The objective of this study was the synthesis of
L-C2S (Ca2SiO4) belite cement, starting from fly-ash of
system CaO–SiO2–Al2O3–SO3, and using the hydrothermal method in alkaline solution. The lime deficit in
these asheswascompensated by the addition of slaked lime from lime bagging workshops. The hydrothermal
treatment of the mixture was carried out in demineralized water, NaOH or KOH solution, continually
stirred at a temperature below 100 ◦C and atmospheric pressure. The dehydration and calcination of the
mixtures at temperatures between 800 and 1100 ◦C allowed
L-C2S-rich cement to be obtained. The
optimization of the synthesis parameters (temperature and time of stirring, pH of solution, temperature
and duration of mixture burning) was also studied. The phase formation during various synthesis stages
was studied by X-ray diffraction (XRD). Other techniques, such as SEM and EDX, were used to characterize
the cement minerals. The results obtained showed that these ashes could form belite cement composed
of only one dicalcium silicate phase (
L-C2S).