Dr SB Hegde, Professor and Director of Postgraduate Studies, Jain College of Engineering and Technology, Hubli, and Visiting Professor, Pennsylvania State University, USA, discusses the innovations in kiln and refractory management.

The role of kilns and refractories in meeting evolving cement production demands is paramount, as they directly influence operational efficiency, cost control, and environmental compliance. Indian cement production currently stands at over 421 million tonnes per annum (MTPA), with projections to exceed 800 MTPA by 2030, driven by urbanisation and infrastructure investments. Kiln utilisation in India averages 75 to 85 per cent, reflecting a robust demand for consistent clinker production.
Refractory costs constitute around 15 to 20 per cent of the operational expenditure in cement plants, primarily driven by frequent maintenance cycles due to high thermal loads and wear. Innovations in refractory materials, such as alkali-resistant bricks and low-cement castables, are increasingly adopted to improve kiln life, reduce downtime, and enhance heat retention. Decarbonisation has pushed plants to upgrade kiln technology, transitioning to pre-calciner systems and alternate fuels, which in turn demand advanced refractory materials to withstand chemical and thermal stresses.
Government initiatives like the National Infrastructure Pipeline (NIP) with a projected investment of `111 lakh crore and schemes like PMAY and Gati Shakti are expected to significantly boost cement demand. For example, NIP alone involves 9,300+ projects, leading to increased kiln utilisation and a sharper focus on energy efficiency and reduced emissions. Industry leaders such as UltraTech and Dalmia Bharat are investing heavily in low-carbon and energy-efficient production, with capital expenditures exceeding `12,000 crore for capacity expansion and carbon-neutral initiatives.
In alignment with global trends, Indian cement plants are also integrating smart technologies for predictive maintenance of kilns, reducing refractory wear, and optimising fuel use. Such advancements aim to lower production costs and align with the industry’s sustainability goals. This strategic emphasis positions the kiln and refractory segments as critical components in addressing the challenges of decarbonisation, cost efficiency, and operational excellence in a competitive market landscape.

Advanced Kiln Operation Strategies
A. Dynamic Process Optimisation
AI-Driven Kiln Control Systems: The adoption of artificial intelligence (AI) in kiln operations is revolutionising cement manufacturing by enhancing efficiency and reducing costs. Indian cement plants such as UltraTech and Dalmia Bharat have begun deploying AI-driven kiln control systems like ABB’s Advanced Process Control and FLSmidth’s Expert Optimiser. These systems leverage machine learning to adjust kiln parameters in real time, achieving higher stability and reducing fuel consumption. For instance, AI integration has demonstrated a return on investment (ROI) of up to 15 per cent within two years in energy savings alone.
Data-Driven Process Modeling: Real-time data from sensors and IoT devices is now utilised for process modelling to optimise fuel mix. For example, Indian plants have achieved specific heat consumption reductions of approximately 5 per cent by fine-tuning the proportion of petcoke and coal blends using advanced algorithms. This aligns with decarbonisation goals while maintaining clinker quality.
Case Study: A leading cement manufacturer in Rajasthan implemented an advanced AI kiln control system, reducing specific heat consumption from 750 kcal/kg to 712 kcal/kg of clinker, saving `20 crore annually in fuel costs while cutting CO2 emissions by 10,000 tons per annum.

