Dr SB Hegde, Professor, Jain College of Engineering and Technology, Hubli, and Visiting Professor, Pennsylvania State University, USA, helps us understand the red river formation in cement kiln operations, its causes, impacts and mitigation strategies.

Red river formation in cement kilns, where molten clinker flows uncontrollably in the cooler, is a costly problem for cement plants. The phenomenon not only affects clinker quality but also leads to significant operational disruptions, increased energy consumption and accelerated wear on kiln refractory bricks. Understanding the factors that cause red river formation and implementing strategies to prevent it are critical to maintaining operational efficiency and clinker quality.
This paper explores the causes of red river formation, the operational impacts it has on kiln performance, and the various mitigation strategies that cement plants can adopt. Additionally, safety considerations associated with the prevention and handling of red river formation are discussed, with practical insights from case studies of successful plant interventions in India and globally.

Causes of red river formation
Red river formation is primarily caused by improper kiln operations, including fluctuating kiln temperatures, oxygen levels, and cooler inefficiency. The following parameters are essential contributors:
Kiln temperature: Inconsistent temperature control in the kiln’s burning zone, often exceeding 1500°C, creates an imbalance between the solid and molten clinker phases, leading to red river formation. Maintaining temperatures within a more stable range of 1470-1490°C ensures that the clinker remains solid as it moves into the cooler.
Oxygen levels and CO concentrations: Oxygen levels above 2.5 per cent increase the risk of over-combustion, while elevated CO levels above 0.3 per cent indicate incomplete combustion, both contributing to excessive clinker melting. Optimising oxygen levels to 1.8-2.0 per cent minimises the risk.
Raw mix composition: The raw mix plays a vital role in clinker formation. A high liquid phase due to improper ratios of silica, alumina, and iron oxide can lead to excessive melting. Controlling the silica modulus (SM: 2.3-2.7) and alumina modulus (AM: 1.3-1.8) ensures a more stable clinker and reduces the risk of red river formation. If the raw mix is improperly proportioned, red river formation becomes more likely due to high fluxing compounds that melt at lower temperatures.
Kiln speed and torque: Kiln speeds that fluctuate below 3.4 rpm can cause material buildup, while kiln torque exceeding 50-60 per cent indicates stress that can lead to clinker instability.
Cooler efficiency: Inefficiencies in the clinker cooler, with efficiency levels below 78 per cent, can exacerbate red river formation. Clinker that is not cooled properly will remain molten for longer, allowing it to flow uncontrollably. Coolers should maintain exit temperatures between 180-200°C to prevent red river incidents.
Impact on clinker quality and kiln performance
The occurrence of red river has numerous negative impacts on both clinker quality and kiln performance:
Clinker quality: Red river formation results in poor clinker grindability, higher variability in free lime content and inconsistent cement properties. Poor clinker reactivity reduces both early and late strength development in the final cement product.
Increased heat consumption: Red river typically increases specific heat consumption by 3-5 per cent, resulting in higher fuel usage. These inefficiencies can significantly affect the plant’s cost structure, driving up operational expenses.
Refractory damage: The molten clinker accelerates the wear of refractory bricks in the kiln, especially in the burning zone and cooler transition areas. Brick life can decrease by 25-30 per cent, leading to more frequent replacements and higher maintenance costs.
Equipment and instrumentation damage: The uncontrolled molten flow of clinker during red river incidents can damage cooler plates, kiln discharge systems, and even temperature sensors and thermocouples, leading to costly repairs and prolonged downtime.

Mitigation strategies
Mitigating red river formation requires a multi-faceted approach combining operational optimisation, automation and staff training:
Kiln temperature control: Maintaining stable burning zone temperatures in the 1470-1490°C range is key to preventing excessive melting of clinker. Advanced temperature monitoring systems can help regulate temperature fluctuations.
Cooler efficiency optimisation: To ensure proper cooling, cooler efficiency must be maintained at 78-80 per cent, with clinker exit temperatures not exceeding 200°C. Real-time airflow adjustments in grate coolers improve cooling performance, solidifying the clinker at the appropriate stage.
Automation and data analytics: Advanced Process Control (APC) systems using data analytics can monitor critical kiln parameters—such as temperature, oxygen levels, and torque—in real-time, allowing for predictive maintenance and early intervention when red river signs appear. This technology has been implemented successfully in leading plants globally to prevent red river formation.

