In Delhi, according to CPCB, solid waste generation is predicted to be 43.5 million metric tonnes/year. In that, the waste generated from the construction industry is considered to be about 13.6 million metric tonnes. These solid waste materials formed by demolished structures are discarded by dumping them as landfills or disposal areas. Relinquish of this solid wastes is causing scarcity of disposal areas in urban areas. Hence, it's essential to start re-using and recycling waste demolition concrete to save lots of money, energy, and the environment. Employing recycled coarse aggregates assists in sustainable and economic growth through recycling. Durability parameters of Recycled Aggregate Concrete (RAC) are considered in this research to find out the optimum quantity of recycled aggregates which acts as a replacement for natural aggregates and finding out the mathematical equation by Analytical Modelling. Fly Ash here is employed as a replacement for cement without affecting its strength of concrete. This experimental investigation includes various durability tests viz. Water Absorption test (WAT), Abrasion Test, and Compressive strength. Recycled aggregate concrete of M50 and M60 grades with 0, 20, 40, and 60 % substitute of natural aggregate with recycled concrete aggregates along with 25% of cement is substituted by Fly Ash. The tests were executed at 28 days and 56 days of curing. From the above durability test, Mathematical modeling has to be found out to study concrete durability. Analysis and correlation were done by MLR (Multiple Linear Regression). The equations are formed of all three tests with their regression graph. So this research assists in the use of recycled aggregate concrete in the construction sector.