The Effect of Mechanical Activation of Lime Putty on Properties of the Autoclaved Calcium Hydrosilicate Materials

The lime putty is a non-Newtonian fluid that can be either thixotropic or rheopectic depending on burning process of the lime, the presence of the quartz sand and other parameters. One of the most important lime putty characteristics is its plasticity which affects its workability and use. It is possible to increase the lime putty plasticity by mechanical activation. This work focuses on the effect of the mechanical activation of the lime putty on its rheological behavior and on properties of lime hydrosilicate autoclaved materials. Fresh lime putty was activated in a high-speed mixer at 1000 RPM for 1, 3, 5 and 10 minutes. Non-activated lime putties show rheopectic behavior. Rheopectic behavior becomes slightly more distinct after 1 min. of activation and then less distinct with increasing time of activation. After 10 min. of activation, the system shows no time-dependent properties, nor even slight thixotropic behavior. This trend can be related to process where smaller and smaller aggregates are fragmented in the suspension. The hydrosilicate materials were prepared in two series from quicklime and finely ground sand with the ratio C/S 0.85, under hydrothermal conditions. The amount of xonotlite in hydrosilicate material increases with activation time as the increased amount of portlandite particles retards the reaction. 11.3 Å tobermorite crystallizes more slowly and formation of xonotlite is accelerated.