The future of concrete

Kenneth Frampton (GSAPP, Columbia), Pascal Casanova (R&D Director, Lafarge), Jacques Resplendino (engineer, French Transport Ministry), Benjamin A. Graybeal (engineer, Federal Highway Administration), Antoine Naaman (Civil engineering, University of Michigan), Surendra Shah (Civil engineering, Northwestern University), Laurie Hawkinson (GSAPP, Columbia), Jacques Ferrier (architect), Jacques Lukasik (Scientific Affairs SVP, Lafarge), Christian Meyer (Civil engineering, Columbia), Paulo Monteiro (Civil engineering, Berkeley).

Invented by the Romans and forgotten for nearly 1500 years, concrete was rediscovered in the 19th century and became so popular that it is now the most used construction material in the world. The second most consumed product in the world after water, every inhabitant of the planet consumes 1.5m³ of concrete each year!

Concrete's renaissance owes much to France's Joseph-Louis Lambot who was the first to submit a patent for "ferro-cement". This original reinforced concrete was used in various applications: boats, apartment blocks, works of art, etc.
Up until the 1960s, concrete reinforced with a steel grid was the prevailing model. Then concrete reinforcement technologies developed with, for example, the addition of metal or natural fibers, three-dimensional steel reinforcement, the introduction of microfine cements, etc.

Nowadays, reinforced concrete is in a period of transformation; methods and techniques for reinforcing are developing, as is the plasticity and nature of additives. Innovations are making it possible to carry out closely spaced pourings and therefore create new continuous surfaces and more elastic shapes.

A real technological break-through occurred in the 1980s with the emergence of ultra-high performance fiber-reinforced concrete. A genuinely high-tech product, "UHPFRC" developed as a result of:

• The pooling of multidisciplinary scientific knowledge: chemistry, rheology, physics, mechanics of construction materials, micromechanics, etc.
• The use of digital observation and modeling tools: nuclear magnetic resonance, electron microscopy, nanoindentation, atomic force microscopy, etc. These new instruments make it possible to expand our in-depth knowledge of concrete down to the nanoscale.

Ultra-high performance fiber-reinforced concrete combines three main revolutionary properties:

• Resistance and ductility, enabling concrete to absorb deformations without breaking and be used in construction of expressway bridges.
• Self-compaction, making it possible to produce works of art in the most unusual shapes.
• Durability, which allows concrete to be used in aggressive or dangerous contexts (porosity to sea water, permeability to oxygen, etc.), in nuclear power plants for example.

An ultra-thin footbridge in Seoul, Korea, helical stairs in Great Britain, thin colonnades at the Reina Sofía Museum in Spain, expressway bridges in the United States... all these international accomplishments demonstrate the many possible uses for Ductal®, Lafarge's ultra-high performance concrete.

As the most used construction material in the world, the concrete and its industry must be able to respond to the challenges of global warming and questions of sustainable construction, both through the material itself and its manufacture, but also by contributing to the performances of construction systems.

Concrete is currently the ideal material to respond to these sorts of challenges, and it can do so on several levels:

• Economic and social level: concrete is the only material able to respond to current demographic growth (+ 150,000 inhabitants/day globally). It represents 10% of the world's GDP and 28% of the total global payroll.
• Standard of living and safety: fire-resistant, earthquake-proof and with acoustic and thermal insulation properties... all advantages for a sustainable material with a low maintenance cost.
• Environment and natural resources: produced locally, concrete is transported over short distances and has a very favorable carbon and energy footprint.

To meet sustainable construction and climate change challenges, several actions are possible:

• using alternative energy sources (old tires, coffee pods, wind farms, etc.),
• optimizing the composition of concrete and the use of alternative material that partially replace cement and natural raw materials (fly ashes, slags, etc.),
• perfecting processes in the plants,
• recycling water and concrete, etc.