Cement Manufacturers Association (CMA)

15 Beyond Bogue's Formula: Reimagining Clinker Mineralogy for Sustainable Cement Production in the 21st Century Dr S B Hegde Professor, Department of Civil Engineering, Jain College of Engineering and Technology, Hubli, India and Visiting Professor, Pennsylvania State University, United States of America 02 Abstract For nearly 100 years, Bogue's equations have been the main tool used in cement plants to predict the four key minerals in clinker (alite, belite, aluminate and ferrite) from the chemical oxides in the raw mix. Developed in the 1920s, the method assumes perfect chemical balance and pure minerals. It is still widely used today. However, modern clinkers are much more complex. It contains solid solutions, crystal defects, fast cooling effects, minor phases and amorphous (glass-like) material that Bogue's formula cannot measure accurately. Global cement production is now about 4.15 billion tons per year and releases 2.4–2.5 billion tons of CO annually — around 6–8 % of all 2 global emissions. Although the industry has cut Co intensity by 25 % since 1990, total emissions 2 remain high. This paper explains the weaknesses of Bogue's method using recent XRD data, machine- learning results from real plants, and new low- carbon cements such as LC³ and activated belite clinkers. It shows that crystal structure, microstructure and stored energy in the crystals control how cement hydrates, gain strength and last much more than simple oxide chemistry. A new “Digital Bogue” that combines AI, XRD and kiln data is proposed as the way forward. Clear recommendations are given for industry, researchers and policymakers to help the cement sector reach net-zero Co by 2070. 2 Keywords: Clinker mineralogy; Bogue's formula; LC³ cement; Activated belite; Microstructure; Digital mineralogy; Sustainability; CO reduction 2 1. Introduction Cement is the most widely used man-made material in the world. Global production now stands at about 4.15 billion tons every year.