Performance Optimization And Engineering Application Of Duct Grouting Materials

The grouting materials is a cement paste composed of various admixtures,mineral admixtures,cement and water.It is generally used in post-tensioned prestressed duct grouting and other projects.It can protect the prestressed tendons from external ion corrosion,increase the adhesion between concrete and steel bars,and reduce the fatigue damage of anchors.The price of grouting materials on the market is high,the quality is uneven,and there are problems such as poor slurry stability,low fluidity,shrinkage,etc.Slurry stability is the ability to keep uniformity over time before slurry hardening.When the stability of the duct grouting materials is poor,the solid particles with higher density will settle under the action of gravity,free water movement,leaving the water channel inside the hardened slurry,affect safety and durability of structural.In addition,the slurry stability test method in the current standard is single and low in operability.In view of the above problems,this paper introduces the slurry deposition density ratio test method,using mineral admixtures such as microbeads as mineral stabilizing components,cellulose ether,starch ether and maltodextrin as organic thickening components,with CSA expansion agent and plastic expansion agent as micro-expansion components and defoaming agent as defoaming component.The effects of mineral stabilizing components and organic thickening components on the stability of pore grouting material slurry were studied,and the effects of various components on the fluidity,setting time and mechanical properties of the grouting material and SEM,XRD and Mercury intrusion.Finally,a grouting material with excellent slurry stability and basic properties is prepared,which is applied to repair and damage the bridge of Jiujiang Bridge.The experimental results show that:By incorporating 10% microbeads into the duct grouting material,the slurry deposition density ratio can be increased to 0.89.When the starch ether is blended,the slurry deposition density ratio can be increased to 0.95 or more,and the bleeding rate is reduced to 0.When the content of starch ether was 0.011%,the slurry deposition density ratio reached 0.97,and the initial,30 min and 60 min fluidities were 15.1s,15.9s and 16.7s,respectively,the slurry fluidity was the best.The slurry stability of the duct grouting material is more scientific and comprehensive with the slurry deposition density ratio and the bleeding rate.Getting the best mix ratio when the water-gel ratio is 0.28,the JS-6 content is 0.4%,the microbead content is 15%,the starch ether content is 0.011%,the CSA expansion agent is 3.4%,the plastic expansion agent is 0.02%,and the defoaming agent is 0.02%.At this time,the slurry deposition density ratio reached 0.97,the bleeding rate was 0,the initial fluidity was 14.8 s,the 60 min fluidity was 17.9 s,and the compressive strengths at 7d and 28 d were 61.3 MPa and 78 MPa,respectively.All performances meet the technical requirements of the d grouting material.The slurry deposition density ratio of the duct grouting material is greater than 0.95,the bleeding rate is 0,the initial fluidity is about 15 s,the fluidity of 60 min is less than 20 s,the compressive strength of 7d,28 d can reach 55 MPa,65MPa or more,and all performances meet the technical requirements of the channel grouting material,when the amount of JS-6 polycarboxylate water reducing agent is 0.4%,the amount of microbeads is 15%,the amount of starch ether is 0.009%~0.015%,and the amount of CSA expansion agent is 1.7%~5.1%,the dosage of the plastic expansion agent is 0.02%~0.04%,and the dosage of the defoamer is 0.02%~0.03%.The duct grouting materials is applied to the repaired bridge deck of Jiujiang Bridge.The slurry deposition density ratio reached 0.97,the initial fluidity was only 14.6s,the fluidity was only 18.2s after 1h loss,and the 28 d compressive and flexural strength values reached 74.1MPa,14.6MPa,endoscopic detection and slotting test results are good.