Pore‐forming process in dehydration of metakaolin‐based geopolymer

Abstract

The geopolymer catalyst supports utilized in the nuclear waste containers for the Fukushima Daiichi Nuclear Power Station, will be required to have high porosity, and durability. This work presents the synthesis of a potassium and metakaolin based geopolymer and its performance upon dehydration. During water content measurements of the samples, it was seen that in the demolded samples, the water content quickly decreased to less than 30% within 7 days, while the samples, that had the cap removed from the container retained more than 50% of the water Accepted ArticleThis article is protected by copyright. All rights reserved after 28 days. The pore size distribution of the samples that were post-cured at different temperatures up to 28 days did not vary greatly with respect to the average pore size. We can infer that structurally stable pores were formed in the first 4 days and were not affected by the post-curing rate, which may be related to rheological properties and the drainage path of water or hydrogen gas during post-curing.

Early-Stage Geopolymerization Process of Metakaolin-Based Geopolymer

“…However, rapid generation of initial gels can make products cover the surface of remnant precursor particles. Moreover, the samples with a lower water/binder ratio have less water, which will weaken the free movement of ions and retard the bond linkage [ 47 ]. Therefore, the duration from the strength of the initial setting to the strength of the final setting is prolonged, and the reduction of the final setting time is not as much as the initial setting time.…”

Effect of dehydration time and air tightness on pore distribution of potassium and metakaolin-based geopolymer

“…29) The porosity and pore distribution of geopolymers play an important role in the application of catalyst supports. Previous research 21) showed that macropores may be formed in the first 4 d. In the present work, potassium and metakaolin-based geopolymer samples were synthesized. The workflow was carried out by evaluating the mechanical strength value and pore size distribution of the geopolymer, which are based on two factors, the varying early-age curing time and air tightness after early-age curing.…”

“…5,[17][18][19][20] Consequently, geopolymers have been developed as candidate materials for hydrogen recombination catalyst support in previous research. 2,21) The mechanical strength of geopolymers is strongly affected by the content of K 2 O and the water coefficient of H 2 O/metakaolin, while the compressive strength value of the sample is not significantly different from the SiO 2 to K 2 O molar ratio variable. 22) When a sample is cured at a high temperature, compared to one cured at room temperature, the higher curing temperature will increase the early compressive and flexural strength, and even reach the target value within 1 d. In addition, the effect of temperature depends on the curing time.…”