Indian case studies
Case Study 1: Cement Plant in South India – Optimisation of Kiln Parameters
A cement plant in South India faced recurrent red river issues due to high kiln temperatures and low cooler efficiency. After comprehensive process audits, the plant optimised its kiln temperature to 1480°C, reduced oxygen levels to 1.9 per cent, and upgraded its cooler to an efficiency of 80 per cent. These changes reduced red river incidents by 85 per cent, saving the plant Rs 10 million in energy costs annually and improving clinker quality by
15 per cent.

Case Study 2: Cement Plant in North India – Cooler Upgrade and Automation
A northern India plant increased cooler efficiency from 70 per cent to 78 per cent by installing an advanced grate cooler. This reduced clinker exit temperatures to 190°C, preventing red river formation. Automation systems provided real-time adjustments, decreasing the frequency of incidents by 75 per cent and saving `12 million annually.

Global Case Studies
Case Study 1: European Plant – Automation Success
A German cement plant, experiencing red river issues due to fluctuating oxygen levels, installed an advanced data-driven automation system. The system stabilised oxygen at 1.9 per cent and maintained kiln temperature at 1,475-1,485°C, reducing red river by 90 per cent. Clinker quality improved by 10 per cent, with a reduction in specific heat consumption by 4 per cent.

Case study 2: US Plant – Operator Training and Process Optimisation
A US cement plant reduced red river occurrences by 70 per cent through kiln speed optimisation (3.8 rpm) and comprehensive operator training. Improved monitoring of kiln torque and cooler exit temperatures led to higher cooler efficiency (75 per cent) and an annual savings of $2 million.

Safety Aspects
Safety is a paramount concern in red river incidents. When molten clinker flows uncontrollably, it poses a significant risk to personnel working near the kiln and cooler areas.

To mitigate these risks:

• Clearance zones: Kiln and cooler areas should have strict clearance zones for personnel when red river incidents are detected.
• Protective gear and training: Personnel should be equipped with proper protective equipment (PPEs) and trained to handle emergencies involving molten clinker. Emergency shutdown procedures should be well-documented and rehearsed.
• Automation and early warning systems: Automation can provide early warning systems that alert operators to potential red river formation before it becomes critical, ensuring safe intervention.

Conclusion
Red river formation remains a major operational challenge for cement plants, but it can be effectively mitigated through proper kiln temperature control, cooler efficiency optimisation and the use of advanced automation systems.
The case studies highlight the importance of process improvements and staff training in reducing red river occurrences, improving clinker quality, and lowering operational costs. Additionally, safety
measures must be prioritised to protect personnel from the risks posed by molten clinker. By incorporating these strategies, cement plants can ensure consistent kiln performance and enhanced operational efficiency.

References
1. Duda, W. H. (1985). Cement Data Book. International Process Engineering in the Cement Industry. Bauverlag GmbH.
2. Javed, I., & Sobolev, K. (2020). “Use of Automation in Modern Cement Plants.” Cement and Concrete Research, 130, 105967.
3. Tamilselvan, P., & Kumar, R. (2023). “Optimisation of Kiln and Cooler Systems in Indian Cement Plants.” Indian Cement Review, 34(7), 42-48.
4. Martin, L. (2019). “Case Studies of Red River Mitigation in European Cement Plants.” International Journal of Cement Production, 12(2), 63-78.
5. Schorr, H. (2021). “Advanced Process Control in Cement Manufacturing.” Cement International, 19(3), 30-37.
6. Singh, V. K., & Gupta, A. (2022). “Impact of Raw Mix on Clinker Formation and Kiln Operations.” Global Cement Magazine, 14(4), 22-29.

About the author: Dr SB Hegde brings over thirty years of leadership experience in the cement industry in India and internationally. He has published over 198 research papers and holds six patents, with four more filed in the USA in 2023. His advisory roles extend to multinational cement companies globally and a governmental Think Tank, contributing to research and policy. Recognised for his contributions, he received the ‘Global Visionary Award’ in 2020 from the Gujarat Chambers of Commerce and Industry.

Vimal Joshi, Assistant General Manager – Quality Control, Wonder Cement, discusses how use of SCMs reduces reliance on clinker while supporting circular economy, creating long-lasting, high-quality infrastructure.

