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Environmental Benefits of Using Waste Glass as Pozzolana

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Dr SB Hedge, Professor, Jain University and Visiting Professor, Pennsylvania State University, United States of America, discusses the environmental benefits of using waste glass as Pozzolana in this concluding part of the article.

Pozzolanic properties of waste glass refer to its ability to react with calcium hydroxide in the presence of water to form cementitious compounds. This reaction, known as the pozzolanic reaction, contributes to the strength and durability of cementitious materials.

Findings based on the investigation on the Pozzolanic properties
Here are some details on the pozzolanic properties of waste glass and examples of its usage:
Amorphous Silica Content: Waste glass typically contains a significant amount of amorphous silica, which is a key factor in its pozzolanic activity. Amorphous silica has a high
surface area, allowing it to react readily
with calcium hydroxide and form additional cementitious compounds.
Reactivity and Fineness: The reactivity of waste glass depends on factors such as its chemical composition, particle size distribution, and surface area. To enhance its pozzolanic reactivity, waste glass is often ground to a fine powder. Increased fineness improves the contact between waste glass particles and calcium hydroxide, facilitating the pozzolanic reaction.
Pozzolanic Reaction Products: When waste glass reacts with calcium hydroxide in the presence of water, it forms additional cementitious compounds, such as calcium silicate hydrate (C-S-H) gel. The C-S-H gel contributes to the strength and binding properties of the
cementitious matrix.

Examples of Usage
Partial cement replacement: Waste glass can be used as a partial replacement for cement in concrete production. Typically, a portion of the cement is substituted with finely ground waste glass powder. This reduces the overall cement content while maintaining or improving the mechanical properties and durability of the concrete.
Glass powder addition in concrete mixes: Waste glass powder can be directly added to concrete mixes as an additional pozzolanic material. It acts as a supplementary cementitious material (SCM) alongside other pozzolanic materials like fly ash or silica fume. This combination enhances the reactivity and overall performance of the concrete.
Glass aggregate in concrete: In addition to using waste glass as a pozzolanic material, it can also be used as a fine or coarse aggregate in concrete production. By incorporating waste glass aggregates, both the pozzolanic and aggregate properties of the glass are utilised. This approach enhances the sustainability of concrete while maintaining structural integrity.
Glass fibre reinforcement: Waste glass fibres can be used as reinforcement in cementitious composites. The glass fibres provide tensile strength and improve the overall performance of the concrete. This application is particularly useful in construction elements requiring enhanced durability and crack resistance.
Glass as pozzolanic additive in mortars: Waste glass can be used as a pozzolanic additive in mortar mixes. Mortars containing waste glass exhibit improved workability, increased strength and reduced permeability. This makes them suitable for applications such as plastering, masonry and tile adhesives.
Waste glass possesses pozzolanic properties due to its high amorphous silica content. By utilising waste glass as a pozzolanic material, its environmental impact can be reduced while enhancing the performance and sustainability of cementitious materials.
The examples provided demonstrate the versatile usage of waste glass in cement and concrete applications, contributing to a more sustainable construction industry.

Environmental Benefits
The utilisation of waste glass as a pozzolanic material in cement production offers significant environmental benefits. Here is a detailed account of these benefits:
Waste reduction and recycling: Waste glass, if not properly managed, poses a significant environmental challenge. By using waste glass as a pozzolanic material, it is diverted from landfills or incineration, reducing the need for new disposal sites and minimising the environmental impact associated with glass waste. Recycling waste glass as a pozzolana promotes a circular economy by converting it into a valuable resource.
Conservation of natural resources: The incorporation of waste glass in cement production reduces the need for virgin raw materials, such as limestone or silica. By substituting a portion of cement with waste glass, natural resources are conserved, including the energy and water required for extraction and processing of raw materials. This conservation helps in preserving natural ecosystems and reducing the overall ecological footprint.
Energy savings and emissions reduction: The production of cement is energy-intensive and contributes to greenhouse gas emissions, primarily carbon dioxide (CO2). By using waste glass as a pozzolanic material, the cement content in concrete is reduced, resulting in lower energy consumption and CO2 emissions during cement manufacturing. This reduction in energy usage and emissions contributes to mitigating climate change and achieving sustainability goals.
Reduced landfill space and leachate generation: When waste glass is disposed of in landfills, it occupies valuable space and can contribute to environmental concerns. Glass waste in landfills may also produce leachate, potentially contaminating soil and groundwater. Utilising waste glass as a pozzolanic material reduces
the amount of glass waste sent to landfills, alleviating the pressure on waste management infrastructure and minimising the associated environmental risks.
Improved air quality: Cement production is associated with the release of pollutants, including dust, particulate matter, and potentially harmful gases. By replacing a portion of cement with waste glass, the production of cementitious materials can be optimised. The use of waste glass as a pozzolana reduces the overall emissions of particulate matter and improves air quality in and around cement plants, promoting a healthier environment for nearby communities.
Enhanced durability and reduced maintenance: Concrete incorporating waste glass as a pozzolanic material exhibits improved durability and reduced permeability. This translates into longer service life for concrete structures, reduced maintenance requirements, and decreased need for repairs or replacements. By extending the life of concrete, the environmental impact associated with new construction projects is minimised.

