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Waste Glass as Pozzolana

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Dr SB Hegde, Professor, Jain University and Visiting Professor, Pennsylvania State University, United States of America, gives a detailed account of the use of waste glass as Pozzolana, a sustainable solution for cement production, in a two-part article.

The increasing demand for cement, coupled with growing environmental concerns, has led to a search for alternative materials that can reduce the carbon footprint of cement production. Waste glass, a significant environmental concern itself, has emerged as a promising alternative due to its pozzolanic properties.
This paper delves into the concept of utilising waste glass as a pozzolanic material in cement production, highlighting its benefits, challenges and potential for sustainable development based on the research and development work carried out by the author. This is part one of the study; part two will be featured in the consecutive issue of the magazine.

Generation and Availability of Waste Glass
On a global scale, this only amounts to a recycling rate of less than 35 per cent. Worldwide, around 130 million tonnes (Mta) of glass are currently produced annually.
India alone produces three million tonnes of glass waste annually, of which only 35 per cent is recovered, and the rest often ends up in landfills or down cycled into construction material aggregates. Glass is found in municipal solid waste (MSW), primarily in the form of containers such as beer and soft drink bottles; wine and liquor bottles; and bottles and jars for food, cosmetics and other products. India is one of the largest consumers of glass in the world, and as a result, it also generates a significant amount of waste glass. Waste glass, also known as cullet, can come from various sources such as bottles, jars, containers, windows and other glass products.
The availability and generation of waste glass in India depend on several factors, including population, consumption patterns, recycling infrastructure and waste management practices. Glass waste can be generated from residential households, commercial establishments and industries as well as construction and demolition activities. In recent years, there has been growing awareness about the importance of recycling glass waste in India. Recycling glass has several environmental benefits, such as reducing the consumption of raw materials, saving energy and reducing landfill waste.

Infrastructural requirement
To effectively use waste glass as a pozzolanic material in a cement plant, certain facilities and processes can be implemented. Here are some key facilities that can be created:

  1. Glass Sorting and Preprocessing: A facility for sorting and preprocessing waste glass is essential to segregate glass by colour and removing contaminants such as paper, plastics and metals. Crushing or grinding equipment can be used to reduce the glass to a suitable particle size.
  2. Glass Storage and Handling: Adequate storage facilities should be established to store the sorted and processed glass. It is important to protect the glass from moisture and other environmental factors that can affect its quality.
  3. Glass Dosing System: A dosing system should be set up to accurately measure and control the amount of waste glass being added to the cement production process. This can involve automated feeders or other equipment to ensure a consistent and controlled addition of glass.
  4. Glass Grinding or Milling Equipment: Depending on the desired fineness of the waste glass, a grinding or milling unit may be required to further reduce the particle size. This equipment can include ball mills, vertical roller mills, or specialised glass grinding mills.
  5. Blending and Mixing Facilities: Cement plants typically have blending and mixing facilities where various supplementary cementitious materials, including waste glass, can be combined with other raw materials. This ensures homogeneity and uniformity in the cement production process.
  6. Quality Control and Testing: Facilities for quality control and testing should be in place to assess the chemical and physical properties of the waste glass, as well as the performance of the cementitious mixtures incorporating the glass. This can include laboratory testing equipment and personnel trained in relevant testing methods.
    It’s important to note that the specific facilities required may vary depending on the scale of the cement plant and the volume of waste glass being processed. Detailed engineering studies and consultations in cement production and waste management can help determine the optimal design and layout of these facilities within a cement plant. Additionally, it is advisable to comply with relevant environmental regulations and obtain any necessary permits or approvals from statutory bodies in that particular country for handling and using waste glass within the cement plant.

