The performance of cement-based coatings for drinking water reservoirs: a case study

SUPSI, University of Applied Sciences of Southern Switzerland, DACD, V. Flora Ruchat 15, 6850 Mendrisio, Switzerland

^* Corresponding author: christian.paglia@supsi.ch

Abstract

Drinking water reservoirs are often made of cementitious materials. The inorganic mineral phases exhibit a similar chemical composition as the natural rocks. This enables the concrete in contact with drinking water to be a safe material with respect to the human health. The carbonate or the free-CO² content of the water control the extent of the concrete deterioration. To increase the durability, cement-based mortars are applied as a coating. In this work, the damage on site and in laboratory, such as bubbles, cracks and microcracks formation, leaching effects and detachments of three cement-based coatings were investigated. The coating systems exhibited conventional mechanical parameters, such as the compressive and flexural strength, but a different behavior with respect to the cracks formation. This fact was dependent from the coating thickness, application features, water content, superplasticizer dosage, environment parameters and mortar quality. The damage was less related to the mechanical properties, in particular the compression strength. The coatings generally exhibited a dense compact microstructure. The addition of superplasticizers promoted the segregation of the aggregates. The fine particles were concentrated along the surface layers, which in turn, were more susceptible to the environmental changes. The coatings adhesion strength was always above 2 N/mm² for the coatings tested in laboratory. A reliable and acceptable adhesion that increased the durability.