Natural pozzolan as a sustainable cement replacement in high-performance concrete: Effects on mechanical properties, durability, and microstructural development

Abstract

High-Performance Concretes (HPC) play a crucial role in contemporary construction due to their exceptional strength and durability. However, the necessity for high cement content leads to considerable environmental and economic concerns. Consequently, there is an urgent need to explore more eco-friendly alternatives that can sustain the performance of HPC while meeting technical, economic, ecological, and sustainability requirements. One viable option is natural pozzolan (NP), which is abundantly available in many regions and can serve as a partial replacement for cement. . Algeria, for instance, has abundant and low-cost NP, which can significantly decrease clinker demand and enhance eco-concretes' performance. Our objective is to assess how partially substituting cement with NP with a replacement rate ranging from 0 % to 50 % affects the physical, mechanical behavior, and durability of Eco-HPC made with ternary binders. Experimental results indicate that eco-HPC, which includes up to 20 % NP, shows good performance. After 28 days, it achieves a compressive strength of 63.8 MPa, slightly lower than the control HPC's 68.5 MPa. In addition, its long-term strength development reached 84.4 MPa at 180 days compared to 78.2 MPa for the control HPC. Furthermore, the 20 % pozzolan mix demonstrates 15 % less total shrinkage at 180 days and a 25 % decrease in capillary water absorption when compared to the control mix, while retaining adequate workability. These results support the potential of using ternary binder systems with NP in creating eco-friendly HPC, achieving a good balance between environmental advantages and improved durability.