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Materials role in pavement design and its impacts
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SBEfin2022 Emerging Concepts for Sustainable Built Environment (SBEfin2022)
IOP Conf. Series: Earth and Environmental Science 1122 (2022) 012037
IOP Publishing
doi:10.1088/1755-1315/1122/1/012037
1
Materials role in pavement design and its impacts in LCA of
road construction and use phase
K Negishi, R De Montaignac, N Miravalls
ORIS, 54 avenue hoche, 75008 Paris, France
koji.negishi@oris-connect.com
Abstract. Connecting real material databases at a very early stage enables to measure, predict
and support informed decision making based on energy and carbon performance in the
infrastructure sector. While, in the past twenty years, a significant increase of Life Cycle
Assessment (LCA) research for road construction projects was seen, data collection and
management still remains one of the main challenges. Having a capability to combine the
planning, execution, maintenance and recycling on one platform greatly contributes to reducing
the effort and assessment execution time and early stage decision makings. ORIS is the first
web-based material platform enabling more sustainable road construction with optimised
solutions, bringing an assessment of different pavement design options within a geolocalised
material sourcing environment. Based on the embedding local design catalogues and its
automatized data-driven approach, an exhaustive LCA analysis is performed on road for its
whole life cycle conformed to LCA standards. A case study in the United Kingdom
demonstrated the life cycle carbon and cost assessment with a significant contribution of use
phase modules (30-40% of the total) and the potential of 56% reduction in the global warming
indicator from the product and construction phase and 24% in total life cycle saving 720 k£.
1. Introduction
700 000 km of new roads are built worldwide each year. Materials and pavement design choices
impact up to 60% of the cost of a road project and about 85% of its overall greenhouse gas emissions.
Most roads are designed according to standardised and historical road design methods, where
materials availability and adequacy are considered only later at the construction phase due to the
difficulty in data collection and the lack of systematic approach. Such approach from the road
ecosystem (owners, investors, designers, contractors) lacks to integrate sustainability requirements
such as climate change mitigation, natural resources scarcity or social disparities. Connecting real
materials databases at a very early stage enables to measure, predict and support informed decision
making. ORIS is the first material platform, which is a web-based multi-user and multi-service that
will enable more sustainable road building with optimised solutions for each local sourcing
environment. Users are from the road ecosystem at large: material suppliers, road contractors,
engineering firms or road authorities and even financial institutions and infrastructure financiers.
Integrated in Building Information Modeling (BIM) workflow, an assessment of different pavement
design options is instantly performed. First road alignment is loaded into the platform that geolocalises
the project and material sourcing opportunities. Embedding local design catalogues, the user has the
capacity to select several pavement structures from all visualized designs in order to compare and to
choose their preferred design according to their priorities: carbon footprint mitigation, increased
durability, local materials, cost reduction. Beyond pavement choice, the users can select several
SBEfin2022 Emerging Concepts for Sustainable Built Environment (SBEfin2022)
IOP Conf. Series: Earth and Environmental Science 1122 (2022) 012037
IOP Publishing
doi:10.1088/1755-1315/1122/1/012037
2
maintenance scenarii to be compared and assess the impact on the use phase. The key to success is the
capability to combine planning, execution, maintenance and recycling on one platform. Our global
approach is creating impact at every stages of road life cycle. Furthermore, this data-driven approach
and abundant geolocalised material databases enable to extend to rails or even other transport
infrastructures, which are important public expenses for any country budget.
Recent review works revealed the significant increase in the research on LCA applied to road
construction projects in the last twenty years [1–4]. In fact, this shows the enhancement of the
sustainable strategy on the infrastructure. Meanwhile, they also highlighted that the majority of
published studies were involved in an inconsistency in the functional unit and an incomplete system
boundary. Subsequently, main challenge in data collection and a significant execution time of an LCA
study finally leads to the unavailability of results and decision makings before at the early design
stage. To the best of our knowledge, none of existing studies provided a systematic approach enabling
full and easier road LCA. In order to improve sustainability in road construction, the swiftness and
data availability using data science techniques are of great importance and allow performing the
project assessment at the very early stage.
