Glass fiber reinforced concrete (GFRC) is concrete that relies heavily on the use of glass fibers to provide strength. These are different from the fibers commonly used in precast and site cast concrete to control shrinkage cracking. Those fibers, typically polypropylene or nylon, are neither stiff nor strong enough to provide significant tensile strength to uncracked concrete. GFRC, in contrast, uses massive doses of AR glass fibers to provide crack control and actual tensile strength. The doses are about 30 to 80 times that of regular concrete.
Learn more about concrete countertops from Jeff Girard, PE, in TH25 Concrete Countertops: Step-by-Step Instructions Using GFRC.