The effects of mixing time on cement paste slurry transport and mechanical property

Abstract

The optimization of mixing time could benefit transport and mechanical performances of paste due to the enhancement of cement dispersion and paste fluidity induced by mixing process. However, research on the effects of mixing time during paste preparation has rarely focused on the reasons and mechanisms for the changes in characteristic properties. In this paper, a mining paste mixing system was simulated based on the similarity principle that recorded the slump and mechanism of paste among several mixing modes and on the clarify principles with which mixing process affected paste's properties. The results indicated that in consideration of equal linear velocity, the transport and mechanical properties of paste were definitely improved with time when mixing time was less than 3 min. Once mixing time exceeded 3 min, the properties of paste were improved at a slower rate until they became insensitive to mixing action at four minutes. Taking into account the paste properties, operation efficiency and energy consumption, the optimal mixing time was determined as approximately 3 min. The reform towards mixing system which met paste filling flow of 90 m 3 /h was implemented by extending mixing time to 3.33 min. Consequently, the slump was definitely enhanced by ≤ 10%. Besides, the uniaxial compression strength (UCS) of specimens curing for 28 d was enhanced from 0.69 to 1.37 MPa.