Sustainable Use of Recycled Glass in Pavement Systems

Featured Scientist: Saurabh (Mobi) Singh (he/him/his), Master of Business Administration 2017, Inactive M.S. student, Department of Technology, Illinois State University.

A picture of Saurabh standing in front of a construction site.
Mobi Singh at a construction site in Bloomington, IL

Birthplace: Jhajjar, Haryana, India

My Research: The research, led by Dr. Pranshoo Solanki, involved creating unique types of construction materials out of waste products like glass and rubber. The goal of the project was to support sustainability and help reduce pollution. The cement industry is one of the leading producers of greenhouse gases and our research can help the industry make sustainable and environment-friendly decisions.

Research Goals: Short term, I want to engage in research that challenges the status quo to help industries make choices that will make the world a cleaner and better place. Long term, I want to engage in research that will use innovative technologies to address child hunger. I am also interested in researching the role of privacy concerns and emotions in social media advertising at Kent State University in Ohio. 

Career Goals: I like to dream and try new things. There is no specific career path that fits all my skill sets but I wish to be a full-time scholar for the rest of my life. Being a university professor and helping other students grow intellectually is one of my long-term career goals. As I grow older, I would like to spend more time giving back to my community. In later years, I wish to support the costs of higher education for those who are not able to cover the costs themselves.

Hobbies: I enjoy travelling to other countries, cooking, meeting new people, and community service.

Favorite Thing About Science: Science is exciting because it shifts paradigms towards better methods and applications of knowledge.

Field of Study: Material Science

What is Material Science? Material science is the study of human-made materials. We study the chemical and physical properties of these materials and figure out how they can be used. For example, one practice could be to take recycled materials and see how they might be used in common household items.

My Team: The research was conducted in Turner Hall at Illinois State University. The research team was led by Dr. Pranshoo Solanki. The team had an external co-investigator named Dr. Gaurav Sancheti from Manipal University in India. I actively worked with Dr. Pranshoo Solanki in the construction management laboratory to test samples of concrete.

Check Out My Original Paper: “Sustainable Use of Waste Glass in Pavement Systems–Review, Limitations and Potential Application”

QR code that links to the original publication.
QR code to the original publication

Citation: Solanki, Pranshoo, Gaurav Sancheti, and Saurabh Singh. “Sustainable Use of Waste Glass in Pavement Systems–Review, Limitations and Potential Application.” The Journal of Solid Waste Technology and Management 47.2 (2021): 235-251.

Research At A Glance: The United States (U.S.) transportation sector is one of the main sources of greenhouse gas emissions and energy consumption in the U.S. According to the Environmental Protection Agency (EPA), the U.S. is the third largest producer of cement, and cement is the second most consumed substance in the world (after water). The cement industry is the third largest source of industrial pollution in the U.S. and is responsible for emitting more than 500,000 tons of greenhouse gases per year. Cement is one of the raw materials used to make pavement. As cement is a leading contributor of industrial pollution, it has become increasingly clear that our use of pavement has had a negative impact on the environment. As a result, many researchers have started to explore how recycled materials might be used in pavement. For example, usage of recycled glass in pavement has attracted a lot of interest as an alternative to current methods. According to the EPA, 11.5 million tons of glass is produced in the U.S. every year, but 60% of it ends up in landfills. However, when glass is finely ground, it can be used as a substitute for certain components of cement. In our paper, we reviewed potential uses of recycled glass as a pavement material and how the glass might affect the performance of the pavement. Overall, our study found that recycled glass could be used as a pavement material. This means that we could divert large amounts of glass headed to landfills to use as a construction materials.

Highlights: Fly ash has traditionally been used as a partial replacement for cement in many construction materials, like concrete and other controlled low strength pavement materials. Fly ash is a fine powder that is created as a by-product of coal power plants. There have been numerous closures of coal power plants in the past few decades, and this has disrupted the supply of fly ash to the construction industry. Recycled glass powder can be used in place of fly ash in pavement construction and can help to reduce the industry’s reliance on cement. Our study tested the feasibility of using recycled glass powder in lieu of fly ash

To test this, we substituted the fly ash in the cement with a specific type of recycled glass, called ACAS.  We then tested the material for its compressive strength. Compressive strength refers to the amount of pressure that a solid material can handle before it cracks. We also used glass of varying thickness to see if more finely ground or more coarsely ground glass would be best to improve the compressive strength of the pavement. The results in Figure 1 show that when 100% of the fly ash inside of the cement was replaced with finely ground glass, the compressive strength of the pavement improved the most.

Figure 1. This graph displays the results of experiments that tested the compressive strength of the samples. ACAS is a type of fine recycled glass and the three lines depict how the compressive strength varied with different blends of fine and coarse glass. The y-axis shows the compressive strength and the x-axis shows the percent of cement that was replaced with ACAS glass. Figure adapted from Solanki et al. 2021.

Next, we tested the material for its flow consistency. Flow consistency refers to the ability of freshly mixed concrete to flow into empty spaces before it sets. It is used to measure how much the low strength pavement materials flow naturally when they are used to fill trenches and pavements. Similar to the previous experiment, we replaced the fly ash inside of the cement with different amounts of finely or coarsely ground glass. The results in Figure 2 show that the flow consistency was highest when 50% of the fly ash was substituted with finely ground glass.

Figure 2. This graph displays the results of experiments that tested the flow consistency of the samples. The y-axis shows the flow consistency and the x-axis shows the percent of cement that was replaced with ACAS recycled glass. Figure adapted from Solanki et al. 2021.

What My Science Looks Like: In this paper, we suggest that recycled glass can be used as a replacement for fly ash in cement and we test the quality of the new material. In the image below, a sample of controlled low strength pavement material is being tested for its compressive strength.

An image of a cylinder piece of cement. The cement is between two metal pieces attached to an electrical source. The top of the machine pushed down to create force, which is measured to determine the compressive strength.
In this image, we test the cement for its compressive strength at the construction management lab at Illinois State University. The sample contains recycled glass powder in place of fly ash.

The Big Picture: Our research can help reduce pollution in many ways. We suggest alternatives to concrete and provide proof that these alternate materials are effective. We show that recycled glass can improve the properties of concrete. Glass can be a cost effective alternative for the transportation industry and we hope that the industry will adopt these new materials. We offer a green and cost effective alternatives to certain parts of cement and our goal is to reduce current levels of pollution.

Decoding the Language:

Compressive strength: Compressive strength can be defined as maximum compressive stress that a solid material can sustain before fracture.

Environmental Protection Agency (EPA): The EPA is a United States federal government agency whose mission is to protect human and environmental health.

Flow consistency: The flow consistency is a measure of the ability of freshly mixed concrete to flow into empty spaces before it sets.

Fly ash: Fly ash is a fine powder that is made from burning pulverized coal. It is used in concrete to improve workability, strength, and durability.

Greenhouse gas: Greenhouse gases, such as carbon dioxide and methane, trap heat inside the Earth’s atmosphere and can destabilize global weather patterns.

Low strength pavement materials: Low strength pavement materials have a lower concentration of cement as compared to regular pavement material.

United States (US) transportation sector: The US transportation sector is a subsector of the government that deals with all types of transportation, including roads, railways, air travel, and waterways.

Learn More:

United States EPA information on the health and environmental effects of cement

United States EPA information on coal ash

Synopsis edited by Ian Rines, BS 2018, Wofford College, Elyse McCormick, MS (Anticipated 2022), Illinois State University, and Rosario Marroquin-Flores, PhD (Anticipated 2022), Illinois State University.

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