# Basalt fiber

Basalt fibers are produced from basalt rocks by melting them and converting the melt into fibers. Basalts are rocks of igneous origin. Basalt fibers are classified into 3 types:
* Basalt continuous fibers (BCF), used for the production of reinforcing materials and composite products, fabrics, and non-woven materials;
* Basalt staple fibers, for the production of thermal insulation materials; and
* Basalt superthin fibers (BSTF), for the production of high quality heat- and sound-insulating and fireproof materials.

## Manufacturing process

The technology of production of basalt continuous fiber (BCF) is a one-stage process: melting, homogenization of basalt and extraction of fibers. Basalt is heated only once. Further processing of BCF into materials is carried out using "cold technologies" with low energy costs.
Basalt fiber is made from a single material, crushed basalt, from a carefully chosen quarry source. Basalt of high acidity (over 46% silica content) and low iron content is considered desirable for fiber production. Unlike with other composites, such as glass fiber, essentially no materials are added during its production. The basalt is simply washed and then melted.
The manufacture of basalt fiber requires the melting of the crushed and washed basalt rock at about 1,500 °C (2,730 °F). The molten rock is then extruded through small nozzles to produce continuous filaments of basalt fiber.
The basalt fibers typically have a filament diameter of between 10 and 20 μm which is far enough above the respiratory limit of 5 μm to make basalt fiber a suitable replacement for asbestos. They also have a high elastic modulus, resulting in high specific strength—three times that of steel. Thin fiber is usually used for textile applications mainly for production of woven fabric. Thicker fiber is used in filament winding, for example, for production of compressed natural gas (CNG) cylinders or pipes. The thickest fiber is used for pultrusion, geogrid, unidirectional fabric, multiaxial fabric production and in form of chopped strand for concrete reinforcement. One of the most prospective applications for continuous basalt fiber and the most modern trend at the moment is production of basalt rebar that more and more substitutes traditional steel rebar on construction market.

## Properties

The table refers to the continuous basalt fiber specific producer. Data from all the manufacturers are different, the difference is sometimes very large values.
| Property | Value |
| Tensile strength | 2.8–3.1 GPa (410–450 ksi) |
| Elastic modulus | 85–87 GPa (12,300–12,600 ksi) |
| Elongation at break | 3.15% |
| Density | 2.67 g/cm$^3$ (0.096 lb/cu in) |
Comparison:
| Material | Density (g/cm$^3$) | Tensile strength (GPa) | Specific strength | Elastic modulus (GPa) | Specific modulus |
| Steel rebar | 7.85 | 0.5 | 0.0637 | 210 | 26.8 |
| A-glass | 2.46 | 2.1 | 0.854 | 69 | 28 |
| C-glass | 2.46 | 2.5 | 1.02 | 69 | 28 |
| E-glass | 2.60 | 2.5 | 0.962 | 76 | 29.2 |
| S-2 glass | 2.49 | 4.83 | 1.94 | 97 | 39 |
| Silicon | 2.16 | 0.206-0.412 | 0.0954-0.191 | | |
| Quartz | 2.2 | 0.3438 | 0.156 | | |
| Carbon fiber (large) | 1.74 | 3.62 | 2.08 | 228 | 131 |
| Carbon fiber (medium) | 1.80 | 5.10 | 2.83 | 241 | 134 |
| Carbon fiber (small) | 1.80 | 6.21 | 3.45 | 297 | 165 |
| Kevlar K-29 | 1.44 | 3.62 | 2.51 | 41.4 | 28.7 |
| Kevlar K-149 | 1.47 | 3.48 | 2.37 | | |
| Polypropylene | 0.91 | 0.27-0.65 | 0.297-0.714 | 38 | 41.8 |
| Polyacrylonitrile | 1.18 | 0.50-0.91 | 0.424-0.771 | 75 | 63.6 |
| Basalt fiber | 2.65 | 2.9-3.1 | 1.09-1.17 | 85-87 | 32.1-32.8 |
| Material type | Elastic modulus (E) | Yield stress (fy) | Tensile strength (fu) |
| 13-mm-diameter steel bars | 200 GPa (29,000 ksi) | 375 MPa (54.4 ksi) | 560 MPa (81 ksi) |
| 10-mm-diameter steel bars | 200 GPa (29,000 ksi) | 360 MPa (52 ksi) | 550 MPa (80 ksi) |
| 6-mm-diameter steel bars | 200 GPa (29,000 ksi) | 400 MPa (58 ksi) | 625 MPa (90.6 ksi) |
| 10-mm-diameter BFRP bars | 48.1 GPa (6,980 ksi) | - | 1,113 MPa (161.4 ksi) |
| 6-mm-diameter BFRP bars | 47.5 GPa (6,890 ksi) | - | 1,345 MPa (195.1 ksi) |
| BFRP sheet | 91 GPa (13,200 ksi) | - | 2,100 MPa (300 ksi) |

## History

The first attempts to produce basalt fiber were made in the United States in 1923 by Paul Dhe who was granted U.S. patent 1,462,446. These were further developed after World War II by researchers in the US, Europe and the Soviet Union especially for military and aerospace applications. Since declassification in 1995 basalt fibers have been used in a wider range of civilian applications.

### Schools

* RWTH Aachen University. Every two year RWTH Aachen University's Institut für Textiltechnik hosts the International Glass Fibers Symposium where basalt fiber is devoted a separate section. The university conducts regular research to study and improve basalt fiber properties. Textile concrete is also more corrosion-resistant and more malleable than conventional concrete. Replacement of carbon fibers with basalt fibers can significantly enhance the application fields of the innovative composite material that is textile concrete, says Andreas Koch.
* The Institute for Lightweight Design Materials Science at the University of Hannover
* The German Plastics Institute (DKI) in Darmstadt
* The Technical University of Dresden had contributed in the studying of basalt fibers. Textile reinforcements in concrete construction - basic research and applications. The Peter Offermann covers the range from the beginning of fundamental research work at the TU Dresden in the early 90s to the present. The idea that textile lattice structures made of high-performance threads for constructional reinforcement could open up completely new possibilities in construction was the starting point for today's large research network. Textile reinforcements in concrete construction - basic research and applications. As a novelty, parallel applications to the research with the required approvals in individual cases, such as the world's first textile reinforced concrete bridges and the upgrading of shell structures with the thinnest layers of textile concrete, are reported.
* University of Applied Sciences Regensburg, Department of Mechanical Engineering. Mechanical characterization of basalt fibre reinforced plastic with different fabric reinforcements – Tensile tests and FE-calculations with representative volume elements (RVEs). Marco Romano, Ingo Ehrlich.

## Uses

* Heat protection
* Friction materials
* Windmill blades
* Lamp posts
* Ship hulls
* Car bodies
* Sports equipment
* Speaker cones
* Cavity wall ties
* Rebar
* Load bearing profiles
* CNG cylinders and pipes
* Absorbent for oil spills
* Chopped strand for concrete reinforcement
* High pressure vessels (e.g. tanks and gas cylinders)
* Pultruded rebar for concrete reinforcement (e.g. for bridges and buildings)

## Design codes
### Russia

Since October 18, 2017, JV 297.1325800.2017 "Fibreconcrete constructions with nonmetallic fiber has been put into operation. Design rules, "which eliminated the legal vacuum in the design of basalt reinforced fiber reinforced concrete. According to paragraph 1.1. the standard extends to all types of non-metallic fibers (polymers, polypropylene, glass, basalt and carbon). When comparing different fibers, it can be noted that polymer fibers are inferior to mineral strengths, but their use makes it possible to improve the characteristics of building composites.