Thesis Defense – Yiğit Alper Atalay (MSCE)

Yiğit Alper Atalay – M.Sc. Civil Engineering

Asst. Prof. Dr. Zeynep Başaran Bundur – Advisor

Date: 09.08.2022

Time: 11.00

Location: AB1 231

“Implementation of Microwave Curing System to Adapt

Metakaolin Based Geopolymer Binders for 3D-Printing”

Asst. Prof. Dr. Zeynep Başaran Bundur, Özyeğin University

Prof. Dr. Mehmet Ali Gülgün, Sabancı University

Asst. Prof. Dr. İlknur Eruçar, Özyeğin University

Abstract:

Three-dimensional (3D) printing techniques for the construction materials such as contour crafting and additive manufacturing are being developed in the construction sector and replacing the conventional building techniques used for generations. To achieve successful printing on large scale, it is necessary to develop advanced printing systems and compatible software. Another main challenge in 3D printing is to design a suitable material feasible with the requirements of the 3D printing in terms of its extrudability and buildability. It is also known that extrudability and buildability are also contradicting factors, as high workability causes more extrudability while low workability provides more buildability. Therefore, the designed material should exhibit a high level of workability as it is required to be extruded through the printer nozzle and sustain its shape without major deformation while subsequent layers are printed on top of each other. To obtain such structural reliability and applicability, fresh and hardened properties of the material such as tensile and compressive strength, static and dynamic yield stress obtained by rheological experiments, thixotropic behavior, flowability, etc. should be evaluated.

The goal of this study was to adapt metakaolin-based geopolymer mortar to 3D printing through a novel microwave curing approach. To achieve this goal, 3 types of precursor materials and 2 types of different curing regimes which are microwave and oven curing were utilized to enhance the materials’ characteristic properties by triggering the rapid strengthening and buildability. The experimental design was established for samples with 3 different molar ratios (MR; 1.3,1.5 and 1.7) containing metakaolin, fly ash and silica fume. Samples were subjected to 3 different curing regimes: oven curing, microwave curing and hybrid curing (combination of optimized microwave and oven curing).

Results showed that replacing a portion of applied oven curing with microwave curing in a hybrid approach can increase operation speed and increase the rate of hardening. While the use of microwave curing in the geopolymer binders did not affect the alkali leaching, it increased the drying shrinkage in the material. Moreover, it was found that the samples can be hardened in 120 minutes once they are subjected to microwave curing while it was 60 minutes for hybrid curing. The use of microwave curing increased the green strength and dimensional stability without sacrificing from workability of the sample. Implementation of microwave curing improved the printability of metakaolin based geopolymers by affecting the buildability of the material. The outcomes of this study will pave a better design of set-on-demand geopolymer binders for advanced applications such as 3D printing by reducing the total duration of heat curing.

Bio:

Yiğit Alper Atalay graduated from Hacı Sabancı Anatolian High School in June 2013. The following September, he entered Özyeğin University and in June 2018 received the degree of Bachelor of Science in Civil Engineering. He entered Özyeğin University in September 2019 and received a Master of Science Degree in Civil Engineering under the supervision of Asst. Prof. Zeynep Başaran Bundur in August 2022.

He authored publications in journals including “RILEM International Conference on Concrete and Digital Fabrication” and “Journal of the Building Engineering”. His fields of study are 3D printing of cementitious and geopolymer-based materials, material recycling, concrete, and geopolymer rheology.

Publications:

1. “Design of Energy-Efficient White Portland Cement Mortars for Digital Fabrication” Second RILEM International Conference on Concrete and Digital Fabrication, vol. 28, 2020.
2. “Effect of microwave curing on performance of metakaolin-based geopolymer mortars” Journal of Building Engineering, 2022