Preparation And Modification Mechanism Of Waterborne Epoxy Resin Modified Composite Grout Material

With the development of deep underground engineering in China,geological disasters such as deformation and permeability of deep surrounding rock occur frequently in engineering construction,which puts forward more stringent requirements for the performance and functionality of grouting materials in soft surrounding rock under high ground stress.The defects of traditional cement-based grouting,such as weak early strength,poor toughness,weak resistance to dynamic water scouring and poor slurry stability,are becoming increasingly prominent.Moreover,the characteristics of high carbon emissions in the cement production industry are not conducive to China’s early completion of the tasks of"carbon peaking"and"carbon neutralization"of ecological civilization.It is of great significance for the development of deep grouting engineering to develop a new grouting slurry with high strength,high toughness,strong dynamic water scouring resistance,good durability,high stability,low carbon,environmental protection and economy.In this paper,ordinary Portland cement is used as the matrix material,water-borne epoxy resin and curing agent are used as the main modification materials,and a new interface coupling agent of silane coupling agent nano-silica composite is designed and prepared to improve the reaction activity and connection strength of organic and inorganic phases in composite grouting.A new grouting material with the characteristics of high strength and toughness and the combination of organic and inorganic materials was developed.The rheological properties,mechanical properties,erosion resistance and modification mechanism of the material were tested and analyzed.The main research contents and achievements of this paper are as follows:（1）choose bisphenol-A waterborne epoxy resin emulsion,curing agent,TBP and OPC to prepare polymer-cement composite grout material.Taking the analysis results of fluidity,flow time,rheological curve,laser particle size distribution and zeta potential as evaluation indexes,the effects of the composition of WBER,polymer-cement ratio（P/C）and water-cement ratio（W/C）on the rheological properties of polymer cement-based grout materials were studied,and the modification mechanism of WBER on the rheological properties of cement-based materials was revealed.The results show that the fluidity of composite paste first increases and then decreases with the increase of P/C,and the optimum fluidity content is about 2.5%;The flow pattern of the composite paste is closer to the Vipulanandan rheological model.Under the conditions of low W/C and high P/C,the paste has obvious shear thinning phenomenon.The average particle size of the composite paste decreases and the initial fluidity can be maintained for a longer time.Cement and polymer particles have opposite zeta potential and exhibit electrostatic attraction characteristics.The absolute potential of zeta in suspension increases first and then decreases.The modification of WBER can improve the uniaxial compressive strength（UCS）and splitting tensile strength（STS）of composite grout materials,and significantly improve the brittle failure characteristics of cement-based paste.The UCS increases first and then decreases with the increase of P/C,and the STS increases continuously with the increase of P/C.The best P/C of compressive strength is 5%～10%,and the maximum increase is 38.9%.The optimum P/C of STS is 20%,and the maximum increase is 120.2%;In terms of limit strain,when the content of WBER is low,the limit strain increases slightly.When the P/C is greater than 10%,the limit strain increases significantly and can be increased to 4.2%.The modification mechanism of WBER on cement-based materials was studied.The distribution characteristics and micro morphology of polymer in cement-based materials in fresh-state and after curing were characterized by scanning electron microscope（SEM）,field-emission scanning electron probe（EMPA）and laser confocal microscope（CLSM）.The effect of WBER on cement hydration products was analyzed by X-ray diffraction（XRD）,Fourier transform infrared spectroscopy（FT-IR）and thermogravimetric analysis（TGA-DTG）,and the action model of WBER modified cement-based materials was put forward.（2）A new type of interfacial coupling agent suitable for organic-inorganic composite grout material system was designed and prepared by grafting nano-silica particles after hydrothermal treatment onto silane coupling agent molecules.The preparation conditions of silane coupling agent and nano-silica composite particles were optimized through the parameters of grafting rate,mechanical properties and rheological properties:a)the pre-hydrolyzed silane coupling agent can produce more intermediate products containing Si-OH bond,and then react with CH and C-S-H to produce more composite hydration products.The pre-hydrolysis step of silane coupling agent is necessary;b)The composite particles prepared with KH-560 silane coupling agent have the best modification effect on the UCS and STS of grout material.The strength value is about 19.6%and 52.6%higher than that of polymer-modified grout,respectively.The grafting rate of KH-560 group was the highest by TGA analysis;c)Hydrothermal treatment（50℃）and reaction heating（80℃）of nano-silica can effectively increase the grafting rate of nano-silica.The modification mechanism of interfacial coupling agent was explained by TGA,XRD and FT-IR.（3）The polymer cement-based grout material is further modified with KH560-SiO₂interface coupling agent:the addition of KH560-SiO₂can further improve the mechanical properties and bonding ability of polymer grout material while retaining its high toughness;For the fluidity of paste,there is the best amount of KH560-SiO₂（about1%）.A small amount of KH560-SiO₂ can enhance the fluidity of suspension and enhance the zeta potential of suspension;CH in the hydration products of modified cement was consumed a lot,and more C-S-H gels were generated.The grafted nano-silica has higher reaction activity and plays a stronger role in promoting the hydration process of cement.（4）The two modification methods of WBER and KH560-SiO₂can effectively improve the paste retention rate of cement grout materials under the condition of dynamic water scouring and enhance the anti-dynamic water scouring performance of cement-based grout materials;The two modification methods can effectively reduce the mass loss rate of hardened grout eroded by salt solution and improve the strength erosion coefficient.The two groups of polymer-modified samples have better sulfate and sulfate chloride corrosion resistance than neat cement paste samples;After polymer modification,the erosion microstructure of the material changes from through micro cracks to dispersed micro pores.The polymer can effectively delay the corrosion of sulfate ions to CH.After KH560-SiO₂ is added,the amount of ettringite and C-S-H in the hydration product increases,and the sample has higher hydration degree and stronger salt solution corrosion resistance.