To meet these challenges, an exhaustive and data-driven approach is required in order to promptly
and seamlessly performs an extended level analysis of a road pavement design performance during its
whole life cycle stages, conformed to LCA standards (ISO 14040/14044 and EN15804). From the
original construction - including material productions, transport and construction operations - with
customised options in terms of materials actual properties and pavement solutions, the developed tool
expands its analysis to the road use and maintenance phases, up to the end-of-life stage, compared to
previously developed road LCA approaches that in most cases only consider production and
construction stages. State of the art models are used to incorporate the impact of the road use due to
specific pavement properties (albedo, carbonation and lighting) and the impact due to Pavement-
Vehicle Interactions (PVI). The modules associated with PVI take into account not only pavement
mechanical characteristics and the pavement ageing but also the evolution of annual average daily
traffic (AADT) and local climate conditions over the road service lifetime in order to calculate
increased vehicle fuel consumptions.
To be in accordance with the referred LCA standards, the carbon footprint is calculated by applying
the life cycle impact assessment (LCIA) method, which converts the resource use and emissions
contained in the life cycle inventory to the Global Warming Potential (GWP) indicator (kgCO2eq.).
Moreover, given the early design focus, data quality assessment should be carried out for inventory
datasets to incorporate uncertainty in results.
A case study is presented to demonstrate the potential of the tool to uncover the environmental
impact of the different decisions made during the design of a project as well as the indirect effects that
decisions made in one phase (e.g. construction or maintenance) can have on the subsequent use phase.
Compared to most conventional road LCA approaches only covering a part of the life cycle, our
solution scientifically based on data proves that holistic assessment over the full life cycle is a key to
improve the overall sustainability of the road infrastructure. Besides carbon footprint criteria, material
circularity (recycled materials used in the project and potential benefits from demolition waste) is
monitored to support users even more sustainably and economically driven decision making.
2. Digital solution of life cycle approach
The conventional road LCA approach includes only the impact of product, transport, construction and
maintenance operations, while the impact during the use phase would help with a more precise
evaluation and to improve decision making. To fill this gap, a methodology dedicated to a holistic road
LCA with an extensive database with verified material and carbon data was developed, combined with
climate data from NASA, in order to calculate GWP indicator with uncertainty. GWP results are
calculated for each year of the life cycle and shows how the overall impact increases during the whole
life cycle of the road project. The assessment with the use phase increasingly contributing to the
SBEfin2022 Emerging Concepts for Sustainable Built Environment (SBEfin2022)
IOP Conf. Series: Earth and Environmental Science 1122 (2022) 012037
IOP Publishing
doi:10.1088/1755-1315/1122/1/012037
3
overall result helps to better identify the potential for reduction in GWP and avoid ramifications in the
decision making.
There is today a huge trade-off between high material demand and climate concerns while
Brundtland’s report [5] introduced the idea of sustainable development with a focus on a proper
management of material supply to mitigate resource uses and greenhouse gas (GHG) emissions. ORIS
platform gathering construction materials information and knowledge makes it accessible for the entire
construction ecosystem. The tool paves the way to sustainable road construction through its digital
platform providing circular, low-carbon, and resource optimised solutions for safer and more resilient
roads. These evaluations are performed on the basis of Life Cycle Assessment applied to road
construction projects, initially developed by Holcim Innovation Centre [6] and then its API established
was deployed in the web-based tool. The figure shows the developed digital solutions for LCA
calculations and its link with background databases. In total, 8 calculations core function separately
and are called as an API service, each of which investigate at each calculation request material and
CO2 emission factor stored in background SQL databases. The calculation is completed by climate
data via POWER web service from NASA. The result of GWP indicator is assessed by applying
characterization factors from CML (Centrum voor Milieukunde Leiden) method [7] as a reference
method to be in accordance with the LCA standards.
Figure 1: Architecture of the digitised solution of carbon footprint assessment
The following subsections summarise the functionalities of ORIS platform and a general
configuration of the tool usage as well as evaluated life cycle assessment indicators.
