Sustainable And Smart Pavements [S2P] – Working With The End In Mind


Dr. Chetan Hazaree
Head – Research & Development (Roads, Runways & Elevated Corridors)
L&T Construction (Transportation Infrastructure IC)

Introduction

The Need

Exceptional infrastructure systems in varied exposures are on a rise. There is ever increasing demand for additional infrastructure. But there is a direct consequence of ever-increasing population, growth of urban habitats, increasing population densities, need for faster and higher capacity transportation systems. Limited land availability, depleting natural resources and scarce monies are widening the demand-supply gap. Besides being exposed to natural hazards, the built structures deteriorate in their respective environments. This presents a unique situation. On one hand, the society needs enhanced performance, while capping the expenses, on the other hand, rapid environmental degradation is forcing optimal use and recycling. This necessitates the requirement to predict the real-time health of the built structures.

The construction revolution, especially during last 25 – 50 years, has resulted in a huge inventory of deteriorating structures and infrastructure. To ensure an economically and environmentally sustainable future, the continued usability of these structures must be guaranteed as much as possible. This challenge requires application of reliable and adaptive new materials for designing retrofitting systems and rehabilitation schemes.

The combined needs for existing and new structures are forcing higher performance with longer life. In-turn, real-time monitoring aimed towards predicting the health and remaining service life and need for repair and rehabilitation have become crucial.

The Gap

The investment gap between the investment needed and current investment trend for the road sector today across the world is forecasted to be 8 trillion USD by 2040. While the same gap for Indian road sector is forecasted to be 79 billion USD by 2040, [1] global infrastructure needs are daunting. Creating investable project pipelines and speeding the technological advancement of infrastructure development will not solve all the problems. These can however provide some important solutions, and help create a more connected, prosperous, and sustainable world [2]. Realizing the vision of sustainable and smart pavement is going to be rather long journey of patience, experimentation, innovation, rapid adaptation, and improvisation.

The Case Of Pavements In India

Pavements are an integral part of surface transportation or road network. Their wide-scale and preferred utilization provides unique opportunity to deliver environmental, social, and economic benefits. India has a total road network of 58,97,671 km, of which only 5% is constituted by National and State Highways. This composition presents multifarious opportunities to choose strategies for sustainable and/or smart pavements.


Fig.1: Road Network Break-up w.r.t. length [3]

Sustainable And Smart Pavement (S2P)

Realizing S2P needs elements of sustainable and smart construction from the project conceptualization stage. This could be followed by embedding sustainable and smart considerations at all major stages of a project cycle viz. planning, designing, construction, maintenance, refurbishing or entering new cycle. When it comes to roads, they by default include capacity, drainage systems, markings, signages, safety systems, roadside management, drainage structures, bridges and other structures that fall along the alignment. This article primarily focuses on the pavement structure and materials.

New And A Few Know It

Both the words viz. sustainable and smart have become industry jargons. Multiple sectors are progressively embracing the terms smarter, and more sustainable. Infrastructure systems, however, remain among the least digitally transformed in the entire global economy. Sustainability is being slowly introduced, but the pace could be radically increased. Each word, as a process, and a phenomenon is differently understood and applied in different contexts. Rather than going into the details of voluminous research, cases, and studies available, this article attempts to identify broad, relevant, and actionable agenda.

Today, the pavement engineers seem to be having many questions about sustainability. The primary ones include:

– What are the appropriate sustainability factors to be considered over the life cycle of a pavement (from material extraction to the end-of-life)?
– How do the various materials used in paving applications impact the overall sustainability of the pavement system?
– How can pavements be effectively designed and constructed to meet the specific sustainability needs of a given project?
– How can the pavement community make more sustainable choices?
– How does one consider trade-offs in the process?
– What methods are available to assess the sustainability of pavement systems?
– What implementation strategies are available for highway agencies to adopt more sustainable pavement practices?


Fig. 2: Vision for European Infrastructure in 2040

Definitions And Developments

Sustainable

“Sustainable” in the context of pavements refers to system characteristics that encompasses a pavement’s ability to – achieve the engineering goals for which it was constructed; preserve and (ideally) restore surrounding ecosystems; use financial, human, and environmental resources economically; meet basic human needs such as health, safety, equity, employment, comfort, and happiness [4].

Smart

‘Smart’ broadly includes three aspects viz. smart material, smart pavement systems, and smart monitoring system. Either singularly or in a combined mode, these are understood to represent smart; accordingly, definitions of ‘smart’ are coined. Following is a sampling of definitions:

A smart structure has intelligence and reaction capability embedded within it [5]. Smart structures represent a new engineering approach or design philosophy that integrates the actions of sensors, actuators and control circuit elements into a single system that can respond adaptively to environmental changes in a useful manner [6].

