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RESEARCH REPORT VTT-R-00068-15

Life Cycle assessment (LCA) and costing analysis (LCCA) for conventional and permeable pavement walkways Authors: Sirje Vares & Sakari Pulakka

Confidentiality: Public

RESEARCH REPORT VTT-R-00068-15 2 (24)

Preface

This report gives a short overview about the life cycle assessment of conventional and permeable pavement structures and especially from the viewpoint of carbon footprint and life cycle costing in the Finnish CLASS -project (Climate Adaptive Surfaces, 2012-14). This project develops surfacing materials and pavement structures to mitigate impacts of climate change in urban environments. The new materials are surfacing layers of porous concrete, porous asphalt and interlocking modular paving stones together with subbase structures of aggregate, pipes, geotextiles and water storage tanks and other systems. The CLASS-project is funded by TEKES (Finnish Funding Agency for Technology and Innovation) together with Finnish cities, companies and organizations including VTT Participants of the steering group in CLASS-project are:

Pirjo Sirén (chairperson), Espoon kaupunki, tekninen keskus Eeva-Riikka Bossmann, FCG Suunnittelu ja tekniikka Oy Osmo Torvinen, Helsingin kaupunki, Rakennusvirasto Tommi Fred, Helsingin seudun ympäristöpalvelut – kuntayhtymä (HSY) Olli Böök, Kaitos Oy Pekka Jauhiainen, Kiviteollisuusliitto ry Lars Forstén, Lemminkäinen Infra Oy Tapio Siikaluoma, Oulun kaupunki Mika Ervasti, Pipelife Finland Oy Tomi Tahvonen, Puutarha Tahvoset Oy Juha Forsman, Ramboll Finland Oy Tiina Suonio, RTT Betoniteollisuus Kimmo Puolakka, Rudus Oy Ab Kati Alakoski, Saint Gobain Weber Oy Ab Marika Orava, Vantaan kaupunki Angelica Roschier, TEKES Eila Lehmus, VTT

Espoo, 9.1.2015 Sirje Vares & Sakari Pulakka


Contents

Preface ................................................................................................................................... 2

Contents ................................................................................................................................. 3

1. Introduction ....................................................................................................................... 4

1.1 Pavements................................................................................................................ 4 1.2 Life cycle assessment ............................................................................................... 4 1.3 Life cycle costing analysis ......................................................................................... 7

2. Goal and scope ................................................................................................................. 9

3. System boundaries ........................................................................................................... 9

4. Structures for conventional and permeable pavements ................................................... 11

4.1 Conventional pavements ........................................................................................ 11 4.2 Permeable pavements ............................................................................................ 12 4.3 Life cycle data for main raw materials ..................................................................... 14

4.3.1 Asphalt ........................................................................................................ 14 4.3.2 Concrete ..................................................................................................... 16 4.3.3 Gravel ......................................................................................................... 16 4.3.4 Infiltration systems with polyethylene pipes and manholes .......................... 17

5. Results ............................................................................................................................ 17

5.1 Carbon footprint ...................................................................................................... 17 5.2 Life cycle costing analysis ....................................................................................... 20

6. Conclusions .................................................................................................................... 22

References ........................................................................................................................... 24


1. Introduction

1.1 Pavements

Lately the square meters covered by non-permeable, conventional, pavement types are expected to be increased, especially in urban areas. In case of severe weather and heavy rain this type of concrete and asphalt pavements have a problem with the increased stormwater loads which are not penetrated naturally into the ground but burden on drains and surface waterways. Increased amount of stormwater causes overloads to the stormwater network, damages to the pavement structures and nature.

Permeable pavements are a solution for natural stormwater infiltration. The functionality of permeable pavements is simple. Permeable pavement surface allows the rainwater to infiltrate into the structures when the impermeable structure redirects stormwater into the urban water collection system. When the pipe systems’ flow-rate capacity is insufficient, the water stays on the impermeable surfaces and causes undesired floods but also in a long run disrupt the pavement structure itself.

According to literature, Belgium is one example of having good experience and implementation of new types of permeable pavements. Since the year 2003 more than 1 million square meters of permeable pavements have been built in Belgium (Holt et al. 2014).

VTT’s CLASS project (Climate Adaptive Surfaces) studies the permeable pavement structures, applicable for Finnish climate conditions. Structural permeable pavements are functioning best in light traffic pavements, walkways and parking lots. Many different structures could be implemented for fully or partly permeable applications. Differences always exist regarding the best performance structures depending on the environmental conditions and specific locations.

