Research On Properties And Mechanism Of Hydrophobic Nano-silica Modified Asphalt

As a kind of nanotechnology in the field of traffic construction materials,nano-modified bitumen has received increasing attention in recent years and has been developed,researched and utilized.It has broad application prospects.Ordinary inorganic nanoparticles have higher surface energy and are easily agglomerated,and their dispersibility and compatibility in organic materials are affected.This article considers the hydrophobic nano-silica modified by chlorosilane,silicone organic compounds and silane coupling agents as modified materials,and the introduction of asphalt into new nano-asphalt materials.Comparing the performance and mechanism of the unmodified hydrophilic nano-silica modified asphalt and the matrix asphalt,it provides reference and direction of improvement for the use of nano-asphalt in the use of road building materials and the development of nano-modified asphalt.First,different types of nano-silica modified asphalts were prepared and subjected to regular performance tests and short-term aging tests.The experimental results show that the hydrophobicity of the surface modified with respect to the unmodified hydrophilic nanoparticles under the same conditions improves the penetration index of the asphalt,the measured softening point T_R&B,the equivalent softening point T₈₀₀,and the low temperature ductility,viscosity values as well as lowering the equivalent brittleness point T_1.2.2 and other indicators have more obvious effects;short-term aging test proves that the modified particle can improve the thermal oxidation resistance of asphalt.Second,the temperature-sweep test,the frequency sweep test,and the compatibility test from the rheology point of the hydrophobic nano-silica modified asphalt mortar are performed by a dynamic shear rheometer.The experimental results show that the three types of hydrophobic nano-silica can effectively improve the resistance of the asphalt against external forces under the changes of temperature and frequency,and the capability is greatly improved compared to the unmodified nano-particles;from the perspective of rheological properties,the compatibility of various types of nano-silica modified asphalts was studied.The distribution of chlorosilane-modified nano-silica particles was the most uniform,followed by silane coupling agents and silicone organic compounds,and several types of hydrophobic materials.The compatibility with asphalt is better than that without surface modification.Third,morphology observation and distribution of nanomaterials were performed through scanning electron microscopy（SEM）tests of nano-silica particles before and after modification and modified asphalt;infrared spectroscopy（IR）analysis of nano-white before and after modification The chemical interaction between carbon black and the asphalt component was added with finely ground limestone powder to analyze the interaction between the slag powder,the organic groups on the surface of the particles,and the asphalt between the modified asphalt binder;differential scanning calorimetry（DSC）experiments were conducted to analyze the effect of nano-silica on the change of aggregation inside the asphalt before and after surface modification.The experimental results show that the nano-silica particles after surface modification have stronger adhesion and are evenly distributed in the asphalt without agglomeration;the organic group of the modifier has been successfully grafted onto the surface of the nanoparticles.A certain chemical interaction occurred between the asphalts and a chemical bond was formed.The binding mechanism between the hydrophobic nano-silica modified asphalt and the fine limestone powder was different from that of common inorganic nanomaterials,and a small amount of chemical bonds could be formed with the stones.