Reinforced concrete (RC) structures exposed to aggressive environments will deteriorate quickly and shorten their service life. Many developed and developing countries face the great challenge of deteriorating construction infrastructure, with investments worth trillions of dollars. According to Federal Highway Administration (FHWA) regulations, billions of dollars are spent each year repairing bridge deck delamination in North America. The development of an efficient bridge deck rehabilitation system is vital for the efficient management of such infrastructures. LIFE-365 is a worldwide used service life prediction model proposed by NIST and ACI 2001. It was found and understood from the literature that the service life prediction model LIFE-365 uses a two-phase model (corrosion initiation period and propagation period) to assess the remaining service life of RC structures. It was also found that LIFE-365 software assumes a constant value of six years for bare steel bars and twenty years for epoxy-coated bars for determining the propagation period. The recent mathematical models use three-phase models (corrosion initiation period + free expansion period + propagation period), which consider porous zone thickness and rate of corrosion to predict service life. The present study focuses on the accurate prediction of service life of RC structures exposed to harsh environments using LIFE-365 and a mathematical model proposed by T El Maaddawy and K Soudki in 2007. It was observed that LIFE-365 accurately predicts the corrosion initiation period; however, the free expansion period was assumed to be six years without considering the rate of corrosion and steel–concrete interface (SCI) properties. The free expansion period was calculated using T El Maaddawy and K Soudki’s 2007 model, considering the properties of SCI and the actual corrosion rate. It is necessary to use both LIFE-365 and T El Maaddawy and K Soudki’s 2007 model to accurately predict the service life of corroding RC structures.