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