Basalt, Holy Grail of bridges?



Climate conditions make life hard for our road infrastructure, sending engineers and scientists on a continuous quest for the Holy Grail of materials that will combine durability with high performance. One possible candidate: fibres of basalt, impregnated with a polymer matrix. Lightweight and resistant to corrosion, they have a lifespan of more than 100 year! Basalt fibre has been on the market for several years, but building codes provide no recommendations for its use due to a lack of scientific data. This problem has been rectified by Mathieu Robert, professor in the Department of Civil Engineering at Université de Sherbrooke.

Basalt fibre lasts twice as long as steel, which can cause concrete to corrode and crack after only 20 years.

The researcher analyzed the properties of basalt fibre composites, showing them to be better than fibreglass composites, at a similar cost. Among the advantages of basalt fibre are its tensile strength—the ability to be stretched without breaking—which is about 20% greater than that of fibreglass. Furthermore, basalt fibre lasts twice as long as steel, which can cause concrete to corrode and crack after only 20 years and must be replaced after 50 years. Basalt fibre is also significantly cheaper than carbon fibre. The verdict: basalt fibre is an excellent option for replacing the steel bars used to reinforce concrete in bridges, for example.

However, basalt needed a little help from science. Mathieu Robert and his team corrected a few flaws found in the rocky fibre. In particular, they modified the surface chemistry of the fibres in order to increase their adherence to resin, increasing the long-term durability of the composite. Other research teams are now studying the behaviour of bridge deck units reinforced with basalt, where durability and performance are paramount, for both safety and cost-effectiveness!