A comprehensive study on the influence of a shrinkage-reducing admixture (SRA) on properties of ordinary Portland cement and shrinkage-compensating cement has been conducted. The properties investigated include: electrical resistivity, hydration heat rate, free shrinkage and restrained shrinkage cracking. It is found that the shrinkage-reducing admixture (SRA) can reduce the free shrinkage and postpone the occurrence of shrinkage crack significantly. The SRA has also an effect to retard the hydration process of Portland cement under normal condition. However, under semi adiabatic condition, it seems that SRA accelerates the hydration process. A new concept of the hardening ratio, ρ H , is proposed in the study. It is indicated that the hardening ratio, ρ H , and compressive strength development have very good linear relationship.