Hans Kühl Medal of the GDCh Division of the Chemistry of Construction Materials

The chemist Prof. Dr. phil. Hans Kühl (1879–1969) was a pioneer in cement chemistry and building materials technology. The Division Board of the specialist group chose him as the namesake for the prize based on his groundbreaking scientific work and his exemplary personality. The following describes the life, work, and personality of this doyen of cement and silicate chemistry.

Professor Hans Kühl was born on February 11, 1879, in Karlsburg (Schleswig-Holstein), the son of a farmer. After graduating from the Realschule (a type of secondary school) in Flensburg in 1898, he devoted himself to the study of chemistry at the Universities of Freiburg, Kiel, and Leipzig. There, he was particularly captivated by the lectures and work of the physical chemists Wilhelm Ostwald and Max Bodenstein, whose student he considered himself to be throughout his life. In 1903, he received his doctorate ( Dr. phil.) with a dissertation on the kinetics of carbon monoxide, graduating summa cum laude.

A pivotal moment in his life dedicated to the cement industry came after his time as an assistant to Bodenstein, when he joined the Chemical-Technical Testing Institute of Dr. Hermann Passow (a cement expert widely known at the time, alongside Michaelis and Schott) in Blankenese (1905). There, Kühl made his first invention, producing cement from blast furnace slag. In 1907, the then 28-year-old Kühl moved to Berlin-Lichterfelde and took over the renowned Cement and Mortar Technology Institute from Dr. Wilhelm Michaelis, the most important German cement technologist of the time.

Scientists and practitioners

In 1922, the Lichterfelde Institute was affiliated with the Technical University of Berlin. Kühl became a lecturer at the Technical University of Berlin and, in 1925, an honorary professor. From then on, he worked there as a teacher and researcher in cement chemistry, renowned far beyond the region. Milestones of his scientific work include the introduction of the terms "silicate" and "alumina modulus" in 1913 and 1926, respectively. His "lime standard" (1933) contrasted Michaelis's empirical "hydraulic modulus" with the scientifically calculated amount of lime that the hydraulic factors can bind. In 1924, Kühl invented bauxite cement (also called "Kühl" cement) and addressed problems of fineness of grinding. Of his numerous patents, only those for the production of sulfate smelting cement (1909) and for the introduction of sludge into rotary kilns (1911) will be mentioned here. Over the decades, more than 400 technical and scientific publications in German, English, French, Italian, Russian, and Spanish emerged, testaments to his extensive research and tireless diligence. In addition to topic-specific works, Kühl repeatedly published comprehensive review articles that described the state of knowledge at the time regarding fundamental aspects of cement and building materials technology and illustrated their interrelationships. These works reveal not only Kühl as an outstanding expert but also as a gifted teacher. Examples include the articles "Fundamentals and Historical Aspects of the Hardening Theory of Mortar Materials" and "50 Years of Cement Chemistry in Theory and Practice," both published in 1951 in the journal "Silikattechnik" (Silicate Technology).

Text: Prof. Dr. Johann Plank