In last few years, the expression ‘High Performance Concrete’ and the acronym HPC have become very fashionable. But what exactly is meant by this? Is high performance concrete a material really different from just concrete? Or is it a concrete that is appropriate for a particular situation?

It sounds like advertising a new product but, in most respects, high performance concrete is not fundamentally different from the concrete that we have been using in all along, because, it does not contain any new ingredients and does not involve new practices on site. In the 1970s, when the compressive strength of concrete used in the columns of some high-rise buildings was higher than that of the usual concretes used in construction, there is no doubt that it was legitimate to call these new concretes ‘high-strength’ concretes. They were used only because their strength was higher than that of usual concretes generally specified at that time.
Actually, high performance concrete evolved gradually over the last 15 years or so, mainly by the production of concrete with higher and higher strengths: 80, 90, 100, 120 MPa, and sometimes even higher.

However, when the superplastizer began to be used to decrease the water/cement or water/binder ratios rather than being exclusively used as fluidifiers for usual concretes, it was found that concretes with a very low water/cement or water/binder ratios also had other improved characteristics, such as higher flowability, higher elastic modulus, higher flexural strength, lower permeability, improved abrasion resistance and better durability. Finding aggregate that meet the minimum standard requirements for usual concrete in the 20 to 40 MPa range is fairly easy; however, when targeting 75 MPa, a number of problems arise. Performance can be limited by certain aggregates, such as gravels that are too smooth and not clean enough, those containing too many soft and crumbly particles, soft limestones and hard aggregates with poor shape characterised by flat or elongated particles. Aiming for a design compressive strength of 100 MPa imposes even greater restrictions on selecting aggregates, cements and superplastizers. Successfully producing a 100 MPa concrete requires:
A very strong, clean, cubical coarse aggregate (with some exceptions for some glacial gravels)
A cement that performs outstandingly well, both rheologocally and in terms of strength
A superplastizer that is totally compatible with the selected cement

Example projects that make use of HPC:
Water Tower Place (1970), Chicago, Illinois, USA (60 MPa)
Norway’s Gulfaks offshore platform (1981) (70 MPa)
Hassan II mosque (1986), Casablanca, Morocco (95 MPa)
Sylans and Glacieres viaduct (1986), France (60 MPa)
Scotia Plaza (1988),Toronto, Canada (70 MPa)
Two Union Square (1988), Seattle, Washington, USA (90 MPa)
Joigny bridge (1989), France (60 MPa)
The ‘Pont de Normandie’ bridge (1993), France (60 MPa)
Hibernia offshore platform (1996), Newfoundland, Canada (70 MPa)