Effect of multicomponent mineral additives on the microstructure and strength of composite cement

In the face of growing environmental and energy challenges, the cement industry is shifting towards the use of composite Portland cements containing hybrid mineral additives to reduce clinker consumption and CO₂ emissions. This study investigates the pozzolanic activity and hydration behavior of thermally activated aluminosilicate additives (TAFM), quartz-feldspar sand, apobasalt-orthoshale (APO), and limestone. The chemical composition and calcium oxide binding capacity of each component were examined using the lime saturation method. Results showed that TAFM exhibits the highest pozzolanic reactivity, significantly binding free lime (CaO), followed by APO and limestone. Composite cement mixtures were formulated according to GOST 31108–2020 standards, incorporating 20% hybrid additives. Mechanical tests revealed that such compositions improve long-term compressive and flexural strength, early setting times, and structural density. In particular, the combination of TAFM, APO, and limestone showed synergistic effects in enhancing hydration kinetics and final performance. The findings support the feasibility of using local mineral resources as effective components in sustainable cement production and highlight the benefits of hybrid additives in reducing clinker demand while improving mechanical and durability characteristics of cementitious composites.