Smart pavement refers to roadways that have been specifically engineered and built to support a wide range of 21st century ITenabled features, making them “smart” in the process [7].

As conceived in India, ‘smart roads’ or ‘smart highways’ integrate technology with transportation infrastructure, including but not limited to, functions such as generating power through solar panels, integration with self-driving cars and sensors and structural maintenance monitoring systems. Smart highways have the opportunity to turn from serving a singular purpose of being the backbone of a country’s transportation system to provide additional value through generation of power, safety feature implementation and gathering of key data points for both road users and transportation administrators [8].

Sustainable And Smart Pavements (S2P) – A Case

Amalgamating, contextualizing, and prioritizing while establishing long-term trade-offs is crucial for achieving S2P. Accordingly, a global vision for the European infrastructure in 2040 is formed by the Forum of European National Highway Research Laboratories. This New Road Construction Concept (NR2C) vision is based on four key concepts representing the dominant characteristics of the society’s expectations for the road of the future:

  1. Reliable infrastructure, standing for optimizing the availability of infrastructure
    2. Green (environment friendly) infrastructure, standing for reducing the environment impact of traffic and infrastructure on the sustainable society
    3. Safe and smart infrastructure, standing for optimizing flows of traffic of all categories of road users and road construction work safety
    4. Human infrastructure, standing for harmonizing infrastructure with the human dimensions

Besides, it also insists on key factor for successful innovation: a shared will to innovate and a full engagement of all the actors [9].

Some Examples

Sustainability

Defining sustainability is easier than applying its principles. Each pavement case, either new construction or rehabilitation presents a unique case. It depends on what are the key considerations driving the sustainability agenda – whether societal, economical, and environmental. Thus, sustainability for pavement can often be reduced to understanding how each system component affects sustainability. For example, use of local marginal aggregate could be possible for constructing a village road, while transporting aggregate from 200-300 km may still be required for an expressway.

The effects of using a pavement could be understood in terms of material production, design, construction, usage, maintenance, and end-of-life of the pavement. This forms a complete pavement life cycle. Sustainability impacts greenhouse gas emissions, energy consumption, habitat loss, water quality, air quality, mobility, access, freight, community, non-renewable resources, economic development, changes in the hydrological cycles, etc.

Pavement sustainability assessment could be done in multiple ways – this is however an area of research. Performance assessment, life-cycle costing, life cycle assessment, pavement rating systems and integrated systems are some of the ways in which it could be assessed. While deciding on a project, a preference matrix for tradeoff between different considerations is often accounted for while arriving at a decision.

Some of the strategies for pavement sustainability in terms of materials, design and construction are summarized in Table 1 and Table 2. Similar strategies could be derived for maintenance, rehabilitation, and end of the design life phases of pavements.

Smart

Self-sensing, self-adapting, interacting with the loading and catering to multiple functionalities are the primary objectives of being smart. Smart pavement includes smart materials, smart design, smart monitoring, and smart multi-functionality. The possibilities are endless:

i. Energy harvesting – the pavement surface could be used for harvesting and storing energy, for example solar roads
ii. Charging of electric vehicles using harvested energy
iii. Self-powered wireless sensors capable of detecting damage and loading history for pavement structures, for example this data can be used for pavement diagnostics and for pavement management systems
iv. Self-healing materials, for example self-healing asphalt, bacterial concrete
v. Self-responding materials, for example magnetically triggered induction healing of asphalt
vi. Weigh-in-motion, auto-tolling, auto-challan, etc.
vii. Traffic flow coordination, accident reporting, traffic prediction, etc.

Eastern Peripheral Expressway: India’s First Smart And Green Highway

India’s first smart and green highway is a 135 km long KundliGhaziabad-Palwal (KGP) Expressway also known as Eastern peripheral Expressway (EPE). It consists of 14-lane highway with following features:

  1. Solar Power Plants: 8 nos. solar power plants, with capacity of 4,000 KW (4 megawatt) for lighting of underpasses and running solar pumps for watering plants.
    ii. Rainwater Harvesting: On both sides at every 500 metres and there is drip irrigation for plants all along the expressway
    iii. Closed Tolling System: Toll is collected with Electronic Toll Collection (ETC) system only for the distance travelled and not for the entire length
    iv. Weigh-In-Motion (WIMs) equipment: To stop entry of over-loaded vehicles, WIMs are installed at all 30 entry points
    v. Auto Challans: Over-speeding will be fined as cameras along the highway will capture speed of vehicles and issue autochallans
    vi. Intelligent Traffic Management: Smart and intelligent highway traffic management system (HTMS) and video incident detection system (VIDS) have been installed
    vii. Green Cover: Over 2.5 lakh trees have been planted with drip irrigation provision for irrigating these trees.

