Compatibility of Hydrogarnet, Ca₃Al₂(SiO₄)ₓ(OH)₄₍₃₋ₓ₎, with Sulfate and Carbonate-Bearing Cement Phases: 5-85 °C

Abstract

The stable existence of hydrogarnet in Portland cement compositions cured at temperatures below 55 °C has long been predicted from application of equilibrium thermodynamics. However hydrogarnet is not often reported in hydrated commercial Portland cements. The substitutions (SO4-CO3-OH) in AFm have previously been shown to stabilise AFm to higher temperatures and raise the temperature at which AFm converts to Si-free hydrogarnet, C3AH6. But unanswered question remains about the compatibility of AFm and AFm solid solutions with Si-substituted hydrogarnet, Ca3Al2(SiO4)x(OH)4(3 - X). Phase relations of C3AH6 and Ca3Al2 (SiO4)x(OH)4(3 - X) at sulfate and carbonate activities conditioned respectively by (gypsum and SO4-AFt) and (calcite and CO3-AFt) have been determined experimentally in the range 5-85 °C. The results confirm the instability of Si-free hydrogarnet with carbonate and sulfate-bearing cement phases, but do indicate that a range of silica-substituted hydrogarnet solid solutions are stable under conditions likely to be encountered in blended cement systems.

Department(s)

Chemical and Biochemical Engineering

Keywords and Phrases

Carbonate (D); Hydrogarnet (D); Kinetics (A); Stability(C); Sulfate (D)

International Standard Serial Number (ISSN)

0008-8846

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2016 Elsevier Ltd, All rights reserved.

Publication Date

01 May 2016

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