Mix Design and Performance Study on CEA Slurry for Shield Tunnel Backfill Grouting in Typical Strata
To investigate the influence rule and mechanism of cement and emulsified asphalt contents on fluidity,consistency,compressive strength,setting time,and demulsification time of cationic cement emulsified asphalt(CEA)slurry,a series of proportioning tests,scanning electron microscopy and energy dispersive spectrum analysis are performed.The influence of water-cement ratio(W/C)and asphalt-cement ratio(A/C)on the properties of CEA slurry are studied.The optimal proportion of CEA is obtained by combining orthogonal analysis and fuzzy optimization theory.The result indicates that when A/C is 0.30-0.60,the content of free water in CEA slurry increases with the increase of W/C from 0.35 to 0.50.The contact between cement particles and emulsified asphalt is reduced,and the contact with free water is increased.The demulsification rate of emulsified asphalt and the formation of hydration products of cement slow down,which result in the increase of fluidity and consistency of CEA slurry.The compressive strength of solidified CEA blocks increases,and the demulsification time and coagulation time are extended.When W/C increases to 0.6,the content of free water increases.The excess free water evaporates during the coagulation process,which leads to the increase of pores in solidified CEA block,and the decrease of its compressive strength.With the increase of A/C,the content of free water in CEA slurry decreases,the contact between cement particles and emulsified asphalt increases,and the hydration of cement promots the demulsification of emulsified asphalt.Because of the high viscosity of bitumen particles and its inhibition on hydration of cement,the hydration products of cement are reduced,the compressive strength of cured CEA blocks is reduced,the fluidity and consistency of CEA slurry are reduced,the demulsification time is shortened,and the final coagulation time is prolonged.The optimal proportion of CEA slurry is with W/C of 0.4,and A/C of 0.4.
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