Materiales de Construcción, Vol 51, No 263-264 (2001)

Thaumasite formation in hydraulic mortars by atmospheric SO2 deposition


https://doi.org/10.3989/mc.2001.v51.i263-264.357

M. T. Blanco-Varela
Instituto de Ciencias de la Construcción Eduardo Torroja (CSIC), Spain

J. Aguilera
Instituto de Ciencias de la Construcción Eduardo Torroja (CSIC), Spain

S. Martínez Ramirez
Instituto de Ciencias de la Construcción Eduardo Torroja (CSIC), Spain

A. Palomo
Instituto de Ciencias de la Construcción Eduardo Torroja (CSIC), Spain

C. Sabbioni
Institute ISAO, National Research Council, Italy

C. Riontino
Institute ISAO, National Research Council, Italy

G. Zappia
Institute ISAO, National Research Council, Italy

K. Van Valen
Dept. of Civil Engineering, KU Leuven, Belgium

E. E. Toumbakari
Dept. of Civil Engineering, KU Leuven, Belgium

Abstract


Sulphation of mortars and concretes is a function of diverse environmental factors (SO2 aerosol, temperature, etc) as well as some material characteristics. One of the phases that could be formed as consequence of the sulphation of the hydraulic binder is thaumasite. In this paper different hydraulic mortars have been exposed to laboratory exposure chambers in order to reproduce thaumasite formation due to atmospheric SO2. Under the laboratory exposure conditions, thaumasite was formed in hydraulic lime mortars, and mortars elaborated with ordinary Portland cement as well as mineralized white portland cement. However, thaumasite was not formed in mortars made of lime and pozzolan. The first product formed as a result of the SO2-mortar interaction was gypsum. Gypsum reacted with calcite and C-S-H gel, present in the samples, giving place to thaumasite. Low temperature promotes thaumasite formation.

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