Thermochemical behavior of several common salts blended with cement raw material

Abstract

Experiments have been conducted to study the thermochemical behavior of common chlorides, sulfates, and alkali salts (CaCl2, CaSO4, K2CO3, Na2CO3, KCl, NaCl, K2SO4, Na2SO4) when blended with cement raw materials at high temperatures, as well as the phenomena of element migration and transformation of Cl, S, K, and Na in the process. The results indicate that little effect was observed on the formation of clinker with the addition of 20% KCl&NaCl and 10% CaSO4. KCl&NaCl were observed to melt at 800°C but completely volatilize at 1100°C, while CaSO4 was not completely decomposed until 1450°C. The addition of 10% CaCl2, 20% K2CO3&Na2CO3, and 20% K2SO4&Na2SO4 resulted in the appearance of the liquid phase of raw materials at 800°C. K2CO3&Na2CO3 predominantly formed complex and stable potassium salts and sodium salts through reactions with raw materials, significantly affecting the formation of C2S and C3S. CaCl2 and K2SO4&Na2SO4 mainly produced liquid phases through melting. CaCl2 completely volatilized after reaching 1250°C, and the molten CaCl2 inhibited the decomposition of CaCO3, thereby inhibiting the formation of C2S and C3S. Although K2SO4&Na2SO4 melted, they only formed stable sulfate salts, without affecting the formation of C2S and C3S.