What role do supplementary cementitious materials (SCMs) play in enhancing the performance and sustainability of cement and concrete?
SCMs play a crucial role in enhancing both the performance and sustainability of cement and concrete. By replacing a portion of traditional Portland cement with materials like fly ash, slag and silica fume, we significantly improve the durability, strength and workability of concrete. SCMs react chemically with the calcium hydroxide released during hydration, forming additional calcium silicate hydrate (C-S-H), which enhances the concrete’s long-term strength.
Beyond performance, SCMs also contribute to sustainability by reducing the carbon footprint associated with cement production. By using industrial by-products as raw materials, we reduce the need for energy-intensive clinker production and divert waste from landfills, contributing to an eco-friendlier construction process.
SCMs not only improve the technical properties of cement but also support the broader goals of reducing greenhouse gas emissions and promoting resource efficiency.

How has your company integrated SCMs into its production process, and what challenges have you encountered?
We have successfully integrated SCMs into our production process, making them a key component of our sustainability strategy. We incorporate fly ash, and Performance Improver Limestone to replace a portion of the clinker in our cement, thus lowering our carbon emissions and enhancing product performance. However, the integration of SCMs has presented some challenges, primarily in terms of supply consistency and quality control (such as high moisture content and presence of foreign material in coal fly ash). Since SCMs are industrial by-products, their availability and composition can vary, which requires rigorous quality checks and adjustments to the production process.
Another challenge is achieving the right balance in the cement mix to ensure optimal strength and durability while maximising SCM content. Despite these challenges, we remain committed to increasing the use of SCMs and have developed strong partnerships with suppliers to ensure a reliable and consistent supply of high-quality materials.
Apart from fly ash and performance improvers we are using iron sludge (0.3 per cent to 0.8 per cent) as a substitute for laterite and red mud (1 to 2 per cent) as a substitute for bauxite in the manufacture of clinker without compromising on quality. Both materials are by products of industries with low SiO2 and high R2O3 content (addition of oxides), which helps reduce additive consumption in the raw mix (conserving natural resources) and reduces LSF requirement in stock pile preparation and thus, helping in increasing the available limestone reserves (conservation of natural resources).
We are using chemical gypsum and bed ash gypsum as substitutes to mineral gypsum in cement grinding, both are by-products of the industries that have high purity, which helps in preserving the natural gypsum and also increases the strength of cement and concrete.

Can you share insights on how SCMs such as fly ash, slag, and silica fume impact the durability and strength of concrete in different environmental conditions?
SCMs like fly ash, slag and silica fume significantly enhance the durability and strength of concrete, particularly under diverse environmental conditions. Fly ash improves workability and extends the setting time, making it ideal for mass concrete projects and hot climates. The fine particles fill voids in the cement matrix, reducing permeability and enhancing resistance to sulphate and chloride attack, thus increasing durability. Slag, with its slow hydration properties, improves long-term strength and is particularly effective in reducing thermal cracking in massive concrete structures. It also enhances resistance to aggressive chemicals, making it suitable for marine environments and industrial applications.
Silica fume, known for its ultrafine particles, increases the density of concrete, boosting both compressive strength and durability, especially in harsh environments. By incorporating SCMs, we create concrete that is more resilient to environmental stressors, ensuring longer-lasting structures with reduced maintenance needs.

With the global push for sustainability, how do SCMs contribute to reducing the carbon footprint of cement production?
SCMs play a pivotal role in reducing the carbon footprint of cement production, aligning with the global drive for sustainability. By substituting a portion of clinker, the most energy-intensive component of cement, with SCMs like fly ash and slag, we lower CO2 emissions from the production process. Each tonne of clinker replaced by SCMs reduces the need for limestone calcination, a major source of carbon emissions. SCMs are often industrial by-products, so their use in cement also promotes waste recycling, contributing to the circular economy.
Furthermore, SCMs typically require less energy to process than clinker, resulting in lower overall energy consumption. This shift towards utilising SCMs supports our broader sustainability goals, helping Wonder Cement meet both regulatory requirements and industry benchmarks for environmental responsibility, while providing
high-quality cement products that meet modern construction needs.

