This volume comprises the proceedings of the Third International Conference on Calcined Clays for Sustainable Concrete held in New Delhi, India in October 2019. The papers cover topics related to geology of clay, hydration and performance of blended systems with calcined clays, alkali activated binders, and economic and environmental impacts of the use of calcined clays in cement-based materials. The book presents research on influence of processing on reactivity of calcined clays, influence of clay mineralogy on reactivity, geology of clay deposits, and the environmental impact of use of calcined clays in cement and concrete and field applications of calcined clay in concrete. Apart from giving an overview of the progress of research during the last two years, this work also covers the state-of-the art on the practical aspects of production and use of calcined clays in construction. The contents of this volume will prove useful to researchers and graduate students working in the areas of cement chemistry, cement production, and concrete design.