High early strength concrete for tall builds in London

Southwark, London



Dunne Group


Brookfield Multiplex

Location type

City Centre



The challenge

No.1 Blackfriars is a mixed use, 50 storey development. It comprises of residential apartments, commercial, entertainment and retail space. Tarmac completed 30 storeys by June 2016. Following successful completion of the four storey basement where approximately 25,000m3 of TOPFLOW was supplied, Tarmac were asked to supply 1,000m3 of TOPROC HS to support the core of the building. From the perspective of concrete, this meant we previously needed to deliver a compressive strength of up to 60MPa. However, the demands of tall building construction today are such that structures need significantly higher compressive strengths, as high as 90MPa, so that we can meet developers’ demands.

Our solution

Tarmac committed to the project by installing a new microsilica dispensing system at their Kings Cross plant. This new system was installed to specifically supply One Blackfriars. Tarmac worked closely with the client at the development stage of testing the concrete to ensure that the designed strength was reached. TOPROC HS gains strength in hours not days and on average will gain 25N strength in 24-48 hrs.

Results and benefits

A typical TOPROC concrete, when tested, demonstrated that it was capable of increasing the impact until first crack by up to 30 times when compared to a typical RC32/40N concrete. Tarmac have had a steady relationship with Dunne Group since 2013 and have also supplied Brookfield Multiplex on various sites throughout London. After all the hard work that has gone into this project, Tarmac have excelled their reputation as a supplier. The supply to date has reached the specified strengths and all parties involved are happy with the result. Tarmac continued to supply until project completion in 2017.

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Additional info

Performance concrete

The properties of Toproc concrete make it ideal for use in high rise buildings.

Faster curing 

Toproc offers faster curing and extreme toughness. Toproc gains strength in hours, not days and on average will gain 25N strength in 24-48 hours compared to a C40N concrete, which typically gains 40N stregnth in 28 days. The average strength of Toproc is 60N+/28 days.

Whole life project savings 

Toproc is proven to outlast conventional concretes in environments subjected to high impact and abrasion resulting in reduced whole life costs. 

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TOPROC HS case studies