What strategies or innovations has your company adopted to ensure a consistent and reliable supply of SCMs, given their reliance on industrial by-products?
To ensure a consistent and reliable supply of SCMs, Wonder Cement has adopted several strategies and innovations. First, we have established long-term partnerships with key industries, such as thermal power plants, to secure a steady supply of fly ash. This collaboration ensures that we can maintain the quality and availability of SCMs despite potential fluctuations in production volumes. Additionally, we have invested in logistics and storage infrastructure to manage the seasonal and location variability of SCMs, allowing us to store and distribute materials as needed.
Another innovation involves the diversification of SCM sources, exploring options like rice husk ash, silica fume, granulated slag, copper slag, steel slag, lead zinc slag and ground granulated blast furnace slag. We also engage in research and development to optimise the performance of SCMs, ensuring that even with variability, the final cement product consistently meets our quality standards. These strategies ensure that we can reliably integrate SCMs into our production process.

Are there specific projects where SCMs have delivered outstanding results in terms of performance or sustainability?
SCMs have delivered outstanding results in various projects undertaken by Wonder Cement, particularly in terms of performance and sustainability. One notable example is our use of SCMs in large infrastructure projects such as bridges, dams and highways, where durability and long-term performance are crucial.
The incorporation of fly ash and performance improvers in these projects has enhanced concrete’s resistance to cracking, sulphate attack and chloride-induced corrosion, ensuring structural longevity.
In terms of sustainability, SCMs have been integral to our low-carbon cement mixes, which have been used in green building projects aimed at reducing the overall environmental footprint. These eco-friendly cement products have not only met but exceeded performance expectations, while significantly cutting down on carbon emissions during production.
By utilising SCMs, we have successfully delivered projects that align with both performance standards and sustainability goals, providing long-lasting, high-quality infrastructure with reduced environmental impact.

How does the use of SCMs align with your company’s broader goals around circular economy and resource efficiency?
The use of SCMs at Wonder Cement aligns perfectly with our broader goals of promoting the circular economy and enhancing resource efficiency. SCMs are typically industrial by-products like fly ash from power plants and performance improver from our own mines, and by incorporating these materials into our cement production, we help close the resource loop. This approach reduces the need for virgin raw materials, lowers waste sent to landfills, and minimises the environmental footprint of our operations. It also enables us to reduce the clinker factor in cement, which is the most carbon-intensive component, thereby contributing to lower CO2 emissions.
Additionally, the use of SCMs extends the life cycle of concrete products, reducing the need for repairs and replacements. This aligns with our commitment to sustainable development, resource optimisation, and supporting the global transition towards more circular, low-waste industrial practices.

What future trends do you foresee in the use of SCMs within the cement industry?
The future of SCMs in the cement industry looks promising, with several key trends likely to shape their development. One trend is the increasing diversification of SCM sources, as industries explore new by-products like rice husk ash, volcanic ash and even recycled construction materials as viable alternatives to traditional fly ash and slag. Another development is the refinement of SCM processing technologies, allowing for more consistent quality and higher substitution rates of clinker without compromising cement performance.
As sustainability continues to drive innovation, we foresee a growing demand for low-carbon cement products, with SCMs playing a critical role in meeting regulatory and market expectations for green construction materials. Additionally, advancements in carbon capture and storage (CCS) technologies could complement the use of SCMs, further reducing the carbon footprint of cement production.
Wonder Cement is keen to stay at the forefront of these trends, continuously evolving our use of SCMs to meet future industry demands.

– Kanika Mathur

As the cement industry prioritises sustainability and performance, Supplementary Cementitious Materials (SCMs) are redefining standards, explains Tushar Khandhadia, General Manager – Production, Udaipur Cement Works.

What role do supplementary cementitious materials (SCMs) play in enhancing the performance and sustainability of cement and concrete?
SCMs play a crucial role in enhancing the performance and sustainability of cement and concrete. These materials are added to concrete to improve its properties such as strength, durability, and workability, as well as to reduce the environmental impact of cement production. The addition of SCMs to cement reduces the amount of Portland cement required to manufacture concrete, reducing the carbon footprint of the concrete. These materials are often industrial waste products or by-products that can be used as a replacement for cement, such as fly ash, slag and silica fume.
SCMs also reduce the amount of water required to produce concrete, which reduces the environmental impact of concrete production. This is achieved through their ability to improve the workability of concrete, allowing the same amount of work to be done with less water.
In addition, SCMs improve the durability of concrete by reducing the risk of cracking and improving resistance to chemical attack and other forms of degradation.