Waste Glass Addition
The addition of waste glass to concrete can significantly improve its performance in several ways. Here are the key ways in which waste glass enhances the performance of concrete:

  1. Increased strength and durability: The incorporation of waste glass as a pozzolanic material in concrete leads to the formation of additional cementitious compounds. These compounds, such as calcium silicate hydrate (C-S-H) gel, contribute to the strength and durability of the concrete. The pozzolanic reaction between waste glass and calcium hydroxide results in denser and more compact concrete, improving its compressive and flexural strength.
  2. Reduced permeability: Concrete containing waste glass exhibits reduced permeability to water and other potentially harmful substances. The pozzolanic reaction of waste glass results in the formation of a refined pore structure within the concrete matrix. This refined pore structure restricts the movement of water and other aggressive agents, enhancing the concrete’s resistance to moisture ingress, chemical attack, and freeze-thaw damage.
  3. Enhanced chemical resistance: The pozzolanic reaction of waste glass in concrete leads to the formation of calcium silicate hydrate (C-S-H) gel, which provides improved chemical resistance. This resistance makes the concrete less susceptible to chemical degradation caused by substances such as sulphates, chlorides and acids.
    Concrete with waste glass as a pozzolanic material exhibits better long-term performance in aggressive environments.
  4. Improved workability and cohesion: The addition of waste glass as a pozzolanic material can enhance the workability and cohesion of concrete. Due to the fine particle size and pozzolanic nature of waste glass, it acts as a filler material, improving the packing and lubrication of the concrete mixture. This improved workability allows for easier placement, consolidation, and finishing of
    the concrete.
  5. Mitigation of alkali-silica reaction: Alkali-Silica Reaction (ASR) is a chemical reaction that can occur between certain reactive silica minerals in aggregates and the alkalis present in cement. This reaction can lead to expansive cracking and deterioration of concrete. Waste glass, being an inert material, can act as a mitigating agent for ASR by replacing some of the reactive silica in the concrete mix.
  6. Sustainability and eco-friendliness: In addition to performance improvements, the utilisation of waste glass in concrete contributes to sustainability and eco-friendliness. By incorporating waste glass as a pozzolanic material, the consumption of cement is reduced, resulting in CO2 emissions associated with cement production. This reduction in CO2 emissions aligns with environmental goals and contributes to a more sustainable construction industry.

Challenges and Considerations
The utilisation of waste glass as a pozzolanic material in cement production does pose some challenges. Proper processing and grinding of waste glass to achieve optimal fineness is crucial to ensure its reactivity. The potential presence of impurities in the waste glass, such as metals or contaminants, requires careful selection and pre-treatment. Additionally, the impact of incorporating waste glass on the fresh and hardened properties of concrete should be evaluated to ensure compatibility with specific project requirements.

Research and Industry Initiatives
Ongoing research and industry initiatives are focused on optimising the use of waste glass as a pozzolanic material. Studies explore various methods of processing and grinding waste glass to enhance its reactivity and maximise its utilisation. Additionally, there is a scope to investigate the influence of waste glass characteristics, such as particle size, composition and treatment, on the properties of concrete. These efforts aim to develop guidelines and standards for incorporating waste glass in cement production.

