Doctoral Dissertations

Keywords and Phrases

Borosilicate glass; Corrosion; Enamel coating; Phosphates; Reinforcing steel

Abstract

"Phosphate-doped sodium borosilicate glasses were developed for enamel coatings to provide corrosion protection for reinforcing steel in concrete. Phosphates have low solubilities in borosilicate glasses, generally less than about 4 mol%, and are incorporated mainly as isolated PO43- and P2O74- anions, along with some borophosphate bonds. With the addition of P2O5, the silicate network is repolymerized and tetrahedral borates are converted to trigonal borates, because the phosphate anions scavenge sodium ions from the borosilicate network. The addition of Al2O3 significantly increases the solubility of P2O5 due to the formation of aluminophosphate species that increases the connectivity of phosphate sites to the borosilicate glass network. The addition of P2O5 has an insignificant effect on thermal properties like Tg, Ts and CTE, and chemical durability in alkaline environments can be improved, particularly for glasses co-doped with alumina. When the solubility limit is reached, a phase-separated microstructure forms, degrading the chemical durability of the glass because of the dissolution of a less durable alkali borate phase. The dissolution rates of glasses in a simulated cement pore water solution are orders of magnitude slower than in Ca-free solutions with similar pH. In Ca-saturated solutions, a passivating layer of calcium silicate hydrate (C-S-H) forms on the glass surface. Phosphate-rich glasses react with the simulated cement pore water to form crystalline hydroxyapatite (HAp) on the glass surface. Electrochemical tests reveal that the HAp precipitates that form on the surfaces of intentionally-damaged phosphate-doped enamel coatings on reinforcing steel suppress corrosion. The enhanced corrosion protection is retained in chloride-containing pore water, where the development of hydroxyl-chlorapatites immobilizes the free chloride ions in solution"--Abstract, page iv.

Advisor(s)

Brow, Richard K.

Committee Member(s)

Chen, Genda
Day, D. E.
OKeefe, Matt
Schlesinger, Mark E.

Department(s)

Materials Science and Engineering

Degree Name

Ph. D. in Materials Science and Engineering

Sponsor(s)

National Science Foundation (U.S.)

Publisher

Missouri University of Science and Technology

Publication Date

Fall 2014

Journal article titles appearing in thesis/dissertation

  • Effect of P2O5 in sodium borosilicate and aluminoborosilicate glasses on structure: multi-nuclear (31P, 27Al, 11B, 29Si) MAS NMR and Raman study
  • Effect of P2O5 in sodium borosilicate and aluminosilicate glasses on properties: phosphate solubility, phase separation, thermal properties and chemical durability
  • The dissolution behavior of phosphate-doped borosilicate glasses in simulated cement pore solutions
  • Self-healing property of phosphate-doped enamel coatings on reinforcing steel in simulated cement pore fluid and its deterioration under chloride

Pagination

xix, 171 pages

Note about bibliography

Includes bibliographical references (pages 166-170).

Rights

© 2014 Xiaoming Cheng, All rights reserved.

Document Type

Dissertation - Open Access

File Type

text

Language

English

Subject Headings

Steel, Structural -- Corrosion -- PreventionReinforced concrete constructionEnamel and enamelingCoatings

Thesis Number

T 10605

Electronic OCLC #

902730677

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