Study On Performance And Engineering Application Of Polymer-cement Matrix Composite Grouting Material

In view of the coal wall and roof caving on large mining face seriously affecting the efficient production,the advanced pre-grouting flexible reinforcement technology was proposed.Based on the advantages of low cost,non-toxicity and simple construction technology,the single liquid cement was modified by VAE emulsion.In this paper,the compressive strength,bending strength,bonding strength and compressive strength of VAE modified Portland cement and VAE modified aluminate cement were discussed.The results showed that when the curing age was 28 d and P/C=3%,the compressive strength and flexural strength of VAE modified common Portland cement calculi reached a peak value of 30.0MPa and 5.95 MPa,and the compressive strength and flexural strength of common silicate calculi increased by6.8% and 16.9% respectively compared with that of ordinary silicate slurry with P/C=0%.When P/C=5%,the compressive strength and flexural strength of VAE modified aluminate cement calculi reached a peak value of 40.3MPa and 7.13 MPa,and the compressive strength and flexural strength of aluminate cement calculi increased by 8.0% and 13.0% respectively compared with that of P/C=0%.VAE modified cement-based materials and coal bonding strength have been greatly improved.When the curing age is 28 days,P/C=8%,VAE modified Portland cement and VAE modified aluminate brine mud and coal bonding strength reached the peak of 0.89 MPa and0.95 MPa,compared with P/C=0% cement mud and coal bonding strength increased by89.4% and 90%.VAE modified cement-based materials have better reinforcement effect on coal.When the curing age is 28 days,P/C=5%,VAE modified Portland cement and VAE modified aluminate cement and coal consolidated body compressive strength reached the peak of 19.7MPa and 22.6MPa,compared with P/C=0% slurry and coal consolidated body compressive strength increased by 30.5% and 40.4%,respectively.The modification mechanism of VAE emulsion and the interface transition zone structure(ITZ)between slurry calculi and coal were analyzed by scanning electron microscopy(SEM).The analysis results show that when the ash accumulation is small,VAE film is not dominant in the overall structure,a small number of VAE film filling in the calculous body pores or structural pores.As the poly ratio increased,VAE films and cement hydration products formed an organic-inorganic interpenetrating three-dimensional network structure.VAE film ACTS as a "bridge" in the calculous body,improving the stress state caused by volume shrinkage of the calculous body,thus limiting the spread of microcracks in the calculous body.When the ash is relatively large,VAE emulsion in the structure of the formation of the film is thicker,wrapped hydration products can not effectively wear out VAE film,so as to inhibit the growth and migration of crystals.At the same time,VAE emulsion was mixed into the cement-based materials,which improved the structure of the interfacial transition zone between the stone body and the coal body,effectively reduced the fracture width of the interfacial transition zone,and improved the bonding force between the composite slurry and the coal body surface.Finally,through the combination of industrial experiment and laboratory experiment,it is determined that the material is suitable for large mining and high flexible grouting reinforcement.