Use of environmental friendly materials in concrete to make concrete sustainable is gaining importance, as the growth of the construction sector is rapid and massive in India. Such a sustainable concrete is the geopolymer concrete with scrap steel slag coarse aggregate. The concrete replaces cement and natural coarse aggregate by fly ash and scrap steel slag. Mechanical Strength of the concrete of M20 grade was evaluated and found suitable. Concrete strength has no role without the concrete being durable. Experimental tests were carried out to check the durability of the concrete and the results are presented in this paper. M20 grade geopolymer concrete with scrap steel slag coarse aggregate was tested after ambient curing for 28 days and the results are compared with M20 grade cement concrete with conventional Coarse aggregate. Durability was checked based on Water absorption, Acid resistance, Sulphate resistance and Sorptivity. The experimental results indicate that geopolymer concrete exhibit excellent durability than conventional cement concrete.