The RBC Gateway tower in Minneapolis, Minnesota welcomed its first office tenants in February 2022, with the remaining office tenants and condo residents expected later this summer. The project engineers specified PENETRON ADMIX SB, a crystalline waterproofing admixture, for the tower’s below-grade concrete structures.
With a population of around 430,000, Minneapolis metropolitan area is the largest business center between Chicago and Seattle. The city features one of the country's most comprehensive park systems, thirteen lakes, wetlands, the Mississippi River, creeks, and waterfalls; many of which are connected by parkways within the Grand Rounds National Scenic Byway. As a result, the region has very high groundwater levels.
The RBC Gateway project, a 37-story tower redevelopment in downtown Minneapolis, was designed by Smallwood, Reynolds, Stewart, Stewart & Associates, an international architectural firm. The tower is one of downtown’s tallest buildings and is located at the north end of Nicollet Mall and is connected via skyway to the Minneapolis Central Library, extending the city’s unique system of enclosed pedestrian bridges.
The RBC Gateway complex has over 1.2 million ft2 of floor space, with 531,000 ft2 of office space, an 8-floor, 222-room Four Seasons Hotel – Minneapolis’s first 5-star luxury hotel – a café, a restaurant, 34 residential condos, underground parking (428 spaces), a bike garage, and an outdoor public plaza with green space.
Surrounded by Groundwater
“Due to the high groundwater levels of the area, the project engineers required a reliable system to protect the below-grade concrete structures – including the multi-floor parking garage and basement areas – from the high hydrostatic pressure,” explains Christopher Chen, Director of The Penetron Group. “Our local Penetron team worked with Cemstone Products, the ready-mix concrete supplier, to ensure a durable and waterproof mix design.”
PENETRON ADMIX SB – in soluble bags – was added to the concrete mix during the batching phase. The pre-measured bags dissolve quickly and completely for accurate (and easy) dosage for any project. This helps save time and costs in addition to enhancing the durability of the finished concrete.
Reducing Permeability is Key
The PENETRON ADMIX SB-treated concrete for the RBC Gateway project was used for the below-grade retaining walls and the tower’s foundation slab.
“While an optimal W/C ratio is key in achieving the desired overall concrete performance, reducing permeability is the most crucial aspect of concrete durability,” adds Christopher Chen. “PENETRON ADMIX reduces shrinkage cracking and self-heals hairline cracks over the service life of the structure. This virtually eliminates any maintenance costs for waterproofing over the lifespan of the structure.”