The Gradient Design And Durability Research Of Materials Of Concrete Slab For Earth-rock Dam In Cold Regions

The complex hydraulic environmental conditions in cold regions have brought great challenges in the service life of earth-rock dams.The concrete dissoluble erosion caused by contacting with water for a long time in concrete slab will lead to the deterioration of the pore structure having influence on the properties of slab materials.In recent years,the ideas of materials gradient design is attracting more and more attention of concrete constructions.This material can both enhance the properties of concrete and save cost.In this paper,the concrete slab is designed as gradient material.The UHPC in protective layer and the ordinary concrete in structural layer are combined together as a whole structure with the ideal of material gradient design.Both the protective layer and the whole gradient structure are researched in this paper.The protective layer need to have the characteristic of high strength,high resistance of dissoluble erosion and low shrinkage.In this paper,silica fume were added to UHPC to study the influence of strength and resistance of dissoluble erosion at variable levels of 10%,20%,30% and by mass of cementitious materials,respectively.The results show that the compression strength increased at first and then decreased with the addition of silica fume.The peak value is during 10%～20%.And silica fume could improve flexural strength of UHPC between 30% to 50%.Also,silica fume could improve the resistance of dissoluble erosion a lot.When the content of silica fume was over 20%,there was almost no phenomenon of dissoluble erosion.In addition,this paper also focused on the shrinkage of UHPC.Steel fiber,shrinkage reduced agent and expansive agent were added to UHPC to study the influence on reducing shrinkage of protective layer.The result showed that expansion agent had the most significance effect,then is shrinkage reduced agent and steel fiber.In this paper,ABAQUS was used to do numerical simulation to study the properties of the interface of gradient concrete.The shrinkage stress of interface was calculated by simulation software through the shrinkage data of experiments.The bond strength of interface was calculated by simulation of splitting test and bi-surface shearing test.The result showed that the property of structural material had significance effect on bond strength of interface.The structure had higher bond strength when the strength of structural layer was higher.Furthermore,sequential thermal coupling was used to study the damage of freeze-thaw cycles around interface.The result showed that the deterioration of the interface became slow when the strength of structural material was higher.