Conclusion
The use of waste glass as a pozzolanic material in cement production offers a sustainable solution to address environmental concerns associated with both waste glass disposal and cement manufacturing. By harnessing the pozzolanic properties of waste glass, cement producers can reduce their carbon footprint, enhance concrete performance, and contribute to a more circular economy.
The addition of waste glass as a pozzolanic material significantly enhances the performance of concrete. The improvements include increased strength and durability, reduced permeability, enhanced chemical resistance, improved workability and cohesion, mitigation of alkali-silica reaction and sustainability benefits. By embracing waste glass in concrete production, the construction industry can create more resilient and eco-friendly structures while effectively utilising a valuable waste material.
Further research, collaboration and implementation efforts are essential to fully exploit the potential of waste glass as a valuable resource.

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.

You can find part one in the August issue of Indian Cement Review.

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

Concrete

The primary high-power applications are fans and mills

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Alex Nazareth, Whole-time Director and CEO, Innomotics India, explains how plants can achieve both cost competitiveness and sustainability by lowering emissions, reducing downtime and planning for significant power savings.

As one of the most energy-intensive industries, cement manufacturing faces growing pressure to optimise power consumption, reduce emissions and improve operational reliability. Technology providers like Innomotics India are enabling this transformation by combining advanced motors, AI-driven digital solutions and intelligent monitoring systems that enhance process stability and reduce energy costs. From severe duty motors built for extreme kiln environments to DigiMine AI solutions that optimise pyro and mill operations, Alex Nazareth, Whole-time Director and CEO, Innomotics India, explains how the company is helping cement plants achieve measurable energy savings while moving closer to their sustainability goals.

How does your Energy Performance Contracting model typically reduce power consumption in cement plants—e.g., MWh saved?
Our artificial intelligence-based DigiMine AI Pyro and Mill solutions developed specifically for the cement industry, supports our customers in improving their process stability, productivity and process efficiency. In Pyro, this is achieved by optimising fuel consumption (Coal / AFR), reducing Specific Heat Consumption and reduction in emissions (CO2, SOx and NOx) through continuous monitoring of thermodynamics in pyro and recommending set-points of crucial parameters in advance for maintaining stable operations.
Within the mill, this is achieved by improving throughput, reduce energy / power consumption and maintaining stable operations on a continuous basis. Our ROI-based value proposition captures the project KPIs like reduction of coal usage, increase of AFR, reduction of specific heat consumption (Kcal / Kg), reduction of specific power consumption (KWH / tonne), reduction of emissions, etc., by a specific percentage. This gives clarity to our customers to understand the investment vis-à-vis savings and estimate the recovery time of their investment, which typically is achieved within one year of DigiMine AI Pyro and Mill solutions implementation.

What role do digitalisation and motor monitoring play in overall plant energy optimisation?
Motors are being used extensively in cement production, and their monitoring play crucial role in ensuring continuous operation of applications. The monitoring system can automatically generate alerts for any anomaly / abnormalities in motor parameters, which allows plant team to take corrective actions and avoid any major equipment damage and breakdown. The alerts help maintenance team to plan maintenance schedule and related activity efficiently. Centralised and organised data gives overview to the engineers for day-to-day activities. Cement is amongst the top energy intensive industries in comparison to other industries. Hence, it becomes critically important to optimise efficiency, productivity and up-time of plant equipment. Motor monitoring and digitalisation plays a vital role in it. Monitoring and control of multiple applications and areas
within the plant or multiple plants becomes possible with digitalisation.
Digitalisation adds a layer on top of OT systems, bringing machine and process data onto a single interface. This solves the challenges such as system silo, different communications protocol, databases and most importantly, creates a common definition and measurement to plant KPIs. Relevant stakeholders, such as engineers, head of departments and plant heads, can see accurate information, analyse it and make better decisions with appropriate timing. In doing so, plant teams can take proactive actions before machine breakdown, enable better coordination during maintenance activities while improving operational efficiency and productivity.
Further using latest technologies like Artificial Intelligence can even assist operators in running their plant with minimal requirement of human intervention, which allows operators to utilise their time in focusing on more critical topics like analysing data to identify further improvements in operation.

Which of your high-efficiency IEC low-voltage motors deliver the best energy savings for cement mills or fans?
Innomotics India offers a range of IEC-compliant low-voltage motors engineered to deliver superior performance and energy savings, particularly for applications such as cement mills, large fans, and blowers. Innomotics has the complete range of IE4 motors from 0.37kW to 1000kW to meet the demands of cement industry. The IE5 range is also available for specific requirements.

