Protection for Steel Reinforcement - Wacker Chemie AG


Protection for Steel Reinforcement

Built by Kajima, the Toyota Arrows bridge on the Shin-Tomei Expressway between Tokyo and Nagoya was hydrophobically impregnated with silanes in 2004.

Pressure and Dosage Decisive

Liquid products, on the other hand, are applied by “flooding.” This means that the product is applied to the wall under very low pressure. It runs down the wall, soaking into it as it goes. For liquid products, several work steps (two to three) are often required in order to apply sufficient material.

Prior to the actual application via the airless technique, WACKER building-protection expert Auer recommends carrying out spray tests to find the right application pressure for the relevant product, environmental and substrate conditions. Too much pressure would cause the product to atomize and lead to wastage, while too little pressure would result in uneven application – lumps form on the surface.

Beside material dosage and active-ingredient concentration in the water repellent, there are a number of other factors that determine the silanes’ penetration depth, including weather conditions and the porosity and moisture content of the concrete to be treated. If the moisture content is greater than four percent, for example, treatment must not proceed – according to the German technical contractual conditions and guidelines for civil engineering structures – as the silanes cannot penetrate sufficiently. Further problems can arise if the building-component temperature is too low – below five degrees Celsius. At such low temperatures, there is a risk of water condensation on the component, preventing the effective penetration of the water repellent.

For quality control purposes, in Germany, reference surfaces must be prepared prior to the actual application to test how the hydrophobic impregnation works on the concrete to be treated. Among other things, this test area is used to determine the amount of water-repellent agent needed. Normally, two or three test surfaces with different dosage are prepared; exactly 28 days later, service engineers determine the quality of the water-repellent treatment. Only then do they decide what dosage to apply to the concrete structure.

Best Protection even under Extreme Conditions

Although the application conditions vary greatly with location and climate, hydrophobic impregnation with silanes is in demand around the world. “In Japan alone, 125 million square meters of concrete surfaces have been treated since the market launch,” says Wacker Asahikasei manager Kanzawa. Especially in the case of calls for bids for expensive infrastructure projects, contracting authorities increasingly demand that the results should be durable – renovation cycles that are too short could ruin a bidder’s chances. The operator didn’t give the construction of the new highway beside the Tomei Expressway the motto “100-year road” without good reason.

Whether roads and highway bridges in Japan, harbor piers in Dubai, tunnels in Europe or dams in China – WACKER’s silane treatment protects structures even under extreme loads. All around the world.