Structures are designed to fulfil certain technical performance requirements, but might cause less or more environmental costs and –impacts. Unfortunately, the selection of alternative pavement structures is often only based on the initial structural cost, without regard for life cycle cost and environmental impacts because these have not been assessed. This report intends to shed information on the whole lifetime consideration for the pervious systems.

This report gives an overview about the life cycle assessment for conventional and permeable pavement structures and especially in the viewpoint of carbon footprint and life cycle costing.

1.2 Life cycle assessment

Life cycle assessment (LCA) addresses the environmental aspects and potential environmental impacts (e.g. use of energy and other resources and environmental consequences of releases) throughout a product's life cycle, from raw material acquisition through production, use, end-of-life treatment, recycling and final disposal (i.e. cradle-to-grave). Life cycle stages are introduced in Figure 1 for building materials and buildings but in general level the same stages are valid also for the assessment of infra structures such as pavements.


Figure 1. Stages of the LCA and Environmental Product declarations (EN 15804).

The general principles on life cycle assessment of products and services have been agreed upon and introduced with the help of standardisation (ISO 14040 & ISO 14044). In addition, there are international standards available on the formats, contents and processes of environmental assessment and declarations of products (ISO 14020 & ISO 14025). LCA assesses the environmental aspects and potential impacts by:

• compiling an inventory of relevant inputs and outputs of a product system; • evaluating the potential environmental impacts associated with those inputs and

outputs; • interpreting the results of the inventory analysis and impact assessment phases in

relation to the objectives of the study. Table 1 show the environmental impact categories which are used in LCA. Impact categories are always expressed by the impact parameter and equivalent emission. For example, global warming potential (GWP) assessment is limited to emissions that have an effect on climate change and thus greenhouse effect. GWP is assessed as CO2 equivalent (CO2e) and calculated as a sum of all greenhouse gases by using the mass of a greenhouse gas multiplied by its global warming potential. The main greenhouse gases, for global warming calculations, and their potentials are given in Table 2. In addition to global warming, also the term Carbon footprint (CF) is known. CF is a net amount of greenhouse gas emissions and greenhouse gas removals, expressed in CO2 equivalents.


Table 1. Impact categories of LCA.


Table 2. Greenhouse gases and their potential factors within global warming calculations (GWP 100) (IPCC 2007).

Species Chemical formula Potential for GWP 100 Carbon dioxide CO2 1 Methane CH4 25 Nitrous oxide N2O 298 HFCs - 124 – 14 800 Sulphur hexafluoride SF6 22 800 PFCs - 7 390 – 12 200

LCA data and product based environmental declarations Prior to the life cycle assessment of structures, material and product specific life cycle data should be known. For making assessment easier and more consistent, The European Platform on LCA has been established. This was launched by the European Commission and carried out by the Commission’s Joint Research Centre, Institute for Environment and Sustainability (JRC-IES) in collaboration with DG Environment, Directorate for Sustainable Development and Integration. The purpose has been providing reference data and recommended methods for LCA studies to improve credibility, acceptance and practice of LCA in business and public authorities. The main deliverables include the following:

− Internationally coordinated and harmonized ILCD Handbook of technical guidance documents for LCA.

− LCA information hub to ease the access to data and methods and to facilitate knowledge exchange, comprising among others also a global LCA Resources Directory with software, database and service providers.

− European Reference Life Cycle Database (ELCD) with European scope inventory data sets.

In parallel to ELCD, many internationally recognized life cycle databases for building products and materials exist. One, which is often referred to for plastics, is a web-based solution from the European Plastic Industry, PlasticsEurope. A known database is also the EcoInvent database but also LCA tools like Gabi, Simapro, Athena etc. contain their own databases for material production, transportation, chemicals, and acquisition of energy raw-materials. The European building sector has been very active in developing product category rules for the assessment and declaration of environmental impacts of building materials and products. This has happened both on the national level and on the European level. Currently CEN/TC 350 is developed standardised methods for the sustainability assessment of products and buildings (EN 15804).

1.3 Life cycle costing analysis

Life-cycle cost analysis (LCCA) is a tool to determine the most cost-effective option among different competing alternatives. ISO standard 15686, for service life planning, has been developed by Technical Committee ISO/TC 59, Building construction - Subcommittee SC 14. Design life is a decision process which addresses the development of the service life of a building component, building or other constructed work like a bridge or road. Its approach is to ensure a proposed design life has a structured response in establishing its service life normally from a reference or


estimated service life framework. The life cycle costing standard (ISO 15686-5) provide an in-depth guide to life cycle costing, an area of increasing importance. For example, for a pedestrian and bicycle pavement, in addition to construction cost LCCA takes into account also future periodic maintenance costs. All the costs are usually discounted total to a Net Present Value (NPV).


