Effects Of Ultra-fine Mineral Admixture On The Properties Of High-strength Concrete Mixture

In order to reduce the plastic viscosity of high-strength concrete mixture and improve the workability of high-strength concrete.In this paper,two kinds of ultra-fine fly ash with average particle diameter of 8.289μm(UFA1)and 3.677μm(UFA2)are collected by sorting process,one kind of ultra-fine fly ash with average particle diameter of 5.528μm(UFA3)and two kinds of ultra-fine slag with average particle diameter of 8.559μm(US1)and 11.309μm(US2)are produced by mechanical milling.They are selected respectively to study the influence with single-mixed and compound-mixed on the workability and mechanical properties of high-strength concrete.Effects of ultra-fine mineral admixture on the workability of high-strength concrete is analyzed based on film thickness theory.The results showed that:UFA1,UFA2,US1,US2 single-mixed can effectively increase the fluidity and decrease the marsh time of cement paste.The marsh time of UFA3 single-mixed can remain basically unchanged compared with benchmark group under different dosage,but UFA3 can effectively increase the fluidity within a certain dosage range.Under the same dosage,the fluidity and marsh time of cement paste with UFA1,UFA2,UFA3single-mixed sequence respectively that UFA2>UFA1>UFA3;UFA3>UFA1>UFA2.The influence rules on the fluidity and marsh time of cement paste with US1,US2single-mixed is similar.UFA1,UFA2,US1 single-mixed and compound-mixed can effectively increase the slump and slump-flow,decrease the plastic viscosity,reduce the slump and slump-flow1 h loses through time of high-strength concrete.In addition to the partial dosage of UFA2single-mixed,UFA1,UFA2,US1 single-mixed and compound-mixed can effectively increase the apparent density of concrete mixture.UFA1,UFA2,US1 compound-mixed can increase the apparent density of concrete mixture compare with single-mixed,and the plastic viscosity of concrete mixture with UFA1,UFA2,US1 compound-mixed is significantly lower than single-mixed.UFA2,US1 single-mixed and UFA1,UFA2,US1 compound-mixed can effectively increase the compressive strength and split-tensile strength at 7d and 28 d of high-strength concrete within a certain dosage range.With the dosage increase of UFA1single-mixed,the compressive strength at 7d and 28 d of concrete decreases gradually,but UFA1 single-mixed can effectively increase the split-tensile strength at 7d and 28 d of concrete within a certain dosage range.UFA1,UFA2,US1 compound-mixed can’t significantly improve the compressive strength and split-tensile strength at 7d of concrete compared with single-mixed,but the compound-mixed can significantly increase the compressive strength and split-tensile strength at 28 d of concrete.UFA1,UFA2 single-mixed can effectively increase the packing density of cementitious materials and the water film thickness on the solid particles surface in the cement paste,under the same dosage,the packing density of cementitious materials with UFA2 single-mixed are higher than UFA1 single-mixed.Water film thickness is strongly correlated with the workability of cement paste,taking the maximum water film thickness as the design goal on the workability of high-strength concrete with ultra-fine mineral admixture,it can make concrete show excellent workability finally.