Study On Anti-scouring Characteristics Of Concrete Improved By Deep Penetrating Sealer(DPS)

Among the various factors that cause the damage of concrete surface,erosion failure is a common failure mode,which is usually used to describe the wear effect of fluid containing solid suspended particles on concrete,which is generally found in concrete runner structure,such as spillways,diversion tunnels,channels,etc.Therefore,it is very important to study the corresponding protective measures and repair means for the long-term safe operation of concrete.As an effective means to deal with external corrosive substances and make up for the defects of concrete itself,coating protection technology can directly act on the surface of concrete to avoid the change and damage to the structure of concrete itself.At present,water-based permeable crystalline inorganic waterproofing agent-permanent condensate(DPS)is widely used in anti-seepage and durability protection engineering of concrete structures due to its many advantages.This paper focuses on the reaction mechanism of DPS and concrete materials and the evolution characteristics of physical properties of concrete surface.The micromorphology,chemical composition and pore structure of the reaction products of DPS and concrete were observed and analyzed by experiments,and the mechanism of enhancing the physical properties of concrete surface was revealed.Water absorption,impermeability,surface hardness and contact angle tests were carried out to test and analyze the effect of DPS on concrete.The continuous impact test of concrete was carried out by using the self-designed high-speed water erosion equipment.At the same time,the flow velocity,sand content,erosion angle and DPS spraying times were used as variables,and the three-dimensional scanning equipment was used to visualize the erosion pit.The characteristic parameters of the erosion pit were analyzed to evaluate the erosion effect.This study will deepen the understanding of the mechanism of DPS and provide theoretical support for the durability design of concrete surface based on DPS.The main research results are as follows:(1)The reaction process between DPS and concrete material is mainly reflected in the chemical reaction between sodium silicate in DPS and calcium hydroxide in concrete,which causes the decrease of calcium hydroxide content and the increase of calcium silicate content in concrete.The resulting calcium silicate particles have a particle size of 50nm.DPS has a certain sealing effect on the pores in the pore size range of 20～130nm in concrete,but has a weak effect on the pores in other sections.As the alkali content(calcium hydroxide)near the cracks and pores of concrete is high,a large amount of calcium silicate can be generated after spraying DPS.Therefore,DPS plays a significant role in filling concrete holes.After DPS treatment,the specific surface area,porosity,average pore size,threshold pore size and critical pore size of the internal pores of the concrete decreased by 3.58m~2/g,5%,9nm,38nm and 54nm,respectively,and the surface compactness is significantly improved.(2)After DPS treatment,the water absorption rate of the concrete surface is significantly reduced,and its impermeability and microhardness are improved in different degrees.Among them,the improvement degree of surface physical properties of the concrete with more water-cement is significantly higher than that of the concrete with less water-cement.After DPS treatment,the surface smoothness and smoothness of concrete are improved to a certain extent,and the roughness is reduced,the surface contact angle decreases.(3)In the scour test,the scour velocity has a significant effect on the volume and average depth of the concrete surface,and the scour Angle has a significant effect on the area and average depth of the concrete surface.The overall effect of DPS increased with the increase of spraying times,but with the increase of flow rate and sand content,the effect of DPS under the condition of high flow rate and high sand content is lower than that under the condition of low flow rate and low sand content.When the depth of the pit exceeds the infiltration depth of DPS,the damage caused by erosion will be greatly intensified.