News

Effect of Silica Purity

Time:

2017-04-22

Source:

network

For a period of time, people have clearly realized that the contemporary low cement castables require accurate control of the settlement process, which is greatly affected by the chemical purity of the added silicon powder [6]. The purity of silica fume and its influence on low cement castable system play an important role in the development of durable castable. From the figure below, we can see the influence of low purity silica fume on the control of castable flow and settlement behavior. These silica fume are added to the mullite based castable formula together. One formula uses fast setting cement (CA-14W) and the other uses slow setting cement (CA-14S). The big difference between the three grades of silicon micro powder is their chemical purity. The total silicon oxide content changes from relatively low (94% SiO2) to relatively high (>98%). It is worth noting that dispersed alumina can overcome the adverse effects of low purity silicon powder on sedimentation and flow behavior through adjustment. It should also be noted that even if the reduction of the purity of silica fume has a great impact on the settlement and flow characteristics of the castable, this can be overcome by correctly selecting cement and using dispersed alumina.

The production process of 70% calcium aluminate cement was improved, and the development of cement clinker phase was closely controlled. So as to achieve accurate control of cement performance, which is very important for the use of these cements in contemporary high-performance refractory castables. In particular, the control of settlement and flow characteristics has promoted the development of high flow castables. Stable cement quality and dispersed alumina make the formula of castable very flexible, which can overcome the contradiction caused by other raw materials such as low purity silicon powder.

Key words: calcium aluminate powder