Alternative Evaluation of the grindability of Pozzolanic Materials for Cement Production

An ecological way of reducing CO₂ emissions in cement production is the usage of blended cement with an active pozzolan. A part of this issue is the adjustment of granularity of raw materials. This is often achieved by the grinding of the input components. All conventional methods for the evaluation of grindability require a specific grinding instrument. These grinding instruments do not have any other practical use and thus are not very common. This paper focuses on the alternative evaluation of grindability. Inspired by the VTI method used in the coal industry, which uses porcelain laboratory ball mill and compares material based of oversize particles, a new method was created. The first modification in methodology was the use of a planetary mill instead of a porcelain drum mill. Another modification was in the measurement of undersize by means of laser granulometry. This method was then tested on clinker, slag, and recycled glass, which can also be used as an active pozzolan in blended cement. Also, co-milling measurements were made on clinker-pozzolan combinations. These results were then used in the calculation of the grindability index, which can be used for the comparison of properties. The modification of the VTI methodology has a positive impact on the evaluation of grindability, especially with regard to fine particles, thanks to the use of laser granulometry and at the same time it makes use of more a commonly available grinding apparatus