On the aggressive nature of non-aggressive water – deterioration of cement-based materials in permanent contact with drinking water
Schwotzer, M. / Gerdes, A. (2018)
H2OSummit, 1st International Water Congress 2018, Rovinj, Croatia, 18.-21.04.2018
- Date: April 2018
The long-term performance of the drinking water supply infrastructure is of utmost importance for further social development. Therefore, in all epochs of European history drinking water reservoirs were coated with mineral mortar linings. Although drinking water is commonly not considered to be particularly harmful to cement-based systems, modern coatings systems often show insufficient durability in this particular operational environment. Especially in regions with hard drinking water, there are frequent damages appearing on the cement-based mortar linings, for which the causes are still the subject of intensive scientific discussions. Such degradation reactions of mortar linings in drinking water storage tanks, which are referred to as hydrolytic corrosion, can cause considerable damage after a service life of only a few months. This results in cost intensive repair measures and thus high life-cycle costs as well associated with an ecological burden. Furthermore, an insufficient understanding of degradation mechanisms and their underlying physical, chemical as well as biological processes currently impedes performance-oriented approaches to improve durability. In this regard, a research project was carried out unravel the potentially combined multiple deterioration mechanisms integrating results of case studies and laboratory experiments. In particular the potential impact of the conditions during the construction phase of drinking water reservoirs and their operational phase were addressed. This study shows, that the transport properties of the rim zone of cement-based materials, which are developing in a material directly after the application, are regulating its sturdiness in aggressive aqueous environments. Moreover, during use, durability may be affected by various firstly unapparent factors. E.g. electrical fields are suspected to have a significant impact on reactive transport processes promoting the degradation of the materials. This results in new approaches for the prevention of damages in practice contributing to more target-oriented quality control concepts and performance-oriented development of materials with increased durability.