Identifizierung der Zementart in hydratisierten Betonen und Mörteln / Identification of the Type of Cement in Hardened Concretes and Mortars

Subject of this paper is the development of a method for the identification of the type of cement present in a hardened concrete or mortar. The method is based on the dehydration of the cement paste and the identification of the phases present after the dehydration. Considering clinker phases and real cements, the following possibilities for the identification of cements were worked out:

• differentiation between Portland cements and cements containing additions by the identification of the mineral phases which are typical for the type of the addition

• differentiation between ordinary and sulphate resistant Portland cements by the identification of the Ye'elimite phase after a dehydration at a temperature of 1100° C

• determination of the characteristic compressive strength of Portland cements by the evaluation of the Alite-content.

For an identification at least two dehydration temperatures have to be considered. The first temperature range is at about 1100 to 1200°C. It is important for the identification of the aluminates and ferrites. Temperatures from about 1400 to 1450°C are needed for the dehydration of the silicates. Because of the appearence of melting phases at temperatures above 1200°C, the Alite-content will be determined indirectly by the determination of the Belite-content and the content of free lime after a dehydration at 1100°C. At this temperature the free lime is considered to represent the difference in calcium oxide between the Alite and the Belite.