Basalt fiber (BF), known as “the green industrial material of the XXI-century”, combines ecological safety, natural longevity and many other properties. It is not a new material, but its applications are surely innovative in many industrial and economic fields, from building and construction to energy efficiency, from automotive to aeronautic, thanks to its good mechanical and chemical performances. Hence basalt fiber has gained increasing attention as a reinforcing material especially compared to traditional glass and carbon fibers. In this context, several studies dealing with glass and carbon fiber reinforced composites consider the significance of basalt fiber as a new reinforcing material.

Basalt fiber

As it is well known, basalt is the name given to a variety of volcanic rock, known principally for its resistance to high temperatures, strength and durability, widely diffused all around the world, in which SiO2 accounts for the main part, followed by Al2O3, then Fe2O3, FeO, CaO and MgO. For this reason, basalt rocks are classified according to the SiO2 content as alkaline (up to 42% SiO2), mildly acidic (43 to 46% SiO2) and acidic basalts (over 46% SiO2). Only acidic type basalts satisfy the conditions for fiber preparation.

Basalt applications are well known from roman age where this material was used in its natural form as a paving and building stone: actually basalt can also be formed into a continuous fiber having unique chemical and mechanical properties, so that it is ideally suited for demanding applications requiring resistance against high temperatures, insulation properties, acid and solvent resistance, durability, mechanical strength, low water absorption, etc.

Among others, two more characteristics must be highlighted:

1. basalt fiber can be suited for fire protective applications and so it can replace almost all applications of asbestos without any impact on human health, thanks to the fiber’s size that make it non-breathable. In this regard, in 1998 an official list containing the names of the materials that can replace asbestos – Decreto Ministero dell’Industria del Commercio e dell’Artigianato 26.03.1998 –Elenco contenente i nomi delle imprese e dei materiali sostitutivi dell’amianto che hanno ottenuto l’omologazione – was published in Italy and among those materials there is also the basalt fiber;
2. basalt fiber is an eco-compatibility material, characterized from an easier recyclability if compared, for example, to glass fiber. Infact the principal problem in glass fibers recycling is that they melt during incineration, sticking to the inside of the incineration chamber. The result is a costly clean-up effort and significant downtime. Basalt, instead, has a melting point of about 1400 °C; this means that after some composite material containing basalt fibers is incinerated, the only product left is an unmolten, fully usable basalt that can be swept from the incineration. And this is naturally a considerable added value.

Unweathered basalt is black or gray.

On Earth, most basalt lava rock magmas have formed by decompression melting of the mantle. Basalt has also formed on Earth’s Moon, Mars, Venus, and even on the asteroid Vesta. Source rocks for the partial melts probably include both peridotite and pyroxenite The crustal portions of oceanic tectonic plates are composed predominantly of basalt, produced from upwelling mantle below ocean ridges.

The term basalt is at times applied to shallow intrusive rocks with a composition typical of basalt, but rocks of this composition with a phaneritic (coarse) groundmass are generally referred to as dolerite (also called diabase) or gabbro

This material can be used for commercial or residential applications as well as interior and exterior use.

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