This research is a part of a wide and ongoing investigation performed on the use of Phragmites Australis Ashes (PAA) as partial cement replacement in mortar mixes. Replacing cement in mortar or concrete by bio-ash materials can be beneficial for the environment after the CO2 emissions due to cement manufacturing process have reached hazardous levels. PAA is burnt in a totally closed container where no CO2 is emitted to the atmosphere. So, PAA can be considered as an environmentally friendly material. This paper examines the mass change of mortar specimens exposed to dimensional stability tests such as drying shrinkage, autogenous shrinkage and expansion containing PAA as partial cement replacement. Cement is replaced by 0%, 10%, 20% and 30% (PAA) by weight with a constant water to binder ratio 0.55 and binder:sand ratio 1:3. The mass change due to drying shrinkage, autogenous shrinkage and expansion is monitored up to 28 days where the results showed a high potential for PAA to be used to partially replace cement in mortar or concrete. Different correlations between mass changes due to different dimensional stability properties are also examined. Results reveal that there is a high relationship between different mass change properties where high correlation coefficients are obtained.