2. Goal and scope

The study is a subtask of the VTT’s CLASS project (Climate Adaptive Surfaces) with the objective of life cycle assessment of pavements. The study has concentrated on pavements which are used in walkways, backyards, and bicycle lanes, those which are subjected to light traffic loads. The goal here is to compare conventional and permeable pavement solutions for the applications used in Finland with regard to the carbon footprint and life cycle costing analysis.

The objective are met by: • evaluating structures for conventional and permeable walkways, • considering life cycle data sources from VTT database and literature for the material

types used, • performing life cycle assessment and costing analysis for chosen pavement types, • evaluating the result with regard to carbon footprint and cost.

3. System boundaries

The scope of this study was to compare carbon footprint for permeable and conventional, impermeable, pavement solutions. The scope includes the sets of functional unit, analyse period, life cycle phases and system boundaries. According to the methodology of LCA and LCC, comparison of pavement structures should be performed on alternatives with the same functional unit which includes both, the definition of “reference unit” and “quantified technical performance”. The reference unit is based on the case with defined dimensions, used materials and structures. All compared alternative structures are dimensioned for the light traffic area (katupiha) with corresponding load bearing capacity. The structures are designed for handling stormwater runoffs, which always depends on local soil and pavement properties. When the soil has very poor infiltration rates, part of the stormwater in the sub-base is conducted through a perforated underdrain pipe to the soil with better absorption or the stormwater can be stored temporarily in a gravel layer for later, low speed infiltration. To achieve similar stormwater drainage capacity between impermeable and permeable pavement, the drainage pipes and manholes are used in the cases when needed:

• impermeable pavement structure: the drainage system is needed, • fully permeable structure: it is assumed that no drainage system is needed and • partly permeable structure: the drainage might be needed only in a small extent, as

the excessive stormwater could be led to the sub-bases or to an area with better infiltration.

In this study, the location with soil properties, needed subgrades (type and layer thickness) and pavement types is based mainly on an example case study from the intended Oulu city pilot case of the Soittajakangas neighbourhood (Municipal engineering plan for Soittajakangas, date 15.8.2014, Ramboll Oy) but also for some hypothetical structures. The Oulu city case study of Soittajakangas contains four smaller walkway areas called Tähti, Tempo, Lyyra and Rytmi. The pavement structures are chosen from the plan of Katupiha 2, Rytmi. The Rytmi area (total size is 640 m2) contains pavement structures with different area


sizes, yet for unifying the area sizes in this LCA and LCCC alternative comparison, an area size 25 m2 was chosen for each paving material type The LCA assessment is made by taking use of main Life cycle assessment principles, according to ISO 14040 and 14044. The life cycle costing-method (LCCA) is based on corresponding ISO standard 15686-6, Life-cycle costing. Carbon footprint values, for the used materials and products, are based mainly on VTT’s database (ILMARI tool) and literature. The acquisition costs were defined using the information from literature (Research Report UCD-ITS-RR-48A) and were checked against with the data from the designer Ramboll Oy, as a CLASS project member. The calculation is aimed at the realistic cost level rather than exact costing. The construction costs on site are dependent on the wideness of work (in a small area unit costs are relatively high), transportation distances, and business cycle averages. The unit costs are given in Table 3.

Table 3. Unit acquisition and maintenance costs of alternative structures for light traffic (hypothetical structure).

Structure description Acquisition cost €/ m²

Repair cost €/m²/30y

Maintenance cost €/m²/30y

Impermeable structure 65 15 35

Solid asphalt 25 10 30

Base structures 15 5

Drainage manholes and pipes 25 5

Partly permeable structure 62 40 31

Concrete paving block 35 30 30


Drainage manholes and pipes 7 1

Fully permeable structure 50 20 40

Permeable porous asphalt 35 15 40


The assessment contains product stage (A1, A2 and A3) according to the ISO 15804, but also construction (A4 and A5) and use phase period, 30 year, with the maintenance (B2) and repair (B3). The cost analysis takes use of present value covering acquisition and maintenance costs:

• acquisition costs cover all builder costs, invoices of contractors etc. allocated to the acquisition unit,


• maintenance costs cover all costs caused both pavement maintenance and partial renewings within the calculation period, and

• the sensitivity analysis of results is based on cross-check of results.

The scenario for the maintenance (B2) conciders yearly operations for all compared structures: 2 times snow clearance and 2 times sanding (300 g/m2), each procedure lasts 5 min/25 m2. For permeable structures additional maintenance is needed 2 times per year to keep the surface penetration rate. The methods might be brushing, pressure or vacuum-cleaning (also 5 min/25m²).

