The manufacture of hydraulic binders, and in particular of cements, consists essentially of a calcination of a mixture of carefully chosen and assayed raw materials also referred to as “raw mix.” The firing of this raw mix yields an intermediate product, the clinker, which, shredded with possible mineral additions, will yield cement. The type of cement manufactured depends on the nature and proportions of the raw materials as well as the firing method. There are several types of cements: Portland cements (which make up the great majority of cements produced in the world), aluminous (or calcium aluminate) cements, natural quick setting cements, sulfoaluminous cements, belitic sulfoaluminous cements, and other intermediate varieties. Since these families are not totally disconnected, it is preferable to describe them by their chemical and mineralogical components.
In the world of cement, it is common to use a specific notation to describe the components of a clinker or cement. Since the clinker is the result of a high-temperature calcination, the elements are essentially present in oxide form.
Regardless of the type of cement, a person skilled in the art will always be faced, during its manufacture, with a dual aim: ensuring the chemical stability of the mixture of raw materials and the heat stability of the method. Indeed, since the performance expected from the cement depends on the quantity and nature of the mineralogical phases synthesized during firing, it is crucial for the raw mix to contain the elements necessary for that synthesis and for the heat conditions of the method to lend themselves to the appearance and conservation of said phases. However, this dual requirement is not always easy to respect, since the chemistry of the raw mix influences how the method is conducted and the mineralogy of the cement depends on how the method is conducted. These difficulties have been largely empirically resolved through a slow evolution of the manufacture method for Portland cements. However, although the most recent industrial equipment meets the needs of large-scale production of Portland cements, it does not make it possible to separate the respective influences of the chemistry and conduct of the method.
USPTO Backgrounds
USPTO Backgrounds