VTT-R-00068-15
RESEARCH REPORT
Life Cycle assessment (LCA) and
costing analysis (LCCA) for
conventional and permeable
pavement walkways
Authors:
Sirje Vares & Sakari Pulakka
Confidentiality:
Public
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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 CLASSproject 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
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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
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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-tograve). 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.
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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.
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Table 1. Impact categories of LCA.
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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
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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).
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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
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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
Impermeable structure
Acquisition
cost
€/ m²
Repair
cost
€/m²/30y
Maintenance
cost
€/m²/30y
65
15
35
Solid asphalt
25
10
30
Base structures
15
5
Drainage manholes and pipes
25
Partly permeable structure
62
40
31
Concrete paving block
35
30
30
Base structures
20
10
Drainage manholes and pipes
Fully permeable structure
5
7
1
50
20
40
Permeable porous asphalt
35
15
40
Base structures
15
5
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,
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•
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 vacuumcleaning (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.
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Table 4. Conventional impermeable asphalt pavement structure for light traffic case (Rytmi,
Katupiha 2).
Conventional, Asphalt
Surface layer, Asphalt (AB 11/100)
Profiling layer, (KAM 0…20mm)
Load bearing layer, crushed aggregate
(KAM 0 …55mm)
Drainage course, sand (KH)
Layer
thickness
mm
40
50
250
Density
Weight
Weight
kg/m3
1600
1600
kg/m2
100
80
400
kg/ 25m2
2 500
2 000
10 000
700
1800
1260
31 500
Drainage pipes PEH 110
Drainage manhole ( Ø 600 mm)+ iron
steel cap
Total
5 running meter/25 m2
1 units/25 m2
4.8
745
1 040
46 750
Table 5. Conventional impermeable concrete pavement structure for light traffic (hypothetical
structure).
Conventional, Concrete
Concrete plate
Bedding layer, sand KaS 6/16
Filter cloth
Load bearing layer, crushed aggregate
(KAM 0 …55mm)
Drainage course, sand (KH)
Drainage pipes (PEH 110)
Drainage manhole (Ø 600 mm)
Total
4.2
Layer
thickness
mm
80
50
0,2
250
Density
Weight
Weight
kg/m3
2283
1800
1600
kg/m2
182
90
0.24
400
kg/ 25m2
4 560
2 250
6.0
10 000
700
1800
1260
31 500
5 metres /25 m2
1 units / 25 m2
1 080
4.8
704
49 072
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.
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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
Concrete paving block, (impermeable)
Layer
thickness
mm
Density
Weight
Weight
kg/m3
kg/m2
kg/ 25m2
183
4 586
1800
15
387
80
Jointing sand, (permeable)
Bedding layer, sand (permeable)
50
1800
90
2 250
Load bearing gravel layer (KAS=16/32
VS)
Drainage course, sand (KH)
350
1600
560
14 000
630
1800
1134
28 350
Drainage pipes (PEH 110)
Drainage manhole (Ø 600 mm)
Total
probably not needed, but in this
assessment 2.15 m/25m2 is
allocated
probably not needed, but in this
assessment 0.04 manhole/25m2 is
allocated
1 110
2.1
30
49 605
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Table 7. Fully permeable pavement structure with permeable concrete (hypothetical
structure).
Permeable concrete
Layer
thickness
mm
Density
Weight
Weight
kg/m3
kg/m2
kg/ 25m2
Permeable concrete plate
80
1970
158
3 940
Bedding layer, sand (permeable) KaS
6/16
Filter cloth
50
1800
90
2 250
0.24
6
Load bearing gravel layer (KAS=16/32
VS)
Drainage course, sand (KH)
0.2
250
1600
400
10 000
700
1800
1260
31 500
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
mm
Density
Weight
Weight
kg/m3
kg/m2
kg/ 25m2
110
2 750
Permeable asphalt (AA 16/110)
40
Profiling layer, (KAM 0…20mm)
50
1600
80
2 000
Load bearing gravel layer (KAS=16/32
VS)
Drainage course, sand (KH)
350
1600
560
14 000
630
1800
1134
28 350
Drainage manhole (Ø 600 mm)
not needed
Drainage pipes (PEH 110)
not needed
Total
4.3
4.3.1
1 080
47 100
Life cycle data for main raw materials
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.
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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.
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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 rawmaterial 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).
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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.
RESEARCH REPORT VTT-R-00068-15
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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
803
769
Total
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
613
530
585
kg CO2e/ 25 m 2
Total
Drainage
900
800
700
600
500
400
300
200
100
0
Materials from
structure
Conventional Conventional Concrete
Permeable
Asphalt
Concrete Paving blocks concrete
Porous
asphalt
Figure 2. Carbon footprint for the impermeable, partly permeable and permeable pavement
structures (life cycle phases A1-A3).
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100 %
90 %
80 %
70 %
60 %
50 %
40 %
30 %
20 %
10 %
0%
Conventional Conventional
Concrete
Paving blocks
Asphalt
Concrete
Permeable
concrete
Porous asphalt
Surface
Profiling layer
Load bearing layer
Drainage course
Drainage pipes
Drainage well
Figure 3. Layer share from total Carbon footprint pavement structure (life cycle phases A1A3).
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.
1600
kg CO2e / 30 year
1400
1200
1000
800
600
400
200
0
B3
B2
A4-A5
A1-A3
Conventional Conventional Concrete
asphalt
concrete paving blocks
pavement
pavement
Permeable
concrete
pavement
Porous
asphalt
pavement
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).
RESEARCH REPORT VTT-R-00068-15
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100 %
90 %
kg CO2e / 30 year
80 %
70 %
60 %
50 %
40 %
30 %
20 %
10 %
0%
B3
B2
A4-A5
A1-A3
Conventional Conventional
Concrete
asphalt
concrete
paving blocks
pavement
pavement
Permeable Porous asphalt
concrete
pavement
pavement
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).
RESEARCH REPORT VTT-R-00068-15
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140
€/m²/30y
120
100
80
60
40
20
0
Impermeable structure
REPAIR COST
Partly permeable structure
MAINTENANCE COST
Fully permeable structure
ACQUISITION COST
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).
40
30
€/m²/30y
MAINTENANCE AND REPAIR COST
ACQUISITION COST
20
10
0
-10
-20
-30
-40
Figure 7. Savings in LCC (€/m²/30y) of fully permeable structure compared to impermeable
structure.
RESEARCH REPORT VTT-R-00068-15
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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
RESEARCH REPORT VTT-R-00068-15
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•
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.
RESEARCH REPORT VTT-R-00068-15
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