Can safe area motors operate safely and efficiently in cement kiln environments?
Yes, safe area motors are designed to operate reliably in these environments without the risk of overheating. These motors have ingress protection that prevents dust, moisture ingress and can withstand mechanical stress. These motors are available in IE3 / IE4 efficiency classes thereby ensuring lower energy consumption during continuous operation. These motors comply with relevant Indian as well as international standards.

How do your SD Severe Duty motors contribute to lower emissions and lower cost in heavy duty cement applications?
Severe duty motors enhances energy efficiency and durability in demanding cement applications, directly contributing to lower emissions and operational costs. With high-efficiency ratings (such as IE3 or better), they reduce power consumption, minimising CO2 output from energy use. Their robust design handles extreme heat, dust and vibration—common in cement environments—ensuring reliable performance and fewer energy losses.
These motors also lower the total cost of ownership by reducing downtime, maintenance and replacement frequency. Their extended service life and minimal performance degradation help cement plants meet sustainability targets, comply with emissions regulations and improve overall energy management—all while keeping production consistent and cost-effective.

What pump, fan or compressor drive upgrades have shown approximately 60 per cent energy savings in industrial settings and can be replicated in cement plants?
In the cement industry, the primary high-power applications are fans and mills. Among these, fans have the greatest potential for energy savings. Examples, the pre-heater fan, bag house fan, and cooler fans. When there are variations in airflow or the need to maintain a constant pressure in a process, using a variable speed drive (VSD) system is a more effective option for starting and controlling these fans. This adaptive approach can lead to significant energy savings. For instance, vanes and dampers can remain open while the variable frequency drive and motor system manage airflow regulation efficiently.

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Concrete

We conduct regular internal energy audits

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Shaping the future of low-carbon cement production involves integrating renewables, digitalisation and innovative technologies. Uma Suryam, SVP and Head Manufacturing – Northern Region, Nuvoco Vistas, gives us a detailed account of how.

In an industry where energy consumption can account for a significant portion of operating costs, cement manufacturers are under increasing pressure to adopt sustainable practices without compromising efficiency. Nuvoco Vistas has taken a decisive step in this direction, leveraging digitalisation, renewable energy and innovative technologies to drive energy efficiency across its operations. In this exclusive conversation, Uma Suryam, SVP and Head Manufacturing – Northern Region, Nuvoco Vistas, shares its approach to energy management, challenges of modernising brownfield plants and its long-term roadmap to align efficiency with India’s net-zero vision.

How has your company improved energy efficiency over the past five years?
Over the past five years, we have prioritised energy conservation by enhancing operational efficiency and scaling up renewable energy adoption. Through strategic fuel mix optimisation, deployment of cleaner technologies, and greater integration of renewables, we have steadily reduced our environmental footprint while meeting energy needs sustainably.
Technological upgrades across our plants have further strengthened efficiency. These include advanced process control systems, enhanced trend analysis, grinding media optimisation and the integration of solar-powered utilities. Importantly, grid integration at our key plants has delivered significant cost savings and streamlined energy management.
A notable milestone has been the expansion of our solar power capacity and Waste Heat Recovery Systems (WHRS). Our solar power capacity has grown from 1.5 MW in FY 2021–22 to 5.5 MW, while our WHRS capacity has increased from 44.7 MW to 49 MW, underscoring our commitment to sustainable energy solutions.

What technologies or practices have shown the highest energy-saving potential in cement production?
One of our most significant achievements in advancing energy efficiency has been the successful commissioning of a 132 KV Grid Integration Project, which unified three of our major manufacturing units under a single power network. This milestone, enabled by a dedicated transmission line and a state-of-the-art Line-In Line-Out (LILO) substation, has transformed our energy management and operational capabilities.
With this integration, we have substantially reduced our contract demand, eliminated power disruptions, and enhanced operational continuity. Supported by an optical fibre network for real-time communication and automation, this project stands as a testament to our innovation-led manufacturing excellence and underscores Nuvoco’s vision of building a safer, smarter, and sustainable world.