The Fineness of Waste Glass
When waste glass is used as a supplementary cementitious material in cement production, it is important to consider the fineness or particle size distribution of the glass. The fineness of waste glass affects its reactivity and compatibility with
cement, which can impact the performance of the cementitious mixture.
The specific fineness requirements for waste glass can vary depending on the specific application, the type of cement being used, and the desired properties of the final concrete or mortar. However, in general, the waste glass particles should be finely ground to ensure effective pozzolanic or latent hydraulic reactions with the cement.
Here are some common guidelines for the fineness of waste glass used in cement:
Particle Size Distribution: The waste glass particles should have a range of sizes to ensure good packing and fill the voids between cement particles. A typical particle size distribution for waste glass in cement applications is similar to that of cement, with a majority of particles passing through a 325 mesh (45 microns) sieve.
Blaine Fineness: The Blaine fineness test is often used to measure the specific surface area of cementitious materials. The waste glass should generally have a Blaine fineness similar to or higher than that of cement. Typical values can range from 300 to 500 m²/kg or higher, depending on the application.
Grinding or Milling: Waste glass may require grinding or milling processes to achieve the desired fineness. The grinding method can vary depending on the available equipment and the specific glass composition. Ball mills, vertical roller mills or specialised glass grinding equipment can be used.
Gradation Control: It is important to control the gradation of waste glass during the grinding process. A well-controlled gradation can improve the flowability and workability of the cementitious mixture.
It is worth noting that the precise fineness requirements may vary depending on the specific standards, specifications, or guidelines established by statutory bodies of the particular country.

Attributes of Waste Glass as Pozzolana
Based on research and development investigations the following avenues are investigated for utilisation of waste glass.
Pozzolanic Properties of Waste Glass: Pozzolanic materials, when combined with calcium hydroxide in the presence of water, react to form cementitious compounds. Waste glass, rich in amorphous silica, exhibits excellent pozzolanic properties. Through a process called pozzolanic reaction, waste glass can contribute to the strength, durability, and chemical resistance of cementitious materials.
Environmental Benefits: Incorporating waste glass as a pozzolanic material in cement production offers significant environmental advantages. Firstly, it reduces the need for virgin raw materials such as limestone, thus conserving natural resources. Additionally, it mitigates the environmental impact associated with glass waste disposal, diverting it from landfills or incineration.
Improved Concrete Performance: The use of waste glass as a pozzolanic material enhances the performance of concrete. Due to its pozzolanic activity, waste glass reacts with calcium hydroxide in the cement matrix, resulting in denser and more durable concrete. This leads to improved mechanical strength, reduced permeability, and increased resistance to chemical attack.
Supplementary Cementitious Material: Waste glass can be used as a supplementary cementitious material (SCM) in cement production. When properly ground and processed, waste glass can replace a portion of cement without compromising the desired concrete properties. This substitution not only reduces cement consumption but also lowers the carbon dioxide emissions associated with cement production.
Sustainable Development and Circular Economy: Utilising waste glass as a pozzolanic material aligns with the principles of sustainable development and the circular economy. It promotes resource efficiency, reduces waste generation, and contributes to a more sustainable construction industry. The integration of waste glass into cement production presents opportunities for collaboration between cement manufacturers, waste management companies, and regulatory bodies to develop innovative and eco-friendly solutions.

References

  1. Utilisation of Waste Glass Powder in Concrete by P. Manoj Kumar,
    K. Sreenivasulu, and M. Srinivasulu Reddy, International Journal of Innovative Research in Science, Engineering and Technology, 2013.
  2. Recycling of Waste Glass as a Partial Replacement for Fine Aggregate in Concrete Mix by W. A. Rahman, M. A. S. Al-gahtani,
    and M. A. K. El-Kourd, Journal of King Saud University – Engineering Sciences, 2010.
  3. Mechanical and Durability Properties of Concrete Containing Glass Powder as Partial Replacement of Cement by A. Shayan and R. Xu, Construction and Building Materials, 2004.
  4. Properties of Glass Concrete Containing Fine and Coarse Glass Aggregates by Z. Feng, S. Xie, and Y. Zhou, Journal of Materials in Civil Engineering, 2011.

ABOUT THE AUTHOR
Dr SB Hegde, Professor, Jain University and Visiting Professor, Pennsylvania State University, United States of America.

Concrete

We engineer smarter systems to reduce waste

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Naveen Kumar Sharma, AVP – Sales and Marketing, Toshniwal Industries, talks about redefining instrumentation with customised, digitally enabled solutions engineered for harsh plant environments.

