| Different from the traditional construction technology,3D printing concrete technology is a new construction technology.It has great advantages in modeling design,efficient construction and green intelligence.It is one of the hotspots of building construction technology research at present.However,under the constraints of current materials,equipment and construction technology,3D printing concrete technology is more suitable for printing some lightweight buildings,municipal public facilities and landscape sketches with special and complex structures.In view of the main problems existing in the preparation and application of 3D printing concrete,combined with the characteristics and advantages of 3D printing concrete technology,this paper studies the preparation and application of high-performance 3D printing concrete from two aspects:preparation and physical printing.The research contents are as follows:Ordinary Portland cement-based high-performance 3D printing concrete with good printability and mechanical properties was prepared by using bulk raw materials such as machine-made sand,ordinary portland cement and mineral admixtures together with admixtures such as water reducing agent and accelerator.White or colorless materials such as white cement,limestone powder,quartz sand,polycarboxylic acid water reducer and accelerator were used to prepare white 3D printing concrete.On this basis,color 3D printing concrete with good performance was prepared by adding pigment.Lightweight 3D printed concrete was prepared with P·O42.5R cement,micro silica powder,limestone powder,hollow glass beads,basalt fiber,water reducer and alkali free accelerator.And the volume weight of the lightweight 3D printed concrete is 1097kg/m~3,the setting time is36min,the flexural strength at 1d and 28d is 3.4MPa and 9.0MPa respectively,and the compressive strength at 1d and 28d is 19.6MPa and 48.3MPa respectively.The red 3D printing concrete prepared with 3%DPP red pigment and the ordinary Portland cement-based 3D printing concrete without fiber were used to print the Jiangong company logo,corrugated flower bed and polygonal flower pot from easy to difficult respectively.The structures of the three models are relatively simple and the overall printing effect is good.The special-shaped columns with complex structure are printed with ordinary Portland cement-based 3D printing concrete.While the surface forms a braided texture,the section changes with the printing height,and has obvious inclination angle.The designed printing width is 25mm,the floor height is 10mm,and the printing speed is 2.8m/min.Its actual printing width is 25～27mm,the floor height is uniform,the total height is 1000mm,it takes 71min to print,the printing texture is neat and beautiful,the design features are completely presented,and the printing quality is good.By reasonably cutting and optimizing the printing path,the lightweight 3D printing concrete with dry unit weight of 1100kg/m~3is used to realize the printing of lightweight hollow seats with more curved surfaces,hollows and local suspension without formwork and support.The printed lightweight hollow out chair presents a good design shape,and the overall printing effect is good.Participated in the design and construction of the frame 3D printer,and the effective printing range is 10m long,5m wide and 4m high.The model house with an area of 24 square meters and a height of 3.72 meters was printed in situ.The wall printing took 20h,which took about 30 hours in three days.The overall printing effect was good.By laying fiber mesh cloth in the horizontal direction and embedding reinforcement cage in the vertical direction,the integrity of the house is enhanced and the structural safety of the house is improved. |