With The End In Mind

No matter what strategy and priority are used, the eventual goal is to meet the needs of the present without compromising the ability of future generations to meet their own needs. Sustainable and/or smart are no longer remaining options – these have become necessary considerations. At the project conceptualization stage itself, there is a need to look beyond the pavement life cycle, its assessment and rehabilitation. Designing for more than one life cycle of a pavement seems to be the future. While doing so, the application of smart materials, and monitoring technologies would form an integral part.

While both sustainable and smart are achievable, each needs to be contextualized and prioritized (for example, refer Table 3). Prior to this however, there is a need to undertake an honest assessment of the current state. Fig. 3 shows the sustainable – smart matrix. While the ideal desired state (IDS) is to have both sustainable and smart pavement infrastructure, the current state however might be exactly opposite. There could be many pathways to reach IDS. Prioritizing Sustainable over smart appears or vice versa are potentially two pathways – a balancing approach would serve the best.

Contextualizing Strategies

Firstly, India’s mix of road network provides a unique opportunity for having sustainable-smart balance. Fig. 3 indicates the road network break-up. Rural roads could be explored for sustainability in terms of use of local construction materials. Urban roads on the other hand would need an intelligent mix of sustainable and smart. This is primarily because of the utilities, access for construction and rehabilitation, decongestion priorities, land availability, multi-modal transportation systems, considerations for making cities sustainable and smart, etc. National highways on the other hand carry almost 40% of the traffic volume. Hence, building national highways in sustainable and smart ways is a priority.

Similarly, the strategies for urban roads would be quite different. Managing multi-utilities, drainage system management, faster repair strategies and methods, managing with multi-modal transportation system, contactless pavement monitoring systems, etc. would form the priorities. While in case of rural roads, use of local materials and technologies, increased use of supplementary cementitious materials, higher percentage of recycled products, etc.

Differentiating: Old And New

Secondly, India would have to address sustainable and smart pavement infrastructure for old and new pavement infrastructure. India had started building its ambitious highway infrastructure expansion plan about 20 years ago under its National Highways Development Program (NHDP) phase-I and II. Smart monitoring of existing pavements and sustainable rehabilitation and repair strategies or a combination could be prioritized.

Prioritizing Smart

While the word ‘smart’ may seem attractive, the strategies to achieve the same needs to be scrutinized and prioritized before applying. For example, a block of smart pavement wired with necessary gadgets could prove to be difficult during recycling concrete. Hence the trade-offs between different purposes needs to be properly understood.

Conclusion

Achieving sustainable and smart pavement infrastructure system is a long-term agenda needing prioritization, contextualization, and a balance between maintaining existing and creating new. How we realize these in phases with right trade-offs is far more important. While the possibilities are endless, complete realization of smart and sustainable needs some radical changes in terms of material selection, design methods, construction, and maintenance strategies. And we are running against time.

References

  1. Oxford Economics, Global Infrastructure Outlook, 2017
    2. World Economic Forum, The world is facing a 15 trillion infrastructure gap by 2040-Here is how to bridge it, 11 April, 2019, https://europeansting. com/2019/04/11/the-world-is-facing-a-15-trillion-infrastructure-gap-by2040-heres-how-to-bridge-it/
    3. MoRTH, T. (2019). Basic road statistics of India [2016/17]. New Delhi: MoRTH.
    4. Zietsman, J., T. Ramani, J. Potter, V. Reeder, and J. DeFlorio. 2011. A Guidebook for Sustainability Performance Measurement for Transportation Agencies. NCHRP Report 708. Transportation Research Board, Washington, DC
    5. Culshaw, B. (February 01, 1992). Smart Structures—a Concept or a Reality? Proceedings of the Institution of Mechanical Engineers, Part I: Journal of Systems and Control Engineering, 206, 1, 1-8.
    6. Suleman A., Prasad E., Blackow R., Waechter D. (2001) Smart Structures — an Overview. In: Suleman A. (eds) Smart Structures. International Centre for Mechanical Sciences (Courses and Lectures), vol 429. Springer, Vienna
    7. Careless, James, The possibilities are endless with smarter pavements, Asphalt, the magazine of Ashlatph institute, http://asphaltmagazine.com/ smarterpavements/
    8. CRISIL, Paving future roads for India, Dec 2019
    9. Forum of European National Highway Research Laboratories, NR2CNew Road Construction Concepts, April 2008, https://ec.europa.eu/transport/road_safety/sites/roadsafety/files/pdf/projects_sources/nr2c_final_ report.pdf

 

 

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