For over six decades, Toshniwal Industries has played a pioneering role in advancing process instrumentation for Indian manufacturing. In this exclusive conversation with Kanika Mathur, Naveen Kumar Sharma, AVP – Sales & Marketing, explains how the company designs kiln and grinding plant solutions tailored to the unique demands of the cement industry. As plants transition to higher AFR use and smarter automation, Toshniwal’s technologies offer greater reliability, accuracy and predictive insight.

Tell us how are your process instruments and condition monitoring system customised for cement kilns and grinding plant operations?
Toshniwal is a company with a legacy of over 65 years, and our experience has taught us that cement kilns and grinding units are fundamentally different in their operational demands. As an Indian company, we understand the unique requirements of Indian cement manufacturers. We work closely with our customers, engage deeply with their technical teams, and study operational challenges in real-time.
Based on these insights, we customise our solutions for both kiln and grinding applications. This tailoring is not just at a product level, but at a solution level—engineering design, instrumentation logic, and process optimisation. Our primary objective, for both the industry and our customers, is to reduce yield loss. Every customisation we implement is driven by this goal. We engineer smarter systems to reduce waste, improve consistency and increase plant reliability.
Ultimately, our solutions are built on an understanding that cement manufacturers require robust, practical and maintainable instruments. We design with this mindset so plants can operate more efficiently, with better control and higher profitability.

With the rising use of AFR, how do your solutions support thermal zone reliability and process time?
Our solutions are built around four core parameters: energy efficiency, yield loss reduction, product quality and environmental responsibility. These pillars drive our engineering decisions and define how our technologies support cement plants, especially as they adopt alternative fuels and raw materials (AFR).
We strongly believe in energy conservation. Every product we offer—whether for thermal monitoring, kiln control or flame optimisation—is engineered to improve energy performance. Reducing yield loss is another principle deeply embedded in our solutions, because production interruptions and material losses directly affect plant profitability and clinker quality.
We are also highly conscious of the end-product quality delivered by our customers to their markets. Consistency in burning, heat transfer, and thermal profiling directly influences clinker characteristics, and our instruments help maintain this stability.
Lastly, and most importantly, we care about the environment. We want to leave a greener world for the next generation. This mindset aligns with India’s digitalisation movement, advocated by our Prime Minister. Digital technologies are crucial for optimising AFR use, process stability, emissions and kiln efficiency. We are proud to contribute to this transition.
By optimising flame patterns, energy use, and pollution, our solutions deliver direct and indirect savings. Plants benefit from lower operational losses, reduced maintenance, and improved reliability, especially in pyroprocessing zones.

Tell us how do you address harsh environment challenges in cement plants, say dust, temperature, etc. with your sensor and monitoring?
This is a very important question because cement plants, steel plants, and power plants operate in extremely harsh environments. There are two major categories of specifications that we must respect while designing solutions: technical specifications and environmental specifications. Technical specifications relate to performance accuracy, measurement integrity, responsiveness and process safety. Environmental specifications, on the other hand, relate to high temperatures, heavy dust, humidity, vibrations and corrosive atmospheres. Our solutions are engineered to withstand both. We customise sensors, housings, mounting mechanisms and protective systems so that our instruments operate at 100 per cent functionality in harsh conditions. We ensure that the plant experiences minimal downtime from our systems. That is our engineering philosophy—solutions must work reliably in real-world environments, not just in ideal laboratory conditions.

What retrofit pathways do you offer for older cement lines to upgrade measurement and monitoring systems and how is the Indian market responding?
Every solution we provide is scalable and digitally adaptable. Technology evolves rapidly, and our offerings evolve with it. When we upgrade instruments or monitoring systems, we design them to integrate with existing plant infrastructure, so customers do not have to rebuild everything from scratch. Once our solution is installed, software upgrades or performance improvements can often be deployed without major cost. This ensures that customers continue to benefit from ongoing technological advancements. The Indian market has responded positively to this approach. Plant operators appreciate solutions that are future-ready and dynamic rather than static. Scalability helps them maintain competitiveness, extend asset life, and move toward smart manufacturing with confidence.

