Investigation of production possibilities of natural hydraulic binders from marls

Natural hydraulic binders were replaced by modern cement in the 20th century. The distinction between binders categorized as natural is characterized by raw materials with a naturally favorable mineralogical composition. This study aims to develop a natural hydraulic binder by calcining local marls from Türkiye. The two types of marl—Adana (CI=4.40) and Mersin (CI=0.42)—were calcined within a temperature range of 750–1050 °C. The eight different binders were produced and compared with NHL3.5 and NHL5. The chemical composition of binders changes significantly with calcination temperature. The primary hydraulic phases of M-coded binders are larnite (C₂S and C₃S), whereas A-coded binders do not contain hydraulic phases. Nevertheless, the strength gain of A-coded binders is attributed to the formation of calcium silicate hydrate (C-A-S-H) products, which are formed from the clay components (SiO₂, Al₂O₃, and Fe₂O₃), portlandite, and mixing water. The w/c of mortars at the same consistency increases with the calcination temperature of binders in M-coded mortars, while it decreases in A-coded mortars. M850 is similar to natural hydraulic lime, but its production process is the same as that of natural cement. M850 can be used in the restoration and conservation of historical structures, as well as in modern applications, with its white color enabling the mixing of desired color tones using pigments or colored binders. This study shows that natural hydraulic binders can be produced using local raw materials in Türkiye, and further research may enhance their properties. Future studies can focus on industrial production, providing sustainable local alternatives instead of costly imports.