This DURABLE word - BASALT!

15.08.2010

Basalt and fiber concretes

Concrete was, is and will for a very long time remain the fundamental construction material, which along with evident virtues has one basic drawback – low tensile strength. When making concrete structures for the perception of tensile load in certain zones, reinforcement with high tensile strength materials, which can insure joined work with concrete due to cohesion, is practiced.

The most wide-spread application is discrete reinforcement of concrete by steel rebars (bars, wires, ropes) for the formation of so-called ferroconcrete structures. At the same time, structures with disperse reinforcement by different fibers are well-known and used in different fields of construction. Therefore, the main requirements to fiber are resistance to the material of the concrete matrix, high tensile strength, ability to insure cohesion with concrete, and processability when making and laying the concrete mix.

Basalt fiber meets all of the above mentioned requirements and is widely used internationally on the US, Canadian and European construction markets.
Basalt chopped fiberare fibers, which, when added, increase the tensile strength of the concrete and which have a wide range of advantages compared to synthetic fibers as they are made of the strongest mineral fibers known to the mankind. Basalt fiber works in concrete more effectively than polypropylene fiber, because it is an additional mechanical element, which reinforces the structure, improves hydration, and facilitates effective work of cement in forming cement stone, while special fiber coating technology makes the fiber alkali resistant. Complex research and conclusions made by leading Ukrainian and foreign laboratories give the basis to affirm with full confidence that Basalt fiber can completely change the conception of construction. Table 1 shows results of experimental research to determine the influence of the type and content of fiber on the tensile strength of the concrete, which are indicative of the 1,8…2,2 increase of the tensile strength of the concrete due to fiber content.                                                                  

№	Basalt filament diameter, mkm	Fiber length, mm	Fiber content in dry mass, %	Axial tensile strength of the concrete, MPa	Fractional increase of the axial strength of the concrete
1	Without fiber	Without fiber	Without fiber	1,32	х
2	16	24	1%	2,37	1,8 times
3	16	24	2%	2,76	2,1 times
4	16	24	3%	2,97	2,3 times
5	16	50	1%	2,40	1,8 times
6	16	50	2%	2,84	2,2 times

The method of inclusion and dispersion of basalt fiber is rather simple and is as follows: the fibers are added by way of intergrinding with cement and fluidifier. This method insures better dispersion of fiber in portland cement and excludes clot formations in the process of forming concrete mix.

Due to its chemical inertness, Basalt fiber does not react with salts and dyes, which makes it possible to use these basalt fiber concrete solutions in building sea structures, civil engineering infrastructure, as well as in architectural and decorative types of concrete. In road construction, basalt fiber keeps concrete and rebars from penetration of anti-icing salts and aggressive substances; it also increases the retained strength and resistance to freezing/defrosting as well as roughness of the surface.

Today more and more application fields are opening for basalt fiber:

- production of foam, gas and ferroconcrete molds (fences, building blocks, bricks, beams, paving tiles, sewage wells, road curbs etc),

- concrete and industrial flooring for facilities, especially where heavy equipment is used,

- roads and runways,

- tunnels and wells,

- reconstruction and reinforcement of buildings and structures,

- structures with high level of fire security,

- buildings and structures, which are designed in seismic regions, etc.

Basalt and rebar

Basalt rebar is a unique construction material 3 times stronger and 4 times lighter than steel rebar. Its technical characteristics are: absolute corrosion, decay, and distortion resistance, unique chemical resistance, dielectric character, low thermal conductivity, and hard combustibility. All these characteristics make it possible to use basalt rebar in road construction, for reinforcement of bridges, in walling structures that are subject to highly corrosive conditions of steel rebar and concrete (ports, dry docks, sea line reinforcement).

Test results for determining the strength of bendable concrete elements reinforced y basalt fiber shown in Table 2, have shown a rather high bearing capacity of the beams with single basalt rebar reinforcement commensurable with the bearing capacity of the ferroconcrete beams with steel rebar.

Table 2

Longitudinal reinforcement ratio	Bearing capacity, kN/m
	Basalt rebar	Steel rebar А500С
0,0059	19,40	15,30
0,0086	21,30	21,51

• Modulus of elasticity not less than 70 000 MPa;
• Tensile strength not less than 1100 MPa.

The use of basalt rebar instead of steel rebar brings about the whole range of economic advantages:

• Increase of serviceability and long life of constructions and products,
• Long overhaul period for constructions,
• Possibility to install and carry out routine maintenance and repair works without the use of special lifting mechanisms and technology,
• Lower costs for transporting structures and its elements to the place of installation due to lower weight.

The use of basalt-based construction material makes it possible to substantially improve the quality and durability of constructions and materials.

D.E., Professor of Kyiv national university

of construction and architecture,

Academician of the Academy of construction of Ukraine

Yu.А. Klimov