2.1. Pavement design
From the embedded catalogue of pavement structural designs, ORIS proposes multiple solutions of
pavement based on a very few user inputs. In general, the catalogues for countries of interest are
preliminary elaborated considering a limited number of input essentially with traffic volume, subgrade
soil quality and local climate conditions and additionally with the type of pavement (flexible, semi-
rigid or rigid). Combining these first level inputs, the thickness of each layer of proposed structure is
calculated. It is important to note that the method of structural design, criteria of layer sizing and
available materials differ from a country to another and not necessarily the same pavement designs are
elaborated. Therefore, prior to the project, the literature review should be performed to understand the
method of structural designing, available and useful materials, and minimum and maximum thickness
of the pavement according to country standards.
Using catalogues is a great support for engineers and drastically reduces the time at the pavement
design phase. Moreover, it makes it possible to perform an LCA study at the very early stage of a
project because it solves the unavailability of data for LCA modelling. In most LCA studies, the lack
SBEfin2022 Emerging Concepts for Sustainable Built Environment (SBEfin2022)
IOP Conf. Series: Earth and Environmental Science 1122 (2022) 012037
IOP Publishing
doi:10.1088/1755-1315/1122/1/012037
4
of data leads to LCA performance only after the project is already in the construction phase or
finalised.
2.2. Material cost and carbon datasets
ORIS employs a unique material sourcing database which helps to link a road construction project to
locally available materials. In order to have a complete analysis, the first step of a project consists of
feeding the platform with required data concerning the sourcing locations, the local available materials
and the standards. The data required for the successful completion of the database is collected from
various data sources including data provided by clients and data available within the area of interest.
This database incorporates material production sites such as asphalt, bitumen, cement, concrete and
any other raw materials needed for a project. Material prices are, on one hand, retrieved from
contractors introduced in a cost database dedicated to a project. On the other hand, a database
gathering the carbon emission factors is built to being feed by two types of data: 1) background raw
material carbon emission factors from generic environmental databases (e.g., Ecoinvent) and 2)
foreground inventory flow (e.g., material and energy consumption for asphalt production). These two
types of dataset are combined with to have carbon emission factors of final products.
2.3. Consideration of use phase modules
Since 2010, LCA researchers are increasingly investigating the effect on environmental impact due to
the road use and finding out a wide ramification on final decision makings because each of the use
phase modules has potentially a significant contribution to the overall LCA results. However, still few
developed a systematic and automatized approach in LCA in general and even less in LCA for road
projects. ORIS’s data management platform enables to automatize LCA calculations not only for
product and construction stages but also for maintenance operations and its influence to pavement
quality over age. A total of 6 use phase modules have been built and made available. Three of the
modules relate to pavement-vehicle interactions (deflection, roughness and texture) while the
remaining three are related to the pavement properties (albedo, lighting and carbonation). The modules
of PVI takes into account a pavement evolution over time (e.g., change in material properties due to
maintenance, increase in international roughness index due to pavement deterioration) along which
extra fuel consumptions resulted from rolling resistance due to surface texture [8] and roughness [9],
and deflection [10] as a structural asset. CO2 emissions of vehicles associated with extra fuel
consumption are quantified. A daily average traffic volume of passenger cars and heavy trucks is
combined with these models. Besides, direct environmental interventions from the pavement are
measured by considering albedo [11], carbonation [12] and lighting [13] on the pavement surface.
Albedo and carbonation modules would have a net balance of global warming potential below zero,
meaning that a pavement solution would reduce global warming potential by offsetting a global
balance of carbon dioxide in the atmosphere. Furthermore, the calculations use local climate data
(solar radiation, air temperature, precipitation and surface albedo). The data was obtained from the
National Aeronautics and Space Administration (NASA) Langley Research Centre (LaRC) Prediction
of Worldwide Energy Resource (POWER) Project funded through the NASA Earth Science/Applied
Science Program.
2.4. Material and operating cost
ORIS performs life cycle cost analysis alongside carbon footprint analysis. The product stage (A1-A3)
estimates the cost related to raw material production, transport and manufacturing of mixed products.
The transport (A4) cost includes the finished product transportation from the production site to the
project main access point. The construction process (A5) cost includes the internal transport cost of
materials from a main access point to other work locations within the construction site as well as fuel
consumptions of engine used for the placement of each layer (e.g., paver, compactor, field crews). For
each road project, these operating cost data retrieved from different constructors and estimates a total
SBEfin2022 Emerging Concepts for Sustainable Built Environment (SBEfin2022)
IOP Conf. Series: Earth and Environmental Science 1122 (2022) 012037
IOP Publishing
doi:10.1088/1755-1315/1122/1/012037
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operating cost are introduced into the platform. Additionally, it calculates service life cost associated
with the maintenance operations (B2-B4).
