Potable water tank in Oberwart repaired

The potable water tank serving the town of Oberwart had developed signs of damage to the ceiling, walls and floor. In planning the repair measures, the operator decided to use the MC-RIM system as a particularly sustainable means of protecting the structure.

Spalling at the rebar had occurred and distinct areas of brown discoloration had appeared on the floor, walls and ceiling inside Oberwart’s 2,500 m3 potable water tank, which was built in 1970. The impermeability of the mortar layer in the affected areas had gradually decreased over the years of service. A problem for the upcoming rehabilitation arose from the fact that the interior had been patched with abrasion-resistant plaster a few years ago due to similar damage.

 

Together with the specialist construction company MM Kanal-Rohr-Sanierung GmbH from Hartl in Austria, the regional water authority (Wasserverband Südliches Burgenland) developed a sustainable rehabilitation concept for the elevated tank. This involved removing the old coating by means of high-pressure jetting (HPJ). Wall and ceiling surfaces were to be levelled and the concrete cover increased before the final new coating could be applied. Only materials that are demonstrably suitable for potable (drinking) water were to be used.

MC-RIM PW at work

Both parties had already had a number of positive experiences with the MC-RIM PW surface protection system developed by MC for potable water tanks, a system with a proven record for efficacy and durable protection going back many years. The rehabilitation work in Oberwart was scheduled for the period from January through April 2019. The inner surfaces of the tank were first completely levelled with the cement-bound speciality concrete replacement MC-RIM PW 201. It can be applied by hand and sprayed and can be used on both structural and non-structural concrete components, walls, floors and ceiling surfaces in potable water tanks. MC-RIM PW 201 is certified as an M3 mortar – the highest grade – according to Germany’s DAfStb repair directive for steel-reinforced concrete structures.

 

The specified increase in internal concrete coverage was thus readily achieved. This was followed in the ceiling and wall areas by a finish with the mineral surface protection compound MC-RIM PW 101, a water-impermeable material offering high sulphate and chloride resistance and carbonation-retarding properties as well as being open to water vapour diffusion. Exhibiting identical properties but optimised for use on horizontal surfaces in the potable water sector, MC-RIM PW 301 was used as the surface protection solution for the floor.

 

Far below specified max limits

The all-mineral MC-RIM PW system fully met the ÖVGW (Austrian Association for Gas and Water) requirements as per Codes of Practice W 347 and W 300 of its German counterpart DVGW (ÖVGW test reference W1.547). The coatings exhibit values well under the prescribed water-cement limit for lining mortars of (w/c)eq ≤ 0.50. And with fresh mortar air void contents far below the required 5% by volume, MC-RIM PW 101 and 301 offer excellent waterproofing properties.  In all, the surface area coated with MC-RIM PW was 2,800 m2. Both chambers were successfully repaired one after the other over a period of three months, with the client more than satisfied with the sustainability, durability and long service life provided by this state-of-the-art solution.