B. Impact of Alternative Fuels on Kiln Dynamics
Co-Processing of Waste: Indian cement plants increasingly use refuse-derived fuels (RDF) and plastic waste, aligning with sustainability objectives.
Co-processing at cement plant/s for instance, has replaced up to 15 per cent of conventional fuel with alternative fuels, saving up to 50 per tonne of clinker produced. However, these fuels pose challenges such as fluctuating flame stability and accelerated refractory wear, requiring high-performance refractory linings.
Thermal Efficiency and Refractory Wear: Petroleum coke (petcoke) and biomass are widely used as alternative fuels, with petcoke offering superior calorific value but exacerbating alkali attacks on refractories. Biomass, while more sustainable, requires modified kiln burners to maintain thermal efficiency. Studies show that petcoke can reduce thermal efficiency by 3 per cent while increasing refractory maintenance costs by 10 per cent.
Comparative Analysis: An Indian kiln running on coal exhibits a refractory life cycle of approximately 12 months, whereas the use of RDF and petcoke often reduces this to 8-10 months. This highlights the need for advanced refractory materials resistant to alkali and chlorine attacks common with alternative fuels.
C. Advanced Material Flow Management
Mitigating Coating and Ring Formation: Predictive tools based on AI and machine learning are now addressing material build-up issues such as ring and coating formation. Plants using AI systems report a 25 per cent reduction in unplanned stoppages due to excessive coating, translating into savings of `5 crore annually.
Impact of Rawmix Variability: Variations in raw material chemistry, particularly silica and alumina content, affect refractory life. Data from Indian plants shows that deviations in raw mix standard deviation beyond ±1.5 per cent reduce refractory lifespan by 20 per cent. Advanced raw material blending systems, such as Schenck Process feeders, ensure consistent feed chemistry, enhancing kiln lining durability.
Insights into Blending Precision: Enhanced raw material precision in an Andhra Pradesh cement plant increased refractory life by three months, yielding a cost reduction of `1.2 crore annually in maintenance expenses. Investments in XRF analysers and online quality monitoring systems are increasingly adopted to sustain these results.
These advanced strategies demonstrate the transformative potential of technology and innovation in improving kiln operations and refractory management. Integrating AI, alternative fuels, and precision raw material control positions Indian cement plants for sustainable and cost-efficient production.

Cutting-Edge Refractory
Management Practices
A. Innovative Refractory Materials
Development of Alkali-Resistant Bricks and Coatings: Modern kilns frequently operate with alternative fuels, including refuse-derived fuels (RDF), petcoke, and biomass, which lead to increased alkali loads and vapor-phase infiltration. High alumina and magnesia-rich bricks with low silica content have become critical in managing alkali attack. These bricks incorporate additives like zircon and spinel to resist alkali penetration at temperatures above 1300°C. Recent data from Indian kilns utilising RDF indicates a refractory lifespan improvement from 10 months to 15 months with alkali-resistant linings. Furthermore, advanced ceramic coatings with a thickness of 0.5–1 mm are applied to enhance resistance to alkali-induced chemical stress and thermal spalling, particularly in the lower transition zones.
High-Performance Monolithic Refractories: Monolithic refractories, specifically low-cement castables (LCCs) and ultra-low-cement castables (ULCCs), are replacing conventional bricks in various kiln sections due to their seamless structure, superior thermal shock resistance, and low porosity. In preheater and calciner zones of Indian cement plants, ULCCs have demonstrated a 25 per cent reduction in maintenance frequency. For example, at a kiln in Karnataka, LCC applications resulted in specific heat savings of 2.5 per cent, contributing to annual fuel cost reductions of `3 crore. These refractories also exhibit higher abrasion resistance, withstanding air velocities of up to 25 m/s in cyclone stages without significant wear.
Nano-Structured Refractory Solutions: Nano-engineered refractory materials use ultra-fine oxides like nano-alumina and nano-zirconia, improving thermal and mechanical properties. These refractories provide enhanced creep resistance at temperatures exceeding 1400°C and reduce thermal conductivity by up to 15 per cent. Trials conducted at UltraTech Cement showed a significant reduction in heat loss through the kiln shell, enhancing overall thermal efficiency. The adoption of these materials is projected to increase by 30 per cent across Indian plants by 2030, driven by the need for higher energy efficiency.
B. Proactive Refractory Monitoring
Thermal Imaging and Laser-Based Shell Scanning: Advanced thermal imaging tools detect surface hotspots with precision down to 1°C. In the rotary kiln of an Andhra Pradesh plant, implementing such tools reduced undetected refractory wear by 40 per cent, leading to annual cost savings of `2.7 crore. Laser shell scanners, capable of mapping shell temperatures along the kiln’s length, have enhanced monitoring accuracy, enabling predictive maintenance schedules that minimise unscheduled shutdowns.
IoT-Enabled Refractory Sensors: Real-time data acquisition through IoT-integrated sensors embedded in refractory linings provides insights into temperature gradients, heat flux, and stress distribution. These sensors use wireless communication to alert operators to potential failure points. A study at a Gujarat plant using IoT-enabled systems showed a 10 per cent improvement in refractory life, translating to savings of `1.5 crore annually. Such systems are instrumental in reducing failures caused by temperature shocks exceeding 100°C/min during emergency shutdowns.
Case Study: A kiln at a major Indian cement producer integrated predictive analytics with shell temperature data. The system identified abnormal wear patterns near the kiln’s hot spot zone, enabling preemptive relining during scheduled maintenance. This proactive approach extended refractory life by 20 per cent and saved `4 crore over three years.
C. Failure Mechanisms and Mitigation
Thermal-Mechanical-Chemical Degradation: Refractory wear in Indian kilns is predominantly driven by the combined effects of thermal cycling, mechanical load variations, and chemical attack. Thermal cycling, particularly during start-ups and shutdowns, creates thermal shock stresses that exceed the critical tensile strength of refractories, causing cracks and spalling. High alkali content from petcoke or RDF leads to the formation of alkali sulphates and chlorides, which infiltrate and weaken the lining. Moreover, mechanical stresses from
coating dislodgement and raw material build-up exacerbate wear.
Advanced Coatings for Thermal Shock and Erosion: Spinel-rich ceramic coatings with nano-bonding technology reduce thermal gradients and erosion rates by forming a thermal barrier with low thermal expansion coefficients. These coatings, applied in calciner zones, reduced thermal shock-related spalling incidents by 30 per cent at a Rajasthan plant operating with mixed-fuel inputs.
R&D Case Study – Hybrid Refractory Formulations: Researchers are developing hybrid formulations combining magnesia-alumina spinels and silicon carbide (SiC) to improve resistance to thermal shock and abrasion. Trials in a Tamil Nadu plant demonstrated a 20 per cent reduction in material loss during high thermal cycling, with improved alkali resistance. Additionally, coatings incorporating graphene oxide reduced hot face temperature by 30°C, further extending refractory life.

