Research Of Surface Modification And Road Performance Of Machine-made Sand Concrete Pavement

Compared with natural river sand,machine-made sand has a high content of powder and a large proportion of needle-like particles,which leads to a decrease in the durability and anti-skid performance of machine-made sand cement concrete pavement.nano-SiO₂has the characteristics of small particle size,large specific surface area,high activity,etc.,which has an outstanding effect on improving the performance of cement-based materials;combined with hydrophobic agent composite modified cement-based materials can increase surface hydrophobicity and improve the compactness of the structure from the micro level.Compared with natural river sand,machine-made sand has a high content of ore powder and a large proportion of needle-like particles,which leads to a decrease in the durability and anti-skid performance of machine-made sand cement concrete pavement.nano-SiO₂ has the characteristics of small particle size,large specific surface area,high activity,etc.,which has an outstanding effect on improving the performance of cement-based materials;combined with hydrophobic agent composite modified cement-based materials can increase surface hydrophobicity and improve the compactness of the structure from the micro level.In this paper,systematic experimental research is carried out on the composite modification of machine-made sand,cement mortar and concrete with nano-Si O2 colloid and hydrophobic agent.On the basis of exploring the anti-skid performance and durability of machine-made sand pavement,combined with the microstructure of hydration,a correct understanding of the role of composite nanomaterials in concrete pavement can reduce the lack of concrete durability and anti-skid performance caused by the use of machine-made sand,Not only will greatly reduce the application of river sand,at the same time it is of great significance to ecological protection.The innovative results and main conclusions of this paper are as follows:（1）The fluidity of composite modified machine-made sand,cement mortar and concrete gradually decreases with the increase of hydrophobic agent and nano-SiO₂colloid.Under the same dosage of nano-SiO₂ colloid,the addition of three hydrophobizing agents reduces the fluidity of machine-made sand cement mortar.The lotus leaf type hydrophobic agent has a greater influence on the fluidity of cement-based materials.The silicone hydrophobing agent has less effect.（2）Nano-SiO₂ colloid and hydrophobic agent improve the mechanical properties and wear resistance of machine-made sand cement mortar.The full experimental method tested the 28d flexural compressive strength of 96 groups of modified machine-made sand cement mortars.The maximum flexural strength was 9.2MPa and the maximum compressive strength was 52.4MPa.According to the multi-factor variance method,analyze the influence of nano-SiO₂ colloid type,hydrophobic agent type and dosage on the work performance and compressive and flexural properties of cement mortar,and further apply the comprehensive performance value method to comprehensively and objectively evaluate and find composite modified materials The best ratio.（3）The surface spraying method and the external admixture method were compounded to modify the machine-made sand concrete,and it was found that the impermeability of the surface spraying compound modified machine-made sand concrete was better than that of the external admixture method.When nano-SiO₂ colloid and lotus leaf water-repellent agent P800 are respectively 7%and 4%of the cement quality,the average penetration depth and related impermeability coefficient of modified machine-made sand concrete are the lowest,the impermeability is improved the most,and the average penetration height is reduced to the benchmark The average penetration height of machine-made sand concrete is 11.7%.（4）The self-made three-wheel accelerated loading abrasion test system is used to simulate the abrasion of automobile tires on the machine-made sand concrete pavement,and the dynamic friction coefficient instrument is used to macroscopically evaluate the anti-skid performance of the modified concrete pavement.The test found that when the nano-SiO₂ colloid 1050 and lotus leaf water-repellent agent P800 were 7%and 4%of the cement mass,respectively,the zero-order dynamic friction coefficient value of the modified concrete was the highest,about 0.6,and the dynamic friction coefficient change curve was relatively Smooth,after 160000 times of accelerated loading and polishing times,the dynamic friction coefficient is still 0.348.（5）With the hardening of machine-made sand,cement mortar and concrete,the filling and densification effect of composite nanomaterials is gradually exerted,which reduces the porosity of concrete and improves the pore characteristics.XRD diffraction analysis and SEM scanning electron microscopy showed that with the increase of the content of nano-SiO₂ colloid,the nano-SiO₂ colloid consumes the CH component,and the diffraction peak of Ca（OH）₂ decreases,which reduces the content of Ca（OH）₂ in the transition zone of the concrete interface.,And the hydrophobic agent together improve the microstructure of the interface transition zone and reduce the number of micro-domain cracks in this zone.（6）The composite modified machine-made sand cement concrete pavement has a certain surface hydrophobicity after forming and curing.After 160,000 times of accelerated loading and abrasion,the hydrophobic performance of the surface spraying method on the concrete surface is significantly attenuated.The surface hydrophobicity of the specimens has been reduced to a certain extent,but most of the modified machine-made sand concrete still has hydrophobic properties.Therefore,the research in this article provides new ideas for improving the road performance of machine-made sand cement concrete pavement and prolonging the service life of machine-made sand cement concrete roads,and provides technical reference for the performance research of limestone machine-made sand cement concrete pavement.