| As a construction technology developing rapidly in recent years,architectural 3D printing has attracted wide attention from all sides.Compared with traditional construction methods,3D printing of buildings does not require the use of templates during construction,which is easy to construct and saves manpower and material resources.At the same time,the construction site has low noise and pollution,and has the advantages of green and environmental protection.However,the selection of building 3D printing materials is more stringent than traditional construction,and the development of 3D printing materials is a key factor for the maturity of3 D printing technology.However,at present,there is no clear and authoritative standard for the characterization of the printability of cement-based materials.In order to discuss the printing performance and characterization of cement-based materials for 3D printing of architecture,the following studies are mainly carried out:(1)Cement-based composites mixed with PVA,PP and POM were taken as the research object,and 50%,66% and 75% fly ash were used to replace cement in equal quantities for fluidity,consistency,setting time,compressive strength,flexural strength and ultimate elongation tests.The results show that the fluidity and consistency of cement-based materials mixed with PP fiber are the best under different fly ash content.The cement-based material mixed with POM fiber has the shortest setting time and the largest compressive strength.The ultimate elongation and flexural strength of cement-based materials mixed with PVA fiber are the largest.(2)Through the orthogonal experiment design,the use of extreme difference analysis method to study the water-binder ratio,sand cement ratio,sulfur,aluminate cement,fly ash,dosage of fiber,dosage of water reducing agent and dosage of cellulose ether of doped with limestone powder fluidity of PP fiber reinforced cement matrix composites,consistency,setting time,compressive strength,the influence degree of the ultimate tensile strength and the influence law.The results show that the water-binder ratio has the greatest influence on fluidity,consistency,setting time and compressive strength,and the fiber content has the greatest influence on tensile strength.Combined with the printability requirements of building 3D printing and the analysis of experimental results,it is concluded that the most significant factor affecting the printability of building 3D printing is the water-binder ratio.(3)A device was designed and studied to test the extrudability of 3D printing of buildings.Variable speed extrudability tests were carried out on all orthogonal test groups,and the extrusion speed was set as 200mm/min and 400mm/min respectively.After data processing,the extrusion force-displacement curve(F-L curve)was drawn.The results show that the extrusion force of the same experimental group at the speed of 400mm/min is obviously greater than200mm/min,but the overall situation of the curve changes similarly.At the same time,the slope of 400mm/min extrusion velocity curve increases more than 200mm/min at the later stage.Then,according to the extrusion test results,the image was divided into three main regions,and the building 3D printer was started to verify the printability.The results showed that the image region,fluidity and consistency with the printability of building 3D printing were obtained.Finally,the extrudability test,3D printing test,fluidity and consistency test were carried out again by changing the dosage of limestone powder.According to the test results and the lateral characterization of the printability of fluidity and consistency,the 3D printing material with good working performance can be configured with 10%～15% limestone powder in equal quantity instead of ordinary Portland cement. |
PDF Full Text Request