ADVANCES IN ORDINARY PORTLAND CEMENT CLINKER: REDUCING THE ENVIRONMENTAL IMPACT OF THE PRODUCTION PROCESS

Ordinary Portland cement (OPC) clinker production process has a remarkable environmental impact in terms of energy consumption, raw materials exploitation and greenhouse gases emissions. The present thesis deals with advances in the characterization and formulation of OPC clinker raw meals, the limestone and clay minerals mixture that is thermally treated in the rotary kiln to obtain cement clinker. The purpose is to better understand some key points of the clinkerization, in order to reduce the environmental impact of the production process. First, the influence of limestone petrography and calcite crystals microstructure on the OPC clinker raw meals burnability was investigated. Starting from eight natural limestone samples, similar from a mineralogical and chemical point of view but very different concerning texture and diagenetic history, a reliable parameter linking the limestone features to the OPC clinker raw meals burnability was found. Then, for the first time the influence of different minor elements combinations on the clinkerization process was investigated, starting from an industrial raw meal instead from chemical reagents as in previous studies. This will allow to transpose results from the laboratory to the actual production process. Finally, an heterogeneous and unconventional raw meal configuration was tested: clay minerals were replaced by basalt and both coarse- and fine-grained limestone fractions were used, leading to very promising results in this still relatively unexplored field. These three topics were selected because held to be among the most relevant within the global framework to reduce the OPC clinker production process environmental impact. Moreover, they were studied separately but they actually interact with each other at the industrial scale.