The possibility of recycle Glass Reinforced Plastic industrial by-product Dust (GRPD) in cementitious materials was considered and the effect of GRPD addition on plastic and hardened properties of cement mortars was investigated. Results revealed that GRPD addition delays the setting time of cement paste, but the delay can be partially recovered by using a previously heated GRPD. Moreover, GRPD is effective in reducing the viscosity and yield stress of cement paste when used as a partial cement replacement. Replacing 5 - 10% of sand volume with GRPD causes an increase in autogenous shrinkage and deformability of mortars as well as a strong reduction in the mechanical performance. However, the risk of cracking induced by restrained drying shrinkage and capillary water absorption is significantly lower in the presence of GRPD. This decrease could involve enhanced durability of GRPD mortars, even if only in a supporting role.