*Article* **The Influence of Sintering Temperature on the Pore Structure of an Alkali-Activated Kaolin-Based Geopolymer Ceramic**

**Mohd Izrul Izwan Ramli 1,2 , Mohd Arif Anuar Mohd Salleh 1,2,\*, Mohd Mustafa Al Bakri Abdullah 1,2, Ikmal Hakem Aziz 1,2 , Tan Chi Ying 2, Noor Fifinatasha Shahedan <sup>2</sup> , Winfried Kockelmann 3, Anna Fedrigo <sup>3</sup> , Andrei Victor Sandu 4,5,6,\* , Petrica Vizureanu 4,7,\* , Jitrin Chaiprapa <sup>8</sup> and Dumitru Doru Burduhos Nergis 4,\***


**Abstract:** Geopolymer materials are used as construction materials due to their lower carbon dioxide (CO2) emissions compared with conventional cementitious materials. An example of a geopolymer material is alkali-activated kaolin, which is a viable alternative for producing high-strength ceramics. Producing high-performing kaolin ceramics using the conventional method requires a high processing temperature (over 1200 ◦C). However, properties such as pore size and distribution are affected at high sintering temperatures. Therefore, knowledge regarding the sintering process and related pore structures on alkali-activated kaolin geopolymer ceramic is crucial for optimizing the properties of the aforementioned materials. Pore size was analyzed using neutron tomography, while pore distribution was observed using synchrotron micro-XRF. This study elucidated the pore structure of alkali-activated kaolin at various sintering temperatures. The experiments showed the presence of open pores and closed pores in alkali-activated kaolin geopolymer ceramic samples. The distributions of the main elements within the geopolymer ceramic edifice were found with Si and Al maps, allowing for the identification of the kaolin geopolymer. The results also confirmed that increasing the sintering temperature to 1100 ◦C resulted in the alkali-activated kaolin geopolymer ceramic samples having large pores, with an average size of ~80 μm<sup>3</sup> and a layered porosity distribution.

**Keywords:** geopolymer; pore; tomography imaging; sintering
