Production optimization of composite cements with low environmental footprint

Various strategies are applied in order to reduce the green-house gas-emissions, such as optimizing the process of clinker production, the use of alternative fuel and the partial substitution of the clinker in composite cements by the so-called supplementary cementitious materials (SCM). Currently, the most suitable SCMs from the available materials are semi-hydraulic or pozzolanic materials such as granulated blast-furnace slags (herein "slag") and fly ashes from coal combustion process [1]. Application of, limestone, is limited because of its little contribution on the performance [2]. Ternary systems (herein "composite cement") simultaneously containing more than one SCM besides Portland cement clinker contribute to the reduction of CO2 emissions due to further decrease of the clinker content. Recent research work on quaternary systems revealed that use of slag and fly ash in combination with limestone may lead to the further increase of the cement clinker replacement ratio [3] [4]. The main processes taking place during the hydration of Portland cements (OPC) are well understood. In contrast, the hydration of composite cements are more complicated. As both, part of the Portland cement and the added SCMs react simultaneously. This leads to their interaction and thus influencing the reactivity of each other. HeidelbergCement launched the research program aiming at the understanding of the parameters that allow maximizing the clinker replacement by slag and limestone while keeping adequate cement performances. Understanding the interactions between the reacting clinker, slag and limestone [4] [5] allowed the development and the optimization of production methods of the composite cements at a clinker replacement of up to 50%. These efforts have led to the establishment of the know-how allowing the optimization of the cement composition and properties. During the Endurcrete project (EU funded project Horizon 2020), the methods of optimization were used to produce composites cement with low environmental footprint for improved durability. This contribution presents the optimization of the multicomponent cement for this purpose maximizing the cement performance evolution while minimizing its environmental impact.