How has your company integrated SCMs into its production process, and what challenges have you encountered?
The integration of SCMs into cement and concrete production may pose certain challenges in the areas of sourcing, handling and production optimisation.

• Sourcing: Finding an adequate and reliable supply of SCMs can be a challenge. Some SCMs, such as fly ash and slag, are readily available by-products of other industrial processes, while others such as silica fume or metakaolin may be more difficult to source.
• Handling: The storage, handling, and transportation of SCMs require special considerations due to their physical and chemical properties. For instance, some SCMs are stored in moist conditions to prevent them from drying out and becoming airborne, which could pose a safety risk to workers.
• Production optimisation: The addition of SCMs into the mix may require adjustments to the production process to achieve the desired properties of cement and concrete. For example, the use of SCMs may affect the setting time, workability, strength gain, and other properties of the final product, which may require reconfiguration of the production process.
• Quality control: The addition of SCMs may introduce variability in the properties of cement and concrete, and rigorous quality control measures are necessary to ensure the final product meets the required specifications and standards.

Proper planning, handling and production optimisation are essential in overcoming the challenges encountered during the integration process.

Can you share insights on how SCMs such as fly ash, slag and silica fume impact the durability and strength of concrete in different environmental conditions?

• Fly ash is a by-product of coal combustion and is widely used as an SCM in the production of concrete. When added to concrete, fly ash reacts with the calcium hydroxide present in the concrete to form additional cementitious materials, resulting in improved strength and durability. Fly ash increases the durability of concrete by improving its resistance to sulphate and acid attacks, reducing shrinkage and decreasing the permeability of concrete. Fly ash also enhances the workability and pumpability of concrete while reducing the heat of hydration, which reduces the risk of thermal cracking. In cold climates, fly ash helps to reduce the risk of freeze-thaw damage.
• Slag is a by-product of steel production and is used as an SCM because of its high silica and alumina content. When added to concrete, slag reacts with the calcium hydroxide present in the concrete to form additional cementitious materials, resulting in improved strength and durability. Slag increases the durability of concrete by improving its resistance to sulphate and acid attacks, reducing shrinkage and improving the strength of concrete over time. Slag also enhances the workability of concrete, reduces the heat of hydration, and improves the resistance of concrete to chloride penetration.
• Silica fume is a by-product of the production of silicon and ferrosilicon alloys and is used as an SCM because of its high silica content. When added to concrete, silica fumes react with the calcium hydroxide present in the concrete to form additional cementitious materials, resulting in improved strength and durability. Silica fume increases the durability of concrete by improving its resistance to sulphate and acid attacks, reducing permeability, and improving abrasion resistance. Silica fume also enhances the workability of concrete, reduces the heat of hydration, and improves the resistance of concrete to chloride penetration.

Overall, the use of SCMs such as fly ash, slag and silica fume can significantly improve the durability and strength of concrete in different environmental conditions. Their impact on concrete varies depending on the availability, physical and chemical properties of the specific SCM being used and proper testing and engineering analysis should be done for each mix design in order to optimise the final product.

With the global push for sustainability, how do SCMs contribute to reducing the carbon footprint of cement production?
SCMs provide an environmentally friendly alternative to traditional Portland cement by reducing the amount of clinker required to produce cement. Clinker is the main ingredient in Portland cement and is produced by heating limestone and other raw materials to high temperatures, which releases significant GHG emissions. Thus, by using SCMs, less clinker is required, thereby reducing GHG emissions, energy use and the environmental impact of cement production. Some SCMs such as fly ash and slag are by-products of other industrial processes, meaning that their use in cement production reduces waste and enhances resource efficiency. Moreover, the use of SCMs can enhance the properties of concrete, thereby increasing its durability and service life which helps to further reduce the overall embodied carbon of the structure.
In short, the use of SCMs contributes to reducing the carbon footprint of cement production by improving the efficiency of resource utilisation and reducing greenhouse gas (GHG) emissions during the production process. This has led to an increased demand for SCMs in the construction industry, as environmental concerns and sustainable development goals have become more prominent factors in the selection of building materials.

What strategies or innovations has your company adopted to ensure a consistent and reliable supply of SCMs, given their reliance on industrial by-products?

