During the construction of buildings and facilities stone materials are used: bricks, stones, blocks, panels, facing tiles and many more. But to ensure the building is solid and warm these materials must be linked together into a single monolithic structure.
To do this binders are used. Binders also represent the main component of such artificial stone materials as concrete and mortar, in which they are fastened together with grain aggregates (sand, gravel and crushed stone).
One of the first bindings used by man was raw clay. In 3,000 BC people began to use more durable binders produced artificially by firing natural stone materials. The first material was probably a gypsum binder, the next one was air lime. However, due to the lack of water resistance such material didn’t fully meet the requirements of the construction. To improve the water resistance of binders volcanic ash was added to the air lime by the ancient Romans. Later, in the XVIII century, the builders discovered that by firing limestone with high content of clay a way more effective water-resistant binder can be obtained. So this is how hydraulic lime and roman cement were born. The impetus for the further development of the production and use of binders was the invention in the beginning of XIX century, a new quality of cement higher strength and water resistance, known as Portland cement.
Currently, a variety of other mineral binders which differ in their properties are used in the construction. The modern architectural companies, like a UK-based Telling, focusing on hydraulic lime and lime mortar technologies, use over 30 types of mineral binders depending on the purpose of the project and the environmental conditions.
Mineral binders are powdered substances capable, when mixed with water (sometimes with salt solutions) of forming viscoplastic mass that gradually hardens into a stone-like body. In the construction of binders mixtures with fillers to save the binder and improve some properties of artificial stone are used.
Here are the types of mixtures are based on binders:
- Binder (e.g. gypsum) dough – a mixture of binder (gypsum) with water; hardened gypsum paste called gypsum
- Mortar mix consisting of binder, water and sand; after solidification of the mortar mixture is formed
- Concrete mix, which includes a binder, water, sand and crushed stone (or gravel)
Mineral binders, depending on their ability to harden (strength gain) under certain conditions is divided into air and hydraulic.
Air binders harden and preserve the strength for a long time only in the air; in water, they soak and lose their qualities quite quickly. The reason for decrease in the strength is relatively high solubility of the components of artificial stone. This group includes: gypsum and magnesia binders, liquid glass, air lime. Sometimes air binders include clay. However, this is not entirely justified, since the clay dough hardens solely through drying and does not change its chemical composition, which is typical for all hardened mineral binders.