Research On The Performsnce Of Green Cement-Based Grouting Materials From Activated Stimulated Solid Waste

With the continuous development of China’s economy,industrialization and urbanization,a large amount of construction and industrial waste has been generated,and the current situation of Chin’s construction waste and industrial waste disposal is not optimistic,mainly using landfills and open piles,with low recycling rate and great harm to the environment.Under the guidance of the concept of ecological civilisation,the Fifth Plenary Session of the 19th Central Committee has clearly pointed out the need to“improve the utilisation rate of resources”,and the 14th Five-Year Plan has clearly pointed out the need to“promote the resourceisation of solid waste,improve the utilisation rate of resources,improve environmental quality,promote comprehensive economic and social development,and accelerate green transformation”.The contradiction between the ban on mining of natural sand and gravel aggregates and the huge demand for engineering construction is increasing,which makes the research on the recycling of solid waste urgent.In order to improve the utilisation rate of recycled materials and reduce the cost of cement-based grouting materials,this experiment uses two solid wastes,recycled fine aggregate and iron tailings,to study the active excitation of recycled materials;the samples were analysed using an orthogonal design method combining X-ray diffraction and scanning electron microscope characterisation to optimise the proportion of each material;and the reinforcement effect was tested using numerical simulations.Details of the study are as follows:（1）In order to improve the activity of the recycled materials prepared by solid waste,different ways were studied to activate the recycled materials,which lays a theoretical foundation for their application in cement-based materials.Through indoor test,the effect of physical excitation（mechanical grinding）and chemical excitation（hydrochloric acid and ethylene glycol）on the activity of iron tailings powder,and the effect of alkali excitation（sulfate and water glass）on the activity of concrete recycled fine aggregate（construction waste）were analyzed.The 28d compressive strength was determined,and the compressive strength ratio K was calculated and analyzed together with X-ray diffraction and scanning electron microscopy.The specific surface area of iron tailings powder and the specific surface area increased less after grinding,increased 53.1m²/kg,the effect of grinding and hydrochloric acid reagent treatment was better,and the specific surface area increased 64.4m²/kg.After grinding iron tailings powder and treating with 2%hydrochloric acid solution,the compressive strength can reach 124.24%;After the recycled fine aggregate of concrete is soaked with 3%calcium sulfate solution,the compressive strength can reach 109.80%.（2）By designing orthogonal tests,the above activation-treated construction and industrial wastes were studied for use in cement-based grouting materials.The effects of five factors,namely water-cement ratio,recycled fine aggregate,cement-sand ratio,iron tailing powder and fly ash,on the basic properties of the grouting materials were discussed,and tests were conducted on the flow rate at 0 min and 30 min,flexural and compressive strengths at 1d,3d and 28d,and X-ray diffraction and scanning electron microscope analysis.The test results show that under the condition of 28d as the final strength standard,the orthogonal polar difference analysis reveals that the water-cement ratio has the greatest influence,the cement-sand ratio has the least influence,and the influencing factors are water-cement ratio,fly ash,recycled fine aggregate,iron tailing powder and cement-sand ratio in the order from high to low;X-ray diffraction and scanning electron microscope analysis reveal that construction and industrial solid waste can be better adapted to cement-based grouting materials,which can promote It can promote the hydration reaction,fill the voids and improve the strength.A more reasonable combination of factors is A₁B₃C₄D₂E₂,i.e.water-cement ratio（A）is 0.36,cement-sand ratio（B）is 1:0.8,recycled fine aggregate dosing（C）is 40%,iron tailing powder dosing（D）is 8%and fly ash dosing（E）is 8%.（3）To investigate the application of cementitious grouting materials obtained from the above tests in the reinforcement of existing building structures,the reinforcement of reinforced concrete beams with cementitious grouting materials was simulated using ABAQUS numerical simulation.The reinforcement with increased cross-section is used to analyse the forces as well as the deformation of the reinforced concrete beam before and after reinforcement.The results show that the longitudinal reinforcement can withstand greater loads after strengthening,with an average increase of 10%-15%.Under the same load,the spanwise deflection of the reinforced beam becomes smaller and the maximum deflection is reduced by 42.8%.Therefore,the above cementitious grouting material reinforcement is effective and can improve the force deflection of the building structure.