 Cysil has been reported as a potential material for use in cement-based composites. However, its performance in these composites has yet to be fully explored. This study examined the effects of Cysil fiber content on the properties of SFRC and SSFRC, including water absorption, rapid chloride permeability, and acid attack. Results showed that Cysil fiber content had a significant effect on all three properties. Water absorption was significantly higher in SFRC than in SSFRC, while both materials experienced similar levels of rapid chloride permeability and acid attack. Additionally, Cysil fiber content had no effect on the compressive strength of either material. Overall, this study suggests that Cysil fiber may not be suitable for use in cement-based composites due to its high water absorption rate and lack of resistance to rapid chloride penetration and acid attack. This article was authored by Srimavasa Rao Naraganti.