Bridge repairs streamlined thanks to waterproofing with polyurea

In the renovation of the Kaarepere bridge, the bridge was waterproofed with a sprayable Teknos polyurea coating system. The highly waterproof, elastic and resistant polyurea forms a seamless waterproofing film that adheres firmly to the surface of the bridge's concrete deck and lasts well in Estonia’s extreme temperature fluctuations. The bridge was kept open to traffic while under renovation and waterproofing was renewed within less than a week.

Damaged pavement of a heavily trafficked bridge in need of renovation

The Kaarepere bridge is located in Estonia, where temperatures can rise above +30 °C in summer and drop below -20 °C in winter. The Kaarepere bridge was constructed in 2011 and is heavily trafficked, especially by HGVs. Therefore, the bridge pavement is stressed by varying weather conditions as well as constant loading. There was extensive damage to the bridge pavement, such as dents, humps and cracks.

Bituminous film materials, which are traditionally used as waterproofing materials and applied to concrete, act like an adhesive and adhere firmly to the substrate during the installation phase when heated by fire. However, heat also exposes the surface to changes. In addition, the surface of the concrete is never perfectly smooth. When two materials glued together are stressed, air pockets may be left between the film and the concrete.

In the hot summer heat of Estonia, the temperature of the black asphalt road can rise up to +70 °C, and even the smallest air bubble between the waterproofing material and the concrete collects heat, which in turn increases the air pressure in the bubble. As a result of the air pressure, a hump rises to the road surface and the asphalt breaks. Much of the damage to the road surface of the Kaarepere bridge was due to this phenomenon.

Broken asphalt is a danger to traffic, and it also exposes the concrete bridge structure to erosion. In general, bridges can be in very poor condition as early as 3 to 4 years after completion. Repairing poor road surfaces and bridges takes time, and long road repairs interrupt and slow down traffic for months.

The time required for repair work was significantly reduced with polyurea as waterproofing speeded up the work

The damage to the bridge was repaired during the renovation in the summer of 2020 and waterproofed with the TEKNOPUR polyurea coating system. Teknos' SILKO-approved coating system guarantees that waterproofing with polyurea complies with the Nordic quality standards of the bridge repair regulations.  

Polyurea is a highly waterproof coating that forms a seamless film. The sprayable polyurea fills the cracks in the surface and bridges them as a highly flexible coating. Polyurea adheres tightly to concrete according to its surface shape and performed very well in the adhesion tensile test performed at the design stage.

The whole renovation was completed one week faster than with the more conventional method, as the entire coating process of the bridge could be shortened from 10-14 days to 6 days, which is the fastest possible time to renew the waterproofing on a large bridge deck like this. The waterproofing work with polyurea spraying went quickly — polyurea cures in seconds and the bridge deck can be covered with asphalt soon after the adhesion treatment. Polyurea is a highly elastic and durable coating whose reliability is not affected by the heat of the asphalt.

Waterproofing with polyurea allows traffic to continue throughout the renovation work

There were no disruptions to traffic in Kaarepere during the renovation of the bridge, because in the waterproofing phase before the asphalt work, the polyurea was first sprayed onto one section of the strip, after which the traffic could immediately resume in this already waterproofed strip. The cured polyurea film withstands heavy traffic well.

As traffic resumed in the already waterproofed lane, renovation work continued in the second lane until the lane with its waterproofing and asphalt was completed, and traffic was again transferred to the fully finished lane. The final phase of the renovation consisted of completing asphalt work in the second lane.

In Estonia, 11 bridges have already been waterproofed with Teknos polyurea. In the waterproofing of bridges, the use of polyurea elastomer is an innovative method and is rapidly becoming more widespread.