Preparation Of Environmentally Friendly Super-hydrophobic Concrete And Its Application In Long-distance Water Transport Channels In Cold Regions

The water resources are mostly in the south and the area is not balanced.In order to coordinate the regional water supply contradiction,a large number of long-distance inter-basin water transfer projects such as the South-to-North Water Diversion Project came into being.The concrete lining channel has become one of the backbone water delivery facilities due to its low cost,easy construction and easy management.However,long-distance concrete lining channels located in the cold and cold regions of northern China have insufficient head loss,poor anti-seepage ability and adaptability to deformation,resulting in insufficient over-current capability,serious frost heaving,freeze-thaw damage,and restricting the "lifeline".The safe operation of the project and the effectiveness of the project.Therefore,the use of rubber recycled concrete has low elastic modulus,strong adaptability to deformation,super-hydrophobic coating with good anti-seepage effect,remarkable drag reduction effect,etc.,and develops a simple process,durable and low cost,and integrates anti-seepage.The environmentally-friendly super-hydrophobic lining concrete with reduced drag and frost resistance is of practical significance for the construction of long-distance water transport channels in cold regions.To this end,based on the superhydrophobic "binary(rough microstructure + low surface energy)synergy" preparation ideas,the optimal preparation process of environmentally friendly superhydrophobic concrete was explored;and through series of physical properties test and numerical simulation,systematic research was carried out.Its mechanical properties,frost heave resistance,impermeability,drag reduction,ice-repellent and super-hydrophobic surface stability demonstrate its application value in long-distance water transport channels in cold regions.The main work and conclusions of the thesis are as follows:(1)Comparative study on preparation methods of environmentally friendly super-hydrophobic concrete: Firstly,environmentally-friendly concrete(30% of recycled concrete and 5% of waste rubber)is prepared;environmentally-friendly concrete is used as the base,and the surface is covered with copper mesh or used.The mortar surface is induced to form a rough surface microstructure and impregnated with fluorosilane to form environmentally-friendly super-hydrophobic concrete I and II,respectively.The preparation process and durability are preferred indicators,and the preparation method is preferred.The results show that the optimal preparation method of environmentally-friendly super-hydrophobic concrete is to use environmentally-friendly concrete surface with fine mortar,and the surface is immersed in a concentration of 1.5% fluorosilane.The surface contact angle is 153.4°,and the surface energy is only 2.58 mJ/m2,which achieves a better superhydrophobic state.(2)The mechanical properties of ordinary concrete and environment-friendly superhydrophobic concrete were studied.The compressive strength,splitting tensile strength and elastic modulus of environmentally friendly super-hydrophobic concrete decreased by 18.75%,3.3% and 39.9%,respectively,compared with ordinary concrete,indicating that the environmentally-friendly superhydrophobic concrete has little reduction in compressive strength and tensile strength.In the case,the modulus of elasticity can be greatly reduced,and the deformation can be better.(3)Based on the three-field coupling theory of frozen soil water heat,the frost expansion model of lining channel is established,and the stress distribution law of common concrete lining channel and environment-friendly super-hydrophobic concrete lining channel is analyzed.Compared with ordinary concrete,the maximum tensile stress and maximum compressive stress of the channel lining structure prepared by environment-friendly super-hydrophobic concrete are reduced by 51.8% and 14.4%,respectively,and the mean square stress of upper and lower surfaces is reduced by 32.8% and 50.7%,respectively,indicating that it adapts to deformation.Stronger ability and better resistance to frost heaving.(4)The impermeability of ordinary concrete and environmentally-friendly super-hydrophobic concrete was investigated by the "gradual pressurization method" impermeability test.Compared with ordinary concrete,the environmentally-friendly super-hydrophobic concrete has more than twice the impermeability grade,and the seepage height is only 13.9% of ordinary concrete;and compared with the anti-seepage composite lining,the cost of environmentally-friendly super-hydrophobic concrete lining is reduced per square meter.9.9% is an ideal anti-seepage and anti-freeze-thaw material.(5)A rectangular concrete lining channel with a length of 25 m and a longitudinal slope ratio of 1/400 was established.Through the hydraulic model test,ordinary concrete and environment-friendly super-hydrophobic concrete with flow rates of 0.02,0.039,0.047 and 0.057m3/s were determined.Surface roughness.The results show that the surface roughness of ordinary concrete and environment-friendly super-hydrophobic concrete are 0.01491 and 0.01322,respectively,and the surface roughness of environmentally-friendly super-hydrophobic concrete is reduced by 11.3%,which has a significant effect of reducing drag and can improve the efficiency of channel water delivery.(6)The concrete ice-breaking research was carried out with a self-designed concrete icebreaker,and the surface ice residual rate was evaluated.The residual rate of ordinary concrete ice is 74.4%,and the residual rate of environmentally friendly super-hydrophobic concrete ice is 30.9%,which is reduced by 51.8%,indicating that the environmentally-friendly super-hydrophobic concrete has good ice-slipping properties.(7)Through the "underwater steel ball method" grinding test,the abrasion time is taken as the independent variable and the surface contact angle is used as the evaluation index to explore the superhydrophobic surface stability of the prepared concrete.After 72 h abrasion,the surface contact angle is still stable above 100°,indicating that the hydrophobic surface has good stability.