In order to clarify the durability performance of cement composites, it is necessary to simulate mass transport properties, and in this case, it is important to take into consideration the heterogeneity of the hardened cement. In this research, the connectivity of transition zone, which is effective factor for mass transport properties, was expressed by the “burning algorithm”. As a result, the sand amount that brings about the rapid increase in the connectivity depends on water cement ratio. And using the coefficient of mass transport and percolation theory. we simulate the mass transport properties in 3-D. Comparing the analytical results with experimental results, this simulation may be effective to evaluate the real condition of mass transport properties.