Virginia Tech Analyzes Fresh Mixing Properties of 3D Printed Cement Materials

China3D printingMorgan Christen Jenkins recently submitted a master’s thesis to Virginia Tech University, “Fresh Mixed Properties and Digital Image Correlation of Additively Manufactured Cementitious Materials.” Deflection Analysis”, focusing on3D printingmaterials, and how this incredibly innovative technology fits into modern civil infrastructure applications. With the need for better quality assurance and quality control, Jenkins wanted to address standardized testing and evaluation issues and explore typical challenges encountered when working with cement materials today.

Jenkins shows how civil engineering3D printingA nifty picture of many projects revolving around “demonstrability” rather than real reality, a lack of insight into what future outcomes might involve in design, durability, and capacity. With improved testing methods, not only will safety in designs and long-term use be better assured, but users will also have greater potential to enjoy the benefits and success of additive manufacturing.


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3D printingconcrete walls and columns (from Buswell et al.[5]original source in photo description)

3D printingThe use of cement in the construction industry (especially for sustainable housing and other projects featuring components such as concrete slabs, integration with robotics, etc.) is well documented because of the huge advantages of this technology . Such as:

.speed up builds and increase efficiency

.improve accuracy

.Reduce material waste

.Template cost is lower

.reduces the need for manual labor (thus, reduces the risk of workplace injuries)

Meanwhile, challenges include:

.
“Comparison Requirements” for Fresh Mix Performance

.lack of true quality control standards

.Possibility of inferior materials and parts due to decreased strength of material properties

An ever-increasing timeline of projects related to additive manufacturing of cementitious materials since 1997. [5]

with the cement3D printingDuring the continued popularity of the past decade (especially the last few years), a number of methods have been used:

“For example, material extrusion and binder jetting (also known as particle bed fusion) are two AM processes for 3DCP,” Jenkins said. “The difference in which process is used can change which parameters need to be considered during QA/QC. However, the material extrusion process has been the most commonly used AM method for 3DCP.”
Jenkins continues to be concerned about the lack of consistency in the AM process, especially in hardware and software, hybrid design, document design, and the use of concrete in testing.



Iterative process to refine hybrid designs to meet desired AM properties. (Adapted from Zhang et al.[24](Adapted from Kazemian et al.[3]))

“Documenting past, present and future research processes, materials, testing methods, etc., can address the continued development of AM through the use of cementitious materials,” Jenkins noted.
The samples for this study were created using the Sky Large Area Additive Manufacturing (SkyBAAM) system. Phase 1 testing was conducted at the University of Tennessee (UTK) facility, and Phase 2 testing was conducted at the Virginia Tech (VT) facility.

One of the Skybaam workstations controlling the xy plane (left) and the z-axis cables for overhead crane control (right)

Nozzle Extrusion Diagram

Oak Ridge National Laboratory also created a hybrid design for all samples and tests in this study to accompany the SkyBAAM process.
In the first phase, eight samples were tested, all of which failed “rapidly within one to two minutes of loading”. The researchers attribute this to the higher loading rate, which will need to be changed in the future.
“Based on preliminary results from the first stage, sample preparation was carried out; however, the loading rate was extremely high and was not adjusted for the width and height of each beam. Also, finding the modulus of rupture alone did not provide much information on how the loading would information that is distributed or transferred between layers,” Jenkins explained.



visually acceptable print

“Orientation B initially appeared to outperform Orientation A, but the means were not statistically different due to high standard 43 deviations. Further research is needed due to high loading rates and inconclusive results. In particular, further research is needed, including how defects affect performance in every direction.”

Mixing ratio for standard batch of 0.75 ft3 mortar

In the second stage, three methods were used for evaluation: flowability, setting time and early compressive strength-indicating that in3D printingThe effect of using various mortars in Jenkins noted that “there was less variation in properties when measuring and accounting for the moisture profile of the aggregates.” The natural sand setting also showed a 67% reduction between groups 1 and 2. Artificial sand was reduced by 71%. Jenkins recommends that the mixture used to make the composite should take moisture into account for maximum optimization.

[来源/图片：“添加材料制造的胶凝材料的新鲜混合特性和具有数字图像相关性的弯曲分析”]

Jenkins concludes: “For this study, using a minimum unit weight of 132 pcf allowed qualitative differentiation of specimens with significant defects that were closely related to observations and pre-test considerations. For example, in samples with a unit weight of less than 132 pcf There was an 86% increase in the direction of the modulus of rupture B and a 68% reduction in standard deviation between the group and the group with a basis weight greater than 132 pcf. Further indicating the need to implement QA/QC measures; however, at 90, 132 pcf It may not be the same cutoff point for other mortars, and based on extrusion technology, it may vary for each different 3DCP system.for3D printingThe realization of concrete structures, due to the anisotropy of composite materials, strongly suggests that the design is a function of load orientation. “

(responsible editor: admin)