Page 49 - MSAM-1-3

Optimization of chemical admixtures for 3DCP

Materials Science in Additive Manufacturing

structure occurred during the printing test since material static
yield stress is insufficient to keep the printed layers to stand
firmly; therefore, it is not suitable for 3D printing. Finally, the
structure collapsed due to large deformation and misalignment.
Therefore, materials with higher yield stress and higher
thixotropy have better printability according to the printing
test. The developed statistical models by using CCD can be an
efficient method to optimize the dosage of chemical admixtures
so that the material has the desired rheological properties, that
is, high yield stress and high thixotropy, for 3DCP.
5. Conclusions

In this study, CCD was adopted to investigate the impact
of chemical admixtures and their combined interactive
effects on the rheological properties with respect of static/
Figure 11. Final printout of formulation No. 3. dynamic yield stress, plastic viscosity, and thixotropy. Two
mixtures with the extremes of the rheological properties
A B were selected for the printing test in this work. The printing
test was successfully conducted when the mixture has high
yield stress (1,156 Pa) and high thixotropy (17,081 Pa/s).
However, the collapse happened during the printing test
when materials have a low yields stress (588.6 Pa) and low
thixotropy (7,410 Pa/s).
Four polynomial models are constructed to correlate
the dosage of chemical admixtures with material
C rheological properties. The derived models are shown
to be statistically significant based on ANOVA analysis.
The results indicate that with an increase in the dosage
of superplasticizer or retarder, the rheological properties
decrease, while accelerator possesses an opposite effect on
the rheological properties. The combined interactive effect
of retarder and accelerator has a negative impact on the
rheological properties. The interactive effect of retarder
Figure 12. Printability test result of formulation No. 6: (A) Slight and superplasticizer possesses a positive impact on the
deformation appeared; (B) large deformation and misalignment occurred; dynamic yield stress, plastic viscosity, and thixotropy
and (C) final collapse occurred. while it has a negative influence on the static yield stress.
The interactive effect of accelerator and retarder has a
4.3. Printability test results positive influence on the yield stress whereas it possesses
The mixture proportions of No.3 and No.6 in Table 4 were a negative impact on the plastic viscosity and thixotropy.
selected in printability test as they show the extremes The CCD derived model is not universally applicable
of the rheological properties. The mixture proportion since the results may possibly alter in conjunction with
of No.3 possesses high yield stress (1,156 Pa) and high other factors such as the test range of parameters being
studied. However, the CCD can minimize the efforts
thixotropy (17,081 Pa/s). On the contrary, No.6 possesses and time consumed in conducting experiments while
a low yields stress (588.6 Pa) and low thixotropy (7,410 obtaining sufficient information for data analysis. The
Pa/s). Final printed component with mixture proportion method is particularly useful when one has to deal with
No.3 is illustrated in Figure 11. As shown from Figure 11, a large number of variables in experiment. The second-
it indicates that the mixture proportion of No.3 can be order models can be further obtained through the CCD
printed well, and material can fully maintain its shape in to make predictions.
the printing process.
However, mixture proportion of No.6 is not suitable for Acknowledgments
printing as shown in Figure 12. Large deformation of the None.

Volume 1 Issue 3 (2022) 10 https://doi.org/10.18063/msam.v1i3.16