Dark discoloration of fair-Face concrete surfaces-transport and crystallization in hardening concrete

Abstract

Especially during outdoor concrete production in winter, mottled dark discoloration frequently spoils the appearance of fair-face concrete surfaces. At the Centre for Building Materials (cbm) of the Technical University of Munich, the dark discoloration that occurs in practice is characterized in terms of surface structure, near-surface microstructure and chemical composition. By varying the conditions of concrete production and storage, it was possible to simulate the discoloration in the laboratory and thus determine the main factors responsible for the mottled appearance. By comparing the results of field and laboratory investigations, the transport and crystallization processes in hardening concrete that lead to the discoloration of fair-face concrete surfaces were determined. Copyright © 2008 Japan Concrete Institute.