This paper reports on an experimental program investigating the durability and mechanical properties of alkali activated slag concrete (AASC). The AASC was prepared using ground granulated blast furnace slag activated by high concentration alkali solution. The mechanical properties were determined by compressive strength and elastic modulus. The durability characteristics of AASC were measured using Ultrasonic Pulse Velocity (UPV) and permeable voids tests. The result showed that AASC developed a comparable strength to Portland Cement (PC) concrete over the short term. However, the material displayed an increase in voids, as well as a reduction of velocity over time. This could lead to the material displaying inferior performance over longer periods of time.