Making roads from ash!

If Tushar Gupta, a research scholar with the IITB-Monash Research Academy, has his way, fly ash from coal-fired power plants will soon be used to help make roads stronger and greener.

The Academy is a Joint Venture between IIT Bombay and Monash University, and aims to enhance scientific collaborations between the two countries. Research scholars study for a dually-badged PhD from both institutions, enriching their research and building collaborative relationships by spending time in Australia and India over the course of their degree.

Tushar is working on a project titled ‘Fly ash utilisation in haul road construction in open cast coal mines: A geo-environmental and hydro-geological investigation’ under the supervision of Professor T N Singh and Dr Mohan Yellishetty.

“The world has developed an insatiable appetite for energy to meet its development needs,” he says, “and coal remains one of the biggest sources of energy. Hence it is imperative that the by-products of the coal production-combustion cycle like overburden, fly ash and carbon dioxide be mitigated effectively, economically and in an environmental-friendly way.”

Figure 1. Fly Ash and Bottom Ash from a Coal Power Plant Source

These by-products have a huge potential to pollute the environment. Based on the source of used coal, fly ash, which is the solid, unburnt remnant of coal combustion, can amount to anything from less than 5% to more than 40% of the total amount of coal burnt. In India, where the ash content of coal is relatively high, more than 180 million tonnes of fly ash is generated each year. Mitigation of such huge volumes is a big challenge; consecutively India is only able to use around 56% of the total amount, leaving the rest to be dumped in the open. This open dumping not only leads to wastage of precious land area, but also increases the air, water and soil pollution in the local region. Tushar recalls the working environment near his last job location, “The situation was really bad.” he says. “An area of almost 4 square km was wasted to store the ash. During summers, the visibility was not more than 10 metres near the (ash) pond due to dry fly ash suspended in surrounding air. The leaves of all the plants and shrubs were covered with fly ash. During the rains, you could not trust the safety of drinking water as it could have been contaminated by leachate from the ash pond.”

Satellite view of a 4 km2 ash pond at Sarni in Madhya Pradesh (Source: Google Maps)

Fortunately, scientists have recently discovered that fly ash exhibits a cement-like nature in the presence of an additional source of lime. This property, called the pozzolanic nature of fly ash, has caught the attention of the cement and construction industry. However, challenges such as huge amounts of generated ash, the cost associated with transportation, and the lack of effective and applicable research act as barriers. Tushar is trying to overcome these challenges by using high volumes of fly ash in haul road construction in opencast coal mines as well as to make economic construction support material in civil applications.

Increased workability of mixture with fly ash (left) and without fly ash (right). Source: circainfo.ca

“What’s most exciting is that we are using a waste product from the coal industry to create something that will make our planet more environment-friendly,” explains Tushar. “If we succeed in using fly ash effectively and efficiently, we will not only help curb pollution but also reduce the requirement of cement and timber in construction work.”

One of the major costs associated with the mining sector is the construction and maintenance of haul roads, which are practically the life-lines of mining operations. Traditionally, these haul roads are made out of overburden material (blasted waste rock), and their maintenance cost comprises a significant portion of mine economics. Using the fly ash composite synthesized from Tushar’s research will increase the structural strength of these roads at practically no extra cost. Since fly ash will be used in coal mines, the transportation cost will be negligible as most coal mines are strategically located near coal power plants. Therefore, Tushar’s research project also has immense potential to overcome the hurdles in bulk fly ash utilisation for a significantly beneficial end product.

High-strength testing of fly ash based composite being carried out in Monash and IITB Labs

Prof Murali Sastry, CEO of the IITB-Monash Research Academy, is closely following Tushar’s progress. “The Academy was conceived as a unique model for how two leading, globally focused academic organisations can come together in the spirit of collaboration to deliver solutions and outcomes to grand challenge research questions facing industry and society,” he says. “And what better example of this than the work being done by Tushar and his team?”

Tushar is now using by-products and wastes from other industries (such as polymeric wastes from the paint industry) along with the fly ash to enhance the composite’s properties in terms of resistance to weathering and other natural degradation. This will have a huge application in the civil and mining industries, as it can effectively replace construction materials like timber, simultaneously providing better resistance against elements. “The results are very promising.” Tushar says. “The polymeric composite synthesised here has exhibited much better results than traditional construction methods used today for mine haul roads. With further research, this composite can be used in varied aspects of mining and civil engineering. Due to the demonstrated results and uniqueness of this research, we have recently filed a patent for this material as well.”

So, when you go for a long drive in the not-too-distant future on a road that is strong, smooth, and green, you know whom to thank.

Research scholar: Tushar Gupta, IITB-Monash Research Academy

Project title: Fly ash utilization in haul road construction in open cast coal mines: A geo-environmental and hydro-geological investigation

Supervisors: Professor T N Singh from IIT-B; Dr Mohan Yellishetty from Monash University

Contact details: tushar18.iitb@iitb.ac.in

This story was written by Mr Krishna Warrier based on inputs from the research student, his supervisors and IITB-Monash Research Academy. Copyright IITB-Monash Research Academy.