The scenario for repair periods of surfaces (B3) is as follows:

• after every 20 years 10% of impermable asphalt is repaired,

• only minor repairment is considered for impermable concrete, during the use phase 30 years,

• every 5 years concrete paving block are straightened by light roller compaction,

• every 12 years 10% of permeable the asphalt is repaired.

4. Structures for conventional and permeable pavements

4.1 Conventional pavements

Two conventional pavement types, with impermeable asphalt surface and with impermeable concrete surface layer with needed subgrades, are assessed. The conventional pavements types are representing light traffic structures such as used for courtyards, pedestrian walking and cycling.

The stormwater handled with the structure includes a built in sewage system with pipes and manholes. It is hypothetically concluded that one manhole and 5 m of pipe are needed for the drainage of the 25 m2 area.

Table 4 and Table 5 show the structures for conventional pavement and subsequent subgrades used for light traffic.


Table 4. Conventional impermeable asphalt pavement structure for light traffic case (Rytmi, Katupiha 2).

Conventional, Asphalt Layer thickness

Density Weight Weight

mm kg/m3 kg/m2 kg/ 25m2 Surface layer, Asphalt (AB 11/100) 40 100 2 500 Profiling layer, (KAM 0…20mm) 50 1600 80 2 000 Load bearing layer, crushed aggregate (KAM 0 …55mm)

250 1600 400 10 000

Drainage course, sand (KH) 700 1800 1260 31 500 Drainage pipes PEH 110 5 running meter/25 m2 4.8 Drainage manhole ( Ø 600 mm)+ iron steel cap

1 units/25 m2 745

Total 1 040 46 750

Table 5. Conventional impermeable concrete pavement structure for light traffic (hypothetical structure).

Conventional, Concrete Layer thickness


mm kg/m3 kg/m2 kg/ 25m2 Concrete plate 80 2283 182 4 560 Bedding layer, sand KaS 6/16 50 1800 90 2 250 Filter cloth 0,2 0.24 6.0 Load bearing layer, crushed aggregate (KAM 0 …55mm)

250 1600 400 10 000

Drainage course, sand (KH) 700 1800 1260 31 500 Drainage pipes (PEH 110) 5 metres /25 m2 4.8 Drainage manhole (Ø 600 mm) 1 units / 25 m2 704 Total 1 080 49 072

4.2 Permeable pavements

Permeable pavements may have partly permeable or fully permeable structures. In the case of fully permeable structure pavement, the layers are fully permeable by serving as a reservoir to store the water from heavy rain and storms, whereas a partly permeable structure considers either partly permeable surface or also other partly permeable layers.

The dimensioning for permeability and water infiltration rate is not made but the assessment considers two fully permeable pavements and one partly permeable pavement structure.

Permeable pavement surface has as alternatives either a special mix of asphalt (porous asphalt) or a special mix of concrete (porous concrete). As the surface structure is porous, stormwater infiltrates through the surface into the sub base, which is a usually a dense gravel layer. The thickness of the gravel layer depends on the load bearing character of structure – mainly stiffness of the bottom soil - and from the frost heave behaviour of the soil.


Permeable pavements have also an occasional need for surface maintenance, which keeps permeable surface clean and free from fine material. Otherwise the amount of fine material might block the pores and thus turn the permeable structure into less permeable for stormwater filtration.

Impermeable concrete paving blocks with permeable sealing is an option for partly permeable structures. In addition, the concrete industry also produces permeable concrete paving blocks with permeable concrete mix which is studied in the permeable concrete pavement case.

For partly permeable structures, also stormwater sewers system with pipes and manholes are included to the assessment but for fully permeable structure these are considered to be not needed. In the Katupiha Rytmi, one stormwater inlet (manhole) is situated in the middle of the area (640 m2). It is concluded that this is for the case of partly permeable structures. This area is drained with the help of 55 m of stormwater drainage pipes (PEH 110). As the reference area was 25 m2 the allocation of pipes and manholes is made. According to that 2.15 m pipes (25 m2* 55 m/ 640 m2= 2.15 m) and 4% of manhole (1 manhole / 640 m2= 0.04 manhole / 25 m2) is allocated to the area 25 m2 for the case of partly impermeable surface.

Table 6. Partly permeable pavement structure with concrete paving block (Rytmi, Katupiha 2).

