复掺缓凝剂对3D打印混凝土建造性能的影响OA

This study addressed the requirements for compressive strength and setting time in continuous 3D printing concrete construction by employing a composite retarder of sodium gluconate and sodium citrate.By testing rheological properties,compressive strength,and setting time of the composite paste,a type of 3D printing concrete was successfully developed that concurrently met the demands of printability,buildability,compressive strength,and setting time.The results indicate that when the dosage of sodium citrate or sodium gluconate is between 0.02％and 0.10％(mass fraction),or when the composite retarder dosage is 0.10％or 0.12％,the cement hydration is effectively delayed.Compared to the reference group,the initial and final setting times are extended by 32～42 min and 34～50 min,respectively.The variation in total composite retarder dosage shows no significant effect on the setting time,early-age strength,or rheological properties of different mixtures.However,the variation in proportion between sodium citrate and sodium gluconate demonstrates considerable influence on the setting time,early-age strength,and rheological properties of the 3D printing concrete.When the mass ratio of sodium citrate to sodium gluconate ranges from 1∶1 to 2∶1,the overall performance of the 3D printing concrete is optimal.Additionally,the 3D printing concrete prepared with composite retarder is successfully enabled the continuous printing of precast composite floor slab side formwork.