This thesis investigates the carbon emission of CO2. Produced by the construction of the building structure and how we can reduce it by using the SCM materials like Fly ash. Using ETABS and safe Software, a series of detailed modelling were performed on a set of different strengths with different fly ash substitution were modeled and design. Concrete Strength parameters were varied for each Class of concrete starting from C25/30, C33/40, C40/50, C50/60. Also, Young Modulus For each Class were updated and after getting the results of these models without any fly ash substitutes we developed more models with 5,10,20,30 and 80 percent fly ash and with that ratios we used equation from Fanelli research and get the fck and E and update on new models and run those models and get the total Reinforcement volume As and total concrete quantity Ac.