Concrete paving block Layer thickness


mm kg/m3 kg/m2 kg/ 25m2

Concrete paving block, (impermeable) 80 183 4 586

Jointing sand, (permeable) 1800 15 387

Bedding layer, sand (permeable) 50 1800 90 2 250

Load bearing gravel layer (KAS=16/32 VS)

350 1600 560 14 000

Drainage course, sand (KH) 630 1800 1134 28 350

Drainage pipes (PEH 110) probably not needed, but in this assessment 2.15 m/25m2 is

allocated

2.1

Drainage manhole (Ø 600 mm) probably not needed, but in this assessment 0.04 manhole/25m2 is

allocated

30

Total 1 110 49 605


Table 7. Fully permeable pavement structure with permeable concrete (hypothetical structure).

Permeable concrete Layer thickness



Permeable concrete plate 80 1970 158 3 940

Bedding layer, sand (permeable) KaS 6/16

50 1800 90 2 250

Filter cloth 0.2 0.24 6


250 1600 400 10 000


Drainage manhole (Ø 600 mm) not needed

Drainage pipes (PEH 110) not needed

Total 1 080 47 696

Table 8. Fully permeable pavement structure with porous asphalt (20 % air) (Rytmi, Katupiha 2).

Permeable asphalt Layer thickness



Permeable asphalt (AA 16/110) 40 110 2 750

Profiling layer, (KAM 0…20mm) 50 1600 80 2 000


350 1600 560 14 000


Drainage manhole (Ø 600 mm) not needed

Drainage pipes (PEH 110) not needed

Total 1 080 47 100

4.3 Life cycle data for main raw materials

4.3.1 Asphalt

Types

Asphalt is a material that contains crushed aggregates which are bonded together with bitumen and adhesive. Bitumen is the ingredient which has the highest environmental impact from the asphalt mix. It is made from pollutive coal or petroleum and obtained by distillation.


Depending on the traffic loads and needed performance different asphalt mixes are used. For example according to the asphalt mix classification, the asphalt types can be classified by sub-layer types:

• asphalt concrete (AB) is used in the surface layer (surface course),

• binding course asphalt mix (ABS) is used in the binding layer and

• load bearing layer asphalt mix (ABK) is used in the load bearing layer.

In addition to the layer classification, also smooth asphalt concrete (Pehmeä asfalttibetoni -PAB), stone mastics asphalt (Kivimastiksiasfaltti – SMA), porous asphalt (Avoin asfaltti – AA), cast asphalt (Valuasfaltti –VA) etc. exists. All the asphalt types have a different mix design and application cases as they are designed to fulfil different technical functions. This assessment considers two types of asphalt: asphalt concrete (AB11/100) and porous asphalt (AA16/110).

Lowering the amount of fine aggregates, the empty spaces in asphalt will increase and the asphalt gets high-permeability. Porous asphalt typically has a porosity (empty space) of 15 – 20 %, while the conventional asphalt has only 2 - 3 %.

Manufacturing technology

Asphalt is manufactured at asphalt plants by mixing hot aggregate with warm bitumen. The asphalt’s manufacturing temperature is high (100–180 °C), because at this temperature the bitumen will mix evenly with aggregates.

From an environmental point of view, as the asphalt is 100 % recyclable, it is important to know the use amount of reclaiming asphalt pavement (RAP). In the Nordic countries approximately 23 million tonnes of asphalt is produced from which approximately 4–5 million tonnes (~ 20%) is reclaimed asphalt. The majority of old asphalt is recycled as a raw material for new asphalt by replacing the most severe asphalt impacts caused by bitumen.

However, in this LCA pavement assessment, the used asphalt type was based on the EcoInvent database (described in the report Kellenberg et al 2007). In this, asphalt production represents mixing, heating and casting of raw materials according to current technology used in Switzerland. Even then, it can be assumed that the production technology is basically the same all over Europe

In this database, the consumption of raw materials, per kg of ready mix product, is in the following ratio: limestone powder (0.260 kg), sand (0.66 kg), bitumen (0.060 kg) and natural bitumen (0.020 kg). This ratio could be varied by different asphalt types but also from the use of reclaiming asphalt. Yet this assessment considers only conventional and porous asphalt production without using a reclaim asphalt amount. These different mix variations are the further subject for the asphalt industry if they find necessary in future LCA work.

However, also no separate LCA assessment is made for porous asphalt mix. It is considered that as the porous asphalt has porosity of 20%, resulting in the decreased specific weight and thus also to the decreased GWP impact.

Assembly

Assembly is based on the assumption made by Häkkinen & Mäkelä (Häkkinen & Mäkelä 1996)1.

1 Häkkinen, T., Mäkelä, K.1996. Environmental adaption of concrete. Environmental impact of concrete and asphalt pavements. VTT Research Notes 1752. 61 p. + app. 32 p.


