, GGBFS and silica fume contents for equivalent benchmark strength grade, provided in Table 2 and α, β, and γ are correction factors read for different environmental impacts from Table 9. The application of the provided method aids LCA studies of concrete constructions in Australia and significantly reduces the required efforts for performing LCA calculations of customised mix-design concretes. An additional simplified method for calculating the associated environmental impacts of customised products has also been provided and discussed in Electronic Supplementary Material NO 4. The simplified formulation only considers the cement content of products with customised mix proportions. However, it has a higher level of error in approximating the environmental impacts because the simplified method does not consider the adjustment for the use of different SCMs. Fig S1 of Supplementary Material NO 4 shows the errors associated with the application of simplified methods for different grades of customised mixes. As an example, a range of customised commercial mix designs for different applications was acquired from the concrete industry (see Tables S1 and S2 from Electronic Supplementary Material NO 4). The actual emissions were calculated using the GaBi software program and were compared with emissions estimated using the method introduced by Eq. (2). The results of using the introduced method for the calculation of primary energy, Global Warming Potential (GWP), Acidification potential (AP), Eutrophication potential (EP), and Ozone Layer Depletion (ODP) per cubic metre of customised concrete are presented in Fig. 12. As can be seen from Fig. 12, using the method provided by Eq. (2) can be appropriately used for the estimation of emissions associated with concrete products produced with customised mix-designs. The average errors associated with using the introduced method for the calculation of the environmental impact of the customised mix designs have been determined as follows: 2.9% for the primary energy, 2.4% for Global Warming Potential (GWP), 2.6% for Acidification Potential (AP), 1.9% for Eutrophication Potential (EP) and 1.9% for Ozone Layer Depletion (ODP). The similar expected variation of the environmental impact, as shown in Figs. 3, 4, 5, 6 should also be added to the values calculated by the formulation.

6 Conclusions This study has comprehensively reviewed the environmental performance of different benchmark concretes in Australia. The environmental datasets provided by this study can help the construction industry to compare the environmental credentials of different construction materials with concrete products to select more eco-friendly options. The LCA catalogues for different concrete benchmark products were defined and the environmental impacts of each grade have been investigated. It was found that the kg CO2eq emissions per cubic metre of concrete products were in the range of 209 to 521, for mortar it was in the range of 219 to 463 and for grout and render were 522 and 386, respectively. Other environmental impacts, such as acidification and eutrophication, were also determined for different products. It was found that acidification was in the range of 0.670 to 1.609 kg SO2-Eq, and eutrophication was in the range of 0.108 to 0.259 kg Phosphate-Eq per cubic metre of concrete products. The outcome of this study revealed that in all cases cement had the highest contribution to the emissions of concrete products. Using less cement in concrete products either by substitution of it with supplementary cementitious products SCMs or manufacturing cement with increased mineral additions could effectively reduce concrete emissions. In addition, a practical method for approximating environmental impact of other concretes with customised mix-designs was provided.

Compliance with ethical standards Disclaimer and statement of application This article has been prepared for the purpose of providing a harmonised framework for determining the Life Cycle Assessment (LCA) for concrete products. The products assessed represent general commercial applications used in market, but should not be taken to represent a specific product. The data used to inform the LCA is based on aggregated information that is not specific to any industry product, brand, or company. For this reason, LCA results contained in this article should only be interpreted as informative data. These informative LCA results should only be compared against other research that has the same boundary of assumptions for calculating LCAs and should not be used for other purposes such as advertising, marketing or legislating against or in favour of any specific products.

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