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

Abstract

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 (tstop) 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.