Repair

Service life for asphalt pavement is dependent on the traffic load and asphalt wear. In this scenario-based pavement assessment, it is considered that impermeable asphalt lasts 20 year without repair, but after that the asphalt surface will be repaired by 10 %. In the case of permeable asphalt pavement more severe repair is considered, so that after every 5 years nearly 10% is repaired.

4.3.2 Concrete

Types

It is assumed that ready mix concrete (C30/35) is used for the impermeable concrete plates and concrete paving blocks. LCA data for the mix design, energy consumption and raw-material transportation is based on the average Finnish ready mix concrete plant assessment. The average concrete mix contains the following substances: cement (310 kg/m3), gravel and filler (1227 kg/m3), crushed aggregate (647 kg/m3), fly ash (8 kg/m3), blast furnace slag (2 kg/m3, plasticizer (2 kg/m3) and water 87 kg/m3.

Permeable concrete mix is based on VTT’s mix design (mix PC1): Plus-cement type (305 kg/m3), filler and sand (110 + 1455 kg/m3), air entrainment agent, plasticizer (9.5 kg/m3) and water (85 kg/m3).

LCA data for concrete ingredients is based as follows:

• cement - cement production at Finncement AB, Parainen factory, in 2012;

• gravel, crushed aggregate and sand - ELCD database,

• fly ash and blast furnace slag - as these are wastes by-products from energy and metal production, no environmental impact were allocated from the main process, only the impact from transportation is included.

Assembly

Concrete assembly is based on Häkkinen & Mäkelä report (Häkkinen & Mäkelä 1996). In case of concrete paving blocks assembly the energy consumption and thus carbon footprint is much smaller as the blocks are assembled by handwork.

Repair

It is considered that during 30 years operation the concrete paving needs only minor repair; only paving block straightening is needed after every 5 years by light roller compaction.

4.3.3 Gravel

Pavement structures contain sub-bases with crushed stones, gravel and sands. Unfortunately no exact life cycle data for certain sub-base fractions, with and without fines, was found and because of that the combination of available values is used. LCA data is based on ELCD database which represents European production value (RER).

Gravel and sand production processes which were taken into account in carbon footprint assessment were: mixing of gravel and sand from dry quarry, their transportations, washing, pre-classification, crashing and classification into two products sand 0/2 (ELCD database: Sand 0/2; wet and dry quarry; production mix, at plant; undried) and gravel 2/32 (ELCD database: Gravel 2/32; wet and dry quarry; production mix, at plant; undried).


Carbon footprint value of sand is mainly used in case of concrete and concrete paving block bedding layer and jointing, but also in the case, were drainage course sand is used.

Carbon footprint value for gravel is mainly used in case of load bearing layers but also in case of asphalt profiling layer.

Crushed stone process contains mixing of gravel from an open pit, arrangements of transportation, transportation, washing, crushing, classification into three products: crushed stone 0/2, grit 2/15 and gravel 16/32 (ELCD database: Crushed stone 16/32; open pit mining; production mix, at plant; undried).

Crushed stone carbon footprint value is used in case of concrete paving block structure for load bearing layer.

4.3.4 Infiltration systems with polyethylene pipes and manholes

Assessment considers 110 mm pipe and 600 mm manhole with the depth of 1.6 m in which 0.2 m is gravel bottom.

The manhole contains concrete tube with reinforcement, sealing and gravel bottom. Manhole raw-materials, energy and material consumptions as well as raw-material transportations are based on 600 mm manhole with 80 mm wall thickness and production at Rudus Oy Ab. Concrete manhole carbon footprint assessment is made with the help of BERTTA tool were cast iron cap assessment is added according to VTT’s calculation.

Drainage pipes are made from high density polyethylene which representing polyethylene production in Europe. Carbon footprint for polyethylene is based on PlasticEurope data (Eco profiles and Environmental Product Declarations of the European Plastics Manufacturers, High density polyethylene, 2014).

5. Results

5.1 Carbon footprint

The life cycle assessment for the different pavement structures is made and the result is shown as the carbon footprint for the life cycle phase production (A1 – A3), construction phase (A4 – A5) but also for the surface maintenance (B2) and repair (B3) during the 30 years of operation. The result for conventional asphalt and concrete pavement is given in Table 9 and for partly and fully permeable asphalt and concrete pavements in Table 10.


Table 9. Carbon footprint (CO2e) for the conventional pavement structures (Life cycle phases A1 – A3).