So how is your organisation leveraging digital technologies in your instrumentation portfolio for cement plants?
Digitalisation is at the core of every product we manufacture. We stand firmly behind the digital movement, not only because it represents efficiency, but because it is the direction in which the Indian industrial ecosystem is evolving. We deploy machine-vision technologies, advanced inline monitoring systems, and solutions capable of visualising the
inside of the furnace. These systems help reduce downtime, enable predictive asset management and provide actionable analytics to customers. All our technologies communicate seamlessly with Level 1, Level 2, and Level 3 automation. This allows integration across SCADA, DCS, ERP, and cloud ecosystems. Digitalisation for us is not an add-on—it is foundational to how our instrumentation is built.

What are your key innovation priorities to help Indian cement plant producers hit harder, higher substitution rates, lower emissions and smarter processing?
Sustainability is a national priority, and we are committed to supporting it. Our current portfolio already helps improve efficiency, reduce emissions, and support alternative fuel integration. But our innovation roadmap goes further. We are now developing specialised productivity-oriented software modules that will provide proactive alerts—not just alarms triggered after a fault has occurred. These modules will leverage artificial intelligence and machine learning to detect patterns early. The intention is to help plant teams take corrective actions ahead of time, reducing yield loss and environmental impact. Instead of informing the plant that a disruption has happened, the system will indicate that a disruption will happen, giving operators time to prevent it. We believe that within the next 12 to 18 months, we will launch these predictive solutions in combination with our instrumentation. When implemented, they will significantly improve decision-making, process stability and environmental performance across the Indian cement sector.

– Kanika Mathur

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Concrete

India donates 225t of cement for Myanmar earthquake relief

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On 23 May 2025, the Indian Navy ship UMS Myitkyina arrived at Thilawa (MITT) port carrying 225 tonnes of cement provided by the Indian government to aid post-earthquake rebuilding efforts in Myanmar. As reported by the Global Light of Myanmar, a formal handover of 4500 50kg cement bags took place that afternoon. The Yangon Region authorities managed the loading of the cement onto trucks for distribution to the earthquake-affected zones.

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Reclamation of Used Oil for a Greener Future

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In this insightful article, KB Mathur, Founder and Director, Global Technical Services, explores how reclaiming used lubricants through advanced filtration and on-site testing can drive cost savings, enhance productivity, and support a greener industrial future. Read on to discover how oil regeneration is revolutionising sustainability in cement and core industries.

The core principle of the circular economy is to redefine the life cycle of materials and products. Unlike traditional linear models where waste from industrial production is dumped/discarded into the environment causing immense harm to the environment;the circular model seeks to keep materials literally in continuous circulation. This is achievedthrough processes cycle of reduction, regeneration, validating (testing) and reuse. Product once
validated as fit, this model ensures that products and materials are reintroduced into the production system, minimising waste. The result? Cleaner and greener manufacturing that fosters a more sustainable planet for future generations.

The current landscape of lubricants
Modern lubricants, typically derived from refined hydrocarbons, made from highly refined petroleum base stocks from crude oil. These play a critical role in maintaining the performance of machinery by reducing friction, enabling smooth operation, preventing damage and wear. However, most of these lubricants; derived from finite petroleum resources pose an environmental challenge once used and disposed of. As industries become increasingly conscious of their environmental impact, the paramount importance or focus is shifting towards reducing the carbon footprint and maximising the lifespan of lubricants; not just for environmental reasons but also to optimise operational costs.
During operations, lubricants often lose their efficacy and performance due to contamination and depletion of additives. When these oils reach their rejection limits (as they will now offer poor or bad lubrication) determined through laboratory testing, they are typically discarded contributing to environmental contamination and pollution.
But here lies an opportunity: Used lubricants can be regenerated and recharged, restoring them to their original performance level. This not only mitigates environmental pollution but also supports a circular economy by reducing waste and conserving resources.

Circular economy in lubricants
In the world of industrial machinery, lubricating oils while essential; are often misunderstood in terms of their life cycle. When oils are used in machinery, they don’t simply ‘DIE’. Instead, they become contaminated with moisture (water) and solid contaminants like dust, dirt, and wear debris. These contaminants degrade the oil’s effectiveness but do not render it completely unusable. Used lubricants can be regenerated via advanced filtration processes/systems and recharged with the use of performance enhancing additives hence restoring them. These oils are brought back to ‘As-New’ levels. This new fresher lubricating oil is formulated to carry out its specific job providing heightened lubrication and reliable performance of the assets with a view of improved machine condition. Hence, contributing to not just cost savings but leading to magnified productivity, and diminished environmental stress.

