Potable water tank in Lozenets
Sofia - Bulgaria
The 90-year-old potable water storage tank in Sofia boasts an 18,500 m³ capacity and a turbulent past. Its chambers defied the bombings of the Second World War and survived numerous earthquakes in the region unscathed. But now the sands of time had taken their toll, with the structure so dilapidated that a thorough rehabil-itation campaign was imperative for its survival. MC had already cooperated successfully in the past on the Rila Water Supply Pipelines Project with Sofiiska Voda, the local supplier and operator of the facility, and had been invited back in 2015 for an inspection of the potable water tank together with another specialist supplier.
Cracks and spalling
The masonry of the structure revealed numerous cracks, some of which had already developed leaks and were water-bearing. There were also fractured and spalled areas and exposed reinforcement, especially in the ceiling area.
Discounting a repair system based on waterproof PE panels suggested by the competitor bidder, the project planning company TIA Engineering and representatives of Sofiiska Voda opted for MC 's solution proposals instead. Decisive factors included the prevailing application conditions of only 6 – 8° C due to the high humidity and low ambient temperatures prevailing, and the fact that the installation of rigid PE panels in the caverns with their many columns and different wall and ceiling shapes presented a huge challenge.
In June 2016, the chosen applicator Opel Neshev started work on the rehab project. The cracks were repaired using MC-Injekt GL-95 TX, a low-viscosity, soft and flexible sealing injection resin offering easy application at low temperatures. This meets the requirements issued by the UBA (German Environmental Agency) for repair systems in contact with potable water and is best suited for sealing joints, cracks, cavities in masonry and concrete with permanent water contact.
For the further repair of the ceilings and walls of the chambers, the project team opted for the MC-RIM PW 20 concrete replacement system and MC-RIM PW 10 special protective coating, which have proven effectiveness in providing enduring protection in the potable water sector. The cement-bonded concrete replacement system was used to level the wall and ceiling surfaces and increase the concrete coverage. This was followed by a finish with the mineral surface protection coating MC-RIM PW 10. Highly sulphate-resistant and chloride-proof as well as carbonation-inhibiting, this product is impermeable to water yet open to vapour diffusion. Both chambers were thus successively and successfully repaired to the absolute satisfaction of the customer within a period of just three months.