Journal of Applied Sciences1812-56541812-5662Asian Network for Scientific Information10.3923/jas.2011.584.588MajeedSura A.32011113It is well known that the strength of any tested matrix materials like concrete or mortar is affected by the specimen size; therefore it is important to consider the effect of specimen size when estimating the ultimate strength of such materials. This study presents the effect of specimen size on the mechanical properties of cement mortar. These include the compressive, splitting strength and modulus of rupture. For the compressive strength three different sizes of cylinder and three sizes of cubes are used and the same sample sizes are used for testing the splitting strength. Also three different sizes of specimen are used for modulus of rupture. Preparation, casting and testing procedures are carried out according to ASTM specifications using constant mix proportion of cement/sand and water cement ratio. The obtained results show that the three mechanical properties of mortar affected by the specimen size specially the compressive strength and splitting strength of cylinders. Some best fit relationships that relate these properties are presented in this study although it cannot be generalized due to the fact that the presented results are based on limited number of tested specimens with constant mix proportion.]]>ASTM C-33,1978ASTM C 496,1996ASTM C-39-01,2001ASTM C-109-02,2002ASTM C-78,2002Bazant, Z.P.,1984Bazant, Z.P., Y. Xi and S.G. Reid,1991Bazant, Z.P. and Y. Xiang,1994Bazant, Z.P., Y. Xiang and S.G. Reid,1997Cotterell, B.,1972Gonnerman, H.F.,1925IQS No. 5,1984Jen, Y.S. and S.P. Shah,1991