Study on printability of 3D printing carbon fiber reinforced eco-friendly concrete: Characterized by fluidity and consistency

Abstract

Carbon fibers have often been added to concrete as reinforcement. Eco-friendly concrete with industrial by-products has been widely studied and applied as green building materials. Studying the workability and printability of eco-friendly concrete with carbon fibers is worthwhile. The workability and printability of eco-friendly concrete are dominating factors that ensure that printing can be carried out smoothly. This study uses a combination of experiments and numerical simulations to study the printing performance of carbon fiber-reinforced eco-friendly concrete (CFREFC). The workability and printability of 9 mixes of 3D printing CFREFC under various combinations of different water-binder (w/b) ratio levels and superplasticizer (SP) dosages were tested. Two methods, namely the consistency and fluidity tests, were used to characterize the printability. After consistency and mortar fluidity tests, the 9 mixtures were printed to get the printing performance. Finally, the relationship between the workability and printability of 3D printing CFREFC was established. The condition numbered M7 (w/b = 0.4, SP = 0.5) in the selected experimental group was used as the source of its simulation parameter. The result shows that it is feasible to characterize printability using workability, i.e., consistency and fluidity, which increase with the increase of w/b and SP dosage. Under the printing parameters of the HC1008 printer were determined, i.e., 20 mm of nozzle size, 50 mm/s of printing speed, 30 rpm of material extrusion speed, and 14 mm layer height, the fresh CFREFC was not suitable for 3DP application when its consistency is less than 48.99 mm and more than 81.96 mm, or when its fluidity is less than 166.72 mm and more than 200.93 mm. When the consistency is from 56.34 to 65.61 mm, and the fluidity is from 172.18 to 183.30 mm, the printability of CFREFC is the best under the same printing parameters. The simulation results indicated that with the increased number of printing layers, the bottom of the printed model would be deformed by the gradual increase in pressure, and a specific height loss would occur, which was consistent with the experimental results.