Effect of cone lift rate on the flow time of self-compacting concrete

A wide range of normal-strength self-compacting concrete (SCC) mixes ranging in compressive strength from 30 to 80 MPa with a maximum aggregate size of 20 mm were prepared in the laboratory, and the time taken by the flow to reach the spread diameter of 500 mm (t₅₀₀) and to stop (t_stop) of each mix in the slump cone flow test were recorded. The entire test was then numerically simulated from the moment the cone was lifted until the flow stopped, using a three-dimensional meshless smoothed particle hydrodynamics computational approach, treating the SCC mix as a non-Newtonian Bingham fluid. The aim was to investigate the effect of the cone lift rate on the flow pattern and t₅₀₀. The results demonstrate that an increase in the cone lift rate from 0·1 to 0·5–0·7 m/s (i.e. cone raised to a height of 300 mm in 3 to 0·6–0·43 s depending on the cube compressive strength) leads to a significant reduction in t₅₀₀, but the rate of reduction slows considerably when the cone lift rate is increased beyond 0·5–0·7 m/s (i.e. cone raised to 300 mm in under 0·6–0·43 s). This bilinear reduction in t₅₀₀ with the increase in the cone lift rate was observed for all mixes having a cube compressive strength in the range 30–80 MPa.