Study On Development Of High Belite Sulphoaluminate Cement-based(HOC) Fracture Grouting Material And Related Mechanism

“Carbon peaking by 2030 and carbon neutrality by 2060”are listed as one of the key tasks of ecological civilization construction.In the field of grouting engineering,high belite sulphoaluminate cement（HBSC）has become one of the future development trends of green grouting materials due to its low energy consumption and low CO₂ emissions.This dissertation aims at providing theoretical and technical support for the compilation of relevant contents of fracture grouting in Shanxi local standard"grouting technical regulations",based on the theory of cement reconnection,and closely combining with engineering practice,to the grouting material of high belite sulphoaluminate cement The compound and its related mechanism were studied.Taking high belite sulphoaluminate cement as matrix material,and introducing coal measure metakaolin（CMK）and ordinary portland cement（OPC）to form ternary grouting material（HOC）,the test scheme was designed by using the method of“uniform design”.Firstly,through a series of physical and mechanical properties tests,the high belite sulphoaluminate mud based fracture grouting material with adjustable performance was developed;secondly,through the flow uniformity test of HOC fracture grouting material and fluent numerical simulation,the time variation characteristics of fluidity,migration and diffusion law and grouting plugging mechanism were revealed;finally,EIS,XRD and SEM were used to characterize the hydration process,hydration products and microstructure of HOC fracture grouting material,revealing its hydration and durability mechanism.The main achievements are as follows:（1）Aiming at the fracture grouting material,through a series of physical and mechanical properties tests,the relationship between the composition and properties of HOC fracture grouting material was studied,and the high belite sulphoaluminate cement-based fracture grouting material with excellent performance,resource saving and green environmental protection was developed with reference to the analysis results of resource saving and carbon emission（authorized invention patent No.:ZL 2018 1 1512312.5）.Among them,P15 has the best comprehensive performance,which can save 27.73%of limestone consumption,15.78%of standard coal consumption,and CO₂ emission reduction rate of 19.23%.P12 with fast setting characteristics can meet the requirements of special engineering.P16 with excellent mechanical properties can meet the requirements of reinforcement engineering,which has broad application and promotion value.（2）By analyzing the stress-strain curves of crack grouting material under the conditions of standard curing,clear water curing,salt corrosion environment and freeze-thaw cycle,the change rules of elastic modulus and ultimate strain are studied;Considering the brittle failure characteristics of grouting material,based on the“composite power exponential model”（CPE model）,a modified“composite power exponential model”for crack grouting material of HOC is proposed,the relevant parameters of CPE model under different conditions are given.（3）Through the fluidity test of the HOC fracture grouting material,it is revealed that the fluidity time curve has significant time-varying characteristics,and can be divided into three stages:slow stage,fast stage and stable stage;The diffusion model of single fracture grouting is established by FLUENT simulation software.The diffusion law of fracture grouting is studied by using the generalized Bingham fluid constitutive equation based on the viscosity time-varying of HOC fracture grouting material.The mechanism of fracture grouting sealing is revealed,the results show that:the advantages of HOC fracture grouting material are reflected in its large diffusion range,high uniformity and less dynamic water erosion loss;the most favorable time period for the formation of solidified plugging body is t₂-t₃,that is,the grouting material diffuses to the solid wall boundary but not to the outlet boundary;for other situations that can not effectively block groundwater,the grouting rate and material ratio can be adjusted and so on.（4）Based on the study of macroscopic physical and mechanical properties,the hydration process,hydration products and microstructure of HOC fracture grouting material were characterized by EIS,XRD and SEM,and the hydration mechanism was revealed.The study shows that the hydration process of HOC grouting material is mainly controlled by two stages.The first stage is the joint control of sulphoaluminate phase and gypsum,mainly forming AFt and AH₃,which can form the framework of HOC fracture grouting material.The second stage is hydration of two calcium phase silicate,which mainly generates C-S-H gel,which can play the role of caulking and cementation,and improve the density of HOC fracture grouting material.（5）The long-term immersion system was used to study the deterioration rule of HOC fracture grouting material under the erosion condition of single sulfate solution and sulfate chloride combined solution.The durability mechanism of HOC fracture grouting material was revealed by EIS,XRD and SEM.The results show that HOC fracture grouting material exhibits excellent sulfate resistance.When a single sulfate attack occurs,the main products are AFt and C-S-H gel without AFm because of the presence of SO₄^2-,while the presence of chloride salt inhibits the formation of AFt and promotes the formation of Friede’s salt.The erosion and damage of acid salt play a certain role in delaying.（6）The freeze-thaw cycle system was adopted to study the freeze-thaw cycle resistance characteristics of HOC fracture grouting material with mass change,relative dynamic elastic modulus and mechanical properties as evaluation indexes.The deterioration law is analyzed by combining with EIS.The results show that with the increase freeze-thaw cycles,the internal damage degree of HOC fracture grouting material increases,the path of connected pores increases,the structure becomes loose,and the physical and mechanical properties of the material also decreased correspondingly,but the HOC fracture grouting material still showed good freeze-thaw cycle resistance.The relevant content of HOC fracture grouting material studied in this dissertation can provide theoretical and technical support for Shanxi local standard“grouting technical specification”and other relevant standards.At the same time,as an environmental protection grouting material with high performance,low energy consumption and low emission,the application and promotion of HOC fracture grouting material can increase the coordination with the environment,which is in line with the development concept of ecological civilization construction.It is of great practical significance to achieve the goals of“reaching the peak”and“carbon neutralization”.