In the last few years, due to the urgent need for reducing the amount of greenhouse gas emissions mankind is looking for the ways to construct the buildings with higher efficiencies in using resources and providing a convenient environment for living. Therefore in the last few decades, thermal storing systems are being used to solve this problem. Using smart materials which is known as Phase Change Materials (PCM) is one of many ways for reducing the thermal load of the buildings. This kind of materials stores the unwanted amount of latent energy in the freezing and thawing processes and release the back whenever it's needed. They can be used in many ways, one of which is suspending the constructing elements in them. In this research, two forms of phase change materials have are used. The commercial names are polyethylene glycol and salt hydrate. Aggregates were immersed in these materials and then been used to make the concrete. in this paper, the effect of phase change materials on the thermal and mechanical characteristics of concrete, long term and short term water absorption, thermal conductivity factor and the effect of them on the hydration process has been analyzed. Furthermore the effect of adding silica fume in the concrete specimens which were already under the influence of PCM has been examined. 26 mix designs have been tested. The results showed that using PCM in the mixes affects the hydration process and causes the resistance to decrease, but adding silica fume to the mixture minimizes this reduction. The tests showed that if the specimens contain PCM, the changes in the short and long term water absorption and the thermal conductivity factor are obvious. following these findings in the research, there is a whole section about analyzing the result of tests on the thermal performance, thermal mass and other thermal characteristics. Moreover, the results show that there is a need for using the calculation in unsteady states in replacement of common steady states. While testing the thermal performance, it was clearly found out that by using the PCM the thermal performance undergoes a significant improvement in a way that not only it leads to decrease in maximum temperature, but also it causes an amount of delay before reaching the maximum temperature which is a clear indication that using these materials in construction will lead to a significant decrease in power consumption. Key Words: Concrete, Phase Change Materials (PCM), Silica Fume, Scoria, Compressive Strength, Test Semi-adiabatic, Water Absorption of Short-term and Final, Thermal Conductivity, Thermal Performance.