Introduction: The paper addresses the effect of a composite modifying mineral additive based on waste — tailings from the Balkhash Mining and Processing Plant — and microsilica on the structural characteristics and performance of heavy concrete. Purpose of the study: We aimed to select optimal B25 and B35 concrete mixes based on the MV-D20 modified binder with the composite additive in its composition and evaluate the characteristics of concrete. Methods: In the course of the study, standard methods were used to design concrete mixes and test the characteristics of concrete. Proportioning was performed in accordance with State Standard GOST 27006-86 “Concretes. Rules for Mix Proportioning”. The physical and mechanical properties of heavy concrete were determined in accordance with State Standard GOST 10180-2012 “Concretes. Methods for Strength Determination Using Reference Specimens”. The strength of concrete was assessed in accordance with State Standard GOST 18105-2018 “Concretes. Rules for Control and Assessment of Strength”. Results: It was established that in terms of the rate of strength gain, the designed heavy concrete mixes are fast-curing. In the initial curing period of 7 days, B25 and B35 concretes gain 90.1 and 85.4% of the required standard strength, respectively. The average values of water absorption in B25 and B35 concretes are 4.20 and 3.46%, respectively. In terms of water tightness, concrete mixes have W10 and W12 grades. The application of the MV-D20 modified binder with the composite additive consisting of tailings and microsilica instead of standard sulfate-resistant Portland cement will reduce the relative deformation of B35 concrete in an aggressive environment by 12%.