A thermodynamic approach to the hydration of sulphate-resisting Portland cement

Journal Article · Sat Jul 01 04:00:00 EDT 2006 · Waste Management

DOI:https://doi.org/10.1016/j.wasman.2006.01.023· OSTI ID:20877585

Lothenbach, Barbara ^[1]; Wieland, Erich ^[2]

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1. Empa, Swiss Federal Laboratories for Materials Testing and Research, Laboratory for Concrete and Construction Chemistry, Uberlandstrasse 129, 8600 Duebendorf (Switzerland)
2. Paul Scherrer Institute, Nuclear Energy and Safety Department, Laboratory for Waste Management, 5232 Villigen PSI (Switzerland)

A thermodynamic approach is used to model changes in the hydrate assemblage and the composition of the pore solution during the hydration of calcite-free and calcite-containing sulphate-resisting Portland cement CEM I 52.5 N HTS. Modelling is based on thermodynamic data for the hydration products and calculated hydration rates for the individual clinker phases, which are used as time-dependent input parameters. Model predictions compare well with the composition of the hydrate assemblage as observed by TGA and semi-quantitative XRD and with the experimentally determined compositions of the pore solutions. The calculations show that in the presence of small amounts of calcite typically associated with Portland cement, C-S-H, portlandite, ettringite and calcium monocarbonate are the main hydration products. In the absence of calcite in the cement, however, siliceous hydrogarnet instead of calcium monocarbonate is observed to precipitate. The use of a higher water-to-cement ratio for the preparation of a calcite-containing cement paste has a minor effect on the composition of the hydrate assemblage, while it significantly changes the composition of the pore solution. In particular, lower pH value and higher Ca concentrations appear that could potentially influence the solubility and uptake of heavy metals and anions by cementitious materials.

• OSTI ID: 20877585
• Journal Information: Waste Management, Journal Name: Waste Management Journal Issue: 7 Vol. 26; ISSN WAMAE2; ISSN 0956-053X
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ANIONS
CALCITE
CALCIUM
FORECASTING
HEAVY METALS
HIGH-TC SUPERCONDUCTORS
HYDRATES
HYDRATION
PH VALUE
PORTLAND CEMENT
SULFATES
THERMAL GRAVIMETRIC ANALYSIS
TIME DEPENDENCE
UPTAKE
X-RAY DIFFRACTION