Study On The Microstructure Of Ultrafine Cement Emulsified Asphalt Mastic And Its Adhesion Characteristics

With the development of China’s economy,the number of new roads built in China is increasing year by year.In order to combat climate change and promote sustainable development of human society,efforts must be made to reduce greenhouse gas emissions.China is committed to achieving carbon peaking by 2030 and carbon neutrality by 2060.Emulsified asphalt is widely used as a road material that can be constructed at room temperature and is more environmentally friendly.Existing studies have often added a certain amount of cement to emulsified asphalt to form a cement-emulsified asphalt composite.Although the addition of cement can reduce the time required to build up the strength of the mix,the rate of hydration of the cement greatly limits the growth of the viscosity of the emulsified asphalt,and because of the large size of the ordinary cement particles,when mixed with emulsified asphalt,the cement particles are encapsulated by the asphalt making the hydration of the cement incomplete and the rate of hydration slow.At room temperature,the viscosity of the cement-emulsified asphalt slurry is not sufficient to make the emulsified asphalt slurry on the aggregate coating rate is low and poor adhesion.The key to improving the road performance of cement-emulsified asphalt is to improve the adhesion of the early cement-emulsified asphalt slurry to the aggregate.Superfine cement is very different from ordinary cement in many aspects of physical and mechanical properties,rheological properties and hydration properties,with small particle size,large specific surface area,fast hydration rate and more uniform distribution.Based on this,this thesis intends to investigate the adhesion properties and microstructure of superfine cement emulsified asphalt slurry.The three emulsified asphalt slurries and the evaporated residues of the emulsified asphalt were tested at different maintenance ages using a dynamic shear rheometer and a bending beam rheometer.The results showed that the high temperature performance of the superfine cement emulsified asphalt slurry was better than that of the ordinary cement emulsified asphalt slurry at the same temperature and age;the effect of the superfine cement on the low temperature and fatigue cracking resistance of the emulsified asphalt slurry was not significant compared to that of the ordinary cement.Fourier infrared spectroscopy,scanning electron microscopy and atomic force microscopy were then used to study the emulsified bitumen residues and cement emulsion asphalt slurry in order to analyse the microstructure of the emulsified bitumen slurry.An X-ray diffractometer was used to qualitatively and quantitatively analyse the hydration products of the cement at different ages.The results show that the mixing process between cement and emulsified bitumen is a physical co-mingling;the ultrafine cement particles are more uniformly distributed in the emulsified bitumen than in ordinary cement;the two-dimensional height image of the evaporated residue of the emulsified bitumen does not show a ’bee-like’ structure;the rate of hydration of ultrafine cement is significantly faster than that of ordinary cement,which results in a higher This results in a higher early strength of the superfine cement and a faster rate of hydration,which leads to faster breaking of the emulsified bitumen.Finally,the 15℃ splitting strength test,freeze-thaw splitting test and rutting test were used to study the road performance of three kinds of emulsified asphalt mixes,to analyse the effect of ultrafine cement on the road performance of emulsified asphalt mixes,and to analyse the void characteristics of three kinds of emulsified asphalt mixes by CT scan test.The results show that the addition of ultrafine cement has significantly improved the strength and high temperature performance of the emulsified asphalt mixes;the addition of ordinary cement to the emulsified asphalt mixes increased the small and medium voids and reduced the large voids,and the effect was more obvious after the addition of ultrafine cement.The maximum pore size of the mix was also reduced after the addition of cement.