Experimental Research On A Kind Of Prestressed Pore Pressure Slurry With Large Fluidity

In recent years,Chinese infrastructure construction has advanced by leaps and bounds,the proportion of highway and railway bridges has increased,and post-tensioned prestressed bridges have become more widely used.Post-tensioned prestressed tunnel grouting is a key technology for post-tensioned prestressed bridges.Good channel grouting is extremely important for ensuring the safety and durability of bridges.However,more and more press slurry now has shortcomings such as insufficient fluidity,bleeding segregation,low performance,low compressive strength and low flexural strength.In response to these shortcomings and engineering requirements,it is urgent to develop a large fluidity Prestressed channel press slurry to meet the application requirements of the project.By studying the choice of four water-reducing agents such as polycarboxylate superplasticizer,naphthalene water reducer,aliphatic water reducer and amino sulphonate series superplasticizer,systematically explore the four water-reducing agents for prestressed pore pressure slurry Due to the influence of fluidity,it was found that the polycarboxylic acid water-reducing agent can maintain the large fluidity of the press slurry while maintaining a small dosage,and can ensure that the press slurry does not leak or segregate.The polycarboxylate superplasticizer can effectively improve the pore structure of the press slurry,making the interior more dense and the strength can be further improved.On the basis of ensuring that the press slurry has large fluidity,three mineral admixtures of ultra-fine fly ash,ultra-fine ore powder,and micro-beads are added for single-factor analysis.Experimental studies have shown that The initial fluidity and the fluidity after one hour have the greatest impact,but it has an adverse effect on the strength of the pressed slurry,and too many microbead parameters will cause the surface of the pressed slurry to blacken and produce bleeding.The ultra-fine ore powder has a positive effect on the compressive strength of the press slurry,which can effectively avoid the problem of the early strength reduction of the press slurry.The addition of the ultra-fine fly ash will correspondingly improve the fluidity and later resistance of the press slurry Fold strength,but will reduce the early compressive strength of the press slurry.And through the compounding of the mineral admixture,the performance of the press slurry is comprehensively improved.It is found that the addition of anhydrous gypsum plays a great role in improving the fluidity and other properties of the slurry.When the amount of gypsum is in a certain range,the fluidity of the slurry will be accelerated,and the compressive and flexural strength of the slurry will also be improved.The addition of gypsum will make the paste not shrink at the later stage,and greatly improve the free expansion rate of the paste at 3 h and 24 h.By means of XRD test and TG quantitative analysis,it is shown that gypsum can greatly promote the hydration reaction,increase the amount of hydration products,increase the amount of ettringite from less to more,and make the internal structure more compact.At the same time,wollastonite gypsum will be generated in the later stage,which can effectively avoid the shrinkage phenomenon of the strength in the later stage of slurry pressing,and thus effectively improve the physical properties of slurry pressing.SEM test showed that when gypsum content was 2%,calcium silicate gel developed toward high density calcium silicate gel in the early stage and promoted hydration reaction,which made the slurry more hydrated in the early stage.