Experimental Research On The Mix Proportion Design And Performance Optimization Of Reinforced Sleeve Grout

The reliability of the connection of prefabricated concrete buildings affects the integrity and stability of the building structure.Grouting sleeve connection is a common method for node connection of prefabricated components.Grout is used as the main material for node connection to improve its mechanical properties and volume stability.Grout can improve the mechanical properties and volume stability of the sleeve joint,enhance the bearing capacity of the joint,and provide a technical reserve for the development of prefabricated buildings towards super high-rise buildings.At present,in view of the fact that the grout is prone to generate large self-shrinkage problems,this subject explores the factors affecting the mechanical properties and volume stability of the grout.In this study,the effects of water-binder ratio,binder-sand ratio,silica fume content,and slag content on the flow and mechanical properties of grout were explored using orthogonal test methods.In this test,a comparative test method was used to explore the effects of different magnesia expansion agent dosages and different curing conditions(standard curing,sealed curing,dry curing)on the mechanical properties and volume stability of the grout.At the same time,the micropore structure of the grout was tested using the mercury intrusion borehole method,in order to clarify the relationship between the micropore structure and the macro performance.The results showed that:The water-binder ratio is the main factor that affects the sleeve grout flow performance and early or late mechanical properties;the rubber-sand ratio is the main factor that affects the early compressive strength of the sleeve grout.With the development of age,the strength of the cement slurry gradually improved,the interface between the aggregate and the slurry changed from weak to strong,and the failure mode of the specimen changed from crystalline to penetrating.When the slag content was 15% and silica fume content was 6%,the sleeve grout had better flow and mechanical properties.With the increase of the amount of magnesia expansion agent,both the initial mobility and the 30-minute mobility of the grout significantly decreased,and the loss over time gradually increased.Magnesium oxide expansion agent replaces the slag in the grouting system,which can increase the alkalinity of the slurry and accelerate the response of the plastic expansion agent,thereby increasing the vertical expansion rate of the grout.The compressive strength was not greatly affected by the amount of magnesia expansion agent.Compared with the blank group,the test group with a content of 12%,the compressive strength at 28 days under standard curing decreased by about 12%.The main reason is that the addition of magnesia expansion agent reduces the concrete compaction,and further verified by the mercury intrusion test,the test group with the magnesia expansion agent has a larger porosity,and the denseness of the hardened slurry is relatively low.Under standard curing,the 28-day swelling deformation rate of the test group with 12% content is about 0.035%.Under sealed curing,the free deformation of the grout always appears as shrinkage deformation,but the shrinkage deformation first increases and then decreases,and the shrinkage deformation at 28 d is about 0.002%.The mix ratio of grout obtained in this experiment is 0.22 water glue ratio,0.8 cement sand ratio,6% silica fume content,9% slag content,6% magnesium oxide expansion agent,0.6% polycarboxylic acid water reducer and 0.03% plastic expansion agent.Its volume stability and flow performance are better than two commercial grouts.The compressive strength of grout with low water to binder ratio is greatly affected by curing conditions.The variation law of compressive strength is: standard curing > sealed curing > dry curing.Volume free deformation is also affected by curing conditions.the variation law is: standard curing > sealed curing > dry curing.Under standard curing,with the increase of the amount of magnesia expansion agent,the porosity of the slurry gradually increases,and the number of harmful pores increases;the decrease of the curing humidity will result in the increase of the porosity of the slurry and the increase of harmful pores.