Cost Implications and Operational Insights
A. Refractory Performance vs. OPEX
Breakdown: Refractory Cost per Tonne of Clinker Produced: In Indian kilns, refractory costs typically range between Rs.20 and Rs.40 per tonne of clinker, depending on the kiln size, fuel mix, and quality of refractories used. Plants employing higher-grade refractories, such as spinel-based or high-alumina bricks, report costs at the upper end of this range. For example, a kiln producing 5000 tonnes per day with advanced refractory materials incurs an annual refractory cost of Rs.6–7 crore, contributing 1–1.5 per cent of total operational expenditure (OPEX).
Impact of Suboptimal Refractories on Downtime and Clinker Costs: Suboptimal refractories can lead to frequent shutdowns, increased maintenance costs, and reduced clinker output. For instance, at a plant in Gujarat, refractory failures caused by poor alkali resistance led to a 5-day unscheduled shutdown, resulting in production losses of 10,000 tonnes and a cost escalation of `4.5 crore. A subpar refractory with a lifecycle of 8 months often results in 15–20 per cent higher overall costs compared to premium options lasting 12–18 months.
Comparative Study: ROI of High-Quality vs. Cheaper Refractories: High-quality refractories, while costlier upfront, deliver significantly better ROI. A Tamil Nadu plant using imported magnesia-alumina spinel bricks achieved a lifecycle extension of 24 months compared to 10 months for lower-grade bricks, reducing the total cost per tonne by
Rs.3. Advanced refractory adoption reduced clinker cost by 2 per cent, translating to annual savings of `4 crore for a 6000 TPD kiln.
B. Balancing Cost with Performance
Strategic Sourcing Models for Refractory Procurement in India: Indian cement plants increasingly adopt hybrid sourcing models, balancing local and imported refractories. While local refractories are cost-effective for general applications, imported options, such as European spinel or Japanese
magnesia-chrome refractories, offer superior performance in high-stress zones. Approximately 30 to 35 per cent of refractories used in premium Indian plants are imported, particularly for transition and burning zones.
Impact of Bulk Procurement and Vendor Partnerships: Collaborative procurement strategies, such as long-term agreements with suppliers, provide cost advantages of up to 15 per cent. For instance, bulk procurement of low-cement castables (LCC) by a cluster of cement plants in Andhra Pradesh achieved a 12 per cent reduction in unit costs. Vendor partnerships, where payments are linked to refractory lifecycle performance, further incentivise quality. An integrated plant in Rajasthan achieved Rs.2 crore annual savings through such a model.
Latest Procurement Trends: Performance-linked pricing is gaining traction in the Indian cement industry, where refractory vendors are evaluated based on key performance indicators (KPIs) such as lifecycle, downtime reduction, and clinker quality impact. In 2023, a Gujarat plant adopted this model, tying 20 per cent of payments to refractory performance metrics, achieving a 15 per cent increase in refractory lifecycle.
The integration of advanced materials and data-driven procurement practices is reshaping refractory management in Indian kilns, enabling cost-effective and reliable operations. Balancing cost with performance requires a nuanced approach, leveraging high-quality materials, strategic partnerships, and performance-focused contracts.

