Effects of Mg on the Mineralogy and Micro-Mechanical Properties of a Cao-Sio2-H2o System Under Autoclaved Conditions

Abstract

In the mining of natural limestone, the phenomenon of calcium-magnesium accompaniment is very common. According to our previous study, Mg 2+ can enter the crystal lattice of calcium silicate hydrates. In this study, the mineralogy of a CaO-MgO-SiO 2 -H 2 O system was characterized and the micro-mechanical properties were evaluated using nano-indentations to clarify the effect of magnesium on the mechanical properties of quartz sand-lime autoclaved products. The results showed that magnesium facilitated the formation of C-S-H with lower alkalinity and accelerated the transformation of C-S-H (I) into tobermorite, thereby improving its crystallinity. Petal-like Mg-tobermorite was generated from the original flaky tobermorite, and the amount of binding Mg-tobermorite reached 2.5% under an autoclaved temperature of 180°C. Furthermore, the content of ultra-high-density C-S-H increased when 5% magnesium was added to the system.

Keywords: CaO-MgO-SiO-H2O autoclaved products, Mineralogy, Micro-mechanical properties, Tobermorite