Takumi Harada;Hisanobu Tanaka;Makio Yamashita;
<正>Cement manufactures today use various waste materials and by-products as instead of raw materials and fossil fuel in order to promote recycling because of the shortage of final disposal sites for such materials and the need to preserve natural resources in Japan.However,these waste materials and by-products sometimes contain chemicals that differ from conventional raw materials and fuels and might affect the properties of clinker and cement.We studied the overall influence of several minor components in clinker on the properties of clinker and cement.In this study,we investigate the influence of Lanthanum oxide(La_2O_3) and Cerium oxide(CeO_2) on various properties of clinker and cement.La_2O_3 and CeO_2 have not been studied extensively in cement manufacturing because they exist only as trace elements in raw materials and cement.La_2O_3 and CeO_2 are present in the grinding sludge from the semiconductor industry.This sludge is increasing thanks to favorable solar battery and liquid crystal panel developments. Laboratory clinker and cement with a maximum of 3%La_2O_3 and 3%CeO_2 in the clinker were burned in an electric furnace using raw meal and commercially available reagents.No noticeable difference in the mineral composition was detected with an increase in La_2O_3 and CeO_2 in the clinker except Ceria(single phase of CeO_2) formation in the high CeO_2 content clinker.Both of these components concentrate in clinker interstitial areas.Increasing La_2O_3 and CeO_2 in clinker delayed the setting time of cement and reduced the compressive strength of the cement for all cement ages.Also, La_2O_3 and CeO_2 in clinker had similar influences on cement properties.This can be attributed to the suppression of the hydration reactivity of silicate due to the solid dispersed La_2O_3 and CeO_2 in the clinker. Originality The influence of La_2O_3 and CeO_2 in clinker on cement properties has not been studied because they are present only as trace elements in conventional raw materials.Our study benefits cement manufactures by maintaining cement quality and promoting recycling since the amount of waste such as grinding sludge from the semiconductor industry,which includes significant amounts of these components,has recently increased.We clarified the extensive influence of these components on the properties of clinker and cement and its essential principles.La_2O_3 and CeO_2 influences on cement properties are almost equivalent to each other under the equimolar condition,and we proposed that both amounts should be managed to safely maintain the quality of cement. Our extensive and realistic approach to understanding the properties of clinker and cement will be applied to commercialization in cement plants.
Lanthanum oxide;;Cerium oxide;;Cement clinker;;Mineral composition;;Setting time;;Compressive strength;;Hydration reactivity
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