Effect of Sandstone Fineness on Mineral Formation and Hydration Properties of Portland Clinker

Abstract

The fineness of the raw material is the essential factor affecting the burnability of raw meal, with the fineness of the siliceous material being of the utmost importance. In this paper, Portland clinker was prepared from sandstones with four different particle sizes. The effects of sandstone fineness on calcination, crystal structure, phase assemblage, and hydration of the clinker were investigated by means of thermomechanical analysis (TMA), X-ray diffraction analysis (XRD), isothermal conduction calorimetry (ICC), and thermogravimetric analysis (TGA). The results show that as sandstone fineness decreases, the clinkers undergo a gradual decrease in shrinkage during calcination, alongside a consistent rise in free lime (f-CaO) content. The decrease in sandstone fineness has been shown to have a significant effect on the size of C3S and C2S, but no obvious effect on their crystal structure. The f-CaO rapidly reacts with water to form Ca(OH)2 in the initial stage of cement hydration, resulting in the shortening of the hydration induction period and the advance of the hydration of C3S. Furthermore, the compressive strength of Portland cement increases with the increase in sandstone fineness at every age, and the increase in age compensates for the differences in strength among samples.

Keywords

• sandstone fineness
• clinker calcination
• free lime (f-CaO)
• cement hydration