Study On The Microstructure And Durability Of Cement Emulsified Asphalt Mortar

The national "One Belt,One Road" marine plan has resulted in a rapid expansion in the number of offshore and coastal structures,but the hostile marine environment has severely decreased the service life of reinforced concrete structures.This paper investigates the effect of cationic emulsified asphalt on the microstructure,mechanical properties,and durability of cement slurry,as well as the intrinsic relationship between microstructure and macroscopic properties.It also investigates the feasibility and applicability of emulsified asphalt mortar as a protective mortar for concrete structures in the marine environment,which is critical to the service life of concrete structures in harsh environments.The main findings of this paper are as follows:(1)Study on the microstructure of cement and asphalt slurry.Metallographic microscopy was used to examine the cement-asphalt bonding process,and it was discovered that the cement hydration process stimulated the breaking of the cationic emulsified asphalt,while the asphalt film generated after the breaking inhibited the cement hydration process.The microscopic morphology and elemental composition of the CA slurry were characterised by scanning electron microscopy,and it was found that the slurry microstructure was based on the cement matrix as a continuous phase,and the asphalt film formed after emulsion breaking and aggregation interspersed with the cement hydration products,forming a mesh-like structure of the cement-asphalt interface transition zone,in which a large number of pores were distributed,and the generation of hydration products was inhibited,and the denseness of the matrix decreased with the increase of A/C.The pore structure of the CA slurry was characterised with the help of mercury-pressure tests,and it was found that the porosity of the CA slurry and the percentage of harmful pores larger than 20 nm increased with the increase of the cationic emulsified asphalt admixture,and the asphalt film formed after the emulsified asphalt broke the emulsion and gathered would cover the pore wall,and the large pore size and number of pores became the significant characteristics of the transition zone of the cement-asphalt interface.(2)Study the mechanical properties of CA mortar.The mechanical properties of the CA mortar were characterised by the bending ratio test,the fracture energy test and the impact test.It was found that the toughness of the CA mortar increased and then decreased with the increase of cationic emulsified bitumen,and the best toughness was achieved at A/C=0.15.The bending ratio test was not applicable to the toughness characterisation of the CA mortar at high emulsified bitumen dosing.The mortar bond strength test revealed that the bond strength of the CA mortar to the cement matrix at 14 days was greater than 1MPa,meeting the requirements of the repair mortar specification.(3)Study the durability performance of CA mortar.The contact angle test revealed that the contact angle between the CA slurry and deionised water became larger with increasing A/C,indicating that the cationic emulsified bitumen improved the hydrophobic properties of the mortar and inhibited the transfer of water to the cement substrate.The electric flux test and the sulphate immersion test showed that the incorporation of cationic emulsified bitumen inhibited the transport of aggressive ions into the mortar and improved its resistance to ionic attack.Sulphuric acid immersion tests showed that the incorporation of cationic emulsified bitumen delayed the "neutralisation" reaction and improved the acid resistance of the mortar,effectively ensuring the structural stability of the mortar in the acid solution.The freeze-thaw cycle test was used to characterise the frost resistance of CA mortar.It was found that the frost resistance of CA mortar decreases with increasing A/C due to the decrease in viscosity and increase in brittleness of the bitumen film at low temperatures,resulting in a decrease in the bonding of the bitumen film with the hydration products,indicating that CA mortar is not suitable for use in cold regions.