Dr. Ambika Behl: Sustainable Road Engineering with Waste By-Products

In an exclusive interview with Maria R., Dr. Ambika Behl, Senior Principal Scientist - Flexible Pavements, CSIR-CRRI, shares her research-based innovations in road construction using waste by-products as sustainable solutions, the ensuing challenges, and the resultant achievements and accolades.

Dr. Behl, you’ve been recognized with several prestigious awards like the Bitumen India Award, Build India Infra Innovative Technology Award, the IRC Pt. Jawaharlal Nehru Birth Centenary Award (the first woman to receive this award in 2022), and many others. How did the accolades further motivate you to research on advancements in road construction practices in India?

As you mentioned, being the first woman to receive IRC Pt. Jawaharlal Nehru Birth Centenary Award will always be a cherished milestone for me. It was a moment of validation for my efforts in a sector where I initially faced significant resistance. Receiving appreciation and IRC recognition for my work in sustainable road construction technologies further motivated me to continue advocating for environmental considerations in the forefront of road construction in India.

Research on Waste Recycling and Utilization

Dr. Behl, your research has consistently focused on utilizing waste materials for road construction. What specific challenges and observations led you to recognize and explore the potential of waste materials in road infrastructure development?

My journey into exploring the potential of waste materials in road infrastructure development was driven by a combination of industry challenges, environmental concerns, and the need for sustainable solutions.

Conventional road construction relies heavily on natural resources like aggre- gates, bitumen, and cement, leading to resource depletion and environmental degradation. The high carbon footprint of construction activities called for innovative, eco-friendly alternatives.

Rapid urbanization and industrialization in India have led to an alarming increase in waste materials such as plastic, fly ash, construction and demolition (C&D) waste, and steel slag. Inefficient waste disposal methods contribute to pollution, landfills, and ecological damage.

When the idea of incorporating waste materials in road construction was first proposed, there was considerable scepticism about their long-term performance, durability, and safety. Overcoming industry resistance required extensive research, pilot projects, and proven case studies.

Observing successful international case studies on sustainable road technologies inspired me to explore how similar innovations could be adapted to India’s climatic and traffic conditions.

Policy shifts and government initiatives promoting circular economy principles and waste utilization in construction further reinforced the need for sustainable road-building solutions. Recognizing these challenges, I delved into research and development, exploring ways to integrate waste materials into road infrastructure without compromising quality, durability, or cost-effectiveness.

On Using Waste Plastics in Road Construction

You've been recognized for your significant contributions in using waste plastics in road construction. How do you evaluate the current state of incorporating waste plastics into infrastructure projects, and what improvements or innovations do you foresee in this area?

Waste plastics come in various types (e.g. PET, HDPE, LDPE, PVC), but only certain types (mainly LDPE and PP) are suitable for road construction. Proper segregation is critical to avoid contamination. Establishing efficient plastic waste collection and sorting systems can help to ensure effective utilisation of plastics in making durable roads.

The melting of plastics at high temperatures can release harmful gases and microplastics, raising concerns about environmental and health impacts. Using controlled processing techniques at optimal temperatures are required to minimize emissions and ensuring safe handling practices for workers.

While plastic roads have been successfully tested but large-scale implementation requires modifications in asphalt plants. Investing in technology upgrades for asphalt plants and incentivizing the use of plastic waste in government-funded road projects is required for large scale adoption.

Collecting, cleaning, shredding and processing plastic waste incurs costs, and the financial benefits of plastic roads need clearer validation. Government subsidies, tax incentives, and public-private partnerships can make plastic road technology more cost-effective and attractive for contractors. However, while incorporating waste plastics in road construction offers environmental and economic benefits, but some hurdles are there which must be addressed to ensure its effective implementation.

Bio-bitumen - A Groundbreaking Innovation

One of your groundbreaking innovations is the development of a process to produce bio-bitumen from the pyrolysis of rice straw. How do you see this technology reducing dependence on fossil-based materials like bitumen and lowering the carbon footprint of the construction industry?

Bio-bitumen technology has the potential to revolutionize the road construction industry by reducing dependence on fossil-based bitumen and significantly lowering the carbon footprint.

Traditional bitumen, derived from petroleum, contributes to greenhouse gas emissions and resource depletion. By utilizing biomass such as rice straw, wood waste, or algae, bio-bitumen decreases reliance on crude oil-based bitumen, promoting energy security.

