Research On Rheological Properties Of Concrete With Mill Tailings Of Iron Ore As Aggregate

It is the development trend of concrete to use artificial sand instead of natural sand. The workability of concrete prepared with artificial sand was generally unsatisfied. So attention has to be paid to certain rheological properties of freshly mixed concrete that also influence the microstructure of the hardened paste. The propose of this study was to conduct a systematic comparison of the difference between mill tailings of iron ore and natural sand in rheological properties .The particle shape difference between mill tailings of iron ore and natural sand were compared with a shape parameter—roundness. The outlines of particles were obtained by a scanner and then numerical treatment was used to analyze roundness parameters.For cement paste, plastic viscosity coefficient of paste depended on water/powder ratio and a negative exponential correlation existed, while yield stress was related to powder characteristics.For cement mortar, a negative correlation existed between fluidity and yield stress. The fluidity weren't correlated with plastic viscosity coefficient at different filling coefficient, water/powder ratio and content of powdery mill tailings of iron ore. The mortar plastic viscosity coefficient reached a maximum when the filling coefficient was about 1.18.The slump process was recorded by a camera to obtain the strain rate, acceleration and the angle between the direction of motion and horizontal. Then the new concrete rheological formulas could be educed. The research on concrete had shown that the filling coefficient had more effect on the yield stress than on the plastic viscosity coefficient. Superplasticizer, retarder and air entraining agent can effect rheological properties of concrete.Plastic viscosity coefficients of natural sand were larger than that of mill tailings of iron ore, and yield stresses of the former were less than the latter.