Erosion And Wear Protection Material For Concrete Structure In Strong Wind-sand Environment

The northwestern part of China suffers from eroding with wind and sand all the year round.The concrete structure in this area can be damaged as erosion cracks and cement peeling under the action of wind and sand erosion.And then other diseases and damages in concrete structure can be resulted.These damages can aggravate the failure of concrete structure and even cause great potential safety hazard.Consequently,the durability of concrete structurestructure will be reduced seriously.The destruction can be reduced by coating protection materials on the concrete structure surfaces.As a result,the concrete structure can be protected effectively.Therefore,it has quite important theoretical and practical significance of studying structurethe erosion and wear damage of protection materials for concrete structure in strong wind and sand.Epoxy resin is the most widely used polymer building material.It is often used for repairing concrete cracks and structural reinforcement.It is also the preferred material for erosion protection for concrete structure.However,due to the high brittleness and easy cracking of epoxy resin,it is needed to toughen and modify so as to be used as an erosion wear protection material for concrete structure.In this thesis,the epoxy resin was modified by the addition of SiC micropowder or both SiC micropowder and polyurethane toughener.The mechanical properties and erosion wear properties of the modified epoxy resin were evaluated.The effect of SiC powder size,contents of SiC powder and polyurethane toughener on properties of the modified epoxy resin was analyzed.The modified epoxy resin with excellent erosion wear resistance was obtained.Based on this matrix,carbon fiber and glass fiber reinforced epoxy resin composites were prepared.Their mechanical properties and erosion wear properties were investigated,and their erosion wear mechanism was analyzed.The feasibility of using carbon fiber and glass fiber epoxy resin composites in erosion wear protection of concrete structure was discussed.The research contents and conclusions are as follows:(1)The epoxy resin was modified by SiC micropowder with the same particle size.With the increase of SiC content,the tensile strength and impact toughness of SiC powder modified epoxy resin first increased and then decreased.When the content of SiC micropowder was 5%,the tensile strength and impact toughness of modified epoxy resin were the largest.When the epoxy resin was modified with SiC micropowders of different particle sizes,it was found that the tensile strength and impact toughness of the SiC micropowder modified epoxy resin increased with the decrease of the SiC particle size;When the size of SiC powder is 1000mesh and the dosage is 5%,the optimum mixing ratio is obtained.The tensile strength,Shore hardness and impact toughness of SiC powder/epoxy resin material prepared by this mix ratio are 55.43 MPa,79 HA and 1.02 J/cm~2.(2)The volumetric erosion rates of SiC powder/epoxy resin materials with different proportions at different erosion angles and velocities were investigated.The experimental results show that the erosion resistance of SiC micropowder/epoxy resin material is the best when the SiC micropowder size is 1000mesh and the content is 5%.The SiC micropowder/epoxy resin has the highest erosion rate when the erosion angle is 60°,showing the erosion characteristics of semi-plastic materials in gas-solid two-phase environment.(3)When SiC micropowder and polyurethane toughener P24F were used to modify epoxy resin,the erosion resistance of modified epoxy resin was the best when the content of SiC powder was 5%and P24F was 12.5%.The erosion rate is 0.066 mm~3.g~-11 under the condition of 27 m/s erosion speed and 45°erosion angle,which is 17.5%lower than that of SiC micropowder/epoxy resin without toughening agent.(4)In order to solve the problems of difficult construction and high cost of coating epoxy resin,modified epoxy resin composites reinforced by glass fiber cloth and carbon fiber cloth were prepared.The volumetric erosion rates of the two composites were 0.529 mm~3·g~-11 and0.379 mm~3·g~-11 respectively when the erosion velocity was 27 m/s and the erosion angle was45°.The maximum erosion rate occurs at 60 erosion angle.The tensile strength of composites increases with the addition of glass fiber cloth and carbon fiber cloth,and the erosion wear resistance decreases,showing the erosion characteristics of semi-plastic materials.(5)The erosion and wear mechanisms of various reinforcements in epoxy resin matrix composites are as follows:erosion and wear of sand flow on the surface of materials can be decomposed into normal extrusion deformation and tangential micro-cutting failure;SiC particles filled in epoxy resin matrix have great hardness and stiffness,and can resist the impact and cutting damage of sand particles on the matrix material.Flexible segments in polyurethane toughener P24F can absorb external impact energy and effectively prevent the formation of microcracks due to erosion of the matrix.Glass fiber cloth and carbon fiber cloth belong to brittle materials,which are easy to break and peel off when erosion occurs,so the erosion resistance of composites is reduced.(6)The volume erosion rate of epoxy resin matrix composites reinforced by fibre cloth is1/4-1/13 of that of common building materials such as cement paste,concrete and mortar,which is suitable for erosion and wear protection of concrete structure in strong wind and sand flow environment.Glass fiber reinforced epoxy resin matrix composites are the best choice of erosion and wear protection materials for concrete structure in strong wind and sand flow environment.