2.5. Natural resource use
Enhancing natural resource use in a project would have a consequence of reducing available amounts
of natural resources in other projects. The conservation of natural resources and the reduction of use
by designing a pavement with material-efficient structure become one of the essential goals in the
infrastructure sector, both environmentally and economically. ORIS elaborates the analysis on natural
resource uses through a road project based on primary and secondary road construction materials such
as aggregate, concrete, asphalt, cement treated material and water required for placement. The analysis
is performed both at a layer level and at material type level by monitoring primary and secondary
materials used.
2.6. Data quality assessment and uncertainty
Given the early design focus and low level user inputs, significant uncertainty is associated with data
overall the LCA modelling. Data quality assessment of both foreground and background data is
therefore critical in order to understand the potential gaps in results and select better the pavement
solution. Following the ecoinvent’s guideline [14], background data is characterised by basic
measurement uncertainty referring to possible errors when building inventory datasets. On top of this
basic uncertainty, it is important to add the potential variability in foreground data such as the amount
of materials used in pavement and material transport distances. ORIS takes into account these two
types of uncertainty and incorporates in final GWP results.
3. Case study
3.1. Description of the case study
The case study is the reconstruction of the existing 3.9 km with 16 m width carriageway ran from the
M6 Junction 36 and the Brettargh Holt roundabout in Cumbria, which is a major route into Southern
Cumbria. This construction project is identified as the first UK Carbon Neutral Scheme. Based on the
general road project information (e.g., location, road type, length, estimated traffic volume), ORIS was
able to generate multiple design solutions within the UK pavement standards and shortlisted standard
and alternative asphalt-based pavement options to be compared for the current case study. Table 1
summarises the two pavement designs that have been studied respectively based on the Design Manual
for Roads and Bridges [15] and the report from Transport Research Laboratory [16]. The design 1
with fully flexible pavement was chosen as a reference design in this case study. Compared to that, the
design 2 adopts a cold recycled foamix for a complete base course with the same thickness as the
reference design. Besides, the binder course in the design 2 uses the warm mix technology with the
advantage of reducing the amount of thermal energy for material mixing.
The service life is considered to be 40 years and a maintenance scenario was elaborated and applied
to the all two pavement options. In the 14th year after the first construction, the 40 mm is removed with
a milling machine and replaced by the same thickness of Thin Wearing Surface Course (TWSC). In
the 26th year, heavier maintenance is planned with the removal and replacement of 100 mm by 40 mm
of TWSC and 60 mm of Asphalt Concrete.
Table 1. Selected pavement designs for the case study
Fully flexible
(design 1 = reference)
Thickness
(mm)
Flexible foamix
(design 2)
Thickness
(mm)
Surface course
Thin wearing surface course
40
Thin wearing surface course
40
Binder course
Hot mix asphalt concrete
60
Warm mix asphalt concrete
60
Base course
Hot mix asphalt concrete
110
Cold recycled foamix
220
Base course
Hot mix asphalt concrete
110
SBEfin2022 Emerging Concepts for Sustainable Built Environment (SBEfin2022)
IOP Conf. Series: Earth and Environmental Science 1122 (2022) 012037
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doi:10.1088/1755-1315/1122/1/012037
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Total thickness
320
320
From the material database embedded in ORIS platform, the project found the material sourcing
sites of 10 asphalt plants and 13 quarries as well as 2 recycling facilities to which cold recycled foamix
was assigned in this project. Data science technique is used to find the best materials from locally
available sources by avoiding dense traffic of materials and trucks coming from far away. The
transport distance of materials is automatically calculated. The climate data was obtained from the
POWER Project’s daily 2.2.20 version and climatology v2.2.18 version on 2022/03/15.
The case study considers an annual average daily traffic volume of 2,000 that evolves by 10% a
year over 40 years and 10 % of the total traffic being truck.
The construction and maintenance activities estimate fuel consumptions of engines used for laying
each layer. It is assumed that the material properties such as IRI (m/km) or albedo value of the surface
are brought back to their initial values when replacement activities are performed at 14 and 26 years.
