Prüfung der Best?ndigkeit von M?rtelprodukten gegenüber saurem Angriff bis pH3 und Einstufung in Expositionsklassen

摘要

Structures and channels, particularly those used in wastewater systems, can be exposed to acid attack that can have various causes and different acid concentrations. If the structures are made of masonry or concrete then mineral mortars, which are expected to resist these acid attacks to a certain extent, are used in their construction, protection and repair. The article describes a test method for purely dissolving acid attack by mineral acids like hydrochloric acid and nitric acid and also, in particular, for attack by sulfuric acid that leads to the formation of new solid phases in the corrosion layers, as well as by organic acids like lactic acid. The suitability of the test method was checked and demonstrated with the aid of numerous investigations on different mortar products. The method proved to be more economical and more accurate than visual evaluation of cross-sections. Permissible corrosion depths are recommended on the basis of the guidelines in DIN 1045 and DIN EN 206 and the results of the tests on a reference mortar. These recommended corrosion depths serve as limit values for classifying other mortar products with respect to their corrosion resistance to acid attack, especially by sulfuric acid. The classification or evaluation provides information about whether the mortar products that have been tested are suitable use in the exposure classes XA3, XA2 or XA1. For use outside the scope of approval of the above-mentioned standards a pH limit can be determined and defined up to which the mortar product can be used without any additional protective measures. A procedure is also recommended for estimating the depths of corrosion during exposure times of up to ten years on the basis of 4000 hours of test results.%Insbesondere in der Abwassertechnik k?nnen Bauwerke und Kan?le einem sauren Angriff ausgesetzt sein, der verschiedene Ursachen haben und unterschiedliche S?urekonzentrationen aufweisen kann. Sofern die Bauwerke aus Mauerwerk oder Beton bestehen, werden zur Herstellung, zum Schutz und zur Reparatur mineralische M?rtel eingesetzt, die den genannten sauren Beanspruchungen in einem bestimmten Umfang widerstehen sollen. In dem Beitrag wird ein Prüfverfahren beschrieben, dessen Eignung getestet bzw. nachgewiesen wurde anhand zahlreicher Untersuchungen an verschiedenen M?rtelprodukten für rein l?sende saure Angriffe durch Minerals?uren wie Salzs?ure und Salpeters?ure, insbesondere aber auch für den Angriff durch Schwefels?ure, die zur Neubildung fester Phasen in den Korrosionsschichten führt, ferner durch organische S?uren wie Milchs?ure.