Synchronous vacuum hot pressing ultra-high performance geopolymers: Deformation behavior across temperatures

Junchao Yang, Peng Du, Yiming Zhou, Jinbang Wang, Xin Cheng

Research output: Contribution to journalArticlepeer-review

Abstract

In order to develop ultra-high performance geopolymer products with "high strength, high density, high stability and low cost", breakthroughs in geopolymer technology are crucial for their application in high-end commercial and even military sectors. This study investigates the self-deformation mechanism at ambient temperature and the deformation behavior from low temperature to high temperature of synchronous vacuum hot pressing metakaolin fly ash-based geopolymers. In contrast to previous studies, the self-deformation of Synchro-vacuum hot pressing metakaolin fly ash based geopolymer at room temperature undergoes four distinct stages: the expansion period of the first and third stages and the shrinkage period of the second and fourth stages. The modification results in a synergistic effect between the first and second stages, effectively suppressing the volumetric deformation of geopolymers. The expansion deformation is primarily caused by an increase in internal stress within the matrix and further gelation reaction during the later stage, while shrinkage deformation arises from changes in the gel structure. Additionally, volume deformation from low to high temperatures can be divided into four stages, with 200 °C and 800 °C identified as key temperatures for such deformations. The rapid shrinkage observed at these temperatures is attributed to the swift loss of free water at 200 °C and transformation of the internal matrix structure at 800 °C. Notably, two ultra-high strength peaks of 142 MPa and 147 MPa are achieved at 200 °C and 500 °C respectively due to rapid gelation reactions prior to reaching 200 °C and continued reactions involving inert particles along with transformation of crystal hydration products into a more stable form. The structure of the aluminosilicate three-dimensional network remains relatively stable across all samples until feldspar formation occurs above 800 °C. The synchronous vacuum hot pressing metakaolin fly ash-based geopolymers synthesized in this study represents a novel category of ultra-high performance ceramic-like geopolymers, exhibiting exceptional strength and stability at both low and high temperature.

Original languageEnglish
Article number139568
Number of pages13
JournalConstruction and Building Materials
Volume458
DOIs
Publication statusPublished - 10 Jan 2025

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