Very simple test showing the strength of Surecrete's Xtreme Series Precast Mix with and without Basalt Fibers. In this scenario, we have casted our XS Precast concrete countertop mix at 3/4 inch and tested it at a span of 4 feet. Basalt Fibers can be found here: Basalt fiber is a material made from extremely fine fibers of basalt, which is composed of the minerals plagioclase, pyroxene, and olivine. It is similar to carbon fiber and fiberglass, having better physic mechanical properties than fiberglass, but being significantly cheaper than carbon fiber. What this means for you as a weekend warrior casting his very own 14′ long kitchen countertop? Lighter casted concrete pieces with no seams! For those professional fabricators looking to create multiple precast pieces, the combination of Basalt Rods and AR Glass Fibers can help to make complicated install jobs a breeze by keeping pieces structurally sound while keeping casted concrete weight down to a minimum.