The production process of bio-bitumen emits fewer greenhouse gases compared to conventional bitumen refining, contributing to climate change mitigation. Agricultural waste, like rice straw, is often burned, leading to air pollution. Converting it into biobitumen provides a sustainable disposal method while adding value to waste materials. Bio-bitumen supports a circular economy by repurposing organic waste into high-value infrastructure materials.

What challenges did you face in working with biomass like rice straw to produce bio-bitumen, and how did you overcome them during your research?

The biggest challenge in utilizing biomass like rice straw for Bio-bitumen production is Feedstock Variability & Quality Control. Biomass sources like rice straw have inconsistent chemical compositions depending on harvest conditions, affecting the quality of bio-bitumen. Strategic planning and standardized pre-processing techniques can be a potent solution to this challenge.

Another challenge is Efficient Biomass Conversion Process. Extracting bitumen-like substances from biomass requires advanced thermal and chemical processes, which need optimization for yield and quality. Our research is done and we have filed patent also on this developed technology. The next big challenge is Industry Acceptance & Regulatory Compliance.

Bio-bitumen technology is a promising step toward a more sustainable construction industry. Ongoing research and development efforts aim to further optimize production methods, improve cost-effectiveness, and facilitate widespread adoption.

My dream projects are achieving large-scale production of bio-bitumen and establish a comprehensive policy framework and guidelines for its use in road construction; develop guidelines for increased use of high RAP in highway construction from the current 30%; and construct self-healing highways in India, paving the way for more durable and cost-effective road networks.

Challenges in Implementing Large Scale Recycling

You’ve pioneered several technologies, including an indigenous recycling agent for hot mix recycling of pavements. What do you see as the biggest challenges to implementing large-scale recycling in road construction, particularly in a fast-growing infrastructure market like India? How can these challenges be overcome, and how do you envision the future of recycling in the sector?

While the benefits of recycling—such as reduced resource depletion, cost savings, and environmental sustainability—are well established, widespread adoption still faces hurdles due to the following challenges:

Engineers and policymakers are often concerned about the long-term durability and strength of recycled materials compared to virgin materials. The absence of well-defined standards and specifications for recycled materials leads to hesitation in their adoption by engineers and contractors.

Traditional road construction methods are deeply ingrained, and contractors may be reluctant to shift to new materials or processes. Many regions lack adequate recycling plants, equipment, and processing facilities. While recycling can be cost-effective in the long run, initial setup costs for recycling plants and equipment can be a deterrent.

Solutions lie in adopting the following: Developing national-level standards for using recycled aggregates, reclaimed asphalt pavement (RAP), and industrial byproducts can provide clarity and build confidence in their use. Awareness programs, incentives, and policy-driven mandates can encourage the use of recycled materials. Training programs for engineers and contractors will also help in knowledge transfer. Investments in mobile recycling units, decentralized processing plants, and public-private partnerships can accelerate infrastructure development for recycling. Government subsidies, tax benefits, and incentives for recycling initiatives can help offset initial investments and make it more financially attractive.

By addressing these challenges and leveraging emerging opportunities, India can lead the way in sustainable road construction, balancing infrastructure expansion with environmental responsibility.

Rewarding work on incorporating RAP

Your work on incorporating reclaimed asphalt pavement (RAP) and high percentages of recycled materials into road construction has been highly regarded. How can we ensure that using RAP doesn't compromise the quality and safety of road infrastructure projects?

Reclaimed Asphalt Pavement (RAP) is a valuable material for sustainable road construction, but its use must be carefully managed to ensure that it does not compromise quality of the asphalt mix and pavement performance. The key lies in proper material selection, processing, mix design optimization, and strict adherence to performance-based specifications.

With advancements in material science, mix design technology, and recycling infrastructure, RAP can be used extensively without compromising road quality. Smart pavements, AI-driven mix design optimizations, and enhanced RAP rejuvenation techniques will further improve durability, making RAP an essential component of sustainable infrastructure development. By following these best practices, we can maximize RAP’s environmental and economic benefits while ensuring safe, durable, and high-performing roads.

International collaborations are vital for advancing road construction technologies. By sharing knowledge and best practices, we can accelerate innovation and build more sustainable, smarter road networks globally.

Cross-Border Collaborations

Having presented your research at global platforms like the Australian Road Research Board and at REX FUELS Dubai, and receiving international accolades, how do you view the role of cross-border collaboration in advancing road construction technologies?

Please share instances where the exchange of ideas and research has led to fruitful collaborations between CSIR-CRRI and your international counterparts, particularly in the field of waste management.