Save oil, save environment
At Global Technical Services (GTS), we specialise in the regeneration of hydraulic oils and gear oils used in plant operations. While we don’t recommend the regeneration of engine oils due to the complexity of contaminants and additives, our process ensures the continued utility of oils in other applications, offering both cost-saving and environmental benefits.

Regeneration process
Our regeneration plant employs state-of-the-art advanced contamination removal systems including fine and depth filters designed to remove dirt, wear particles, sludge, varnish, and water. Once contaminants are removed, the oil undergoes comprehensive testing to assess its physico-chemical properties and contamination levels. The test results indicate the status of the regenerated oil as compared to the fresh oil.
Depending upon the status the oil is further supplemented with high performance additives to bring it back to the desired specifications, under the guidance of an experienced lubrication technologist.
Contamination Removal ? Testing ? Additive Addition
(to be determined after testing in oil test laboratory)

The steps involved in this process are as follows:
1. Contamination removal: Using advanced filtration techniques to remove contaminants.
2. Testing: Assessing the oil’s properties to determine if it meets the required performance standards.
3. Additive addition: Based on testing results, performance-enhancing additives are added to restore the oil’s original characteristics.

On-site oil testing laboratories
The used oil from the machine passes through 5th generation fine filtration to be reclaimed as ‘New Oil’ and fit to use as per stringent industry standards.
To effectively implement circular economy principles in oil reclamation from used oil, establishing an on-site oil testing laboratory is crucial at any large plants or sites. Scientific testing methods ensure that regenerated oil meets the specifications required for optimal machine performance, making it suitable for reuse as ‘New Oil’ (within specified tolerances). Hence, it can be reused safely by reintroducing it in the machines.
The key parameters to be tested for regenerated hydraulic, gear and transmission oils (except Engine oils) include both physical and chemical characteristics of the lubricant:

  • Kinematic Viscosity
  • Flash Point
  • Total Acid Number
  • Moisture / Water Content
  • Oil Cleanliness
  • Elemental Analysis (Particulates, Additives and Contaminants)
  • Insoluble

The presence of an on-site laboratory is essential for making quick decisions; ensuring that test reports are available within 36 to 48 hours and this prevents potential mechanical issues/ failures from arising due to poor lubrication. This symbiotic and cyclic process helps not only reduce waste and conserve oil, but also contributes in achieving cost savings and playing a big role in green economy.

Conclusion
The future of industrial operations depends on sustainability, and reclaiming used lubricating oils plays a critical role in this transformation. Through 5th Generation Filtration processes, lubricants can be regenerated and restored to their original levels, contributing to both environmental preservation and economic efficiency.
What would happen if we didn’t recycle our lubricants? Let’s review the quadruple impacts as mentioned below:
1. Oil Conservation and Environmental Impact: Used lubricating oils after usage are normally burnt or sold to a vendor which can be misused leading to pollution. Regenerating oils rather than discarding prevents unnecessary waste and reduces the environmental footprint of the industry. It helps save invaluable resources, aligning with the principles of sustainability and the circular economy. All lubricating oils (except engine oils) can be regenerated and brought to the level of ‘As New Oils’.
2. Cost Reduction Impact: By extending the life of lubricants, industries can significantly cut down on operating costs associated with frequent oil changes, leading to considerable savings over time. Lubricating oils are expensive and saving of lubricants by the process of regeneration will overall be a game changer and highly economical to the core industries.
3. Timely Decisions Impact: Having an oil testing laboratory at site is of prime importance for getting test reports within 36 to 48 hours enabling quick decisions in critical matters that may
lead to complete shutdown of the invaluable asset/equipment.
4. Green Economy Impact: Oil Regeneration is a fundamental part of the green economy. Supporting industries in their efforts to reduce waste, conserve resources, and minimise pollution is ‘The Need of Our Times’.

About the author:
KB Mathur, Founder & Director, Global Technical Services, is a seasoned mechanical engineer with 56 years of experience in India’s oil industry and industrial reliability. He pioneered ‘Total Lubrication Management’ and has been serving the mining and cement sectors since 1999.

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