Effect of metal chelating agents on crack self-healing and mechanical properties of cement-based sealing materials

SI Leilei; WANG Yinghui; WEI Jianping; KONG Yadong; ZHAO Tongyu; SUN Feiyang; WANG Zhiming

doi:10.13225/j.cnki.jccs.W725.0433

Abstract：Grouting sealing quality is recognized as a critical factor ensuring gas drainage efficiency.Influenced by min-ing stress disturbance and slurry dehydration shrinkage,sealing materials tend to crack and form secondary fractures,lead-ing to gas leakage in drainage boreholes.To address this issue,a self-healing grouting sealing concept is proposed where sealing materials spontaneously react with environmental moisture and CO2 through self-healing agents to generate CaCO3 precipitation for crack closure when gas leakage occurs.However,the self-healing agent interferes with the hydration reac-tion of sealing materials and negatively impacts mechanical properties.Building on existing research,the content of self-healing agent is adjusted to balance self-healing capacity and mechanical performance.Results indicate that reduced self-healing agent content decreases crack-repairing capability.Specimen S1 achieves a maximum repairable crack width of 0.88 mm after 4 days of curing,while S2 and S3 specimens require 5 days to repair maximum crack widths of 0.73 mm and 0.71 mm,respectively.Meanwhile,mechanical properties improve significantly,with compressive strength increasing from 3.23 MPa(S1)to 4.31 MPa(S2)and 8.85 MPa(S3).To investigate self-healing agents' effects on pore-sealing ma-terials,microstructural and mineralogical analyses revealed that reduced agent dosage enhanced hydration product forma-tion and densification,forming a continuous network,while XRD indicated a mineralogical shift toward diminished un-hydrated clinker(3CaO·SiO2,2CaO·SiO2)peaks and intensified hydration product(C-S-H gel,Ca(OH)2)peaks.By optimizing the self-healing agent content,it is found that a 12％dosage achieves balanced self-repair capability and signi-ficantly improved mechanical performance.These findings hold substantial significance for regulating the self-healing properties and mechanical performance of sealing materials.