{"id":14111,"date":"2026-11-06T07:54:20","date_gmt":"2026-11-06T05:54:20","guid":{"rendered":"https:\/\/www.traveter.ee\/?p=14111"},"modified":"2026-11-06T07:54:20","modified_gmt":"2026-11-06T05:54:20","slug":"reconstruction-of-filters-f17-f19-ulemiste-water-treatment-plant","status":"publish","type":"post","link":"https:\/\/www.traveter.ee\/en\/reconstruction-of-filters-f17-f19-ulemiste-water-treatment-plant\/","title":{"rendered":"Reconstruction of filters F17\u2013F19 in Building A of \u00dclemiste Water Treatment Plant"},"content":{"rendered":"\t\t
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Reconstruction of filters F17\u2013F19 in Building A of \u00dclemiste Water Treatment Plant<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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As a subcontractor to Bauest O\u00dc, Traveter Grupp carried out concrete repair, shotcrete and waterproofing works on filters F17\u2013F19 in Building A of AS Tallinna Vesi’s \u00dclemiste Water Treatment Plant, as well as the renovation of the filter hall. The filters were built in 1927 in the historic Building A of the Tallinn Filter Waterworks, which is a listed heritage building, and are in direct contact with drinking water, so all materials used had to be certified for contact with drinking water.<\/p>\n

The original plan<\/strong><\/p>\n

Based on the information available at the time of the tender, the plan was to remove the ceramic tiles and filter media, clean the surfaces of the filter chambers with ultra-high-pressure water jetting down to the load-bearing reinforced concrete, repair and level the concrete surfaces with repair mortar, and coat the filter walls with MasterSeal M 808 \u2013 an elastic, easy-to-clean waterproofing membrane designed for drinking water tanks.<\/p>\n

The challenge revealed during the works<\/strong><\/p>\n

After ultra-high-pressure jetting of the walls of filters F17 and F18, it became clear that the concrete was in much worse condition than expected. When the filters were built in 1927, uncrushed natural gravel was used as concrete aggregate instead of crushed stone. Its rounded particles bond to the cement matrix considerably more weakly than crushed stone. The concrete was particularly weak from the bottom of the filter up to a height of 2 metres, where the filter media had previously been.<\/p>\n

We carried out pull-off tests at eight test locations in each filter. The average bond strength was 1.16 and 0.83 N\/mm\u00b2 respectively, and a large share of the individual results were below 1.0 N\/mm\u00b2. The waterproofing manufacturer requires a substrate tensile strength of at least 1.0 N\/mm\u00b2, and the concrete repair standard EN 1504 requires at least 1.5 N\/mm\u00b2. In addition, no individual result may be below 1.0 N\/mm\u00b2. It was therefore not possible to continue with the original solution.<\/p>\n

The solution<\/strong><\/p>\n

As the required bond strength could not be achieved, the technology had to be changed. Further removal of the weak concrete by hydrodemolition would have had an unpredictable duration and outcome, so we proposed to the Client a solution in which a layer of shotcrete is added to the existing walls and anchored to the substrate with reinforcement mesh.<\/p>\n

The final scope of works included:<\/p>\n