Pantheon, Rome

17 March 2011 – Favourites:  The  world’s most important materials have an intriguing history of genius, commercial know-how and colourful characters, reports Caroline Noller in this first of a two part series. Part one of this story focuses on bricks, cement and concrete; the second will be on the amazing story of aluminium, steel and glass.

Just six materials account for the vast majority of the carbon footprint of our buildings today, and their origins and application were the responsibility of a handful of men and a few precipitous moments in history.

The evolution of cement, steel, brick, glass, aluminium and plastics is entwined with fascinating stories of ingenuity, greed, passion and control, punctuated with decade-long patent wars, famous anti-trust actions and threats of death.

Today, their production methods remain largely unchanged from their Industrial Revolution roots, and are likely to remain so in the absence of massive external forces.

Environmentalists portray these materials and their controlling multinational corporations as epitomising the evil of globalisation with disregard for the communities from which they extract resources, the impact of their products’ profligate use, and visceral urban sprawl.

But what are the facts? Is there validity to the demonisation of the decisions that have led to these materials dominating our building and consumer tastes?

Are we looking at these materials in the right light? Is it possible to use them in a productive manner, and if so, what are the constraints to achieving their sustainable potential?

A trip back in time
This series journeys into history to investigate the stories behind these materials, the economics of their exploitation and their environmental impacts.

These six materials have appeared with mankind’s major breakthroughs in harnessing fuel and power for mechanical means.

The harnessing of fire and the agricultural revolution, with its development of organised society, saw the breakthroughs of fired-clay bricks and cement, with its complex daughter, concrete.

The discovery of coal and its application to mechanical production defines the major industrial era breakthroughs of steel and flat, clear, window glass.

The age of oil and electricity heralds the entry of the most modern of building materials, aluminium and plastics, which accelerated building and consumption, and the associated impact on the atmosphere and environment.

The coming together of the industrial revolution, with its energy multiplier, and the creation of the modern corporation, enabled the monopolisation of the natural resource inputs into these materials and, consequently, the control of their markets.

Energy efficiency
The maintenance of market price differentials and the use of cartels for price fixing were the major mechanisms by which companies secured dominating market share in the early 1900s .

Without doubt, this condition has delivered enormous social benefits. However, it has allowed a systemic lack of energy efficiency investment or improvement, with the International Energy Agency recently estimating that the underlying industrial processes are at least 50 per cent higher than their theoretical potential .

If the embodied carbon externalities were internalised at A$40 per tonne, the inflation cost impact on buildings would be between five and eight per cent. At A$150 per tonne, the level the IEA suggests as economic for breakthrough improvements, the impact on building would be so great as to stop it in its tracks.

Historically these building materials first appear with kiln-fired clay bricks and pozzolanic cement in ancient Rome around 50 BC (although sun-dried bricks date back to 4000 BC). Also in Rome, sand-cast glass for windows and floor mosaics appeared around 100 AD.

Steel has been known since the Iron Age but not comprehensively as a building material until in England in 1709 AD.

Aluminium is described by Pliny the Elder in Rome but does not appear as a building material until late 1800 AD, and finally, plastics from 1900 AD.

Today these materials account for 18 per cent of annual global carbon dioxide emissions.

v

Two men rate a special mention for their influence on four of our six materials: Marcus Vitruvius Pollio (80-70 BC to approx c15 BC), described by historians as the world’s first architect, engineer and master-builder, is responsible for our use of fired-clay bricks as well as cement and concrete. Paul LT Heroult (1863 to 1914) gave us the process for “reducing or smelting” aluminium, as well as the electric arc furnace for energy efficient steel production.

Here we look at the history of five of the six materials: bricks, cement and concrete, aluminium, steel and glass.

Bricks

By mass, there are more bricks made than any other building material in the world today[3]. Vitruvius elevated the brick to its higher and more durable form in his description of the use of kilns in brick making and their subsequent properties and limits when applied to construction such as aqueducts and large public buildings[4].

Early uses
Although not designed by him, The Baths of Caracalla, Rome (216AD, with a reported 18 million bricks) and the aqueducts of the Pont du Gard, France (19 BC) and Segovia, Spain, are outstanding examples that still exist today of the contribution of his technological advancements.

Environmental credentials
The roots of the fired brick align closely with the sustainability mantra of local and durable qualities. However, it is let down by its need to be integrated into walls with cement and, owing to its mass, the extent of reinforced concrete support structure.

Bricks are third in terms of annual contribution to global carbon dioxide emissions and yet considered alone, each brick has a small carbon footprint. However, when bound into a 90 mm wall its carbon footprint doubles owing to the cement mortar. It doubles again if rendered, excluding the incremental structure .

China and India account for 65 per cent of global production and consumption of clay bricks and less than 10 per cent of kilns in use are modern, energy and pollution-efficient .

Cement

In his masterpiece De Architectura, Vitruvius says: “There is also a kind of powder from which natural causes produce astonishing results. This substance, when mixed with lime and rubble, not only lends strength to buildings of other kinds, but even when piers are constructed of it in the sea, they set hard under water .”

Early uses
The Pantheon, Rome (126 AD), is one of the world’s most loved and best preserved ancient Roman buildings, and is a classical example of the genius of Vitruvian pozzolanic cement and concrete. Still the world’s largest un-reinforced concrete dome, its exceptionally long life, local, lightweight concrete design, and light-admitting oculus, and floors shaped to capture and re-use rainwater that falls within, makes it the quintessential “green” building.
Environmental credentials

The ingenious use of volcanic pumice and ash in place of traditional heavy crushed rock aggregates and the coffering of the ceiling are the means by which the structure achieves it light, self- supporting state across such an incredible span.

Concrete

Notwithstanding the documentation of his methods, the genius of Vitruvian cement was lost and remained largely undeveloped until Joseph Aspdin discovered and patented Portland cement in 1824.

However, it was not until 1867 that frustrated French gardener Joseph Monier achieved the breakthrough of reinforced concrete when searching for a garden pot impervious to cracking. He showed the new patented invention at the Paris World Fair that same year.

Early uses
Having seen the Monier method, François Hennébique, a French engineer, applied the idea to buildings and patented the first integrated concrete and steel building construction method in 1892. In 1897, his invention enabled the construction of the Weaver’s Flour Mill (Swansea, Wales), Europe’s first multi-storey, reinforced concrete building. This set the stage for the rapid development of the skyscraper.

Environmental credentials
Most of concrete’s environmental impact arises from the energy intensity of the cement that requires the “sintering”, or burning, of limestone at 1450 degrees Celsius in a kiln, to achieve its desirable hydraulic properties (that is, it not only hardens by reacting with water but also forms a water-resistant product).

Accounting for five per cent of global carbon emissions in all its applications, it is ironic to witness the modern move to increase the use of fly ash (a waste product from power stations) as a cement replacement in concrete that harks back to the original Vitruvian formula.

  1. World Aluminium Industry, Australian Mineral Economics, 1980
  2. Tracking Industrial Energy Efficiency and CO2 Emissions, IEA, 2007
  3. Assuming produced via clean and efficient cement and brick kiln technology. If produced using inefficient means this figure could be 5 to 10 times higher.
  4. Baum, Black Carbon from Brick Kilns, OECD Clean Air Task Force, April 2010
  5. Vitruvius, De Architectura Book 2, Ch 5, section 1, 25 or 40 BC (est)