Quantitative Analysis Of Carbon Emission Of 3D Printing Building Structure Based On Life Cycle Assessment

In recent years,the application of concrete 3D printing technology in the field of civil engineering has been rapidly developed,and it is considered to be a possible alternative to traditional concrete construction methods in the future,mainly because the high degree of automation improves productivity and construction accuracy,reduces construction safety risks and the potential environmental impact of the construction industry.At present,however,the quantitative analysis and research on the environmental impact of 3D printing buildings and bridge structures is limited at home and abroad.Based on the current situation,this paper uses the life cycle assessment method(LCA)to quantitatively analyze the environmental carbon emissions during the construction of 3D printing buildings and bridge structures,and compares them with traditional construction schemes.A comparative analysis was made to evaluate the impact of architectural 3D printing technology on the global warming potential(GWP).The specific research carried out in this article and the corresponding conclusions are as follows:(1)Firstly,the concept of life cycle assessment and the application of life cycle assessment in the field of civil engineering are introduced.Secondly,the carbon emission analysis methods and calculation methods recognized at home and abroad are introduced and compared,and the carbon emission factor method is determined as the method used for carbon emission accounting in this paper.Through a large number of relevant codes or standards at home and abroad and academic papers,the carbon emission factors such as energy,building materials,raw materials and construction machinery are compared,selected or modified on this basis,and finally determined for the later carbon emission accounting process.(2)Taking a small and medium-sized building built by 3D printing contour technology as the prototype,this paper designs three structural schemes: brick concrete,cast-in-situ concrete frame and concrete 3D printing.Aiming at the materialization stage(from cradle to site)of the main stress components of various schemes,this paper compares and analyzes the carbon emission effects caused by the consumption of building materials,energy and labor.The results show that regardless of the structure type,the carbon emission in the material production stage accounts for the absolute proportion of the total carbon emission in the materialization stage,and the carbon emission in the material transportation stage and construction stage accounts for a small proportion.Compared with the traditional construction technology,3D printing technology has certain carbon reduction advantages in the materialization stage.The traditional construction carbon emission is mainly due to the high demand for formwork and reinforcement in the material production stage,while the 3D printing construction carbon emission is mainly due to the high cement consumption in the material production stage and the high power consumption in the construction stage.(3)Through the sensitivity analysis of the carbon emission effect of 3D printed concrete under different mix proportions,it can be seen that the cement dosage of 3D printed structure in the material production stage plays a decisive role in the carbon emission effect,and the carbon emission factor of 3D printed concrete can be significantly reduced by adding industrial waste and fiber,adjusting the aggregate content and reducing the cement dosage.During the transportation of building materials,the increase of aggregate has little impact on the carbon emission in the physicochemical stage.It can be seen that the optimization design of 3D printing concrete mix proportion can further improve the carbon reduction advantage of 3D printing construction.(4)In order to further explore the carbon emission of 3D printing construction and traditional construction in bridge engineering,taking a pedestrian bridge as an example,on the premise of comprehensively considering the bridge safety,aesthetics and economic indicators,the topology of the main structure of the bridge is optimized,and the material parameters and construction process information of special-shaped components are refined through BIM Technology;On this basis,for the special-shaped concrete substructure of the bridge,the carbon emission effects of three construction schemes of full 3D printing construction,3D printing + traditional construction and full traditional construction in the materialization stage are compared.The results show that due to the high energy consumption of 3D printer and the high carbon emission of 3D printing concrete materials,compared with the other two schemes,the carbon emission in the materialization stage of special-shaped pier constructed by 3D printing +traditional construction method is the lowest,because this hybrid construction method not only reduces the use of cement,but also improves the construction efficiency and avoids the use of formwork.The construction period of the full 3D printing scheme completely depends on the 3D printer,and different matching ratios of 3D printing materials have different effects on the final carbon emission results,so there is great uncertainty.Secondly,the full 3D printing construction has inconvenient operation when arranging reinforcement.Similar to housing construction,the traditional construction scheme of the bridge still has a large carbon emission effect in the formwork project,especially in the manufacturing process of special-shaped components,there are great difficulties in formwork production and construction,and the consumption of manpower,materials and the construction cycle will increase accordingly.