Research On Mechanical Properties Of Graphene Oxide-fly Ash Modified Cement-based Grouting Material

The mechanical properties and fluidity of cement-based grouting material are the key factors affecting the reinforcement effect of broken rock in rock engineering,and it is very important to maintain the structural stability of broken surrounding rock.However,the current research on the relationship between the strength and fluidity of cement-based grouting material is not perfect.Therefore,this paper first studied the mechanical properties and flow properties of graphene oxide-fly ash modified cementbased grouting material through experiments.Secondly,combined with molecular dynamics simulation,the elongation mechanism of graphene oxide on cement-based grouting material was revealed.Then,the optimal proportion of modified cement-based grouting material was obtained through experiments,and its mechanical properties after grouting reinforcement of broken rocks were analyzed.The main conclusions are as follows:(1)The mechanical strength and microstructure characteristics of graphene oxidefly ash modified cement-based grouting material were studied by field emission electron microscopy and mercury injection method combined with mechanical test.The results show that graphene oxide changes the morphology of hydration products,reduces the porosity of cement-based grouting materials,and enhances the compressive,tensile and shear strength of cement-based grouting materials.The existence of fly ash makes up for the influence of graphene oxide on the fluidity of grouting material,which makes the slurry have better fluidity and saves the amount of cement material.The optimal proportion of the two was obtained through experiments,that is,fly ash combined with 0.08 wt.% graphene oxide to replace 20 % of cement material.Without affecting the mechanical properties of grouting material,it not only reduced the amount of cement material,improved the utilization rate of fly ash waste residue,but also enhanced the fluidity of slurry.(2)The microscopic molecular model of cement-based grouting material containing graphene oxide was established,and the influence of graphene oxide on the mechanical behavior of C-S-H gel under microscopic tensile action was studied at the atomic scale.The mechanism of delaying the fracture failure of materials and enhancing the ductility of materials was expounded.The simulation results show that the presence of graphene oxide greatly improves the ductility of the material,and the graphene oxide bridged at the structural fracture plays a decisive role in the ductility of the material.Due to the existence of bridging graphene oxide,the energy required for the fracture of the material structure and the external work of the system increase;On the contrary,the unbridged graphene oxide reduces the two,and the number of bridged graphene oxide has a great influence on the fracture energy of the model.(3)The best graphene oxide – fly ash ratio was used to modify the cement-based grouting material,which was used to reinforce the broken rocks,and the mechanical properties of the modified grouting material for reinforcing the broken rocks were analyzed.It is found that the existence of graphene oxide in graphene oxide-fly ash modified cement-based grouting material not only improves the compressive strength and elastic modulus of broken rocks,but also reduces the acoustic emission count and amplitude of the sample in the initial compaction stage,effectively inhibits the generation and propagation of micro cracks under load,so that the sample remains good integrity and improves its toughness.From the microscopic morphology and fractal characteristics of the fracture surface,the existence of graphene oxide makes the fracture surface structure maintain good integrity,and reduces the fractal box dimension of the fracture surface,that is,reduces the degree of damage and deterioration of the fracture surface,and improves its ability to resist load.There are 53 pictures,21 tables and 129 references.