In north-west Vietnam, Mong Sen Viaduct overlooks the rice terraces of the beautifully situated town Sa Pa. At 83 meters, the viaduct is Vietnam’s highest bridge. It lies at the foot of Fansipan, the Indochina peninsula’s highest mountain.

Mong Sen Viaduct, Vietnam
Image: Mong Sen Viaduct, Vietnam’s highest bridge

This new construction, which is more than 600 meters long, was completed at the end of 2022 and shortens the journey between the provincial capital of Lao Cai town and Sa Pa. It not only delivers time savings, but provides a much safer alternative too, given that the winding road is regularly hit by landslides. “The viaduct makes this journey quicker and less stressful,” says Jacobo Perez Polaino, General Manager of Sika Vietnam. For him, the viaduct is a sustainable project that supports the country’s development. “It’s a real feather in Sika’s cap, and one that we’re proud of.”

High-Performance Concrete To Meet the Highest Demands

Due to its remoteness, the Mong Sen Viaduct could not be built with prefabricated concrete elements. Instead, it was constructed by the casting of concrete in situ. Sika was able to support general contractor Thang Long Meco by providing not just concrete admixtures and mortar products, but also technical advice throughout the successful construction of this balanced cantilever bridge structure. The products used were the superplasticizers SikaPlast®-398 SF and Sika® ViscoCrete®-3000-20 M for the concrete, along with the powder admixture Sika® Intraplast® Z-HV and grouting mortar SikaGrout®-214-11 for the backfilling of the prestressing cables duct. These high-performance products met the construction site requirements for the flow properties, reducing maximum water content, optimizing mechanical properties and therefore durability of the final concrete.

Construction of the viaduct took place not only during the day, but also at night. Therefore, the project team faced significant temperature swings. “This was quite a challenge, as the concrete had to exhibit the same properties at all times when it was pumped up for casting following long transport journeys,” explains Pham Huy Cuong, who headed the project team as North Area Manager of Sika Vietnam. Thanks to Sika’s admixtures, the required properties were consistently met. The additives ensured that the concrete cured completely to meet the high compressive strength required. This high-strength concrete allowed the project team to install sections of the horizontal bridge segment by segment, which was essential because the viaduct is exposed to extreme stress.

"Thanks to our technical expertise, we were able to provide the client with detailed advice on the perfect mix design of the concrete." Pham Huy Cuong, North Area Manager for Sika Vietnam
Pham Huy Cuong, North Area Manager for Sika Vietnam
Image: Pham Huy Cuong, North Area Manager for Sika Vietnam