• Developing partnerships with suppliers: Many cement and concrete manufacturers establish long-term partnerships with suppliers of SCMs. These partnerships provide a reliable supply of high-quality SCMs, improve supply chain efficiency, and often provide access to new sources of SCMs.
• Advanced SCM processing techniques: Many companies are investing in advanced processing techniques to unlock new sources of high-quality SCMs. Advanced processing techniques include new separation processes, calcination techniques, and chemical activation methods.
• Alternative SCM sources: Many companies are exploring alternative SCM sources to supplement or replace traditional SCMs. Examples include agricultural by-products such as rice hull ash or sugar cane bagasse ash, which can be used in place of fly ash.
• Quality control measures: Strict quality control measures are necessary to ensure consistent quality of SCMs. Many companies use advanced testing methods, such as particle size analysis, chemical analysis, and performance testing, to validate the quality of SCM materials used in production.
• Supply chain diversification: Diversifying suppliers and SCM sources is another way to ensure a reliable supply. This reduces the risk of supply chain disruptions caused by factors such as natural disasters, market changes, or geopolitical risks.

The strategies and innovations adopted to ensure a consistent and reliable supply of SCMs include establishing long-term partnerships with suppliers, investing in advanced processing techniques, exploring alternative SCM sources, implementing strict quality control measures, and diversifying supply chains. By implementing these approaches, we ensure that use of SCMs in cement production is an effective and viable solution for reducing the environmental impact of operations

How does the use of SCMs align with your company’s broader goals around circular economy and resource efficiency?
Here are some ways in which the use of SCMs supports these goals:

• Reducing waste: The use of SCMs, such as fly ash and slag, diverts significant quantities of industrial waste from landfills, turning it into a valuable resource that can be used in construction. This helps to reduce waste and conserve natural resources.
• Reducing carbon emissions: Cement production is a significant contributor to greenhouse gas emissions, and the use of SCMs can significantly reduce the amount of cement required in concrete mixtures. This helps to reduce the carbon footprint of construction activities and move towards a low-carbon economy.
• Enhancing resource efficiency: The use of SCMs can reduce the demand for raw materials, energy, and water in the production of concrete. This not only conserves natural resources but also reduces the costs associated with the extraction, transportation and processing of these materials.
• Closing the loop: SCMs encourage closed-loop systems in the construction sector, where waste materials from one process become input materials for another. This can improve the efficiency and sustainability of the construction industry.
• Supporting sustainable design practices: The use of SCMs can support sustainable design practices by improving the durability and performance of structures while also reducing their environmental impact. This supports a circular approach to design, construction and operation of buildings and infrastructure
  that improves their social, economic and environmental sustainability.

What future trends or developments do you foresee in the use of SCMs within the cement industry?
Future trends in the use of SCMs within the cement industry are likely to focus on: increased utilisation of diverse waste-derived SCMs, development of new SCM sources to address potential shortages, advanced characterisation techniques to optimise SCM blends and data-driven approaches to predict and optimise SCM usage for reduced carbon footprint and improved concrete performance; all driven by the growing need for sustainable cement production and stricter environmental regulations.
Key aspects of this trend include:

• Expanding SCM sources: Exploring a wider range of industrial byproducts and waste materials like recycled concrete aggregate, activated clays and certain types of industrial minerals as potential SCMs to reduce reliance on traditional sources like fly ash, which may become increasingly limited.
• Advanced material characterisation: Utilising sophisticated techniques to better understand the chemical and physical properties of SCMs, allowing for more precise blending and optimisation of their use in cement mixtures.
• Data-driven decision making: Implementing machine learning and big data analysis to predict the performance of different SCM combinations, allowing for real-time adjustments in cement production based on available SCM sources and desired concrete properties.
• Focus on local sourcing: Prioritising the use of locally available SCMs to reduce transportation costs and environmental impact.
• Development of new SCM processing techniques: Research into methods to enhance the reactivity and performance of less readily usable SCMs through processes like activation or modification.
• Life cycle analysis (LCA) integration: Using LCA to assess the full environmental impact of different SCMs and optimise their use to minimise carbon emissions throughout the cement production process.
• Regulatory frameworks and standards:Increased adoption of building codes and industry standards that promote the use of SCMs and set targets for reduced carbon emissions in cement production.

– Kanika Mathur