Preparation of metakaolin based geopolymer and its three-dimensional pore structural characterization

Abstract

Three types of pure geopolymer pastes (poly-sialate PS, poly-sialate-siloxo PSS, and polysialate-siloxo PSDS) were fi rst prepared by alkali (NaOH and KOH) activated metakaolin. Then a void space network was employed to simulate the 3-D pore-throat distribution across the unit cell of the various hardened geopolymer pastes with reference to their experimental mercury intrusion curves. Based on the simulated 3-D pore-throat structure models, a wide range of pore-level properties such as porosity, connectivity, permeability and tortuosity of various geopolymer pastes were calculated. The 3-D structural model and calculated parameters showed that most of the pores in Na-PS geopolymer paste was very small size pores ranging from 0 to 100 nm. A few very large pores were spread amongst the small pores, resulting in a very high penetration pressure, permeability resistance. Unlike Na-PS geopolymer paste, pore size with medium size of Na-PSS, K-PS and K-PSS geopolymer pastes distributed uniformly across the unit cell, and the size changes of adjacent pores in the 3 geopolymer pastes were little, producing higher penetration pressure, lower permeability, smaller connectivity and larger tortuosity. In contrast, pores in Na-PSDS and K-PSDS geopolymer pastes were relatively large and distributed concentratively, which caused samples to be easily penetrated by mercury, methane and nitrogen etc under relatively low pressures. Z H A N G Yu n s h e n g ( ) : P r o f . ; P h D ; E -m a i l :

Preparation and Properties of Alkali Activated Metakaolin-Based Geopolymer

“…Figure 2 shows the X-ray diffractograms of raw material metakaolin and geopolymers cured at different temperatures and times. In the XRD pattern of metakaolin, a wide dispersion peak located between 18° and 25° was attributed to the amorphous structure of metakaolin [ 25 ]. In addition to quartz crystals, the microstructure of metakaolin was mainly hypocrystalline and amorphous.…”

The Effect of Polymer Waste Addition on the Compressive Strength and Water Absorption of Geopolymer Ceramics

“…Characteristic kaolin peaks at 2θ values of 12.5 • , 24.9 • , and 27.1 • had high intensities but decreased after calcination and geopolymerization (Figure 7a). Similarly, characteristic high-intensity kaolin peaks at 2θ = 27.1 • were decreased after geopolymerization (Figure 7b), which suggests that the amorphous kaolinitic phase is the main constituent after geopolymerization [50][51][52].…”

Preparation of Low-Cost Magnesium Oxychloride Cement Using Magnesium Residue Byproducts from the Production of Lithium Carbonate from Salt Lakes

“…The mechanical strength of MOC cement is related to the content of crystals and microstructure of the hydration products, porosity and pore distribution [ 52 , 53 ]. As shown in Figure 13 , the cumulative porosity of MOC cement with increasing calcination temperature and Baume.…”