Susan Taylor, of the Queen's University, Belfast, received a grant from the UK Department of Transportation to implement a large bridge span employing reinforcing members made not from the steel we normally use, but frmo basalt fiber reinforced polymer (BFRP), a material made by melting igneous rock and extruding it into the required fiber shape. Rock fiber is not a new building material: Roxul is a commercially available insulation made from spun mineral wool, a byproduct of ore smelting. What's new in this case is its addition to load-bearing concrete structures.
BFRP is very corrosion resistant, and has an extremely high tensile strength -- approximately twice that of steel. It also costs about 40% less than stainless steel rebar, making it an ideal candidate to reinforce stainless in areas where corrosion factors significantly into the structural design. Glass fiber is also used as a reinforcing component in these cases, but BFRP outperforms it, costs about the same, and weighs 75% less. BFRP does cost about three times what common steel rebar does, so don't expect its use to be ubiquitous.
For more information, read the Engineering News-Record article.