Title:
Characteristics of Microhydrates Formed under Steam
Conditions
Author(s):
Wei-Ming Lin, C. L. Hwang, and Y. N. Peng
Publication:
Materials Journal
Volume:
97
Issue:
3
Appears on pages(s):
309-324
Keywords:
cement; dry-mixture; fineness; hydrate; scanning electron
microscope (SEM); x-ray diffraction (XRD).
DOI:
10.14359/9876
Date:
5/1/2000
Abstract:
This paper presents the physical properties and chemical composition of hydrates formed under steam conditions. The test specimens were made with cement as well as individual compounds. A comprehensive study on the characteristics of hardened hydrates in a microscopic scale was carried out. An improved polymerization of silicate anions resulting in an increased CaO/SiO, ratio at an elevated temperature was verified by the nuclear magnetic resonance spectroscopy (NMR) analysis. Dense microstructures of hydrates and low content of Ca(OH), crystals were observed by the scanning electron microscope (SEM), energy dispersive spectromer (EDS), environmental scanning electron microscope (ESEM), thermogravimetric analyzer (TGA), and x-ray diffractrometer (XRD) tests. Mercury intrusion porosimetry (MIP) had been used to examine the pore structures of hydrates. It revealed that the hardened paste made with the dry-mixture/steam injection (DMSI) method developed microstructures with low porosity, small pore radius, and larger surface areas. These observations agree with the NMR/TGA test results. This paper also discusses the effects of sample fineness and compaction on the hydrate’s microstructures formed under steam environment. The test results verify the validity of the DMSI concept.