The Primary Study Of The Burnability Of Cement Raw Mixes With High Calcium

Increasing the content of C3S in cement is a best way of gaining high strength cement, but means the higher burning temperature. This paper is for finding a solution of the problem. We research the effect of foreign oxides on the burnability of high CaO cement raw mixes with the change of temperature und content of foreign oxides by XRD, SEM and DTA.According to potential mineral C3S=75% C3A=8% C4AF=17%,the based sample are mixed with chemical reagents, then added 2% oxide, and burnt at 1300℃ and 1400℃. We find the difference of the effect on burnability between lower and higher temperature by fCaO: (1) at 1300℃ CuO>Co2O3>ZnO>Li2O>Cr2O3>PbO> WO3 > ZrO2 > TiO2 > MnO2 > MgO > P2O5 > BaO > reference sample, at 1400℃ TiO2 > ZrO2 > WO3 > MnO2 > PbO > Co2O3 > MgO > reference sample > ZnO > Cr2O3 > P2O5 > BaO > CuO > Li2O. (2) the effects was concluded as following: Evidently positive in low temperature (1300℃) but no observably positive or negative in high temperature (1400℃); No markedly positive in low temperature but evidently positive in high temperature; remarkably negative in high temperature.We further study TiO2, WO3, BaO, LiO2 and CaF2 with different temperature und different contents by ethylene glycol method, XRD, SEM and DTA. We find: (1) TiO2, WO3 have good effect on burnability(1350℃), but they are bad at lower temperature (1300℃), for the TiO2 sample there is an optimal content, when the content exceed 2% the burnability go bad; Proper TiO2 contributes the formation and crystallization of C3S, but excessive TiO2 is adverse; The solubility of TiO2 is 1.7%, in excess of 1.7% TiO2 CaO appear. (2) CuO has evidently positive in lower temperature, but negative in higher temperature; With increasing of the content, for CuO the burnability become firstly bad, then better, the difference between 1350℃ and 1400℃ is that the extremum moves to the higher content; CuO favors the formation and crystallization of C3S; the solubility of CuO is 1.2%, but in excess of 1.2% no new phase appears. (3) Li2O, CaF2, BaO have evidently positive in lower temperature, but no observably positive or negative in higher temperature; for BaO and Li2O the burnability become bad with increasing of the contents; Li2O and BaO accelerate the formation of C3S at lower temperature, but at higher temperature prevent crystallization of C3S; Li2O narrows the temperature range of decomposition of calcium carbonate and make it decompose in higher temperature. The sample containing 4% Li2O shows two-step decomposition which has tendency to widen temperature range.At lower temperature foreign oxides mostly affect the property of liquid phase; at higher temperature mainly alter the structure of silicate mineral. Similar to the property of Si, foreign ions favor free CaO consumed; similar to the property of Ca, they prevent free CaO consumed.