Reactive powder concrete (RPC) has been proposed as barrier materials for the construction of engineered barrier in a low-level radioactive waste disposal site. The durability characteristics of RPC in such applications become paramount for the success of the containment of the wastes. The adverse environmental conditions at the disposal site could attack concrete barrier material and result in degradation of the material. Laboratory tests were conducted on RPC with various compositions to investigate the physical and durability properties of RPC. The effects of the addition of cement, silica fume, quartz powder, silica sand, steel fiber, and 2 levels of water-to-binder ratio (W/B = 0.25 and 0.30) on the properties of RPC specimens were investigated. Experimental results indicate that the long-term durability of RPC is significantly improved with the hydration of pozzolanic materials, which produces a very dense structure and thus exhibiting improved durability. The coefficient of permeability of RPC matrix determined using gas permeability apparatus demonstrated that RPC has much lower permeability than that of ordinary concrete. Heat-treating of concrete at 80°C accelerates the hydration process of RPC and shows enhanced physical and durable characteristics, as demonstrated by the chloride penetration test results.