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