Study on influencing factors of shear characteristics of rock-fill concrete layer of iron tailings as fine aggregate

Abstract

With global energy conservation and emission reduction, recent research have begun to explore the possibility of iron tailings application in concrete. The layer condition of rockfill concrete is directly related to the shear strength of the layers, and affects engineering stability. In this research, the shear performance of iron tailings as fine aggregate rockfill concrete with different layer characteristics was investigated. In this paper the particle size distribution, fineness modulus, stone powder content, density, chemical composition, mineral composition and other basic properties of iron tailing sand were measured. Experimental data were compared with mechanical sand and combined with microscopic morphology observation to verify the feasibility of iron tailing sand to replace mechanical sand in the preparation of rockfill concrete. 12 groups of rockfill concrete with iron tailings with different layer characteristics and 1 group of rockfill concrete with iron tailings without layer were designed. The influence of different rockfill exposure height and area, degree of roughen and content of stone powder, afterward, all the rockfill concrete samples were subjected to four grades of normal stress loading shear tests, control group without layer was comparedwithdifferent layers. The observed microstructure morphology and physicochemicalproperties show that iron tailings as fine aggregate can be used to replace mechanical sand in the preparation of rockfill concrete, however, the content of stone powder and mud in iron tailings should be controlled. It is concluded that the shear failure of layered rockfill concrete samples is in two forms, failure along one side of the specimen and failure along the shear layer. Rockfill exposure height and area, degree of roughen and content of stone powder, all have a certain degree of impact on shear characteristics, rockfill exposed stone area has the greatest effect, and the shear strength increases by 4.92%∼38.24%. The increase of shear strength at the interface of rockfill concrete with multi-aggregate layer is less than the aggregate shear strength under the influence of a “stone group effect”. The stone powder content of rockfill concrete increases, the layer shear strength also decreases. The overall results indicate that useful references for the design of sheering properties of layers of rockfill concrete and construction of rockfill concrete layer in the future.