Active C 2S Cement from Fly Ash and Kiln Dust


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Title: Active C 2S Cement from Fly Ash and Kiln Dust

Author(s): A. Xu and S. L. Sarkar

Publication: Special Publication

Volume: 153


Appears on pages(s): 213-228

Keywords: clinker; C 2S; gypsum; strength; Materials Research

Date: 6/1/1995

As focus increasingly shifts to protecting the environment through recycling of industrial byproducts and wastes, as well as conserving energy and resources, corresponding restructuring of conventional production technology and practices has become imperative. Because of these considerations, mixtures of kiln dust and fly ash were hydrothermally treated and calcined to produce a new type of beta-C 2S rich cement. Fly ash, which is the most abundantly generated industrial byproduct, is still largely disposed of as waste; kiln dust is the waste product of the cement industry, vast quantities of which are discarded due to its high alkali content. The former is composed of alumino-silicate glass, while the latter has a composition similar to that of partially calcined cement raw meal. This study demonstrates that it is possible to produce C 2S cement of dequate 28-day strength by suitably proportioning fly ash and kiln dust. The results of variations in factors such as the CaO:SiO 2 ratio and two different precalcination treatments are presented. Prehydration-dehydration (sintering at 950 C) processes were specially applied for the production of this cement, in contrast to the direct calcination method in the presence of a mineralizer. The cement was constituted of beta-C 2S and calcium aluminates. The formation of these minerals in relation to the clinkering sequence is discussed. The cement is sufficiently hydraulic, and its strength development largely depended on the CaO:SiO 2 ratio of the raw mix and the precalcination process.