Towards sustainable high-strength concrete: A ternary blend of alternative cementitious materials

• A novel ternary blend of FA, MK, and SF was used to partially replace OPC in high-strength green concrete. • The ternary mix (25% FA, 10% MK, 5% SF) achieved the highest compressive strength (76 MPa at 90 days). • Tensile (4.6 MPa) and flexural (5.7 MPa) strengths were maximized at 28 days in the ternary mix. • SEM and XRD analyses confirmed a denser, more uniform microstructure with reduced porosity. • The synergistic effect of cementation material enhanced hydration, matrix compactness, and long-term durability. Due to its massive carbon footprint, the construction industry urgently needs sustainable alternatives to ordinary Portland cement (OPC). This study investigates a novel ternary blend (Mtb) of industrial byproducts and processed materials: 25% fly ash (FA), 10% metakaolin (MK), and 5% silica fume (SF) as partial OPC replacement to develop high-strength green concrete (HSGC). The research combines experimental testing and microstructural analysis to evaluate the blend's effects on mechanical properties: compressive strength at 7, 28, and 90 days, tensile and flexural strength at 28 days. Microstructural evolution was examined using scanning electron microscopy (SEM). Results showed that the ternary blend (Mtb) had the maximfum compressive strength at 90 days, reaching 76 MPa, followed by M(sf+mk), the SF and MK mixture (5% SF + 10% MK + 85% OPC), at 75 MPa, and M(sf+fa), the SF and FA mixture (5% SF + 25% FA + 70% OPC), at 70 MPa. At 28 days, Mtb achieved the highest tensile strength (4.6 MPa) and flexural strength (5.7 MPa). These gains are due to SCMs' synergistic interaction, increasing matrix density, and crack resistance. According to SEM, SF and MK significantly densified the microstructure, reducing porosity and enhancing hydration product uniformity. FA's delayed pozzolanic activity contributed to pore refinement over time. Of all mixes, the ternary mix (Mtb) had the most uniform and compact matrix. These findings suggest that combining SF, FA, and MK in proper quantities can yield long-lasting, high-performance concrete with enhanced mechanical properties, microstructural integrity, and durability.