Optimizing milling parameters for refining portland cement

Ordinary Portland Cement (OPC) supplied by Grupo Cementos de Chihuahua, Mexico has a particle size distribution (PSD) such that 90% of total particles correspond to 50μm, disclosing an onset setting time of 2 to 3 hours. Depending on its chemical composition OPC might attain 40MPa of compressive strength after 28 days curing. Reducing the particle size of cement ingredients increases its reactivity as to turn out into super fast setting cement (FSC). Providing that an efficient compaction technique and an effective water reducing additive are used, the mechanical properties of concrete might substantially be increased. In this work OPC has been mechanically refined to 2 and 9μm (50 and 90% PSD, respectively) and thus mechanically activated through high energy milling, so that 2 to 3 min is the setting time observed. To further reduce the particle size several experimental milling conditions have been evaluated, such as ball to powder (B/P) ratio, milling time, rpm of milling device, etc. Results indicate that after reaching this size, FSC particles agglomerate rather than undergoing further refinement, in spite of adding chemical dispersion agents.