Systematic assessment of the technical performance, durability, cost, and environmental impact of sustainable concrete incorporating fly ash and ground granulated blast-furnace slag

River sand (RS), the main fine aggregate used in the manufacturing of mortar and concrete, has been chronically and seriously limited in availability in recent years. Additionally, numerous unfavorable problems with cement manufacture and use have been documented thus far. Given the aforementioned, identifying viable, alternative sources is essential to promoting the construction industry's sustainable growth. This study was developed to systematically assess the effect of fly ash (FA) as a replacement for RS (20–60 vol.%) and ground granulated blast-furnace slag (GGBFS) as a substitution for cement (30 wt.%) on technical performance, microstructure, cost, and environmental impact of concrete. The resulting concrete exhibited increased compressive and flexural strengths up to 56.2% and 60.1%, respectively. Importantly, the proposed mixtures also offer both cost advantages and environmental benefits by reducing the total cost, CO₂ emission, and energy consumption per unit strength of concrete. These findings underscore the respective potential of FA and GGBFS as sustainable alternatives to RS and traditional cement. Incorporating these two industrial by-products delivers improved mechanical properties and enhanced durability (in terms of resistivity, ultrasonic pulse velocity, porosity, chloride permeability, water absorption, and drying shrinkage), promotes sustainable development in the construction industry, reduces environmental pollution, and conserves natural resources.