This project’s aim will be to demonstrate the appropriateness of using high quality basalt fibres within the construction industry. More specifically, work will focus on establishing fundamental intellectual knowledge required to utilise chopped basalt fibres as micro reinforcement for both structural and non-structural concrete.
In its current transnational research strategy4, for example, the European Directors of Roads views ‘energy efficient materials and technologies’ as a core theme. Advised by a technical committee which monitors European research and advises on topical issues, a specific strategy focus is a need for: investigations into new materials; improvement of material durability by increasing the quality of materials used; and long term influence of new materials on operation, maintenance and recyclability. Similarly, part 3 of Horizon 20205 – the new €70 billion EU framework programme for research and innovation from 2014-20 – focuses on smart, green and integrated transport. This includes a next-generation infrastructure strand focussing on resource efficiency; reduced maintenance; and market up-take of innovative infrastructure solutions.
Conventional concrete does not align well with this future vision for the built environment. Concrete is inherently weak in tension. Its ultimate effectiveness is governed by its response and resistance to tensile stresses arising from drying, impact, bending and/or temperature. The standard approach to addressing this shortcoming is use of mild steel reinforcement; an approach highly susceptible to premature corrosion and associated maintenance costs. The Corrosion Society has estimated this cost to be approximately $125 billion per year in the US alone. Concrete’s other major shortcoming is that its production accounts for 5% of all annual anthropogenic CO2 produced globally. As such, routes to reducing the environmental and maintenance impacts of concrete are in high demand.
According to Professor Scrivener6, head of the construction laboratory at the Swiss Federal Institute of Technology in Lausanne, the concrete industry needs to reinvent itself by developing ultra-strong and resilient varieties, so effectively less material is required to do the same job. Basalt fibre use is proposed as a key contributor to this challenge.
Basalt fibre manufacture involves melting quarried basalt rock at about 1,400°C and extruding the molten material to produce continuous 9-13µm diameter fibre filaments. Basalt fibres are both naturally lightweight and strong; exhibiting similar strength as steel in certain applications. They are inherently resilient to chemical, abrasion, impact and high temperature exposures. The cost/performance benefits of basalt fibres are already being explored and exploited in other sectors, such as the aeronautical and renewable energy industries. This project’s endeavor will be to transfer this knowledge to the construction sector and, in doing so, begin to develop innovative commercial markets internationally.
Based on preliminary findings, performance benefits offered by the use of basalt fibres in concrete include: inhibition of intrinsic early-age plastic shrinkage and settlement cracking; increased cohesion and impact resistance; reduced segregation, settlement and bleeding; and reinforcement against abrasion and freeze/thaw damage.
The initial target market for chopped basalt fibres is the mass ready mixed and precast concrete sectors. Concrete is ubiquitous and undeniably mankind’s major construction material. Globally, over 2 billion tonnes are consumed annually. By 2050, concrete use is predicted to reach four times the 1990 level. In the UK, consumption of ready-mixed and precast concrete is around 23 million cubic metres and 38 million tonnes respectively. Water is the only worldwide resource consumed in greater volumes.
Fibre use in construction materials is not a new phenomenon. Egyptians used straw to reinforce mud bricks and evidence exists that asbestos fiber was used to reinforce clay posts over 5000 years ago. In concrete today, polymer and steel fibres are commonly used, although not without performance limitations such as performance in high temperature and corrosive environments. Despite this, yearly consumption of fibers in concrete is reported7 to be in excess of 300,000 tons and growing. In North America alone, the yearly fibre market growth rate is around 20%.
With ever increasing demands to strengthen existing reinforced concrete structures to facilitate higher performance levels and extended service lifetimes, it is proposed that basalt fibres have a key role to play. Potential applications are limitless, including industrial floors, tunnelling, mining, security structures and heavy duty pavements; in fact anywhere where conventional reinforcement systems are often impractical.
School of the Built Environment
University of Ulster