In promoting sustainability in concrete, Effective Micro-Organism (EM) has been used in construction industry for the last few years. The aim of the study is to assess the effect of EM on the properties of concrete including fresh, hardened, durability and temperature variation in concrete. The research is based upon the addition of 5%, 10%, 15%, 20%, 25% and 30% of EM by replacing water in the concrete mixture. Concrete cube samples with the size of (100 x 100 x 100) mm were prepared and tested at the age of 3, 7, 14 and 28 days. The curing method was employed by water curing. Laboratory tests that had been done include temperature variation test, density test, Ultrasonic Pulse Velocity test, Initial Surface Absorption Test (ISAT) and compressive load test to assess the effects of effective micro-organisms in concrete. Results showed that compare to control sample the EM sample offered better performance in terms of all tests conducted. Using 10% of EM in sample recorded the highest compressive strength and also the lowest water penetration. It also increased the early strength of concrete significantly. On the other hand, the use of 15% of EM in concrete shows the lowest temperature rise during hardening of concrete. In conclusion, the addition of EM in concrete shows a positive effect on properties of concrete especially in temperature and durability
