In today’s scenario, construction equipment plants are essential for any construction projects and are also important for rapid progress and improvement in the quality of work. Breakdown and less productivity of equipment can increased the cost of construction project. Hence it is important that attempts to be made to increase the productivity of equipment. Earlier research has often addressed this fact, but it has rarely explained the causes and consequences of downtime. Thus this research paper highlights various causes of downtime of RMC plant and Transit Mixer. Also the downtime cost of RMC plant and Transit Mixer (TM) is determined by using mathematical model, COX Model and NUNALLY Model. These models are used to identify the downtime cost of equipment where COX Model gives the value by only taking into account of failure machine and not considering the impact, while the NUNALLY Model gives higher value due to considering the overall impact of failure machine on work.