Concrete relative velocity prediction to prevent mortar segregation for safe gravity transportation

Concrete mortar segregation during vertical pipeline gravity transportation will form a weak part in the shaft lining, which poses a challenge for deep mine shaft safety. The specific gravity difference between aggregate and slurry will cause relative motion; the relative velocity is detrimental to the mortar workability, which plays a significant role in mortar segregation. A prediction model of the relative velocity between slurry and aggregate was proposed and verified by numerical simulation results. This approach adopts the interference coefficient to revise the aggregate collision loss. The corresponding relationship among aggregate relative velocity, mortar rheological properties and particle shape was analysed to explain the mortar segregation mechanism. Segregation can be prevented by increasing the mortar viscosity and shape coefficient and decreasing the density difference and aggregate diameter to reduce the relative velocity. This work is favourable for concrete mortar quality control for gravity transportation and shaft lining construction safety. (C) 2020 The Authors. Published by Elsevier B.V. on behalf of Faculty of Engineering, Alexandria University.