Sustainability and Decarbonisation
A. Low-Carbon Kiln Operations
Reduction in Thermal Losses: Advanced refractories significantly minimise thermal losses in cement kilns, leading to reduced specific heat consumption. High-performance materials such as spinel-based and nano-bonded refractories have thermal conductivities 20 to 30 per cent lower than conventional options. For instance, an Indian cement plant in Madhya Pradesh reported a 6 per cent reduction in fuel consumption after upgrading its burning zone with high-alumina refractories engineered for higher insulation properties. This translates to a savings of approximately Rs.3.5 crore annually for a 6000 TPD kiln.
CO2 Emissions Reduction: By lowering fuel requirements, advanced refractories indirectly contribute to CO2 emission reductions. A case study from a leading cement manufacturer in Tamil Nadu showed that using ultra-low thermal conductivity refractories resulted in 0.1 tonnes of CO2 reduction per tonne of clinker, equivalent to a 5 per cent reduction in total emissions. This approach aligns with India’s commitment to reducing cement industry CO2 intensity by 45 per cent by 2050 under the Paris Agreement targets.
B. Recyclability of Spent Refractories
Recycling Spent Refractories into Raw Meal: Recycling initiatives are gaining traction in India as a means of improving sustainability and reducing raw material dependency. Spent refractories containing alumina and silica are increasingly being reused in kiln feedstock. For example, Dalmia Cement’s Ariyalur plant implemented a spent refractory recycling program, processing 300 tonnes annually into raw meal, resulting in savings of `2 crore in virgin material costs.
Economic Feasibility in Cost-Sensitive Markets: The recycling of refractories faces economic challenges, particularly in cost-sensitive regions. However, the adoption of efficient grinding and sorting technologies has made recycling viable. With an investment of Rs.50 lakhs in specialised equipment, one Karnataka-based plant reduced refractory disposal costs by 50 per cent while achieving a 10 per cent raw material cost offset.
C. Green Refractory Innovations
Development of Low-Carbon Refractories: Emerging R&D focuses on reducing the embodied carbon in refractories through alternative raw materials and production methods. For instance, magnesia-carbon refractories manufactured with bio-based binders instead of phenolic resins have shown a 15 per cent reduction in lifecycle carbon emissions. Adoption of these materials has started in premium plants in Maharashtra and Gujarat, which aim to lower their overall carbon footprint.
Adaptation of Global R&D for Indian Conditions: Globally, innovations such as non-chrome refractories and geopolymers are being adapted for Indian conditions. A collaboration between a Japanese refractory giant and an Indian manufacturer has led to the development of chrome-free bricks resistant to alkali and thermal shocks, optimised for kilns using Indian raw materials. Initial trials in Andhra Pradesh indicate a 20 per cent lifecycle improvement and a 25 per cent reduction in embodied carbon compared to conventional chrome-bearing options.
These advancements in kiln and refractory management underscore the cement industry’s ability to align operational goals with sustainability targets, paving the way for a greener, more efficient future.

