October 2, 2010

FEATURE | Concrete & Masonry

Column: From the Romans to the Jetsons, concrete is versatile

CAROLYN CAMPBELL

BC Ready-Mixed Concrete Association

As long ago as the Greek and Roman empires, concrete helped shape the built environment.

Today, this natural construction material is still made in essentially the same way, by mixing sand, water, cement and aggregate.

While at a basic level the composition of concrete has remained largely unchanged, research and development of concrete technology continues to hoist our understanding of what can be done with this “liquid stone” .

Advancements in concrete are clearly linked to the discovery of smaller and smaller material scales.

In the mid-1980s, scientists broke through the submillimeter scale (one thousandth of one meter), which led to high performance concretes with higher strengths (> 40 MPa) and increased durability. The construction market harnessed the economies resulting from accelerated schedules, longer spans and reduced column sizes.

In the mid 1990s, science cracked the submicrometer scale (one millionth of one meter) and gained a better understanding of calcium silicate hydrates, which make up 80 to 90 percent of cement binding paste.

This gave rise to ultra high performance (UHP) concretes, with yet again improved durability and strengths like mild steel.

The design community responded with concrete structures that are taller, more slender and elegant, and more durable using UHP mixes.

Around that same time, self-consolidating concrete (SCC) emerged as another breakthrough in the production process of concrete.

Ideal for achieving unblemished surface finishes and flowing through rebar congestion, SCC has helped eliminate the need for large placing crews and noisy machinery.

Contractors using SCC need fewer finishers and construction sites are quieter and safer.

Today, research is developing scientific breakthroughs at the atomic scale.

Two emerging areas of research deal with cement and admixtures.

Understanding of the hydration of cement particles and their interaction with chemical admixtures, combined with the use of nano-sized particles (one billionth of a meter) help to design modifications so that performance requirements can be met using less material.

Also, the chemical reactions that take place can be manipulated for maximum environmental and economic benefit.

While nanotechnology sounds like the science of the future, dozens of nanomaterials are currently available in the architectural marketplace.

You may be familiar with the de-polluting or “smog eating” concrete used in Richard Meier’s Jubilee Church, which used titanium dioxide nanoparticles to make this marvel possible.

Using light and air, photocatalytic concrete breaks down organic and inorganic substances responsible for air pollution.

However, you don’t need to be a nanotechnologist to take advantage of the many sustainable benefits that concrete offers.

Innovative designers are harnessing the thermal efficiency in concrete to help achieve zero net energy targets in construction, while taking advantage of concrete’s acoustic performance and fire resistance to build quieter and safer high-density neighbourhoods.

Concrete’s durability is enabling structures to be designed with increasingly longer service lives and the ability to repurpose architecture to save the impact of new construction.

Property owners are using pervious concrete to develop a larger area of available property at a lower cost, by eliminating the need for retention ponds, swales, and other stormwater management devices, while recharging the groundwater in situ.

The concrete and cement industries continue to seek ways to minimize our ecological footprints and enhance the sustainable nature of concrete.

Last year, the Ready Mixed Concrete Research & Education Foundation and Portland Cement Association partnered with the Massachusetts Institute of Technology (MIT) to establish the Concrete Sustainability Hub, a research center at MIT.

Each organization is committing $1 million a year for the next five years, with the goal of accelerating breakthroughs in concrete science and engineering and transferring that science into practice.

Two initial work plans focusing on the life cycle of concrete structures and the DNA of concrete, are well underway and MIT will release some of its early findings later this fall.

With the help of science, we will continue to further the understanding of concrete to lower both the monetary and ecological cost of construction materials.

The next wave of advancement in concrete will no doubt alter the built environment in ways almost unimaginable today.

I, for one, can’t wait to see what’s next.

Carolyn Campbell is the executive director for the BC Ready-Mixed Concrete Association (BCRMCA). Association members have more than 120 plants and 9,300 skilled workers in B.C.

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