The present investigation deals with how minor elements (their oxides: MgO, Na2O and SO3) in industrial kiln
feeds affect (i) chemical reactions upon clinkering, (ii) resulting phase composition and microstructure of
clinker, (iii) hydration process during cement production.
Our results show that all these points are remarkably sensitive to the combination and interference effects
between the minor chemical species mentioned above.
Upon clinkering, all the industrial raw meals here used exhibit the same formation temperature and amount
of liquid phase. Minor elements are preferentially hosted by secondary phases, such as periclase. Conversely, the
growth rate of the main clinker phases (alite and belite) is significantly affected by the nature and combination
of minor oxides. MgO and Na2O give a very fast C3S formation rate at T > 1450 K, whereas Na2O and SO3 boost
C2S
After heating, if SO3 occurs in combination with MgO and/or Na2O, it does not inihibit the C3S crystallisation
as expected. Rather, it promotes the stabilisation of M1-C3S, thus indirectly influencing the aluminate content,
too. MgO increseases the C3S amount and promotes the stabilisation of M3-C3S, when it is in combination with
Na2O. Na2O seems to be mainly hosted by calcium aluminate structure, but it does not induce the stabilisation of
the orhtorhombic polymorph, as supposed to occur. Such features play a key role in predicting the physicalmechanical
performance of a final cement (i.e. rate of hydration and hardening) when used as a bulding material.