What role does digitalisation play in achieving energy efficiency in your operations?
Digitalisation plays a transformative role in driving energy efficiency across our operations. At Nuvoco, we are leveraging cutting-edge technologies and advanced digital tools to enhance productivity, optimise energy consumption and strengthen our commitment to sustainability and employee safety.
We are developing AI-enabled dashboards to optimise WHRS and kiln operations, ensuring maximum efficiency. Additionally, our advanced AI models evaluate multiple operational parameters — including fuel pricing, moisture content and energy output — to identify the most cost-effective fuel combinations in real time. These initiatives are enabling data-driven decision-making, improving operational excellence and reducing our environmental footprint.

What is your long-term strategy for aligning energy efficiency with decarbonisation goals?
As part of India’s climate action agenda, the cement sector has laid out a clear decarbonisation roadmap to achieve net-zero CO2 emissions by 2070. At Nuvoco, we view this as both a responsibility and an opportunity to redefine the future of sustainable construction. Our long-term strategy focuses on aligning energy efficiency with decarbonisation goals by embracing innovative technologies, alternative raw materials and renewable energy solutions.
We are making strategic investments to scale up solar power installations and enhance our renewable energy mix significantly by 2028. These initiatives are a key part of our broader vision to reduce Scope 2 emissions and strengthen our contribution to India’s net-zero journey, while continuing to deliver innovative and sustainable solutions to our customers.

How do you measure and benchmark energy performance across different plants?
We adopt a comprehensive approach to measure and benchmark energy performance across our plants. Key metrics include Specific Heat Consumption (kCal/kg of clinker) and Specific Power Consumption (kWh/tonne of cement), which are continuously tracked against Best Available Technology (BAT) benchmarks, industry peers and global standards such as the WBCSD-CSI and CII benchmarks.
To ensure consistency and drive improvements, we conduct regular internal energy audits, leverage real-time dashboards and implement robust KPI tracking systems. These tools enable us to compare performance across plants effectively, identify optimisation opportunities and set actionable targets for energy efficiency and sustainability.

What are the key challenges in adopting energy-efficient equipment in brownfield cement plants?
Adopting energy-efficient technologies in brownfield cement plants presents a unique set of challenges due to the constraints of working within existing infrastructure. Firstly, the high capital expenditure and relatively long payback periods often require careful evaluation before investments are made. Additionally, integrating new technologies with legacy equipment can be complex, requiring significant customisation to ensure seamless compatibility and performance.
Another major challenge is minimising production disruptions during installation. Since brownfield plants are already operational, upgrades must be planned meticulously to avoid affecting output. In many cases, space constraints in older facilities add to the difficulty of accommodating advanced equipment without compromising existing layouts.
At Nuvoco, we address these challenges through a phased implementation approach, detailed project planning and by fostering a culture of innovation and collaboration across our plants. This helps us balance operational continuity with our commitment to driving energy efficiency and sustainability.

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Concrete

Enlight Metals Supplies 3,200 Tonne of Steel for Navi Mumbai Airport

The airport is set to become Asia’s largest air connectivity hub.

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Enlight Metals has supplied 3,200 metric tonne of steel for the newly inaugurated Navi Mumbai International Airport, marking a major contribution to one of India’s largest infrastructure projects and reinforcing the company’s commitment to supporting national development.

The Navi Mumbai International Airport, developed under a Public-Private Partnership led by the Adani Group, was inaugurated today by Prime Minister Narendra Modi. The airport is set to become Asia’s largest air connectivity hub, enhancing regional connectivity, boosting economic growth, and expanding trade opportunities. Prime Minister Modi described the project as a “glimpse of Viksit Bharat,” highlighting its transformative impact on infrastructure and development in the region.

“The supply of 3,200 metric tonne of steel for this key project aligns with our focus on supporting critical infrastructure development through reliable and timely metal sourcing. Enlight Metals is committed to enhancing transparency and efficiency in the steel supply chain, contributing to projects integral to India’s growth objectives,” said Vedant Goel, Director, Enlight Metals.

Enlight Metals has implemented technology-driven solutions to strengthen supply chain efficiency, ensuring consistent availability of construction materials for large-scale projects nationwide. Its contribution to the Navi Mumbai International Airport underscores the company’s growing role in supporting India’s infrastructure development initiatives.

This milestone reflects Enlight Metals’ ongoing engagement in delivering quality materials and timely services for major national projects, further cementing its position as a reliable partner in India’s infrastructure sector

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