Basalt fibre for concrete mix study

The shortcomings of plain concrete can be reduced by adding reinforcing bars or prestressing steel. Reinforcing steel is continuous and is specifically located in the structure
to increase performance. Fibres are discontinuous and are generally distributed randomly
throughout the concrete matrix. Randomly dispersed fibres provide a three-dimensional
reinforcement compared to the traditional rebar which provides two-dimensional
reinforcement. Fibre reinforced concrete can be a cost effective and useful construction
material because of the flexibility in methods of fabrication. In slabs on grade, mining,
tunneling, and excavation support applications, steel and synthetic fibre reinforced
concrete and shotcrete have been used in lieu of welded wire fabric reinforcement

One of the greatest benefits gained by using fibre reinforcement is improved long-term
serviceability of the structure or product if properly engineered. Serviceability is the ability
of the specific structure or part to maintain its strength, integrity, and to provide its designed
function over its intended service life. Fibres can prevent the occurrence of large cracks.
These cracks permit water and contaminants to enter causing corrosion of reinforcing steel.
In addition to crack control and serviceability benefits, use of fibres at high volume
percentages (5% to 10% or higher by volume) can substantially increase the tensile strength
of FRC .

Basalt fibres are manufactured in a single-stage process by melting crushed volcanic basalt
rock. They are environmentally safe, non-toxic, possess high heat stability, and insulating
characteristics, and have an elastic structure. Basalt fibres are extremely strong and durable
and hence, it is an ideal material for structural and other construction related applications.
It provides unique mechanical properties when used in composite materials. The
mechanical characteristics of roving depend on the diameter of the elemental fibres.
Elemental fibres with smaller diameter show higher tensile strength and modulus of
elasticity than those of elemental fibres with larger diameter.

Basalt filaments are made by melting crushed volcanic basalt rock . The molten material is then extruded through special platinum bushings to produce continuous filaments of basalt fibre. The three main manufacturing techniques of basalt filaments are centrifugal-blowing, centrifugal-multiroll, and dieblowing. The fibres cool into hexagonal chains resulting in a resilient structure
substantially stronger that steel or glass fibres. Its production creates no environmental
waste.
Basalt roving is a bundle of continuous mono-directional complex basalt fibres. Basalt fibre has electrical insulating properties 10 times better than glass and has better chemical resistance than glass fibre, especially in strong alkalis. It reduces the risk of environment pollution unlike glass fibre which produces high-toxic metals and oxides during its production. Furthermore, basalt fibre has higher stiffness and strength than glass fibre.

Chopped basalt fibres are made from a continuous roving using drum chopping machines Hence, the addition of basalt fibre does not increase the dead load of FRC compared to steel fibre.
Basalt fibres are corrosion resistant unlike steel fibres. In addition, basalt fibre also has
excellent temperature resistance anti-oxidation, and anti-radiation characteristics .

Following are some of the characteristics of basalt fibre:
– High tensile strength, high thermal conductivity, high modulus of elasticity, high
sound absorption, high friction, frost, heat, and moisture resistance
– Chemical resistance to acids/alkalis, and aggressive chemicals
– No carcinogenic risk or other health hazards
– Completely inert with no environmental risks (eco-friendly)
– Good fatigue resistance
– Electro-magnetic resistance
– Resistance to ultraviolet radiation
– Dielectric characteristics
– Light weight

Basalt fibre is an effective reinforcing additive component to concrete because it improves
the thermal and mechanical properties of concrete. Basalt fibre has good adhesion with the
cement matrix. The main factor for chemical stability of basalt fibre in concrete is the
presence of heavy metal oxides in its molecular structure (Al2O3 and Fe2O3), which
prevents disintegration of basalt fibres in a highly alkaline concrete environment.

Beyond Materials Group is a growing manufacturer of non–ferrous basalt fibre materials and can meet your specification and quality requirements for a wide variety of custom applications. From our head office in Gold Coast we are able to ship our basalt products Australia wide.

Gold Coast, Brisbane, Sydney, Adelaide, Melbourne, Perth.

The development of cracks is an inevitable phenomenon in concrete structural elements, which are subjected to tensile stresses. Cracking can reduce the load bearing capacity of the structure and also accelerate deterioration, thereby shortening the service life and increasing the inspection and maintenance costs. For reinforced concrete (RC), excessive cracking reduces the overall durability by allowing water and other aggressive agents to penetrate, thus accelerating the deterioration, mainly through corrosion, of the reinforcing steel. The corroded reinforcing steel has a reduced cross-sectional area which results in a loss in the bearing capacity of the steel reinforced concrete member, as well as a reduction in the composite action between the constituent materials.

Research studies have shown that under excessive corrosion, reinforcing steel may suffer a significant loss of ductility as well as a reduction in yield and ultimate strength. In addition, there is likely to be a loss of bond strength, which may result in excessive cracking and spalling of the concrete, as well as pull-out failure of the rebars. In this respect, cracking of concrete and reduction in the cross-sectional area of the rebar can endanger the safety and serviceability of RC structures. Chloride–induced corrosion may occur in marine environments where the reinforced concrete structures are exposed to ocean salts, and may also occur inland when deicing salts come in to contact with the concrete surface of pavements and floors of parking garages . The UK’s Department of Transport (DoT) estimates that salt-induced corrosion damage costs around £616.5 million per year on motorway and trunk road bridges in England and Wales alone .

