The lack of knowledge on the long-term behaviour of Fabric Reinforced Cementitious Matrix (FRCM) composites limits their confident use in structural rehabilitation. Despite the scientific literature on this issue is continuously growing and the requirements set by certification guidelines include tests on aged specimens, more research is still needed to gain an improved understanding on the durability of mortar-based systems, especially when the fabrics are particularly sensitive to alkali attack, as in the case of glass and basalt, due to the alkaline nature of the mortar matrix. This paper presents a laboratory investigation on an FRCM composite developed for the strengthening of masonry structures, consisting of a bidirectional basalt mesh embedded in a lime-based mortar. The ultimate tensile strength of dry textiles and FRCM prismatic (coupon) specimens was investigated after artificial aging in 0.16% wt Ca(OH)2 aqueous solution, for durations ranging from 1000 to 9000 h and at either 23 ℃ or 40 ℃ temperature. Test results showed that the considered basalt textile is vulnerable to alkali attack both alone and embedded in the mortar and that the temperature plays a key role in its chemical degradation.