Conventional asphalt pavement

kg CO2e/25 m2

Conventional concrete pavement

kg CO2e/25m2 Surface layer 525 478 Profiling layer 6.8 20 (with filter cloth) Load bearing layer 34 34 Drainage course 77 77 Drainage pipes 8.6 8.6 Drainage manhole 152 152

Total 803 769

Table 10. Carbon footprint for the partly and fully permeable pavement structures (life cycle phases A1-A3).

Concrete paving blocks

Permeable concrete pavement

Permeable asphalt

pavement Surface layer 481 400 462 Profiling layer 5.5 20 (with filter cloth) 6.8 Load bearing layer 47 34 47 Drainage course 69 77 69 Drainage pipes 3.7 0 0 Drainage manhole 6.1 0 0

Total 613 530 585

Figure 2. Carbon footprint for the impermeable, partly permeable and permeable pavement structures (life cycle phases A1-A3).

0100200300400500600700800900

ConventionalAsphalt

ConventionalConcrete

ConcretePaving blocks

Permeableconcrete

Porousasphalt

kg C

O2e

/ 25

m 2

Drainage

Materials fromstructure


Figure 3. Layer share from total Carbon footprint pavement structure (life cycle phases A1-A3).

Carbon footprint assessment is made also for the life cycle phase’s construction and use containing raw-material transportation to the site, paving, maintenance and repair. Result is shown in the Figure 4.

Figure 4. Carbon footprint for pavement over whole service life of 30 year (including product phase A1-A3, construction phase A4-A5, use phase B2 and B3).

0 %10 %20 %30 %40 %50 %60 %70 %80 %90 %

100 %

ConventionalAsphalt

ConventionalConcrete

ConcretePaving blocks

Permeableconcrete

Porous asphalt

Surface Profiling layer Load bearing layer

Drainage course Drainage pipes Drainage well

0

200

400

600

800

1000

1200

1400

1600

Conventionalasphalt

pavement

Conventionalconcrete

pavement

Concretepaving blocks

Permeableconcrete

pavement

Porousasphalt

pavement

kg C

O2e

/ 3

0 ye

ar

B3B2A4-A5A1-A3


Figure 5. Life cycle stages share from total Carbon footprint pavement structure (including product phase A1-A3, construction phase A4-A5, use phase B2 and B3).

5.2 Life cycle costing analysis

Life cycle costing analysis is based on the examples of impermeable and permeable asphalt pavements and concrete paving block solution. Results for Life Cycle Costing of compared alternatives are presented in Figure 6.

Fully permeable structures are economical solutions compared to impermeable structures, in the Oulu city light traffic case study. Concrete pavements may be recognized as more valuable looking than open asphalt.

Sensitivity analysis (25 % higher costs in case of permeable structures as pessimistic alternative and 25 % lower costs as optimistic alternative) shows that the life cycle costs of permeable structures could be even over 15 % higher than calculated to be still economical (Figure 7).

0 %10 %20 %30 %40 %50 %60 %70 %80 %90 %

100 %

Conventionalasphalt

pavement

Conventionalconcrete

pavement

Concretepaving blocks

Permeableconcrete

pavement

Porous asphaltpavement

kg C

O2e

/ 3

0 ye

ar

B3B2A4-A5A1-A3


Figure 6. Life Cycle Costs (€/m²/30y) of alternative surfaces (Acquisition costs cover all labour, material, sub contract etc. costs caused for the client, maintenance costs cover all costs caused by annual condition keeping of surfaces and repair costs all costs caused by structural refurbishments).

Figure 7. Savings in LCC (€/m²/30y) of fully permeable structure compared to impermeable structure.

0

20

40

60

80

100

120

140

Impermeable structure Partly permeable structure Fully permeable structure

REPAIR COST MAINTENANCE COST ACQUISITION COST

€/m²/30y

-40

-30

-20

-10

0

10

20

30

40

MAINTENANCE AND REPAIR COST

ACQUISITION COST

€/m²/30y


6. Conclusions

The objective of this study has been life cycle assessment and life cycle cost assessment of permeable and impermeable pavements used in Finland for light trafficked areas such as walkways.

It is recognized that in this small case study it is impossible to consider all different materials, climates, subgrades, structural cross sections as a variable of performance, cost and impacts. Therefore, just pre-defined structures and only one impact category, global warming calculated as carbon footprint, is considered for this example LCA assessment.

For a more complete assessment, a precise calculation model would need to be built for different pavement types which take into account all possible variables in land and structure performance including also service life and maintenance needed. For the whole life cycle analysis besides material types, their acquisition, transportation and production also material recyclability, construction works, maintenance and repair with the end of life scenarios need to be considered (ISO 15804 and ISO 15686-5). This assessment presented here now contains life cycle stages A1, A2, A3 representing used materials, life cycle stages A4 and A5 representing material transportation and construction works and life cycle stages B2 and B3 representing the use phase with maintenance and repair needed for 30 years of operational service life.