Technological Advancements
A. Digital Twins for Kiln and Refractory Management
Simulating Refractory Wear and Optimising Kiln Performance: Digital twins replicate kiln operations virtually, enabling precise monitoring of refractory conditions and predictive analysis of wear patterns. These simulations help optimise operational parameters like fuel flow, rotational speed, and air distribution. In India, ACC Cement has implemented digital twins in a pilot project at its Wadi plant, reducing refractory failure rates by 15 per cent and increasing kiln availability by 8 per cent.
Pilot Projects in India: A key success story is UltraTech Cement’s adoption of digital twins at its Rawan plant. The system predicted hotspots leading to thermal degradation, allowing the team to preemptively reline sections of the kiln, saving Rs.1.2 crore annually in downtime and material costs. These projects show significant promise for widespread adoption, particularly in plants operating at >90 per cent capacity utilisation.
B. AI and Machine Learning Applications
Predictive Maintenance Tools for Refractory Performance: AI-driven tools analyse historical data on temperature, load, and chemical exposure to predict refractory life. For example, JSW Cement employs an AI-powered maintenance system that combines real-time thermal imaging with historical failure data, resulting in a 20 per cent reduction in unplanned maintenance events and Rs.1 crore annual savings.
ML-Based Algorithms for Failure Prediction: Machine learning algorithms have proven effective in identifying patterns of high-temperature zone failures, particularly in plants co-processing alternative fuels. At a Gujarat plant, a predictive model flagged potential failures in the burning zone 30 days in advance, allowing for targeted interventions.
This proactive approach increased refractory lifespan by 10 per cent, reducing replacement costs byRs.50 lakhs annually.
C. Emerging Refractory Materials
Ultra-High-Temperature Refractories for Newer Kiln Designs: Innovations in materials science have led to the development of ultra-high-temperature refractories capable of withstanding 2000°C without spalling or significant wear. Indian plants utilising these materials in kilns designed for alternative fuels have reported significant benefits. For instance, a Dalmia Cement plant in Tamil Nadu introduced nano-ceramic bonded bricks, resulting in a 25 per cent improvement in thermal efficiency and a 15 per cent extension in refractory life.
Case Study: Extending Refractory Life by 30 per cent: A Tier-1 cement plant in Rajasthan collaborated with a Japanese manufacturer to adopt magnesia-spinel bricks tailored for local kiln conditions. These advanced refractories not only extended the lining’s life by 30 per cent but also reduced fuel consumption by 5 per cent, yielding annual savings of Rs.2.5 crore.
The integration of digital twins, AI, and advanced materials underscores the cement industry’s commitment to leveraging technology for operational excellence. These advancements are driving cost efficiency, sustainability, and reliability in an increasingly competitive market.

Advanced R&D Insights
A. Collaborations and Innovations
Indian Cement Industry Partnerships: Indian cement manufacturers are increasingly collaborating with refractory suppliers to develop tailored solutions that address the specific challenges of local kiln conditions, such as high thermal gradients and the use of alternative fuels. For example, Shree Cement partnered with RHI Magnesita to develop specialised refractories for kilns using petcoke. This collaboration resulted in a 15 per cent increase in refractory lifespan and a 10 per cent reduction in downtime.
Cross-Industry R&D on Refractory Chemistry: Cross-industry research is driving innovations in refractory chemistry, with Indian firms collaborating with global players in steel and glass sectors. A notable initiative is the Tata Steel Research Centre’s partnership with UltraTech Cement to study thermal shock resistance in refractories, leading to a hybrid solution that combines the properties of magnesia and alumina. Initial trials indicate a 12 per cent improvement in thermal resilience under high-stress conditions.
B. Experimental Developments
Computational Modeling for High-Stress Zones: Advanced computational models are being used to simulate the behavior of refractories under extreme conditions, including high-temperature gradients and chemical attack. In a joint project by Birla Institute of Technology and Indian cement manufacturers, finite element analysis (FEA) was employed to predict wear patterns in rotary kilns. This research reduced the frequency of unplanned shutdowns by providing accurate wear predictions.
Minimising Alkali-Silica Reactions: Experimental research on alkali-silica reactions (ASR) caused by petcoke ash is gaining momentum. Studies conducted at CSIR-Central Glass & Ceramic Research Institute revealed that introducing zircon-based additives to refractories mitigates ASR-related damage, enhancing the durability of bricks by 20 per cent. Plants in Gujarat and Rajasthan have begun implementing these findings, with promising results in reducing kiln maintenance cycles.
C. Global vs. Indian Trends
Comparative R&D Budgets: Global leaders in the refractory industry, such as Vesuvius and Saint-Gobain, allocate 4–6 per cent of annual revenue to R&D, while Indian counterparts, including local refractory manufacturers, typically spend less than 1 per cent. For example, in 2023, RHI Magnesita invested €50 million globally in refractory R&D, compared to Rs.30 crores by the top Indian manufacturers collectively.
Lessons from Global Practices: Global refractory management practices emphasise predictive maintenance and advanced material science, with significant adoption of AI-based tools and robotics. Indian plants are gradually adapting these practices, with Ambuja Cement and ACC implementing robotic refractory installation systems in select kilns. While adoption remains limited, these innovations have reduced installation times by 25 per cent and increased overall safety.
These R&D advancements, collaborations, and global benchmarking efforts are setting the stage for the Indian cement industry to overcome traditional limitations and achieve greater efficiency, sustainability, and competitiveness in kiln and refractory management.