Cross-border collaboration plays a pivotal role in accelerating innovation, enhancing sustainability, and improving the overall efficiency of road construction technologies. By exchanging knowledge, research partnerships, and technology transfer between nations, we can overcome common challenges and drive progress in the infrastructure sector. For example, India was the first country to work on waste plastic roads and CSIR-CRRI shared the technical know-how and benefits of this technology with many agencies outside India for waste plastic road technology and on steel slag road technology, which led to projects with international agencies.

I often engage in discussions with professionals working in the area of sustainable technologies in other countries which help me to learn from their successful policy frameworks, and accordingly I develop research plans and frameworks required for India. Countries with advanced road construction techniques should share their expertise with developing markets, as it will help in reducing the learning curve and enabling faster adoption of best practices.

In the coming years, global partnerships will be essential for building smarter, more resilient, and environmentally friendly road networks. By leveraging technological advancements and fostering international cooperation, we can create a more connected and sustainable future for road infrastructure worldwide.

Dream Projects and Targets

Dr. Behl, as a leading scientist in the field of sustainable road construction, what are your dream projects or key targets for the future? Are there any emerging materials, trends or technologies that you're particularly excited about, and how can they be integrated into mainstream construction practices?

My current dream project is to achieve large-scale production of bio-bitumen and establish a comprehensive policy framework and guidelines for its use in road construction. While the technology is still at the pilot stage, significant efforts are needed to bring it into mainstream adoption.

Another key objective is to develop guidelines for the increased use of high RAP in highway construction. In India, the current allowable RAP limit is 30%, whereas some countries have successfully implemented up to 80% and even 100% RAP in bituminous hot mix. Expanding RAP utilization can greatly enhance sustainability in road infrastructure.

Additionally, I am focused on advancing self-healing road technology. Having successfully completed lab-scale studies, our next goal is to construct a self-healing highway in India, paving the way for more durable and cost-effective road networks.

Embrace confidence, resilience, and continuous learning. In a field full of challenges, your expertise and perseverance will help you thrive, make an impact, and pave the way for future generations of innovators. Don’t wait for opportunities — create them.

Message for Aspiring Women Scientists and Engineers

As a successful woman in a male-dominated industry, what advice or message would you share with aspiring women scientists and engineers? What key qualities and skills should women focus on developing to excel in leadership roles and drive innovation within their fields?

I don't consider myself successful yet, as my journey is still ongoing toward that milestone. However, after spending nearly 20 years in the construction sector, I would like to share a few insights with the young women professionals aspiring to enter the Highway Infrastructure sector. My advice to them is to embrace confidence, resilience, and continuous learning. The infrastructure construction industry presents unique challenges, but with the right mindset and skills, you can thrive and make a significant impact. Challenges and biases will arise, but resilience will help you navigate obstacles and prove your worth.

Trust in your expertise and speak up in meetings, project discussions, and leadership conversations. Develop technical excellence. Stay updated with the latest engineering, construction, and project management advancements. Mastering your technical field will give you credibility and authority.

Take ownership of your career by seeking growth opportunities. If opportunities are not coming your way create them. The construction industry is evolving with technology, sustainable practices, and digital solutions, so be open to learning new tools, processes, and leadership strategies.

Who has been the most influential person in your career, and how did they shape your professional journey? What kind of legacy do you hope to leave for future generations of engineers and innovators?

When I began my journey in the road construction sector in 2007, I faced significant challenges, resistance, and criticism. During that time, our former Head of Department, Dr. Sunil Bose, encouraged me to pursue a PhD to gain the knowledge and expertise needed to excel in this field. He connected me with Prof. Satish Chandra at IIT Roorkee, under whose mentorship I learned the fundamentals of research and began presenting my work. This guidance and experience not only strengthened my technical skills but also instilled confidence in me and became the foundation for my professional growth.

I therefore aspire to be remembered as someone who not only contributed to engineering excellence but also championed positive change, mentorship, and the empowerment of future leaders in the field.

I wish to leave a legacy that inspires future generations of engineers and innovators to build a more sustainable, inclusive, and forward-thinking infrastructure industry. My goal is to pave the way for environmentally responsible engineering solutions, ensuring that sustainability becomes a fundamental pillar of road construction and infrastructure development.

Beyond technical advancements, I want to encourage a culture of diversity, resilience, and innovation—where women and underrepresented groups have equal opportunities to lead and make an impact.