Initial time of cracking ocurring in restrained shrinkage under dry condition of mortar and electrical resistivity of cement pastes with different alkali and admixtures were tested using a multicenter ellipse ring apparatus with an automatic monitoring system and a non-contact resistivity meter, respectively. Besides, compressive and flexural strength of mortar under dry curing condition were also determined. Experimental results show that alkali(R_2SO_4) accelerates hydration process of cement with or without fly ash or shrinkage-reducing admixtures(SRA) or water-reducing admixtures, and enhances the strength development of corresponding mortar but also shortens greatly the initial cracking time, especially under lower water-cement ratio and with water-reducing admixtures. However, fly ash or SRA is capable of resisting drying shrinkage crack and reducing strength development of mortar at early ages, because fly ash or SRA may retard the hydration and hardening process of cement, especially for cement-based materials with high alkalinity.