This study intended to enhance the mechanical properties of cement with less clinker content through the addition of composite admixtures (JT-GA), and decreasing the amount of CO2 released in cement production. In this investigation, the effects of incorporating JT-GA on the grinding efficiency, setting time, standard water demand, mechanical properties, hydration heat, and hydrates of cement samples, P80-1-0 (80% clinker, H19-GA), P74-1-0 (74% clinker, 0.05% H19-GA), and P74-1-1 (74% clinker, 0.05% H19-GA and 0.1% JT-GA), were examined. Results indicated that the mechanical properties of cement with less clinker (P74-1-1) were significantly improved through the addition of JT-GA. Compared to cement with 80% clinker content (P80-1-0), the compressive strengths at 3 d and 28 d were increased by 6.5% and 11.3%, respectively. This improvement was attributed to the use of JT-GA, which leads to a more uniform particle size distribution in cement with reduced clinker content and significantly promoted the dissolution of Fe3+ and Al3+ ions from ferric phases to react with aluminates, thus facilitating the formation of Hc/Mc, leading to the stabilization of ettringite. This further reduced porosity and increased the compressive strength. Additionally, the incorporation of JT-GA had minimal impact on the setting time and water demand for normal consistency of cement with reduced clinker content. © 2024 Bauverlag BV GmbH. All rights reserved.