Study of the impact of the free lime in the clinker on the properties of the Portland cement [Etude de l'impact de la chaux libre du clinker sur les propriétés du ciment Portland]

During the production of the clinker in cement factories,it often happens that incidents which favor the production of the free lime. like an inappropriate dosage of the raw mixture,or defect of grinding or homogenization of the raw mixture,an instant shutdown of the oven,a reducing burning of the clinker or a slow cooling of the clinker. in order to determine the impact of the lime not combined in the clinker on the properties of the cement,we prepared cements from clinkers having increasing contents of free lime varying from 2.18,3.15,4.2,5.24 and 6.02 %. we realized several experiments by fixing the fineness of prepared cements: ssb = 3820 ± 50 cm2/g. these experiments showed that the content of water demand increases according to the increase of the percentage of the free lime,in more the expansion rises when the content of the free lime increases. the setting time also increases with the increase of the percentage of the free lime. moreover,the heat of hydration rises while the free lime increases. also the mechanical strength of 2,7 and 28 days decreases according to the increase of the free lime.