Earth

Cement and chalk

Binders are products that are used in the building sector. These substances, mixed with water, allow to obtain mortars that, after a particular chemical phenomenon (called “setting”), hardens and acquires mechanical resistance. Binders are classified into aerial and hydraulic binders, according to the kind of setting they have. The setting occurs when getting in contact with air or water. Limestones are raw materials for the production of lime, which is used to obtain the popular mortar that is largely applied in the building sector. Hydraulic limes harden both in the air and under the water, therefore they have “hydraulic” properties. This particular type of limes is obtained by firing marly limestones, i.e. calcareous rocks containing clay. Pozzolana is a volcanic tofa (a rock resulting from the cooling of magma that comes out of the subsoil during volcano eruptions) that contains both small grains of vitreous substance and different kinds of silicates. If pozzolana is mixed with lime the result is a binder with hydraulic properties. Rocks made of limestone with 25% of baked clay at 1500 °C lead to the production of one of the most popular hydraulic binders, which is called Portland cement. Natural chalk is used to prepare rapidly hardening chalk and filling chalk.