Mixing approach for 3D printable concrete: method of addition and optimization of superplasticizer dosage

This study systematically investigates the superplasticizer (SP) addition methods and optimum SP dosage with various water binder (w/b) ratios for mixing 3D printable concrete (3DPC). In the present study, five distinct strategies were adopted to arrive at the optimum Method of Addition (MoA). The first strategy applied the random mixing approach to identify the methods for adding SP with varying time patterns through visual observation. Secondly, a constant time pattern was adopted from the random approach for mixing and the optimal SP dosage was determined. The third strategy examined different addition methods with the optimum SP dosage. In the fourth strategy, the batching effect of the material with the optimum SP dosage was assessed, and finally, the printable region with different w/b ratios and SP dosages were correlated. The observations illustrated that the optimum SP dosage in the range of 0.10 to 0.21% of binder with a w/b ratio of 0.21 to 0.25 achieved adequate printability parameters by full addition of SP following a constant wet mixing time as the optimal application. However, after applying the optimum SP dosage, a supplemental SP dosage is required at appropriate intervals to retain the workability for higher batches.