AbstractPumping of concrete is an efficient placement technique. When the concrete is pumped in a pipe, the lubrication layer (LL) forms and its rheological properties predominantly dictate the flow and govern the resumption operations. The primary purpose of this study was to investigate the effects of a new admixture, limestone calcined clay (LC2) at variable replacements (0%, 5%, 10%, and 20% by weight) on rheological properties of cementitious suspensions (equivalent to lubricating layer). An increase in yield stress, plastic viscosity, structuration rate, and decreased percolation time were observed with increments in the proportion of LC2 in cementitious suspensions. However, at the optimal dosage of superplasticizer, yield stress and plastic viscosity were decreased by 78% and 82%, respectively, even for the maximum replacement (20%) of LC2. Similarly, the percolation time increased by 15% and the structuration rate decreased by 39%, allowing additional time to deal with any pumping operational delays. From the results, it is also evident that higher deformation ratio of the lubrication layer is beneficial for concretes at rest due to pumping interruption. This study contributes to the fundamental understanding of viscoelastic properties of LC2-based cementitious suspensions, which will improve understanding of lubrication layer behavior for pumping operations.

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