Preparation Of Sulphoaluminate-based 3D Printing Cementitious Materials By Industrial Solid Waste

During the rapid development of China's industrialization process,a large amount of industrial solid waste was generated.The low utilization rate of industrial solid waste causes its large accumulation,and the large amount of accumulated industrial solid waste will pollute the atmosphere,water and even endanger human health.The use of industrial solid waste to prepare building materials is a way to use industrial solid waste on a large scale,but the contradiction between the comprehensive utilization rate of solid waste and the added value of products in this process hinders the further development of this approach.In order to solve the massive accumulation of industrial solid waste,this paper combines the two concepts of solid waste synergistic complementarity and value transition,and innovatively proposes the research topic of"Preparation of sulfoaluminate-based 3D printing cementitious materials from all industrial solid waste".This article will be carried out in accordance with the process plan of "Efficient pretreatment of industrial solid waste—Industrial solid waste synergistically prepares high-performance sulfoaluminate cementitious materials—Preparation of 3D printing materials of building with cementitious materials".Achieve the separation,regeneration,and value reconstruction of industrial solid waste,and form a solid waste overall resource,green and high-value technical system Solve the contradiction between product performance and cost in the process of resource utilization of solid waste,and realize the true transformation of solid waste into treasure and large-scale resource utilization.The main work carried out in the article is as follows:1.The municipal solid waste incineration fly ash was selected as the main raw material for the preparation of sulphoaluminate cementitious material,and the pretreatment of fly ash was studied.Water washing treatment was selected as the pretreatment process of fly ash,and then the influence of water washing conditions on the chlorine removal efficiency of fly ash,the mineral composition and morphology of fly ash was studied.The mechanism of dechlorination of water-washing,the mineral composition and morphology change mechanism of fly ash were analyzed,and the best water washing process was obtained.The composition of fly ash water washing liquid was preliminarily explored,the influence of water washing conditions on the pH value of fly ash water washing liquid,the weight of the extracted materials and the mineral composition of water washing liquid were studied.The best water washing process is:two water washings with a water-to-solid ratio of 3,the first water washing is 60 min,the second water washing is 30 min,and the water washing temperature is controlled to 25?.After pretreatment,the chloride content in fly ash can be reduced to 1%,and the residual chloride is mainly FeOCl that is difficult to remove with water washing.The different washing conditions will have a certain effect on the pH value of the fly ash washing solution,the quality and composition of the extracted substances in the washing solution.2.Using three solid wastes of fly ash,desulfurized gypsum and aluminum ash as raw materials,a study on the preparation of solid waste-based sulfoaluminate cement materials was carried out.The three-modulus method and material balance were used to calculate the ingredients,and the effects of calcination temperature on the chemical composition,mineral composition and strength properties of the cementitious materials were studied.Based on the above research results,the best preparation process of the cementitious material was obtained:the raw material was kept at the calcination temperature of 1270? for 30 min.Under this condition,the cementitious material prepared has the best hydraulic mineral content and the best strength characteristics.The 1,3,and 28-day strengths of the material were 44.1 MPa,69.8 MPa,and 93.4 MPa,respectively.The strength performance is better compared with similar fly ash-based cementitious materials for the same curing time.Aiming at the best-performing cementitious material,the curing ability of the eight heavy metals was studied.The material has a good curing effect on heavy metal ions,and the leaching concentrations of eight heavy metal ions in samples of each hydration age of the material tested are far below the national standard concentration limit.A life cycle assessment of the material was conducted,and the results showed that the solid waste source sulfoaluminate cementitious material had less impact on the environment than traditional sulfoaluminate cement.3.Based on the solid waste source sulphoaluminate cementitious material as the basic material,the experimental research on the preparation of 3D printing materials of building was carried out.The research content includes:the influence of a single admixture on the performance of cementitious materials and its mechanism analysis;the study of the influence of the amount of aggregate and the type of fiber addition on the strength of mixed materials;the ingredients and performance testing of 3D printing materials;3D printing for construction;cost analysis of the entire process from solid waste to building 3D printing materials.The effect of admixtures on the properties of cementitious materials conforms to a certain law.Appropriate addition of additives can improve the fluidity and setting time of cementitious materials.Based on the sulphoaluminate cementitious material,a high-performance 3D printing material can be prepared,and the components printed with this material have good appearance and strength.The entire production process from solid waste to 3D printing materials of building has high economic benefits.The idea of "preparation of sulphoaluminate-based 3D printing cementitious materials from industrial solid waste" has important practical significance.It can break through the single solid waste composition,characteristics and value limits,and solve the contradiction between product performance and cost in the preparation of solid waste construction materials.It can open up new ways for the industrial development of green building materials and provide theoretical guidance for the large-scale utilization of industrial solid waste.