Unsatisfactory durability of concrete structures has not only severe economic impacts, since repairing deteriorated structures can cost almost as much as replacing them entirely, but also industrial, environmental and social challenges due to the reduction of reliability and safety . With this in mind, construction and infrastructure faces a real challenge to improve the resilience, maintenance and rehabilitation of RC structures to minimise the cumulative cost to society. The use of fibre reinforced polymer (FRP) reinforcement, such as carbon (CFRP) and glass (GFRP), can be an effective, sustainable and durable solution to enhance the performance of RC structures in aggressive environments. Another type of FRP that has gained popularity in construction in the recent years is basalt fibre reinforced polymer (BFRP), which is the main subject of interest in the current paper. Basalt FRP does not require the addition of any special additives during production; therefore, it is easier and cheaper to produce than other fibre types such as glass fibre .

The chemical stability of Basalt FRPs is better than glass FRPs, especially under exposure to acids, and they have very good resistance to alkaline exposure as well as corrosion from seawater . There are many economic benefits of using Basalt FRP in construction. The density of basalt is approximately one third of that of steel, which means less cost for transportation and lifting, and other associated construction costs. The tensile strength of Basalt FRP rebars is much higher that the tensile strength of steel reinforcement and consequently, smaller concrete sections can potentially be designed. Furthermore, Basalt FRP rebars do not corrode or absorb water in aggressive environments and therefore the concrete cover distance can be reduced. This is particularly useful in marine and bridge applications which currently require relatively large concrete cover distances, and therefore significant savings in construction and maintenance costs can be achieved. It has been estimated that the energy required for basalt fibre production is around 5 kWh/kg in an electric furnace, whereas the energy required to produce steel is around 14 kWh/kg [8]. It is expected that this saving in energy consumption will have an impact on the environmental performance of BFRP. Basalt FRP reinforcement bars are therefore a promising material in concrete as a replacement for at least some steel and other types of FRP reinforcement.

Beyond Materials Group is a growing manufacturer of non–ferrous basalt fibre materials and can meet your specification and quality requirements for a wide variety of custom applications. From our head office in Gold Coast we are able to ship our basalt products Australia wide.

Gold Coast, Brisbane, Sydney, Adelaide, Melbourne, Perth.

Research:

” A mechanical and environmental assessment and comparison of
basalt fibre reinforced polymer (BFRP) rebar and steel rebar in
concrete beams” by
Marianne Inmana
Eythor Rafn Thorhallssonb
Kamal Azraguea

The findings have shown that BFRP rebar is a stronger and lighter alternative to steel reinforcement in concrete beams, and that it is a very promising building material for the future. Furthermore, fewer material and energy resources are required during the production process, which leads to a better environmental profile with fewer embodied emissions. In contrast, the mechanical testing part of this experiment showed that the BFRP reinforcement has a lower elastic module than steel reinforcement. This disadvantage leads to excessive deformation at service limit state compared to steel bars, if the same cross-section area is used. However, compared to steel, BFRP does not exhibit yielding during tension. When the BFRP environmental results were compared to EPD data, there were two core findings. Firstly, EPDs for precast steel reinforced concrete beams have a similar amount of GWP emissions, ranging from 25.1 – 27.9 kgCO2eq/FU, compared to the steel reinforced concrete beams tested in this study, 23.7 kgCO2eq/FU. Secondly, when the EPD data for precast beams was replaced with EPD data for in-situ pouring concrete and 100% recycled steel, embodied emissions were significantly reduced to 11.3 kgCO2eq/FU. This result is competitive with the BFRP reinforced concrete beam that experiences 14.6 kgCO2eq/FU. These results highlight the environmental benefits to be
gained from precast BFRP reinforced concrete beams. It is likely that the future market for basalt rebar will be within the precast industry rather than in on-site construction. This is because the handling of thinner and lighter precast basalt reinforced concrete members will be quicker and easier to install on-site than steel. This is advantageous from an environmental perspective, since precast BFRP concrete beams experience approximately half the emissions of precast steel reinforced concrete beams.
Another core finding was that both the BFRP tendons and reinforcement steel have similar emission factors: 2.6 and 2.34 kgCO2eq/kg respectively. However, since BFRP has a lower specific weight to steel, and is three times lighter, the overall embodied emissions are much lower in the BFRP reinforced concrete beams. This is because less material (per kg) is required to perform the same function. When considered without concrete, the LCA results showed the largest contributor to BFRP emissions was resin (86.8%). It was therefore ascertained that the LCA results are sensitive to the type and quantity of resin used, and that the amount of embodied emissions arising from resin are a significant driver of high emissions in BFRP tendons. This finding highlights an area for optimisation in the future. BFRP manufacturers could therefore experiment with the
composition and quantity of resin required during the BFRP production process with a view to reduce embodied emissions. The development of new environmentally friendly resins could then be applied to all FRP composite materials.
In this study, the same quantity of concrete was used for both steel and BFRP reinforced concrete beam scenarios. It is thought that thinner concrete members could be implemented in the BFRP scenarios, since the mechanical results show that BFRP is much stronger than conventional steel reinforcement. This study highlights that BFRP is an advantageous construction material, and more specifically beneficial as a reinforcement material in concrete beams.
The study highlights that BFRP may also be suitable in other construction applications, such as prefabricated sandwich panels, that require thin concrete facades and thin structural cores. It is expected that using BFRP in thinner concrete sections will have similar, low environmental emissions compared to conventional steel reinforced concrete elements.
It is recommended that further work involves the investigation of thinner concrete members in BFRP reinforced elements, to find out which thickness is required for given performances. This body of work could help the future development of design guidelines and codes for BFRP in construction.