Combined effect of NaAlO2 and NaOH on the early age hydration of Portland cement with a high concentration of borate solution

Journal Article · Tue Jun 15 04:00:00 EDT 2021 · Cement and Concrete Research

DOI:https://doi.org/10.1016/J.CEMCONRES.2021.106430· OSTI ID:23206294

Li, Qiu ^[1]; Ma, Haosen; Tang, Yanjie ^[1]; Chen, Wei ^[1]

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1. State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, 430070 Wuhan, Hubei (China)

The early age hydration of ordinary Portland cement in 5 M borate solution, with or without the addition of NaAlO{sub 2} and/or NaOH, was investigated. Hydration was measured using calorimetry, X-ray diffraction, thermogravimetric analysis, {sup 11}B and {sup 27}Al magic angle spinning NMR analysis, and scanning transmission electron microscopy. The purpose of this study was to reveal the mechanisms behind the retardation caused by a high concentration borate solution and the restoration of hydration through the combined addition of NaOH and NaAlO{sub 2}. Amorphous ulexite, which formed on the surface of the cement particles and prevented the further dissolution of anhydrous phases, was identified as the retardation product. The mechanism of the combined addition of NaAlO{sub 2} and NaOH in overcoming retardation was to transform amorphous ulexite into B-AFt and gowerite (CaB{sub 6}O{sub 10}·5H{sub 2}O). Formation of gowerite is favorable because of the much higher boron immobilization capacity in weight percentage, comparing to usual boron-containing phases reported previously.

• OSTI ID: 23206294
• Journal Information: Cement and Concrete Research, Journal Name: Cement and Concrete Research Vol. 144; ISSN 0008-8846; ISSN CCNRAI
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM 27
BORATES
CALORIMETRY
COMPARATIVE EVALUATIONS
DISSOLUTION
NUCLEAR MAGNETIC RESONANCE
PORTLAND CEMENT
SODIUM HYDROXIDES
SURFACES
THERMAL GRAVIMETRIC ANALYSIS
TRANSMISSION ELECTRON MICROSCOPY
X-RAY DIFFRACTION