These effects of pavement structure and properties change combined with AADT, which are all
evolving over time, are then reflected into the use phase modules.
For the EOL module, for the sake of simplicity, it is assumed that 100% removed asphalt and
composite are sent to a waste treatment platform with a default transport distance of 50 km after the
demolition processes and considered to be subsequently reused. The processing of waste treatment
(sorting and grading) is modelled using an average waste treatment profile for this case study.
3.2. Results of LCIA and LCCA
The cumulative global warming impacts expressed in tonnes of CO2 equivalent and the results of life
cycle cost for the two pavement options are shown in Figure 2 and 3. Based on the ORIS assessment,
the Flexible foamix design (reference) appears as the best solution because of its optimum balance
between life cycle carbon performance and cost performance. Compared to the reference design, the
design 2 reduces the total GWP impact by 24% and the total operating cost by 14%, which is
equivalent to 790 k£ saving. GWP impacts are dominated by the material production (A1-A3), the
maintenance operation (B2-B4) and the PVI effect (B6) for both designs. The use of foamix and warm
mix asphalt technologies in the design 2 resulted in 56% reduction of the production phase compared
to the reference. It appears applying the low carbon material strategies makes the use phase and the
maintenance phase even more visible in terms of carbon performance. Also the choice of the service
life has a significant effect on the overall contribution of the use and maintenance phases. A longer
service life of a road leads to a clearer contrast in long term effect factors such as evolving traffic
volume and IRI as shown in Figure 4.
Figure 2. GWP impact assessment for two
pavement designs
Figure 3. Life cycle cost assessment for two
pavement designs.
SBEfin2022 Emerging Concepts for Sustainable Built Environment (SBEfin2022)
IOP Conf. Series: Earth and Environmental Science 1122 (2022) 012037
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doi:10.1088/1755-1315/1122/1/012037
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Figure 4. Cumulative GWP impact over the service life for the low carbon pavement
4. Conclusion
Early engagement with low carbon strategy leads to the development of a low carbon pavement
solution in infrastructure. Key to the success of a significant reduction in GWP impacts lays in the
combination of material-efficient pavement structure, local and optimum material sourcing, low
carbon materials technology and optimum maintenance operations. In addition to the reduction in
GWP impact, cost and material savings while ensuring safer and smoother pavement solutions
extensively meet the sustainable strategy in the infrastructure sector. This paper first presented the
overall ORIS’s digital platform linking real material markets with road construction projects. The
required carbon and cost data and a catalogue of multiple pavement solutions depending on structural
and local requirements are all embedded into the background databases enabling an automatized data-
driven approach. This disposition of data allows easing the pavement design process at a very early
stage. Second, a case study, involving two pavement solutions (reference and alternative ones), was
demonstrated to show how the ORIS assessment helps early stage decision makings for sustainable
roads.
As shown with the case study, considering materials from the early stage of road designs makes a
difference in terms of carbon and cost performance. The use of low carbon materials (cold recycled
foamix) locally identified thanks to ORIS’s material sourcing technique led to a tangible solution of
GWP reductions by 24% compared to the standard pavement solution. According to our internal
research, the choice of designs in road construction is a major factor on costs (60% of the total
construction costs) and carbon footprint (85% of carbon emissions). Each road is unique and is
dependent on its location. For increased sustainability, as shown in this example of A590, each road
should be designed taking into account the following elements:
Local sourcing: to optimise material supplies and avoid long distance transport;
Circular economy: using recycled materials to preserve natural resources being part of the
local equation from early stages of design;
Carbon footprint: given the climate urgency, carbon emissions reduction with adapted design
is a must for all sectors;
Durability: as the longevity of a road is key to avoid multiple maintenance work and ensure a
long service to communities.
Bringing materials engineering upfront in road construction and maintenance is a unique capability
for the market and will become a necessary behaviour in the future. It will make a major difference in
improving the carbon performance of the road infrastructure.
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SBEfin2022 Emerging Concepts for Sustainable Built Environment (SBEfin2022)
IOP Conf. Series: Earth and Environmental Science 1122 (2022) 012037
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doi:10.1088/1755-1315/1122/1/012037
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