Deansgate Square, Manchester

Once completed in Spring 2020, Deansgate Square will consist of four glazed towers – the tallest of which will be 64 storeys high and the tallest building in the UK outside London – providing more than 1,500 luxury apartments and leisure facilities.

Concrete supplier, Hanson, has designed and delivered a range of different concretes to overcome the engineering challenges of the project. These include high performance concretes providing strength in excess of 100N/mm² in the lower columns; watertight derivates in the basement and bespoke designs containing 70 per cent GGBS in the foundations and raft bases.

All of the concretes were also designed to be able to be pumped more than 300 linear metres across the site and, for the walls, up to 204 metres vertically.

GGBS (ground granulated blastfurnace slag) is a cement replacement product which enhances the durability of the concrete while adding to its sustainability credentials. It is a by-product and using it to replace one tonne of Portland cement reduces the embodied CO₂ of the concrete by around 850kg.

The percentage of GGBS used in the concrete mixes varied from 40 per cent in the main structural elements to 70 per cent in the foundations and raft bases, where its use also helped minimise the production of heat, reducing the risk of thermal cracking.