Strengthening concrete by fiber reinforcement is a new trend nowadays. Glass is one of the materials that have the highest chemical durability in concrete. Chemically durable glass compositions in alkaline environment have been studied for 25 years by our group. SMZS (SrO-MgO-ZrO2-SiO2) system glass compositions possess high chemical durability in alkaline solutions. Further investigations show that recently discovered SMFMZS (SrO-MgO-FeO-MnO-ZrO2-SiO9) glasses exhibit better chemical durability when compared to the former one containing more SrO in the composition as a modifying oxide.