Abstract: Industrial solid waste (ISW)–cement blends have the advantages of low carbon, low energy consumption, and low pollution, but their clinker replacement level in low carbon cement is generally low. To address this challenge, this study considers the latest progress and development trends in the ISW–cement blend research, focusing on the activation of ISWs, the formation of ISW–cement blends, and their associated hydration mechanisms. After the mechanical activation of ISWs, the D₅₀ (average size) typically drops below 10 µm, and the specific surface area increases above 350 m²/kg. Thermal activation can increase the glassy-phase content and reactivity of ISWs, where the coal gangue activation temperature is usually set at 400–1000°C. Furthermore, the roles of ISWs in the hydration of ISW–cement blends are divided into physical and chemical roles. The physical action of ISWs usually acts in the early stage of the hydration of ISW–cement blends. Subsequently, ISWs participate in the hydration reaction of ISW–cement blends to generate products, such as C–(A)–S–H gels. Moreover, alkali activation affects the hydration kinetics of ISW–cement blends and modifies the proportion of gels. Environmental impacts and costs of ISW–cement blends have also been discussed to guide stakeholders in selecting sustainable ISWs.