At present, reducing the environmental impact of the construction industry is a major subject of study. In terms of the use of recycled concrete aggregates (RCA), most recently conducted studies have shown that the use of a limited percentage of those aggregates does not significantly affect the properties of concretes. This work analysed the mechanical properties of medium-strength concretes with a high contribution to sustainability, where cement and natural coarse aggregates (NCA) were partially replaced by volcanic powder (VP) and RCA, respectively. Three mixing ratios of VP replacement were tested in concretes without RCA and concretes with 30% RCA replacing NCA. Results show that when VP is used without RCA, up to 10% of the cement can be replaced by VP without a significant loss in the mechanical properties. When a combination of 5% VP and 30% RCA is used, the weakness of the recycled concrete is strengthened, obtaining stronger concretes than a control concrete with no recycled materials. Finally, the greenhouse gas assessment showed that the simultaneous incorporation of VP and RCA reduces CO2 emissions produced in the manufacture of concrete by up to 13.6%.