Future of Kiln and Refractory Management in India
Adoption of Circular Economy Principles in Refractory Usage: The Indian cement industry is moving towards circular economy models, focusing on the reuse, recycling, and repurposing of spent refractories. Traditionally discarded as waste, spent refractories are now being processed for use as secondary raw materials in clinker production. For instance, ACC Cement and UltraTech have implemented systems to integrate 30–40 per cent of spent refractories into raw meal blends, reducing dependence on virgin materials. This initiative aligns with India’s commitment to reducing industrial waste and has the potential to cut refractory disposal costs by `15–20 crore annually across the industry. Globally, advanced recycling technologies have demonstrated significant success. Indian manufacturers are collaborating with international players like Vesuvius to bring these technologies into the domestic market. Research indicates that widespread adoption of refractory recycling could lead to annual savings of Rs.500–700 per tonne of clinker produced in India.
Vision 2030: Energy-Efficient Kilns and Next-Gen Refractories: The Indian cement industry’s “Vision 2030” emphasises the adoption of ultra-modern kilns capable of achieving thermal efficiencies beyond 85 per cent. These kilns will require next-generation refractories with high thermal insulation and resistance to alternative fuel residues. Nano-engineered refractories are expected to play a critical role in this transformation, with pilot projects already showing a 10–15 per cent increase in energy efficiency. As of 2024, India’s average thermal energy consumption for clinker production stands at 720 kcal/kg clinker, compared to global benchmarks of 650 kcal/kg. Adoption of advanced refractories is projected to bridge this gap, saving up to `25 per tonne of clinker. The increased durability of these materials will also reduce kiln downtime, improving overall plant productivity by 5–7 per cent.
Predictions: Cost Savings and Emission Reductions with New Refractory Technologies: Advanced refractory materials and kiln technologies are forecasted to yield significant cost and environmental benefits by 2030. By implementing cutting-edge materials like high-alumina and magnesia-spinel bricks, Indian plants could achieve annual cost savings of `1,000–1,500 crore collectively through reduced maintenance and enhanced thermal efficiency. Emission reductions are also a critical area of impact. Studies indicate that optimising refractory performance can lower CO2 emissions by 0.02–0.05 tonnes per tonne of clinker produced. For an industry producing 350 million tonnes annually, this translates to an annual reduction of 7–17.5 million tonnes of CO2, supporting India’s broader climate goals under the Paris Agreement.

Conclusion
The adoption of advanced kiln operation strategies and refractory management practices is no longer optional but essential for the Indian cement industry to remain competitive in an evolving global landscape. Advanced digital tools such as AI-driven control systems and digital twins have demonstrated significant operational efficiencies, reducing specific heat consumption by 5–10 per cent and increasing clinker quality consistency. Simultaneously, the integration of high-performance refractory materials has enhanced durability and reduced maintenance costs, saving up to `1,000–1,500 crore annually across the industry. Sustainability is at the core of these advancements. Recycling initiatives for spent refractories and the development of low-carbon refractory materials are paving the way for a circular economy, contributing to a reduction of 7–17.5 million tonnes of CO2 annually. As Vision 2030 unfolds, the alignment of refractory technologies with India’s carbon neutrality goals will help cement plants achieve significant energy efficiency gains and meet stringent environmental targets.
In conclusion, industry-wide adoption of these innovative practices is imperative. While the upfront investment in advanced refractories and digital technologies might seem substantial, the long-term benefits in cost savings, operational excellence, and environmental impact far outweigh the initial costs. By embracing these solutions, the Indian cement industry can set global benchmarks for sustainability and efficiency, ensuring its growth and relevance in a carbon-conscious world.

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ABOUT THE AUTHOR:
Dr SB Hegde is an industrial leader with expertise in cement plant operation and optimisation, plant commissioning, new cement plant establishment, etc. His industry knowledge cover manufacturing, product development, concrete technology and technical services.