Effect of calcination process and calcium-silica ratio on the composition and properties of hydraulic lime

The calcination process and the ratio of to calcium to silicon in raw materials are the key factors affecting the mineral composition and properties of natural water hard lime(NHL). This study prepared NHL was by different calcination processes using argillaceous limestone tailings with different chemical compositions as raw materials. This paper studied the mineral composition and compressive strength of the prepared NHL by a combination of orthogonal and single-factor tests, and analyzed the effect of calcination process and calcium-silica ratio on its performance. Results showed that: ① With the increase of calcination temperature, the content of CaO in NHL decreased, and the content of dicalcium silicate(Ca₂SiO₄, C₂S)increased in NHL. ② Calcination temperature had the most significant effect on the mineral composition and compressive strength of NHL, followed by holding time and heating rate. ③ In the calcination temperature range of 1 000~1 100 ℃, the natural hydrostatic lime prepared by the given argillaceous limestone tailings meets the requirements of NHL2 and NHL3.5 strength grades. ④ When the calcium-silicon ratio is in the range of 3.55~6.76, the compressive strength of NHL decreases and then increases with the increase of calcium-silicon ratio, while the CaO content shows continuous increases.