The life cycle assessment of pavement structures shows that the carbon footprint from the pavement surface has the highest value compared to the other sub-bases (life cycle phases A1 – A3). The surface responds to 65 – 80% of the total pavement structures’ carbon footprint. All permeable pavement structures show less carbon footprint than conventional solutions. This is because it was assumed that the permeable pavement structure does not need conventional drainage systems but also because of the material types used for surfaces. The lowest carbon footprint value was achieved for the structure made having a permeable concrete surface. This case considered an environmentally-friendly cement type as well as lighter concrete than in the case of a conventional impermeable structure. When also other life cycle phases such as construction, maintenance and repair are taken into account the highest carbon footprint was in the permeable asphalt pavement case. This was because it was assumed that more maintenances care and repair were needed over the defined service life period consistent with pervious concrete. The result would have been more favourable if lighter repair and maintenance scenario would have been considered.

Although this brief case study was done using only partly source information, it has shown that it is both possible to compare LCC of the alternative materials and pavement structures with each other and that the permeable structures are worth analysing. Any future full LCCA should be based on the following boundaries:

• Thorough structure description of material and design alternatives, defined for specific area

• Use of Fore-/Hola etc. costing information (FORE) with its correction factors (for example geographic situation and other circumstances like size of area, reserves for extra works and risks) to estimate realistic costs of defined alternatives in specific area


• Setting boundaries for acquisition of contractors, for example time of repair responsibility and use of Finnish surfacing products.

• Use of costing information of areal maintenance service organisation to calculate maintenance costs of defined alternatives based on typical maintenance programme

• Estimate of non-measurable quality differences between alternatives

• Estimation of areal risks taking especially financial, safety and flood risks in account.

The results of this LCA and LCCA study are being used by the CLASS project partners, when planning Finnish guidelines for implementation of pervious pavement solutions as well as when preparing for future pervious pavement demonstration pilot areas.


References

BERTTA Tool for the life cycle assessment of concrete products. Created at VTT (or the Finnish concrete industry use

ELCD European Reference Life Cycle Database http://eplca.jrc.ec.europa.eu/ELCD3/index.xhtml

FORE - Infrarakentamisen kustannushallinnan ohje Helsingin kaupungille. Cost management guide of infrastructures for city of Helsinki. Rapal 11/2011

Holt, E., Kuosa,H, Wahlgren, I., Kling, T., Korkealaakso, J. Läpäisevien päällysteiden CLASS –hanke. Class-project - pervious, climate adaptive surfaces. Betoni 2/2014, 36 – 41 pp.

Häkkinen, T., Mäkelä, K.1996. Environmental adaption of concrete. Environmental impact of concrete and asphalt pavements. VTT Research Notes 1752. 61 p. + app. 32 p.

ILMARI tool. Tool for carbon footprint assessment of building structures and buildings. http://www.vtt.fi/sites/ilmari/ (site in Finnish)

ISO 14020:2000. Environmental labels and declarations. General principles.

ISO 14040:2006. Environmental management. Life cycle assessment. Principles and framework. 20 p.

ISO 14044:2006. Environmental management. Life cycle assessment. Requirements and guidelines. 46 p.

ISO 14025:2000. Environmental labels and declarations − Type III environmental declarations. Principles and procedures. 25 p.

ISO 15804:2012. Sustainability of construction works. Environmental product declarations. Core rules for the product category of construction products.

ISO 15686-5: 2008 Buildings and constructed assets. Service life planning: Part 5, Life-cycle costing. (New version under development) 42 p.

Kellenberger D. Althaus H.-J., Jungbluth N., Künniger T. 2007 Life Cycle Inventories of Building Products. Final report ecoinvent Data v2.0. Duebendorf, CH. Swiss Centre for LCI, Empa – TSL. 98 p.

PlasticsEurope 2014 Eco-profiles and Environmental Product Declarations of the European Plastics Manufacturers 2014. High-density Polyethylene (HDPE), Low-density Polyethylene (LDPE), Linear Low-density Polyethylene (LLDPE). April 2014.

Research Report UCD-ITS-RR-48A.Framework for life-Cycle Cost Analyses and Environmental Life-Cycle Assessments for Fully Permeable Pavements. Institute of transportation studies.

http://eplca.jrc.ec.europa.eu/ELCD3/index.xhtml

http://www.vtt.fi/sites/ilmari/

life cycle assessment (lca) and costing analysis (lcca ... · cycle costing in the finnish class...

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